US1347741A - Manufacture of steel - Google Patents

Description

UNITED STATES ROBERT ABBOTT HADFIELD, OF WESTMINSTER, ENGLAND.

MANUFACTURE or STEEL.

Specification of Letters Patent.

Patented July 27,1920.

No Drawing. Application filed August 10, 1917, Serial No. 185,523. Renewed May 27, 1920. Serial To all whom it may concern:

Be it known that 1, Sir ROBERT ABBOTT HAD-FIELD, Baronet, F. R. S.,'a subject of the King of Great Britain and Ireland,residing at the city of Westminster, England, have invented Improvements'in or Relating to the Manufacture of Steel, of which the ganese), which is always expensive and not always readily obtainable in sufiicient quantities to meet practical requirements, and at present is only obtainable in relatively small quantities and at many times its ordinary normal cost.

The invention also has for object to produce from stock or raw material that is not of high quality, that is to say, is not specially low in sulfur and phosphorus, steels that in addition to being practically free from or low in man anese, shall also be low in or practically ree from sulfur and other injurious impurities and which shall therefore be of high grade, and which, accordingto the amount of carbon present therein, are specially suitable for various purposes.

' A further object of the invention is to improve, when required, the physical and mechanical properties of steel produced according 'to the invention, and particularly of medium carbon steels.

For attaining the foregoing objects, H101? ten iron or steel is decarburized, de'siliconized and demanganized by the open hearth, Bessemer, electric or like process to the desired extent and the resulting product is deioxidized by a deoxidizing agent consisting wholly or mainly of silicon or aluminium, or silicon and aluminium, additional carbon if needed,'being also added to the molten metal by addition thereto of a carburizing agent of good quality to obtain'the necessary percentage of carbon.

- The silicon can be added in any suitable form, conveniently in the form of ferro-silicon, andthe aluminium as such. Additional carbon that may be required to increase the desired percentage thereof in the resulting steel, can be added at the same time to the molten metal in any convenient form, as for instance in the form of pig iron of good quality, as for example white iron, or as free carbon, for example as anthracite, and the whole thoroughly stirred together. The addition of either or both, of the deoxidizing agents and also the re-carburizing agent, if

used, may be made to the molten metal while it is in the furnace, the resulting steel being afterward run offinto a casting or other ladle or receptacle in the ordinary way.

Or the required amount of ferro-silicon, or of aluminium, or of both, and of the recarburizing agent, if required, can be added it may be in a liquid condition, to the molten metal while the latter is being run off from the furnace into a casting orother ladle or receptacle. Or the said deoxid'rzing and recarburizing agents may be placed, it may be in a liquid condition, in the ladle or receptacle and the molten metal run off from the furnace on to them.

If desired and when practicable, ferromanganese, may also be added tothe molten metal with the ferro-silicon or aluminium, or both, and re-carburizing agent, if used, but in this case a much less quantity than has heretofore been be needed. a

In the case of medium carbon steel,'suitable for use in the manufacture of high explosive shells and other articles which do not require to be hardened in the ordinary sense of the term, the-carbon may vary between say about decimal four five to decimal six of one per cent. I

In the case of high carbon steel, the carbon may vary from say about decimal eight of one per cent. of carbon and upward. For use in lieu of the ordinary expensive crucible cast steel for the manufacture .of cutting tools, instruments and the like, and for other purposes, the high carbon steel is made of high grade, the amount of silicon present in such steel being low but varying it maybe up to say about decimal three of one per cent.

For the manufacture of a medium carbon steel according to the invention, the charge of iron from which it is to be made, for example steel turnings, scrap and the like, may be treated in an open hearth furnace, or Bessemer converter, and the molten metal usual or necessary, will both, is or are then added in the required amount to and thoroughly mixed with the molten steel, to effect the required deoxidation thereof, which may be done either before or after the metal has been run off from the furnace or converter or during such running off. If required, and as hereinbefore stated, pig iron, or anthracite may be added to and mixed with the molten metal at or about the same time as the deoxidizing agent, to recarburize it to any desired degree.

