US3881967A

US3881967A - High saturation cobalt-iron magnetic alloys and method of preparing same

Info

Publication number: US3881967A
Application number: US430114A
Authority: US
Inventors: Alexander W Cochardt; Administratrix By Hil Cochardt; Karl Foster
Original assignee: Westinghouse Electric Corp
Current assignee: ABB Inc USA
Priority date: 1972-02-22
Filing date: 1974-01-02
Publication date: 1975-05-06
Anticipated expiration: 1992-05-06

Abstract

An alloy is described which is suitable for use as a transformer core material. The alloy consists essentially of from about 4% to 6% cobalt, from 1% to 1.5% silicon, up to about 0.3% aluminum, up to about 0.8% chromium, less than 0.03% carbon and the balance essentially iron with incidental impurities. The method for preparing the alloy includes selected processing variables which will provide either a (110) or a (100) orientation in the alloys which have an open gamma loop which orientations are obtained during final heat treatment by the process of primary recrystallization and normal grain growth. There is also disclosed a process for producing in the same alloys having an open gamma loop an essentially (110) (001) type orientation employing a process in which the final microstructure is characterized as a secondary recrystallized microstructure.

Description

United States Patent [1 1 Cochardt, deceased et al.

[451 May6, 1975 [73] Assignee: Westinghouse Electric Corporation,

Pittsburgh, Pa.

[22] Filed: Jan. 2, 1974 [21] Appl. No.: 430,114

Related US. Application Data [63] Continuation-impart of Ser. No. 228,320, Feb. 22,

[52] US. Cl. 148/31.55; 75/123 K; 75/123 L; 148/100; 148/120; 148/121 [51] Int. Cl C04b 35/00 [58] Field of Search 148/31.55, 120, 121, 100, 148/110,l12,111;75/123 K, 123 L [56] References Cited UNITED STATES PATENTS 1,338,134 4/1920 Honda 75/123 K 1,678,001 7/1928 Brace.......... 75/123 K 2,112,084 3/1938 Frey et al 148/l20 2,442,219 5/1948 Stanley 75/123 K 3,164,496 1/1965 Hibbard et al 148/120 3,347,718 l0/l967 Carpenter et a1... 148/112 3,418,710 12/1968 Seidel et a1. 148/112 FOREIGN PATENTS OR APPLICATIONS 424,327 2/1938 United Kingdom 75/123 K Primary ExaminerWalter R. Satterfield Attorney, Agent, or FirmR. T. Randig [57] ABSTRACT An alloy is described which is suitable for use as a transformer core material. The alloy consists essentially of from about 4% to 6% cobalt, from 1% to 1.5% silicon, up to about 0.3% aluminum, up to about 0.8% chromium, less than 0.03% carbon and the balance essentially iron with incidental impurities.

The method for preparing the alloy includes selected processing variables which will provide either a (110) or a (100) orientation in the alloys which have an open gamma loop which orientations are obtained during final heat treatment by the process of primary recrystallization and normal grain growth. There is also disclosed a process for producing in the same alloys having an open gamma loop an essentially (110) [001] type orientation employing a process in which the final microstructure is characterized as a secondary recrystallized microstructure.

36 Claims, 4 Drawing Figures PATENTEURAY ems 3.881.967

sum 10F 2 ROLLING DIRECTION men CONTOUR FRACTION o l I 90 8O 6O 4O 2O 0 ALPHA FIG.IA

EITEIHEU 612112 3.881.967

Mitt! E01" k3 ROLLING DIRECTION |80 DIGlT CONTOUR z 60- g [.0 2.0 E 3 3.0 g 4 4.0 cc 5 5.0 e 6.0 20- 7 8.0 8 I00 9 I20 0 I r I 1 9o o so 40 20 o ALPHA HIGH SATURATION COBALT-IRON MAGNETIC ALLOYS AND METHOD OF PREPARING SAh/[E CROSS REFERENCE TO RELATED APPLICATIONS The present application is a continuation-in-part of Application Ser. No. 228,320 filed Feb. 22, 1972.

The subject matter of the present application is closely related to Application Ser. No. 228,071 filed Feb. 22, 1972 and Application Ser. No. 480,075 filed as a division of Application Ser. No. 228,071 on June 17, 1974; Application Ser. No. 228,319 filed Feb. 22, 1972; Application Ser. No. 228,318 filed Feb. 22, 1972 now abandoned in favor of Application Ser. No. 312,681 filed Dec. 11, 1972 allowed and Application Ser. No. 489,324 filed July 17, 1974 as a division of Application Ser. No. 228,070 filed Feb. 22, 1972 now abandoned in favor of continuing Application Ser. No. 401,766 filed Sept. 29, 1973.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to soft magnetic materials which are particularly useful in transformers as a transformer core material and may be processed in such a manner that either a cube-on-edge type orientation or a cube-on-face type orientation may be supplied in the final material thereby enabling the designer to take advantage of the preferred easy direction of magnetization when the materials are assembled in a transformer core. The cube-on-face material can also be used for cores of motors and generators and other dynamic electrical apparatus. In addition, either a primary recrystallized or a secondary recrystallized microstructure may be obtained thereby enabling the manufacturer to have a high degree of flexibility in manufacturing and supplying such material, and the electrical equipment manufacturer to utilize the best material for his applications.

2. Description of the Prior Art The operating induction of many of today's transformers is limited by the saturation value of the transformer core material. One of the most popular core materials in use today is one which contains nominally about 3% silicon in an iron base alloy and which is characterized by a high degree of (110) [001] type grain orientation. Such a steel however has a limited saturation value of about 20,300 gauss. If higher saturation steels can be obtained, smaller and ligher weight transformers can be built for a given rating at substantially reduced cost.

It is known that cobalt is the only element which significantly increases the saturation value of iron. However, the high cost of cobalt additions to iron precludes the economical use in transformers of materials containing between about 25 to 50% cobalt. This high cobalt class of iron base materials exhibits the highest saturation values known, namely, about 24,000 gauss.

The 3% silicon iron material in wide use in transformer cores today requires special processing to attain a desired orientation and this has both beneficial and detrimental effects.

Initially, it may be noted that the addition of 3% silicon to iron reduces the saturation value of pure iron from about 21,500 gauss to about 20,300 gauss thereby limiting the induction value at which the transformer may be operated. However, the reduction in the saturation value has been justified since the addition of up to 3% silicon and the processing thereof to obtain the req uisite degree of texture development results in substantially lower observed core loss values than with pure iron because the silicon addition improves the electrical resistivity, improves the purity and greatly aids in the development of the l 10) [001] texture. Consequently, an increase in the saturation value of the transformer steel to about 21,500 gauss would allow operating inductions above 19,000 gauss and would be quite valuable from the standpoint of reducing the size and weight of the transformer which could be built for a given rating.

In accordance with this invention two approaches have been made to this desired end and they result in one material having a saturation value equivalent to that of pure iron, namely about 21,500 gauss, a resistivity, p, of at least 30 microohm-centimeter and an open gamma loop, the material being characterized by the development therein of grain orientations characterized as either (1 10) or which orientations are obtained through a process of primary recrystallization. The other approach is an alloy meeting all of the above requirements and having a high degree of (1 l0) grain orientation but employing a secondary recrystallization process.

Pure iron undergoes a phase transformation from the room temperature alpha phase to the gamma phase at a temperature of 910C. This phase transformation destroys any recrystallization textures and makes the development of a preferred texture most difficult. A silicon addition of about 2% of iron is effective for closing the gamma loop and thereby prevents phase transformation from occurring when the material is heated to a temperature in excess of 900C. Accordingly, annealing of iron base alloys having 2% or more of silicon can be carried out at a temperature as high as l,200C for the development of the preferred orientation and purification of the alloy. The addition of cobalt to iron does not prevent the phase transformation but rather only raises the transformation temperature slightly. More over, it is also known that any element which tends to close the gamma loop also lowers the magnetic saturation value of pure iron.

Alloys with an open gamma loop undergo a phase transformation at the Ac, temperature of the alloy. Consequently, in processing that alloy it is imperative that any annealing heat treatment which takes place or any grain orientation must be done at a temperature below the Ac temperature of the alloy. Thus the alloy of the present invention when produced having a chemical composition in which the alloy may be characterized as having an open gamma loop will be processed in such a manner as to derive the required grain texture, which texture is developed by a primary recrystallized microstructure having normal grain growth. In addition, this same composition of matter having an open gamma loop may be processed to produce a (l 10) orientation but in which the microstruction is characterized as a secondary recrystallized microstructure.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a (200) Pole figure for an alloy of the present invention illustrating the cube-on-face texture developed within the alloy.

FIG. 1A is a Histogram for FIG. I.

