| In this paper, the TIG welding method had been used to overlay cooper on the steel matrix. Interface bond strength of copper - steel was required to surpass welding copper layer and control the Fe content of copper layer. Based on the thickness requirements for copper, the method of double-surfacing had been adopted. The first layer was called the matrix layer, and the second was called coating layer. In addition, the essence of matrix layer process and coating layer was analyzed and summed up.Moreover, the TIG surfacing system was set up, a special gas protection device was designed, and non-essential process parameters (the location of the wire, the diameter of tungsten rod, tungsten bar high from the work piece) were determined through preliminary tests. The evaluation criterion of forming quality was made. In the meanwhile, the orthogonal test method was used to optimize the main process parameters of the matrix layer forming quality. And the results showed that the current and swing speed were the two most significant impact factors of the forming quality. The mechanism of Fe penetration was analyzed; the characteristics of Fe penetration was summed up, and the main process parameters impact on the degree of Fe penetration of the matrix layer were studied. The results revealed that with the increase of current and Fe penetration, while with the increase of wire feed speed, rotational speed and swing speed, it decreased. With combining the summary of process parameters of the matrix layer and a large number of coating layer's welding, the good forming process parameters of the coating layer were found. Samples welded of the optimized parameters were tested; results showed that use TIG surfacing could guarantee steel matrix scarcely non-melting and copper - steel metallurgical bonding.The observation of SEM indicated that the copper - steel interface was straight, steel matrix did not melt, there were no Stomata, welding slag nor other defects. In addition, there were 1- 2μm of composition rapidly changing regional and 5-10μm of the transition layer in the interface, while there was no Fe in the outside of the transition layer. The shear results showed that the sections were cut at the copper layer, which proved the interface shear strength was greater than copper layer. According to the hardness test, the hardness of copper layer surfacing was 55 - 60HB. |
