奧氏體不銹鋼采用手工鎢極氬弧(hu)焊可以進行各種位置的操作,其中包括水平固定管(全位置)的對接焊,但主適用于薄壁件和打底層的焊接。


  根(gen)據接(jie)頭(tou)的形式,平(ping)焊(han)位置包括對(dui)接(jie)平(ping)焊(han)和平(ping)角焊(han)兩種(zhong)。


①. 對(dui)接平焊


 焊件在(zai)裝配時,為了防止(zhi)焊接(jie)過程中產生變形,應放(fang)在(zai)夾(jia)具中緊固,并在(zai)焊件坡口背面(mian)安放(fang)墊板(ban),墊板(ban)上應開(kai)設凹槽,內通氬氣,保護背面(mian)焊縫,如圖(tu)4-11所示。


11.jpg


  焊(han)(han)接時(shi),首先在定位焊(han)(han)縫根部后10mm左右處開(kai)始引燃電弧,運(yun)弧至定位焊(han)(han)點(dian)根部,此時(shi)焊(han)(han)槍(qiang)畫一個半圓形的圈(quan),在坡口根部形成(cheng)一個熔(rong)孔,熔(rong)孔形成(cheng)后向右側鈍邊處填加(jia)焊(han)(han)絲(si)(si),然(ran)后得向左側運(yun)弧,向左側鈍邊處填加(jia)焊(han)(han)絲(si)(si),再向右運(yun)弧,如此往復循環,逐漸形成(cheng)熔(rong)透焊(han)(han)縫。


  操作過(guo)(guo)(guo)(guo)程中(zhong)要保(bao)持熔(rong)(rong)(rong)孔(kong)(kong)始終(zhong)深入母材0.5~1.0mm,出現熔(rong)(rong)(rong)孔(kong)(kong)后(hou)應立即填充焊(han)絲,這(zhe)時形成(cheng)(cheng)的(de)(de)焊(han)縫才會均勻。如果(guo)填充焊(han)絲過(guo)(guo)(guo)(guo)遲,熔(rong)(rong)(rong)孔(kong)(kong)過(guo)(guo)(guo)(guo)大,反面(mian)焊(han)縫就過(guo)(guo)(guo)(guo)高(gao),甚至產生焊(han)瘤;填充焊(han)絲過(guo)(guo)(guo)(guo)早,若還(huan)未形成(cheng)(cheng)熔(rong)(rong)(rong)孔(kong)(kong),就會產生未焊(han)透(tou)。焊(han)接過(guo)(guo)(guo)(guo)程中(zhong)在不影響視(shi)線(xian)的(de)(de)情況下盡(jin)量采用短弧(hu),以(yi)增(zeng)強(qiang)氬(ya)氣(qi)的(de)(de)保(bao)護效果(guo)和提高(gao)電弧(hu)的(de)(de)穿透(tou)能力。鎢極(ji)端部距熔(rong)(rong)(rong)池表面(mian)以(yi)2~3mm為宜,要注(zhu)意觀察熔(rong)(rong)(rong)池的(de)(de)形狀,熔(rong)(rong)(rong)池應保(bao)持與焊(han)縫軸(zhou)線(xian)對稱,否則焊(han)縫就會偏(pian)斜。


  熔(rong)(rong)(rong)(rong)透的(de)識別:焊(han)(han)接過(guo)程中應通(tong)過(guo)仔細(xi)觀(guan)察熔(rong)(rong)(rong)(rong)池(chi)的(de)變(bian)化來(lai)判斷是否熔(rong)(rong)(rong)(rong)透,以達到單面(mian)焊(han)(han)雙面(mian)成形(xing)的(de)目的(de)。當填充焊(han)(han)絲上(shang)一(yi)顆熔(rong)(rong)(rong)(rong)滴落(luo)入熔(rong)(rong)(rong)(rong)池(chi)時,熔(rong)(rong)(rong)(rong)池(chi)表(biao)面(mian)位(wei)置就會(hui)升高,隨著(zhu)熱量向下(xia)傳輸(shu),基本金屬熔(rong)(rong)(rong)(rong)化形(xing)成熔(rong)(rong)(rong)(rong)孔。由于重力使熔(rong)(rong)(rong)(rong)池(chi)下(xia)沉(chen),于是熔(rong)(rong)(rong)(rong)池(chi)水平下(xia)降,熔(rong)(rong)(rong)(rong)池(chi)表(biao)面(mian)積(ji)擴張,這是焊(han)(han)透的(de)重要標志。如果沒(mei)有焊(han)(han)透,熔(rong)(rong)(rong)(rong)池(chi)便不(bu)會(hui)下(xia)沉(chen)。


  當(dang)運弧(hu)至終焊(han)端(duan)的定位焊(han)縫根部(bu)3~5mm時,焊(han)槍(qiang)畫圈,把(ba)定位焊(han)縫根部(bu)熔化,然后填充2~3滴熔滴,繼(ji)續向前施焊(han)10mm左右(you),把(ba)定位焊(han)縫表面(mian)熔化,最后用(yong)電流衰(shuai)減法收弧(hu)。收弧(hu)焊(han)縫應在定位焊(han)縫后方10mm左右(you)處,以保證接頭(tou)部(bu)位能(neng)焊(han)透。


②. 平角(jiao)焊


  操作時(shi),焊(han)(han)槍(qiang)(qiang)、焊(han)(han)絲和焊(han)(han)件(jian)之間的相(xiang)對位置如(ru)圖4-12所(suo)示。電弧長度1.5mm左右(you),焊(han)(han)槍(qiang)(qiang)與焊(han)(han)件(jian)的傾(qing)角為40°~50°,焊(han)(han)絲送入(ru)傾(qing)角為15°~20°。