US2357450A - Aluminum alloy - Google Patents

Description

Patented Sept. 5, 1944 ALUMINUM ALLOY Walter Bonsack, South Euclid, Ohio, assignor to The National Smelting Company, Cleveland, Ohio, a corporation of Ohio No Drawing. Application January 18, 1941, Serial N0. 375,043

6 Claims.

This invention relates to alloys, and more par-.

er exposure to prolonged high temperatures, are

especially desirable for the manufacture of castings, such as pistons or other parts, for use in internal combustion engines and the like,

Aluminum-silicon alloys containing suitable amounts of manganese and magnesium have been used in the production of pistons and the like, In these alloys, as the proportion of silicon is increased, the thermal expansion of the alloy is decreased, and the hardness and wear resistance of the alloy are increased. Their Wear resistance, however, has not been as great as usually desired and the expansion has not been low enough. This is because it has usually been necessary to have the percentage of silicon less than about as higher amounts of silicon have decreased the machinability and fatigue resistance of the alloyto a substantial degree.

It is an object of the present invention to provide a castable aluminum alloy having greater hardness, improved wear resistance and good machinability.

It is a further object of the invention to provide a machinable alloy having improved wear resistance, relatively high strength and fatigue resistance, and a relatively low thermal expansion, and which will retain these properties when exposed to relatively high temperatures, such as those encountered in the operation of internal combustion engines.

In my prior application, Serial No. 366,453, filed November 20, 1940, of which this application is a continuation-in-part, is disclosed an aluminum base alloy containing silicon, magnesium, manganese, iron and copper,

It ,has now been found that the above objects may be accomplished to a greater extent by an aluminum base alloy containing about 18% to 35% silicon, about .1% to 1% magnesium, about 1% to 5% copper, about .6% or .7% to 2% iron, and proper proportions of any two or more hardening metals of the group consisting of maganese,

nickel, chromium, cobalt, titanium, columbium,

molybdenum, tungsten, vanadium, zirconium, cerium, tantalum and boron in a total amount of .5% to 5%.

Silicon, which aside from aluminum is the predominant alloying ingredient, may be present in the alloy within the limits of 18% to 35%; but, silicon is preferably present in an amount from about 20% to 30% of the alloy. Silicon increases the hardness and wear resistance of the alloy and decreases its thermal expansion. Without suitable quantitiesof the other above mentioned constituents, however, it has a tendency to crystallize into relatively large crystals and to decrease the machinability of the alloy,

Iron tends to harden the alloy, decreases its thermal'expansion, increases its machinability, and aids in maintaining the properties of the alloy at relativelyhigh temperatures. ably present within the amounts of about 1% to 1.5%, although an alloy having very desirable properties may be obtained with 2% or so, and with as little as about .6% or .7 iron. Iron like silicon, however, has the property of tending to crystallize into relatively large crystals in the ab sence of hardening metals of the groups set out above.

The members of the above group each tend to harden the alloy, decrease its-thermal expansion and increase its machinability. They are also beneficial in that they tend to maintain the desirable properties at relatively high temperatures, such as those encountered in internal combustion engines and the like,

Of the metals of the above group, manganese, nickel, cobalt and chromium are usually most desirable for the reason that they are more readily available and are more easily alloyed with the aluminum, These four elements function in aluminum alloys as hardeners and have relatively no function as grain-refiners.

The remaining hardening metals of the group, namely columbium, molybdenum, tungsten, vanadium, zirconium, cerium, titanium, tantalum and boron are generally recognized as being both hardeners and grain refiners in aluminum alloys.

of the following elements: about 2% to 1% manganese; about .2% to 1.5% nickel; about .1% to .5% chromium; about .1% to .5% cobalt; about .01% to 25% columbium; about .1% to .5%

molybdenum; about .1% to .5% tungsten; about .1% to .5% vanadium; about .01% to 25% zir- It is preferconium; about .01% to .25% cerium; about .05% to .3% titanium; about .1% to .3% tantalum; and about .005% to .l% boron.

Since each of these hardening metals may tend to crystallize in somewhat difierent shapes, finer crystals and more desirable properties may be obtained in alloys havinga large number of these metals present, each in relatively smaller amounts than in alloys having the same total effective amount of a lesser number of these metals. Thus, when each of the above ten members of the group is present in an amount such as one-fifth of its maximum range'above enumerated, somewhat more desirable properties are obtained than .1 when two of the element are present in amounts used to obtain substantially th same properties in the alloy as when a smaller amount of iron is present.

Th total quantity of the hardening metals in the above group should be less than and should be present in an amount of about .5% or more, and preferably 1% or more of the alloy. In the preferred alloys having manganese, chromium and nickel, with one of the grain refiners 1 and hardening group, such as titanium, present, the preferred amount of manganese is about .'7%; the preferred amount of nickel is around 1%; the preferred amount of chromium is around .2%;

and the preferred amount of titanium is about Magnesium, as well as improving the hardness and tensile strength of aluminum-silicon alloys, increases the elastic properties of the alloy and also improves the machinability, and is preferably present in amounts of about 13% to about .8%, although as much as 1%, or even somewhat more, may be used, and an appreciable effect is obtained with as little as about .l%.

