隨著現代汽車工業的發展，為了提高使用壽命，車身通常采用耐腐蝕性能較好的鍍層鋼板，尤其以鍍鋅鋼板的使用量為大，鍍鋅板已經在越來越多的汽車零部件上得到應用[1-4]。由于鍍鋅板的大量應用，汽車零部件常規的組裝方法——焊接，也帶來了新的技術問題，汽車焊接主要采用電阻焊焊接。目前國內汽車廠使用的焊接鍍鋅板電極材料一般為鉻鋯銅，鉻鋯銅在焊接低碳鋼時具有很好的可靠性。但焊接鍍鋅板時，由于銅和鋅在高溫情況下發生冶金結合，生成鋅黃銅，從而出現電極粘連鍍鋅板的情況，嚴重影響產品的焊接質量，減少了電極的使用壽命，頻繁的更換電極，降低了生產效率。

1.鍍鋅板點焊電極使(shi)用條件(jian)及失效現象

電(dian)阻焊(han)在汽車(che)焊(han)接(jie)(jie)上廣泛應(ying)用，電(dian)阻焊(han)的焊(han)接(jie)(jie)原理是利(li)用在電(dian)極之間(jian)通過大電(dian)流而(er)產生大量熱量，使鋼(gang)(gang)板在電(dian)極壓力下形成焊(han)核，從(cong)而(er)達到聯接(jie)(jie)鋼(gang)(gang)板的目的。

鍍鋅板(ban)焊接(jie)(jie)過程是(shi)個復雜(za)的(de)(de)(de)物(wu)理及(ji)化(hua)(hua)(hua)學(xue)變(bian)化(hua)(hua)(hua)的(de)(de)(de)過程，其中典(dian)型的(de)(de)(de)化(hua)(hua)(hua)學(xue)變(bian)化(hua)(hua)(hua)就是(shi)鋅與(yu)(yu)銅(tong)(tong)(tong)(tong)(tong)結合產生(sheng)了(le)黃(huang)(huang)(huang)(huang)銅(tong)(tong)(tong)(tong)(tong)。由于鍍鋅板(ban)上的(de)(de)(de)鋅溶點較(jiao)低，焊接(jie)(jie)加(jia)(jia)熱時(shi)，鋅會(hui)首先熔化(hua)(hua)(hua)析出(chu)與(yu)(yu)電(dian)(dian)(dian)極(ji)(ji)(ji)(ji)(ji)表面的(de)(de)(de)銅(tong)(tong)(tong)(tong)(tong)結合產生(sheng)黃(huang)(huang)(huang)(huang)銅(tong)(tong)(tong)(tong)(tong)，黏附在(zai)電(dian)(dian)(dian)極(ji)(ji)(ji)(ji)(ji)表面，導(dao)致電(dian)(dian)(dian)極(ji)(ji)(ji)(ji)(ji)導(dao)電(dian)(dian)(dian)率下降，因此黃(huang)(huang)(huang)(huang)銅(tong)(tong)(tong)(tong)(tong)的(de)(de)(de)存在(zai)會(hui)直接(jie)(jie)影響到(dao)下一次焊接(jie)(jie)的(de)(de)(de)效果，同時(shi)鉻是(shi)鋅與(yu)(yu)銅(tong)(tong)(tong)(tong)(tong)發生(sheng)化(hua)(hua)(hua)學(xue)反(fan)應產成黃(huang)(huang)(huang)(huang)銅(tong)(tong)(tong)(tong)(tong)的(de)(de)(de)催化(hua)(hua)(hua)劑。用(yong)含(han)鉻這種元素的(de)(de)(de)銅(tong)(tong)(tong)(tong)(tong)合金來制作電(dian)(dian)(dian)極(ji)(ji)(ji)(ji)(ji)，在(zai)冷軋鋼板(ban)的(de)(de)(de)焊接(jie)(jie)過程中，可(ke)以增加(jia)(jia)電(dian)(dian)(dian)極(ji)(ji)(ji)(ji)(ji)的(de)(de)(de)硬度(du)，減少修(xiu)磨(mo)次數(shu)，從而提高電(dian)(dian)(dian)極(ji)(ji)(ji)(ji)(ji)的(de)(de)(de)使(shi)用(yong)壽命，但是(shi)在(zai)進行鍍鋅板(ban)的(de)(de)(de)焊接(jie)(jie)時(shi)，卻(que)會(hui)在(zai)焊接(jie)(jie)過程中產生(sheng)黃(huang)(huang)(huang)(huang)銅(tong)(tong)(tong)(tong)(tong)，導(dao)致電(dian)(dian)(dian)極(ji)(ji)(ji)(ji)(ji)和鍍鋅板(ban)容易發生(sheng)粘連，增加(jia)(jia)修(xiu)磨(mo)次數(shu)。由此可(ke)見(jian)，鉻鋯銅(tong)(tong)(tong)(tong)(tong)對于鍍鋅板(ban)焊接(jie)(jie)來說反(fan)而不是(shi)一種理想的(de)(de)(de)電(dian)(dian)(dian)極(ji)(ji)(ji)(ji)(ji)材料。

