DE1558519A1 - Steel with a maximum of 0.08 percent carbon - Google Patents

Description

Dr.-lng. G. Eichenberg ,,,.,

ιν Ί ι υ e I J 4 Doleidorf, the .. .1.4 ....

Dipl.-Ing. H. Sauerland ceciiienoiiee ? &

Patent attorneys

Bank account:

Deutsche Bank AG., Düsseldorf branch Posischeck account: Essen 8734 Telephone number 43 2732

Use in correspondence too nsjr characters: /

International Nickel Limited, Thames House, Millbank,

London, S.W. 1, England

"Steel with a maximum of 0 _t 08 percent carbon"

The invention relates to steels with remarkably great plasticity at high temperatures and good Hot working properties.

Investigations on different alloy systems recently uncovered a new metallurgical phenomenon, which is called "superplasticity". This can be defined as the ability of a material to be an unusual one exhibit great elongation when subjected to tensile stress. An alloy that, in its superplastic state, is a Tensile stress is subjected to a controlled increase in tension, can be two, three or even tenfold stretched to their normal length before breaking.

So far, superplasticity has not been observed in steels and the invention is based on the discovery that in the case of steels with a low carbon content,

0 09 815/0765 original

For the letter of .... 14-.J-UILL 1967 · to ...!. 'Stahl-jni ± ... JlQ Cu; \ _ "13 Ü, .Q8 #. C ". Sheet

Composition which have a two-phase microstructure at room temperature, which consist of austenite or martensite in a ferritic matrix, the plasticity at high temperature can be increased to a remarkable extent by the generation of an extremely fine grain structure in the forged or otherwise machined state. In general, the invention relates to steels of this structure in which the carbon content does not exceed $ 0.08 and the grain structure is so small that the steel is superplastic. In this specification and claims, a steel is referred to as superplastic if it is stressed with a uniformly increasing stress of 0.16 to 0.26 cm / cm of initial length and at a temperature in the range of 870 to 980 ⁰ O, a Has an elongation of at least $ 150. In order to achieve this effect, the grain size of each phase j must be as small as possible, and it should advantageously be such that the free path between the austenite and martensite particles does not exceed 8 microns. Advantageously, however, this path is lower and does not exceed 6 microns. In fact, it is best not to exceed 3 microns.

A group of steels in which the ultrafine microstructure with superplastic properties is advantageous can be achieved by mechanical or thermal treatment are stainless nickel-chromium steels that

009815/0763

have a relatively low content of nickel and a relatively high content of chromium, are ferritic at high temperatures and have a two-phase ferrite-austenite structure at low temperatures above the HS temperature. The invention includes such chromium-nickel steels if they have an ultra-fine duplex microstructure, such that the steel is superplastic, and 18 to 35? 6 chromium, 2 to 12? Nickel, not more than 0.08? Carbon, 0 to 1.5 - / * titanium and 0 to 1> * vanadium, with the total titanium and vanadium content at least four times the carbon content above 0.03> 0, but not more than 1.5? » is further 0 to 1 / ί manganese, 0 to 1 $ silicon, 0 to 3A molybdenum, 0 to 2% cobalt, up to 2.5 C ^ copper, radical ini weseixtlichen iron. To ensure that the steels have a duplex microstructure, the total content of chromium and molybdenum must have the relationship

1.17 (#ii) + 13.3 ^ 5 $ Cr + 5 & I0 <. 5.5 ("SKi) + 11

suffice. The extraordinarily high toughness of these steels, when they are at a controlled speed in temperature area from 870 to 93C ^ "C under increasing voltage gives them the ability to be deformed to a remarkably high degree under the application of little load. In addition, these steels can easily be made by conventional means varä be processed, for example by hot rolling or extrusion at temperatures in this range

■ - ORIGINAL BATHROOM

009815/0763

or even below, using forces comparable to those used for processing ferritic stainless steels are used.

Another feature of the invention is based on the observation that new steels of carefully observed Composition have a remarkable combination of properties within the ranges given above, especially after previous treatment, by means of which an extremely fine-grained duplex ferrite austenite or austenite martensite microstructure generated v / ird. The properties of the new steels persist after such treatment in addition to increased plasticity and V / arm machinability higher temperatures in high strength, malleability and resistance to fatigue and corrosion at ordinary Temperatures.

The new steels thus offer advantages over known types, both austenitic and ferritic stainless steels, all of which have properties that make them only applicable to a limited extent.

Well-known varieties of austenite stainless steel Steels are stiff during hot working, require considerable forces during processing and have to be used during processing often be reheated. In the processed state, they show a relatively low strength in the usual sense as well as low endurance strength

009815/0763 ^ original

kelt, tend to form holes and fail under stress corrosion, especially in chloride solutions. Ferritic stainless steels generally have greater strength than austenitic steels, although they are not particularly are solid, and they have a greater fatigue strength, but are prone to pitting corrosion and also to Stress corrosion under certain external circumstances, for example in bubbling hydrogen sulfide solutions "

The new steels according to the invention contain $ 23 to $ 35 chromium and $ 4.5 to $ 12 nickel. Otherwise are put them together in the manner given above.

The chromium and nickel content in the steels is of great importance. If the chromium content is less than $ 23, the steels are not tough enough. In order to give the steels high resistance to cracking under stress corrosion conditions, the chromium content should exceed $ 24. It is generally not necessary to make the chromium content greater than $ 28 to cool the desired combination of properties, and chromium levels above $ 35 lead to serious commercial disadvantages including poor block surface, formation of oxide foam in air, increased costs and the possibility of embrittlement during heating to hot working temperatures »at least 4? 5 $ nickel must be present is" to provide adequate strength zn -Get ^ and is .with advantage of JfickeX-content at least 5 _r 2 $ _f us the spontaneous occurrence of

To prevent tensite when cooling from elevated temperature to room temperature. The nickel content advantageously exceeds this $ 8 no.

The strength and toughness of steels are determined by the proportions of ferrite and austenite or Martensite affects, and the composition must be as follows Satisfy conditions:

and ° / oCr + "million? 1.17 ($ Ki) + 13.3.

If the nickel content is lower than the first of these two conditions requires, the steel is not sufficiently tough, and if the nickel content is higher than the second condition requires, the steel is not sufficiently strong »

Control of the carbon content is of great importance and the carbon content must not exceed $ 0.08 to ensure adequate toughness at room temperature. Preferably, the carbon content does not exceed $ 0.05 in order to ensure optimum toughness at room temperature, and in order to ensure good hot workability, the carbon content should not exceed $ 0.03. If the carbon content is greater than 0 _; 03 $ _? d &: in must the steel contain titanium or vanadium and the composition must accordingly meet the further condition »?