Or, in carrying out the invention in an open hearth furnace, or in a Bessemer converter, the molten metal may practically be completely decarburized, desiliconized and demanganized and the ferro-silicon, or aluminium, or both, and the pig iron or other recarburizing agent, added in the required amounts to effect the necessary deoxidation and recarburization of the resulting metal to )roduce steel of the required quality.

r the roduction of medium carbon steel may be e ected in an electric furnace.

The following are given as examples of analyses of medium carbon steels produced according to the invention that have been found to give good results under test, namely: 7

0 Si s ,P Mn (a) .49 .03 .ll .01 .15 (b) .55 21.01 .016 .24 .58 .30 .067 .041 .54

The first mentioned steel (a) was produced by treating lyddite steel turnings and lyddite steel scrap in the proportion of about seventeen hundredweight of the former to about three hundredweight of the latter, according to the electric process in an electric furnace, and adding to the treated metal about one hundred and eight pounds of white iron, three pounds of ferro-manganese and one and a half pounds of aluminium, the aluminium being added to the metal when in the ladle into which it was poured.

The secondly mentioned steel (6) was produced by treating lyddite steel .turnings and lyddite steel scrap in about the same proportions as for steel (a) by the electric process and adding about two pounds of aluminium to the ton of treated metal in the furnace. v

The thirdly mentioned steel (0) was produced by treating a charge of 80% ordinary hematite and 20% scrap in a converter and adding to about eighty nine decimal seven nine per cent. of the blown metal in the ladle, about nine decimal six five per cent. of good quality pig iron, about decimal five six of one per cent. of ferro-manganese and about decimal two per cent. of aluminium.

For producing high grade steel, the charge of iron from which it is to be made, for example steel turnings, scrap and the like, may be treated according to the open hearth, Bessemer or like processes and afterward by the electric process, or wholly by the electric process in an electric furnace, so as to produce molten metal practically free from or very low in carbon, silicon, sulfur, phosphorus, manganese and other impurities, such metal being deoxidized by the addition of silicon, for example ferro-silicon, alumini- .um, or ferro-silicon and aluminium, and

recarburized by the addition of a carburi'zing agent of good quality, as for example good quality pig iron, for instance white iron, or anthracite, the deoxidizing agent and recarburizing agent being added'in such quantities as to leave in the finished steel the required amount of carbon, or carbon and silicon, to produce high grade steel of the required quality. The deoxidizing and recarburizing agents can'be added to the purified molten metal at any desired stage of the process, that is to say, while it is in the furnace, or while it is running from the furnace, or while it is in a ladle or other receptacle into which it has been run, as hereinbefore stated.

The following are examples of analyses of high carbon high grade steel produced according to the invention that have been found suitable for use as cutting tools C Si S P Mn (d) .82 .18 .020 .016 .24 (e) .80 .27 .010 .020 .06

The'high carbon steel (:21) was produced by treating in an electric furnace, a change comprising about ninety nine hundredweights of lyddite steel turnings, about twenty six tons of lyddite steel scrap, adding about eight and one half hundred-weights of good quality pig iron and about two hundred-wei hts of carburite and adding about six poun ds of aluminium to the resulting metal when run into a'ladle.

The high carbon steel (6) was produced by treating in an electric furnace about five tons of lyddite steel turnings and one and a quarter tons of lyddite steel scrap and adding to the finished steel when poured into a ladle about seven pounds of aluminium.

If desired, another metal as for example, nickel, chromium, aluminium, copper and so on, or two or more of such metals may be added to steel produced according to this with the sulfidaggregate disconnected thereinvention to produce special alloys of steel designed for different purposes. Thus, an alloy made of high grade steel with nickel and chromium and suitable for use in the manufacture of armor piercing projectiles, may contain for example about 56% C, 14% Si, 09% Mn, 2.75% Ni and 2.5% Cr, sulfur and phosphorus being very low.

