US2035197A - Processes for producing wrought iron - Google Patents

Description

Patented Mar. 24, 1936 llNlTEDSTATES PATENT OFFICE PROCESSES FOR PRODUCING WROUGHT IRON John B. Schlossberg, Terre Haute, Ind., and Lester E. Frazier, deceased, late of Stratford, Conn, by Gayle G. Frazier, administratrix, Stratford, Conn, assignors to Highland Iron & Steel Company, a corporation of Indiana No Drawing. Application June 1, 1933, Serial No. 673,854

3 Claims. (01. 75-47) The invention relates 'to wrought iron and processes of producing it, more particularly from ferrous scrap as distinguished from pig iron.

The principal object is to produce from ferrous scrap, such as breakage steel scrap, car wheels, stove plate, machinery castings, and the like, qualities of wrought iron that will possess the properties and characteristics called for by the trade in general, and through the selection of certain of the above named ferrous scraps, by the several specifications of the American Society for Testing Materials and the American Railroad Association.

The object of using the scrap as raw material is, of course, to reduce the cost of production of the final product, since scrap is obtainable generally at a considerably lower figure than is pig iron. 7

Another object is to obtain as high a recovery of finished wrought iron as is possible from a given quantity of raw materials.

Subordinate objects are the production of wrought iron from the various forms of scrap above-mentioned or mixture of two or more of them as may be desired; the production of prod-f ucts that will be substantially free from hot shortness or as it is sometimes called red shortness; the production of products that will be substantially free from cold shortness; a reduction in puddling time from that required for the puddling of pig iron; proper dosification and treatment of raw material in its several stages prior to introducing into the puddling furnace; the proper selection of a puddling agent for producing a product having the characteristics above-mentioned; and, in general, proper treatment of the material from the commencement of the operation through to the production of rods, sheets, and other shapes.

An object that is subordinate although very important in the processes is the maintenance of the sulphur content at a sufiiciently low value to avoid the deleterious results which would accrue from its presence and the proper maintenance of the carbon content to produce the most efiectual high boil and graining in the puddling furnace.

In carrying out the processes, we may use as raw material breakage scrap, steel scrap, car wheels, machinery cast scrap, stove plate, and the like, or the combination of two or more of them.

As a specific example of one suitable process.

particularly adapted to the manufacture, of sheets, shapes, bars, etc., or such items where Breakage scrap About 480 lbs.=12 parts Steel scrap; About 400 lbs.=10 parts Car wheels About 120 lbs.= 3 parts Into .a cupola furnace of a capacity for handling a charge of the above weight, the mixture is charged together with: f

About 2 /2 lbs. of ferro-manganese.

About lbs. of limestone. I

- About 113 lbs. of coke.

About 5 lbs. of soda ash or its equivalent.

When the phosphorus content of the charge is lower than that that will be required in'the finished iron, phosphorus should be introduced in the form of ferro-phosphorus or other phosphorus bearing combination as hereinafter described.

The furnace is operated in the usual way. It is to be understood, of course, that the proportions of raw material and dosifying agents given are not critical and may be varied through a range that will result in a molten metal for charging into the. puddling, furnacehaving the. desired properties forsatisfactory puddling.

The average analysis. of the raw. material when made up of breakage scrap, steel scrap, and car wheels, as above setwforth, is as follows:

' Per cent Carbon About 2.25

Manganese Under 1.00 Silicon Under 1.00 Phosphqrus Under .80 Sulphur .Under .07 Iron and misc Balance As to the quantity of phosphorus, it is sufficient to say that'it is to be so calculated that, when the molten metal is puddled, there will be a minimum offive per cent (5%) of phosphoric acid (P205) in the slag figured on the basis of two and onehalf per cent (2 of slag by weight in the iron. With raw materials selected for their phosphorus content, the introduction of ferro-phosphorus or other phosphorus bearing combination, such as. calcium phosphate, may be dispensed with but this would not be true with raw materials select-ed at random and, therefore, in practice we find that the additions of phosphorus to the melting furnace charges in the form of ferro-phosphorus, calcium phosphate or other phosphorus bearing combinations is highly; desirable and very much simplifies the problem of selection of raw material.