$ Ti + $ V ^ 4 {$ 0) - 0.03. 009815/0763

. Titanium has an adverse effect on toughness. The titanium cold should therefore, although titanium and vanadium may be present in a total amount of up to 1.57 °, provided the carbon content is $ 0.03 or less, 0.3; ' at the upper carbon limit of $ 0.08, proportionally larger amounts of titanium are permitted with lower carbon contents. Purely general purpose the titanium content does not need to exceed $ 0.7 and is preferably no more than $ 0.3 for each carbon content. The vanadium content need not exceed $ 0.5 and is preferably no more than $ 0.25.

Silicon and manganese have an undesirable effect on the. Toughness, and v / eia 2; i or m »i.r copper present the silicon and manganese content may be 0.4; » or, do not exceed $ 0.3, otherwise the steel no crack formation during hot rolling.

The steel can contain residual amounts of deoxidizing agents and other additives such as magnesium, zirconium, aluminum, - ger, boron and hafnium, the can be added to the melt in quantities of up to 1fi / The Steel can also contain the usual impurities, although the contents of phosphorus, nitrogen and sulfur are so should be kept as low as possible, as is good steelmaking practice. The presence of such residual treatment agent and impurities should by the statement made above that the remainder is essentially iron

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BAD ORiGiNAL

is not to be excluded.

As for impurities, note that niobium is a noxious element, and so on should be excluded as much as possible.

Upon cooling of the inventive composite or made -Siiähle from a temperature at which its structure is essentially ferritic, for example 1200 ⁰ C, to a temperature in the two phase region above the MS temperature balance between austenite and ferrite is produced only slowly, so that when Quenching or normal cooling to such a temperature the structure remains essentially ferritic. Precipitation of austenite is obtained by the fact that the steel excessively exposed to high temperatures in the two phase temperature range, for example, 760 to 1010 ⁰ C and preferably at least 815 ° C, and for a time of 20 to 30 minutes or more, or else by that the steel is exposed to these temperatures and processed at the same time. If the steels are exposed to such temperatures in the range mentioned for a prolonged period, they generally have a structure which contains 20 to 80% austenite, the remainder being essentially entirely composed of ferrite. At low temperatures, the austenite can be completely or substantially decomposed into martensite.

By appropriate treatment, it is possible to develop the two-phase structure in such a way that the austenite

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Particles are ultrafine and the transverse mean free path (hereinafter referred to as path) between the Austenite (or Martensi-t) particles preferably not exceeding 8 microns ο It has already been indicated that the Steel, when in this state, "is unique Has a combination of highly useful properties, including improved plasticity at elevated temperatures, excellent strength "at room temperature, malleability, Toughness, resistance to fatigue and corrosion, and good hot and cold workability. (Indeed the forces required for hot machining of steels are comparable to those required for plastic deformation of ferritic stainless steels are needed, and considerably lower than those used in austenitic stainless steels Steels are necessary. The steels are also readily cold-deformable and age-hardened.

The shorter the shorter, the better the properties the middle free path becomes. Preferably this is not larger than 6 microns and even better not larger than 3 microns "

The small distance between the particles and the ultrafine grain size of the steels according to the invention can can advantageously be produced by a process that combines heat treatment and plastic deformation represents. This procedure is the subject of another

009015/0763

Patent application by the same applicant. It avails itself the well-known fact that a steel that is plastically deformed, recrystallises when it is down to a certain Temperature or above this temperature is heated, the V / ert of this temperature from the composition and to a certain extent also depends on the extent of the plastic deformation. The lowest temperature begins when recrystallization is generally referred to as the recrystallization temperature. In the treatment the steels according to the invention is the precipitation of the Austenite in the plastically deformed steel above the recrystallization temperature causes recrystallization of the ferrite combined with precipitation of the austenite takes place. Generally speaking, the treatment consists of the plastic deformation within the two-phase temperature range of steels that have a ferritic structure in solid Solution on iron and contain austenite, these steels being heated within the two-phase temperature range during or after deformation to To bring about recrystallization of the ferrite and precipitation of the austenite. It was found that the recrystallization of the plastically deformed material ensures the formation of fine grains, while the precipitation of austenite the grain growth is blocked at the precipitation temperature, effects that work together to create and maintain contribute to a fine duplex structure, The duration of the

009815/0763 bad original

heating in the two-phase range, which is necessary for the Precipitating austenite changes with the history of the Material in terms of thermal and deformation technology and is generally between a few minutes and a number of hours.

The treatment can be carried out in various ways _e Thus, after heating of the steel zwedks resolution of a portion of the austenite to form a solid Ferritlösung of steel, starting vun the dissolution temperature, keeping adequately s elin eil cooled .werden to the dissolved austenite in solution su whereupon the steel is cold worked to bring about plastic deformation and then heated again to recrystallize it and precipitate the austenite.

In the case of steels according to the invention that have not previously been machined in the two-phase range, the approach to phase equilibrium is slow since little or no austenite is precipitated, while the steel is cooled after the solution heat treatment, provided that the Cooling rate is not extremely slow _c

The cooling with the solution temperature as the starting temperature can be accompanied by plastic deformation , for example by the fact that the steel is worked, starting at the solution temperature, until a temperature

'009815/0763 ^BAD

temperature in the two-phase range is reached, whereupon the steel continues to be plastically deformed and heated in this area to induce recrystallization and precipitation of austenite.

It will be appreciated that although high temperatures, preferably be ^ of heating are above the ZweiphaBenbereichs, for example 1200 ⁰ G used by steel blocks, before they are pre-stretched for the first time, which blocks should not be re-heated to such temperatures after it, starting from the temperature required for solution annealing, or have been subsequently treated to produce a fine grain structure, as this would result in the precipitated austenite being partially or completely dissolved again and making the ferrite coarser. Generally speaking, the new steels according to the invention should not be reheated ^{to a temperature above 1010 0 O during or after the treatment which follows the cooling step.}

To get the finest microstructure of the steels, the solution annealing should be carried out in such a way that as much as possible of the austenite initially present in the steel much unc. preferably all or substantially all of it is dissolved, since undissolved austenite particles have the tendency to be relatively rough. The Kikrο structure that received becomes when the austenite is dissolved and during recrystallization is excreted again is essentially

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'. BATH

axially rectified, and the properties of the forged Steels are isotropic. The fineness of the structure obtained also depends on the degree of plastic deformation and this should be at least a $ 20 reduction and preferably correspond to a 50% reduction or more in cross-section. Reduction is used here in the sense a reduction in the cross-sectional area, i.e. in the mechanical, not in the metallurgical sense.

It is also advantageous to apply the deformation by cold working. Extremely fine microstructures, for example with a gap between neighboring austenite particles of 3 microns or less, can be achieved by a combination of heating, hot working within the two-phase temperature range, Cross-section reduction in the cold state, reheating and hot working within the Two-phase range can be obtained.

