US2944889A

US2944889A - Aluminum bronze alloy containing chromium and having improved wear resistance

Info

Publication number: US2944889A
Application number: US697537A
Authority: US
Inventors: John F Klement
Original assignee: Individual
Current assignee: Individual
Priority date: 1957-11-20
Filing date: 1957-11-20
Publication date: 1960-07-12
Anticipated expiration: 1977-07-12

Description

' nite This invention relates to an'aluminum bronze alloy and more particularly to an aluminum bronze alloy having improved corrosion resistance, toughness and wearres'istance.

rates atent Aluminum bronze alloys have for years been used :as

dies for forming and --drawing operations for a large group of sheet and plate alloys, such as stainless steel, aluminum, nickel, titanium, mild steel and some copper zbase alloys. Aluminum bronze alloys used '-'in die applications possess-the properties of good corrosion resistance, wear resistance and non-galling against many wrought materials. I

The aluminum bronze alloys which in the past have shown-the optimum properties for deep drawing dies are those that contain approximately 14% aluminum, a small amount of'iron and the balance copper. An alloy of this *type has'good corrosion resistance and non-gelling properties. 'However, under heavy use in die application, this alloy sometimeswea'rs undesirably fast so that close dimensional tolerances cannot be maintained because of the wear that occurson the die surface.

"The present invention is directed to an aluminum bro'nze alloy having the non-galling properties characteristic of "aluminum bronze alloys but having greatly improved corrosion -resistance, 'wear resistance and toughness. This is accomplished by the addition of a small amount of chromium to the alloy which renders the alloy less susceptible :to eutectoid transformation and its em- ,hrittling structure.

' The alloy .of the invention'has the following general composit on by Weight 1 Percent Aluminum 13.0-20.0

Iron r, 1.0-8.0 Chromium 0.5-3.0 Copper Balance v A specific illustration of the composition falling within the above range is as follows in weight percent:

Percent Aluminum 13.01 Iron 4.13 Chromium 1.51 Copper 81.35

The wear resistance of the alloy of the invention is substantially improved over that of aluminum bronze alloys which do not contain the chromium. The data contained .in the following table shows the improved wear resistance of the alloy of the invention over similar aluminum bronze alloys which do not contain the chromium addition:

Patented July 12,1960

The draws set forth in the above table were made on production presses drawing stainless steel parts for barrels and the results clearly show the superiority of the present alloy in regard'to wear resistance over that of the other alloys which do .not contain the chromium addition. As-shown in the table, 134,-493 :draws were made with the die fabricated from the :present alloy before it was necessary to redress the die due to loss of dimensional tolerance caused :by wear, 'while the alloy samples 1 and 2, which did not contain the chromium addition, had to be redressed after only 77,000 and 93,190 draws, respectively.

The increase in thewear resistance of the alloy with the addition of chromium ;is particularly surprising since the hardness o'f-the alloy containing chromium is less than the hardness of the alloys which do not contain chromium, as shown in the table. With'the decrease in hardness, it would be expected that the wear resistance of the alloy would be correspondingly decreasedg'how ever, the opposite is true with respect to the alloy of the invention.

The alloy of the invention containing about 13% aluminum, 4% iron, 1.5% chromium and the balance copper can be cast statically or centrifugally to produce a fine grain tough structurehaving a hardness of approximately 32 Rockwell C. The hardness of the alloy can be varied within the range of 25 Rockwell 'C'to 55 Rockwell C depending upon the specific aluminum and chromium contentin the alloy.

The alloy with the above composition has unusual compressive strength and test specimens have been as high as 200,000 p.s.'i. inult'imate compression. A centrifugally cast alloy of the above composition'ha-s a tensi'lestrength of about 100,000 p.s.i., while a statically 'cast alloy'has a tensile strength of'about 80,000 p.s.'i.

The 'metallographic structure of the alloy consists essentially of gamma two phase which is uniformly distributed in a matrix of beta. An intermetallic compound composed of iron, aluminum, copper and chromium exists in rosette and spheroid particles and is uniformly disresistance and also makes the alloy less susceptible :to

the eutectoid transformation. The eutectoid structure consists of alpha phase plus gamma two phase formed from the transformation-dccomposition of the beta phase. This transformation occurs at temperatures below 1050 F. in aluminum bronze alloys and the resultant eutectoid structure is brittle and possesses low ductility and poor machinability.

The chromium also provides a finer grain structure which enables the alloy to be machined to a better finish.

