3.5%鎳鋼(gang)通過降低碳、硫、磷含量，加(jia)(jia)入鎳等合金成分(fen)，并(bing)通過熱(re)(re)處(chu)(chu)(chu)理細化(hua)晶(jing)粒，使(shi)其(qi)具有(you)(you)優良的(de)低溫(wen)(wen)(wen)(wen)(wen)性(xing)(xing)(xing)能，被廣泛應(ying)用(yong)(yong)于(yu)(yu)乙烯、化(hua)肥、液化(hua)石油氣(qi)及煤氣(qi)工(gong)程(cheng)中低溫(wen)(wen)(wen)(wen)(wen)設備的(de)制(zhi)(zhi)(zhi)造。3.5%鎳鋼(gang)一般(ban)為(wei)正火(huo)(huo)或正火(huo)(huo)＋回(hui)火(huo)(huo)狀態使(shi)用(yong)(yong)，其(qi)低溫(wen)(wen)(wen)(wen)(wen)韌性(xing)(xing)(xing)較(jiao)穩定，顯(xian)微組織為(wei)鐵(tie)素(su)體和珠光體，使(shi)用(yong)(yong)溫(wen)(wen)(wen)(wen)(wen)度(du)達-101℃.經調質處(chu)(chu)(chu)理，其(qi)組織和低溫(wen)(wen)(wen)(wen)(wen)韌性(xing)(xing)(xing)得到進(jin)一步改善，最(zui)低使(shi)用(yong)(yong)溫(wen)(wen)(wen)(wen)(wen)度(du)為(wei)-110℃.為(wei)避(bi)免由(you)(you)于(yu)(yu)過熱(re)(re)而使(shi)焊(han)(han)(han)縫及熱(re)(re)影響(xiang)區的(de)韌性(xing)(xing)(xing)惡化(hua)，焊(han)(han)(han)接(jie)(jie)時焊(han)(han)(han)條(tiao)盡(jin)量不(bu)擺動，采(cai)陽焊(han)(han)(han)道(dao)、多道(dao)多層焊(han)(han)(han)，并(bing)嚴(yan)格(ge)控(kong)(kong)制(zhi)(zhi)(zhi)焊(han)(han)(han)接(jie)(jie)預(yu)熱(re)(re)溫(wen)(wen)(wen)(wen)(wen)度(du)及焊(han)(han)(han)道(dao)間溫(wen)(wen)(wen)(wen)(wen)度(du)，一般(ban)控(kong)(kong)制(zhi)(zhi)(zhi)在(zai)(zai)(zai)50~100℃范(fan)圍(wei)內，同時應(ying)采(cai)用(yong)(yong)小的(de)熱(re)(re)輸入施焊(han)(han)(han)，焊(han)(han)(han)條(tiao)電弧焊(han)(han)(han)的(de)熱(re)(re)輸人(ren)應(ying)控(kong)(kong)制(zhi)(zhi)(zhi)在(zai)(zai)(zai)2.0kJ/mm以(yi)(yi)下(xia)，熔化(hua)極(ji)氣(qi)體保護焊(han)(han)(han)的(de)熱(re)(re)輸入應(ying)控(kong)(kong)制(zhi)(zhi)(zhi)在(zai)(zai)(zai)2.5kJ/mm以(yi)(yi)下(xia)。由(you)(you)于(yu)(yu)3.5%鎳鋼(gang)中的(de)含碳量較(jiao)低，所以(yi)(yi)其(qi)淬硬傾向(xiang)不(bu)大(da)，一般(ban)可(ke)以(yi)(yi)不(bu)預(yu)熱(re)(re)，但板厚在(zai)(zai)(zai)25mm以(yi)(yi)上，焊(han)(han)(han)件剛性(xing)(xing)(xing)較(jiao)大(da)時，焊(han)(han)(han)前(qian)要預(yu)熱(re)(re)到150℃左右，道(dao)間溫(wen)(wen)(wen)(wen)(wen)度(du)與預(yu)熱(re)(re)溫(wen)(wen)(wen)(wen)(wen)度(du)相同，鋼(gang)有(you)(you)應(ying)變時效傾向(xiang)，當冷加(jia)(jia)工(gong)變形量在(zai)(zai)(zai)5%以(yi)(yi)上時，要進(jin)行消除(chu)應(ying)力熱(re)(re)處(chu)(chu)(chu)理改善韌性(xing)(xing)(xing)。該類鋼(gang)在(zai)(zai)(zai)焊(han)(han)(han)后消除(chu)應(ying)力退火(huo)(huo)處(chu)(chu)(chu)理過程(cheng)中，易(yi)產生回(hui)火(huo)(huo)脆性(xing)(xing)(xing)。為(wei)避(bi)免回(hui)火(huo)(huo)脆性(xing)(xing)(xing)，建(jian)(jian)議采(cai)用(yong)(yong)4.5%Ni-0.2%Mo系焊(han)(han)(han)絲，用(yong)(yong)NB-3N焊(han)(han)(han)條(tiao)焊(han)(han)(han)接(jie)(jie)時，建(jian)(jian)議采(cai)用(yong)(yong)表(biao)5-58規定的(de)焊(han)(han)(han)接(jie)(jie)電流，焊(han)(han)(han)后進(jin)行600~625℃熱(re)(re)處(chu)(chu)(chu)理，有(you)(you)利于(yu)(yu)收善焊(han)(han)(han)接(jie)(jie)接(jie)(jie)頭(tou)的(de)低溫(wen)(wen)(wen)(wen)(wen)韌性(xing)(xing)(xing)。