Heat treatment of cast aluminium alloy
Casting aluminum alloy heat treatment operation should pay attention to what matters
(1) to prepare
1) the casting shall not contain core sand, oil and sundries.
2) the casting shall be loaded into the material plate or basket before being put into the furnace. The workpiece shall be kept at an interval of about 25~30mm, and the workpiece with thin wall and cavity shall be placed on the upper layer.
3) equipment should choose low temperature or push rod type furnace, pit type furnace temperature control table for digital potentiometer, quenching temperature deviation is + / - 5 ℃, aging temperature deviation of plus or minus 10 ℃.
(2) operation points
1) load the furnace at quenching or aging temperature.
2) heating and insulation according to process requirements.
3) for complex shaped castings in air heating furnace, heating speed slowly, usually for 3 ~ 5 ℃ / min.
4) al-mg alloy with high magnesium content is not allowed to be heated in the nitre furnace to prevent explosion.
5) solid solution treatment temperature should be controlled in less than 3 ℃.
6) to prevent casting oxidation, aluminum oxide powder, refractory clay or graphite powder can be used for protection.
7) the holding time of solid solution of sand casting is 20%~25% longer than that of metal casting, and the holding time of the second solid solution treatment can be shortened by 25% ~ 40%.
8) quenching operation should be rapid to shorten the quenching transfer time.
9) casting in nitrate bath heating, quenching after cleaning should be carried out in 30 ~ 50 ℃ hot water, but stay in the hot water not too long, lest affect aging effect.
10) aluminum alloy casting shall be aging immediately after quenching. Aging is generally carried out in the air circulation heating furnace.