The new steels are preferably produced by melting in a vacuum, because silicon is then unnecessary and manganese for the purpose of deoxidation, and because the contents of carbon, oxygen, nitrogen, hydrogen, Sulfur, phosphorus and other elements that reduce the steel's impact resistance are kept very low can be. But the economically more advantageous ones can also be used Melting in air methods are used to produce steels with excellent properties,

009815/0763

even with carbon levels of $ 0.05 and below, if Titanium or vanadium or both substances are added in order to combine with the carbon.

The drawings are all photomicrographs magnified 750 times in diameter. Figures 1A and 1B illustrate typical duplex ferrite-austenite structures produced in a steel of the present invention, namely Steel No. 2 in Table I, from which the benefit cold working emerges. Fig 2A and _a 2B illustrate duplex ferrite-austenite structure, which have been generated in a different steel, namely steel no. 27, was initially present in which the austenite does not solved. gig. 3A and 3B illustrate duplex ferrite-austenite structures that have been produced in two other steels, namely steels # 43 and # 54. They show the refinement in structure that forms the result of complete dissolution of the austenite.

The steels to which FIGS. 1A and 1B refer were ^{heated as blocks to 1205 °} C. in order to dissolve the austenite so that the steel became essentially completely ferritic. The structure according to FIG. 1A was produced by initial stretching of the block, starting from the temperature of 1205 ^° C., by forging and then hot rolling with an initial temperature of 925 ^° C. in the two-phase range. The steel structure of Fig. 1B was similar

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Manner except that the steel was cold worked between forging and hot rolling. Both Microstructures are extremely fine, with the mean free path in the case of steel being 3.8 microns in the case of steel and 3.8 microns in the case of steel Fig. 1B is 2.4 microns. It can also be seen that the cold machined steel has a distinctly fine microstructure Has.

Fig. 2A shows the structure of a steel in which heating to the initial forging temperature of 12O5 ° C was not sufficient to dissolve the austenite. The Steel was forged down, starting at this temperature, until it was in the two-phase range at 9? -5 ° C, then again heated to 1Ü4O "C and starting at this temperature hot-rolled in the two-phase area and finally annealed for one hour at 925 ° C, i.e. also in the two-phase area. Fig. 2B shows the structure of the same steel after similar treatment, except that the Steel after hot rolling with a slight reduction in cross-section cold worked and annealed at 925 ° 0 for one hour. Although a certain amount due to the cold working Grain refinement has been achieved, the austenite appears in each case almost entirely in the form of reeds from undissolved material primary austenite. None of these structures are in accordance with the invention.

Fig. 5A shows an example of a structure 009815/076 3 BAD ORfGtNAL

which is obtained when a part of the primary austenite is dissolved and precipitated again, the precipitated austenite appearing in the form of islands between the elongated particles of the primary austenite. This structure was created by soaking a steel block for one hour at 1205 ° C, then rolling it out to a heavy plate 25 mm thick, then reheating it to 925 ° C, rolling it down to 16 mm thick and finally at 925 for one hour ° C was annealed. The initial soak at 1205 ° C was insufficient to dissolve all of the austenite. Fig. 3B shows the result of heating a steel of similar composition at 1260 ⁰ C, so that substantially all of the austenite was dissolved before the block to a spell of 8.5 mm thickness by forging, starting at a temperature of 126o C ⁰ , and 7 / arm rolling with intermediate annealing at 925 ° C. The austenite precipitated out during the tempering and annealing. The mean free path of the structure according to FIG. 33 is 6.85 microns. This steel has a structure that is essentially free from elongated austenite particles.

V / hen the steel a very fine-grained two-phase microstructure have, in which the distance zwisehen two particles does not exceed 8 microns, so they are characterized by unusually high plasticity at temperatures of 87O ⁰ C

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BATH

Ms 98O ⁰ C, as can be seen from the fact that an extensibility of 15C $ or more is obtained at a rate of stress increase of 0.16 to 0.26 cm / cm / min, measured in the short-term tensile test, and that it is at these Temperatures only need unusually low forces to cause large deformations. In addition, the steels can easily be processed hot, for example by rolling or extrusion at the same or lower temperatures. In the hot-worked state, they also show unusual combinations of other properties, namely with regard to tensile strength at room temperature (63 to 88 kg / mm); in relation to 0 _t 2fo of the yield strength (40 to 55 kg / mm ² ), in relation to the malleability (25 to 45 $

tion); in relation to toughness (energy up to 13 kgm / cm and more in the notched impact test according to Oharpy) and in relation to fatigue (a durability limit of, for example, 40 to 55 kg / mm in 10 'cycles). Cold working such as rolling or wire drawing is easy to perform and gives tensile strengths up to 245 kg / mm or more for a wire diameter of 0.25 mm and up to 130 kg / mm or more for a 1.2 mm thick sheet . These steels can also be brought to a high hardness by age hardening, about 45 to 50 .Rockwell ¹¹ C "and accordingly to a correspondingly high strength, without any loss of useful ductility.

009815/07 6 3

Examples of the composition of 52 steels according to the invention are in the table below I stated.

Table 1

stole
No. C. 30th Cr Ni 6th Ti miscellaneous 1 0.02 25th 6th 0.6 2 0.02 25th 6.05 0.6 3 0.009 25th .5 5.2 0.59 4th 0.008 25th .6 7.0 0.63 Ul 0.012 29 .2 6.2 0o61 6th 0.011 29 .4 7.2 0.61 7th 0.009 29 .6 8.9 0.62 8th 0.010 25th .4 8.6 0.60 9 0.007 25th .7 6.1 0.56 10 0.008 25th .6 6.1 0.23 11 0.005 35 .5 10 <0.10 12th 0.05 25th 6th 0.62 13th 0.021 25th 6.1 0.6 15th 0.014 25th .4 6.1 <0.01 16 0.02 25th .9 6.0 <C.O1 17th 0.05 25th .5 6.0 0.08 18th 0.046 25th .7 6.0 0.17 19th 0.047 27 .3 6.8. 0.32 20th 0.010 28 .4 7.2 0.57 21 '0.013 29 .0 7.6 0.59 22nd 0.Ό12 25th .8th 6.0 • 0.59 23 0.08 25th .9 5.9 0.16 24 0.07 23 .6 5.2 0.32 25th 0.022 24 .5 5.6 0.57 26th 0.030 0.58

