電弧在焊劑層下燃燒進行焊接的方法稱為埋弧(hu)焊（submerged arc welding，SAW）。焊接電弧在焊絲與焊件之間燃燒，焊絲沿著待焊軌跡均勻不斷地送往電弧區，電弧熱將焊絲端部及電弧附近的母材金屬和焊劑熔化，電弧移開后熔池金屬凝固成焊縫，熔化的焊劑（未滲入焊縫金屬中的那部分）則凝固成渣殼覆蓋于焊縫表面。埋弧焊分機械操作（自動）和手工操作（半自動）兩種方法。
不銹鋼(gang)管埋弧焊設備按送絲(si)機構(gou)可分為等(deng)速送絲(si)和均勻調(diao)節送絲(si)兩(liang)大類(lei)。
1. 等速送絲(si)（又稱電弧自身調(diao)節送絲(si)）
等(deng)速(su)(su)(su)送(song)(song)絲(si)(si)適用(yong)(yong)于細焊(han)(han)(han)(han)(han)(han)絲(si)(si)或高電(dian)(dian)(dian)(dian)流密度的(de)焊(han)(han)(han)(han)(han)(han)接(jie)場合，配合管狀(zhuang)導電(dian)(dian)(dian)(dian)嘴（或稱管狀(zhuang)偏(pian)心導電(dian)(dian)(dian)(dian)嘴、偏(pian)心導電(dian)(dian)(dian)(dian)嘴）。焊(han)(han)(han)(han)(han)(han)絲(si)(si)的(de)送(song)(song)進按預選定的(de)速(su)(su)(su)度等(deng)速(su)(su)(su)進入焊(han)(han)(han)(han)(han)(han)接(jie)區，其(qi)工(gong)作原(yuan)理是采用(yong)(yong)機械(xie)方法（更換變速(su)(su)(su)齒輪(lun)）來(lai)(lai)調速(su)(su)(su)。依(yi)靠電(dian)(dian)(dian)(dian)弧(hu)(hu)(hu)(hu)的(de)自身調節作用(yong)(yong)來(lai)(lai)維持(chi)弧(hu)(hu)(hu)(hu)長(chang)(chang)相對穩定。當焊(han)(han)(han)(han)(han)(han)接(jie)電(dian)(dian)(dian)(dian)弧(hu)(hu)(hu)(hu)受(shou)到外(wai)界(jie)干擾而弧(hu)(hu)(hu)(hu)長(chang)(chang)增(zeng)加(jia)時(shi)，下降外(wai)特性(xing)電(dian)(dian)(dian)(dian)源供(gong)給的(de)焊(han)(han)(han)(han)(han)(han)接(jie)電(dian)(dian)(dian)(dian)流減小，焊(han)(han)(han)(han)(han)(han)絲(si)(si)熔(rong)化速(su)(su)(su)度減緩，電(dian)(dian)(dian)(dian)弧(hu)(hu)(hu)(hu)便會由長(chang)(chang)變短，趨向(xiang)給定值。反(fan)之(zhi)，電(dian)(dian)(dian)(dian)弧(hu)(hu)(hu)(hu)變短時(shi)，焊(han)(han)(han)(han)(han)(han)接(jie)電(dian)(dian)(dian)(dian)流增(zeng)大，焊(han)(han)(han)(han)(han)(han)絲(si)(si)熔(rong)化加(jia)快(kuai)，弧(hu)(hu)(hu)(hu)長(chang)(chang)又由短變長(chang)(chang)，趨向(xiang)給定值。按這個工(gong)作原(yuan)理制(zhi)造(zao)的(de)等(deng)速(su)(su)(su)送(song)(song)絲(si)(si)埋弧(hu)(hu)(hu)(hu)焊(han)(han)(han)(han)(han)(han)設備有MZ1-1000、MZ2-1500和MZ3-500等(deng)型號，其(qi)焊(han)(han)(han)(han)(han)(han)接(jie)電(dian)(dian)(dian)(dian)源可采用(yong)(yong)交流、直流弧(hu)(hu)(hu)(hu)焊(han)(han)(han)(han)(han)(han)電(dian)(dian)(dian)(dian)源。
2. 均勻調節送(song)絲(si)(si)(si)（又(you)稱強(qiang)迫(po)調節送(song)絲(si)(si)(si)、變速送(song)絲(si)(si)(si)）
均勻(yun)調節送絲適用于粗焊(han)絲或(huo)(huo)低電(dian)流密度的焊(han)接場(chang)合，配合滾輪式或(huo)(huo)夾(jia)瓦式導電(dian)嘴。
焊(han)(han)絲(si)(si)的送進速(su)度(du)按電(dian)(dian)(dian)弧(hu)電(dian)(dian)(dian)壓(ya)(ya)的高(gao)低自動均勻調(diao)節(jie)，電(dian)(dian)(dian)弧(hu)電(dian)(dian)(dian)壓(ya)(ya)調(diao)節(jie)原理是利用電(dian)(dian)(dian)弧(hu)電(dian)(dian)(dian)壓(ya)(ya)作(zuo)為反饋信號，經過控(kong)制調(diao)節(jie)系(xi)統改變(bian)(bian)送絲(si)(si)速(su)度(du)而保持弧(hu)長相(xiang)對不變(bian)(bian)。當電(dian)(dian)(dian)弧(hu)受外界(jie)干(gan)擾變(bian)(bian)長，電(dian)(dian)(dian)弧(hu)電(dian)(dian)(dian)壓(ya)(ya)升(sheng)高(gao)時，控(kong)制調(diao)節(jie)系(xi)統接(jie)到電(dian)(dian)(dian)壓(ya)(ya)反饋信號后送絲(si)(si)速(su)度(du)調(diao)快，弧(hu)長由(you)長變(bian)(bian)短(duan)，趨向穩定值。當電(dian)(dian)(dian)弧(hu)長度(du)變(bian)(bian)短(duan)，電(dian)(dian)(dian)弧(hu)電(dian)(dian)(dian)壓(ya)(ya)下(xia)降時，將(jiang)送絲(si)(si)速(su)度(du)調(diao)慢，弧(hu)長增長趨向給定值。這種埋弧(hu)焊(han)(han)機的控(kong)制系(xi)統稍復雜(za)，具(ju)體型號有(you)MZ-1000、MZ-1-1000和MU1-1000等。其(qi)焊(han)(han)接(jie)電(dian)(dian)(dian)源可采(cai)用交流、直流弧(hu)焊(han)(han)電(dian)(dian)(dian)源。
按工作需要，埋弧焊(han)機常見的構造形式有：焊(han)車式、懸(xuan)掛(gua)式、機床式、門(men)架(jia)式和懸(xuan)臂式等，如圖(tu)4-12所示。
