By analyzing the macroscopic and microscopic characteristics of the inner surface cracks and the machining process of the alloy shell parts, the failure causes are finally found, and improvement measures are proposed.
By analyzing the chemical composition of the fracture of the faulty part, the content of each element meets the requirements of the relevant standards, so the possibility of cracking on the inner surface of the part caused by the mixture of raw materials is excluded.
The low magnification corrosion test results of the faulty parts rule out the possibility of cracking of the inner surface of the parts due to serious metallurgical defects of the raw materials.
Aiming at the problem of crack defects on the inner wall of the shell part, the machining process is analyzed in detail. The original processing technology of 2A12 aluminum alloy shell parts is: blanking → car center hole (Ф65) → heat treatment (quenching + natural failure) → car inner hole (Ф140) → failure. The wall thickness of the part reaches 92.5mm before heat treatment.
Processing of stainless steel gasket parts
The metallographic analysis of the faulty parts after heat treatment (quenching + natural failure) shows that the reason for the cracks in the inner wall of the shell parts is that the tube wall is too thick and the heat treatment is not sufficient.
According to the actual situation of the raw materials of the aluminum alloy shell parts, the heat treatment process is further optimized, quenching + artificial aging heat treatment. The pit furnace is heated to 495±5℃, kept for 180-210min, and water-cooled. The microstructure was not found to be over-burned, and the aggregation of the strengthening phase along the grain boundary was significantly improved. This proves that the cracking part on the inner surface of the part is caused by insufficient heat treatment.
Gear parts processing
The analysis of the processing technology of the faulty part shows that when the processing reaches the insufficient heat treatment part, and the previous cutting speed and cutting amount are maintained, the stress concentration at the tool tip acts on the accumulation of the strengthening phase at the grain boundary, resulting in the crack distribution along the strengthening phase. direction expands rapidly.
Through the analysis of the macroscopic and microscopic characteristics of the inner surface cracks of the alloy shell parts and the machining process of the parts, the failure causes are finally found and improvement measures are proposed.
By analyzing the chemical composition of the fracture of the faulty part, the content of each element meets the requirements of the relevant standards, so the possibility of cracking on the inner surface of the part caused by the mixture of raw materials is excluded.
The low magnification corrosion test results of the faulty parts rule out the possibility of cracking of the inner surface of the parts due to serious metallurgical defects of the raw materials.
