US1920910A - Alloy steel and its manufacture - Google Patents

Description

Patented Aug. 1, 1933 PATENT orncr:

ALLOY STEEL AND ITS MANUFACTURE Joseph Russel Cornell Marsh, Arlington Heights, 111., assignor to Francis Norwood Bard, Chicago,

No Drawing. Application October 2 4, 1923 Serial No. 670,524

4 Claims.

My present invention relates to iron or steel in general, and more particularly to iron products into which modifying elements are intro-- duced for the purpose of imparting thereto certain desired characteristics, and relates also to' 5 the manner of obtaining such products and characteristics.

In the making of alloy steels generally, the metallurgical process is mutually dependent upon the use of carbon in substantial amounts, which procedure not only increases the cost of carrying out the process but would not be successful in respect of the product if but a trace or a relatively small amount of carbon were present.

Furthermore, the principal alloy steels known,

if not substantially all that are available, have as incidents to their manufacture and use as an essential step more or less complex heat treatments requiring special facilities and thereby involve not only expense and inconvenience but also a loss of time. 7

Again, the use of alloy material is ordinarily highly expensive incident to one or more of the following factors: The prime cost thereof, the cost of introducing the same into the ferric prod- 5 not, the cost of manipulation of the product after such introduction and of any change after such manipulation, if such change be requisite and possible, and of the care with which the various steps must be carried out and of the uncertainty of attaining the desired objective within close limits. I

Among the more important objects of my invention are the production of a steel having increased tensile strength and one characterized by high elongation with reduction of transverse area, and by resistance to oxidization and corrosion, and one permitting the use of material having a low, in fact a very low even incidental carbon content to give at a low cost better physical re- 40 sults than have heretofore been available in the case of low carbon steels, and to produce at a low cost steels which may be used not only in the place of higher cost alloy steels but may be so used without heat treatment; the provision of alloy steels characterized by the introduction of modifying means which raise the yield point and ultimate strength of the product, impart qualities of non-oxidization thereto, increase elongation and reduction of area, increase hardness and resiliency, efiect compensation in respect of certain degrees of hardness and other qualities for the absence of percentages of carbon or other modifying agents which are either difi'lcult, expensive or otherwise objectionable as heretofore necessary; the provision of modifying means which may be most perfectly distributed throughout the mass of the product with consequent uniformity in texture, structure and density; the provision of an improved process for utilizing a plurality of modifying means for the production of an alloy steel characterized by qualities which are absent from such modifying means and are not obtainable by any one of them taken alone; the provision of a copper alloy steel characterized by the absence of deleterious qualities incident to the use of copper hitherto; the provision of an alloy steel characterized by the use of aluminum;

the provision of an improved process for modifying steel by the means'of copper to permit the ad dition of aluminum thereto; the provision of an improved process for modifying steel by the means of copper to permit the addition of material as a modifying agent for steel not hitherto utilizable; the process of producing steel containing copper as a modifying agent which includes the use of aluminum as a modifying agent to overcome hotshortness; the provision of an improved process for making steel which includes the useof aluminum, and more particularly of a modifying agent in connection therewith which permits of the successful use of aluminum; the provision of animproved process of making steel including aluminum as a modifying agent which further includes the use of material having suflicient latent heat to so maintain the temperature of the molten steel as to permit'the use of aluminum; together with such further and additional objects as may hereinafter appear or be pointed out.

In my experience, it has been found that steels modified by the addition of copper per se in sufiicient quantities to give the desirable technical effects from the standpoint of copper also involve. among others, the objectionable characteristics of hot-shortness. For this reason it has been my past practice when using copper to make a steel of relatively high carbon content and to use copper only in such quantities and under such circumstances as will not make this objectionable characteristic, such as hot-shortness, so predominant as to overcome the benefits of its use.

- and, furthermorefto rely upon other modifying elements to overcome the undesirable incidents to the use of copper.

