The Study On Prolonging The Electrode Life Of Aluminum Alloy Spot Welding

Resistance spot welding of aluminum alloy is the most important welding technique in the automatic production of car body. However, there is a problem that the ignition loss of the electrode is too fast, which leads to frequent replacement, so production efficiency is reduced and the cost increases. Consequently, the technique of prolonging the electrode life of aluminum alloy spot welding is of reality significance.The research of the mechanism for the ignition loss of the electrode in spot welding of aluminum alloy shows that, plastic deformation is generated in part of the electrode surface by blasting right after the electrification, which is caused by the non-uniform point contact between electrodes and aluminum alloy work-pieces. The plastic deformation accelerates the non-uniform point contact. Blasting caused by the non-uniform point contact in part of the electrode surface leads to the ignition loss, which interacts with Cu-Al synthesis, makes the electrode worse. Hence, the life prolonging technique is to restrain Cu-Al synthesis at the interfaces of electrodes and aluminum alloy work-pieces and reduce blasting caused by the non-uniform point contact. From the point of the electrode surface and the aluminum alloy work piece surface, coating materials are sought and prepared to prolong the electrode life. For the electrode,compound electrode coating of Cu-Ti-B is successfully synthesized in situ at the Zr-Cr-Cu electrode surface by resistance heat and pressure while spot welding. Structure and component analysis show that it contains TiBstrips and grainy with good heat resistance which can intensify the strength of coating base and reduce the plastic deformation generated in part of the electrode surface by blasting right after the electrification. So it is feasible to prolong the electrode life of aluminum alloy spot welding by the Cu-Ti-B compound coating of the electrode. Further research will be grasped.For the aluminum alloy,coating mixture of mineral oil and B₄C on the work-piece can reduce the contact of Cu and Al, and the temperature at the interfaces of electrodes and aluminum alloy work-pieces, which restrain Cu-Al synthesis on one hand. On the other hand mineral oil and B₄BC can reduce the non-uniform point contact and relieve blasting in part of the electrode surface. Hence, the spot welding result of aluminum alloy with the coating mixture of mineral oil and BBC is better, and the electrode life of aluminum alloy spot welding is prolonged.