To improve, when required, the physical or mechanical properties of steel produced according to the invention and particularly of medium carbon steel, that is to say, steels containing about decimal four to decimal six of one per cent. of carbon and designed for the manufacture of high explosive shells and other articles that do not require to be hardened in the ordinary sense of the term but which, in addition to being capable of being readily forged or pressed to shape, require to be very stiff and tough and'to give a high degree of elongation under test, say for example from fifteen to thirty per cent. of elongation, the said steel is subjected to a suitable heat treatment. This heat treatment can be varied but may'consist for example in heating the steel to a suitably high temperature, cooling it, as by quenching it in a cooling medium, as for example water or oil, either to the temperature of the cooling medium or of the external atmosphere,

or to a temperature above the ordinary atmospheric temperature, as by withdrawing it from the cooling medium at a suitable stage of the cooling, reheating it to a high temperature but to a less degree than the first heating and allowing it to cool either slowly -or quickly, some or the whole of these operations being repeated or not as may be found necessary. Thus the steel may advantageously be heated to about 850 0.,

say 855 (3., then quenched in. water and afterward reheated to say about 615 C. and

allowed to cool slowly in the air. The steel may be thusheat treated after it has been converted by pressing or forging into the desired article for example, a shell.

In steel low in manganese and produced as hereinbefore described, sulfur present therein as sulfid of iron is found, as shown by photo-micrographs of the steel, to exist for the greater part, in the cast metal, in the form of very small globules or specks of sul- 'fid aggre ates distributed. throughoutthe crystals 0 ferrite rather than'as segregated into larger masses located between the crystals of ferrite which would weaken the cohesion of'the crystals, with the result that the sulfur present has no harmful effect on the steel as determined by tests thereof, while, after heat treatment of the steel the sulfur isfound to have a beneficial effect resulting as shown by photo-micrograph of the steel,

through, being in the form of very. small angular crystals.

As the deoxidizing agents," silicon and aluminium are the chemical equivalents of each other and as the atomic weight of silicon and of aluminium is about half the atomic weight of manganese, the elements silicon and aluminium either singly or together are included in the general term light deoxidizing agent hereinafter used in some of the claims to distinguish such element or elements from the relatively heavy deoxidizing agent, manganese.

No claim is made broadly to the use of silicon and aluminium as deoxidizing agents, the use of which for this purpose being known.

What I claim is 1. The manufacture of steel containing from about decimal three of one per cent. to one percent. and upward of carbon and practically free from or low in manganese consisting in decarburizing, desiliconizing and demanganizing a molten charge of iron to the desired degree and deoxidizing the resulting product byv a light deoxidizing agent.

.2. The method of producing steel free from or low in managanese and containing from about decimal threeof one per cent. to one per cent. and upward of carbon, consisting in decarburizing, desiliconizing and demanganizing a molten charge of iron to the desired degree and deoxidizing the resulting molten metal by a light deoxidizing agent and recarburizing it to the desired degree by'addition thereto of a recorburizing agent.

3. The method of producing steel free from or low in managanese and containing from about decimal three of one per cent. to one per cent. and upward of carbon, consisting in completely decarburizing, desiliconizing and demanganizing a 'molten charge of iron, and deoxidizing the resulting molten metal by addition thereto ofa light deoxidizing agent and recarburizing it to the desired degree by addition thereto of a recarburizing agent.

.4. The method of producin steel free from or low in mana anese an containing from about decimal t ree of one per cent. to one per cent. and upward of carbon, consisting 1n decarburiz ng, deslhcomzing and demanganizing a molten charge of. iron to the desired degree by the open hearth method of treatment Sand deoxidizing the resulting metal by addition thereto of a light deoxidizing agentv and recarburizmg .it to the desired degree by addition thereto of a recarburizing agent.