These modifying elements, which were used by me in addition to copper hitherto for the purposes above set forth, were generally expensive, not readily available, especially within the confines .of the continental United States, and rendered the alloys relatively difficult and expensive of production and use,v

While aluminum is probably one of the most readily available and most inexpensive of possible alloy modifying agents, its use as such has been impracticable because of the impossibility of maintaining such a temperature for a time sufficiently long as to maintain the melt in such a fluid state as will permit both of a thorough mixing of the aluminum with the ferric mass and also permit pouring of the alloy steel thus produced before solidification. I have discovered, however, that by associating with the aluminum another modifying agent, such as copper, this defeet which renders the use of aluminum impracticable, is overcome. I have furthermore discovered that the association with copper of aluminum as a modifying agent overcomes the hotshortness which characterizes the use of copper. Furthermore, I have found that copper and aluminum are not only in eutectoid solution inter se but also form a eutectoid solution as modifying agents for steel and that their use is attended with the production of a most perfect and uni-' form mechanical mixture of each with the other and of both with the ferric mass with a resultant product of the highest degree of hardness, density toughness and uniformity of composition.

Furthermore, the association of the twoin the manner and for the purpose specified apparently results in not only a mechanical mixture of the character set forth, but results in a mixture which appears to exhibit a high chemical afiinity, not only while in the fluid state but also and to a greater extent when the alloys solidify. In other words, I have found that in the practice of my invention the employment of these two modifying elements is attended with no appreciable harmful segregation. Furthermore, the employment of copper in association with aluminum renders available, from the standpoint of the technique of manufacture, the use of aluminum in so far as the tendency of aluminum to lose its heat quickly is compensated for by the association therewith of the copper. This resultsfrom the latent heat particularly noticeable in molten copper supplying the deficiency of the aluminum in its heat retaining characteristics. This association of copper and aluminum is basic in that the results attained by their associated employment is not only unexpected from the use of either, or from their joint use, but the presence of each appears to modify the other in its relationship in the mass both physically and otherwise and as to the character and characteristics which it gives to the mass. The results attained by this association of aluminum and copper are accountable for only by an intense affinity therebetween or even a true chemical union therebetween, which is not essentially changed by the addition of further modifying agents.

Thus, I have found that the employment of additional and other modifying elements, such as nickel and/ or manganese in increased content not only tends to produce an intensification of the action peculiarly attained by the copper-aluminum modifying means, but also imparts to the mass certain additional qualities due in part to the presence of these additional modifying agents, but more so to their presence in association with and intensification of results attained by the use of the copper-aluminum modifying agent. Among such qualities, for example, are increased ultimate strength, elongation, hardness, torsion, etc.

In the actual practice of my invention, I have found that the different modifying agents may 0 Mn S1 l Cu Al Ni (1)- .09 .21 .n 1. 05 .07 (2) .10 27 21 81. 22 (3) 10 50 17 1. 25 38 (4g .10- .50 .17 .75 .38 (5 l5 50 17 75 38 (6) .30 .60 .17 70 .20 (7) 30 60 17 70 20 (8) 23 25 As it will be observed upon viewing these tables,

although I have found that a variation in the carbon content by way of increase gives more satisfactory results when used in connection with other supplemental modifying agents such as nickel, nevertheless the carbon content at all times is such that all the steels shown and described by me are of the nature properly characterized as low carbon steels. In fact, I have found that where I have attempted to use a carbon content of such a nature and property as would justify terming the steel as one of high carbon content such use has, in fact, been deleterious. It will be further observed that the presence of the nickel as an additional modifying agent may be attended by an increase in the percentage of the carbon and manganese contents and with a decrease in the percentage of the basic modifying agents, viz: copper and aluminum, but that the silicon content is substantially immaterial, within the usual ranges.

The precentage of aluminum that may be used is determined in actual practice within permissible limits by the amount of the melt and in part by the conditions under which it is to be poured, that is, the proznptness with which the molten metal may be poured, the size of the casting, etc.

