US2798826A

US2798826A - Method of heat treating nickel bearing aluminum bronze alloys

Info

Publication number: US2798826A
Application number: US583627A
Authority: US
Inventors: John F Klement
Original assignee: Ampco Metal Inc
Current assignee: Ampco Metal Inc
Priority date: 1956-05-09
Filing date: 1956-05-09
Publication date: 1957-07-09
Anticipated expiration: 1974-07-09

Description

United States Patent METHOD OF HEAT TREATING NICKEL BEARING ALUMHNUM BRGNZE ALLOYS John F. Klement, Milwaukee, Wis, assignor to Arnpco Metal, Inc., Milwaukee, Wis., a corporation at Wrscousin No Dir-swing. Application May 9, 1056, tierial No. 583,627

4 Claims. (Cl. 148-==-1) This invention relates to a method of heat treating a nickel bearing aluminum bronze alloy.

The metallographic structure of an aluminum bronze alloy is controlled generally by the aluminum content. An alloy having an aluminum content below 7 and without appreciable amounts of other alloying elements has an alpha phase structure, while an aluminum content of 7.5% to 10.5% will produce the alpha and/or beta phase depending on the heat treatment to which the alloy is subjected. An aluminum content in excess of about 10.5% will generally result in only a beta phase structure. The addition of aluminum absorbing elements, such as nickel, manganese or the like, would require an aluminum range of about 8.5% to 11.5% in order to obtain the duplex alpha and beta phase.

The alpha phase provides the aluminum bronze alloy with excellent cold working strength and imparts ductility to the alloy, while the beta phase provides excellent hot working properties and imparts hardness to the alloy.

If a nickel-bearing aluminum bronze alloy, having an aluminum content of 8.5% to 11.5% is quenched from the solidus temperature of about 1870 F. all beta phase results. solidus temperature, a structure of about 90% alpha and 10% beta is produced.

An object of the present invention is to control the cooling rate of the aluminum bronze alloy in order to obtain a metallographic structure having about 50% to 60% alpha and the remainder of beta in the cooled alloy. It has been found that this proportion of 50% to 60% alpha provides an alloy having the most desirable combination of strength and ductility. An alpha to beta ratio such as this is particularly useful in a weld deposit employed to weld thick sections of aluminum bronze plate, for this ratio tends to eliminate crater cracking and base metal rupture.

The general composition of the aluminum bronze alloy to be subjected to the treatment of the present invention is as follows, in weight percent:

Percent Aluminum 8.5l0.5 Iron 3.0-6.0 Nickel 3.0-6.0 Manganese 0.5-1.5 Copper Balance A specific example of the composition of the alloy falling within the above range is as follows:

Percent Aluminum a- 9.5 lron 4.0 Nickel 4.0 Manganese 1.0 Copper Balance The aluminum content set forth above provides an alloy having high tensile strength and yield strength coupled with good elongation. is controlled by the aluminum content as well as the iron,

However, if the alloy is slowly cooled from the The relationship of alpha to beta ICQ nickel and manganese. The iron and nickel increase the strength of the alloy, and the iron also produces a fine, tough grain structure, while the manganese aids in improving the fluidity and soundness of the alloy.

The procedure employed to bring about the desired alpha beta ratio is to cool the alloy from the solidus temperature of about 1870 F. down to about 1300 F. at a cooling rate of 400 F. to 550 F. per minute, or preferably about 500 F. per minute. When the temperature of the alloy reaches about 1300 F. the rate of cooling is reduced and the alloy is cooled down to a temperature of about 800 F. at a rate of F. to 150 F. per minute and preferably about F. per minute. The alloy is then cooled from 800 F. to room temperature at a rate of 25 F. to 75 F. per minute and preferably about 50 F. per minute. This controlled rate of cooling results in an aluminum bronze alloy having between 50% and 60% alpha in the metallographic structure.

If the alloy is cooled at a rate greater than about 550 F. per minute from the solidus temperature down to about 1300 F. retained beta is produced in the alloy which is extremely hard. The retained beta destroys the ability to form primary alpha so that the alpha coming out when the alloy is cooled from 1300 F. down to 800 F. will be acicular and the alloy will tend to be brittle.

