普通低(di)合(he)(he)金(jin)(jin)鋼(gang)雖溫(wen)(wen)度(du)降低(di)強度(du)有(you)所增加，塑韌性卻急劇降低(di)，這類鋼(gang)不能用(yong)(yong)(yong)(yong)于低(di)溫(wen)(wen)下(xia)工(gong)作的(de)(de)結構(gou)(gou)上(shang)，而(er)低(di)溫(wen)(wen)用(yong)(yong)(yong)(yong)鋼(gang)在(zai)(zai)相(xiang)應的(de)(de)低(di)溫(wen)(wen)條件(jian)下(xia)仍(reng)具有(you)良好的(de)(de)韌性和(he)抗脆斷(duan)能力(li)，能夠確保結構(gou)(gou)的(de)(de)使用(yong)(yong)(yong)(yong)安全。低(di)溫(wen)(wen)鋼(gang)主要用(yong)(yong)(yong)(yong)于低(di)溫(wen)(wen)下(xia)工(gong)作的(de)(de)容(rong)(rong)器、管道(dao)和(he)結構(gou)(gou)，如石油化(hua)(hua)工(gong)設(she)備(bei)（化(hua)(hua)肥、乙烯、煤液化(hua)(hua)、液化(hua)(hua)石油氣(qi)等）、冷凍設(she)備(bei)、食品工(gong)業及(ji)液態氣(qi)體(ti)儲存設(she)備(bei)等。低(di)合(he)(he)金(jin)(jin)低(di)溫(wen)(wen)用(yong)(yong)(yong)(yong)鋼(gang)一般用(yong)(yong)(yong)(yong)于-110~-20℃工(gong)況條件(jian)。按適用(yong)(yong)(yong)(yong)溫(wen)(wen)度(du)范圍，低(di)合(he)(he)金(jin)(jin)低(di)溫(wen)(wen)用(yong)(yong)(yong)(yong)鋼(gang)可(ke)(ke)分(fen)為-40℃、-70℃、-90℃、-110℃鋼(gang)；按照鋼(gang)材的(de)(de)合(he)(he)金(jin)(jin)體(ti)系，低(di)合(he)(he)金(jin)(jin)低(di)溫(wen)(wen)用(yong)(yong)(yong)(yong)鋼(gang)可(ke)(ke)分(fen)為不含(han)鎳(nie)(nie)及(ji)含(han)鎳(nie)(nie)的(de)(de)兩大類。不含(han)鎳(nie)(nie)的(de)(de)低(di)溫(wen)(wen)用(yong)(yong)(yong)(yong)鋼(gang)一般工(gong)作溫(wen)(wen)度(du)在(zai)(zai)-40℃以上(shang)，而(er)含(han)鎳(nie)(nie)的(de)(de)低(di)溫(wen)(wen)鋼(gang)根據鎳(nie)(nie)含(han)量的(de)(de)高低(di)，可(ke)(ke)以工(gong)作在(zai)(zai)較低(di)的(de)(de)溫(wen)(wen)度(du)下(xia)，如2.5%Ni鋼(gang)可(ke)(ke)以用(yong)(yong)(yong)(yong)于-60℃以下(xia)，3.5%Ni鋼(gang)可(ke)(ke)以用(yong)(yong)(yong)(yong)于-110~-90℃。表1-10和(he)表1-11列出了(le)我(wo)國(guo)常用(yong)(yong)(yong)(yong)低(di)合(he)(he)金(jin)(jin)低(di)溫(wen)(wen)壓力(li)容(rong)(rong)器用(yong)(yong)(yong)(yong)鋼(gang)的(de)(de)化(hua)(hua)學(xue)成(cheng)分(fen)及(ji)力(li)學(xue)性能。

  低(di)(di)合金(jin)低(di)(di)溫(wen)(wen)用鋼(gang)一般是(shi)通過合金(jin)元(yuan)素的固溶強化(hua)、晶(jing)粒細化(hua)，并(bing)通過正(zheng)火(huo)(huo)或(huo)正(zheng)火(huo)(huo)＋回火(huo)(huo)處理細化(hua)組織晶(jing)粒，從而獲(huo)得良好的低(di)(di)溫(wen)(wen)韌性。在低(di)(di)溫(wen)(wen)用鋼(gang)中(zhong)(zhong)常用合金(jin)元(yuan)素是(shi)Mn、Ni、V、Nb等，如(ru)我國(guo)低(di)(di)溫(wen)(wen)壓力容器用鋼(gang)09Mn2VDR、15MnNiDR及(ji)(ji)09MnNiDR等，為保證低(di)(di)溫(wen)(wen)韌性，在低(di)(di)溫(wen)(wen)用鋼(gang)中(zhong)(zhong)盡量(liang)(liang)降低(di)(di)碳含量(liang)(liang)，并(bing)嚴格控制硫、磷含量(liang)(liang)。低(di)(di)合金(jin)低(di)(di)溫(wen)(wen)用鋼(gang)還有(you)相應的鑄件、鍛件及(ji)(ji)管材，JB4727-2000中(zhong)(zhong)對5種常用的低(di)(di)合金(jin)低(di)(di)溫(wen)(wen)鋼(gang)鍛件的化(hua)學成分、力學性能(neng)做(zuo)出了規(gui)定，見(jian)表(biao)1-12及(ji)(ji)表(biao)1-13所示。