There is, it may be mentioned, one form of scrap, namely, so-called stove plate, the phosphorus content of which is sufficiently high to avoid the necessity of dosifying with phosphorus, but, in practice, stove plate is obtainable only in very thin sections which results in great waste during the melting. If used in sufiicient quantity, however, without regard to excessive waste, the dosing with ferro-phosphorus or calcium phosphate or other phosphorus bearing combinations may be dispensed with.

Ferro-manganese is added to overcome severe oxidation of the charge due to the great amount of iron oxide present in scrap of the character above-mentioned. In fact, it is found that, in general, any scrap mixture for puddling purposes. is benefited by the addition of ferro-manganese, since it performs the very important function of keeping down the sulphur content through the formation of manganese sulphide (MnS) which goes into the slag.

The soda ash, for which caustic soda or socalled Purite may be substituted, serves to keep down the sulphur content, and we find that, when used in the quantities above-mentioned, the sulphur content of the metal from the cupola is kept at a point not in excess of .160%.

The limestone is added preferably in sizes of from 1" to 1 mesh to assist fluxing. Of course, any other form of lime could be used, such, for instance, as oyster or clam shells.

Before each tap from the cupola approximately one ounce'of aluminum is placed in the spout, the object of which is to further deoxidize the metal which results from the reaction in the cupola metal.

The molten metal is preferably tapped from the cupola into a large receiving ladle with a capacity of several puddling furnace charges, and, if the process above described is carried out will, as it leaves the spout, have an analysis approximately as follows:

Percent Carbon Under 3.00 Manganese Under .30 Silicon Under .35 Phosphorus Under .190 Sulphur Under .160 Iron and misc Balance In a specific instance, the following analysis was obtained:

. Percent Carbon 2.83

Manganese .105 Silicon .14

Phosphorus .186 Sulphur .148 Iron and misc Balance As a matter of fact it is in practice very dimcult to procure breakage scrap wholly free, "r in copper, and experience shows that there wxl usually be, in addition to the above, a copper content of something like 0.30%.

' The metal in the receiving ladle is treated for further desulphurization by the addition of soda ash, caustic soda or Purite 'or the like. It is preferable to cover the top of the molten metal in the receiving ladle with carbon, which may be in the form of charcoal, in sufficient quantity to prevent atmospheric oxidation and too rapid cooling. The charcoal further adds some carbon to the metal which tends tofurther intensify the high boil in the puddling furnace. We find that it is preferable that no withdrawals be made from the receiving ladle until after three taps from the cupola are contained therein and, further, that preferably no withdrawals are made after any subsequent tap from the cupola for at least six minutes or thereabouts thereafter. These precautions insure proper reactions with the soda ash, caustic soda or Purite or the like, as the case may be.

The analysis of the molten metal in the receiving ladle, after the dosification and other treatment above described, is as follows:

Percent Carbon Under 3.00 Manganese Under .30 Silicon 1 Under .35 Phosphorus Under .200 Sulphur Under .150 Iron and misc Balance In a specific instance the following analysis was obtained:

Percent Carbon 2.90 Manganese .115 Silicon .107 Phosphorus .196 Sulphur 138 From the receiving ladle the metal is drawn into acharging ladle capable of holding sufficient metal for a charge to the puddling furnace, which in the case of the instance now being described, is about 700 pounds.

It is preferred that the puddling process be carried out in a furnace of the so-called Ely type, such as is shown and described in United States patent to Ely No. 1,284,880. The puddling agent used consists, for a 700 lb. charge, of about 200 lbs. of iron ore and granulated furnace cinder in the proportions of about 50% each.

With a charge of the above character, the puddling time is very much reduced consuming not more than twenty minutes from the time of the introduction of the charge to the time of removal of the ball. This favorable result is due to the short period of the low boil which, in turn, is due to the small quantity of manganese and silicon of] the puddling furnace charge. This means that the high boil commences very shortly after the introduction of the charge-as a matter of fact, usually less than three minutes-the graining and agglomeration of the grains take place, and the ball is removed all within approximately the time above-mentioned.

