Causes of various stresses in aluminum alloy forging

Aluminum alloy forging production is one of the main machining methods to provide mechanical parts blank in machinery manufacturing industry. Through forging, not only the shape of the mechanical parts can be obtained, but also the internal structure of the metal can be improved and the mechanical and physical properties of the metal can be improved. Under normal circumstances, high stress, high requirements of important mechanical parts are forged. Such as turbo generator shaft, rotor, impeller, blade, guard ring, large hydraulic machine column, high pressure cylinder, rolling mill roll, internal combustion engine crankshaft, connecting rod, gear, bearing and national defense industrial artillery and other important components, are forged. Therefore, forging production is widely used in metallurgy, mining, automobile, tractor, harvesting machinery, petroleum, chemical industry, aviation, aerospace, weapons and other industrial sectors, in daily life, forging production also has an important position.

 

In a sense, the indexes such as the annual output of forgings, the proportion of forgings in the total output of forgings, the scale and ownership of forgings equipment reflect the industrial level of a country to a certain extent.

 

The stress of aluminum alloy forging includes thermal stress phase transformation stress and shrinkage stress. The causes of various stresses are different.

 

 

 

Forging stress of aluminum alloy forgings

 

(1) Thermal stress. The thermal stress is caused by the shape and thickness of the slab and the uneven thickness of the slab. Compressive stress is formed at the thin wall, resulting in residual stress of casting.

 

(2) Phase transition stress. The phase change stress is caused by the change of the size of some cast aluminum alloys during the cooling process. The main reason is that the wall thickness of cast aluminum is not uniform and the phase transition occurs in different parts at different times.

 

(3) Compression stress. The tensile stress of aluminum castings is caused by the resistance of the mold and core. This stress is transient and dissipates when aluminum castings are disassembled. However, improper opening time often causes thermal cracks, especially when aluminum alloy is poured by metal mold, thermal cracks tend to occur under such stress.