Multi-stage gradient temperature control composite heat source intelligent flame brazing technology

Objective The aim is to solve the problems of insufficient temperature control accuracy and unstable weld quality in the brazing process of semi-circular tubes of airconditioner condenser and evaporator. Methods In this study, an innovative automatic flame brazing technology with multi-stage temperature gradient and composite heat source synergy was proposed. The technology enabled precise control of brazing thermal process through a four-stage temperature control system (preheating, brazing, insulation, and nitrogen cooling) and a differentiated heat source configuration (oxygen-natural gas high heat source combined with air-natural gas temperate heat source). Results The batch verification of 20 000 sets of modules shows that the technology improves temperature control accuracy to ±5 ℃ (the original process ±25 ℃), welding leakage rate is reduced from 38×10⁻⁴ to 8×10⁻⁴. Conclusion The research effectively solves the problems of uneven distribution of brazing filler metal, coarse grain of base metal and post-welding oxidation caused by traditional processes, and provides a high-stability and high-quality connection solution for the manufacture of airconditioner heat exchanger, which has important engineering application value.