3 FIG. 2 is a (I I) Pole figure for the alloy of FIG. 1 illustrating the cube-on-edge texture for the same alloy; and

FIG. 2A is the Histogram for FIG. 2.

SUMMARY OF THE INVENTION The present invention comprises the production of an alloy having a composition consisting essentially of from about 4 to about 6% from about 1% to about 1.5% silicon, up to about 0.3% aluminum, up to about 0.8% chromium, less than about 0.03% carbon and the balance being iron with incidental impurities (all percentages being by weight). In alloys which are to be characterized by an open gamma loop, it is preferred to maintain the silicon plus aluminum content within the range between about 1.5% and about 1.8% where such an alloy is to be processed to produce a predominantly (110) [001] texture by secondarily recrystallizing the material. In the open gamma loop materials which are characterized by a secondary recrystallized microstructure, it is preferred to include within the composition from about 0.05 to about 0.3% manganese and from about 0.01% to about 0.03% sulfur for the formation of manganese sulfide therefrom equally good magnetic characteristics are obtained where the alloy contains aluminum nitride. The melted alloy constituents are thereafter cast either in ingot form or by continuous casting, and the cast material is thereafter heated to a hot rolling temperature within the range between about 1,250C and the highest possible temperature that the alloy can withstand without causing that phenomenon known in the trade as buming." After hot rolling to a band the material is cold worked in two or more operations, the last cold working operation being effective for reducing the cross-sectional area to between about 50 and about 75%. Preferably, an intermediate strip or strand anneal is interposed between the cold working operations, said intermediate anneal preferably being performed at a temperature of between about 800C and 900C. The finish gauge material is thereafter subjected to a decarburizing anneal in a wet hydrogen atmosphere followed by a box annealing, usually at a temperature within the range between about 850C and about the Ac, temperature of the alloy in a nonoxidizing and preferably a reducing atmosphere. As thus processed the material will exhibit a preponderance of the grain volume having a (1 10) [001] orientation and a secondary recrystallized microstructure.

To the alloy composition of this invention which basically includes about 4 to about 6% cobalt, about I to about 1.5% silicon and the balance essentially iron with incidental impurities, having an open gamma loop, are made additions of discrete amounts of aluminum and- /or chromium sufficient for improving the resistivity but insufficient for closing the gamma loop, and, in particular, amounts of chromium of up to about 0.8% and- /or aluminum of up to about 0.3% where aluminum is employed, and the alloy is processed for producing in the finished product a primary recrystallized microstructure, care must be exercised to maintain nitrogen at extremely low levels. As indicated, in these alloys the amounts of silicon, aluminum and/or chromium are so adjusted that the gamma loop does not close. This open gamma loop type material without manganese sulfide or aluminum nitride inoculants is also cast into ingots but it is hot worked into plates or strip at a temperature within the range between about 1,000C and about 1 10C and thereafter the material is cold worked in two or more operations to finish gauge. The amount of cold work which is effected to the material during the last stage of the cold rolling, will determine the type of orientation which the alloy will have upon subsequent annealing. That is, the last cold working operation to reduce the gauge of the material to finish gauge, should effect a reduction in cross-sectional area of between about 50 and about in order to obtain a grain orientation during subsequent annealing heat treatment in which a preponderance of the grains have a (l 10) [001] orientation. This cold rolled material at final gauge is thereafter subjected to a final heat treatment at a temperature within the range between 800C and the Ac temperature of the composition for a period of time and will have a primarily recrystallized microstructure and normal grain growth. On the other hand, if the same material is processed in two or more cold working operations and the last of said cold working operation effects a reduction in cross-sectional area of the excess of about 75% and the same material is thereafter subjected to a final anneal within the same temperature range, namely between about 800C and the AC1 temperature of the composition, the final gauge material will exhibit a preponderance of the grains having a [001 orientation which is obtained also by primarily recrystallization and normal grain growth.

Thus the selection of the composition, the processing history to bring the alloy to the finish gauge, the final heat treatment and the resulting microstructure will determine the various magnetic characteristics exhibited by the alloy. These magnetic property manifestations include grain orientation, resistivity, saturation value, permeability, and core loss associated therewith.

DESCRIPTION OF THE PREFERRED EMBODIMENT The alloys to which the present invention is directed consist essentially of from about 4 to about 6% cobalt, up to about 1.5% silicon, up to about 0.3% aluminum, up to about 0.8% chromium, up to 0.3% manganese, up to about 0.03% sulfur, up to about 0.05% nitrogen less than about 0.03% carbon and the balance iron with incidental impurities.

In this respect it should be noted that the effect of silicon in pure iron is well known. Silicon is effective for increasing the resistivity p and for each increment of silicon added, a corresponding decrease is noted in both the saturation value, 8,, and a decrease in the observable core loss due to the improved resistivity. The silicon content is preferred to be maintained at the range of from about 1 to about 1.5% in order to obtain an improved resistivity although the saturation value of the alloy is somewhat reduced.

In addition, silicon is also quite effective in closing the gamma loop and raising the Ac temperature. Accordingly, the silicon content is limited to about 1.5% maximum. This amount of silicon can be employed without closing the gamma loop and is effective for increasing the resistivity and decreasing the core loss. At least about 1% silicon is preferred in order to obtain a suitable increased resistivity and decrease in the core loss values. In alloys where the final microstructure is characterized as secondary recrystallized and either a manganese sulfide or aluminum nitride inoculant is employed, it is preferred to maintain the silicon content near the upper end of the stated range and where the alloy has a primary recrystallized microstructure it is preferred to maintain the silicon content near the lower end of the range. Higher amounts of silicon, that is, near the upper limit may be employed in primary recrystallized alloys where such inoculant as manganese sulfide and aluminum nitride are controlled to critically low levels.

The cobalt content is preferably maintained within the range between about 4% and about 6% for the primary purpose of improving the saturation induction value of the alloy. While cobalt is also effective for increasing the resistivity and will have some slight effect in decreasing the core loss, cobalt is ineffective for stabilizing the gamma field and raises the transformation temperature of the iron to a value above about 910C. Where higher saturation induction values are desired, the alloy will have from about 5 to about 6% cobalt present.

The invention also contemplates the presence of up to about 0.3% aluminum in the alloys. Aluminum is a potent element for closing the gamma loop and raising the Ac, temperature. Aluminum is also effective for increasing the resistivity of the alloy but it also functions in decreasing the saturation value. Accordingly, the aluminum content is preferably limited to about 0.3% maximum. In this respect where the alloy of the present invention is to be processed to a (1 10) [001] orientation employing a secondary recrystallized microstructure, the sum of the silicon plus aluminum should be limited to the range between about 1.5% and about 1.8% with the concomitant amount of cobalt, namely about 4 to 6% being present. In this respect where the sum of the silicon plus aluminum approaches the upper limit of 1.8%, the cobalt content should be maintained within the range between about 5% and about 6% so that the effect of the depression of the saturation induction value may be effectively offset by the addition of the larger amounts of cobalt thereto for improving the saturation value and bringing the same to a value at least as good as pure iron, namely 21 ,500 gauss. As will be more apparent hereinafter silicon contents of between about 1.2 and about 1.5% with the addition of between about 0.2 and 0.3% aluminum is effective for bringing the saturation value to a minimum value of about 21,500 gauss. Since both silicon and aluminum as well as cobalt improve the resistivity, the alloy will have a resistivity p in excess of about 30 microohmcentimeters Such alloy can be heated to 1,000C or slightly higher with no evidence of phase transformation. A temperature of about 1,080C has been the highest temperature observed in these alloys without phase transformation.

Chromium may be present in the alloys of the present invention in an amount of up to about 0.8%. Chromium is quite effective in raising the resistivity of the alloy with only a slight decrease in the saturation value; however, chromium appears to stabilize the gamma phase of iron and as a result partly offsets the effect of silicon in closing the gamma loop in the alloy of the present invention.

While carbon may be present in the alloy of the present invention, it is preferred to maintain the carbon content as low as possible and only about up to 0.03% can be the maximum tolerated. Even with this low amount of carbon it is preferred to decarburize the alloy during subsequent processing so that the effective carbon content within the alloy will be as low as possible thereby reducing any tendency toward magnetic aging during use.

Where the alloy of the present invention is to be utilized as a core material characterized by a (1 10) [001 orientation and a secondary recrystallized microstructure, the sulfur content is preferably maintained within the range between about 0.01% and about 0.03% together with 0.05% to about 0.3% manganese. These two constituents form manganese sulfide which is effective for inhibiting grain growth until the desired (110) texture is developed and thereafter the manganese sulfide may be removed with concomitant grain growth taking place and the material is characterized by a secondary recrystallized microstructure.