One of the factors that renders the use of the copper-aluminum modifying means particularly valuable is that the alloy steel produced thereby not only is of substantially the low carbon content mentioned above but that no heat treatment is required for this production, and that thereby all the incidents associated with the use of heat treatment are avoided.

Again, alloy steels produced by me in the manner above set forth possess the characteristics, on the one hand, of high carbon steel in the matter of the wearing powers, and, on the other hand, possess the characteristics of low carbon steel in their lack of susceptibility to disruption in the presence of low temperatures. It will, therefore, be understood that I am able to produce at relatively low cost a low carbon steel which possesses all the desirable characteristics of the more expensive alloy steels and, in fact, possesses some of these qualities to an even higher degree, and this again without heat treatment from which it will be understood to what extent my process -is desirable.

I have furthermore found that the distribution throughout the mass is uniform, not only as to the copper and the aluminum, but also as to the carbon. In other words, the use of the copper-aluminum modifying means results additionally in attaining a most uniform distribution of the carbon as well as of these modifying agents themselves and in this manner the segregation of carbon is prevented.

The copper and the aluminum alloy in combination with the iron appears to form a thin film around the crystalline structures, filling the space between the crystals, and thus acting not only to render the mass most dense, but also, as it were, acting as a cushion between the crystals to uniformly distribute the stresses thereon.

The alloying material has been introduced by me into the bath in several different ways. One convenient way is to wire the desired quantities of copper and aluminum to a puddling rod, and puddle it in the bath until they melt. Alternately, an alloy of the desired proportions may be made, and cast into ingots of the desired size, threaded on one end, and then screwed onto the end of a special puddling rod, by which the ingot can be agitated in the bath and melted.

As illustrative of the virtues of steel containing one of the associations of modifying elements of the present invention, as hereinabove set forth, (C .23%, Al 25% and Cu .80%,) I cite the following cold bend tests of bars of dimensions x /2" bent around /2" diameter, viz:

Comparative test A The test bars were put into a cooling solution and held for forty-five minutes at 28" F., then removed and bent in ten seconds.

From the foregoing it is manifest that the two special ingredients of applicant's steel (as compared with commercial railroad rail-sections) act as agents in preventing breakages at low temperatures. This is believed to be due to the high latent heat of steel containing them.

The foregoing tests were made of material that had not been annealed. Furthermore, appliworthy that applicant's bars had the disadvantage of the lack of uniformity of pressure ensuant upon forging as contrasted with the relative uniformity of pressure ensuant upon rolling.

The chief point to be observed in the-use of Cu and Al is that in combining these two elements before their introduction into the molten iron, the chilling effect of introducing the Al, with its low melting point is overcome. For example, an alloy of 80% Cu and 20% AI will have a melting point above 1900 F. In introducing this alloy into the molten iron the temperature of the iron is not so quickly or materially lowered as would be the case if the Cu and A1 were added separately. Also the likelihood of the Al to combine with oxygen would not be as great, thereby cutting down the loss of the metallic Al.

The employment of an alloy of Cu and A1 with the Cu in a large enough percentage to materially raise the melting point, close up to the melting point of the Cu and closer to the melting point of the Fe greatly eliminates the confining of the Al to that portion of the molten iron with which it first comes in contact.

Having thus described my invention and illustrated its use, what I claim as new and desire to secure by Letters Patent is:-

1. The method of alloying copper and aluminum with steel which comprises mixing with the steel a copper-aluminum alloy.

2. As a new product, a stable surface alloy steel capable of being worked and comprising aluminum from .07 to .38 percent, copper from .70. to 1.25 percent, carbon from .09 to .30 percent. and the balance iron.

3. A stable surface alloy steel capable of being worked and comprising as essentials of the. alloy, aluminum from .07 to .38 percent and copper from .70 to 1.25 percent.

4. The process of making copper-aluminum alloy steel, which comprises diffusing a. copperaluminum alloy into molten steel by puddling'the same thereinto.