US1924581A - Alloy - Google Patents

Description

Patented Aug. 29, 1933 UNITED STATES 1,924,581 ALLOY Richard A. Wilkins, Rome, N. Y., assignor to Revere Copper and Brass Incorporated, Rome, N. Y., a corporation of Maryland No Drawing. Application December 25,, 1931, Serial No. 583,160. Renewed May 22, 1933 6 Claims.

This application is a continuation in part of applicant's prior application Serial No. 539,998, filed May 25, 1931.

My invention relates to heat treatable high copper content alloys and to methods of working the same.

Alloys made according to the invention are generally characterized by a high copper content, resistance to fatigue and corrosion, high tensile strength, hardness, toughness, and the property of being capable of being drawn, rolled and extruded while hot or cold by usual mill processes.

The invention however will be best understood from the following description of alloys compounded according to the invention, and of examples of the practice of methods of controlling their physical and chemical characteristics and of working the alloys.

Alloys according to the invention contain copper, iron and silicon, with the balance predominantly zinc, the approximate ranges of these metals being it being understood however that all alloys having these four metals each within the ranges specified will not give the improved alloy, as will hereinafter appear.

According to the invention, the high tensile strength, toughness and non-corrosive properties of the alloy are primarily secured by incorporating silicon, while the hardness is primarily secured by incorporating iron. The silicon, it has been found, tends both to dissolve in the basic solution and to combine with the iron to form iron silicide. By suitably proportioning the silicon to the iron, and by keeping the amount of the latter small, all the iron will be in the form of iron silicide, which latter, by suitable heat treatment of the alloy, may either be dissolved to permit the alloy to be worked, or be precipitated in the form of fine crystals to harden the alloy.

It has been found that when the amount of iron silicide present is small, it is completely dissolved in the alloy when at temperatures above approximately 800 F., and that it will remain in solution if the alloy at these temperatures is suddenly cooled, whereas if the alloy at these temperatures is slowly cooled it will be precipitated in the form of exceedingly minute microscopic crystals. This desirable property permits the alloy with the dissolved iron silicides to be worked without wear and injury to the dies, cut ting tools, and the like employed for this purpose, which wear and injury would otherwise occur if the iron silicide were precipitated. On the other hand, after the alloys are worked with the iron silicide in solution, they may be hardened by heating them and slowly cooling them to precipitate the iron silicide, the crystals of which act to lock the so-called glide planes of the basic solid, or, in effect, to key together the crystals of the basic solid, for imparting hardness to the alloy.

It has been found that the above effects will not be secured if the amount of iron is in excess of 0.6% of the alloy, for if it exceeds this amount segregates of iron silicide will always exist in the solid alloy,,in spite of the above mentioned heat treatment, and further that these segregates and precipitated crystals will be so large and so inadequately distributed as to secure an unsatisfactory key hardening effect. Also it has been found that if the iron content is high with relation to the silicon content all the iron will not combine with the silicon, resulting in the presence 8 of free iron, because the latter is practically insoluble at all temperatures in the basic solid. The presence of free iron acts to destroy the noncorrosive properties of the alloy imparted thereto by the silicon. Free iron also renders the alloy subject to fatigue, rendering it unsuitable for many uses, say for shafting-,-as do likewise the presence of large segregates of iron silicide and the presence of iron silicide particles which are materially large.

Applicant has found that the iron and silicon in the melt combine in the aggregate approximately according to the formula Fe Si, in other words, about one part silicon to two parts iron. However, the silicon besides tending to combine with the iron also strongly tends to dissolve in the basic solution, and to compensate for this latter effect and cause all the iron to be combined with the silicon, it has'been found necessary to employ, for a given amount of iron, an excess of silicon over that which combines with the iron. In this respect, satisfactory results will be secured if approximately three extra molecules of silicon are added for each molecule necessary to combine with the iron, which is to say, that the amount of silicon should not be less than approximately twice the amount of iron. To secure the other valuable properties hereinbefore mentioned the amount of silicon may be in excess of this latter amount, appreciable results being secured in respect to all these valuable properties when the iron is in excess of 0.1% and the silicon is in excess of 0.4%, provided however the iron does not exceed the above mentioned 5 0.6% and the silicon, for reasons hereinafter mentioned, does not exceed about 5%.

