aluminum annealing

Under annealing aluminum and aluminum alloys generally understood full annealing, Unlike partial annealing, annealing to relieve work hardening or annealing in a controlled atmosphere.

Full annealing of aluminum and aluminum alloy

After complete annealing of all aluminum alloys – as thermally reinforcing, So thermally hardening - receive state, which is the softest, most ductile and most conducive to plastic deformation.

The international designation of this condition the letter "O". sometimes this letter "O" is confused with digit «0».

The national standards for aluminum products is the state just "annealing" and is a state designated by the letter "M". Within the meaning of and for the mechanical properties of the alloys in this state, this "simple" is just a joke full annealing, as it is understood in international standards.

annealing temperature

Reduction or complete removal of strain hardening from cold plastic deformation (autofrettage or work hardening) is achieved when heated to a temperature from 260 to 440 ° C. This is true both for the thermally hardened, and for thermally hardenable aluminum alloys.

The rate of strain-hardened softening material is strongly dependent on temperature. Therefore, the time, required for full annealing of the aluminum alloy with a given degree autofrettage, It may vary from several hours at lower temperatures to a few seconds at high temperatures.

Is the target annealing – annealing temperature is

If the purpose of the annealing is simply the removal of strain hardening, then heating to a temperature of about 345 ° C will be sufficient. If it is necessary to remove the hardening by heat treatment, or just by cooling the hot working temperature, it needs a special heat treatment to obtain a structure with a separation of the reinforcing phase in the form of large particles and freestanding. Such heat treatment is complete annealing: holding at a temperature from 415 to 440 ° C and slow cooling at a rate of about 30 ° C per hour to 260 ° C.

The high rate of diffusion of the alloying elements in aluminum, It is characteristic of such a high temperature, holding time and slow cooling ensure maximum coalescence (enlargement) of the hardening phase particles, that results in the material - aluminum alloy - minimum hardness.

Extract annealing and cooling after annealing

When annealing is important to provide, that the desired temperature has been reached in all parts of the cages and at all points of each product. Therefore the usually prescribed duration of soaking at an annealing temperature of not less than 1 o'clock. The maximum annealing temperature is moderately critical: it is recommended not to exceed the temperature 415 ° C due to the possible oxidation and grain growth. The heating rate may be critical, for example, alloy 3003, which usually requires rapid heating to prevent grain growth. Relatively slow cooling at still air or oven is recommended for all alloys to minimize warpage.

Typical parameters complete annealing for some aluminum alloys presented below.

Parameters complete annealing to remove deformation hardening

Aluminum alloys

1060, 1100, 1350
3003, 3004, 3105
5005, 5050, 5052, 5083, 5086, 5154, 5182, 5254, 5454, 5456, 5457, 5652
7005
It can also be used for thermally hardenable alloys, if the purpose is only removal of annealing the strain hardening or partial annealing.

annealing temperature

345 ° C

Exposure duration annealing temperature

Near 1 o'clock. Time spent in the furnace must be less than, than is necessary, that would bring all parts of the cages to an annealing temperature.

Cooling after annealing

The cooling rate after annealing is irrelevant.

Parameters complete relief annealing thermal hardening

Aluminum alloys

2014, 2017, 2024, 2036, 2117, 2124, 2219
6005, 6061, 6060, 6063, 6066
7079, 7050, 7075, 7079, 7178, 7475

annealing temperature

415 ° C

Exposure duration annealing temperature

from 2 to 3 hours

Cooling after annealing

Cooling at about 30 ° C per hour from the annealing temperature to 260 ° C. subsequent cooling rate does not matter.

Источник: Aluminum and Aluminum Alloys, AMS International, 1993.