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(han)電極使用條件及失(shi)效現象

電(dian)阻焊(han)在(zai)(zai)(zai)汽車焊(han)接上廣泛應用(yong)，電(dian)阻焊(han)的(de)焊(han)接原(yuan)理(li)是利(li)用(yong)在(zai)(zai)(zai)電(dian)極之間通(tong)過大電(dian)流(liu)而(er)產生大量熱量，使鋼板在(zai)(zai)(zai)電(dian)極壓力下(xia)形成焊(han)核，從而(er)達到聯接鋼板的(de)目(mu)的(de)。

鍍(du)鋅(xin)(xin)(xin)板焊(han)(han)接(jie)(jie)過程(cheng)是個復雜(za)的(de)(de)(de)物理(li)及化(hua)學(xue)變化(hua)的(de)(de)(de)過程(cheng)，其中(zhong)典(dian)型的(de)(de)(de)化(hua)學(xue)變化(hua)就(jiu)是鋅(xin)(xin)(xin)與(yu)銅(tong)(tong)結合產(chan)(chan)生(sheng)(sheng)了(le)黃(huang)銅(tong)(tong)。由(you)于鍍(du)鋅(xin)(xin)(xin)板上的(de)(de)(de)鋅(xin)(xin)(xin)溶點較(jiao)低(di)，焊(han)(han)接(jie)(jie)加熱時，鋅(xin)(xin)(xin)會首先熔化(hua)析出(chu)與(yu)電(dian)(dian)極(ji)(ji)表面的(de)(de)(de)銅(tong)(tong)結合產(chan)(chan)生(sheng)(sheng)黃(huang)銅(tong)(tong)，黏附在(zai)電(dian)(dian)極(ji)(ji)表面，導(dao)(dao)致(zhi)電(dian)(dian)極(ji)(ji)導(dao)(dao)電(dian)(dian)率(lv)下(xia)降，因此黃(huang)銅(tong)(tong)的(de)(de)(de)存在(zai)會直接(jie)(jie)影響到下(xia)一(yi)次焊(han)(han)接(jie)(jie)的(de)(de)(de)效果，同時鉻(ge)是鋅(xin)(xin)(xin)與(yu)銅(tong)(tong)發(fa)生(sheng)(sheng)化(hua)學(xue)反(fan)應產(chan)(chan)成黃(huang)銅(tong)(tong)的(de)(de)(de)催(cui)化(hua)劑。用含(han)鉻(ge)這種元素(su)的(de)(de)(de)銅(tong)(tong)合金來制作電(dian)(dian)極(ji)(ji)，在(zai)冷軋鋼板的(de)(de)(de)焊(han)(han)接(jie)(jie)過程(cheng)中(zhong)，可(ke)以增(zeng)加電(dian)(dian)極(ji)(ji)的(de)(de)(de)硬度，減(jian)少修磨次數，從而提高(gao)電(dian)(dian)極(ji)(ji)的(de)(de)(de)使用壽命(ming)，但是在(zai)進行鍍(du)鋅(xin)(xin)(xin)板的(de)(de)(de)焊(han)(han)接(jie)(jie)時，卻會在(zai)焊(han)(han)接(jie)(jie)過程(cheng)中(zhong)產(chan)(chan)生(sheng)(sheng)黃(huang)銅(tong)(tong)，導(dao)(dao)致(zhi)電(dian)(dian)極(ji)(ji)和鍍(du)鋅(xin)(xin)(xin)板容(rong)易發(fa)生(sheng)(sheng)粘連(lian)，增(zeng)加修磨次數。由(you)此可(ke)見，鉻(ge)鋯銅(tong)(tong)對于鍍(du)鋅(xin)(xin)(xin)板焊(han)(han)接(jie)(jie)來說反(fan)而不是一(yi)種理(li)想的(de)(de)(de)電(dian)(dian)極(ji)(ji)材(cai)料(liao)。