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stole
No. G Cr Ni
t> Ti
Ϊ * miscellaneous
1 ° 27 0.034 26.0 6.1 0.14 28 0.044 25.8 7.1 0.64 29 0.043 25.6 8.1 0.53 30th 0.041 25.4 9.0 0.63 31 Oc 039 26.2 10.2 0.55 32 0.013 24.5 ' 5.7 <0.01 1 mo 33 0.006 24.0 5.6 <0.01 2 mo 34 0.004 23.5 5.7 <0.01 3 mo 35 0.056 26.0 7.05 - 0.13 V 36 0.044 24.8 5.9 0.57 37 0.048 25.4 6.9 ■ 0.59 38 0.049 2513 6.0 0.62 39 0.043 25.4 6.9 0.61 40 0.039 25.6 5e9 O0I7 41 0.043 25.3 7.0 0.15 42 0.048 25.7 6.0 O0I5 43 0.043 25.5 7.0 0.16 44 OcO22 25 ^ 0 6.4C 0.3Ü 45 0.020 25.2 7.20 0.30 46 0.020 25.95 6.20 0.29 47 0.023 26.03 7.15 0.29 48 0.021 25.3 6.2C C c 28 49 0.021 25.2 6.20 0.30 50 0c022 '25.4 6.2C 0.29 51 0.022 25.3 6.1C 0.29 52 0.025 25.3 6.10 0.29

All steels in Table I contained small residues of aluminum (0.02 to 0.06fb). Steels 1 "to 26 and 32 to 35 were made from virgin material in a vacuum.

0 0 9 815/0763 BAD ORIGIMAL

melted and the levels of silicon and manganese were in the range of 0.01 Ms $ 0.04. Steels 27 to 31 were in Air melted. No intended additions of manganese and silicon were made to steel No. 27, but the Steels Nos. 28 to 31 and 35 contained 0.3 to 0.4 percent manganese and 0.45 to 0.6 percent silicon. Die-steels No. 36 to 52 were made Melted in a vacuum and contained 0.1 to 0.35 $ manganese and 0.15 to 0.5% silicon.

Here are a few examples.

Example I.

This example illustrates the remarkable superplastic elongation at elevated temperatures of Steels with an ultra-fine microstructure. Samples of steels of Nos. 1, 2 and 12, which had been hot worked with an initial temperature of 1205 ° C, were put on tension studied at two-phase temperatures, some without further mechanical treatment and others after they were further reduced by 64% through cold working had been. In each case, the sample was held at the test temperature for approximately 20 minutes before testing was started, and precipitation of austenite from the ferrite occurred during this heating. The results are reproduced in Table II, which also shows the increased superplastic elongation caused by cold working the Steels before recrystallization and precipitation of austenite results.

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κ _ζ Initial condition Plate II kg / mm ' D. II M ₁ Expansion speed
age • D. Warm processed
starting at
1205 ⁰ O, then
by Kaltbear
cost around $ 64
reduced 8.3
5.9
3.7
7.4
5o3
3.8 ² * mm cm / cm / min. stole M ₁ Warm processed
starting at
1205 ⁰ O test
Temp. 7.4
4.9
7.6
5o1 300
200
200
433
600
500 19th
19th
19th
19th
19th
19th 0.266
0.266
0.266
0.266
0.266
0.266 No. Warm processed
starting at
1205 ⁰ C ⁰ O 4.1 160
208
304
304 32
32
32
32 0.160
0.160
0.160
0.160 1
1
1
2
2
2 = Tensile strength 870
925
1010
870
925
1010- 460 32 0.16 1
1
2
2 = Elongation 870
925
870
925 12th = Measuring length 1010 example

* A block measuring 10 ": 10 cm made of steel No. 13 was held at 1205; ° 0 for 1 hour and forged into a bar measuring 5 * 7" 5 cm. The forged gtange was heated to 125 ° G and converted into a heavy plate 2.5 cm thick by hot rolling. The sheet metal obtained was ^{heated again to 925 P} Q and in a single DiiPQliliäUf? U. a sheet of 16 mm thick, as a very good plasfic deformation in the phage area

Example III

A block measuring 10 x 10 cm from steel No. 3 was kept at a temperature of 1205 ° C for one hour held and transformed by V / arm forging into a rod 5 x 5 cm in cross-section. The rod was again at 925 ° E heated and reduced by V / arm rolling to a square cross-section with an edge length of 16 mm.

Example IV

Bars of dimensions 5 x 5 cm from steels No. 1 and 2, which are made by V / arm forging blocks of the dimensions 10 x 10 cm that had been held at 1205 ° C for one hour were heated to 1205 ° C and reduced to a square cross-section of 16 mm edge length, then heated again to 925 ° C and converted into a strip 6 mm thick by hot rolling. Eventually part of the tape was cut down to a thickness cold rolled down from 1.2 mm.

The mechanical properties of the in both. games II to IV can be found in Plate III.

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treatment Shape of Plate III K, D. 0 Q 5 Charpy
Notched impact Hot rolled
beginning
at 925 ⁰ C Materials 0 1o 0 kgm / cm stole 16 mm sheet metal
in Querrich
tion SF
0.296
Offset 7th 27 0 61. 5 13.0 No. Hot rolled
beginning
at 925 ⁰ C in longitudinal
direction kg / mm kg / mm 29 68. 13.0 13th 16 mm sheet metal 60.5 74. 29c 77. —— 60.8 72, 3 77.7 84. .4 .9 , 6

Hot rolled 1.2 mm strip 122.1 129.0 starting at 925 ° C, then reduced by 80 <& cold

Hot rolled 1.2 mm strip 124.0 130.0 5.5 - starting with 925 ^J G, then reduced by 80 fi cold

Hot rolled 1.2 mm strip 72.7 83.3 19.0 57.0 starting at 925 ⁰ C, then reduced by 80-1 cold and ^{annealed at 925 0} C for 1/2 hour

Hot rolled 1.2 mm strip 49-9 74.5 27.0 57.0 starting at 925 ⁰ C. then by 80; j cold reduced and 1/2 hour at 925 ⁰ C.

annealed 009815/07 63 BAD ORIGINAL

stole
No. treatment

Porm of the material

S.P. $ 0.2 offset

kg / mm

kg / mm

Charpy impact

kgm / cm

Hot-rolled starting at 925 ⁰ C, then reduced by 80 $ and ^{annealed at 480 0} C for 8 hours

Hot-rolled starting at 925 ⁰ C, then reduced by 80 ^ cold and ^{annealed at 480 0} C for 8 hours

1.2 mm tape 177.0 180.2 7.0 15.5

1.2mm tape 167.1

171.2 6.0 22.5

S.P. = Yield strength

K _z = tensile strength

D = elongation

Q = reduction in cross section

The pestilence of the steels according to the above table was, as far as these steels were hot-rolled, already after simple machining and heat treatment are far greater than those of most common residual steels. aside from that show the results of tests on No. 13 steel, which has an ultra-fine grain structure similar to that of Pig. 1A found that the properties of this material after hot rolling are essentially isotropic.

