US1394534A - Heat treatment of aluminum alloys - Google Patents

Description

TT FFEIQE.

EARL BLOUGH, OF PARNASUS, PENNSYLVANIA, ASSIGN OR TO ALUMINUM COMPANY OF AMERICA, OF PITTSBURGH, PENNSYLVANIA, A CORPORATION OF PENNSYL- VANIA.

HEAT TREATMENT OF ALUMINUM ALLOYS.

Specification of Letters Patent.

Patented Oct. 25, 1921.

, No Drawing. Application filed November 30, 1917, Serial No. 204,540. Renewed December 28, 1920.

Serial No. 433,691.

T 0 all whom it may concern.

Be it known that I, EARL BLOUGH, a citizen of the United States, residing at Parnasus, in the county of Allegheny and State of Pennsylvania, have invented certain new and useful Improvements in Heat Treatment of Aluminum Alloys, of which the following is a full, clear, and exact description.

This invention relates to the heat treatment of aluminum alloys, and the chief object of the invention is to provide a simple and easily worked method of treatment for the purpose of improving the important physical propertiesof hardness and tensile strength, especially the latter.

As in the treatment of steel, certain prior processes or methods involve heating the metal and then cooling or quenching it. The present invention is based on the discovery that the heat-treatment should be effected in stages, the first at a rather elevated temperature and the last at a somewhat lower degree.

In applying my process in the preferred manner, the metal is first heated to a temperature of about 500 C. or higher, say 575 or more, but in general not above 600. In many cases 520 is satisfactory. The temperature may be considerably lower, for ex; ample around 400, but a higher degree is better. In general, the duration of this heating stage should be long enough for the metal to reach a state of equilibrium, that is to say, a state in which any internal stresses and strains have been relieved and in which there have taken place any thermal reactions and changes that normally occur at such temperature, as for example change in the crystalline structure of the alloy.

The actual time required for this effect is V of course variable with the nature of the alloy, but ordinarily a period of from two to three hours heating, after the metal has been brought up to the temperature, has been found suflicient. If such a period does not give the desired results in any specific instance longer periods may be tried. The heating is now continued (without intermediate rolling, stamping, drawing or other working) at a lower temperature, which may be between about 100 and about 200. Good results are secured at 100, and this temperature is advantageous because of the convenience with which it can be obtained and maintained by means of boiling water. \Vith any material advantage in temperatures much above 200, say 250, it has been observed that the elongation is apt to be impaired and the improvement in tensile strength diminished. A time of two hours for the second heating is ample for most purposes, but it may be prolonged beyond that. I have not, however, observed continuing the second heatin longer than about twentyfour hours. fnstead of continuing the second heating stage it may be maintained merely long enough for the lower temperature to become uniform throughout the metal, after which the temperature can be raised, say to between 150 and 200, about, and kept there until the results desired are attained.

The metal can now be cooled, quickly or slowly, whereupon it will be found that its tensile strength has been very remarkably increased. Nor is it necessary to store the metal, or allow it to rest, for a time after cooling, before it is used. On the contrary, the metal can at once be put to any use for which it is suitable. In fact, with a final heating stage or step lasting no more than twenty-four hours the tensile strength has been found to be superior to that resulting from four days storing after cooling followin a single heating.

IVIy process is applicable to a great variety of aluminum-copper alloys, and to aluminum-copper alloys containing also one or more of other metals, for example, zinc, magnesium, iron, calcium, and silicon. It is particularly effective with alloys in which the copper content does not exceed about ten per cent.

The temperatures referred to in the foregoing description and in the appended claims are all measured on the Centigrade scale.

I claim 2-- '1. In a method of heat-treating aluminum alloy of the kind described to improve certain of its physical properties, especially tensile strength, the steps comprising subjecting the said alloy to heat at a tempera ture above about 400 C., and, without working the alloy, subjecting it for a period of time to heat at a lower temperature.

2. In a method of heat-treating aluminum alloy of the kind described, to improvecertain of its physical properties, especially tensile strength, the steps comprising subjecting the alloy to heat at a temperature of above about 400 0., and, without working the alloy, subjecting it for a period of time to heat at a temperature not less than about 100 O.

. 3. In a method of heat-treating aluminum alloy of the kind described, to improve certain of its physical properties, especially tensile strength,the steps comprising subjectheating for a period of time at a temperature of not less than about 100 C.

5. In a method of'heat-treating aluminum alloy of the kind described, to improve certain of its physical properties, especially tensile strength, the steps comprising subjecting the alloy to heat at a temperature above about 400 C., and, without working the alloy, subjecting it to further heating at a lower temperature for a period of not less than about two hours.

6. In a method of heat-treating aluminum alloy of the kind described, to improve certain of its physical properties, especially tensile strength, the steps comprising sub-- jecting the alloy to heat at a temperature above about 400 C., and, without working the alloy, subjecting it to further heating at a temperature of not less than about 100 0., for a period of not less than about two hours.

7. In a method of heat-treating aluminum alloy of the kind described, to improve certain of 1ts physlcal properties, especially tens le strength, the steps comprising subecting the alloy to heat at a temperature of not less than about 500 CT, and, without working the alloy, subjecting it to further heatlng at a lower temperature for a period of not less than about two hours. I

8. In a method of heat-treating aluminum alloy of the kind described, to improve certain of its physical properties, especially tens le strength, the steps comprising subecting the alloy to heat at a temperature not less than about 500 C., and, without working the alloy, subjecting it-to further heating at a temperature of not less than about 100 C., for aperiod of not less than about two hours.