Copper is beneficial in the alloy in that it aids in increasing its fatigue strength and further improves its machinability. The preferred amount of copper is 1.5% to 2.5%, but-the desirable properties of the alloy are obtained when copper is present from about 1% to about 5%.

Example I Alloys especially desirable for making pistons preferably contain: 20% to 30% silicon; .3% to .8% magnesium; 1.5% to 2.5% copper; about 1% to 1.5% iron; about .7% to 1% manganese; around 1% or 1.5% nickel; about 2% chromium; and .l% to 2% titanium. If desired, part of the titanium may be substituted by a small amount of tantalum or boron, which also act as grain refiners.

Such an alloy may be readily machined with tools now available; it has relatively low expansion; it is relatively hard; and it has relatively great wear resistance. It also has comparatively high heat conductivity, excel-lent fatigue strength and elastic properties, and maintains was 17.35 10 these over long exposures at high temperatures,

Example II A piston alloy containing 1.8% copper, 4% magnesium, 23% silicon, .8% iron, .5% manganese, .5% nickel and .05% titanium was chill cast into test bars, which were heat treated for twelve hours at 355 F. The tensile strength of the test bars was between 31,200 and 33,900 lbs/sq, in; the Brinell hardness was between and and the coeflicient of thermal expansion This alloy had excellent fatigue strength and elastic properties, had relatively great wear resistance and maintained desirable properties at relatively high temperatures.

The alloys of the present invention are particularly desirable for the production of castings, and the castings are susceptible to the usual heat treatments and have tensile strengths and hardnesses substantially improved thereby.

Furthermore, it is to be understood that various modifications of the alloys disclosed herein can be made without departing from my invention as denfied in the appended claims.

What I claim is:

1. An aluminum base alloy having a relatively low coefficient of thermal expansion and relatively great wear resistance, containing about 18% to 35% silicon, about .l% to 1% magnesium, about 1% to 5% copper, about .'7% to 2% iron, and about .5% to 5% of at least two hardening metals selected from the group consisting of about .2% to 1% manganese, about .2% to 1.5% nickel, about .l% to .5% chromium, about .l% to .5% cobalt, about .1% to .5% molybdenum, about .1% to .5% tungsten, about to .5% vanadium, about .01 to .25% columbium, about 01% to .25% zirconium, about .0l% to .25% cerium, about 05% to .3% titanium, about .1% to .3% tantalum, and about 005% to .l% boron, with the balance substantially all aluminum and minor impurities.

2. An aluminum base alloy having a relatively low coefiicient of thermal expansion and relatively great war resistance, containing about 20% to 30% silicon, about .3% to 1% magnesium, about 1.5% to 2.5% copper, about .'7% to 1.5% iron, and about 1% to 5% of at least two hardening metals selected from the group consisting of about .2% to 1% manganese, about 2% to 1.5% nickel, about .l% to .5% chromium, about .1% to .5% cobalt, about .1% to .5% molybdenum, about .1% to .5% tungsten, about .1% to .5% vanadium, about .01% to .25% columbium, about .01% to .25% zirconium, about 01% to .25% cerium, about 05% to .3% titanium, about .1% to .3% tantalum, and about .005% to .l%. boron, with the balance substantially all aluminum and minor impurities.

3. An aluminum base alloy having a relatively lected from the group consisting of about .2% to 1% manganese, about .2% to 1.5% nickel, about .1% to .5% chromium, about .1% to .5% cobalt, about .1% to .5% molybdenum, about .1% to .5% tungsten, about .1% to .5% vanadium, about .01% to .25% columbium, about .01% to .25% zirconium, about .01% to .25% cerium, about .05% to .3% titanium, about .1% to .3% tantalum, and about .005% to .1% boron, with the balance substantially all aluminum and minor impurities.

4. An aluminum base alloy having a relatively low coemcient of thermal expansion and relatively great wear resistance, containing about tantalum,and about .'005% to .1% boron, with the balance substantially all aluminum and minor impurities.

5. An aluminum base alloy having a relatively low coefiicient of thermal expansion and relatively great wear resistance, containing about 20% to silicon, about .1% to 1% magnesium, about 1% to 5% copper, about .7 to 2% iron, and about .5% to 5% of at least two hardening metals selected from the group consisting of about 2% to 1% manganese, about .2% to 1.5% nickel, about .1% to .3% chromium, and about .1% to .5% cobalt, with the balance substantially all aluminum and minor impurities.

6. An aluminum base alloy having a relatively low coefficient of thermal expansion and relatively great wear resistance, containing about 20% to 35% silicon, about .1% to 1% magnesium, about 1% to 5% copper, about .7% to 2% iron, about .2% to 1% manganese, about .2% to 1.5% nickel, and about .05% to .3% titanium, with the balance substantially all aluminum and minor impurities.

WALTER BONSACK.