009815/0763

This panel also illustrates the reaction erfindungsgemaßer steels to age hardening at about 480 ⁰ C.

• The properties of other steels are given in Table, "All of these steels were made into blocks with dimensions of 10 * 10 cm in cross-section, which ^{were heated to 12Ö5 Ö} Ö (except for steel no. 35, which would be heated ^{to 126O 0 O." These} Blocks were then rolled out to 7 * 5 * 7 * 5 µm and then rolled into a 2 * 5 thick coarse sheet, which was followed by an aftertreatment at a temperature "from 98 ^Ö to 1040 ⁰ O." These sheets were heated again to 925 ° 0 and rolled to a thickness of 16 mm in a single pass ! Sons

15S8519

S.F. κ_ Plate IV % Chap'paHteufc S 0 JnI a.g Q «I». 2
kgm / Gm kg / mm ζ
kg / mm ~ 44 L, Ρ « ₂
kgm / cm 9.9 stole 62 65.4 strain 65 9 * 2 13.3 No. 63 73.8 52 11 * 1 7.8 4th 69 75.9 18th 57 8.6 6.9 5 78 84.4 27 58 6 * 9 7.4 6th 77 88.6 20th 73 7.6 26 * 9 7th 40.3 65.9 20th 64 - *. 6.0 8th 54.8 66 _β 8 22nd 65 5.7 8 * 8 9 55.5 65.4 38 67.7 8.6 17.8 10 51.6 70.0 28 66.5 - 15.6 11 53o9 72.7 27 66.5 - 10.4 ' 20 * 56.2 74.7 30th 64 - 11.2 21 * 47.0 71.3 30th 62 8.2 22 * 50α3 73.0 30th - 35 * 33 35 ** 29

* 1 hour, baked for hot, cooled 925 ° C in air ** 1 hr. Hei baked for 815 ⁰ C, cooled in air

S ₄ P, * yield strength

K ₂ = tensile strength

Q = cross-sectional reduction I / "P" = Länggpröheatüük

Qii ". = Cross-test piece ok

OJeile des "Steels Nr. 4 Ms 11 örobhleehes were transformed by hot rolling into rods τοϊϊ 16 knives, the 1> ei 925 ^ö 0 annealed and then cold Walsia reduced to 2.8 tm diameter yu ^ & m _t

009Ö1S / 0783

ORSGUMAL INSPECTED

they were again "annealed at 925 ° C for half an hour" The material then had a forged duplex ferrite austenite microstructure, which contained fine austenite particles in fine distribution. The material was then through Cold drawing into wires with a diameter of 0.5 mm and 0.25 mm transformed without intermediate glow, which corresponds to a 99 # cold reduction. The results of the Tensile tests on parts of the wires of these diameters are given in Table V.

Plate V

tensile strenght tensile strenght stole kg / mm "- 0.5 well kg / now '"- 0.25 mm No. 155 196 4th 174 217 5 144 195 6th 156 209 7th 175 215 "8th 170 215 10 177 226 11

The wires obtained could be of their own Diameter can be wound and looped without breaking. In addition, a considerable reduction in cross-section or necking at break was observed in the tensile test, a sign that an even greater degree of cold working can be expected of the material without difficulty could be.

ORIGINAL BATHROOM 009815/0763

The very fine microstructure of the steels has a

Very high fatigue strength, which corresponds to 10 'cycles in the detection test with rotating rods. Known steels with $ 15 chromium content or $ 25 chromium and $ 20 nickel content or $ 18 chromium and $ 8 nickel content, or finally $ 18 chromium and $ 10 nickel content, had much lower fatigue strengths, both in absolute terms and in relation to their tensile strength . Steels according to the invention which contain less than 23 $ chromium are found to have good resistance to corrosion and to cracking under stress corrosion. For example showed the steels Nos. 2, 4, 5 and 11, after they were hot rolled with a starting temperature of 925 ⁰ C, in the form of tone U-bend samples no cracking after they have been placed in a boiling aqueous solution for 30 days were 42 wt. $ magnesium chloride contained nor, after they were long, placed in an aqueous solution with 0.5 $ 3.5 $ acetic acid content and salt content, saturated with hydrogen sulfide at 3O ⁰ C 45 days. Steels No. 1 and 2 showed no cracks when they were partially immersed in a 20% saline solution at 82 ^° C. for 28 days. Ordinary stainless steel containing $ 18 chromium and $ 10 nickel fails the latter test after just a few days.

Heavy plates made from steels No. 13 and 27, the

009815/0763

were produced by hot rolling with a starting temperature of 12O5 ° O and partial annealing at 925 ⁰ O as well as partial hot rolling at an initial temperature Yon 925 ⁰ O, were able to satisfactory results when using coated with flux electrode arc welded to, with a mating Milldraht using either of the two methods that work with metal-inert gas or with tungsten-inert gas.

The effects of a change in the contents of nickel, chromium and titanium in the new steels result from the test results given in Plate VI are. This table also illustrates the importance of all or substantial initial dissolution entire austenite to the finest possible microstructure to be achieved if the optimum of the properties is to be achieved. Blocks from each of the steels were made for 1 hour warmed through for a long time at 1205 ° C and rolled out with this temperature as the starting temperature to heavy plates of 25 now thickness, which is heated again to 925 ° 0 and in one pass were reduced to 16 mm thick sheet metal.

The tests were carried out on samples that consisted of lormlings which were cut from this sheet were, namely with annealing for one hour at 925 ° 0 and cooling in air. The last column of the board shows the volume percentage of austenite in the annealed Pieces made from steel nos. 56 to 47.

009815/0783

JO

Plate VI

stole
No.

Tensile properties
0.296 SF

kg / mm '

CKP There. in the case of austenite

Energy _1Q 7 _cycle content

ρ ρ

kgm / cin kg / mm $

36 51.5 67.6 28. 0 65.0 8.5 43.9 44 37 47.6 68.1 34. 0 67.0 10.4 42.5 48 38 52.6 68.3 30th 0 65.5 6.2 41.0 40 39 51.5 69.9 31. 0 66.0 12.3 45.4 44 40 48.9 68.9 38. 0 66.0 11.2 46.5 49 41 * 47.5 69.6 35. 0 71.0 12.3 45.2 55 42 50.8 71.0 32. 0 60.5 9.2 44.0 38 43 46.1 70.0 37. 0 67.5 11.3 45.5 53 44 50.3 68.1 33. 0 72.5 8.9 44.2 40 45 41.8 68.0 39. 0 70.5 15.7 42.5 45 46 52.2 69.0 26th 0 67.5 8.2 41.4 31 1-7 49.8 69.7 32. 0 69.5 12.5 41.8 53 48 48.9 68.1 31. 0 67.0 9.1 44.9 - 49 50.8 69.0 28. 0 66.0 11.1 43.2 50 49.1 68.3 35. 0 71.5 11.4 42.7 - 51 50.4 69.2 31. 0 68.0 9.7 41.5 - 52 49.6 68.3 31. 0 76.0 8.0 44.4 - S.] ?. s yield strength = Tensile strength De. = Elongation Eg *. CKP = Constriction β Charpy impact test There. = Endurance strength

A comparison of the results obtained with steels No. 36 to 39 with the results of.

