3.5%鎳(nie)鋼(gang)通(tong)過(guo)降低(di)(di)(di)碳、硫、磷含量，加入(ru)鎳(nie)等(deng)合金成分，并通(tong)過(guo)熱(re)(re)(re)處(chu)(chu)(chu)理(li)細化(hua)晶粒，使其具(ju)有優(you)良的低(di)(di)(di)溫(wen)性能(neng)，被廣(guang)泛應(ying)用(yong)(yong)于(yu)乙烯(xi)、化(hua)肥、液化(hua)石油(you)氣及(ji)煤氣工程中(zhong)(zhong)低(di)(di)(di)溫(wen)設(she)備的制(zhi)造。3.5%鎳(nie)鋼(gang)一(yi)般為正火(huo)或正火(huo)＋回(hui)(hui)火(huo)狀(zhuang)態使用(yong)(yong)，其低(di)(di)(di)溫(wen)韌(ren)(ren)性較穩(wen)定，顯微組(zu)(zu)織(zhi)為鐵素體和珠光體，使用(yong)(yong)溫(wen)度達-101℃.經調質處(chu)(chu)(chu)理(li)，其組(zu)(zu)織(zhi)和低(di)(di)(di)溫(wen)韌(ren)(ren)性得(de)到進(jin)一(yi)步(bu)改善(shan)，最低(di)(di)(di)使用(yong)(yong)溫(wen)度為-110℃.為避(bi)(bi)免由(you)(you)于(yu)過(guo)熱(re)(re)(re)而使焊(han)(han)(han)(han)縫及(ji)熱(re)(re)(re)影響區的韌(ren)(ren)性惡化(hua)，焊(han)(han)(han)(han)接(jie)(jie)時(shi)(shi)焊(han)(han)(han)(han)條盡(jin)量不(bu)(bu)擺動(dong)，采(cai)陽焊(han)(han)(han)(han)道、多(duo)道多(duo)層焊(han)(han)(han)(han)，并嚴格控(kong)(kong)制(zhi)焊(han)(han)(han)(han)接(jie)(jie)預(yu)熱(re)(re)(re)溫(wen)度及(ji)焊(han)(han)(han)(han)道間溫(wen)度，一(yi)般控(kong)(kong)制(zhi)在50~100℃范圍內，同時(shi)(shi)應(ying)采(cai)用(yong)(yong)小的熱(re)(re)(re)輸(shu)入(ru)施焊(han)(han)(han)(han)，焊(han)(han)(han)(han)條電弧焊(han)(han)(han)(han)的熱(re)(re)(re)輸(shu)人(ren)應(ying)控(kong)(kong)制(zhi)在2.0kJ/mm以下，熔化(hua)極氣體保護焊(han)(han)(han)(han)的熱(re)(re)(re)輸(shu)入(ru)應(ying)控(kong)(kong)制(zhi)在2.5kJ/mm以下。由(you)(you)于(yu)3.5%鎳(nie)鋼(gang)中(zhong)(zhong)的含碳量較低(di)(di)(di)，所以其淬(cui)硬傾(qing)向不(bu)(bu)大(da)(da)，一(yi)般可以不(bu)(bu)預(yu)熱(re)(re)(re)，但板厚在25mm以上(shang)，焊(han)(han)(han)(han)件剛性較大(da)(da)時(shi)(shi)，焊(han)(han)(han)(han)前要預(yu)熱(re)(re)(re)到150℃左右，道間溫(wen)度與預(yu)熱(re)(re)(re)溫(wen)度相同，鋼(gang)有應(ying)變(bian)時(shi)(shi)效傾(qing)向，當冷加工變(bian)形量在5%以上(shang)時(shi)(shi)，要進(jin)行(xing)消除應(ying)力(li)(li)熱(re)(re)(re)處(chu)(chu)(chu)理(li)改善(shan)韌(ren)(ren)性。該(gai)類鋼(gang)在焊(han)(han)(han)(han)后消除應(ying)力(li)(li)退火(huo)處(chu)(chu)(chu)理(li)過(guo)程中(zhong)(zhong)，易產生回(hui)(hui)火(huo)脆性。為避(bi)(bi)免回(hui)(hui)火(huo)脆性，建議(yi)(yi)采(cai)用(yong)(yong)4.5%Ni-0.2%Mo系焊(han)(han)(han)(han)絲，用(yong)(yong)NB-3N焊(han)(han)(han)(han)條焊(han)(han)(han)(han)接(jie)(jie)時(shi)(shi)，建議(yi)(yi)采(cai)用(yong)(yong)表5-58規定的焊(han)(han)(han)(han)接(jie)(jie)電流(liu)，焊(han)(han)(han)(han)后進(jin)行(xing)600~625℃熱(re)(re)(re)處(chu)(chu)(chu)理(li)，有利于(yu)收善(shan)焊(han)(han)(han)(han)接(jie)(jie)接(jie)(jie)頭(tou)的低(di)(di)(di)溫(wen)韌(ren)(ren)性。