The alloy of the present invention may also be produced employing the aluminum nitride mechanism for inoculating secondary recrystallization in the final microstructure of a material having the 1 10) [001] grain orientations. When aluminum nitride is employed, the aluminum content should be maintained within the range between about 0.02 and about 0.3% with a corresponding nitrogen content of between about 0.05 and about 0.05%.

It has been found that with the use of either the manganese sulfide on the aluminum nitride mechanism for producing secondary recrystallization within the final microstructure, (in each instance the final heat treatment must be below the Ac, temperature) the observed magnetic characteristics differ from the alloy which is produced having a primary recrystallized microstructure. As a result, the secondary recrystallized materials will be more attractive in some applications than the primary recrystallized materials. For example, the oriented secondary recrystallized materials generally exhibit higher B values and inferior core losses than the [001] oriented material which has a primary re crystallized microstructure. Consequently in direct current application where core loss is not a factor, the [001] oriented material having a secondary recrystallized microstructure may be preferred.

Where the alloy of the present invention is to be processed so that either a (1 10) [001] grain orientation, or a 100) [001] grain orientation is obtained, but with a primarily recrystallized microstructure, it is preferred to maintain the sulfur content as low as possible and in any event the sulfur content should be less than about 0.01%.

Where the alloy contains between about 4 and about 5% cobalt, with substantially no intentional additions of silicon but with deliberate additions of chromium, the amount of chromium present will deterine the final texture in the alloy regardless of the processing to which the alloy is subjected as will be hereinafter set forth. In this respect where the chromium content exceeds about 0.30% with the cobalt content between about 4% and less than about 5% a (1 10) [001] orientation will be obtained regardless of whether the process leading to (110) [001] grain texture or the process ordinarily leading to the (100) [001] grain texture is employed.

On the other hand if the chromium content is maintained below about 0.3% with less than about 5% cobalt and no substantial additions of silicon, utilization of the process set forth hereinafter for producing 100) [001] type texture will result in the attainment of that texture when following the teachings of the present invention.

In the alloys which have a primary recrystallized microstructure it is preferred to maintain the silicon content between about 1 and about 1.5% and up to about 0.8% chromium. Where, on the other hand, a secondary recrystallized microstructure is desired, it is preferred to use aluminum and limit the silicon content to the range between about 1.0% and about 1.5% with a sum of the silicon plus aluminum within the range between about LS and about l.8%. The corresponding nitrogen range is between about 0.005 and about 0.05%. Where the sum of the silicon plus aluminum is toward the high side it is preferred to maintain the cobalt content within the range between about 5 and about 6%, although strong orientations and high B values are obtained in secondary recrystallized materials where the cobalt content is near 4%.

The alloys of the present invention may be made by following any of the well known steel making practices. The constituents are melted and thereafter cast and it is preferred that conventional casting practices be used to form an ingot which may thereafter be hot worked to a thick band in the conventional manner. Following hot working the alloy is thereafter cold worked in one or more operations to finish gauge and, depending upon the orientation and the composition, the final heat treatment is selected in accordance therewith as well as the rolling schedules which will appear more fully hereinafter.

SECONDARY RECRYSTALLIZED MICROSTRUCTURE-( 1 10) [001] ORIENTATION After melting the constitutents including iron in which the silicon content is within the range between I and l.5% or the silicon plus aluminum is limited to the range between about 1.5 and about 1.8%, with a corresponding nitrogen content between 0.005 and 0.05%, the cobalt is present within the range between about 4% and about 6%, or with up to 0.3% manganese and sulfur being present within the range between about 0.01% and about 0.03% the latter two element ranges being employed only where the MnS mechanism is employed, the melt is preferably cast into ingots which are thereafter hot rolled to an intermediate gauge strip or band. In hot working the ingot down to the hot rolled band size the material is preferably heated to a temperature in the range between about l,250C and the highest temperature that the material will withstand without producing that phenomenon known as buming which latter includes the liquefication of low melting phases usually commencing at or adjacent to the grain boundaries of the as cast material. Heating the ingot initially to a high temperature in this range can be deferred if a two step practice is employed wherein the ingot is first hot rolled at a lower temperature to a slab or other intermediate hot worked product and thereafter the slab or other intermediate hot worked product is thereafter heated to said high temperature and then hot rolled into a band. Good results may be obtained where the material is heated to a temperature of about l,370C and hot worked down to a gauge of about 0.08 inch in thickness. While heavier gauges can be utilized, namely gauges anywhere between about 0.06 and about 0.25 inch in thickness, it is preferred to aim for a thickness of about 0.08 inch.

Following hot working, the material is preferably descaled and may be annealed at this time followed by the initial stage of cold rolling. The initial cold working operation usually effects a reduction in cross-sectional area of the material of between about 50 and about of the hot worked gauge cross-sectional area. Thereafter the material is preferably given an intermediate strip anneal at a temperature within the range between about 800C and 900C following which the material is again descaled and cold worked to finish gauge, for example 0.006 to 0.015 inch, and preferably to a gauge of about 0.012 inch in thickness. The final cold working to finish gauge effects a reduction in crosssectional area of between 50 and about 75% following which the steel is given a decarburization annealing heat treatment.

Preferably the decarburization annealing heat treatment takes place by means of a strip or a strand anneal which is usually conducted at a temperature of between about 760C and about 870C preferably in a hydrogen atmosphere having a dew point in excess of about 20C. Following the decarburization anneal the material, usually in coil form, is thereafter subjected to a box annealing heat treatment, said box annealing heat treatment taking place at a temperature of between about 800C and the Ac, temperature of the material undergoing treatment. This box annealing heat treatment usually takes place in a non-oxidizing or reducing atmosphere, such as dry hydrogen of a 40C dew point, in the temperature range indicated for a period in excess of about 24 hours, and following slow cooling to room temperature, the material will exhibit a preponderance of the grains having a {001] orientation and a secondary recrystallized microstructure.

PRIMARY RECRYSTALLIZED MICROSTRUCTURE-(l 10) [00]} TEXTURE-H PROCESS In order to produce the l 10) [001] texture in alloys having a primary recrystallized microstructure, the composition is selected so that there is present from about 4 to about 6% cobalt, about 1% to about 1.5% silicon, up to about 0.8% chromium, less than 0.03% carbon and less than 0.01% sulfur with the balance iron and incidental impurities. While small amounts of aluminum can be present in this alloy, it is preferred to maintain the silicon at the low end of the range and the addition of chromium is of some benefit. In the absence of any appreciable amount of aluminum, up to about 0.8% chromium can be employed with a silicon content within the range between about 1 and about 1.5%.

This material is melted in the same manner as in the previous example and is preferably cast into ingots, continuous slabs or other suitable form. The cast material is thereafter hot worked at a temperature preferably within the range between about l,000C and about 1,lO0C in order to reduce the thickness of the material to a band in the range between about 0.08 inch and about 0.15 inch. Following hot working, the material is thereafter descaled and preferably annealed at a temperature within the range between about 800C and the Ac, temperature of the alloy, for a time period of about 1 hour.

Thereafter, the hot worked material is cold worked in one or more operations, at least the last cold working operation efiecting a reduction in the cross-sectional area of between about 50 and about 75% with an intermediate anneal interposed between each cold working operation.

It will be appreciated that the initial cold working operation may be what has been termed a hot-cold working operation that is, a cold working at an elevated temperature usually within the range between room temperature and about 300C. Such hot-cold working is also included within the context cold working in one or more operations" as utilized hereinbefore. It should be pointed out however that preferred results are obtained when the final cold working operation is done at essentially room temperature, said final cold working effecting a reduction in cross-sectional area between about 50 and about 75%.

For example, a typical schedule of thickness may include hot working to a band of about 0.10 inch in thickness, followed by descaling, annealing and hot-cold working at a temperature of up to about 260C to a thickness of about 0.030 inch, intermediate annealing for about l hour at 900C followed by cold working to a finish gauge of about 0.01 1 inch in thickness.

Following reduction to finish gauge, the material is surface cleaned and thereafter subjected to a final annealing in a nonoxidizing or a reducing atmosphere at a temperature within the range between about 800C and the Ac, temperature of the composition being so processed. Preferably the material is maintained at said temperature for a time period of between about 24 and about 48 hours and thereafter slow cooled to room temperature. This processing results in the final alloy exhibiting a preponderance of the grains having a (1 10) [001] orientation, a primary recrystallized grain structure and normal grain growth in comparison to the secondary recrystallized microstructure of the material of the previously described process.

The foregoing described process has been denominated the H Process and the next to be described process will be designated as the C Process.

