3.5%鎳鋼(gang)(gang)通(tong)過(guo)降低(di)碳、硫、磷(lin)含量，加入(ru)鎳等合金成分，并(bing)通(tong)過(guo)熱(re)(re)處(chu)(chu)(chu)理細化(hua)晶(jing)粒，使(shi)(shi)其(qi)具有(you)優良的(de)(de)(de)(de)低(di)溫(wen)性(xing)(xing)能，被廣(guang)泛應(ying)用(yong)(yong)(yong)于(yu)乙烯(xi)、化(hua)肥、液化(hua)石油氣及煤氣工(gong)程中(zhong)(zhong)低(di)溫(wen)設備的(de)(de)(de)(de)制造。3.5%鎳鋼(gang)(gang)一般(ban)為(wei)正火或正火＋回(hui)火狀態使(shi)(shi)用(yong)(yong)(yong)，其(qi)低(di)溫(wen)韌性(xing)(xing)較穩定，顯(xian)微組(zu)織為(wei)鐵素體和珠光(guang)體，使(shi)(shi)用(yong)(yong)(yong)溫(wen)度(du)(du)(du)達-101℃.經調(diao)質處(chu)(chu)(chu)理，其(qi)組(zu)織和低(di)溫(wen)韌性(xing)(xing)得(de)到(dao)進(jin)一步(bu)改善(shan)，最(zui)低(di)使(shi)(shi)用(yong)(yong)(yong)溫(wen)度(du)(du)(du)為(wei)-110℃.為(wei)避免由(you)于(yu)過(guo)熱(re)(re)而使(shi)(shi)焊(han)(han)(han)(han)(han)縫(feng)及熱(re)(re)影(ying)響區的(de)(de)(de)(de)韌性(xing)(xing)惡化(hua)，焊(han)(han)(han)(han)(han)接時(shi)(shi)焊(han)(han)(han)(han)(han)條盡量不(bu)擺(bai)動，采陽焊(han)(han)(han)(han)(han)道(dao)、多道(dao)多層焊(han)(han)(han)(han)(han)，并(bing)嚴格控(kong)(kong)制焊(han)(han)(han)(han)(han)接預熱(re)(re)溫(wen)度(du)(du)(du)及焊(han)(han)(han)(han)(han)道(dao)間溫(wen)度(du)(du)(du)，一般(ban)控(kong)(kong)制在(zai)50~100℃范圍內，同時(shi)(shi)應(ying)采用(yong)(yong)(yong)小的(de)(de)(de)(de)熱(re)(re)輸入(ru)施(shi)焊(han)(han)(han)(han)(han)，焊(han)(han)(han)(han)(han)條電弧焊(han)(han)(han)(han)(han)的(de)(de)(de)(de)熱(re)(re)輸人應(ying)控(kong)(kong)制在(zai)2.0kJ/mm以(yi)下，熔化(hua)極氣體保護焊(han)(han)(han)(han)(han)的(de)(de)(de)(de)熱(re)(re)輸入(ru)應(ying)控(kong)(kong)制在(zai)2.5kJ/mm以(yi)下。由(you)于(yu)3.5%鎳鋼(gang)(gang)中(zhong)(zhong)的(de)(de)(de)(de)含碳量較低(di)，所以(yi)其(qi)淬(cui)硬傾向不(bu)大，一般(ban)可以(yi)不(bu)預熱(re)(re)，但板厚在(zai)25mm以(yi)上(shang)，焊(han)(han)(han)(han)(han)件剛性(xing)(xing)較大時(shi)(shi)，焊(han)(han)(han)(han)(han)前(qian)要預熱(re)(re)到(dao)150℃左右，道(dao)間溫(wen)度(du)(du)(du)與預熱(re)(re)溫(wen)度(du)(du)(du)相(xiang)同，鋼(gang)(gang)有(you)應(ying)變時(shi)(shi)效傾向，當冷加工(gong)變形量在(zai)5%以(yi)上(shang)時(shi)(shi)，要進(jin)行消(xiao)(xiao)除應(ying)力熱(re)(re)處(chu)(chu)(chu)理改善(shan)韌性(xing)(xing)。該類(lei)鋼(gang)(gang)在(zai)焊(han)(han)(han)(han)(han)后(hou)消(xiao)(xiao)除應(ying)力退火處(chu)(chu)(chu)理過(guo)程中(zhong)(zhong)，易產生(sheng)回(hui)火脆(cui)性(xing)(xing)。為(wei)避免回(hui)火脆(cui)性(xing)(xing)，建(jian)議采用(yong)(yong)(yong)4.5%Ni-0.2%Mo系(xi)焊(han)(han)(han)(han)(han)絲，用(yong)(yong)(yong)NB-3N焊(han)(han)(han)(han)(han)條焊(han)(han)(han)(han)(han)接時(shi)(shi)，建(jian)議采用(yong)(yong)(yong)表5-58規定的(de)(de)(de)(de)焊(han)(han)(han)(han)(han)接電流，焊(han)(han)(han)(han)(han)后(hou)進(jin)行600~625℃熱(re)(re)處(chu)(chu)(chu)理，有(you)利于(yu)收(shou)善(shan)焊(han)(han)(han)(han)(han)接接頭(tou)的(de)(de)(de)(de)低(di)溫(wen)韌性(xing)(xing)。