US1956251A - Copper alloys - Google Patents

Description

Patented Apr. 24, 1934 UNITED STATES COPPER ALLOYS William B. Price, Waterbury, Conn., assignor to Scovill Manufacturing Company, Waterbury, C onn., a corporation of Connecticut No Drawing. Application April 6, 1933, Serial No. 664,776

Claims.

This invention relates to a quaternary copper alloy consisting of copper with essential but limited proportions of tin, silicon and iron.

One important object of the invention is to 5 provide a copper alloy which while highly resistant to salt water and many acids, will have a relatively high tensile strength when hard, and yet, when soft, will have great ductility and malleability, which can be successfully worked both hot and cold and will retain its advantageous properties permanently, that is to say, will not change its characteristics with age.

The quaternary alloy of the present invention is a solid solution of tin, silicon and iron in copper,

l5 and hence must contain the ingredients other than copper in very restricted amounts, as hereinafter pointed out. For some purposes, as for example, where articles made from the alloy are to be machined, it is advantageous to add a small amount of lead to the said alloy, but this amount of lead is so small, viz: from one-half to two percent, and usually about one percent, that it does not injuriously affect the properties of the quaternary alloy of copper, tin, silicon and iron.

In the usual course of manufacture, it is difli- 'cult and in most cases impossible, to avoid the introduction of some impurities into the alloy. It is very important, however, with the present alloy, to keep the impurities very low so that in no case shall the total amount of impurities exceed one percent, and it is highly important that zinc be avoided entirely, as the alloy will be seriously injured if more than a mere trace of zinc be present. Also it is important to avoid the use of phosphorus, or at least to keep it as low as can be done in practice.

Therefore, in that embodiment of the invention in which no lead is used, at least 99 percent of the final product consists of the quaternary alloy of copper, tin, silicon and iron, and the said final product must be substantially free from zinc and phosphorus.

In that embodiment of the invention where the final product contains some lead in order to make it more convenient for machining, the quaternary alloy should form not less than 98 percent of the final product, lead should form not more than 1 percent of the final product, and all other ingredients, generally considered as impurities, consisting of unwanted metals or metalloids must never exceed 1 percent and must not include zinc or phosphorus, or at least not more than a mere trace.

Therefore, considered broadly, at least 98 percent of the final product consists of the quaternary alloy of copper, tin, silicon and iron, and the ranges of proportions must be very limited. The tin must notbe less than 0.50 percent nor more than 1.5 percent, the silicon not less than 1 percent nor more than about 3 percent, and the iron not less than 0.75 percent nor more than 1% percent, these figures referring to the total of the four metals in the quaternary alloy. Copper forms the balance of the quaternary alloy. Of course, where a composition having these proportions is figured as 98 percent of the final alloy product, the proportions of the copper, tin, silicon and iron in the final product are slightly less than givenabove, varying according to the proportion of the said quaternary compound in the final product.

In the best embodiment of the invention heretofore made in accordance with the invention and containing no lead, the mix was prepared to give This mix was-melted and cast in a mold to give a rod 1% inches indiameter. this rod when analyzed showed the following composition:

Percent Copper 94.67

Tin 1.18

silicon 2.73 Iron 1.27

Impurities by difference 0.15

In this particular instance the impurities were found to be manganese and nickel which had been absorbed from the crucible lining which had been previously used in casting different alloys and evidently had retained unwanted metals.

It will be noted that in this case the copper, tin, silicon and iron formed about 99.85 percent of the final product. The structure of the rod casting was unusually sound as it was free from gas and blow holes. Under the microscope it was apparent that the alloy was a solid solution.

The cast bar was then processed according to the following schedule:

Annealed 780 C.

. Overhauled 10%.

Rolled to 1" (rod rolls).

Annealed 780 C.

Rolledto 11/16" (rod rolls).

Annealed 780 C. It was then taken to the rod mill where it wa cleaned in. the bichromate. dip.

The gate end of The following schedule was followed in the rod mill;

Drawn to .625".

Annealed 780 C.

Cleaned in bichromate.

Drawn to .500.

Drawn to .438".

Annealed 780 C.

Cleaned in bichromate.

Drawn to .335".

Annealed 780 C.

Cleaned in bichromate.

The .335" material-was then taken to the wire mill, drawn to 0.257", given a BC anneal, cleaned in bichromate and thrashed.

From this point on, the material was drawn and finished 1#, 2#, 3#, 4#, 5#, 6#, 7#, 8#, 9# and 10# hard, in accordance with the regular wire mill schedule. Test pieces of the wire having the diameter 0.257 to .081 were taken in the annealed stage and at the difierent stages of hardness, and these tests are set out in the following table, in comparison with test pieces of wire made from an old alloy of copper, silicon and iron containing no tin and showing, on analysis, the following composition:

The test pieces of the old alloy were made by the identical steps of annealing, rolling, cleaning, etc., as the new alloy.