PRIMARY RECRYSTALLIZED MICROSTRUCTURE-(lOO) [O01] ORIENTATION C PROCESS Substantially the same material as is employed in H process may be employed in the C Process with one important exception. This exception is that where the silicon content is omitted from the composition and chromium is utilized, the chromium content must be limited to a maximum of about 0.3% in order to obtain the (100) [001] orientation. Where the chromium content exceeds about 0.3% and, in particular amounts of between about 0.5% and about 0.8%, the following described processing will produce a final gauge sheet of (110) [001] grain texture as opposed to the (100) [001] texture. Aside from the foregoing compositional limitations, substantially the same composition is employed as in the H Process in order to obtain the (100) [001] orientation in a primary recrystallized microstructure.

In this process, a melt is made including less than about 0.03% carbon, less than about 0.01% sulfur,

1.5% silicon, up to about 0.3% aluminum, up to about 0.8% chromium and the balance iron with incidental impurities. The melt is preferably cast into an ingot or continuously cast slab or billet and the product resulting is hot worked into a band at a temperature within the range between about 1,000C and about 1,100C. Typical of the gauge of the band at the conclusion of the hot working operation is a gauge within the range between about 0.100 inch and about 0.250 inch in thickness. The ultimate gauge will of course depend upon the desired final gauge and the requisite cold reductions to take place following the hot working operatron.

Following hot working, the material is descaled, usually by pickling, prior to the commencing of any cold working operations. Following descaling it is preferred to anneal the material at a temperature within the range between about 800C and the Ac temperature of the composition usually in an inert or reducing atmosphere. Thereafter the material is cold worked in one or more operations to finish gauge with at least the last of said cold working operations effecting a reduction in cross-sectional area in excess of about Once again an intermediate anneal is interposed between successive cold working operations, said intermediate anneal usually taking place at a temperature within the range between about 800C and the Ac, temperature of the material. It will be appreciated that in cold working the material, hot-cold working is contemplated the same as set forth hereinbefore with respect to the H process. Where more than one cold working operation is performed on the material at least the last cold working operation should effect the reduction in cross-sectional area in excess of about 75% and optimum results are obtained where each cold working operation effects a reduction in cross-sectional area of in excess of about 75%.

Typical of such a schedule for cold working the material to a finish gauge of about 0.01 1 inch would include hot rolling to a band thickness of about 0. 180 inch, hotcold working the band at a temperature of about 260C to a gauge of about 0.080 inch, annealing, followed by hot-cold working to 0.040 inch in thickness and, without any intermediate annealing, cold working at ambient temperature to the finish gauge of about 0.011 inch. Following cold working to finish gauge, the surface of the material is cleaned as required and thereafter subjected to a primary recrystallization anneal at a temperature of within the range between about 800C and the Ac, temperature of the material for a time period of from about 24 to 48 hours. During such final annealing, an atmosphere of dry hydrogen having a dew point of less than about -40C is preferably employed.

Utilizing the three foregoing processes as well as various chemical compositions a number of alloys were made and tested, the results of which appear hereinafter. Reference is directed to Table l which includes the composition of a series of alloys made and tested for their saturation induction as well as resistivity and from about 4 to about 6% cobalt, from about I to about 60 transformation characteristics.

TABLE 1 Alloy %Co %Si %Al (O) P 1200C Phase pflrcm) Transformation 12 4 1.5 21,400 31.4 Yes 32 4 1.3 0.3 21,600 33.1 Yes 34 5 1.4 0.3 21,500 35.4 Yes 35 6 1.4 0.3 21,700 35.5 Yes All compositions which are set forth in Table l were primarily designed for an alloy having a saturation induction approaching that of pure iron, that is, at least 21,500 gauss, and a resistivity in excess of about 30 microohm-centimeters. From the results recorded in Table I it is seen that the addition of only about 1.5 silicon to a 4% cobalt-iron alloy gave saturation induction values slightly lower than that of the goal values of 21,500g and suitable resistivity values. However, by lowering the silicon content to 1.3% and adding 0.3% aluminum to the same alloy increased the saturation to above the goal value with suitable resistivity. Further increases in the cobalt content and silicon to the amounts shown was also effective in achieving the ini tial goals. Thus the potent effect of silicon is clearly evident.

In order to substantiate phase transformation, dialatometric measurements were performed on alloys 32, 34 and 35. These measurements confirm that transformation took place at temperatures between about 1,060C and about 1,080C. Thus it is clear that prior art processes for producing a secondary recrystallized microstructure and a preferred cube-on-edge orientation cannot be used.

As stated previously, the alloy of the present invention can be produced having a cube-on-edge orientation and a secondary recrystallized microstructure. Both the manganese sulfide and aluminum nitride innoculating mechanisms have been employed. In addition, it has been demonstrated that substantial sulfur reductions occur during the final heat treatment which takes place at a temperature of between 800C and the Ac temperature of the alloy for developing the cubeon-edge orientation and the secondary recrystallized microstructure.

The compositions listed in Table II were all selected to employ the manganese sulfide mechanism except for Alloy No. SB 158 which employs the aluminum nitride mechanism. In addition, Alloy No. 1663 which has a nominal manganese content of 0.02% would not be expected to produce a strong cube-on-edge orientation because the manganese content is below the lower limit and hence insufiicient manganese sulfide would be formed.

The nominal compositions set forth in Table II were vacuum induction melted as 7,500 gram nominal weight ingots. Portions of all alloys were moulded by the following process:

1. Hot Roll at 900C, 1,100C or 1,350C to hot roll band thickness of 2.0 mm (0.079 in) 2. Clean surface 3. Cold Roll to 0.60 mm (0.024 in) [70% reduction] 4. Annual 1 to 5 min. at 850C 5. Cold R011 to 0.28 mm (0.011 in) [53% reduction] A portion of alloy SB 158 was also rolled from the hot roll band thickness of 2.0 mm to an intermediate gauge of 0.45 mm [77% reduction], annealed and cold rolled to a finish thickness of O. 1 5 mm (0.006 in) [67% reduction] Individual strips were annealed for 48 hours in dry hydrogen in a gradient furnace having a temperature range variation of about 150C over a 450 mm sample length, and grain structure was studied. Other torque and Epstein samples were box annealed in dry hydrogen for 48 hours at 900 to 1,000C. Torque curves and standard dc and 60 hz magnetic tests were run on selected samples.

Reference is now directed to Table III which lists the torque values of the alloys of Table II.

TABLE II] Torque Properties The composition of alloy 836 was aimed at obtaining Mn and S additions to provide a grain boundary inhibition for secondary growth. It may be noted that the processing is based on standard commercially available material practice. Examination of a 0.28 mm thick strip annealed in the gradient furnace from about 900 to 1,050C indicated that this alloy transformed from the a to 7 phase at a temperature slightly above 1,000C. On the other hand, considerable secondary growth occurred between about 975 to 1,000C. A torque sample punched from an area which had complete secondary growth had a peak torque of 189,400 erg/cm and a peak ratio of 0.36, indicating a strong [001] texture.

Alloys 1661, 1662 and 1663 were similarly processed to a final gauge of 0.28 mm. Torque values for samples given a 2 min. strip anneal at 825C, followed by a 48 hour 950C anneal, are given in Table II]. Samples from alloys 1661 and 1662, which have Mn contents in the normal commercial oriented silicon steel range, had very high peak torque values. Although peak ratios were somewhat higher than observed in commercial material, a strong l 10) [001 texture is indicated; secondary grain structures similar to commercial oriented silicon steel were observed in these samples. For the alloy with the low Mn content, 1663, poorer peak torque was obtained probably due to the low manganese content. Sorne resulting in insufficient inclusion size and distribution.

Alloy SB 1 58, which had Al and N additions, was processed to final thicknesses of 0. 15 and 0.28 mm. A strip of 0.28 mm material was annealed in the gradient fur nace from about 900 to 1,050C. Very large secondary grains were obtained between about 910 and 930C, and smaller secondary grains were observed up to about 975C; the a-y phase transformation was ob served slightly above 1,000C. A grain in this sample was so large that an entire torque disc could be punched out of it. This sample had a peak torque of 253,000 erg/cm and a peak ratio of 0.3 1 representing a good 1 single crystal value for this alloy composition. The torque values set forth in Table 11] indicate very strong secondary l 10) [001] textures.

In the commercially available oriented silicon steels of the prior art which employ the manganese sulfide innoculation mechanism, it is imperative to remove the sulfur content to very low final levels after the manganese sulfide has performed its function. This is accomplished by annealing in hydrogen for long time periods at temperatures of about 1,200C. The high temperatures involved are effective for removing sulfur and fastening grain growth of the favorably oriented grains of the secondary recrystallized microstructure. This has the effect of improving the coercive force and providing for a larger grain size, both of which ultimately influence the core loss exhibited by the alloy.