In order to obtain optimum properties, the metals used with the alloy should be of high quality. Electrolytic or wrought fire refined copper, high purity aluminum, low carbon iron and high purity chromium are preferred to be used. It hasbeen found that a very satisfactory method of obtaining the desired uniformity in the alloy is by using a double melting procedure whereby a pre-alloy is made. The most satisfactory pre-alloy is one that has approximately 50% aluminum, 20% copper, 20% iron and 10% chromium. The chromium can be added to the pre-alloy in the form of powdered briquets containing 35 chromium and the balance copper.

The melting procedure employed in making the prealloy is such that some copper, along with the iron and chromium, is placed into the crucible and melting begun. When the copper starts to melt, the iron and other additives are slowly dissolved into the copper during the period when aluminum is added to form an exothermic re- 7 action which helps to dissolve the higher melting point chromium addition. This form and is ready to use for the final alloy.

Alternately, instead of adding the chromium to the pre-alloy, the chromium can be added to the final alloy. In" this case, an alloy of chromium and 90% copper is added to the final alloy. v

To establish complete uniformity of the micro-strucpre-alloy is then cast into ingot ture and hardness, the alloy is heattreated at ,an elevated temperature in the range of 1050 F. to 1400 R, such as about 1150 F. Small castings of simple shapes of this alloy can be placed directly into the heat. treating furnace at temperature. Large massive castings-or intlicate pes are preheated in the furnace at about 400 1.

20 F. per hour per one inch of section thickness. This 7 rate is conveniently obtained by fan air cooling.

Internal stresses created within castings during machining or other finishing operations, during weldrnents, or from metal overlays on base metals, are usually re.- moved depending on the future application of the part. These stresses are removed by a stress relief heat treatment.

To stress relieve the alloy, the alloy is heated;to a temperaturebelow 600 F. and maintained at this temperature for a period up to 3 hours per one inch of section thickness. The article is then cooled to room temperature. More specifically, to stress relieve the alloy, the alloy is heated to a temperature of 500 F. and maintained at this temperature for approximately 2 hours per one inch of section thickness.

The alloy of this invention can be used to produce articles that require corrosion resistance, toughness and exceptional wearing properties. the form of deep drawing dies,

wear guides; forming rolls, etc.

The articles may take The alloy can. also be extruded into weldrods or weld Y 4 thecopper aluminum iron alloy to be used as die materials greatly improves the resistance to surface oxidation, improves the toughness andwear resistance of the alloy and makes it less susceptible to eutectoid embrittlement.

Various modes of carrying .out the invention are contemplated as being within the scope of the following claims particularly pointing out and {distinctly claiming the subject matter which is regardedas the invention.

1. An aluminum-bronze alloy consistingessentiallyof 13.0% to 20.0% aluminum,from 1.0% 'to'8.0% 'i'r'ori, from 0.5% to 3.0% chromium a'ndtherbalance beihgsubstantially copper, said alloy being characterized by having excellent corrosion resistance and having improved toughness and wear resistance.

2. An aluminum bronze alloy consisting essentially of 13.0% to 20.0% aluminum, from;-1.0% .to 8.0% iron, from 0.5 to 3.0% chromium and the balance being substantially copper, sai-d alloy having a hardness in the range of 25 to Rockwell C and being characterized by having improved corrosion resistance, toughness and wear resistance. v

3. An aluminum bronze alloy having improvedcorrosion resistance,'toughness and wear resistance, consisting essentially of 13.01% aluminum, 4.13% iron, 1.51% chromium and the balance copper.

4. An aluminum bronze alloy welding electrode, .consisting essentiallyof l3.0%' to -20.0% aluminum, from 1.0% to 8.0% iron, from 0.5 to 3% chromium and the balance being substantially copper.

' 5. A. die for use in working a metal selected from the group consisting of stainless steel, aluminum, nickel, titanium, mild steel and copper base alloys, said die being fabricated from au aluminum bronze alloycon sisting essentially of 13.0% to'20.0% aluminum, from 1.0% to 8.0% iron, from 0.5% to 3.0% chromium and the balance being substantially copper, said alloy having a hardness in the range of 25 to 55 Rockwell C and being characterized by having improved corrosion resistance, toughness and wear resistance.

References Cited in thefile of this patent UNITED STATES PATENTS 537,404 f Great Britain j. Sept. 18, 1940

Claims

1. AN ALUMINUIM BRONZE ALLOY CONSISTING ESSENTIALLY OF 13.0% TO 20.0% ALUMINUIM, FROM 1.0% TO 8.0% IRON, FROM 0.5% TO 3.0% CHROMUIM AND THE BALANCE BEING SUBSTANTAILLY COPPER, SAID ALLOY BEING CHARACTERIZED BY HAVING EXCELLENT CORROSION RESISTANCE AND HAVING IMPROVED TOUGHNESS AND WEAR RESISTANCE.