5. The method of producing high grade steel from lower gradematerial and containing from about decimal three of one per cent. to one per cent. and upward of carbon,

consisting in melting a charge of iron and treating it by the electric furnace process so as to produce molten metal practically free from or Very low in carbon silicon, sulfur, phosphorus and manganese, deoxidizing the resulting metal by a light deoxidizing agent and recarburizing it to the desired extent by a recarburizing agent.

6. The method of producing high grade steel from lower grade material and containing from about decimal three of one per cent. to one per cent. and upward of carbon, consisting in melting and treating a charge of the lower grade material by the open hearth method of treatment so as partly to decarburize, desiliconize, demanganize, desulfurize and dephosphorize the metal and afterward subjecting the resulting molten metal to the electric furnace process; so as to produce molten metal practically free from or low in carbon, silicon, sulfur, phosphorus and manganese, deoxidizing the resulting molten metal by addition of a light deoxidizing agent and recarburizing it to the desired extent by a recarburizing agent.

7. The method of producing medium carbon steel, consisting in decarburizing, desiliconizin and demanganizing a molten charge of-iron to such an extent that it does not contain more than about decimal four five to decimal six of one per cent. of carbon and not more than about decimal three of one per cent. of manganese and deoxidizing the resulting molten metal by addition thereto of a light deoxidizing agent as set forth. t

8. The method of producing medium carbon steel, consisting in decarburizing, desiliconizing and demanganizing a molten charge of iron to such an extent that it does not contain more than about decimal four five to decimal six of one per cent. of carbon and not more than about decimal three of one per cent. of manganese, deoxidizing the resulting molten metal by addition thereto of a light deoxidizing agent and recarburizing the metal to the desired extent by addi tion thereto of a recarburizing agent.

. 9. The method of producing high grade steel from lower grade material or stock and containing from about decimal three of one per cent. to one per cent. and upward of carbon, consisting in decarburizing, desiliconizing and demanganizing a molten charge of the lower grade material and dephosphorizing and desulfurizing the partly purified charge by the aid of the electric furnace process, deoxidizing the resulting molten'metal by addition thereto of a light deoxidizing agent and recarburizing it to the desired degree by a recarburizing agent.

10. The method of producing high grade steel from lower grade material or stock and containing from about decimal three of one per cent. to one per cent. and upward of carbon, consisting in decarburizing, desiliconizing and demanganizing a molten charge of the lower grade material by heat due to combustion and dephosphorizing and desulfurizing the partly purified charge by the aid of heat produced by the aid of an electric current, deoxidizing the resulting molten metal by the addition thereto of a light deoxidizing agent and recarburizing it to the desired degree by addition thereto of a recarburizing agent.

11. The method of producing high grade high carbon steel, consisting in decarburiz-- ing, desiliconizing and demanganizing a molten charge of iron, dephosphorizing and desulfurizing the partly purified charge by the electric furnace process of treating iron, deoxidizing the resulting purified metal by addition thereto of a light deoxidizing agent and recarburizing it by addition thereto of a recarburizing agent so that the resulting metal contains about decimal eight of one per cent. and upward of carbon.

12. The method of producing high grade high carbon steel from lower grade material,

'- consisting in treatinga molten charge of the lower grade material by the electric furnace process so as to render the metal practically free from or very low in carbon, silicon, sulfur, phosphorus and manganese, deoxid izing the resulting metal by addition thereto of a light deoxidizing agent and recarburizing it by addition thereto of a recarburizing agent so as to produce steel containing from about decimal eight of one per cent. and upward of carbon, silicon Varying up to about decimal three of one per cent. U

Signed at 22 Carlton House Terrace in the city of- Westminster England this twelfth day of July 1917.

ROBERT ABBOTT HADFIELD. Witnesses:

WILLIAM Cnoss, LEONARD ROWLAND