Since, as set forth hereinbefore, heating the alloy of the present invention to a temperature in excess of about 1,050C will cause the alloy to transform from the alpha phase to the gamma phase and thereby prevent the attainment of any preferred orientation on a secondary recrystallized microstructure, the final heat treatment must take place at a temperature below the AC1 temperature of the alloy. Quite surprisingly, a final anneal in dry hydrogen for 48 hours at 950C was effective for removing sulfur. The test results set forth hereinafter indicate the final sulfur contents for the alloys tested, which originally contained 0.02% sulfur.

TABLE IV Sulfur Present After Final Anneal at 950C For 48 hours.

Alloy No. S

the (1 10) [001] oriented alloy with a secondary recrystallized microstructure may find their greatest application in DC. machinery.

Since the alloy of the present invention is also selected so that the improved saturation values and resistivity will be obtained in an alloy having a primary recrystallized microstructure a series of additional alloys were made and tested having the composition set forth hereinafter in Table VI.

TABLE VI Alloy Analyzed No. Co %Si %Mn %Cr %C Alloy Nominal No. Co Si %Mn %Cr %S %C SE44 4 1.5 0.15 0.005 0.03 SE45 4 1.5 0.15 0.01 003 S846 4 1.5 0.15 0.01 SB47 4 1.5 0.15 0.005 0.01 SB48 4 1.5 0.15 SE49 4 1.5 0.05 0.03 SE50 4 1.5 0.05 0.15 0.03

The alloys having the composition set forth in Table VI were processed in accordance with the H process set forth hereinbefore. More specifically these alloys were cast into ingots which were thereafter hot rolled at a temperature of 1,050C to bands of a thickness of 0.100 inch. Following hot rolling, the bands were pickled, annealed in argon for 1 hour at 900C, hot-cold rolled at 260C to a thickness of 0.030 inch reduction) annealed for one hour in argon at 900C and cold rolled to a finish gauge of 0.01 1 inch in thickness (63% reduction). The finish gauge material was cleaned and thereafter annealed in dry hydrogen for a time period of 48 hours at a temperature of either 850C or 900C employing a programmed heating and cooling cycle of 50C per hour.

Following cooling to room temperature the magnetic characteristics thereof were measured the results of which appear hereinafter in Table Vll.

TABLE V Magnetic Properties Alloy No. Thickness Anneal Hc B, m Pcl5/6O Pcl7/6O (mm) (Tem C) (Oe) (k6) (k0 (w/lb) (w/lb) The high B value for alloy 1662 again indicates a high TABLE V11 degree of orientation, though coercive force is somewhat lower than that usually obtained for primary re- Temp, Peak Torque l-l 13,. B crystallized samples with similar composition and de- A110)! Tmque Ram (08) (K?) (m) gree of texture as will be set forth more fully hereinaf- 60 1459 900 189 400 0 4| 0 I38 189 2H ter. The losses of this sample are somewhat higher than 146 1350 153:200 0.39 0.221 17.7 20.2

' 1461 900 131,400 0.40 0.168 18.1 20.5 commercially available material of the same tl'uckness, 1463 900 80,400 043 (M n9 m6 mainly because of its lower resistivity with respect to 1464 850 143200 044 Alloy 513-158, the coercive force of this sample is lower and the B higher than typically obtained for 0.15 mm 65 thick primary recrystallized alloys with similar compositions, yet the losses are somewhat higher than normally observed for primary textured samples. These higher losses are most likely a result of the very large grain size of the secondary recrystallized sample. Thus,

The peak torque and torque ratios were determined by a torque magnetometer test of disks punched from the sheet. From the test results recorded in Table Vll it is seen that the low peak ratios indicate a high degree [001] texture. While alloys 1459 and 1463 have a high peak torque, the torque ratios indicate that a preponderance of the grains have a (110) [001] texture development. Neither the B nor the B values are as high for the last four alloys as for alloy 1459 where no deliberate chromium additions were made.

It is believed significant that alloy 1464 which did not have any deliberate additions of silicon and which had 0.6% chromium added to a 4% cobalt iron alloy did not produce a (100) [001] grain texture even when manufactured by means of the C process set forth hereinbefore. Instead, the low torque ratio indicated a preponderance of (110) [001] texture development in this alloy by process C.

Reference is directed to Table Vlll which illustrates the effect of employing the H type processing in the identical manner as for the Table VI] specimens with the exception that the last set of duplicate alloys were not subject to a hot-cold working, and their final gauge thickness was 9 mils, as was SE50, the remainder being 11 mils thick. The magnetic characteristics exhibited thereby are as follows:

nominal l 1 mill thickness.

Alloy 1459 was also processed employing the C Process. Alloy 1459 had the composition as set forth hereinbefore in Table V1. In applying the C Process to the 1459 composition the ingot was hot rolled at 1,050C to a thickness of 0.180 inch, pickled and thereafter annealed for 5 hours at a temperature of 900C. Following annealing, the hot worked material was cold rolled at 260C to a thickness of 0.080 inch and thereafter annealed again for 5 hours at 900C. After intermediate annealing, the material was warmed rolled at 260C to a gauge of 0.040 inch and thereafter immediately cold rolled at room temperature to a thickness of 0.01 1 inch (72% reduction).

Epstein samples were cut in the rolling direction and torque disks were annealed for 48 hours at a temperature of 900C in dry hydrogen having a dew point of less than C, said heating and cooling having been programmed to take place at a maximum of C per hour. The following magnetic measurements were obtained:

TABLE Vlll Peak Torque "0 B11] 100 risian rimal Alloy Process Torque Ratio (0e) (kG) (kG) (W/lb) (W/lb) SE44 H 164,000 .48 0.245 18.0 20.5 0.71 1.03 S845 H 124,000 .46 0.355 17.9 20.4 090 1.30 S846 H 186,000 .41 0.153 18.6 20.1 0.67 0.89 S847 H 193,000 .42 0.212 19.5 21.4 0.63 0.83 5848 H 173,700 .46 0.181 18.7 20.2 0.67 090 $1349 H 148,800 .53 O. 166 18.0 20.7 0.67 094 S850 H 153,800 .50 0.163 18.2 20.8 0.66 0.92

S844 H 167.200 .40 0.228 18.1 20.5 0.82 1.10 S845 H 96,400 .40 0.336 17.5 20.0 0.97 137 S846 H 193,200 .39 0.150 19.3 21.6 0.67 089 S847 H* 178,800 .40 0.218 19.1 21.1 0.74 0.97 8848 H 175,000 .43 0.168 18.8 2l.l 0.71 095 S849 H 194,500 .42 0.136 18.7 20.9 0.67 0.90 S850 H 200,300 .42 0.141 19.1 21.3 0.55 0.75

All working done cold TABLE IX dc Hz Peak Tor ue Peak He 13, E B P P P Process (ergs/cm Ratio (06) (k6) (KG) m The data contained in Table V111 indicate that good torque values are obtained for all alloys except S845 which contains 0.010 sulfur. Sulfur additions generally raise the coercive force but good textures were obtained with the additions of up to and including 0.005% sulfur. Moreover, it becomes apparent that by comparing the peak torque as well as the ratios, these alloys exhibited a preponderance of the grains having a (110) [001] orientation, which orientation was obtained where complete cold rolling was substituted for hotcold rolling. While the core loss results appear to be somewhat inconsistent, this may be explained by the fact that the final gauge of all of the hot-cold work samples and the sample SB50 which was done completely at room temperature, was close to nine mils while all the other compositions had a finish guage near the The high peak torque values and the low peak ratios indicate that process H produced a high degree of 1 10) [001] orientation. The B value is quite high and the 17 kilogauss core loss is similar to that of oriented 3.25% silicon steel known commercially as type M5.

On the other hand, process C which provided a peak torque as indicated and a high peak ratio demonstrates that the C process produced a preponderance of the grains having a [001] orientation similar to that observed in higher cobalt containing alloys. As would be expected, the induction and loss values were not as good as those measured on the H Process material which produces a preponderance of the grains having a [001] orientation.

Referring now to the Figures, X-Ray Pole figures were obtained on alloy 1459 which was processed by both the process and the H" process. FIGS. 1 and 1A illustrates the strong cube-on-face 100) [001 texture of the process C sample and analysis closely indicates that 79% by volume of the grains had the (100) plane parallel to within 15% of the surface of the alloy and 67% were parallel to within of the surface of the alloy. These results clearly correlate to the magnetic data set forth in Table IX.