If the cooling is too slow, less than about 450 F. per minute from the solidus temperature to about 1300 F., an excessive amount of grain growth results in the alloy which is undesirable. Therefore, it has been found that the cooling rate from the solidus temperature down to about 1300 F. should be maintained within the 400 F. to 550 F. per minute range in order to provide the proper start of nucleation.

If the alloy is cooled more rapidly than about 150 F. per minute from about 1300 F. down to about 800 F., the proper alpha size and distribution is not: brought out. This results in the alpha particles being too small and the alloy tends to become brittle. If the alloy is cooled at a slower rate than about 75 F. per minute from about 1300 F. to about 800 F. the kappa phase results and an A cooling rate in excess of about 75 F. per minute when cooling from about 800 F. down to room temperature produces stresses in the alloy which cause Warpage, rupture or sensitivity to stress corrosion cracking. On the other hand, if the alloy is cooled too slowly, less than about 25 F. per minute, from about 800 F. down to room temperature the beta transforms into eutectoid which again results in a brittle alloy.

On cooling from the solidus temperature of about 1870 F. the beta phase appears and this has excellent hot working characteristics. In the neighborhood of 1600 to 1700 F. there will be approximately 90% beta and at this temperature the alloy will contract and expand with ease rttlue to the excellent hot working characteristics of the eta.

As the cooling progresses the 10%. alpha phase is enlarged to approximately 30% at about 1300 F. and increases further to about 50% alpha at about 800 F. The beta phase controls the alloy as far as hot working is concerned and below about 800 F. the strength and ductility of the alpha phase will control the alloy down to room temperature.

The metallurgical characteristics of the alpha and beta constituents make the ratio workable. At elevated temperatures the beta has excellent hot working properties and a low Brinell hardness of approximately 80 Brinell. As the alloy is cooled belowabout 800 F. the beta will increase in hardness until the temperature of the alloy has reached approximately F. At this latter temperature the alpha has a hardness of approxi mately 80' Brinell. When the alloy is cooled to room temperature, the alpha developed by the controlled cooling has the ductilityneccssary to deform, while the beta has reached a maximum hardness of approximately 250 Brinell and provides the alloy with strength.

' An example of the invention in the welding of a thick plate of an aluminumbronze, alloy is as follows:

The base plate hada composition by weight of:

The heli-arc welding process was used to make the weld with a current of about 175 amperes. The temperature of the weld deposit was checked by temple sticks and the rate of cooling maintained within the aforementioned ranges by use of a torch anneal to obtain a final metallographic structure of about 50% alpha and 50% beta.

The cooled weld deposit had a composition by weight of:

Percent Aluminum 8.5 Iron 4.5 Nickel 4.5 Manganese 1.0 Copper Balance The weld deposit had a tensile strength of 125,000 p. s. i., a yield strength of 60,000 p. s. i., an elongation in 2 inches of and a Brinell hardness of 200.

A slight variation in the weld rod composition may be necessary when Welding heavier or lighter sections of base metal. The heavier sections which afford a more rapid cooling should have an aluminum content of approximately 9.25%, while very thin sections will cool more slowly and can have an aluminum content of about The ratio between beta and alpha that has been found to be most satisfactory for the weld deposit during welding of either light or heavy sections, is a 9 to 1 ratio be tween beta and alpha at 1650 F. At 1350 F. a ratio r of beta to alpha of 7 to 3 is most desirable and at 850 F. the ratio which produces the best weld deposit is approximately a 1 to 1 ratio between beta and alpha. At room temperature, the most satisfactory ratio of beta to alpha is about 4 to 6. In other Words, approximately 60% alpha and beta at room temperature produces the toughest and soundest weld deposits.