009815/0763

searching with steels no. 40 to 43 shows that the higher one Titanium content of the first group has a tendency to impact resistance decrease and increase the yield strength, and that this effect of titanium by increasing it the nickel content can be countered. A comparison of the properties obtained with steels No. 44 to 47 "shows that higher yield strengths and lower impact strengths with higher chromium and nickel contents were achieved. If the yield strength values of steels 56 to 44, 46 and 47 are plotted against their austenite content Steels, the result is a band of 4.9 kg / mm width in the tensile strength and 17 vol.? » Width in austenite content in relation to the ratio of yield strength to austenite content. The yield strength of the steel Ur. 45 was below this band. The microstructure of this tape was found to be similar to that of Pig. 2A similar where the austenite occurred in the pona of elongated reeds. This was an indication that the austenite had not been sufficiently dissolved during the heating at 1205 ° C. The austenite was found in steels nos. 36 to 39, 44 and 46 was in precipitated porm, and that in Steels Nos. 40 to 43 and 47 was partially unsolved and partially eliminated. All of these steels had structures considerably finer than that of steel No. 45 «Die Structure of No. 43 steel is in Pig. 3A reproduced

0 0 9815/0 763

Steels # 48, 52, and 49 contained $ 0.006 "or $ 0.006 and $ 0.011 phosphorus and steels # 50, 51 and 52 corresponding to $ 0.0076 ", $ 0.011 and $ 0.0095, respectively. The results obtained with these steels show that these amounts of sulfur and phosphorus have their properties not adversely affected.

To give examples of the properties achieved when a preferred steel composition was made on a larger scale, and to see the effects To illustrate various process conditions, melts of 545 kg with a nominal composition were made from $ 6.5 nickel, $ 26 chromium, $ 0.2 titanium, up to C, $ 05 carbon, the remainder being made of iron, with the top Impurity limits were nominally 0.5 $ silicon, C, 5 $ manganese, 0.025 $ phosphorus, and 0.025 $ sulfur. the Manufactured in air in an induction furnace. The melts were composed according to the table below, the remainder in each case consisted of iron.

stole
No. 0 C. C. Mn
$ 0 Si
$ Cr
$ 6th Ni
$ 0 Ti
$ 0 Al
$ 0 P.
$ 4th 0 S.
$ 53 0 .022 0 .48 0 .65 25.5 6th .05 0 .23 0 .012 0 .01 1 0 .003 54 .022 .33 .58 26.9 .1 .24 .017 .01 .012

Steel # 53 contained 73 millionths of oxygen, 2.5 millionths of hydrogen and 125 millionths of nitrogen and steel # 54 contained 198 millionths of oxygen,

009815/0763

4.4 millionths of hydrogen and 189 millionths of nitrogen,

The block from Stan! No. 52 was heated to 1175 ° 0, reduced to 150 ^# .150 ium dimensions in cross section by forging, ^{heated again to 126Q 0} Q, rolled down to a cross section of 100 9 25 mm, ^{heated again to 925 0} O and on a cross section reduced from 100 to 16 mm by rolling. After part of the 16 mm thick sheet ^{had been annealed at ° .25 Q} 0, it had the following properties:

Yield strength in the transverse direction with

O ₁ 2 $ displacement 48.5 kg / mm ²

Tensile strength 70.3 kg / mm ²

strain

Cross-sonic reduction 68 $ Impact strength (CVN) 11.6 kgm / cm ^{2 Endurance strength in torsion}

7 P

rod test (10 'cycles) 43.0 kg / mm.

Another part of the sheet was ^{annealed for 30 minutes at 1230 0} O and quenched in water when it had a coarse-grained, consistently ferritiseiie structure. In this condition, its strength was only 63.6 kg / mm and its endurance strength was between 28 and 32 kg / mm, i.e. less than half the tensile strength.

Another part of the 16 mm thick sheet was annealed for 1 hour at 925 ° 0, cooled in air and thoroughly Cold working subjected to a thickness reduction of $ 80 »

■ 009016/0763

Parts of the sheet thus obtained were again heated to 925 ° C. for 1 hour and further cold worked to reduce its thickness by $ 10 to $ 40. The properties all of these cold rolled materials after the various heat treatments are given in Table VII.

1 Plate VII LK LK LK LK O.25 & S.F. ^K z ₂ D. 1 LK LK ^LK IK kg / mm " kg / mm (%) reduction 1 condition SC + 16 hours / 480 ° C LK 4- 16 hours / 480 ° C SC + 16 hours / 480 ° C SC +16 hours / 480 ° C 68.8 79.0 15.0 ₀ 4 Hrs / 480 ° C Hr / 480 ° G Hr / 480 ° G Hrs / 480 ° C 47.2 68.3 31.0 10 Cold rolled Cold rolled Cold rolled 48.2 68.3 34.0 1 Cold rolled. Hrs / 870 ^Q C Hrs / 870 ° C Hrs / 870 ° G 72.7 94.6 24.0 1 Hours / 87Q ^Ü C Hrs / 925 ° C Hrs / 925 ° G Hrs / 925 ° G 95-6 107.0 16.0 1 Hrs / 925 ° C Hrs / 925 ° G Hrs / 925 ° C Hrs / 925 ° E 84.0 91o4 11.0 Hrs / 925 ° C 16 · 16 16 45.4 66.9 36.0 20th 16 44.7 66.0 35.0 1 67.4 94.6 25.0 1 113.0 120.0 13.0 1 95.5 101.0 7.0 45.8 66.6 35.0 40 44.4 64.8 33.0 1 71.3 94.3 25.0 1 127.0 133oO 10.0 1 112.0 125.0 6.0 46.6 68.5 36.0 80 47.8 67.4 35.0 66.7 94.6 24.0 146.0 156.0 4.0

LK = cooled in air
S, F. β yield strength
K = tensile strength
D = elongation

009815/0763

SS

The JIock steel no. 54 was heated for 1 hour at 126o ⁰ G and by the method steps, the ILR for steel. ' 53 had been used, reduced to a thickness of 16 mm, and part of the sheet obtained was further rolled down onto a 7.6 stance strip. The properties of these products after they have been annealed at different temperatures, cooled in air (LrI) and quenched in water (WA) result in I ¹ Uf! of the na cn granting evil VIII.