When the same alloy was processed using the H process much stronger oriented textures were obtained. Thus FIGS. 2 and 2A which are a (110) pole figure and Histogram respectively show the strong (110) [001 orientation. Actual measurements reveal that 86% by volume of the grains have the 1 10) plane oriented parallel to within of the surface of the alloy and 73% within 10 of the surface of the alloy. Thus the high degree of orientation explains the excellent magnetic characteristics exhibited by these alloys.

From the foregoing test results it is apparent that three different types of processing give different results: the one being manifested by a secondary recrystallized microstructure in which the grains assume an orientation of (1 10) [001]; and, depending upon the processing employed, the alloys will show a grain orientation of(l 10) [001] on the one hand or (100) [001] on the other, both of these latter having a primary recrystallized grain structure and normal grain growth characteristics.

A properly selected process as herein disclosed applied to the alloy compositions set forth will produce a finally annealed sheet or strip having over 50% of its grain volume comprising grains whose crystal lattices are such that the (100) or the (110) plane thereof is parallel within 15 to the plane of the surface of the sheet and two edges of the selected plane are parallel to the rolling or working direction of the sheet within 15. In many cases well over 50% of the grain volume comprises grains with two cube edges within 10 of the working direction, with the (l 10) or (100) planes also being within 10. In the usual commercial practice, the sheets or strips of the material are produced by unidirectional rolling, particularly during the cold rolling stages.

It will be appreciated that the usual surface insulation coatings will be applied to the magnetic sheets, for example, phosphate coatings, magnesium oxide coatings or glass coatings which react with or adhere to the sheet surface.

As thus processed, these materials find suitable use as a core material employed in both distribution and power transformers of reduced weight and size due to the higher induction values and the higher resistivity values exhibited by the alloys of the present invention. Other electrical equipment requiring oriented magnetic steel can be benefited by use of the oriented cobalt iron magnetic products of this invention.

We claim as our invention:

1. A worked and heat treated alloy having a substantially flat surface and which alloy member is suitable for use as a transformer core material, consisting essentially of from about 4 to about 6% cobalt, up to about 1.5% silicon, up to about 0.3% aluminum, up to about 0.8% chromium, up to about 0.3% manganese, up to about 0.03% sulfur, up to about 0.05% nitrogen, less than about 0.03% carbon and the balance essentially iron with incidental impurities, the alloy having an orientation in which over 50% by volume of the grains have a unit cube orientation selected from the group consisting of (110) and in which the selected plane is parallel to within 15 of the plane of the surface of the alloy and in which two of the cube edges of the selected plane are aligned parallel to within 15 of the working direction. the alloy also having a resistivity in excess of 30 microohm-centimeters.

2. The alloy of claim 1 in which the silicon content is within the range of between 1 and 1.5%.

3. The alloy of claim 1 in which the total of silicon and aluminum is within the range of between about 1.5% and about 1.8%.

4. The alloy of claim 1 in which the cobalt content is maintained within the range of between about 5 and about 6% and the total silicon and aluminum content is within the range of between about 1.5 and about 1.8%.

5. The alloy of claim 1 in which the cobalt content is between about 4 and about 5%, the silicon content is between about 1 and 1.5%, the aluminum content is between about 0.1 and about 0.3%, and the nitrogen content does not exceed about 0.005%.

6. A worked and heat treated alloy having a substantially flat surface and which alloy member is suitable for use as a transformer core material, consisting essentially of from about 4 to about 6% cobalt, from about 1.3 to about 1.5% silicon, up to about 0.3% aluminum, up to about 0.8% chromium, up to about 0.3% manga nese, up to about 0.03% sulfur, up to about 0.05% nitrogen, less than about 0.03% carbon and the balance being iron with incidental impurities, the alloy having an orientation in which over 50% by volume of the grains have a unit cube orientation selected from the group consisting of (l 10) and (100) in which the selected plane is parallel to within 10 of the plane of the surface of the alloy and in which two of the cube edges of the selected plane are aligned parallel to within 10 of the working direction, the alloy having a resistivity in excess of 30 microohm-centimeters.

7. The alloy of claim 6 in which the total of silicon and aluminum is within the range of between about 1.5 and about 1.6%.

8. The alloy of claim 6 in which the cobalt content is between about 5 and about 6% and the total of silicon and aluminum is within the range of between about 1.5% and about 1.6%.

9. The alloy of claim 6 in which the cobalt content is within the range of between about 4 and about 5%, the total of silicon and aluminum is within the range of be tween about 1.5 and about 1.6% and the nitrogen content does not exceed 0.005%.

10. A worked and heat treated alloy having a substantially flat surface and which alloy is suitable for use as a transformer core material, consisting essentially of from about 4 to about 6% cobalt, from about 1 to about 1.5% silicon, from about 0.1 to about 0.8% chromium, less than about 0.01% sulfur, less than about 0.03% carbon and the balance being iron with incidental impurities, the alloy having an orientation in which over 50% by volume of the grains have a unit cube orientation selected from the group consisting of and (100) in which the selected plane is parallel to within 10 of the plane of the surface of the alloy and in which two of the edges of the selected plane are aligned parallel to within 10 of the working direction, the alloy also having a resistivity of at least 30 microohmcentimeters.

II. The alloy ofclaim 10 in which the sum of the silicon and chromium content does not exceed about 2%.

12. The alloy of claim 10 in which the cobalt content is within the range of between about 4% and 5%.

13. A worked and heat treated alloy having a substantially flat surface and which alloy is suitable for use as a transformer core material consisting essentially of from about 4 percent to about 6% by weight of cobalt, up to about 1.5% silicon, up to about 0.8% chromium, up to about 0.3% aluminum, up to about 0.3% manganese, up to about 0.03% sulfur, up to about 0.05% nitrogen, the aluminum, manganese, nitrogen and sulfur being selected within the respective ranges stated to provide effective amounts of at least one inoculant of the group consisting of manganese sulfide and aluminum nitride, less than about 0.03% carbon and the balance iron with incidental impurities, the grains of the alloy having an orientation in which over 50% by volume of the grains have a unit cube orientation in which the (1 10) plane is parallel to within of the plane of the surface of the alloy and in which two of the cube edges of the (1 l0) plane aligned within 15 of the working direction, the alloy being further characterized by a secondary recrystallized microstructure, a resistivity in excess of 30 microohm-centimeters and a saturation induction of at least 21,500 gauss.

14. The alloy of claim 13 in which the cobalt content is within the range between about 4 and about 5% and the inoculant is manganese sulfide.

15. The alloy of claim 13 in which the cobalt content is within the range between about 4% and about 5%, the inoculant is manganese sulfide and in which the alloy contains up to 0.3% aluminum and a nitrogen content of less than about 0.005%.

16. The alloy of claim 13 in which the silicon content is within the range of between about 1% and about 1.5%.

17. The alloy of claim 13 in which the cobalt content is within the range between about 4 and about 5%, the inoculant is aluminum nitride and the sulfur content is less than 0.01%.

18. A worked and heat treated alloy having a substantially flat surface and which alloy is suitable for use as a transformer core material consisting essentially of from about 4 to about 6% cobalt, from about 1.0 to about 1.5% silicon, at least one inoculant selected from the group consisting of manganese sulfide and alumi num nitride, the respective amounts of the components of the inoculants being limited to from about 0.05 to about 0.3% manganese with a corresponding sulfur content of between about 0.01% and about 0.03% where manganese sulfide is the inoculant and between about 0.02% and about 0.3% aluminum with a corresponding nitrogen content of between about 0.005% and about 0.05% nitrogen where aluminum nitride is the inoculant, less than 0.03% carbon and the balance iron with incidental impurities; the alloy having an orientation in which over 50% by volume of the grains have a unit cube orientation in which the (1 10 plane is parallel to within 10 of the plane of the surface of the alloy and in which two of the cube edges of the (110) plane are aligned parallel to within 10 of the working direction, the alloy being further characterized by a secondary recrystallized microstructure, a resistivity in excess of 30 microohm-centimeters and a saturation induction of at least about 21,500 gauss.

19. The alloy of claim 18 in which the cobalt content is within the range between about 4 and about 5%, the inoculant is manganese sulfide and the alloy contains from about 0.1% to about 0.3% aluminum and not more than 0.005% nitrogen.

20. A worked and heat treated alloy having a sub stantially flat surface and which alloy is suitable for use as a transformer core material consisting essentially of from about 4 to about 6% cobaa, up to about 1.5% silicon, up to about 0.8% chromium, up to about 0.3% aluminum, up to about 0.3% manganese, less than 0.01% sulfur, less than about 0.005% nitrogen, less than about 0.03% carbon and the balance iron with incidental impurities, the alloy having an orientation in which at least 50% by volume of the grains have a unit cube orientation in which the (1 l0) plane is parallel to within 15 of the surface of the alloy and in which two of the cube edges of the (1 10) plane are aligned within 15 of the working direction, the alloy being further characterized by a primary recrystallized microstructure and a resistivity in excess of 30 microohm-centimeters.