對于目前使用鉻鋯銅作為電(dian)(dian)(dian)極(ji)材料焊(han)接(jie)(jie)鍍鋅板，電(dian)(dian)(dian)極(ji)失效主要有3個方(fang)面：首先電(dian)(dian)(dian)極(ji)變軟(ruan)，出(chu)現(xian)(xian)(xian)蘑菇頭狀，使電(dian)(dian)(dian)極(ji)使用壽(shou)命變短，影響(xiang)焊(han)接(jie)(jie)質量(liang)；其次，焊(han)接(jie)(jie)過程中(zhong)出(chu)現(xian)(xian)(xian)“炸槍”，火花過大，焊(han)點(dian)質量(liang)差(cha)，出(chu)現(xian)(xian)(xian)毛邊、飛刺；出(chu)現(xian)(xian)(xian)焊(han)接(jie)(jie)工件(jian)與電(dian)(dian)(dian)極(ji)粘連現(xian)(xian)(xian)象(xiang)，導致電(dian)(dian)(dian)極(ji)燒蝕，如(ru)圖3所示，工件(jian)虛(xu)焊(han)、電(dian)(dian)(dian)極(ji)脫落，嚴重影響(xiang)焊(han)接(jie)(jie)質量(liang)和生產效率。

2.失效(xiao)原因分析

汽(qi)車電(dian)(dian)阻焊(han)焊(han)接過程(cheng)是高(gao)溫(wen)冶金(jin)過程(cheng)，電(dian)(dian)極(ji)的(de)(de)(de)不(bu)(bu)同(tong)(tong)位置，溫(wen)度有(you)所不(bu)(bu)同(tong)(tong)。由于在焊(han)接時(shi)溫(wen)度很(hen)高(gao)，在導致(zhi)鋼板(ban)軟(ruan)化(hua)(hua)(hua)產生塑(su)性變(bian)形(xing)的(de)(de)(de)同(tong)(tong)時(shi)，也會(hui)使電(dian)(dian)極(ji)發生軟(ruan)化(hua)(hua)(hua)，因此會(hui)使電(dian)(dian)極(ji)的(de)(de)(de)形(xing)狀(zhuang)發生變(bian)化(hua)(hua)(hua)，受壓力影響，出(chu)現蘑菇頭(tou)狀(zhuang)。不(bu)(bu)同(tong)(tong)材(cai)(cai)料(liao)的(de)(de)(de)軟(ruan)化(hua)(hua)(hua)溫(wen)度不(bu)(bu)盡相(xiang)同(tong)(tong)，這(zhe)是材(cai)(cai)料(liao)的(de)(de)(de)物理特性決(jue)定(ding)的(de)(de)(de)，對(dui)于目汽(qi)車焊(han)接使用的(de)(de)(de)鉻(ge)鋯銅電(dian)(dian)極(ji)材(cai)(cai)料(liao)，軟(ruan)化(hua)(hua)(hua)溫(wen)度不(bu)(bu)超過550℃，然而對(dui)于焊(han)接需要(yao)，電(dian)(dian)極(ji)需要(yao)抵抗(kang)大約900℃的(de)(de)(de)溫(wen)度。所以出(chu)現電(dian)(dian)極(ji)軟(ruan)化(hua)(hua)(hua)，蘑菇頭(tou)狀(zhuang)失(shi)效(xiao)(xiao)(xiao)，是電(dian)(dian)阻焊(han)電(dian)(dian)極(ji)材(cai)(cai)料(liao)作為(wei)(wei)焊(han)接消耗(hao)品的(de)(de)(de)主要(yao)的(de)(de)(de)失(shi)效(xiao)(xiao)(xiao)現象，工作人員也通(tong)過各(ge)種(zhong)方法來盡量(liang)減慢這(zhe)種(zhong)失(shi)效(xiao)(xiao)(xiao)現象。對(dui)于鍍(du)鋅(xin)板(ban)焊(han)接，為(wei)(wei)了(le)緩(huan)解電(dian)(dian)極(ji)與鍍(du)鋅(xin)板(ban)的(de)(de)(de)粘連，往(wang)往(wang)通(tong)過加大電(dian)(dian)流的(de)(de)(de)方式來擊穿(chuan)鍍(du)鋅(xin)板(ban)的(de)(de)(de)鋅(xin)層，從而導致(zhi)鉻(ge)鋯銅電(dian)(dian)極(ji)材(cai)(cai)料(liao)在焊(han)接鍍(du)鋅(xin)板(ban)時(shi)出(chu)現蘑菇頭(tou)失(shi)效(xiao)(xiao)(xiao)的(de)(de)(de)現象更(geng)為(wei)(wei)嚴重，使用壽命更(geng)短。