3.5%鎳(nie)鋼(gang)通(tong)過(guo)(guo)(guo)降低(di)(di)碳(tan)、硫、磷含量，加入鎳(nie)等合金成(cheng)分，并通(tong)過(guo)(guo)(guo)熱(re)(re)(re)(re)處理(li)(li)細化晶粒，使(shi)(shi)其(qi)具有(you)優良的(de)(de)低(di)(di)溫(wen)(wen)(wen)性(xing)(xing)能，被(bei)廣(guang)泛應(ying)(ying)用(yong)(yong)(yong)于(yu)乙烯、化肥、液化石油氣(qi)(qi)及(ji)煤(mei)氣(qi)(qi)工程(cheng)中(zhong)(zhong)(zhong)低(di)(di)溫(wen)(wen)(wen)設備的(de)(de)制(zhi)造(zao)。3.5%鎳(nie)鋼(gang)一(yi)般(ban)為(wei)正火或(huo)正火＋回(hui)(hui)(hui)火狀態(tai)使(shi)(shi)用(yong)(yong)(yong)，其(qi)低(di)(di)溫(wen)(wen)(wen)韌(ren)性(xing)(xing)較穩(wen)定(ding)，顯微組(zu)(zu)織為(wei)鐵(tie)素體(ti)和珠光體(ti)，使(shi)(shi)用(yong)(yong)(yong)溫(wen)(wen)(wen)度(du)達(da)-101℃.經(jing)調質處理(li)(li)，其(qi)組(zu)(zu)織和低(di)(di)溫(wen)(wen)(wen)韌(ren)性(xing)(xing)得到進一(yi)步改(gai)善(shan)，最低(di)(di)使(shi)(shi)用(yong)(yong)(yong)溫(wen)(wen)(wen)度(du)為(wei)-110℃.為(wei)避(bi)(bi)免由(you)于(yu)過(guo)(guo)(guo)熱(re)(re)(re)(re)而使(shi)(shi)焊(han)(han)(han)縫及(ji)熱(re)(re)(re)(re)影(ying)響區(qu)的(de)(de)韌(ren)性(xing)(xing)惡化，焊(han)(han)(han)接時(shi)焊(han)(han)(han)條盡量不擺動(dong)，采(cai)陽焊(han)(han)(han)道、多道多層焊(han)(han)(han)，并嚴(yan)格控(kong)(kong)制(zhi)焊(han)(han)(han)接預(yu)熱(re)(re)(re)(re)溫(wen)(wen)(wen)度(du)及(ji)焊(han)(han)(han)道間(jian)溫(wen)(wen)(wen)度(du)，一(yi)般(ban)控(kong)(kong)制(zhi)在(zai)(zai)50~100℃范圍內，同(tong)時(shi)應(ying)(ying)采(cai)用(yong)(yong)(yong)小(xiao)的(de)(de)熱(re)(re)(re)(re)輸(shu)(shu)入施焊(han)(han)(han)，焊(han)(han)(han)條電弧焊(han)(han)(han)的(de)(de)熱(re)(re)(re)(re)輸(shu)(shu)人應(ying)(ying)控(kong)(kong)制(zhi)在(zai)(zai)2.0kJ/mm以(yi)下，熔化極氣(qi)(qi)體(ti)保護焊(han)(han)(han)的(de)(de)熱(re)(re)(re)(re)輸(shu)(shu)入應(ying)(ying)控(kong)(kong)制(zhi)在(zai)(zai)2.5kJ/mm以(yi)下。由(you)于(yu)3.5%鎳(nie)鋼(gang)中(zhong)(zhong)(zhong)的(de)(de)含碳(tan)量較低(di)(di)，所以(yi)其(qi)淬(cui)硬傾(qing)向不大，一(yi)般(ban)可以(yi)不預(yu)熱(re)(re)(re)(re)，但(dan)板厚在(zai)(zai)25mm以(yi)上，焊(han)(han)(han)件剛性(xing)(xing)較大時(shi)，焊(han)(han)(han)前要預(yu)熱(re)(re)(re)(re)到150℃左右，道間(jian)溫(wen)(wen)(wen)度(du)與預(yu)熱(re)(re)(re)(re)溫(wen)(wen)(wen)度(du)相同(tong)，鋼(gang)有(you)應(ying)(ying)變時(shi)效(xiao)傾(qing)向，當冷加工變形量在(zai)(zai)5%以(yi)上時(shi)，要進行消除應(ying)(ying)力熱(re)(re)(re)(re)處理(li)(li)改(gai)善(shan)韌(ren)性(xing)(xing)。該類(lei)鋼(gang)在(zai)(zai)焊(han)(han)(han)后(hou)(hou)消除應(ying)(ying)力退火處理(li)(li)過(guo)(guo)(guo)程(cheng)中(zhong)(zhong)(zhong)，易產生回(hui)(hui)(hui)火脆性(xing)(xing)。為(wei)避(bi)(bi)免回(hui)(hui)(hui)火脆性(xing)(xing)，建(jian)議(yi)(yi)采(cai)用(yong)(yong)(yong)4.5%Ni-0.2%Mo系焊(han)(han)(han)絲，用(yong)(yong)(yong)NB-3N焊(han)(han)(han)條焊(han)(han)(han)接時(shi)，建(jian)議(yi)(yi)采(cai)用(yong)(yong)(yong)表(biao)5-58規(gui)定(ding)的(de)(de)焊(han)(han)(han)接電流，焊(han)(han)(han)后(hou)(hou)進行600~625℃熱(re)(re)(re)(re)處理(li)(li)，有(you)利于(yu)收善(shan)焊(han)(han)(han)接接頭的(de)(de)低(di)(di)溫(wen)(wen)(wen)韌(ren)性(xing)(xing)。