21. The alloy of claim 20 in which the silicon content is within the range between about 1 and about 1.5%.

22. The alloy of claim 20 in which the total silicon and chromium content is within the range between about 1 and about 2%.

23. The alloy of claim 20 in which the cobalt content is within the range between about 4 and about 5% and the total silicon and chromium content is within the range between about 1.5% and about 1.8%.

24. A worked and heat treated alloy having a substantially flat surface and which alloy is suitable for use as a transformer core material consisting essentially of from about 4 to about 5% cobalt, from about 1 to about 1.5% silicon, up to 0.8% chromium, less than 0.01% sulfur, less than 0.005% nitrogen, less than 0.03% carbon and the balance iron with incidental impurities, the alloy having an orientation in which at least 50% by volume of the grains have a unit cube orientation in which the (l 10) plane is parallel to within 10 of the surface of the alloy and in which two of the cube edges of the 1 10) plane are aligned parallel to within 10 of the working direction, the alloy being further characterized by a primary recrystallized microstructure and a resistivity of at least 30 microohm-centimeters.

25. The alloy of claim 24 in which the chromium content is within the range of between about 0.5% and about 0.8%.

26. A worked and heat treated alloy having a substantially flat surface and which alloy is suitable for use as a transformer core material consisting essentially of from about 4 to about 6% cobalt, up to about 1.5% silicon, up to about 0.8% chromium, up to about 0.3% aluminum, less than 0.01% sulfur, less than 0.005% nitrogen, less than about 0.03% carbon and the balance iron with incidental impurities, the alloy having an orientation in which over 50% by volume of the grains have a unit cube orientation in which the plane is parallel to within 15 of the surface of the alloy and in which two of the cube edges of the (100) plane are aligned parallel to within 15 of the working direction, the alloy being further characterized by a primary recrystallized microstructure and a resistivity of at least 30 microohm-centimeters.

27. The alloy of claim 26 in which the chromium content does not exceed 0.3% in the absence of silicon.

28. The alloy of claim 26 in which the cobalt is within the range between about 4 and about 5% and the total of silicon and chromium content does not exceed about 2%.

29. The alloy of claim 26 in which the total silicon and chromium content is within the range between about 1 and about 2%.

30. In the process for producing (1 [001 texture in an alloy suitable for use as a transformer core material, the steps comprising, hot working a casting having a composition including less than 0.03% carbon, less than 0.01% sulfur, from about 4% to about 6% cobalt, up to about 1.5% silicon, up to about 0.3% aluminum, up to about 0.8% chromium, less than 0.005% nitrogen and the balance iron with incidental impurities, the hot working of the casting being at a temperature within the range of between about l,000C and about 1,100C, cold working the hot worked material in two or more operations to finish gauge, the last cold working operation effecting a reduction in cross-sectional area of between 50 and 75% with an intermediate anneal interposed between successive cold working operation, said intermediate anneal being at a temperature within the range between about 800C and the Ac, temperature of the composition, and thereafter annealing the finish guage material at a temperature within the range between about 800C and the Ac, temperature of the composition, the material exhibiting a preponderance of the grains having a 1 10) [001 orientation, a primary recrystallized microstructure and normal grain growth.

31. The process of claim 30 in which part of the cold working takes place at a temperature between room temperature and about 500C.

32. The process of claim 30 in which the final annealing is a box anneal for a time period of between 24 and 48 hours in a reducing atmosphere having a dew point of less than about 40C.

33. The process of claim 30 in which the final cold working operation to finish gauge effects a reduction in cross-sectional area within the range between about 60 to 70%.

34. In the process for producing (100) [001] texture in an alloy suitable for use as a transformer core material, the steps comprising casting a melt having a composition including less than 0.03% carbon, less than 0.01% sulfur, from about 4 to about 6% cobalt, up to about 1.5% silicon, up to 03% aluminum, up to about 0.8% chromium, less than about 0.005% nitrogen and the balance iron with incidental impurities, hot working the casting at a temperature within the range between about 1,000C and 1,100C, cold working the hot worked material in two or more operations to finish gauge, at least the cold working operation effecting a reduction in cross-sectional area in excess of about with an intermediate anneal interposed between each cold working operation, said intermediate anneal being at a temperature within the range between about 800C and the Ac, temperature of the composition, and final annealing the finish gauge material at a temperature within the range between about 800 C and the Ac temperature of the composition, the material exhibiting a preponderance of the grains having a [001] orientation, a primary recrystallized microstructure and normal grain growth.

35. The process of claim 34 in which the fmal annealing is a box anneal for a time period of between 24 and 48 hours in a reducing atmosphere having a dew point of less than about 40C.

36. In the process for producing l 10) [001] texture in an iron base alloy suitable for use as a transformer core material, the steps comprising, casting a melt having a composition from about 4 to about 6% by weight of cobalt, up to about 1.5% silicon, up to about 0.8% chromium, up to about 0.3% aluminum, up to about 0.3% manganese, up to about 0.03% sulfur, up to about 0.05% nitrogen, the aluminum, manganese, nitrogen and sulfur being selected within the respective ranges stated to provide effective amounts of at least one inoculant of the group consisting of manganese sulfide and aluminum nitride, less than about 0.03% carbon and the balance iron with incidental impurities, hot working the cast melt at a temperature within the range between about 1,250C and the highest possible temperature without causing burning, cold working the hot worked material in two or more operations to finish gauge, at least the last cold working operation effecting a reduction in cross sectional area of between about 50 and about 75%, with an intermediate anneal interposed between said cold working operations, said intermediate anneal being at a temperature within the range between 800C and the Ac, temperature of the composition, decarburize annealing at a temperature within the range between about 760C and about 870C in a hydrogen atmosphere of hydrogen having a dew point in excess of about +4C and box annealing the decarburized finish gauge material at a temperature within the range between about 800C and the Ac, temperature of the alloy, the material exhibiting a preponderance of the grains having a [001] orientation, and a secondary recrystallized microstructure.

Claims

1. A WORKED AND HEAT TREATED ALLOY HAVING A SUBSTANTIALLY FLAT SURFACE AND WHICH ALLOY MEMBER IS SUITABLE FOR USE AS A TRANSFORMER CORE MATERIAL, CONSISTING ESSENTIALLY OF FROM ABOUT 4 TO ABOUT 6% COBALT, UP TO ABOUT 1.5% SILICON, UP TO ABOUT 0.3% ALUMINUM, UP TO ABOUT 0.8% CHROMIUM, UP TO ABOUT 0.3% MANGANESE, UP TO ABOUT 0.03% SULFUR, UP TO ABOUT 0.05% NITROGEN, LESS THAN ABOUT 0.03% CARBON AND THE BALANCE ESSENTIALLY IRON WITH INCIDENTAL IMPURITIES, THE ALLOY HAVING AN ORIENTATION IN WHICH OVER 50% BY VOLUME OF THE GRAINS HAVE A UNIT CUBE ORIENTATION SELECTED RORM THE GROUP CONSISTING OF (110) AND (100) IN WHICH THE SELECTED PLANE IS PARALLEL TO WITHIN 15* OF THE PLANE OF THE SURFACE OF THE ALLOY AND IN WHCH TWO OF THE CUBE EDGES OF THE SELECTED PLANE ARE ALIGNED PARALLEL TO WITHIN 15* OF THE WORKING DIRECTION, THE ALLOY ALSO HAVING A RESISTIVITY IN EXCESS OF 30 MICROOHM-CENTIMETERS.

6. A worked and heat treated alloy having a substantially flat surface and which alloy member is suitable for use as a transformer core material, consisting essentially of from about 4 to about 6% cobalt, from about 1.3 to about 1.5% silicon, up to about 0.3% aluminum, up to about 0.8% chromium, up to about 0.3% manganese, up to about 0.03% sulfur, up to about 0.05% nitrogen, less than about 0.03% carbon and the balance being iron with incidental impurities, the alloy having an orientation in which over 50% by volume of the grains have a unit cube orientation selected from the group consisting of (110) and (100) in which the selected plane is parallel to within 10* of the plane of the surface of the alloy and in which two of the cube edges of the selected plane are aligned parallel to within 10* of the working direction, the alloy having a resistivity in excess of 30 microohm-centimeters.

9. The alloy of claim 6 in which the cobalt content is within the range of between about 4 and about 5%, the total of silicon and aluminum is within the range of between about 1.5 and about 1.6% and the nitrogen content does not exceed 0.005%.