T e iron ore constituting one of the components of the puddling agent is selected with a View to a high content of F8203, which, together with the substantial quantity of FeO also present in iron ore, releases oxygen for the oxidizing of manganese, silicon, carbon, sulphur, and phosphorus, and adds some iron silicate to the slag. The granulated furnace cinder which is selected with a View to a silica content of 22% to 26% free from undesirable elements, particularly magnesium oxide, and calcium oxide is also high in iron oxide (FeO) The slag composition contains therefore from about 12% to 20% of silica, and both the ingredients should be as free from copper as possible in order to avoid red shortness. It is found that while slag with less than 12% of silica causes cold shortness, over 20% of silica makes the slag too fluid, the result of which is Percent Carbon Under 0.15 Manganese Under .06 Silicon Under .30 Phosphorus Under .150 Sulphur Under .025 Iron and misc Balance In a specific instance the following analysis was obtained:

Percent Carbon 0.10 Manganese .035 Silicon .225 Phosphorus a .135 Sulphur .015

and a 1" round bar, single worked, made from muck pile, has the approximate analysis of:

Percent Carbon Under 0.15 Manganese Under .06 Silicon Under .30 Phosphorus Under .150 Sulphur Under .025 Iron and misc Balance In a specific instance the following analysis was obtained:

Percent Carbon .08 Manganese .035

Silicon .183 Phosphorus .115

Sulphur .015

Slag and Oxide 3.59 by weight Iron and misc -1 Balance A typical physical test on a 1" round bar from this procedure is as follows:

Tensile strength 48,750 lbs. per sq. in.

Elastic limit 34,950 lbs. per sq. in.

Percent elongation in 8 in 34% Reduction of area 44.4%

Cold bend Flat on itself in one direction Hot bend Flat on itself in two directions Nick bend Showed remarkably long fibres Another procedure which produces material particularly suitable for meeting general A. S. T. M. and American Railroad Association specifications involves the use of material consisting wholly of cast iron scrap; for example, the following:

, Pounds Carwheels 500 Machinery cast scrap 300 Stove plate 200 The analysis of such a mixture would be as follows:

Percent Carbon Under. 3.50 Manganese Under 1.00 Silicon Under 1.50 Phosphorus About 1.00 Sulphur About .10 Iron and misc Balance This mixture is put through the cupola together with about 18% ferro-phosphorus 33 lbs., ferro-manganese about 2 /2 lbs., coke about 113 lbs., limestone about 30 lbs., and soda ash about 5 lbs. The foregoing raw material formula is variable, it having been found that the carwheel content may be reduced and the stove plate content increased to considerable advantage. To each tap from the cupola there is added about two ounces of aluminum.

The molten metal is tapped from the cupola into a receiving ladle after the manner set forth in the first described process, suitably covered with charcoal, dose-d with soda ash, caustic soda, or the like, and otherwise treated with the same objects in view as in the case of the first described process.

The analysis of the molten metal in the receiving ladle after following such a procedure would be as follows:

Percent Carbon Under 3.50 Manganese Under .70 Silicon Under 1.35 Phosphorus Under 1.50 Sulphur Under .150

In a specific instance the following analysis was obtained:

- Percent Carbon 2.70 Manganese .325 Silicon .867 Phosphorus 1.02 Sulphur .109 Iron and misc Balance This metal when tapped into the charging ladle has the following analysis:

Percent Carbon Under 3.50 Manganese Under .70 Silicon Under 1.35 Phosphorus Under 1.15 Sulphur Under .150 Iron and misc Balance In a specific instance the following analysis was obtained:

Percent Carbon 2.80 Manganese .320 Silicon .8 1 1 Phosphorus 1.07 Sulphur .091 Iron and misc Balance From the receiving ladle the metal is drawn into charging ladle capable of holding sufficient metal to puddle which, in the case now being described, is about 700' pounds. It is preferred that the puddling process be carried. out as in the case of the breakage mixture in a furnace of the socalled Ely-type, such as is shown and described in United States patent to Ely #1,284,880. The puddling agent used for a 700 lb. charge consists of about 200 lbs. of iron ore and granulated furnace cinder in the proportions of about 50% each.

With a charge of the above character the puddling time will average about forty minutes. This increase in puddling time over the breakage mixture procedure is due to the greater carbon, manganese, silicon and sulphur content of molten iron. Necessarily, the low boil period with such a charge is considerably longer than when breakage procedure is followed, thus further accounting for the longer time necessary for puddling.

