US2058375A - Alloy - Google Patents

Description

Oct. 20, 1936. J. H..cR| 1'cHErT 2,058,375

ALLOY I Filed May 12, 1933 /aa Copper ff AVVAVA 75 AVAVAVVAVA 70 Q VV V V V ml. Ce o/o SII/icon [ra/7 A INVENTOR Z4/wis H CfP/rcf/Err BY ATTORNEY u Patented Oct.V 20, 1936 James n. crache, nouglaston, N.'Y.,'mino'r, by mesne assignments, to Union Carbide .and Carbon Corporation, a corporation o! New York Application May $2, 1933, Serial No. 670,673 3 claims. (cl. '1s- 134) Copper and chromium are frequently added to ferrous alloys to improve the physical and chemical characteristics of the alloy. In the past it has been necessary to make the additions of cop- 5 per and chromium separately,in the form of copper and chromium or ferrochromium, since copper will not alloy in large proportions with either chromiumor ferrochromium. Neither copper,`

' because of its low rate of solubility in iron, nor` l0 chromium and ferrochromium, because of their high melting points, go readily into solutio'n in ferrous alloys.

y The chief object of the present invention is to provide a series of alloys having a relatively large content of copper and chromium, and at the same time a melting point sumciently low to adapt the alloy for such uses as a pre-alloy for adding copper and chromium to ferrous metals and a coat-` ingalloyto be applied, for example, by placing the pulverized alloy upon a sand mold and casting a ferrous metal within the mold.

Another object of the invention is to provide' a process for making such alloys.

It is found that by the addition of sufcient silicon, relatively large amounts of copper may.

In the accompanying drawing. the singleiigure is a mmcibility diagram by which the above-described relationships may be determined. Iron and chromium are therein treated as a single 40 component, inasmuch as' it is found that chromium and ferrochromium behave with practicall /similarity in dissolvingcopper and silcon. The diagram represents alloys made from commercially pure materials, namely, bar or scrap cop- 5 per, high-carbon ferrochromium containing from H4% to 8% of carbon and about 60% to 70% chromium, and ycommercial ferrosiliccn. If a lower-carbon material is substituted for the highcarbon ferro-chromium, for instancechroinium '50 metal orlow'carbon ferrochromium, *somewhat (less silicon will be required as a minimum to render. the resulting composition homogeneous.

marked Zone of miscibility form a single homo- 55 geneous liquid phase` at or slightly above the the bottom section the richer in respect to copper melting point of the composition, and thisI liquid when cast forms a substantially homogeneous ingot. VFor lany given desired ratio of copper to ferrochromium or chromium, the minimum amount of silicon which must be added to render 5 the alloy homogeneous is to be found ,at the in tersection of the line separating the two zones with the lines representing percentages of copper and chromium y or ferrochromium. in the ilnal alloy. 10

Compositions which. from the relative proportions of the materials melted together, would give an alloy within the portion of the diagram marked Zone of ,immiscibiiity do not 'form homogeneous ingots of the desired analysis, but l5 tend to separate into two phases. When cast very hot and cooled slowly in a sand mold, such compositions form in'gots having two distinct sections which may be separated cleanly ata more or less, smooth interface. of these duplex ingots is homogeneous, but the analysis of one section differs from that of the other. In general, the upper section tends to be the richer in respect to chromium content. and

content. 'I'he composition of each section may 25 be estimated from the diagram as follows: mark the point within the zone of immiscibllity which corresponds to the average composition of the mixture to be melted, through this point draw'a line parallel to the silicon percentage ordinate, the two intersections of this line with the line separating the two zones will then represent the respective analyses of the two layers ofthe ingot.

The alloys ofthe invention may be made by melting a portion of chromium or ferrochrof mim, adding a portion of silicon or ferrosilicon,

land then making additions of copper and silicon or ferrosilicon alternately'.v The temperature oi' the melt should be kept high, preferably above 1500 C., and melting may suitably be done in an electric arc furnace or induction furnace. The above described order of additions has many advantages in producing sound and homogeneous alloys. If\'the order is changed, difficulties in securing homogeneous vcompositi/ons without lengthy heating are encountered. gf/

Tlhe invention comprises the substantially honrogeneous alloys of copper, silicon, chromium,

and iron, within the ranges of\composition: 20% 50 to 40% copper, 20% toA 43% chromium. 15% to 30% silicon, small amounts of carbon, and the Compositions within the part of the diagram balance iron except"for the common impurities such as sulfur and phosphorus. Usually an iron content between 5% 60% will be desired, and 55 Each section of one 20 the carbon may be allowed to rise on occasion to as high as 5% or 6%. Especially useful asprealloys and coating alloys are the compositions containing 20% to 80% copper, 20% to 50% chromium, and 15% to 40% silicon.

Examples of alloys which have=-been made according to the invention, using bar copper., highcarbon ferro-chromium containing about 65%- 68% chromium and about 4% to 8% carbon, and

ferro-silicon containing about 75% silicon, are.

listed in the following table:

%ou %si `7:,01- i %o 19.32 14.37 '36.39 3.a Remainder-gazing. 21.80 14.60 33.92 an Remainder 33.58.

(Carbon content estimated.) D I L It is to be noted that all of the alloysinthe above table may be made from relatively inexpensive materials; hence the alloys are economical to produce and are suitable for use even where cost of materials is controlling', for example, in'making inexpensive iron castings. As'm'ay be seen from the miscibility diagram, the maximum content of chromium and copper'possible in a homo.- geneous alloy .prepared from 75%- ferrosilicon,

high-carbon ferrochromium, and-copper metal,

may be obtained-in an alloy analyzing approximately chromium, 30% copper, 17.5% silicon, and 22.5% iron and carbon.

Alloys having compositions within the scope of ingot or sopas to give two homogeneous layers in 2.'A mold `coating material comprising pulverized substantially homogeneous alloy containing copper, chromium, silicon, carbon, and iron,

j in approximately tlfe proportions: 30% copper, 15

30% chromium, 17.5% silicon, not over 5% carf bon, the remainder iron.

3. A substantially homogeneous "alloy having a composition Awithin the limits: 20% to less than 40% copper, 30%v to,l5% silicon, the remainder 20 vchromium and the impurities iron and carbon;

the siliconbeing at least sulcient to make' the alloy homogeneous, the chromium being at least 20%, the carbon being present in an appreciable amount but not'over 5%,- and the iron and carbon 25 being present only in the amounts introduced Vyby the use of commercial ferrosilicon (about to silicon and the remainder iron) and of commercial ferrochromium (about 60% to 70% chromium and the remainder iron) as the sole sources of silicon and chromiumin said alloy.

. JAMES H. CRITCHETT.

than about-5%, the remainder 10"

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