3.5%鎳鋼通過(guo)降低(di)碳(tan)、硫(liu)、磷含(han)量，加入鎳等合(he)金成分，并通過(guo)熱(re)(re)處理細化晶粒，使(shi)(shi)(shi)其(qi)(qi)具(ju)有優良的(de)(de)(de)低(di)溫(wen)(wen)(wen)(wen)(wen)性(xing)能，被廣泛應用(yong)于(yu)(yu)乙烯(xi)、化肥、液化石油氣(qi)及(ji)(ji)煤氣(qi)工(gong)程(cheng)中低(di)溫(wen)(wen)(wen)(wen)(wen)設(she)備的(de)(de)(de)制造。3.5%鎳鋼一般(ban)(ban)為正火(huo)或正火(huo)＋回火(huo)狀態使(shi)(shi)(shi)用(yong)，其(qi)(qi)低(di)溫(wen)(wen)(wen)(wen)(wen)韌(ren)(ren)(ren)性(xing)較穩(wen)定，顯微(wei)組織為鐵素體和(he)珠(zhu)光體，使(shi)(shi)(shi)用(yong)溫(wen)(wen)(wen)(wen)(wen)度(du)達-101℃.經調質處理，其(qi)(qi)組織和(he)低(di)溫(wen)(wen)(wen)(wen)(wen)韌(ren)(ren)(ren)性(xing)得到進一步改善(shan)，最(zui)低(di)使(shi)(shi)(shi)用(yong)溫(wen)(wen)(wen)(wen)(wen)度(du)為-110℃.為避免由于(yu)(yu)過(guo)熱(re)(re)而使(shi)(shi)(shi)焊(han)(han)(han)(han)縫(feng)及(ji)(ji)熱(re)(re)影響區的(de)(de)(de)韌(ren)(ren)(ren)性(xing)惡化，焊(han)(han)(han)(han)接時焊(han)(han)(han)(han)條(tiao)(tiao)(tiao)盡量不擺動(dong)，采(cai)陽焊(han)(han)(han)(han)道、多道多層焊(han)(han)(han)(han)，并嚴格控(kong)制焊(han)(han)(han)(han)接預(yu)熱(re)(re)溫(wen)(wen)(wen)(wen)(wen)度(du)及(ji)(ji)焊(han)(han)(han)(han)道間(jian)(jian)溫(wen)(wen)(wen)(wen)(wen)度(du)，一般(ban)(ban)控(kong)制在(zai)50~100℃范(fan)圍內，同時應采(cai)用(yong)小的(de)(de)(de)熱(re)(re)輸入施焊(han)(han)(han)(han)，焊(han)(han)(han)(han)條(tiao)(tiao)(tiao)電弧(hu)焊(han)(han)(han)(han)的(de)(de)(de)熱(re)(re)輸人(ren)應控(kong)制在(zai)2.0kJ/mm以(yi)(yi)下，熔化極氣(qi)體保(bao)護焊(han)(han)(han)(han)的(de)(de)(de)熱(re)(re)輸入應控(kong)制在(zai)2.5kJ/mm以(yi)(yi)下。由于(yu)(yu)3.5%鎳鋼中的(de)(de)(de)含(han)碳(tan)量較低(di)，所以(yi)(yi)其(qi)(qi)淬硬傾(qing)向不大(da)，一般(ban)(ban)可以(yi)(yi)不預(yu)熱(re)(re)，但板(ban)厚在(zai)25mm以(yi)(yi)上(shang)，焊(han)(han)(han)(han)件剛性(xing)較大(da)時，焊(han)(han)(han)(han)前(qian)要(yao)預(yu)熱(re)(re)到150℃左右，道間(jian)(jian)溫(wen)(wen)(wen)(wen)(wen)度(du)與預(yu)熱(re)(re)溫(wen)(wen)(wen)(wen)(wen)度(du)相(xiang)同，鋼有應變(bian)時效傾(qing)向，當冷加工(gong)變(bian)形量在(zai)5%以(yi)(yi)上(shang)時，要(yao)進行消除應力熱(re)(re)處理改善(shan)韌(ren)(ren)(ren)性(xing)。該類鋼在(zai)焊(han)(han)(han)(han)后(hou)消除應力退火(huo)處理過(guo)程(cheng)中，易(yi)產生回火(huo)脆性(xing)。為避免回火(huo)脆性(xing)，建議(yi)采(cai)用(yong)4.5%Ni-0.2%Mo系焊(han)(han)(han)(han)絲，用(yong)NB-3N焊(han)(han)(han)(han)條(tiao)(tiao)(tiao)焊(han)(han)(han)(han)接時，建議(yi)采(cai)用(yong)表5-58規(gui)定的(de)(de)(de)焊(han)(han)(han)(han)接電流，焊(han)(han)(han)(han)后(hou)進行600~625℃熱(re)(re)處理，有利于(yu)(yu)收善(shan)焊(han)(han)(han)(han)接接頭的(de)(de)(de)低(di)溫(wen)(wen)(wen)(wen)(wen)韌(ren)(ren)(ren)性(xing)。