鎢(wu)極氬(ya)弧(hu)(hu)(hu)焊(han)(han)(han)雖然能(neng)獲得優良的(de)(de)焊(han)(han)(han)接(jie)(jie)(jie)質量，但(dan)由(you)于(yu)受到鎢(wu)極許用電(dian)(dian)流的(de)(de)限制，焊(han)(han)(han)接(jie)(jie)(jie)電(dian)(dian)流不(bu)(bu)能(neng)用得太大(da)。一般(ban)情況下(xia)，不(bu)(bu)開坡口(kou)對接(jie)(jie)(jie)鎢(wu)極氬(ya)弧(hu)(hu)(hu)焊(han)(han)(han)時，可以焊(han)(han)(han)透(tou)厚(hou)度(du)小于(yu)3mm的(de)(de)母材，超過此(ci)(ci)厚(hou)度(du)的(de)(de)焊(han)(han)(han)件如(ru)要全焊(han)(han)(han)透(tou)，需(xu)對母材開坡口(kou)。由(you)于(yu)鎢(wu)極氬(ya)弧(hu)(hu)(hu)焊(han)(han)(han)焊(han)(han)(han)接(jie)(jie)(jie)速度(du)慢，導致焊(han)(han)(han)接(jie)(jie)(jie)變形增加、焊(han)(han)(han)接(jie)(jie)(jie)接(jie)(jie)(jie)頭抗(kang)腐(fu)蝕(shi)性能(neng)下(xia)降(jiang)，而且鎢(wu)極氬(ya)弧(hu)(hu)(hu)焊(han)(han)(han)焊(han)(han)(han)接(jie)(jie)(jie)時產(chan)生一定(ding)量的(de)(de)放射線對人體(ti)有一定(ding)的(de)(de)損害，因此(ci)(ci)焊(han)(han)(han)接(jie)(jie)(jie)中、厚(hou)板奧氏體(ti)不(bu)(bu)銹鋼(gang)時已(yi)不(bu)(bu)能(neng)很好的(de)(de)滿足實際生產(chan)的(de)(de)需(xu)求。

  熔(rong)(rong)化極(ji)氣(qi)體(ti)保(bao)(bao)護焊(han)用(yong)焊(han)絲(si)作為電(dian)極(ji)（和填充(chong)金屬），焊(han)接(jie)(jie)電(dian)流可以大(da)大(da)提(ti)(ti)高(gao)。由于熔(rong)(rong)深(shen)大(da)，焊(han)絲(si)熔(rong)(rong)敷(fu)速度快(kuai)，提(ti)(ti)高(gao)了(le)生產效(xiao)率(lv)，改善(shan)了(le)勞動條件(jian)，減少(shao)了(le)焊(han)接(jie)(jie)變形，同時(shi)還有利于提(ti)(ti)高(gao)焊(han)接(jie)(jie)接(jie)(jie)頭(tou)耐腐蝕性(xing)能。熔(rong)(rong)化極(ji)氣(qi)體(ti)保(bao)(bao)護焊(han)適用(yong)于中等(deng)和大(da)厚度母材的(de)焊(han)接(jie)(jie)。

  熔(rong)(rong)(rong)(rong)(rong)(rong)化(hua)極氣(qi)體保護(hu)(hu)焊(han)(han)(han)(han)(han)，是用(yong)(yong)可(ke)熔(rong)(rong)(rong)(rong)(rong)(rong)化(hua)的(de)(de)焊(han)(han)(han)(han)(han)絲(si)(si)與被焊(han)(han)(han)(han)(han)工件之間的(de)(de)電(dian)(dian)(dian)弧(hu)作(zuo)為熱源來熔(rong)(rong)(rong)(rong)(rong)(rong)化(hua)焊(han)(han)(han)(han)(han)絲(si)(si)和(he)母材金屬(shu)，并(bing)向焊(han)(han)(han)(han)(han)接(jie)區輸送保護(hu)(hu)氣(qi)體，使電(dian)(dian)(dian)弧(hu)、熔(rong)(rong)(rong)(rong)(rong)(rong)化(hua)的(de)(de)焊(han)(han)(han)(han)(han)絲(si)(si)、熔(rong)(rong)(rong)(rong)(rong)(rong)池及附(fu)近金屬(shu)免受(shou)周圍(wei)空氣(qi)的(de)(de)有害(hai)作(zuo)用(yong)(yong)，通(tong)過(guo)(guo)(guo)(guo)連續送進焊(han)(han)(han)(han)(han)絲(si)(si)不斷熔(rong)(rong)(rong)(rong)(rong)(rong)化(hua)并(bing)過(guo)(guo)(guo)(guo)渡(du)(du)到熔(rong)(rong)(rong)(rong)(rong)(rong)池，形成(cheng)焊(han)(han)(han)(han)(han)縫金屬(shu)。熔(rong)(rong)(rong)(rong)(rong)(rong)化(hua)極氣(qi)體保護(hu)(hu)焊(han)(han)(han)(han)(han)焊(han)(han)(han)(han)(han)接(jie)奧(ao)氏體型不銹鋼時的(de)(de)熔(rong)(rong)(rong)(rong)(rong)(rong)滴(di)(di)過(guo)(guo)(guo)(guo)渡(du)(du)有滴(di)(di)狀(zhuang)過(guo)(guo)(guo)(guo)渡(du)(du)、短路過(guo)(guo)(guo)(guo)渡(du)(du)和(he)噴(pen)射(she)(she)過(guo)(guo)(guo)(guo)渡(du)(du)3種。其中(zhong)滴(di)(di)狀(zhuang)過(guo)(guo)(guo)(guo)渡(du)(du)時，熔(rong)(rong)(rong)(rong)(rong)(rong)滴(di)(di)直(zhi)徑比焊(han)(han)(han)(han)(han)絲(si)(si)直(zhi)徑大(da)，飛(fei)濺較(jiao)大(da)，導致焊(han)(han)(han)(han)(han)接(jie)過(guo)(guo)(guo)(guo)程不穩定，在生產上極少(shao)使用(yong)(yong)。短路過(guo)(guo)(guo)(guo)渡(du)(du)電(dian)(dian)(dian)弧(hu)間隙小(xiao)，電(dian)(dian)(dian)弧(hu)電(dian)(dian)(dian)壓較(jiao)低(di)，電(dian)(dian)(dian)弧(hu)功率比較(jiao)小(xiao)，適(shi)用(yong)(yong)于薄(bo)板焊(han)(han)(han)(han)(han)接(jie)。生產中(zhong)應(ying)用(yong)(yong)最為廣泛的(de)(de)是噴(pen)射(she)(she)過(guo)(guo)(guo)(guo)渡(du)(du)，對于一定的(de)(de)焊(han)(han)(han)(han)(han)絲(si)(si)和(he)保護(hu)(hu)氣(qi)體，當焊(han)(han)(han)(han)(han)接(jie)電(dian)(dian)(dian)流增大(da)到臨界電(dian)(dian)(dian)流值時（圖(tu)4-44），焊(han)(han)(han)(han)(han)絲(si)(si)端(duan)(duan)頭(tou)熔(rong)(rong)(rong)(rong)(rong)(rong)化(hua)的(de)(de)金屬(shu)被壓縮(suo)成(cheng)筆尖狀(zhuang)，以細小(xiao)熔(rong)(rong)(rong)(rong)(rong)(rong)滴(di)(di)從(cong)液柱(zhu)尖端(duan)(duan)高(gao)速(su)軸(zhou)向射(she)(she)入熔(rong)(rong)(rong)(rong)(rong)(rong)池，即噴(pen)射(she)(she)過(guo)(guo)(guo)(guo)渡(du)(du)，如圖(tu)4-45所示。