鎢(wu)極(ji)氬(ya)弧(hu)(hu)焊(han)(han)雖然(ran)能(neng)獲得優良的(de)(de)焊(han)(han)接質量，但由于受到鎢(wu)極(ji)許用電(dian)流的(de)(de)限(xian)制，焊(han)(han)接電(dian)流不能(neng)用得太大(da)。一般情況下(xia)，不開坡口(kou)對(dui)接鎢(wu)極(ji)氬(ya)弧(hu)(hu)焊(han)(han)時，可以(yi)焊(han)(han)透(tou)厚度小于3mm的(de)(de)母材，超過(guo)此(ci)厚度的(de)(de)焊(han)(han)件如要全焊(han)(han)透(tou)，需(xu)對(dui)母材開坡口(kou)。由于鎢(wu)極(ji)氬(ya)弧(hu)(hu)焊(han)(han)焊(han)(han)接速度慢，導致焊(han)(han)接變形增加、焊(han)(han)接接頭抗腐(fu)蝕性(xing)能(neng)下(xia)降，而(er)且鎢(wu)極(ji)氬(ya)弧(hu)(hu)焊(han)(han)焊(han)(han)接時產(chan)生(sheng)一定量的(de)(de)放射線對(dui)人體有一定的(de)(de)損害，因此(ci)焊(han)(han)接中(zhong)、厚板奧氏(shi)體不銹鋼時已(yi)不能(neng)很好的(de)(de)滿足實際生(sheng)產(chan)的(de)(de)需(xu)求。

  熔(rong)(rong)化極氣體(ti)保護焊(han)(han)(han)用(yong)焊(han)(han)(han)絲作為電(dian)(dian)極（和(he)填充金(jin)屬），焊(han)(han)(han)接(jie)電(dian)(dian)流可以大(da)大(da)提高。由于熔(rong)(rong)深大(da)，焊(han)(han)(han)絲熔(rong)(rong)敷速度快，提高了(le)生產(chan)效率，改善了(le)勞(lao)動條(tiao)件(jian)，減(jian)少了(le)焊(han)(han)(han)接(jie)變形，同時還有利于提高焊(han)(han)(han)接(jie)接(jie)頭耐腐(fu)蝕性能(neng)。熔(rong)(rong)化極氣體(ti)保護焊(han)(han)(han)適用(yong)于中(zhong)等和(he)大(da)厚度母材的焊(han)(han)(han)接(jie)。

  熔(rong)(rong)(rong)(rong)化(hua)極(ji)(ji)氣體(ti)保(bao)護(hu)焊(han)(han)，是(shi)用可熔(rong)(rong)(rong)(rong)化(hua)的(de)(de)(de)焊(han)(han)絲(si)與被焊(han)(han)工(gong)件之間(jian)的(de)(de)(de)電(dian)弧(hu)作為熱源來熔(rong)(rong)(rong)(rong)化(hua)焊(han)(han)絲(si)和(he)母材金屬，并向焊(han)(han)接區輸(shu)送(song)保(bao)護(hu)氣體(ti)，使(shi)電(dian)弧(hu)、熔(rong)(rong)(rong)(rong)化(hua)的(de)(de)(de)焊(han)(han)絲(si)、熔(rong)(rong)(rong)(rong)池及附近金屬免受(shou)周圍空氣的(de)(de)(de)有(you)害作用，通(tong)過(guo)連續送(song)進焊(han)(han)絲(si)不斷熔(rong)(rong)(rong)(rong)化(hua)并過(guo)渡(du)到(dao)熔(rong)(rong)(rong)(rong)池，形成(cheng)焊(han)(han)縫金屬。熔(rong)(rong)(rong)(rong)化(hua)極(ji)(ji)氣體(ti)保(bao)護(hu)焊(han)(han)焊(han)(han)接奧氏(shi)體(ti)型不銹鋼時(shi)的(de)(de)(de)熔(rong)(rong)(rong)(rong)滴(di)過(guo)渡(du)有(you)滴(di)狀過(guo)渡(du)、短路過(guo)渡(du)和(he)噴(pen)(pen)射(she)過(guo)渡(du)3種。其中(zhong)滴(di)狀過(guo)渡(du)時(shi)，熔(rong)(rong)(rong)(rong)滴(di)直徑比(bi)焊(han)(han)絲(si)直徑大(da)，飛濺較大(da)，導致(zhi)焊(han)(han)接過(guo)程(cheng)不穩定(ding)，在生(sheng)產(chan)上極(ji)(ji)少使(shi)用。短路過(guo)渡(du)電(dian)弧(hu)間(jian)隙小(xiao)，電(dian)弧(hu)電(dian)壓(ya)較低，電(dian)弧(hu)功率比(bi)較小(xiao)，適用于(yu)薄板(ban)焊(han)(han)接。生(sheng)產(chan)中(zhong)應用最為廣(guang)泛的(de)(de)(de)是(shi)噴(pen)(pen)射(she)過(guo)渡(du)，對于(yu)一定(ding)的(de)(de)(de)焊(han)(han)絲(si)和(he)保(bao)護(hu)氣體(ti)，當焊(han)(han)接電(dian)流增大(da)到(dao)臨界電(dian)流值時(shi)（圖4-44），焊(han)(han)絲(si)端頭熔(rong)(rong)(rong)(rong)化(hua)的(de)(de)(de)金屬被壓(ya)縮(suo)成(cheng)筆尖狀，以(yi)細小(xiao)熔(rong)(rong)(rong)(rong)滴(di)從(cong)液(ye)柱尖端高速軸(zhou)向射(she)入(ru)熔(rong)(rong)(rong)(rong)池，即噴(pen)(pen)射(she)過(guo)渡(du)，如圖4-45所示。