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機構可(ke)分(fen)為等速送絲和均勻(yun)調節送絲兩(liang)大類。
1. 等速送絲（又稱電弧(hu)自(zi)身調節(jie)送絲）
等速(su)(su)送絲適(shi)用于細焊(han)(han)(han)絲或高電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)密度的(de)(de)焊(han)(han)(han)接(jie)(jie)場合，配合管狀導(dao)電(dian)(dian)(dian)(dian)(dian)(dian)嘴（或稱管狀偏心導(dao)電(dian)(dian)(dian)(dian)(dian)(dian)嘴、偏心導(dao)電(dian)(dian)(dian)(dian)(dian)(dian)嘴）。焊(han)(han)(han)絲的(de)(de)送進(jin)按(an)(an)預選定(ding)(ding)的(de)(de)速(su)(su)度等速(su)(su)進(jin)入焊(han)(han)(han)接(jie)(jie)區(qu)，其工作原理(li)是(shi)采用機械方法（更換變(bian)(bian)速(su)(su)齒輪）來調(diao)速(su)(su)。依靠(kao)電(dian)(dian)(dian)(dian)(dian)(dian)弧(hu)(hu)(hu)的(de)(de)自身調(diao)節作用來維持弧(hu)(hu)(hu)長(chang)相對穩定(ding)(ding)。當焊(han)(han)(han)接(jie)(jie)電(dian)(dian)(dian)(dian)(dian)(dian)弧(hu)(hu)(hu)受到(dao)外界干擾而弧(hu)(hu)(hu)長(chang)增加時(shi)，下降外特性電(dian)(dian)(dian)(dian)(dian)(dian)源供給(gei)的(de)(de)焊(han)(han)(han)接(jie)(jie)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)減小，焊(han)(han)(han)絲熔(rong)化(hua)速(su)(su)度減緩，電(dian)(dian)(dian)(dian)(dian)(dian)弧(hu)(hu)(hu)便(bian)會由(you)長(chang)變(bian)(bian)短，趨(qu)向(xiang)給(gei)定(ding)(ding)值。反之(zhi)，電(dian)(dian)(dian)(dian)(dian)(dian)弧(hu)(hu)(hu)變(bian)(bian)短時(shi)，焊(han)(han)(han)接(jie)(jie)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)增大(da)，焊(han)(han)(han)絲熔(rong)化(hua)加快，弧(hu)(hu)(hu)長(chang)又由(you)短變(bian)(bian)長(chang)，趨(qu)向(xiang)給(gei)定(ding)(ding)值。按(an)(an)這(zhe)個工作原理(li)制造的(de)(de)等速(su)(su)送絲埋弧(hu)(hu)(hu)焊(han)(han)(han)設(she)備有MZ1-1000、MZ2-1500和MZ3-500等型(xing)號(hao)，其焊(han)(han)(han)接(jie)(jie)電(dian)(dian)(dian)(dian)(dian)(dian)源可采用交流(liu)、直流(liu)弧(hu)(hu)(hu)焊(han)(han)(han)電(dian)(dian)(dian)(dian)(dian)(dian)源。
2. 均勻調節送(song)絲（又稱強迫調節送(song)絲、變速送(song)絲）
均勻調節送絲適用于粗焊絲或(huo)低(di)電(dian)流(liu)密度的焊接(jie)場合(he)，配合(he)滾輪式或(huo)夾(jia)瓦(wa)式導電(dian)嘴。
焊(han)絲的(de)送(song)進(jin)速(su)(su)度按電(dian)(dian)(dian)弧(hu)(hu)(hu)電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)的(de)高低自動(dong)均勻(yun)調(diao)(diao)節(jie)，電(dian)(dian)(dian)弧(hu)(hu)(hu)電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)調(diao)(diao)節(jie)原理是(shi)利用(yong)(yong)電(dian)(dian)(dian)弧(hu)(hu)(hu)電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)作為反饋信號，經過控(kong)制調(diao)(diao)節(jie)系統改變送(song)絲速(su)(su)度而保持弧(hu)(hu)(hu)長(chang)(chang)相對(dui)不變。當(dang)電(dian)(dian)(dian)弧(hu)(hu)(hu)受外界干擾(rao)變長(chang)(chang)，電(dian)(dian)(dian)弧(hu)(hu)(hu)電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)升高時(shi)，控(kong)制調(diao)(diao)節(jie)系統接到(dao)電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)反饋信號后送(song)絲速(su)(su)度調(diao)(diao)快，弧(hu)(hu)(hu)長(chang)(chang)由(you)長(chang)(chang)變短，趨(qu)向穩定(ding)值。當(dang)電(dian)(dian)(dian)弧(hu)(hu)(hu)長(chang)(chang)度變短，電(dian)(dian)(dian)弧(hu)(hu)(hu)電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)下降時(shi)，將送(song)絲速(su)(su)度調(diao)(diao)慢(man)，弧(hu)(hu)(hu)長(chang)(chang)增長(chang)(chang)趨(qu)向給定(ding)值。這種埋(mai)弧(hu)(hu)(hu)焊(han)機(ji)的(de)控(kong)制系統稍復(fu)雜，具(ju)體型(xing)號有MZ-1000、MZ-1-1000和(he)MU1-1000等。其焊(han)接電(dian)(dian)(dian)源可(ke)采(cai)用(yong)(yong)交(jiao)流(liu)、直流(liu)弧(hu)(hu)(hu)焊(han)電(dian)(dian)(dian)源。
按工作需要，埋弧焊機(ji)常見的構造(zao)形(xing)式(shi)(shi)有：焊車(che)式(shi)(shi)、懸掛式(shi)(shi)、機(ji)床式(shi)(shi)、門架式(shi)(shi)和懸臂式(shi)(shi)等(deng)，如圖(tu)4-12所示。