9. In a method of heat-treating aluminum alloy of the kind described, to improve certain of 1ts physical properties, especially tensile strength, the steps comprising subjecting the alloy to heat at a temperature above about 400 C., then, without working jecting the alloy to heat at a temperature above about 500 C., then, without working the alloy, subject it to heat at a temperature above about 100 0., then without working the alloy subjecting it for a period of time to heat at a higher temperature then that used in said second step, but below 300 C.

11. In a method of heat-treating aluminum alloy of the kind described, to improve certain of its physical properties, especially tensile strength, the steps comprising subjecting the alloy to heat at an elevated temperature, then, without working the alloy, lowering its temperature materially; then, without working the alloy, raising its temperature and maintaining it for-a period of time at a temperature materially higher than that to which the temperature had been so reduced, but lower than that atwhich the alloy was subjected in such first step.

12. In a method of heat-treating aluminum alloy of the kind described, to improve certain of its physical properties, especially tensile strength, the steps comprising subjecting the alloy to heat at an elevated temperature,-then, without working the alloy, lowering its temperature materially, then, without working the alloy, raising its temperature and maintaining it for not less than two hours at a temperature materially higher than that to which the temperature had been lowered, but lower than that at which the alloy was treated in the first step.

13. In a method of heat-treating aluminum alloy of the kind described, to improve certain of its physical properties, especially tensile strength, subjecting the alloy to heat in a plurality of stages without intermedlate working, at least two of the stages each lasting for a material period of tlme; the first at a temperature exceeding 400 C., and another at a temperature more than 200 C. lower than the first. I

14. In a method of heat-treating aluminum alloy of the kind described, to improve certain of its physical properties, especially tensile streigth, subjecting the alloy to heat in a plurality of stages without intermediate working, at least two of the stages each lasting for a sufficient length of time to establish the internal structure of the alloy in an approximately stable state at that temperature, the temperature in the first of said stages exceeding 400 (3., and the temperature in a subsequent one of said stages being more than 200 C. lower than that in the first stage.

15. In a method of heat-treating aluminum alloy of the kind described, to improve certain of its physical properties, especially tensile strength, subjecting the alloy to heat in a plurality of stages without intermediate working, at least two of the stages each lasting for a sufiicient length of time to establish the internal structure of the alloy in an approximately stable state at that temperature, the temperature in the first stage exceeding 400 (7., and the temperature in another of said stages being between 100 C. and 250 C, approximately.

16. In a method of heattreating aluminum alloy of the kind described, to improve certain of its physical properties, especially tensile strength. subjecting the alloy to heat at an elevated temperature until the internal stresses existing have been relieved and the thermal reactions and changes that normally occur at such a temperature have taken place, and thereafter subjecting the alloy, without intermediate working, to heat at a lower temperature for time.

I 17. In a method of heat-treating aluminum alloy of the kind described, to improve certain of its physical properties, especially tensile strength, subjecting the alloy to heat at an elevated temperature until the internal stresses existing have been relieved and the thermal reactions and changes that normally occur at such a temperature have taken place, and thereafter subjecting the alloy, without intermediate working. to heat at a lower temperature above about 100 C. for a material period of time.

18. In a method of heat-treating aluminum alloy of the kind described, to improve certain of its physical properties. especially tensile strength, subjecting the alloy to heat at an elevated temperature until the internal stresses existing have been relieved and the thermal reactions and changes that normally occur at such a temperature have taken place, and thereafter subjecting the alloy, without intermediate working, to heat at a lower temperature for not less than about two hours.

19. In a method of heat-treating aluminum alloy of the kind described, to improve certain of its physical properties, especially tensile strength, subjecting the alloy to heat at an elevated temperature until the internal stresses existing have been relieved and the thermal reactions and changes that normally occur at such a temperature have taken place, and thereafter subjecting the alloy,

without intermediate working, to heat at a a material period of lower temperature between about 100 C and 300 C., for not less than about two hours.

20. In a method of heat-treating aluminum alloy of the kind described, toimprove certain of its physical properties, especially tensile strength, subjecting the alloy to heat at a temperature of above 400 C., and, without working the alloy, quenching it in boiling water; then, without intermediate working, heating it in boiling water for a material period of time.

21. In a method of heat-treating aluminum alloy of the kind described, to improve certain of its physical properties, especially tensile strength, subjecting the alloy to heat at a temperature of over 400 C., and, without working the alloy, quenching it in boil ing water; then, without intermediate working, heating it in boiling water for not less than about two hours.

22. In a method of heat-treating aluminum alloy of the kind described, to improve certain of its physical properties, especially tensile strength, subjecting the alloy to heat at a temperature of over 500 C., and, without working the alloy, quenching it in boiling water; then, without intermediate working, heating it in boiling water for a material period of time.

23. In a method of heat-treating aluminum alloy of the kind described, to improve certain ofits physical properties, especially tensile strength, subjecting the alloy to heat at a temperature of over 500 0., and, without working the alloy, quenching it in boiling water; then, without intermediate working, heating it in boiling water for not less than about two hours.

'24. In a method of heat-treating aluminum alloy of the kind described, to improve certain of its physical properties, especially tensile strength, subjecting the alloy to heat at a temperature of over 400 C., and, without working the alloy, quenching it in boiling water; then, without intermediate working, subjecting it'to a further heating at a temperature betweenl about 100 C. and 300 (1., for a material period of time. e

25. In a method of heat-treating aluminum alloy of the kind described, to improve certain of its physical properties, especially tensile strength, subjecting the alloy to heat at a temperature of over 500 C, and, without working the alloy, quenching it in boiling water; then, without intermediate Working, subjecting it to a further heating at a temperature above about 100 C, for not less than about two hours.

In testimony whereof I hereunt affix my signature.

EARL BLOUGH.