鎢極(ji)氬(ya)(ya)弧(hu)(hu)焊(han)(han)(han)(han)雖然能獲得(de)(de)優(you)良的(de)焊(han)(han)(han)(han)接(jie)質量，但由(you)于(yu)受到鎢極(ji)許用電流的(de)限制，焊(han)(han)(han)(han)接(jie)電流不能用得(de)(de)太(tai)大(da)。一(yi)般情(qing)況下(xia)，不開坡口對(dui)接(jie)鎢極(ji)氬(ya)(ya)弧(hu)(hu)焊(han)(han)(han)(han)時，可(ke)以焊(han)(han)(han)(han)透厚(hou)度(du)小于(yu)3mm的(de)母材，超(chao)過此厚(hou)度(du)的(de)焊(han)(han)(han)(han)件(jian)如要(yao)全焊(han)(han)(han)(han)透，需(xu)對(dui)母材開坡口。由(you)于(yu)鎢極(ji)氬(ya)(ya)弧(hu)(hu)焊(han)(han)(han)(han)焊(han)(han)(han)(han)接(jie)速度(du)慢，導(dao)致(zhi)焊(han)(han)(han)(han)接(jie)變形增(zeng)加(jia)、焊(han)(han)(han)(han)接(jie)接(jie)頭抗腐蝕(shi)性(xing)能下(xia)降(jiang)，而(er)且鎢極(ji)氬(ya)(ya)弧(hu)(hu)焊(han)(han)(han)(han)焊(han)(han)(han)(han)接(jie)時產生(sheng)一(yi)定(ding)量的(de)放射線對(dui)人(ren)體有一(yi)定(ding)的(de)損害，因(yin)此焊(han)(han)(han)(han)接(jie)中、厚(hou)板奧氏體不銹(xiu)鋼時已不能很好的(de)滿足實際(ji)生(sheng)產的(de)需(xu)求。

  熔(rong)化極(ji)氣體保(bao)護焊(han)(han)(han)用(yong)焊(han)(han)(han)絲作為(wei)電極(ji)（和填充金屬(shu)），焊(han)(han)(han)接電流可以大大提高(gao)。由于熔(rong)深大，焊(han)(han)(han)絲熔(rong)敷速度快，提高(gao)了生產效率(lv)，改善了勞動條(tiao)件，減少了焊(han)(han)(han)接變(bian)形，同時還有利于提高(gao)焊(han)(han)(han)接接頭耐(nai)腐蝕(shi)性(xing)能。熔(rong)化極(ji)氣體保(bao)護焊(han)(han)(han)適用(yong)于中(zhong)等和大厚度母材的焊(han)(han)(han)接。

  熔(rong)(rong)(rong)(rong)(rong)化(hua)(hua)(hua)極氣(qi)體(ti)(ti)(ti)保(bao)護焊(han)(han)(han)(han)，是用(yong)(yong)可熔(rong)(rong)(rong)(rong)(rong)化(hua)(hua)(hua)的(de)(de)(de)(de)焊(han)(han)(han)(han)絲(si)(si)(si)與被焊(han)(han)(han)(han)工件之(zhi)間的(de)(de)(de)(de)電(dian)(dian)弧(hu)(hu)作為熱源(yuan)來熔(rong)(rong)(rong)(rong)(rong)化(hua)(hua)(hua)焊(han)(han)(han)(han)絲(si)(si)(si)和(he)母材金屬(shu)，并向焊(han)(han)(han)(han)接(jie)區輸(shu)送保(bao)護氣(qi)體(ti)(ti)(ti)，使電(dian)(dian)弧(hu)(hu)、熔(rong)(rong)(rong)(rong)(rong)化(hua)(hua)(hua)的(de)(de)(de)(de)焊(han)(han)(han)(han)絲(si)(si)(si)、熔(rong)(rong)(rong)(rong)(rong)池(chi)及附近金屬(shu)免受周圍空氣(qi)的(de)(de)(de)(de)有害作用(yong)(yong)，通過(guo)(guo)連續送進焊(han)(han)(han)(han)絲(si)(si)(si)不斷熔(rong)(rong)(rong)(rong)(rong)化(hua)(hua)(hua)并過(guo)(guo)渡(du)(du)到熔(rong)(rong)(rong)(rong)(rong)池(chi)，形成焊(han)(han)(han)(han)縫金屬(shu)。熔(rong)(rong)(rong)(rong)(rong)化(hua)(hua)(hua)極氣(qi)體(ti)(ti)(ti)保(bao)護焊(han)(han)(han)(han)焊(han)(han)(han)(han)接(jie)奧氏(shi)體(ti)(ti)(ti)型不銹鋼時(shi)的(de)(de)(de)(de)熔(rong)(rong)(rong)(rong)(rong)滴(di)過(guo)(guo)渡(du)(du)有滴(di)狀過(guo)(guo)渡(du)(du)、短(duan)路過(guo)(guo)渡(du)(du)和(he)噴射過(guo)(guo)渡(du)(du)3種。其(qi)中(zhong)滴(di)狀過(guo)(guo)渡(du)(du)時(shi)，熔(rong)(rong)(rong)(rong)(rong)滴(di)直徑(jing)(jing)比(bi)焊(han)(han)(han)(han)絲(si)(si)(si)直徑(jing)(jing)大，飛(fei)濺較大，導致焊(han)(han)(han)(han)接(jie)過(guo)(guo)程不穩定，在生產上極少使用(yong)(yong)。短(duan)路過(guo)(guo)渡(du)(du)電(dian)(dian)弧(hu)(hu)間隙(xi)小，電(dian)(dian)弧(hu)(hu)電(dian)(dian)壓較低，電(dian)(dian)弧(hu)(hu)功率比(bi)較小，適用(yong)(yong)于薄板(ban)焊(han)(han)(han)(han)接(jie)。生產中(zhong)應用(yong)(yong)最為廣(guang)泛的(de)(de)(de)(de)是噴射過(guo)(guo)渡(du)(du)，對于一定的(de)(de)(de)(de)焊(han)(han)(han)(han)絲(si)(si)(si)和(he)保(bao)護氣(qi)體(ti)(ti)(ti)，當焊(han)(han)(han)(han)接(jie)電(dian)(dian)流增大到臨界電(dian)(dian)流值時(shi)（圖4-44），焊(han)(han)(han)(han)絲(si)(si)(si)端(duan)頭熔(rong)(rong)(rong)(rong)(rong)化(hua)(hua)(hua)的(de)(de)(de)(de)金屬(shu)被壓縮(suo)成筆尖(jian)(jian)狀，以細(xi)小熔(rong)(rong)(rong)(rong)(rong)滴(di)從液柱尖(jian)(jian)端(duan)高速(su)軸向射入熔(rong)(rong)(rong)(rong)(rong)池(chi)，即噴射過(guo)(guo)渡(du)(du)，如(ru)圖4-45所示。