鎢(wu)極(ji)惰(duo)(duo)性氣(qi)(qi)(qi)體保(bao)護(hu)電(dian)(dian)(dian)(dian)弧(hu)焊(han)(han)(han)(han)(han)(han)(han)(han)（tungsten inert gas welding，TIG），從(cong)屬于GTAW中(zhong)的(de)非熔(rong)(rong)化(hua)極(ji)惰(duo)(duo)性氣(qi)(qi)(qi)體保(bao)護(hu)焊(han)(han)(han)(han)(han)(han)(han)(han)，焊(han)(han)(han)(han)(han)(han)(han)(han)接(jie)時(shi)鎢(wu)極(ji)只起導電(dian)(dian)(dian)(dian)作用，不(bu)作填充金(jin)屬（不(bu)熔(rong)(rong)化(hua)），如圖4-30所示。根據保(bao)護(hu)氣(qi)(qi)(qi)體的(de)不(bu)同，分為(wei)鎢(wu)極(ji)氬(ya)(ya)弧(hu)焊(han)(han)(han)(han)(han)(han)(han)(han)和鎢(wu)極(ji)氦(hai)弧(hu)焊(han)(han)(han)(han)(han)(han)(han)(han)。焊(han)(han)(han)(han)(han)(han)(han)(han)接(jie)時(shi)，惰(duo)(duo)性氣(qi)(qi)(qi)體氬(ya)(ya)氣(qi)(qi)(qi)或(huo)氦(hai)氣(qi)(qi)(qi)（Ar或(huo)He）通(tong)(tong)過焊(han)(han)(han)(han)(han)(han)(han)(han)槍或(huo)其他裝置(zhi)加(jia)入焊(han)(han)(han)(han)(han)(han)(han)(han)接(jie)區(qu)（或(huo)待焊(han)(han)(han)(han)(han)(han)(han)(han)區(qu)），鎢(wu)極(ji)與(yu)被焊(han)(han)(han)(han)(han)(han)(han)(han)工(gong)件之(zhi)間通(tong)(tong)電(dian)(dian)(dian)(dian)產生電(dian)(dian)(dian)(dian)弧(hu)，電(dian)(dian)(dian)(dian)弧(hu)在惰(duo)(duo)性氣(qi)(qi)(qi)體的(de)氣(qi)(qi)(qi)氛中(zhong)燃(ran)燒(shao)。氬(ya)(ya)氣(qi)(qi)(qi)或(huo)氦(hai)氣(qi)(qi)(qi)（Ar或(huo)He）在焊(han)(han)(han)(han)(han)(han)(han)(han)接(jie)過程中(zhong)與(yu)鎢(wu)極(ji)、焊(han)(han)(han)(han)(han)(han)(han)(han)件、填充焊(han)(han)(han)(han)(han)(han)(han)(han)絲不(bu)發(fa)生任(ren)何化(hua)學、冶金(jin)作用、惰(duo)(duo)性氣(qi)(qi)(qi)體保(bao)護(hu)焊(han)(han)(han)(han)(han)(han)(han)(han)的(de)顯(xian)著(zhu)特點是電(dian)(dian)(dian)(dian)弧(hu)燃(ran)燒(shao)穩(wen)定，能(neng)有效地隔(ge)絕周圍空氣(qi)(qi)(qi)，使(shi)熔(rong)(rong)池、填充絲不(bu)被氧化(hua)和氮化(hua)，因而能(neng)獲得(de)高質量(liang)焊(han)(han)(han)(han)(han)(han)(han)(han)縫，且能(neng)進行全位置(zhi)焊(han)(han)(han)(han)(han)(han)(han)(han)接(jie)。但鎢(wu)極(ji)所通(tong)(tong)過的(de)電(dian)(dian)(dian)(dian)流(liu)密(mi)(mi)度(du)(du)受到(dao)限制(zhi)，若通(tong)(tong)過電(dian)(dian)(dian)(dian)流(liu)密(mi)(mi)度(du)(du)太(tai)大，鎢(wu)極(ji)會燒(shao)損，使(shi)焊(han)(han)(han)(han)(han)(han)(han)(han)縫金(jin)屬產生夾鎢(wu)缺(que)欠。由于鎢(wu)極(ji)氬(ya)(ya)弧(hu)焊(han)(han)(han)(han)(han)(han)(han)(han)電(dian)(dian)(dian)(dian)弧(hu)能(neng)量(liang)密(mi)(mi)度(du)(du)低，也不(bu)能(neng)獲得(de)較大的(de)熔(rong)(rong)深和較高的(de)生產率(lv)。采用鎢(wu)極(ji)氦(hai)弧(hu)焊(han)(han)(han)(han)(han)(han)(han)(han)時(shi)，使(shi)用與(yu)鎢(wu)極(ji)氬(ya)(ya)弧(hu)焊(han)(han)(han)(han)(han)(han)(han)(han)同樣的(de)電(dian)(dian)(dian)(dian)流(liu)密(mi)(mi)度(du)(du)，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(wu)極(ji)氬(ya)(ya)弧(hu)(hu)焊(han)(han)時，母材金屬加(jia)熱(re)特(te)點（主要指能(neng)量密度和(he)(he)熱(re)功率大小）介于氣(qi)焊(han)(han)和(he)(he)焊(han)(han)條電弧(hu)(hu)焊(han)(han)之間，在(zai)很(hen)小的焊(han)(han)接電流(liu)（≤10A）下(xia)(xia)，電弧(hu)(hu)仍可穩(wen)定燃燒，特(te)別(bie)適于焊(han)(han)接薄件或(huo)超薄件奧氏體型不銹鋼的焊(han)(han)接構件。鎢(wu)極(ji)氬(ya)(ya)弧(hu)(hu)焊(han)(han)時能(neng)清晰(xi)地(di)觀(guan)察到焊(han)(han)接熔(rong)池和(he)(he)熔(rong)透(tou)情況(kuang)、因此，在(zai)要求(qiu)保證(zheng)焊(han)(han)透(tou)及要求(qiu)背(bei)面成形的情況(kuang)下(xia)(xia)，單面焊(han)(han)采用(yong)(yong)內壁(bi)（或(huo)背(bei)面）通氬(ya)(ya)氣(qi)的鎢(wu)極(ji)氬(ya)(ya)弧(hu)(hu)打底焊(han)(han)的方法，在(zai)國內外已(yi)得到普遍應用(yong)(yong)。鎢(wu)極(ji)氬(ya)(ya)弧(hu)(hu)焊(han)(han)采用(yong)(yong)的填(tian)充絲為裸焊(han)(han)絲，在(zai)施焊(han)(han)過程中(zhong)，不會產生飛(fei)濺、焊(han)(han)縫(feng)成形美觀(guan)，焊(han)(han)縫(feng)上(shang)不存在(zai)渣殼，焊(han)(han)后不需清理(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）。