Muck bar from such iron has an analysis of:

Per cent Carbon Under .15 Manganese Under .06 Silicon Under .30 Phosphorus Under .115 Sulphur Under .015 Iron and misc Balance In a specific instance the following analysis was obtained:

Per cent Carbon 1; .10

Manganese -1 .045 Silicon .185 Phosphorus .088 Sulphur .009

A 1 round bar, single worked, made from muck bar of the above analysis has the following analysis V Per cent Carbon Under .15 Manganese Under .06 Silicon Under .30 Phosphorus Under .115 Sulphur Under .0 15,

In a specific instance the following analysis was obtained:

Per cent Carbon; .07 Manganese .045

Silicon .185 Phosphorus; .103

Sulphur .009

Slag and oxide 2.53 by Weight Iron and misc Balance A typical physical test of such a 1" round bar showed the following:

Tensile strength 49,350 lbs. per sq. in. Elastic limit 35,600 lbs.per sq. in. Per cent elongation in 8" 34.5% Reduction of area 48.8% Col-d bend. Flat on itself in one direction Hot bend Flat on itself in two directions Nick bend Showed remarkably long fibres It is found that, in the operation of the cupola under both methods of procedure, about 10 lbs. of soad ash should be added to the bed coke; that to the first ten taps from the cupola about 10 lbs. of soda ash should be added, and to each tap thereafter 6 lbs. of soda ash. Of course, the proportions of any substitute for soda ash, such as caustic soda, or Purite should be correspondingly adjusted.

Having thus described the illustrated embodiments of the invention and having in mind that variations and modifications of the same may be made; the scope of the invention is defined by the following claims.

What is claimed is:

1. In the process of producing wrought iron, the steps which consist in melting in a cupola furnace a mixture of ferrous scrap together with a small quantity of ferro-manganese, limestone, and soda ash, tapping the molten metal in a receiving ladle while adding a small quantity of aluminum for deoxidizing the iron oxide resulting from the reaction of the cupola furnace, treating the metal in the receiving ladle by the addition of soda ash and carbon, puddling in a furnace while subjected to agitation charges of the said molten metal in the presence of a slag composed of molten iron ore about fifty per cent and granulated furnace cinder about fifty per cent, the said granulated furnace cinder being selected with a view to a silica content in the slag of from about twelve per cent to twenty per cent and with a view to substantial freedom from magnesium oxide, calcium oxide, and copper, then graining and agglomerating the grain into a ball, raising its temperature, and then squeezing and rolling in the usual manner.

2. In the process of producing wrought iron, the steps which consist in melting a mixture of ferrous scrap in a cupola furnace together with a small quantity of ferro-manganese, limestone,

and soda ash, tapping the molten metal into a receiving ladle while adding a small quantity of aluminum for deoxidizing the iron oxide resulting from the reaction of the cupola furnace, treating the metal in the receiving ladle by the addition of soda ash, adding carbon to the metal, preventingatmospheric oxidation of the same, puddling charges of the said molten metal in a furnace while agitating the same in a slag composed of molten iron ore and granulated furnace cinder, the said granulated furnace cinder being selected with a view to a silica content in the slag of from about twelve per cent to twenty per cent and substantially free from magnesium oxide and calcium oxide and with a negligible copper content, graining and agglomerating the ball, raising its temperature, and then squeezing and rolling in the usual manner.

3. In the process of producing wrought iron, the steps which consist in melting in a cupola furnace a mixture of ferrous scrap together with suitable dosifying agents including soda ash, limestone, and also a manganese compound capable of reaction with iron oxide to form a manganeseoxygen compound, and also capable of reaction with sulphur to form manganese-sulphide, introducing into a puddling furnace capable of oscillation a charge of molten metal from said cupola furnace, together with a slag-forming mixture of iron ore and granulated furnace cinder proportioned to produce a slag containing not less than about 12% and not more than about 20% of silica, agitating the furnace and continuing such agitation until graining takes place, agglomerating the grains into a ball, and then removing the ball.

JOHN B. SCHLOSSBERG. GAYLE G. FRAZIER, Administratria: of the goods, chattels, credits, and estate of Lester E. Frazier, late. of Strdtford, county of Fairfield, State of Connecticut, Deceased.