對于目前使用(yong)鉻鋯銅(tong)作為電(dian)極(ji)(ji)(ji)(ji)材料(liao)焊(han)接(jie)鍍鋅(xin)板(ban)，電(dian)極(ji)(ji)(ji)(ji)失效(xiao)主要有3個(ge)方面：首(shou)先電(dian)極(ji)(ji)(ji)(ji)變(bian)軟，出現(xian)蘑菇頭(tou)狀，使電(dian)極(ji)(ji)(ji)(ji)使用(yong)壽(shou)命變(bian)短，影響(xiang)焊(han)接(jie)質量；其(qi)次，焊(han)接(jie)過程中出現(xian)“炸槍(qiang)”，火花過大，焊(han)點質量差(cha)，出現(xian)毛(mao)邊、飛刺(ci)；出現(xian)焊(han)接(jie)工件與電(dian)極(ji)(ji)(ji)(ji)粘連現(xian)象，導致電(dian)極(ji)(ji)(ji)(ji)燒蝕，如(ru)圖3所(suo)示，工件虛(xu)焊(han)、電(dian)極(ji)(ji)(ji)(ji)脫落，嚴重影響(xiang)焊(han)接(jie)質量和生產(chan)效(xiao)率(lv)。

2.失效原(yuan)因分(fen)析(xi)

汽車電(dian)(dian)(dian)阻焊(han)(han)(han)(han)焊(han)(han)(han)(han)接(jie)(jie)(jie)過(guo)程是(shi)高溫冶金過(guo)程，電(dian)(dian)(dian)極(ji)(ji)(ji)的(de)不(bu)(bu)同(tong)位置，溫度有所(suo)不(bu)(bu)同(tong)。由于(yu)(yu)在(zai)焊(han)(han)(han)(han)接(jie)(jie)(jie)時(shi)溫度很高，在(zai)導致鋼板軟化(hua)(hua)(hua)(hua)(hua)產(chan)生塑(su)性(xing)變(bian)形的(de)同(tong)時(shi)，也會(hui)使電(dian)(dian)(dian)極(ji)(ji)(ji)發生軟化(hua)(hua)(hua)(hua)(hua)，因此會(hui)使電(dian)(dian)(dian)極(ji)(ji)(ji)的(de)形狀發生變(bian)化(hua)(hua)(hua)(hua)(hua)，受壓力影響，出(chu)現(xian)(xian)蘑菇頭(tou)狀。不(bu)(bu)同(tong)材(cai)料的(de)軟化(hua)(hua)(hua)(hua)(hua)溫度不(bu)(bu)盡相(xiang)同(tong)，這是(shi)材(cai)料的(de)物理特性(xing)決定的(de)，對于(yu)(yu)目汽車焊(han)(han)(han)(han)接(jie)(jie)(jie)使用的(de)鉻鋯銅電(dian)(dian)(dian)極(ji)(ji)(ji)材(cai)料，軟化(hua)(hua)(hua)(hua)(hua)溫度不(bu)(bu)超過(guo)550℃，然而(er)對于(yu)(yu)焊(han)(han)(han)(han)接(jie)(jie)(jie)需要，電(dian)(dian)(dian)極(ji)(ji)(ji)需要抵抗大約900℃的(de)溫度。所(suo)以(yi)出(chu)現(xian)(xian)電(dian)(dian)(dian)極(ji)(ji)(ji)軟化(hua)(hua)(hua)(hua)(hua)，蘑菇頭(tou)狀失(shi)效(xiao)，是(shi)電(dian)(dian)(dian)阻焊(han)(han)(han)(han)電(dian)(dian)(dian)極(ji)(ji)(ji)材(cai)料作為焊(han)(han)(han)(han)接(jie)(jie)(jie)消(xiao)耗品的(de)主要的(de)失(shi)效(xiao)現(xian)(xian)象，工作人(ren)員也通過(guo)各種方法來(lai)盡量減慢這種失(shi)效(xiao)現(xian)(xian)象。對于(yu)(yu)鍍(du)(du)鋅(xin)(xin)板焊(han)(han)(han)(han)接(jie)(jie)(jie)，為了緩解(jie)電(dian)(dian)(dian)極(ji)(ji)(ji)與鍍(du)(du)鋅(xin)(xin)板的(de)粘(zhan)連，往往通過(guo)加大電(dian)(dian)(dian)流(liu)的(de)方式來(lai)擊穿鍍(du)(du)鋅(xin)(xin)板的(de)鋅(xin)(xin)層，從而(er)導致鉻鋯銅電(dian)(dian)(dian)極(ji)(ji)(ji)材(cai)料在(zai)焊(han)(han)(han)(han)接(jie)(jie)(jie)鍍(du)(du)鋅(xin)(xin)板時(shi)出(chu)現(xian)(xian)蘑菇頭(tou)失(shi)效(xiao)的(de)現(xian)(xian)象更為嚴重，使用壽命更短。