10. A worked and heat treated alloy having a substantially flat surface and which alloy is suitable for use as a transformer core material, consisting essentially of from about 4 to about 6% cobalt, from about 1 to about 1.5% silicon, from about 0.1 to about 0.8% chromium, less than about 0.01% sulfur, less than about 0.03% carbon and the balance beinG iron with incidental impurities, the alloy having an orientation in which over 50% by volume of the grains have a unit cube orientation selected from the group consisting of (110) and (100) in which the selected plane is parallel to within 10* of the plane of the surface of the alloy and in which two of the edges of the selected plane are aligned parallel to within 10* of the working direction, the alloy also having a resistivity of at least 30 microohm-centimeters.

11. The alloy of claim 10 in which the sum of the silicon and chromium content does not exceed about 2%.

13. A worked and heat treated alloy having a substantially flat surface and which alloy is suitable for use as a transformer core material consisting essentially of from about 4 percent to about 6% by weight of cobalt, up to about 1.5% silicon, up to about 0.8% chromium, up to about 0.3% aluminum, up to about 0.3% manganese, up to about 0.03% sulfur, up to about 0.05% nitrogen, the aluminum, manganese, nitrogen and sulfur being selected within the respective ranges stated to provide effective amounts of at least one inoculant of the group consisting of manganese sulfide and aluminum nitride, less than about 0.03% carbon and the balance iron with incidental impurities, the grains of the alloy having an orientation in which over 50% by volume of the grains have a unit cube orientation in which the (110) plane is parallel to within 15* of the plane of the surface of the alloy and in which two of the cube edges of the (110) plane aligned within 15* of the working direction, the alloy being further characterized by a secondary recrystallized microstructure, a resistivity in excess of 30 microohm-centimeters and a saturation induction of at least 21,500 gauss.

18. A worked and heat treated alloy having a substantially flat surface and which alloy is suitable for use as a transformer core material consisting essentially of from about 4 to about 6% cobalt, from about 1.0 to about 1.5% silicon, at least one inoculant selected from the group consisting of manganese sulfide and aluminum nitride, the respective amounts of the components of the inoculants being limited to from about 0.05 to about 0.3% manganese with a corresponding sulfur content of between about 0.01% and about 0.03% where manganese sulfide is the inoculant and between about 0.02% and about 0.3% aluminum with a corresponding nitrogen content of between about 0.005% and about 0.05% nitrogen where aluminum nitride is the inoculant, less than 0.03% carbon and the balance iron with incidental impurities; the alloy having an orientation in which over 50% by volume of the grains have a unit cube orientation in which the (110) plane is parallel to within 10* of the plane of the surface of the alloy and in which two of the cube edges of the (110) plane are aligned parallel to within 10* of the working direction, the alloy being furtHer characterized by a secondary recrystallized microstructure, a resistivity in excess of 30 microohm-centimeters and a saturation induction of at least about 21,500 gauss.

20. A worked and heat treated alloy having a substantially flat surface and which alloy is suitable for use as a transformer core material consisting essentially of from about 4 to about 6% cobalt, up to about 1.5% silicon, up to about 0.8% chromium, up to about 0.3% aluminum, up to about 0.3% manganese, less than 0.01% sulfur, less than about 0.005% nitrogen, less than about 0.03% carbon and the balance iron with incidental impurities, the alloy having an orientation in which at least 50% by volume of the grains have a unit cube orientation in which the (110) plane is parallel to within 15* of the surface of the alloy and in which two of the cube edges of the (110) plane are aligned within 15* of the working direction, the alloy being further characterized by a primary recrystallized microstructure and a resistivity in excess of 30 microohm-centimeters.

24. A worked and heat treated alloy having a substantially flat surface and which alloy is suitable for use as a transformer core material consisting essentially of from about 4 to about 5% cobalt, from about 1 to about 1.5% silicon, up to 0.8% chromium, less than 0.01% sulfur, less than 0.005% nitrogen, less than 0.03% carbon and the balance iron with incidental impurities, the alloy having an orientation in which at least 50% by volume of the grains have a unit cube orientation in which the (110) plane is parallel to within 10* of the surface of the alloy and in which two of the cube edges of the (110) plane are aligned parallel to within 10* of the working direction, the alloy being further characterized by a primary recrystallized microstructure and a resistivity of at least 30 microohm-centimeters.

26. A worked and heat treated alloy having a substantially flat surface and which alloy is suitable for use as a transformer core material consisting essentially of from about 4 to about 6% cobalt, up to about 1.5% silicon, up to about 0.8% chromium, up to about 0.3% aluminum, less than 0.01% sulfur, less than 0.005% nitrogen, less than about 0.03% carbon and the balance iron with incidental impurities, the alloy having an orientation in which over 50% by volume of the grains have a unit cube orientation in which the (100) plane is parallel to within 15* of the surface of the alloy and in which two of the cube edges of the (100) plane are aligned parallel to within 15* of the working direction, the alloy being further characterized by a primary recrystallized microstructure and a resistivity of at least 30 microohm-centimeters.

30. In the process for producing (110) (001) texture in an alloy suitable for use as a transformer core material, the steps comprising, hot working a casting having a composition including less than 0.03% carbon, less than 0.01% sulfur, from about 4% to about 6% cobalt, up to about 1.5% silicon, up to about 0.3% aluminum, up to about 0.8% chromium, less than 0.005% nitrogen and the balance iron with incidental impurities, the hot working of the casting being at a temperature within the range of between about 1,000*C and about 1,100*C, cold working the hot worked material in two or more operations to finish gauge, the last cold working operation effecting a reduction in cross-sectional area of between 50 and 75% with an intermediate anneal interposed between successive cold working operation, said intermediate anneal being at a temperature within the range between about 800*C and the Ac1 temperature of the composition, and thereafter annealing the finish guage material at a temperature within the range between about 800*C and the Ac1 temperature of the composition, the material exhibiting a preponderance of the grains having a (110) (001) orientation, a primary recrystallized microstructure and normal grain growth.

31. The process of claim 30 in which part of the cold working takes place at a temperature between room temperature and about 500*C.

32. The process of claim 30 in which the final annealing is a box anneal for a time period of between 24 and 48 hours in a reducing atmosphere having a dew point of less than about - 40*C.

34. In the process for producing (100) (001) texture in an alloy suitable for use as a transformer core material, the steps comprising casting a melt having a composition including less than 0.03% carbon, less than 0.01% sulfur, from about 4 to about 6% cobalt, up to about 1.5% silicon, up to 0.3% aluminum, up to about 0.8% chromium, less than about 0.005% nitrogen and the balance iron with incidental impurities, hot working the casting at a temperature within the range between about 1,000*C and 1, 100*C, cold working the hot worked material in two or more operations to finish gauge, at least the cold working operation effecting a reduction in cross-sectional area in excess of about 75% with an intermediate anneal interposed between each cold working operation, said intermediate anneal being at a temperature within the range between about 800*C and the Ac1 temperature of the composition, and final annealing the finish gauge material at a temperature within the range between about 800* C and the Ac1 temperature of the composition, the material exhibiting a preponderance of the grains having a (100) (001) orientation, a primary recrystallized microstructure and normal grain growth.

35. The process of claim 34 in which the final annealing is a box anneal for a time period of between 24 and 48 hours in a reducing atmosphere having a dew point of less than about - 40*C.

36. In the process for producing (110) (001) texture in an iron base alloy suitable for use as a transformer core material, the steps comprising, casting a melt having a composition from about 4 to about 6% by weight of cobalt, Up to about 1.5% silicon, up to about 0.8% chromium, up to about 0.3% aluminum, up to about 0.3% manganese, up to about 0.03% sulfur, up to about 0.05% nitrogen, the aluminum, manganese, nitrogen and sulfur being selected within the respective ranges stated to provide effective amounts of at least one inoculant of the group consisting of manganese sulfide and aluminum nitride, less than about 0.03% carbon and the balance iron with incidental impurities, hot working the cast melt at a temperature within the range between about 1,250*C and the highest possible temperature without causing burning, cold working the hot worked material in two or more operations to finish gauge, at least the last cold working operation effecting a reduction in cross sectional area of between about 50 and about 75%, with an intermediate anneal interposed between said cold working operations, said intermediate anneal being at a temperature within the range between 800*C and the Ac1 temperature of the composition, decarburize annealing at a temperature within the range between about 760*C and about 870*C in a hydrogen atmosphere of hydrogen having a dew point in excess of about +4*C and box annealing the decarburized finish gauge material at a temperature within the range between about 800*C and the Ac1 temperature of the alloy, the material exhibiting a preponderance of the grains having a (110) (001) orientation, and a secondary recrystallized microstructure.