71 / 2021-06-30 13:32:00

Removal method and influence analysis of sintered layer on composite joint surface of heat exchanger by wire cutting machining

Heat exchange; Wire cutting; Sintered layer removal

In order to improve the heat transfer efficiency of the heat exchanger, it is necessary to couple the two metals of the radiating surface and the heat producing surface. In engineering application, aluminum alloy and stainless steel should be connected together to form an aluminum / stainless steel composite pipe joint.

At the same time, in order to improve the fluidity of the heat transfer medium, it is necessary to process conduits in the pipe joint. Due to the small size and high accuracy of the internal channel of the joint, it is difficult to process by using the conventional machining method. At present, it can only be manufactured by the slow wire cutting method. However, the surface after wire cutting is seriously oxidized and sintered, and it is easy to adhere and absorb the impurity elements in the processing fluid. In order to reduce the influence of impurity elements on the working fluid in the joint, it is necessary to remove the pollutants in the joint.

This paper analyzes the influence of wire cutting on the surface morphology and chemical composition of 6063 aluminum alloy 316 stainless steel composite pipe joint, and uses ethanol ultrasonic cleaning, hydrofluoric acid  pickling, sodium hydroxide alkali cleaning, sand blasting and other methods to remove the surface pollutants. The micro morphology, chemical composition and tensile strength were tested by tensile machine. The experimental results show that ultrasonic cleaning can remove oil and scale. Hydrofluoric acid pickling has great corrosion on the aluminum end, and obvious height difference is formed between aluminum and stainless  steel. Sodium hydroxide alkali pickling has obvious effect of removing oil and oxide scale, but has no obvious effect on tensile strength. The effect of sandblasting on removing the sintered layer is poor, there is a risk of residual sand, and it has a great impact on the joint size.