Plate VIII

Glow te m- ^ temperature rc)

Hot-rolled 16 mm sheet

K.

Room temperature Sehla «-: firmness

615 / LK 925 / LK 1010 / LK 1C40 / LK

815 / LK S15 / WK 925 / LK 925 / WA

51.9

43.9 5C.6

70.5 09.7 68.1 66.8

63.-Ü

29: 58
29.0 - 62

.5 .0

11.2 11.5

.10.3 6.9

Hot-rolled 7 _t 6 mm strip

57.3

51.9-

53.0

-9.7

76.2 70.7

7; 2.6-

68.8

33.0

1 f—.-Ν "/"" ■»

.0 .0

35.0 36.0

58

LK S = cooled in air

WK = cooled in water

¥ A s = quenched in water

S.F. s = yield strength

K = tensile strength

j) ^z = elongation

Eg ■ = containment

OVN = Charpy impact test

009815/0763

ORIGINAL

The average distance between the austenite particles in the hot-rolled 16 mm thick strip 10.4 microns, while in the 7> 6 now thick band they are 6.85 microns fraud. The microstructure is shown in Fig. 3B.

Steel No. 54 in the form of a hot-rolled bar 16 mm in diameter, which had been annealed at 925 ° C, had an impact strength (Charpy notched impact test) at room temperature of 41.5 kgm / cm and at -75 ° C of 26.8 kgm / cm.

The importance of controlling the composition of the new steels according to the invention within the above indicated ranges is illustrated by the results of tests on 15 steels of other compositions, which are reproduced in Table IX.

009815/0763

apples.

Steel O Or 3Ji 9? I 'Al

A 0 * 084 25 * 7 6 * 1 <0.01 0.055

B 0 * 14 25 * 7 6 * 0 <0 * 01 0 * 036

Ö 0 * 078 25 * 6 5 * 8 0 * 65 0

D. Ö * 008 18th 5 2 6th O* 6th 0 * 041 B. 0 «ΟΊΟ 18th G 3 O ₄ 6th 0 * 034 i ¹ 0 * O14 18th 4th 4th O* 6th 0 * 036 & Ö _O ots 18th 6th 5 8th Oo 6th 0 * 05 H 0 * oi £ ig * 3 * O* 6th 0.03 Ϊ Ö 6Ö16 20 * 4th Oo 58 0 * 03 j 0 «030 21 4 * O* 62 0 * 03 It 0 «019 22s 4th O* 6th 0 * 03

L 0 * 007 1% 4 0 * 6 0 * 03

MO ₆ 12 25 6 0 * 68 0 * 03

AA 0 * 046 25.7 6.0 40 * 01 0 * 034

BB 0 * 056 2.5 * 5 6 * 1 0.04 0 * 037

All of these steels would shut flexed to örotJlileöh of 16 mm thickness, namely dtiröh a method ahnliöh demjenigeni the to JJrzeuguilg of the substances in one of the front * - been applied reciprocating ¹ Safeln was * The are obtained in terms of "tensile strength and SöhlagfestigJcöit in Safe! X against »

Oödet S / 0763

! Üafel

Sf
$ 0.2 offset
(kg / mm ² ) (kg / mm ² ) Yield strength D. Eg Impact test
■ (GVN) kgm / cm ²
lengthways across stole
No. 45.0 67.5 tensile strenght 34 60 10.7 A. 47.1 69.6 35 58 7.5 B. 52.0 68.9 27 58 3.7 O 40.8 48.5 33 74 1.2 1.4 D. 45.7 53.4 30th 73 1.9, 2.3 E. 61 * 9 71 * 7 22nd 70 1.9 2.6 ϊ ¹ Around· _-M -. -, 2.6 H ■ ACM -. 2.3 I. - - - 2 * 9 J - - 3.1, E. 57.0 60.5 16 37 2.8 4.2 I. S.F. = TT

D = elongation

Eg = constriction

CVi = Charpy notch impact test

Material from steels D, E, 1 and L was drawn in the same manner as has now been described in connection with iafel V to produce wires of 0.5 and 0.2.5 thickness. The results of the tensile tests on these wires are reproduced in! Table ti. - ^ a "

009815/0763

Plate XI

- ■ '- ■■ "■ Tensile strength Tensile strength

2 2

Steel kg / mm - 0.5 mm kg / mm - 0.25 mm

No. diameter diameter

D 108 142

E - - 159. 188

F - 159 ■ 210

L 133 184 -

All steels according to Table IX with the exception of steels A and B have low impact strengths. The steels A and B showed serious cannon cracks "during hot rolling. The steels AA and BB also showed crack formation. Lie steels H, I and K fell - after 17 hours and - steels J and L - after only 4 hours Stress corrosion test in boiling, aqueous magnesium chloride solution After 4-0 hours these steels also failed in a stress corrosion test, which was carried out in an aqueous solution made from 0.5 # acetic acid and 3.5% sodium chloride saturated with Y. / asserstoffsulfid at 30 ⁰ C was. steel M, O, $ 12 carbon and C containing 68'- titanium, showed cracks after 2 hours in a test conducted in magnesium chloride stress corrosion test and after 17 hours in a test in hydrogen sulfide. the low Impact strength of 3.1 kgm / cm ² of steel K containing 22 # chromium and 4.3 ^ nickel should be compared with the much higher one

009815/076 3 i-; ■ -..-. .

- '■' ^v BAD "ORIGINAL

Impact strength of 6.0 kgm / cm of the No. 25 steel containing $ 23 chromium and $ 5 »2 nickel and that of 8.5 kgm / cm ^{2 of} the No. 26 steel containing $ 24 chromium and 5.6 $ Contained nickel when these steels were tested under the same conditions.

It should be noted that steels D and L, although having compositions outside the scope of the novel steels of the invention, nonetheless respond to the special treatment described herein to produce an ultra-fine microstructure, and in that condition are superplastic. Thus steel showed D in the state that it was in after heat treatment beginning at 925 C and again heated to 925 ⁰ C for a period of 20 minutes before the test, a superplastic elongation of 210 $, when at an increase speed of the voltage was stretched at 0.16 cm / cm / min.

