Investigation on the induction brazing of copper–steel tubes with different coil structures

The purpose of this study is to investigate the effect of coil structure on electromagnetic fields and temperature distributions of copper–steel tube induction brazing for compressor-automatic production line. To get a satisfied temperature distribution, five coil structures were designed and three-dimensional finite element models were established. The temperature distribution of the workpiece was numerically predicted and compared with the experimental values, and the simulated temperature field shows very good agreement with the experimental temperature measurements on the workpiece surface. The simulated results revealed that the coil structure was crucial and considerable to the thermal field of the workpiece and heating efficiency. Moreover, different materials have large differences in temperature change when heated by the same coil. To ensure good quality of the joints and high productivity, a reasonable heating time of rapid induction brazing was obtained at about 4 s. The comparison results indicated that the coil structure of square ring with series connection demonstrated the highest performance in terms of heating efficiency and energy usage among the coil designs.