鎢(wu)(wu)(wu)極(ji)(ji)惰性(xing)氣(qi)(qi)體保護電(dian)(dian)(dian)(dian)(dian)弧(hu)(hu)焊(han)（tungsten inert gas welding，TIG），從(cong)屬(shu)(shu)于GTAW中的(de)非熔化(hua)(hua)極(ji)(ji)惰性(xing)氣(qi)(qi)體保護焊(han)，焊(han)接時(shi)鎢(wu)(wu)(wu)極(ji)(ji)只(zhi)起(qi)導電(dian)(dian)(dian)(dian)(dian)作(zuo)用(yong)，不(bu)(bu)作(zuo)填(tian)充金屬(shu)(shu)（不(bu)(bu)熔化(hua)(hua)），如(ru)圖4-30所示。根據保護氣(qi)(qi)體的(de)不(bu)(bu)同，分(fen)為鎢(wu)(wu)(wu)極(ji)(ji)氬(ya)弧(hu)(hu)焊(han)和鎢(wu)(wu)(wu)極(ji)(ji)氦弧(hu)(hu)焊(han)。焊(han)接時(shi)，惰性(xing)氣(qi)(qi)體氬(ya)氣(qi)(qi)或(huo)(huo)氦氣(qi)(qi)（Ar或(huo)(huo)He）通過焊(han)槍或(huo)(huo)其他裝(zhuang)置加(jia)入焊(han)接區(qu)（或(huo)(huo)待焊(han)區(qu)），鎢(wu)(wu)(wu)極(ji)(ji)與(yu)被焊(han)工件(jian)之間通電(dian)(dian)(dian)(dian)(dian)產生(sheng)電(dian)(dian)(dian)(dian)(dian)弧(hu)(hu)，電(dian)(dian)(dian)(dian)(dian)弧(hu)(hu)在(zai)惰性(xing)氣(qi)(qi)體的(de)氣(qi)(qi)氛中燃(ran)(ran)燒。氬(ya)氣(qi)(qi)或(huo)(huo)氦氣(qi)(qi)（Ar或(huo)(huo)He）在(zai)焊(han)接過程(cheng)中與(yu)鎢(wu)(wu)(wu)極(ji)(ji)、焊(han)件(jian)、填(tian)充焊(han)絲不(bu)(bu)發生(sheng)任(ren)何(he)化(hua)(hua)學(xue)、冶金作(zuo)用(yong)、惰性(xing)氣(qi)(qi)體保護焊(han)的(de)顯著特點是電(dian)(dian)(dian)(dian)(dian)弧(hu)(hu)燃(ran)(ran)燒穩定，能(neng)有效地隔(ge)絕周圍空氣(qi)(qi)，使熔池、填(tian)充絲不(bu)(bu)被氧化(hua)(hua)和氮(dan)化(hua)(hua)，因而(er)能(neng)獲得(de)高質量(liang)焊(han)縫(feng)，且能(neng)進行全位(wei)置焊(han)接。但(dan)鎢(wu)(wu)(wu)極(ji)(ji)所通過的(de)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)密(mi)度受到限制，若通過電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)密(mi)度太大(da)(da)，鎢(wu)(wu)(wu)極(ji)(ji)會(hui)燒損，使焊(han)縫(feng)金屬(shu)(shu)產生(sheng)夾鎢(wu)(wu)(wu)缺欠。由(you)于鎢(wu)(wu)(wu)極(ji)(ji)氬(ya)弧(hu)(hu)焊(han)電(dian)(dian)(dian)(dian)(dian)弧(hu)(hu)能(neng)量(liang)密(mi)度低(di)，也不(bu)(bu)能(neng)獲得(de)較大(da)(da)的(de)熔深和較高的(de)生(sheng)產率。采用(yong)鎢(wu)(wu)(wu)極(ji)(ji)氦弧(hu)(hu)焊(han)時(shi)，使用(yong)與(yu)鎢(wu)(wu)(wu)極(ji)(ji)氬(ya)弧(hu)(hu)焊(han)同樣的(de)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)密(mi)度，鎢極氦弧焊的電弧電壓較高，電弧熱功率高。氦氣作為熱能的載體，它的熱傳導能比氬氣約大9倍。這樣，就有大量的熱能輸送到焊接熔池中去，從而獲得較大的熔深和得到較高的生產率。但是氦氣來源較為困難，價格比氬氣高20～30倍、同時氦氣的密度比氬氣小，要達到同樣的保護效果，氦氣的消耗量高出很多，所以氨弧焊成本很高。焊接薄的和中等厚度的奧氏體型不(bu)銹鋼板一般極少采用，只有在焊接關鍵焊件時才使用氦弧焊。

  鎢(wu)(wu)極(ji)氬(ya)弧(hu)(hu)焊(han)(han)(han)(han)時(shi)，母(mu)材金屬(shu)加熱(re)特(te)點（主要(yao)指能(neng)量(liang)密(mi)度(du)和(he)熱(re)功率大小）介于(yu)氣焊(han)(han)(han)(han)和(he)焊(han)(han)(han)(han)條電弧(hu)(hu)焊(han)(han)(han)(han)之間，在(zai)很小的(de)(de)焊(han)(han)(han)(han)接電流（≤10A）下，電弧(hu)(hu)仍可(ke)穩定燃燒，特(te)別適于(yu)焊(han)(han)(han)(han)接薄件(jian)或超(chao)薄件(jian)奧氏體型不(bu)(bu)銹鋼的(de)(de)焊(han)(han)(han)(han)接構(gou)件(jian)。鎢(wu)(wu)極(ji)氬(ya)弧(hu)(hu)焊(han)(han)(han)(han)時(shi)能(neng)清晰地(di)觀察到焊(han)(han)(han)(han)接熔(rong)池和(he)熔(rong)透情況、因此，在(zai)要(yao)求保證焊(han)(han)(han)(han)透及要(yao)求背面成(cheng)形(xing)的(de)(de)情況下，單面焊(han)(han)(han)(han)采(cai)用(yong)內(nei)壁（或背面）通氬(ya)氣的(de)(de)鎢(wu)(wu)極(ji)氬(ya)弧(hu)(hu)打底焊(han)(han)(han)(han)的(de)(de)方法，在(zai)國(guo)內(nei)外已(yi)得(de)到普遍應用(yong)。鎢(wu)(wu)極(ji)氬(ya)弧(hu)(hu)焊(han)(han)(han)(han)采(cai)用(yong)的(de)(de)填充絲為(wei)裸焊(han)(han)(han)(han)絲，在(zai)施焊(han)(han)(han)(han)過程中(zhong)，不(bu)(bu)會產生(sheng)飛濺、焊(han)(han)(han)(han)縫成(cheng)形(xing)美(mei)觀，焊(han)(han)(han)(han)縫上不(bu)(bu)存在(zai)渣殼，焊(han)(han)(han)(han)后(hou)不(bu)(bu)需清理(li)。

  鎢極氬弧焊電弧的熱功率低，焊接速度相對其他電弧焊而言比較小，由于奧氏體不銹鋼管(guan)導熱能力較差，如鎢極氬弧焊的焊接速度很慢時、會導致焊接接頭冷卻速度緩慢，在400～800℃的危險溫度區間停留時間較長，會影響焊接接頭耐腐蝕能力（包括晶間腐蝕和均勻腐蝕）。