US2189835A - Aluminum alloy - Google Patents

Description

Patented Feb. 13, 1940.

NI E STATES PATENT OFFICE I amass summon mo! No Drawing. Application May 8, 1939, Serial No. 272,520

-3 mm. (cl. -149) This invention relates to an improvement in aluminum alloys. More particularly, it has in view alloys of aluminum which may be used for most industrial requirements without heat treat- 6 ment and which has special machining qualities,

and also exhibits desirable physical characteristics in the way of high tensile strength, suitable hardness, and a high degree of elongation. The alloys combine with these qualities a number of 0 other advantages characteristics, such .as resistance to oxidation and corrosion. The alloys are of extremely fine grain, and machining operations result in a surface of a highly finished appearance.

15 These alloys, as stated, have high tensile strength and elongation without heat treatment, and while other alloys, after heat treatment involving additional expense, may show comparable tensile strength and elongation, the cost of manufacture is greater and they have the disadvantage of losing the increased physical characteristics, such as tensile strength or elongation upon being subjected to heating operations. The

alloys of the formula herein set forth when used without special heat treatment-may be freely welded or subjected to heating effects without losing the characteristics stated. They at all times exhibit the qualities or high tensile strength and a high degree of elongation, and at the same time provide the most satisfactory material for precision machining operations.

The alloys are of very wide application industrially, and while in no way limited to use for fabrication of various structural parts for ma- 85 chines and the like, they are particularly suited for such use, especially in equipment requiring precision of manufacturev andgood appearance.

Heretofore there have been many alloys embodying various proportions of aluminum, mag

nesium, copper and the like, and certain elements, such as titanium, have been used to improve the grain structure of the finished product. However, in many instances the alloys heretofore produced have involved complicated steps in alloying of the various elements, or in the development of tensile strength of the alloys throinh heat treatment and the like, and this expense and the incidental disadvantage 01' heat treatment are avoided in the present inventio The principal object of the invention is to provide alloys wherein the aluminum content is maintained at a relatively high percentage, and wherein the other elements of the alloy are acas curately proportioned to have combined action to increase the tensile strength of the finished product.

Another object of the invention is to provide alloys of aluminum having a high degree of tensile strength without sacrificing other desirable I physical characteristics, such as high degree of elongation.

Another object of the invention is to provide aluminum alloys having high tensile strength, and a high degree of elongation and physical 10 characteristics without the necessity of heat treatment for such product.

Another object of the invention is to provide an aluminum alloy resistant to corrosion, and at the same time having an unusual degree of 1 tensile strength and elongation, and adapted for machine operations to a greater degree than other alloys having like physical characteristics.

Another object of the invention is to provide an alloy of aluminum for use without heat treatl0 ment, but having a high degree of tensile strength and elongation comparable to those of heattreated alloys, which may be freely'welded without losing such high degree of tensile strength and elongation and other physical characteris- 25 ties as would be the case with'alloys receiving the original heat-treating eiiects.

Other and further objects of the invention will appear in the ,courseof the following description. a The preferred form of alloy includes with other elements added'to a high percentage of aluminum,

a small quantity of titanium, such element, however, being prei'erably added in the form of ferrotitanium instead as a titanium aluminum rich alloy. Normally the addition of iron to an aluminum alloy is not favored, but where such amount of iron is kept at a minimum and in close association with titanium such addition of a fractional per cent of iron is of no disadvantage and it apparently has the effect of speeding up the process of aging the alloy.

The preferred formula foran alloy of a high degree of tensile strength and at the same time a a high limit of elongation comprises the following: v

Specimens made in accordance with the above formula have shown a tensile strength of from 30,220 to 31,000 pounds and' an elongation of from 7 per cent to 8 per cent.

As stated the fractional percentage of iron present apparently accelerates the aging process. The use of term-titanium provides a ready means of introducing a satisfactory proportion of titanium and iron. However, the alloy may be made by adding titanium rich aluminum and a trace of iron may be present in the aluminum.

In the latter case amount iron may range from a trace to .40 per cent and the following formula is to be used:

Aluminum 93.30 to 93.70 Titanium .15 150 .30 Copper 1.50 to 2.00 Tin 1.50 to 1.75 Zinc .75 to 1.00 Magnesium .90 to 1.00 Chromium .20 to .25 Iron trace to .40 Variations may be made slightly above and below the elements set forth in the several formulas, as has been indicated, the aluminum content being the residual amount, required. The

exact physical results to be attributed to any particular element is not fully understood. but it is believed that the interaction of the elements added to the aluminum upon each other is clearly indicated. The titanium and tin together produce an unusuallyflne grained dense product having great tensile strength,-'and at the .same time having exceptional capacity for free machining, and presenting a finished surface after having been so machined. The combination of elements set forth produces an alloy in each instance of wide industrialapplication, which, in addition to having high tensile strength and a high degree of elongation, has fine appearance and capacity to resist oxidation and corrosive eiiects. While in the instances above stated the alloys will be round satisfactory tor most uses without subsequent heat-treatment,

it is not intended. to restrict the use of the invention to the extent that certainspecialized 7 treatment will not be applied in the event some very unusual application of the alloys is to be made,particularlyunder certain high temperature conditions, or where some extraordinary specifications have to be fulfilled. The widespread, and almost universal use of the alloys, without heat treatment, is provided for by the special 10 formulas above set forth, which, as stated, have the advantage of low cost of production, and permanence of physical characteristics, when welding or like operations are carried out.

Other modes of applying the principle of my invention'may be employed instead of those explained, change being made as regards the means and steps herein disclosed, provided the means stated by any of the following claims or the equivalent of such stated means be employed.

I therefore particularly point out and distinctly claim as my invention:

1. An alloy of aluminum consisting. of about 93.30 per cent of aluminum, .30 per cent of titaniuin, 2.00 per cent of copper, 1.75 per cent of tin, 1.00 per cent of zinc, 1.00 per cent of ma nesium, .25 per cent of chromium, and .40 per cent of iron.

2. An alloy of aluminum consisting of about .15 to .30 per cent of titanium, 1.50 to 2.00 per 80 cent of copper, 1.50 to 1.75 per cent of zinc, .75 to 1.00 per cent of magnesium, .20 to .25 per cent of chromium, from a trace to .40 per cent of iron, the balance being aluminum.

3. An alloy of aluminum for use without heat 25 treatment consisting of ferro-titanium having approximately equal parts of iron and titanium of an amount ranging from .30 to .70 per cent, 1.50 to 2.00 per cent of copper, 1.50 to 1.75 per cent of tin, .75 to 1.00 per cent of zinc, .90 to 1.00 40 per cent of magnesium, .20 to .25 per cent of chromium, the balance being aluminum.

EDWARD A. so.