The increased tensile strength and toughness imparted by the silicon in solution is secured at the expense of ductility of the alloy, and this is compensated for in the .present invention by the addition of zinc so as to secure an alloy which may be worked either hot or cold by usual mill processes. If a corrosion resistant alloy is desired, the zinc content however should not be abnormally high with relation to the silicon content, lest the zinc unduly impair the resistance of the alloy. to corrosion, and from this aspect best results will be secured when the amount of zinc does not exceed about seven or eight times the amount of silicon. Further, the copper content, to secure the valuable properties hereinbefore mentioned, should be high with relation to the zinc content, lest the silicon. cause a structure of the alloy resembling so-called beta brass or that of a mixture of beta and gamma brass, neither of which presents a crystalline structure which is capable of coacting withthe iron silicide according to the present invention. From this aspect the silicon should not exceed about 5%, and the copper range should be approximately between 88 and 93%, with the balance of the alloy approximately all zinc but not exceeding about 10% of the alloy for the lowest amounts of copper, although,'if desired, small amounts of other metals or metalloids may be incorporated for insuring special results or properties as, for example, 0.25% of the total alloy may be aluminum to improve the grain structure of the basic solid. A suitable alloy having all around properties of hardness, toughness, high tensile strength, and workability may consist of approximately 5% zinc, 2.5% silicon, 0.25% iron, with the balance copper.

As an example of a suitable process of fabricating the alloy, but without limitation thereto, the copper may be melted in an electric furnace or crucible, and to the molten copper may be added the silicon in the form of a copper alloy rich in silicon, say one containing about 10% silicon. Next the iron may be introduced in the form of a copper alloy rich in iron, and after these ingredients have been well melted and thoroughly stirred, the zinc may be introduced, preferably in the form of scrap brass. Preferably, immediately upon the zinc being introduced, the melt is poured so as to prevent escape and loss of zinc from the melt. heat treatment of thealloy preparatory to working it, the billet conveniently may be cast in a chilled mold, and when it has cooled to about 800 F. may be quenched by plunging it in water. As has hereinbefore been explained, at approximately 800 F. the iron silicide is in solution, and this sudden cooling of the billet prevents precipitation of the iron silicide, thus forming what amounts to a super-saturated solution of iron silicide in the resulting cold alloy. After this heat treatment the billet is very malleable and ductile, and may be rolled, drawn, or otherwise worked hot or cold, by usual mill processes, and machined, without any harmful effect of the iron silicide on the dies, cutting tools, or the like. Articles thus shaped or formed may then be hardened by heating the alloy and slowly cooling it, say by heating formed while the material is hot.

In respect to the the heater and permitting it to cool in the air.

Commonly, however, due to economic considerations, the castings are allowed to cool normally in the foundry, and then are transported to the mill, where they are reheated and the preliminary work of rolling, drawing and piercing is peris then heated to about 1000 F., or other convenient temperature above 800 F., for about one hour and quenched in cold water to form the super-saturated solution above mentioned, after whichthe final cold finishing operations of rolling, drawing, etc. are performed. The final fab-- ricated articles may then be heat treated as above described for securing the precipitation of the iron silicide for hardening the articles.

It will be understood that wide deviations may be made from the specific forms of the invention above described without departing from the spirit of the invention.

I claim:

' 1. Alloys containing approximately from 88 to 93% copper, 0.1 to 0.6% iron, 0.4 to 5% silicon, with the balance approximately all zinc; in each particular instance the amount of silicon being not less than twice the amount of iron and the zinc not exceeding approximately 10%.

2. Alloys containing approximately from 88 to 93% copper, 0.1 to 0.6% iron, 0.4 to 5% silicon, with the balance approximately all zinc, in each particular instance enough silicon being present to cause substantially all the iron to be combined with silicon to form iron silicide, and in each particular instance the zinc not exceeding approximately 10%.

3. Alloys containing approximately from 88 to 93% copper, 0.1 to 0.6% iron, 0.4 to 5% silicon, with the balance approximately all zinc, in each particular instance enough silicon being present to cause substantially all the iron to be combined with silicon to form iron silicide, and in each particular instance the zinc not exceeding approximately 10%, the iron silicide being in the form of minute particles uniformly distributed in a base of copper, zinc and silicon.

4. Alloys containing approximately from 88 to 93% copper, 0.1 to 0.6% iron, 0.4 to 5% silicon, with the balance approximately all zinc, in each particular instance enough silicon being present to cause substantially all the iron to be combined with silicon to form iron silicide, and in each particular instance the zinc not exceeding approximately 10%, the iron silicide being dissolved in a base of copper, zinc and silicon.

5. Heat treatable, corrosion resistant alloys containing copper, iron, silicon and zinc in which the range of iron is varied between 0.1 and 0.6% to vary the available hardness, the range of silicon is varied between 0.4 and 5% without the RICHARD A. WILKINS.

The material