3.5%鎳鋼通(tong)過降低(di)碳、硫、磷含(han)量(liang)，加入鎳等合金(jin)成(cheng)分(fen)，并通(tong)過熱(re)(re)處(chu)理(li)(li)細化(hua)(hua)晶粒，使其(qi)(qi)具有優良的低(di)溫(wen)(wen)(wen)(wen)(wen)性(xing)(xing)(xing)能，被廣泛應用(yong)于(yu)乙(yi)烯、化(hua)(hua)肥、液化(hua)(hua)石油氣(qi)及煤氣(qi)工程(cheng)中(zhong)(zhong)低(di)溫(wen)(wen)(wen)(wen)(wen)設備的制造。3.5%鎳鋼一般為(wei)(wei)正火(huo)或正火(huo)＋回(hui)火(huo)狀態使用(yong)，其(qi)(qi)低(di)溫(wen)(wen)(wen)(wen)(wen)韌(ren)性(xing)(xing)(xing)較(jiao)穩定，顯微組(zu)織(zhi)為(wei)(wei)鐵素體和珠光體，使用(yong)溫(wen)(wen)(wen)(wen)(wen)度(du)(du)達-101℃.經調質(zhi)處(chu)理(li)(li)，其(qi)(qi)組(zu)織(zhi)和低(di)溫(wen)(wen)(wen)(wen)(wen)韌(ren)性(xing)(xing)(xing)得到進(jin)(jin)一步改(gai)善(shan)，最低(di)使用(yong)溫(wen)(wen)(wen)(wen)(wen)度(du)(du)為(wei)(wei)-110℃.為(wei)(wei)避免(mian)由(you)于(yu)過熱(re)(re)而(er)使焊(han)(han)縫及熱(re)(re)影響區的韌(ren)性(xing)(xing)(xing)惡化(hua)(hua)，焊(han)(han)接(jie)(jie)(jie)時(shi)(shi)焊(han)(han)條(tiao)盡量(liang)不(bu)擺動(dong)，采(cai)陽焊(han)(han)道、多道多層焊(han)(han)，并嚴格控(kong)(kong)(kong)制焊(han)(han)接(jie)(jie)(jie)預(yu)熱(re)(re)溫(wen)(wen)(wen)(wen)(wen)度(du)(du)及焊(han)(han)道間溫(wen)(wen)(wen)(wen)(wen)度(du)(du)，一般控(kong)(kong)(kong)制在(zai)(zai)50~100℃范(fan)圍(wei)內，同(tong)時(shi)(shi)應采(cai)用(yong)小的熱(re)(re)輸入施焊(han)(han)，焊(han)(han)條(tiao)電弧焊(han)(han)的熱(re)(re)輸人應控(kong)(kong)(kong)制在(zai)(zai)2.0kJ/mm以(yi)下(xia)，熔化(hua)(hua)極氣(qi)體保護焊(han)(han)的熱(re)(re)輸入應控(kong)(kong)(kong)制在(zai)(zai)2.5kJ/mm以(yi)下(xia)。由(you)于(yu)3.5%鎳鋼中(zhong)(zhong)的含(han)碳量(liang)較(jiao)低(di)，所(suo)以(yi)其(qi)(qi)淬硬傾向(xiang)不(bu)大，一般可以(yi)不(bu)預(yu)熱(re)(re)，但板厚(hou)在(zai)(zai)25mm以(yi)上(shang)，焊(han)(han)件剛性(xing)(xing)(xing)較(jiao)大時(shi)(shi)，焊(han)(han)前要(yao)預(yu)熱(re)(re)到150℃左(zuo)右，道間溫(wen)(wen)(wen)(wen)(wen)度(du)(du)與(yu)預(yu)熱(re)(re)溫(wen)(wen)(wen)(wen)(wen)度(du)(du)相同(tong)，鋼有應變(bian)時(shi)(shi)效傾向(xiang)，當冷加工變(bian)形量(liang)在(zai)(zai)5%以(yi)上(shang)時(shi)(shi)，要(yao)進(jin)(jin)行消除應力熱(re)(re)處(chu)理(li)(li)改(gai)善(shan)韌(ren)性(xing)(xing)(xing)。該類鋼在(zai)(zai)焊(han)(han)后(hou)(hou)消除應力退(tui)火(huo)處(chu)理(li)(li)過程(cheng)中(zhong)(zhong)，易(yi)產(chan)生(sheng)回(hui)火(huo)脆性(xing)(xing)(xing)。為(wei)(wei)避免(mian)回(hui)火(huo)脆性(xing)(xing)(xing)，建議(yi)采(cai)用(yong)4.5%Ni-0.2%Mo系焊(han)(han)絲，用(yong)NB-3N焊(han)(han)條(tiao)焊(han)(han)接(jie)(jie)(jie)時(shi)(shi)，建議(yi)采(cai)用(yong)表5-58規(gui)定的焊(han)(han)接(jie)(jie)(jie)電流，焊(han)(han)后(hou)(hou)進(jin)(jin)行600~625℃熱(re)(re)處(chu)理(li)(li)，有利于(yu)收善(shan)焊(han)(han)接(jie)(jie)(jie)接(jie)(jie)(jie)頭(tou)的低(di)溫(wen)(wen)(wen)(wen)(wen)韌(ren)性(xing)(xing)(xing)。