It is essential that the new steels according to the invention contain no lliob because this element has the properties the steels are significantly impaired. Thus, in the case of an alloy, the composition was similar to that Steel No. 4 but containing $ 0.6 niobium in place of titanium as described in that described in connection with Table V. Wise treated had an impact strength of only 5.35 to 3.80 kgm / cm for samples that were in the longitudinal direction

009815/0763

or transverse direction were investigated * Mob also affects the properties of material that is subjected to severe cold working has been subjected, as is evident from the fact that wire made from this steel in the same way has been drawn as if from steel Fr »4> a tensile strength

2

of only 162 kg / mm at 0.5 mm! diameter and 183 kg / mm at 0.55 min diameter showed, whereby the elongation was negligible was »

The good machinability both in the hot and in the cold state of the new steels according to the invention enable them to be readily used in the manufacture of products of all common shapes to use, including pipe, sheet metal, land, plate, rods, rods, wire and extruded products, there are no complicated and expensive intermediate steps the heat treatment necessary for good mechanisehe Properties to ensure * The remarkable combination of properties of the steels, As explained above and allow their relatively low cost it, as structural elements in objects such as covered garbage wagons, oil drenchers, containers for things to be transported Good, chemical devices, box trailers, light masts, road bridges, load-bearing elements in buildings, window center crosses, Railroad cars and locomotives, equipment for certain oil wells including pipes for oil wells and fishing ropes for the recovery of drilling

0098 15/0763

tools and finally for wire ropes for use in Seev / water.

009815/0763

Claims (1)

International Nickel Limited ,. Thames House, Millbank, London, S. V /. 1, England Claims; 1. Steel with a carbon content of not more than $ 0.08, characterized by a fine-grained micro-structure of austenite and martensite in a ferrite matrix, in which the transverse mean free path between the particles of austenite or cardensite is so short, aa: i eggs if steel is set to "with an increase in speed of 0.16 to 0.26 cm / cra / min in a temperature range of 925 ° to 9αθ '""3 under tension, amounts to its elongation under tensile stress at least Aö'Cp. 2. Steel according to claim 1, characterized marked t that the transverse mean free path does not exceed 6 microns. 3. Steel according to claim 2, characterized in that the transverse central free 7 / egg length does not exceed 3 microns. 4. Steel according to one of claims 1 to 3, characterized marked as $ 18 to $ 35 chrome, 2 to 12? Oil liickel, not more than · C, 35fi carbon, 3 to 0098 1 B / 07 6 3 1.5-7 = titanium, 0 to 1 $ manganese, 0 to 1 $ silicon, 0 to 3 $ Contains molybdenum, $ 0 to $ 2 cobalt and $ 0 to $ 2.5 copper, the remainder consisting essentially of iron, with the proviso that when the copper content is $ 2 or more, the manganese content does not exceed $ 0.3 and the silicon content does not exceed $ 0.4, and that the following conditions are fulfilled: * #Di ? 4 (/ cC - 0.03), 1.17 CfSNi) + 13.3 4 $ Cr + / OMo 4 3.5 (7 ¹ SIi) + 11. 5. Steel according to claim 4, characterized in that part or all of the titanium Titanium is replaced by up to 1 $ vanadium, provided that the following conditions are met: 1.5> $ Ti + $ V ^ 4 (76c - C, 03). 6. Process for producing a steel with a fine-grained microstructure according to claim 4, characterized that the steel is plastically deformed within the range of the two-phase temperature, whereby it in solid solution has a ferritic structure that contains precipitable austenite and that the steel inside the two-phase temperature range during or after deformation is heated to bring about recrystallization of the ferrite without precipitation of the austenite. 7. The method according to claim 6, characterized 009 ^ 15/0763 draws that the solid solution of ferrite is solution heat treatment of the steel to dissolve almost all of it Austenite is produced. Method according to claim 6 or 7 »characterized that the plastic deformation is carried out so far that the cross-sectional area around at least $ 50 is reduced. ο Method according to one of claims 6 "to 8, characterized characterized in that the plastic deformation is combined with cold deformation. 10. The method according to any one of claims 6 to 8, characterized characterized in that the steel is used to dissolve at least a portion of the austenite and form a solid The solution of ferrite is heated, then cooled sufficiently quickly to keep the dissolved austenite in solution, then cold worked and finally heated again to recrystallize and precipitate the austenite bring about. 11. The method according to any one of claims 6 to 8, characterized g e k e η η ζ e i without t that the "steel heats up so much is that at least a portion of the austenite is dissolved to form a solid solution of ferrite that the Steel on this, based on the solution annealing . applied temperature, except for a temperature in the two-phase 009815/0763 Temperature range down hot worked and then plastic is deformed in the two-phase temperature range without any heating in the sin-phase perit region takes place in order to thereby bring about recrystallization and precipitation of the austenite. 12. Steel, which can be given a fine-grained microstructure through treatment, the austenite in a ferritic base mass and 23 to 35; » Chromium, 4.5 to 12> 1 nickel, not more than 0.08 $ carbon, 0 to 1.5 ^ titanium, G to Ma Hangan, G to 1 $ silicon, 0 to 3 $ molybdenum, 0 to 2 $ cobalt and contains 0 to 2.5 copper, the remainder being essentially entirely iron, with the proviso that when the copper content is 2 or more, the manganese content does not exceed 0.35 ° and the silicon content 0.4 does not exceed $ and that the following conditions are met: >, 4 (; & - 0.03),
1.17 (f «Ni) + 13.3 ^ #Cr + jöio ^. 3.5 (pKi) + 11. 13. Steel according to claim 12, characterized in that the kickel content is 5.2 to 6 #. 14. Steel according to claim 12 or 13, characterized in that the chromium content is 24 to 28 amounts to. 15. Steel according to one of claims 12 to 14, characterized 009815/0763 1553519 HJ ge ken η .ζ e ic h n e t that the carbon content 0,, Q5. # Does not exceed. 16. Steel according to claim 15 _f, characterized in that the carbon content does not exceed $ 0.03. _; . . 17 · Steel according to one of claims 12 to 16, characterized marked that the titanium content does not exceed $ 0.3. 18. Steel according to one of claims 12 to 17, characterized in that the titanium egg is replaced by up to Vp vanadium, with the proviso that the following condition is met: + -cV ? 4 (^ C - C, C3). 19. Steel according to claim 18, characterized in that that the yanadium content does not exceed 0.25 ". 20. Steel according to claim 12, since you rc hgeke η η -ζ.e ich η et, da3 its composition is essentially that of the one specified in the description, with 1st. 1 to 34 designated steels. 21. Steel according to claim 12, characterized in that g e k e η η, that he essentially made up to BAP-ORIGifoAL 009815/0 763 m letter from JUk * ÄJmLA9 & L · an! ^f .Siώl: .... fflii ^ .... M.Q3aaiί.§SS ... D .. ^ ΏB ^ ..... Ü.! .'........... Sheet 4JL $ 0.05 carbon, $ 6.5 Iiekel, 26% chromium, $ 0.2 titanium, remainder apart from impurities iron, "consists. 22. The application of the method according to one of claims 6 "to 11 to a steel according to claim 18 or 19. COPY ORlGSNAL INSPECTED 009 815/0763