【作者】 刘丹；

【导师】 王惜宝；

【作者基本信息】 天津大学 ， 材料加工工程， 2006， 硕士

【摘要】 铝合金的电阻点焊是汽车车身自动化生产中最重要的焊接工艺方法,但是铝合金电阻点焊中存在的一个主要问题就是电极过快烧损,引起电极的频繁更换,影响生产效率。因此研究铝合金点焊电极的延寿技术至关重要。本文通过对铝合金点焊电极烧损失效机理的研究发现,点焊时电极与铝合金工件接触面间的不均匀点接触造成通电瞬间局部小爆炸而使电极端面局部区域产生塑性变形,这种局部的塑性变形反过来又加剧了电极与工件接触面间的不均匀点接触,由不均匀点接触引起的局部小爆炸和铜铝合金化交互作用,使电极失效速度加快。因此,铝合金点焊电极延寿技术研究的基本原则,就是要减轻电极与铝合金工件接触面间的铜铝合金化以及减少不均匀点接触造成的局部小爆炸。本文从电极表面和铝合金工件表面两种角度出发,寻找制备涂层材料,以延长电极的使用寿命。从电极表面考虑,我们探索性地利用点焊时产生的电阻热和加压作用,成功地在锆铬青铜电极表面原位合成了Cu-Ti-B复合电极涂层。通过对复合涂层组织、成分的分析,我们发现其中含有条状以及粒状的TiBB具有很好的热强性,点焊时可以增强涂层基体的强度,减少电极端面局部小爆炸引起的塑性变形。故用Cu-Ti-B复合涂层电极点焊铝合金是可以延长电极使用寿命的,以后还要做进一步的研究。从铝合金工件表面考虑,在铝合金表面涂敷矿物油和B的混合物,点焊时一方面可以机械地隔离铜电极中的铜与铝的接触,降低电极与铝合金工件接触面间的温度,从而减轻铜铝合金化,另一方面还可以减少不均匀点接触造成的局部小爆炸。因而铝合金表面涂敷矿物油和BBC的混合物时,电极烧损程度较轻,电极使用寿命得到了延长。更多还原

【Abstract】 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.更多还原