鎢(wu)(wu)(wu)極(ji)惰(duo)(duo)性氣(qi)(qi)體(ti)(ti)(ti)保(bao)護(hu)電(dian)(dian)弧(hu)(hu)焊(han)(han)(han)(han)（tungsten inert gas welding，TIG），從屬(shu)于GTAW中(zhong)的(de)非熔化(hua)(hua)極(ji)惰(duo)(duo)性氣(qi)(qi)體(ti)(ti)(ti)保(bao)護(hu)焊(han)(han)(han)(han)，焊(han)(han)(han)(han)接(jie)(jie)時鎢(wu)(wu)(wu)極(ji)只起導電(dian)(dian)作用(yong)(yong)，不(bu)(bu)作填充(chong)金屬(shu)（不(bu)(bu)熔化(hua)(hua)），如圖4-30所示。根據(ju)保(bao)護(hu)氣(qi)(qi)體(ti)(ti)(ti)的(de)不(bu)(bu)同，分為鎢(wu)(wu)(wu)極(ji)氬(ya)弧(hu)(hu)焊(han)(han)(han)(han)和(he)(he)鎢(wu)(wu)(wu)極(ji)氦(hai)弧(hu)(hu)焊(han)(han)(han)(han)。焊(han)(han)(han)(han)接(jie)(jie)時，惰(duo)(duo)性氣(qi)(qi)體(ti)(ti)(ti)氬(ya)氣(qi)(qi)或氦(hai)氣(qi)(qi)（Ar或He）通過(guo)焊(han)(han)(han)(han)槍或其他裝置(zhi)加入焊(han)(han)(han)(han)接(jie)(jie)區（或待焊(han)(han)(han)(han)區），鎢(wu)(wu)(wu)極(ji)與(yu)被焊(han)(han)(han)(han)工(gong)件(jian)之(zhi)間(jian)通電(dian)(dian)產(chan)生電(dian)(dian)弧(hu)(hu)，電(dian)(dian)弧(hu)(hu)在惰(duo)(duo)性氣(qi)(qi)體(ti)(ti)(ti)的(de)氣(qi)(qi)氛中(zhong)燃(ran)燒。氬(ya)氣(qi)(qi)或氦(hai)氣(qi)(qi)（Ar或He）在焊(han)(han)(han)(han)接(jie)(jie)過(guo)程中(zhong)與(yu)鎢(wu)(wu)(wu)極(ji)、焊(han)(han)(han)(han)件(jian)、填充(chong)焊(han)(han)(han)(han)絲(si)不(bu)(bu)發生任何化(hua)(hua)學、冶金作用(yong)(yong)、惰(duo)(duo)性氣(qi)(qi)體(ti)(ti)(ti)保(bao)護(hu)焊(han)(han)(han)(han)的(de)顯著(zhu)特點是電(dian)(dian)弧(hu)(hu)燃(ran)燒穩(wen)定(ding)，能(neng)有(you)效地隔(ge)絕周圍空(kong)氣(qi)(qi)，使(shi)熔池、填充(chong)絲(si)不(bu)(bu)被氧化(hua)(hua)和(he)(he)氮化(hua)(hua)，因而能(neng)獲得高(gao)質量焊(han)(han)(han)(han)縫(feng)，且(qie)能(neng)進行全位置(zhi)焊(han)(han)(han)(han)接(jie)(jie)。但鎢(wu)(wu)(wu)極(ji)所通過(guo)的(de)電(dian)(dian)流密(mi)度受到限(xian)制，若通過(guo)電(dian)(dian)流密(mi)度太大，鎢(wu)(wu)(wu)極(ji)會燒損(sun)，使(shi)焊(han)(han)(han)(han)縫(feng)金屬(shu)產(chan)生夾鎢(wu)(wu)(wu)缺欠。由于鎢(wu)(wu)(wu)極(ji)氬(ya)弧(hu)(hu)焊(han)(han)(han)(han)電(dian)(dian)弧(hu)(hu)能(neng)量密(mi)度低，也(ye)不(bu)(bu)能(neng)獲得較大的(de)熔深(shen)和(he)(he)較高(gao)的(de)生產(chan)率。采用(yong)(yong)鎢(wu)(wu)(wu)極(ji)氦(hai)弧(hu)(hu)焊(han)(han)(han)(han)時，使(shi)用(yong)(yong)與(yu)鎢(wu)(wu)(wu)極(ji)氬(ya)弧(hu)(hu)焊(han)(han)(han)(han)同樣的(de)電(dian)(dian)流密(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(ban)一般極少采用，只有在焊接關鍵焊件時才使用氦弧焊。

  鎢極氬(ya)弧(hu)(hu)焊(han)(han)(han)(han)(han)時(shi)，母(mu)材(cai)金屬加(jia)熱特點(dian)（主要(yao)指能(neng)量(liang)密度和(he)熱功(gong)率大小）介于氣焊(han)(han)(han)(han)(han)和(he)焊(han)(han)(han)(han)(han)條(tiao)電弧(hu)(hu)焊(han)(han)(han)(han)(han)之間，在很小的(de)焊(han)(han)(han)(han)(han)接電流（≤10A）下(xia)，電弧(hu)(hu)仍可(ke)穩定燃燒(shao)，特別(bie)適于焊(han)(han)(han)(han)(han)接薄件或超(chao)薄件奧(ao)氏體(ti)型不銹鋼的(de)焊(han)(han)(han)(han)(han)接構件。鎢極氬(ya)弧(hu)(hu)焊(han)(han)(han)(han)(han)時(shi)能(neng)清(qing)晰地觀察到焊(han)(han)(han)(han)(han)接熔(rong)池和(he)熔(rong)透(tou)情況、因此，在要(yao)求保證焊(han)(han)(han)(han)(han)透(tou)及要(yao)求背面成(cheng)(cheng)形的(de)情況下(xia)，單面焊(han)(han)(han)(han)(han)采用(yong)(yong)內(nei)壁（或背面）通氬(ya)氣的(de)鎢極氬(ya)弧(hu)(hu)打底焊(han)(han)(han)(han)(han)的(de)方法(fa)，在國內(nei)外已(yi)得到普(pu)遍(bian)應(ying)用(yong)(yong)。鎢極氬(ya)弧(hu)(hu)焊(han)(han)(han)(han)(han)采用(yong)(yong)的(de)填充絲為(wei)裸焊(han)(han)(han)(han)(han)絲，在施焊(han)(han)(han)(han)(han)過(guo)程中，不會產生(sheng)飛濺、焊(han)(han)(han)(han)(han)縫(feng)成(cheng)(cheng)形美(mei)觀，焊(han)(han)(han)(han)(han)縫(feng)上不存(cun)在渣殼(ke)，焊(han)(han)(han)(han)(han)后不需清(qing)理。

  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）。