In the following tables the old alloy is designated as A and the new alloy as B:

Table I Ultimate tensile Yield 1 strength, lbs. sq.

q. n. in Description Old New Old New A B A B Soft on .257" 34, 000 31, 000 64, 000 67, 500 600 3, 000 76, 000 ,000 200 000 112, 900 000 123, 600 000 137, 500 0 143, 600 000 146, 100 000 155, 700 000 158, 500 000 162, 400 000 Table II Elongation, per- Reduction of area, oentage in 2 percentage Description Old A New B Old A New B Soft on .257" 53 56 74 76 hd. .243 36 37 74 1# 11d. .229. 18 17 67 64 8. 5 9 62 66 6. 5 7 58 55 5. 5 5 56 50 4. 5 4. 5 55 56 4. O 3. 5 55 57 3. 5 4 54 56 3. 5 3 53 54 The tables show that while the new alloy (B) in the soft condition has a lower yield point than the old alloy (A), it has about 5 /2 percent higher ultimate strength than the old alloy, and, strange to say, this increase in strength is obtained without any loss of ductility such as would usually be expected. At No. 1 hardness the new alloy has about the same yield point as the old alloy, but at any condition of hardness above or below No. l the new alloy has a higher yield point or limit of elasticity than the old alloy, and the difierence in favor of the new alloy is proportionately greater as the hardness increases above No. 1.

The ultimate tensile strength of the new alloy is greater than that of the old alloy and the difference is greater with the increase of hardness, the percentage increase varying from about 3% percent to about 10 percent.

It is to be noted that these advantages are obtained in the new alloy without any loss of ductility, the percentage of elongation and reduction of area being substantially the same in the two alloys. A further important advantage of the new alloy is its very high resistance to corrosion by salt water and many acids. In this respect, it is unique, since under long time tests with either salt spray or a 20 percent solution of hydrochloric acid at normal temperatures the loss is exceedingly small, the penetration being of the order of 23 x 10- to 28 X 10 Another advantageous property of this alloy is that it retains its advantageous properties permanently, that is to say, will not change its characteristics with age, so far as shown by tests up to the present time.

Tests showed that this material can be worked both hot as well as cold. An important advantage of the alloy is that at higher temperatures, for example, around 500 'F., such as occur in use, the tensile strength and elastic limit although somewhat lower, are still high enough for practical use, thus making the material particularly suitable for use under such relatively high temperatures as are required in practice.

The alloy of the present invention has been found to be particularly suitable for condenser tubes, as well as sheets, rods, bolts and nuts for marine use, because it has a tensile strength comparable with that of mild steel, while at the same time it is as resistant to corrosion as copper. While the percentage composition of the alloy in order to achieve the desired results should not depart materially from that given as the ideal, a variation of proportions within the limits hereinbefore stated will result in the production of alloys retaining substantially the advantageous properties hereinbefore set out.

It will be observed that the ranges of proportions are so selected as to insure the production of a true quaternary alloy of copper, tin, silicon and iron, that is an alloy which is a solid solution of tin, silicon and iron in the copper. This solid solution is not destroyed by the use of a small amount of lead and hence lead within the limits stated may be added where the alloy product is to be extruded or machined, or both.

In every case it will be found that the quaternary alloy having a composition within the ranges stated has a higher tensile strength, and better ductility than a ternary alloy made from the same metals except the tin, and having substantially the same percentage composition as the quaternary alloy with tin with which it is compared.

. the quaternary alloy product will, of course,

not have the same tensile strength as the quaternary alloy with lower percentage of copper, but in every case the tensile strength will be materially greater than the ternary alloy not having tin, but with the same percentage of copper.

For example, a quaternary alloy product having 97.59% of copper, 0.74% tin, 1.06% silicon and 1.19% iron, in its soft condition gave a tensile strength of 49,900 pounds per square inch and 45% elongation in 2 inches, While a ternary alloy of copper, silicon and iron having about the same percentage of copper, gives only about 44,000 pounds.

At the lower limit of copper, the tensile strength is increased materially and while the ductility is decreased it still remains entirely satisfactory for manufacturing purposes. For example, an alloy containing 93.66% copper, 1.58% tin, 3.52% silicon and 1.19% iron, in its soft condition gave a tensile strength of 77,100 pounds per square inch, and 49% elongation in 2 inches. On rolling the tensile strength rapidly increased, so that at No. 2 hardness it was 122,100 pounds per square inch with 7 elongation in 2 inches.

What is claimed is:

1. A copper alloy having substantially the following composition? l 'ercent Silicon 1.00 to 3.25

Iin 0.50 to 1.50

Iron 0.75 to 1.25 Impurities 0.15 to 2 Remainder, to make 100%, copper.

2. A copper alloy having substantially the following composition:

, Percent Silicon (about) 3 Tin (about) 1 Iron (about) 1 Impurities (about) 2 Remainder, to make 100%, copper.

3. A copper alloy, having substantially the following composition:

4. A copper alloy having substantially the following composition:

Percent Tin 1 Silicon 3 Iron 1 Lead 1 Balance copper and not to exceed l. percent of impurities.

5. A copper alloy having substantially the composition of the following formula:

Percent Silicon 1.00 to 3.25 .50 to 1.50 Iron .75 to 1.2?

Impurities Remainder substantially copper.

WILLIAM. PRICE.