電弧在焊劑層下燃燒進行焊接的方法稱為埋弧(hu)焊(han)（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。
不銹鋼管(guan)埋弧焊(han)設(she)備按送(song)絲(si)機構可分為等(deng)速送(song)絲(si)和均(jun)勻調節(jie)送(song)絲(si)兩大類。
1. 等速送(song)絲（又稱電弧(hu)自身(shen)調節送(song)絲）
等速(su)(su)(su)送(song)絲(si)適(shi)用于細焊(han)(han)(han)(han)絲(si)或高電(dian)(dian)(dian)流密度的焊(han)(han)(han)(han)接(jie)場合，配合管狀導(dao)(dao)電(dian)(dian)(dian)嘴（或稱(cheng)管狀偏心導(dao)(dao)電(dian)(dian)(dian)嘴、偏心導(dao)(dao)電(dian)(dian)(dian)嘴）。焊(han)(han)(han)(han)絲(si)的送(song)進(jin)按(an)預選(xuan)定(ding)的速(su)(su)(su)度等速(su)(su)(su)進(jin)入(ru)焊(han)(han)(han)(han)接(jie)區，其工作原(yuan)(yuan)理(li)是采(cai)用機械方法(fa)（更換(huan)變(bian)(bian)速(su)(su)(su)齒輪）來調速(su)(su)(su)。依靠(kao)電(dian)(dian)(dian)弧(hu)(hu)(hu)(hu)的自身(shen)調節作用來維持(chi)弧(hu)(hu)(hu)(hu)長(chang)相對穩定(ding)。當焊(han)(han)(han)(han)接(jie)電(dian)(dian)(dian)弧(hu)(hu)(hu)(hu)受到外界干擾(rao)而弧(hu)(hu)(hu)(hu)長(chang)增(zeng)加(jia)時(shi)，下降外特(te)性電(dian)(dian)(dian)源供給的焊(han)(han)(han)(han)接(jie)電(dian)(dian)(dian)流減(jian)小，焊(han)(han)(han)(han)絲(si)熔(rong)(rong)化速(su)(su)(su)度減(jian)緩，電(dian)(dian)(dian)弧(hu)(hu)(hu)(hu)便會由長(chang)變(bian)(bian)短(duan)(duan)，趨向(xiang)給定(ding)值。反之(zhi)，電(dian)(dian)(dian)弧(hu)(hu)(hu)(hu)變(bian)(bian)短(duan)(duan)時(shi)，焊(han)(han)(han)(han)接(jie)電(dian)(dian)(dian)流增(zeng)大，焊(han)(han)(han)(han)絲(si)熔(rong)(rong)化加(jia)快，弧(hu)(hu)(hu)(hu)長(chang)又由短(duan)(duan)變(bian)(bian)長(chang)，趨向(xiang)給定(ding)值。按(an)這個工作原(yuan)(yuan)理(li)制造的等速(su)(su)(su)送(song)絲(si)埋弧(hu)(hu)(hu)(hu)焊(han)(han)(han)(han)設備(bei)有MZ1-1000、MZ2-1500和(he)MZ3-500等型號，其焊(han)(han)(han)(han)接(jie)電(dian)(dian)(dian)源可采(cai)用交流、直(zhi)流弧(hu)(hu)(hu)(hu)焊(han)(han)(han)(han)電(dian)(dian)(dian)源。
2. 均勻調(diao)(diao)節(jie)送絲(si)(si)（又稱強迫調(diao)(diao)節(jie)送絲(si)(si)、變速送絲(si)(si)）
均勻(yun)調節送絲適用(yong)于粗焊絲或低電(dian)流密(mi)度(du)的(de)焊接(jie)場合，配合滾輪式或夾瓦式導電(dian)嘴。
焊(han)絲的(de)送(song)(song)進速度(du)按電(dian)弧(hu)(hu)(hu)電(dian)壓的(de)高低自動均勻調(diao)節(jie)(jie)(jie)，電(dian)弧(hu)(hu)(hu)電(dian)壓調(diao)節(jie)(jie)(jie)原理是利用電(dian)弧(hu)(hu)(hu)電(dian)壓作為(wei)反(fan)饋(kui)信號，經過控(kong)制(zhi)(zhi)調(diao)節(jie)(jie)(jie)系統(tong)改變送(song)(song)絲速度(du)而保持(chi)弧(hu)(hu)(hu)長(chang)相對(dui)不變。當電(dian)弧(hu)(hu)(hu)受外界干擾變長(chang)，電(dian)弧(hu)(hu)(hu)電(dian)壓升高時(shi)(shi)，控(kong)制(zhi)(zhi)調(diao)節(jie)(jie)(jie)系統(tong)接(jie)到(dao)電(dian)壓反(fan)饋(kui)信號后送(song)(song)絲速度(du)調(diao)快(kuai)，弧(hu)(hu)(hu)長(chang)由長(chang)變短(duan)，趨(qu)(qu)向(xiang)穩定(ding)值。當電(dian)弧(hu)(hu)(hu)長(chang)度(du)變短(duan)，電(dian)弧(hu)(hu)(hu)電(dian)壓下(xia)降時(shi)(shi)，將送(song)(song)絲速度(du)調(diao)慢(man)，弧(hu)(hu)(hu)長(chang)增長(chang)趨(qu)(qu)向(xiang)給定(ding)值。這(zhe)種埋弧(hu)(hu)(hu)焊(han)機的(de)控(kong)制(zhi)(zhi)系統(tong)稍復雜，具(ju)體型號有MZ-1000、MZ-1-1000和(he)MU1-1000等。其焊(han)接(jie)電(dian)源可采用交流、直流弧(hu)(hu)(hu)焊(han)電(dian)源。
按工作(zuo)需要，埋弧焊(han)機(ji)常見的構造形(xing)式(shi)有：焊(han)車式(shi)、懸掛式(shi)、機(ji)床式(shi)、門(men)架式(shi)和懸臂式(shi)等，如圖(tu)4-12所示。
