How to overcome the problem of cracks in the inner wall of the aluminum flame detector housing components

Release time:

2022-01-20

After heat treatment of the aluminum flame detector housing components and the numerical control of the inner surface, the inspection found that there were longitudinal cracks on the inner surface of the parts.

How to overcome the problem of cracks in the inner wall of the aluminum flame detector housing components

aluminum flame detector housing components
The aluminum alloy is a reinforced aluminum alloy that can be heat treated, and has high strength after artificial aging, natural aging or solid solution heat treatment. It has good machinability and plastic forming ability, and is widely used in aerospace and other industrial structural parts because it can obtain different types of aluminum alloy products.
By analyzing the macroscopic and microscopic features of the inner surface cracks of the aluminum flame detector housing components 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 the internal surface cracking of the parts due to serious metallurgical defects of the raw materials.
Aiming at the problem of crack defects in the inner wall of the shell parts, the processing process of the shell parts is analyzed in detail. The original processing technology of Aluminum flame detector housing components 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.
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.
The heat treatment process is further optimized according to the actual situation of the raw materials of the aluminum flame detector housing components, quenching + artificial aging heat treatment. The pit furnace is heated to 495±5℃, kept for 180-210min, and water-cooled. The microstructure is not found to be over-burned, and the aggregation of the strengthening phase along the grain boundary is significantly improved. This proves that the cracking part on the inner surface of the part is caused by insufficient heat treatment.
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.
Axial cracks appear on the inner surface of the inner wall of the aluminum alloy shell during the machining process of the quenching and tempering heat treatment. Scanning electron microscope analysis of the crack, combined with the part processing route map, the results show that the crack formation is caused by insufficient heat treatment in the center of the part, and excessive cutting speed and cutting amount during machining.
In order to avoid inner wall crack defects during the processing of the aluminum flame detector housing components, it is recommended to increase the size of the center hole before the heat treatment in the processing specification. During the heat treatment process, the cooling rate of the parts should be accelerated to promote the complete transformation of the structure.

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