How to Avoid Cracks on the Inner wall of Aluminum Case Parts?

Aluminum case machining is one of the common parts processing in CNC machining, but the aluminum case parts machining will encounter problems such as deformation and cracks. This article analyzes and shares with you the macroscopic and microscopic characteristics of the internal surface cracks of the shell parts and the problems of the parts processing process.

Analysis of the causes of cracks in the inner wall of aluminum case parts machining

We can analyze the problem of cracks on the inner wall of the shell part according to reverse engineering.

1. A detailed analysis of its processing process.

Cutting → the center hole of the car (Ф65) → heat treatment (quenching + natural failure) → the inner hole of the car (Ф140) → failure. The wall thickness of the parts before heat treatment reaches 92.5mm.

2. Perform metallographic analysis on the failed parts after heat treatment (quenching + natural failure).

The reason for the cracks on the inner wall of the shell parts is that the pipe wall is too thick and the heat treatment is not sufficient.

3. According to the actual situation of the raw materials of aluminum case parts, further optimize the heat treatment process analysis,

Quenching + artificial aging heat treatment. The pit furnace is heated to 495±5℃, kept for 180～210min, and water-cooled. No overburning was found in the microstructure, and the aggregation of the strengthening phase along the grain boundary was significantly improved. This proves that the cracks on the inner surface of the aluminum case parts are caused by insufficient heat treatment.

4. Analyze the chemical composition through the fracture of the faulty part.

The content of each element meets the requirements of relevant standards, so the possibility of cracking of the inner surface of the aluminum case parts caused by the mixing of raw materials is excluded.

5. Analysis of the results of the low-magnification corrosion test of the failed parts.

Eliminate the possibility of cracks on the inner surface of the parts due to serious metallurgical defects.

Causes    

The analysis of the above process shows that the cause of the cracks on the inner wall of the aluminum case parts is from the processing to the insufficient heat treatment part, and the previous cutting speed and cutting amount are still maintained, and the stress concentration at the tip part acts on the grain boundary strengthening phase. At the gathering place, the cracks will rapidly expand along the direction of the band-like distribution of the strengthening phase.

The solution is as follows

The processing size of the center hole is increased before the heat treatment in the processing procedure. During the heat treatment, the cooling rate of the aluminum case parts is accelerated to promote the complete transformation of the structure.

Machining speed:

If you need to process a small number of parts in a short time, then CNC machining is the best choice. For example, if you need to make 15 parts in two weeks, CNC machining is the best choice. When you need 40,000 parts in a few months, injection molding takes time to make the mold and ensure that the parts are within tolerance, which may take several weeks to several months. On the other hand, our CNC machining factory machine workshop has hundreds of equipment processing, which can shorten the delivery time.

VMT stainless steel, copper, aluminum precision CNC machining parts manufacturing plant has 11 years of technology precipitation and rich experience. The products processed by our CNC include: non-standard micro and small components, copper/aluminum alloy parts, hardware shells, electronic radiators, medical equipment parts, instrumentation parts, precision machinery parts, communication parts, electronic products High-standard and high-quality products in spare parts, auto parts and other industries. All product production processes strictly abide by quality standards and strictly require production processes. All products undergo strict quality inspections.