The method of weld deposit is not important, consequently carbon arc, metallic arc, consumable electrode and inert gas are have all been employed and satisfactory deposits will result if the proper ratio of alpha to beta is maintained during cooling. The ratio is controlled by the weld wire deposit and the technique of cooling and torch annealing to maintain the proper rate of cooling is essential. Through experimentation on the thickness of the section welded, the speed of travel of the weld wire, and the current density, a welding technique can be developed using torch annealing to maintain the aforementioned cooling rates to bring about the desired alpha-beta relationship.

The thermal treatment of the invention can be applied to forgings, castings, rolled articles, etc. fabricated from the aforementioned composition as well as weld deposits. With a forging, for example, the treatment can easily result in a tensile strength of 110,000 p. s. i., a yield strength of 55,000 p. s. i., an elongation in 2 inches of 20% and a Brinell hardness of 190.

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 regarded as the invention.

I claim:

1. A method of heat treating a duplex phase aluminum bronze alloy of the class described to produce a controlled ratio of alpha phase to beta phase in the metallographic structure, comprising; heating the alloy to a temperature above the solidus temperature thereof; cooling the alloy from the solidus temperature to a temperature of about 1300 F. at a rate of 400 F. to 550 F. per minute; cooling of the alloy from about 1300 F. to about 800 F. at a rate of from 75 to 150 F. per minute; and cooling the alloy from about 800 F. to room temperature at a rate of 25 to 75 F. per minute.

2. A method of heat treating a duplex phase aluminum bronze alloy to produce a controlled ratio of alpha phase to beta phase in the metallographic structure, said alloy having the following composition by weight:

Percent Aluminum 8.5 to 10.5 Iron 3.0 to 6.0 Nickel 3.0 to 6.0 Manganese 0.5 to 1.5 Copper balance said method comprising; heating the alloy to a temperature above the solidus temperature thereof; cooling the alloy from the solidus temperature to a temperature of about 1300 F. at a rate of 400 F. to 550 F. per minute; cooling of the alloy from about 1300" F. to about 800 F. at a rate of from 75 to 150 F. per minute; and cooling the alloy from about 800 F. to room temperature at a rate of 25 to 75 per minute.

3. A method of heat treating a duplex aluminum bronze alloy to produce a controlled ratio of alpha phase to beta phase in the metallographic structure, said alloy having the following composition by weight:

Percent Aluminum 8.5 to 10.5 Iron 3.0 to 6.0 Nickel 1 c 3.0 to 6.0 Manganese 0.5 to 1.5 Copper balance heating the alloy to a temperature above 1800 F, cooling the alloy from about 1800 F. to about 1300 F. at a rate of about 500 F. per minute, cooling the alloy from about 1300" F. to about 800 F. at a rate of about F. per minute, and further cooling the alloy from about 800 F. to room temperature at a rate of about 50 F. per minute to obtain about 50% to 60% alpha phase and the remainder beta phase in the metallographic structure.

4. A method of heat treating a duplex aluminum bronze alloy to produce a controlled ratio of alpha phase to beta phase in the metallographic structure, said alloy having the following composition by weight:

. Percent Aluminum 8.5 to 10.5 Iron 3.0 to 6.0 Nickel 3.0 to 6.0 Manganese 0.5 to 1.5 Copper balance heating the alloy to a temperature above 1800 F. to provide a metallographic structure having about 10% alpha and the remainder beta, cooling the alloy rapidly to provide about 30% alpha and the remainder beta at References Cited in the file of this patent about 1300 F., further cooling the alloy at a reduced v d b th C D 1 e t rate to provide about 50% alpha and the remainder beta Alummum ronze Issue y e Opper eve 0pm n d ,N 31 1939 31-57. at 800 F., and thereafter cooling the alloy slowly to room Assoc (Lon on) o pages temperature to provide about 60% alpha and the re- 5 mainder beta therein.

Claims

2.A METHOD OF HEAT TREATING A DUPLEX PHASE ALUMINUM BRONZE ALLOY TO PRODUCE A CONTROLLED RATIO OF ALPHA PHASE TO BETA PHASE IN THE METALLOGRAPHIC STRUCTURE, SAID ALLOY HAVING THE FOLLOWING COMPOSITION BY WEIGHT: