US2046380A - Copper base alloys - Google Patents

Description

Patented July 7, 1936 UN'H'ED STATES PATENT OFFICE 2,046,380 ooPr'Ea BASE ALLOYS No Drawing. Application September 4, 1935,

Serial No. 39,126 i 8 Claims- (Cl. 14832) Further objects are to prevent oxidation of the alloy both during and after formation thereof.

Still further objects are to improve the handling characteristics of the alloy during casting, forging, cold working or other subsequent operations.

30 A specific object is to produce an alloy suitable for welding electrodes, contacts, electrical parts, bearings and other applications where certain desired electrical and heat conductivity coupled with high strength is required in a non- 35 ferrous material, such as for various parts in electrical apparatus, chemical apparatus, and the like and for various uses in the oil industry and other chemical and electrical industries.

Other objects of the invention will be apparent 30 from the following description taken in connection with the appended claims.

The present invention comprises the combination of elements, methods of manufacture, and the product thereof brought out and exemplified 35 in the disclosure hereinafter set forth, the scope of the invention being indicated in the appended claims.

The invention contemplates the provision of an alloy of copper, chromium, silicon, zinc and silver.

40 This alloy has a number of desirable properties which render it suitable for certain specified uses where high strength, a certain desired electrical and heat conductivity, high resistance to corrosion, high hardness, or high are snufiing ability may be required.

The completed copper-chromium-silicon-zincsilver alloy, to have the most desirable characteristics, should contain the component ingredi- 50 ents m the following ran of proportionfi 55 Copper Remainder alloying methods.

The following 5 specific compositions are listed as examples of the above composition, the properties varying somewhat depending upon the specific proportions of ingredients used. It will be apparent that for any specific application the 5 compositions can be chosen so as to provide the most suitable properties for the purpose:

aChromium 0.5% Zinc 0.5%

Silver -0.05% Silicon 0.05% Copper Balance bChromium 0.5% V

Zinc 0.25% Silver 0.50% Silicon 0.10% Copper Balance cChromium "0.5%

Zinc; o.25% Silver 1.00% Silicon 0.10.% Copper Balance d-Chromium 0.5% Zinc 1.25% Silver 0.05% Silicon 0.25% Copper Balance e-Chromium 0.50% Zinc "1.50% Silver 0.05% Silicon 2.5% Copper Balance In producing the alloy of the present invention part of the zinc,'chromium and silicon is ordinarily lost through oxidation and volatilization during melting, pouring and other handling. It is necessary, therefore, to introduce an excess of 40 these elements into the melt in order that the finished alloy will have the composition given above.

The additives may be introduced, into the copper in a variety of ways, care being taken to avoid unnecessary oxidation and volatilization of oxidizable ingredients. According to one method a copper-zinc-silver alloy is first made by usual The chromium and silicon may then be added in finely divided form, preferably combined with copper powder in the form of a briquette, and intimately mixed therewith. The chromium and silicon may also be added combined with copper to form a hardener alloy containing 10 to 25% of these ingredients. This hardener may be prepared by melting together copper, chromium and silicon under a protective atmosphere. The zinc is preferably added to the melt before the chromium in order to avoid chromium losses.

Inmany cases it will be found preferable to make a master alloy having relatively high percentages of chromium, silver, silicon, and zinc alloyed with copper. This alloy may then be diluted with copper to form lower percentage alloys.

The master alloy is a convenient form for sup.- plying the material to foundries where it may be diluted with copper to produce a finished alloy of the proportionsdesired for the application contemplated.

The zinc used in producing the present alloy is utilized in two ways. Part of it is used up as a deoxidizer and part of it remains as an ingredient in the finished alloy. In order to have 0.5% zinc in the finished alloy, for example, it is necessary to introduce 0.55% to 0.65% of zinc into the original melt. About half of the excess zinc is consumed as a deoxidizer, the zinc being converted to zinc oxide and separating as a slag. The rest of the excess is volatilized due to the low boiling point of the zinc. This volatilized zinc, when it comes into contact with the air, at a high temperature forms zinc oxide which leaves the crucible in the form of a white smoke.

Some of the chromium and silicon are likewise oxidized during the alloying process and accumulates on the top of the melt as part of the slag. In order to obtain 0.5% chromium in the finished alloy it is necessary to add approximately 1.0% chromium to the melt.

In the further treatment of the alloy after solidification it may be first heated to a temperature of 600 C. to 1050 C., and preferably above 700C. for a short time, such as from 10 to 30 minutes. After the metal has reached the desired temperature it may be cooled quickly from the high temperature (quenched). The next step is preferably to heat treat the quenched alloy at a temperature of 350 C. to 600 C. for a period of from 10 minutes to 30 hours, depending on the temperature, the percentage of hardener used, and the results desired.

The alloy may then be cold worked to obtain a cold reduction of approximately 20% and further cold reduction, up to 50% or more, may be applied to further increase the hardness. It has been found that the conductivity will not be appreciably decreased by these further reductions.

For maximum hardness and conductivity, however, it is preferable to apply a series of cold reductions alternated with relatively low temperature heat treatment, preferably within the range 400 C. to 500 C. The ,number of cold workings with intermediate heat treatments may vary with the properties desired in the finished product.

