US2144001A - Low metalloid iron-manganesecopper alloy - Google Patents

Description

Patented Jan. 17, 1939 UNITED STATES LOW METALLOID IRON-MANGANESE- COPPER ALLOY Raymond S. Simmons,

Peoria, 111., assignor to Keystone Steel & Wire Company, Peoria, Ill., a corporation of Illinois No Drawing.

' Serial N 2 Claims.

This invention has reference to a low metalloid A iron-manganese-copper alloy which is particularly adapted for use in the manufacture or production of articles to be subjected to a case hardening process.

The invention has for a further object, the production of a low metalloid carburizing steel, from which may be manufactured articles involving difficult cold forming operations and subsequent case hardening, whereby to obtain the most efficient surface wearing qualities; as for example cross-links for automobile tire chains, sheet metal screws, push rods for Diesel engines, and other and various articles or parts.

A further object is the, production of a low metalloid iron-manganese-copper alloy, from which may be manufactured or produced articles or parts in which strength as well as high duetility for severe cold forming operations is desirable, but where case hardening is not a factor.

My improved alloy can be produced by the open hearth, Bessemer or electric furnace process, or by a combination of any of these processes; but I prefer to produce the alloy by the basic open hearth process. The furnace should be charged with metallics whose content is very low in silicon percentage. A typical charge consists preferably of to of heavy melting steel scrap and 30% to 40% of a special low silicon grade of pig iron. The silicon content of the iron used must be as low as possible, preferably under .75%. Cast iron railroad car wheels are a good example of the type of iron which should be used. The regular oxidizing process for the removal of the impurities in a basic open hearth furnace is car ried on to a much greater extent than is .commonly employed, except in such cases as it is used in the manufacture of the now well recognized ingot iron or similar metal. Low carbon ferromanganese grade A is then added to the metal. Such ferro-manganese should not have a carbon content of over 1.10% (preferably as low as 0.60%), or a silicon content over 1.00% "(preferably as low as 0.60%).

The chemical analyses of an alloy so made, is as follows:-

Per cent Iron 97 to 99 Manganese .60 to 1.30 Copper .15 to .50 Metalloids Less than .15

The metalloid content is considered the total percentages of carbon, phosphorus, sulphur and silicon found by chemical analysis in the alloy.

Application January 28, 1938 The total percentage of these metalloids may be as high as 0.20%, but this is not particularly desirable or useful.

The alloy of my invention will be found to have very desirable properties, especially for the manufacture or formation of articles or parts which, after case hardening, must have an extremely hard (Martensitic) surface and an extremely soft, ductile center or core.

I am aware, and those skilled in the art recognize that certain articles can be produced by a process known as case hardening. Such a process consists of impregnating the surface of an article with a high percentage of carbon by the use of a solid, liquid, or gas at a, temperature of approximately 1600 F. The article, whose surface is so impregnated with carbon, is then quenched in water, oil or other liquid from a temperature above the critical temperature of the resultant metal in the carburized surface or case.

I have discovered that articles or parts produced from my alloy, when carburized on the surface, can be quenched much more easily and less drastically than any other alloy within my knowledge, or which may have come to my attention during many years of experience in the use and manufacture of alloys. In other words, the carburized case or surface'obtained on an article or part, made from my alloy, and which is subjected to a carburizing process, is much deeper hardening than that produced by any other alloy, with which I am familiar, and with the same ductility or toughness remaining in the core or center. By keeping the metalloids, in the alloy, very low, the article or part made from such alloy, when carburized, will not be as brittle and subject to shatter or water cracks, as will an alloy where the carbon, phosphorus, sulphur and silicon are not employed in comparative percentages with the other ingredients, iron-manganese and copper, as herein disclosed. Metals, other than iron-manganese and copper, when present in my alloy will also cause the carburized case to shatter when quenched. A typical carburized case might have a carbon content of 1.20%, and a manganese content of 1.20%. If another metal such as chromium is present, the carburized case will shatter when quenched in water, for instance. It is well recognized that an alloy which is full of so-called shatter or watercracks will not withstand a sharp impact, and it is this serious fault which I obviate in the use of my alloy.

With reference to the ferro-manganese used in the manufacture of the alloy I want it understood that I have in mind a so-called carbonfree ferro-manganese, as compared with common ferro manganese. The latter has, in itself, a carbon content of about 7% and a manganese content of about 80%. To employ common ferromanganese in my'alloy would raise the carbon content to limits which would frustrate the objects and purposes of my invention.

The manganese content of my alloy is larger than the amount generally added to make the metal more malleable at forging or hot rolling temperatures. fully controlled amount to obtain the objects and for the uses and purposes herein stated.

The copper content of my alloy is added in a specific and well controlled amount in order to strengthen and stiffen the ferrite constituent ,of the alloy and it also acts as a surface stabilizer, to prevent rapid scaling of the metal in a butt or spot welding operation to which certain manufactured articles or parts are often exposed just before a carburizing operation.

The low metalloid content of my alloy is carefully controlled because I have discovered that case hardened articles and parts with a high metalloid content are very weak under the force of a sharp impact and quite often fracture more readily under repeated impacts than the same article and parts produced from my alloy.

A typical analysis of my alloy at its best, but.

not to limit the invention, the following example will suffice:-

Per cent Carbon. 0.60 Silicon l v 0.010 Phosphorus 0.012 Sulphur 0.038 Manganese 1.00 to 1.30 Copper s .25 to .50

Iron -i 97.00 to 199.00

Patent No. 2,11%001.

RAYMOND s. .SIMMONS.

It is added in a large and care- For certain uses the manganese content would be 0.80% and the copper content would be 0.25% or the manganese content would be 1.10% and copper content would be 0.50% and the metalloid content in each instance would be substantially as last above indicated. I have obtained very satisfactory results with the manganese content ranging from 1.00% to 1.30% with a carbon' content in the alloy of less than 0.10%.

The phosphorus and sulphur contents in my alloy are somewhat close to the normal contents of these ingredients in ordinary steel, but I am not aware of a steel with such a low carbon and silicon content and with such a high manganese content as is present in my alloy and because of which I am able'to obtain the results herein described.

What I claim is:

1. As a new article of manufacture, a low metalloid iron-manganese-copper alloy characterized by its susceptibility to case hardening to provide an extremely hard surface confining a relatively soft ductile core, said alloy containing manganese from .50% to 1.30%, copper from .15% to .50%

-with metalloids including carbon, phosphorus,

sulphur and silicon, the total percentage of which is less than 20%, andthe balance iron, the car bon content not being below .05% or above .10%.

2. As a new article of manufacture, a low metalloid iron-manganese-copper alloy characterized by its susceptibility to case hardening to provide an extremely hard surface confining a relatively soft ductile core, said alloy containing manganese from 1.00% to 1.30%, copper .15% to .50%, with a metalloid content of less than 15%, and the balance iron, the carbon content not being below .05% or above .08%.

RAYMOND S. SIMMONS.

January 17," 19 9..

It is hereby certified that error appears in the printed specification of theebove numbered patent requiring correction as follows Page 2, first column, line 51 in the table,f for "0.60" read 0.06; and, second column, line 2t, claim 1', for ".5075 to 1. read 50% to 1. 0%; and that" theisaid Letters Patent should be read with this correctioniherei-n that-the same may conform to the record of the case in the Patent Office.

signed and sealed this 7th day of March, p. 11959. 4

Henry Van Arsdale Acting Commissioner-of Patents.