3.5%鎳(nie)鋼(gang)通過(guo)(guo)降低(di)(di)(di)碳、硫、磷含(han)量(liang),加(jia)入(ru)(ru)鎳(nie)等合金(jin)成分,并(bing)通過(guo)(guo)熱(re)處理(li)(li)細化(hua)(hua)晶粒,使(shi)其(qi)具有(you)優(you)良的(de)(de)(de)低(di)(di)(di)溫(wen)(wen)(wen)性(xing)(xing)能,被廣泛應(ying)(ying)(ying)(ying)用(yong)(yong)于乙烯、化(hua)(hua)肥、液化(hua)(hua)石油氣(qi)及(ji)(ji)煤氣(qi)工(gong)程(cheng)中(zhong)低(di)(di)(di)溫(wen)(wen)(wen)設備的(de)(de)(de)制(zhi)造(zao)。3.5%鎳(nie)鋼(gang)一(yi)般為(wei)正火(huo)或正火(huo)+回火(huo)狀態使(shi)用(yong)(yong),其(qi)低(di)(di)(di)溫(wen)(wen)(wen)韌(ren)性(xing)(xing)較穩(wen)定(ding),顯微(wei)組織為(wei)鐵素體和珠光體,使(shi)用(yong)(yong)溫(wen)(wen)(wen)度(du)達(da)-101℃.經(jing)調質處理(li)(li),其(qi)組織和低(di)(di)(di)溫(wen)(wen)(wen)韌(ren)性(xing)(xing)得到(dao)進一(yi)步改善,最低(di)(di)(di)使(shi)用(yong)(yong)溫(wen)(wen)(wen)度(du)為(wei)-110℃.為(wei)避免(mian)由(you)(you)于過(guo)(guo)熱(re)而使(shi)焊(han)(han)(han)縫(feng)及(ji)(ji)熱(re)影響區(qu)的(de)(de)(de)韌(ren)性(xing)(xing)惡化(hua)(hua),焊(han)(han)(han)接時(shi)焊(han)(han)(han)條盡量(liang)不擺動,采(cai)陽焊(han)(han)(han)道(dao)、多道(dao)多層(ceng)焊(han)(han)(han),并(bing)嚴(yan)格(ge)控(kong)制(zhi)焊(han)(han)(han)接預熱(re)溫(wen)(wen)(wen)度(du)及(ji)(ji)焊(han)(han)(han)道(dao)間(jian)溫(wen)(wen)(wen)度(du),一(yi)般控(kong)制(zhi)在(zai)50~100℃范(fan)圍內,同時(shi)應(ying)(ying)(ying)(ying)采(cai)用(yong)(yong)小(xiao)的(de)(de)(de)熱(re)輸(shu)入(ru)(ru)施焊(han)(han)(han),焊(han)(han)(han)條電(dian)弧(hu)焊(han)(han)(han)的(de)(de)(de)熱(re)輸(shu)人應(ying)(ying)(ying)(ying)控(kong)制(zhi)在(zai)2.0kJ/mm以下(xia),熔(rong)化(hua)(hua)極氣(qi)體保護(hu)焊(han)(han)(han)的(de)(de)(de)熱(re)輸(shu)入(ru)(ru)應(ying)(ying)(ying)(ying)控(kong)制(zhi)在(zai)2.5kJ/mm以下(xia)。由(you)(you)于3.5%鎳(nie)鋼(gang)中(zhong)的(de)(de)(de)含(han)碳量(liang)較低(di)(di)(di),所以其(qi)淬硬傾向(xiang)不大(da),一(yi)般可以不預熱(re),但板厚在(zai)25mm以上(shang),焊(han)(han)(han)件剛(gang)性(xing)(xing)較大(da)時(shi),焊(han)(han)(han)前要(yao)預熱(re)到(dao)150℃左右(you),道(dao)間(jian)溫(wen)(wen)(wen)度(du)與預熱(re)溫(wen)(wen)(wen)度(du)相同,鋼(gang)有(you)應(ying)(ying)(ying)(ying)變(bian)時(shi)效傾向(xiang),當冷加(jia)工(gong)變(bian)形量(liang)在(zai)5%以上(shang)時(shi),要(yao)進行(xing)消(xiao)除應(ying)(ying)(ying)(ying)力熱(re)處理(li)(li)改善韌(ren)性(xing)(xing)。該類鋼(gang)在(zai)焊(han)(han)(han)后消(xiao)除應(ying)(ying)(ying)(ying)力退火(huo)處理(li)(li)過(guo)(guo)程(cheng)中(zhong),易產(chan)生回火(huo)脆(cui)(cui)性(xing)(xing)。為(wei)避免(mian)回火(huo)脆(cui)(cui)性(xing)(xing),建議采(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)條焊(han)(han)(han)接時(shi),建議采(cai)用(yong)(yong)表5-58規(gui)定(ding)的(de)(de)(de)焊(han)(han)(han)接電(dian)流,焊(han)(han)(han)后進行(xing)600~625℃熱(re)處理(li)(li),有(you)利于收善焊(han)(han)(han)接接頭(tou)的(de)(de)(de)低(di)(di)(di)溫(wen)(wen)(wen)韌(ren)性(xing)(xing)。