Instead of cold working the alloys they may be hot forged according. to usual methods and it will be found that the resulting hot-forged product will also have a hardness greater than the alloys of the prior art.

The finished alloy has marked heat-resistant properties whereby it is able to maintain its hardness at temperatures of 400 C. to 475 C. or higher. Thus, where the allow has been agehardened it will be suitable for applications where a combination, of high hardness, strength and heat resistance are required.

The present alloy is highly fluid in the liquid state and may be readily cast. This improvement in casting qualities over alloys such as copper-chromium appears to be due to the presence of zinc and silver which elements not only increase'the fluidity but reduce the tendency of the chromium and silicon to form a heavy oxidized film on the surface of the melt.

Since the zinc acts as a strong deoxidizer it is not necessary to add other deoxidizers commonly used, such as aluminum or magnesium, for this P p The presence of the zinc likewise tends to prevent excessive surface oxidation in the finished, solidified alloy and is particularly advantageous where they are heated to high temperatures. The surface oxidation in copper-chromium alloys is quite serious since the oxygen penetrates along the grain boundaries and tends to make the alloy brittle. In the present alloy, the chromium and silicon are protected by the zinc, which will oxidize in preference to these elements.

The alloy likewise has improved arc-snuiilng properties, due to thepresence of the zinc. This is highly advantageous for the electrical applications, suchas in the use of the alloy for pressure welding electrodes and as a contact mateheated to above 900 C. before quenching the.

water. That elevated temperature, however, is normally very conducive to grain growth, the size of the grains usually depending on the length of time the material is held at the elevated temperature. With the present alloy, containing zinc, the grain size appears to be considerably reduced from that found in other copper-chromium alloys.

In the present alloy the proportions of zinc are kept below 5% and accordingly no low-melting point phase is formed, such as that formed in alloys containing zinc in high proportions. This allows a wider range of forging or hot working temperatures and presents a decided improvement over such alloys ascopper-chromium-cam mium in which the forging range is very small.

The absence of a low-melting phase decreases the hazards in forging and the danger of loss of material during forging. It also cheapens the manufacture of forged pieces since it allows working one piece to almost finished dimensions without reheating. With copper-chro'mium-cadmium alloys the material must be reheated frequently during forging.

The silver further improves the casting qualities and also increases the temperature of recrystallization, that is, the temperature necessary to soften the alloy after it has once been hardened and cold worked. The silver may increase this temperature as much as 100 C. and does not impair the other valuable properties of the alloy, such as electrical and heat conductivity.

' The alloy can be cast in chill molds or sand cast with ease and can be mechanically worked in the. hot or cold state with the same ease as the above mentioned alloys of the prior art. It is likewise well adapted to machining.

The hardness and electrical conductivity of the all copper, characterized by high hardness, high alloys having the higher proportions of silver or silicon or both will be higher in strength and hardness but lower in electrical conductivity. The tendency of silicon to decrease the electrical conductivity is greater than that 01 the silver but its tendency to increase hardness is also somewhat greater. The silver on the other hand improves the workability of the alloy as well as its resistance to corrosion. The present alloy is suitable for certain types of resistance welding electrodes, contacts and the like due to its high strength and hardness, its arc-snuillng ability and its other electrical'characteristics but is likewise suitable for other applications where a. high strength, non-ferrous material is required for structural purposes, parts in electrical apparatus, and applications in the chemical industry, the oil industry and the like.

While the present invention, as to its objects and advantages; has been described herein as carried out in specific embodiments thereof, it is not desired to be limited thereby but it is intended to cover the invention broadly within the spirit and scope of the appended claims.

What is claimed is:

1. An alloy containing about 0.1 to 5.0% zinc, 0.05 to 10.0% silver, 0.1 to 2.5% chromium, 0.05 to 5.0% silicon and the'remainder copper.

2. An alloy containing about '0.1 to 5.0% zinc, 0.05 to 10.0% silver, 0.1 to 2.5% chromium, 0.05 to 5.0% silicon and the remainder substantially resistance to corrosion and to arcing and by the ability to maintain its hardness at temperatures in the order of 400 C.

3. An age hardened alloy containing about 0.1 to 5.0% zinc, 0.05 to 10.0% silver, 0.1 to 2.5% chromium, 0.05 to 5.0% silicon and the remainder substantially all copper, characterized by high hardnes's, high resistance to corrosion and to arcing and by the ability to maintain its hardness at temperatures in the order of 400 C. 4. An alloy containing 0.5% zinc, 0.05% silver, 0.5% chromium, 0.05% silicon and the balance copper.

5. An alloy containing 0.25% zinc, 1.0% silver,

0.5% chromium, and 0.1% silicon and the remainder copper. I v

6. An alloy containing 1.5% zinc, 0.05% silver, 0.5% chromium, 2.5% silicon and the balance copper.

'7. A welding electrode composed oi! 0.1 to 5.0% zinc, 0.05 to 10.0% silver, 0.1 to 2.5% chromium, 0.05 to 5.0% silicon and the remainder copper.

8. A welding electrode composed 01 about 0.1 to 5.0% zinc, 0.05 to 10.0% silver, 0.1 to2.5% chromium, 0.05 to 5.0% silicon and the remainder substantially all copper, characterized by high hardness and high arc-snufling ability and by the ability to maintain its hardness at temperatures in the order of 400 C. FRANZ a. KENSEL.