普通低(di)(di)(di)(di)合金鋼(gang)(gang)雖溫(wen)(wen)(wen)度(du)降(jiang)低(di)(di)(di)(di)強度(du)有(you)所(suo)增加，塑韌性卻急劇(ju)降(jiang)低(di)(di)(di)(di)，這類鋼(gang)(gang)不能用(yong)(yong)于(yu)(yu)低(di)(di)(di)(di)溫(wen)(wen)(wen)下工作(zuo)的(de)(de)結構上(shang)，而(er)低(di)(di)(di)(di)溫(wen)(wen)(wen)用(yong)(yong)鋼(gang)(gang)在相應的(de)(de)低(di)(di)(di)(di)溫(wen)(wen)(wen)條件下仍具有(you)良好的(de)(de)韌性和(he)抗脆斷(duan)能力(li)，能夠確保結構的(de)(de)使用(yong)(yong)安全(quan)。低(di)(di)(di)(di)溫(wen)(wen)(wen)鋼(gang)(gang)主(zhu)要用(yong)(yong)于(yu)(yu)低(di)(di)(di)(di)溫(wen)(wen)(wen)下工作(zuo)的(de)(de)容器(qi)、管道和(he)結構，如(ru)石油化(hua)(hua)工設備（化(hua)(hua)肥、乙烯、煤液化(hua)(hua)、液化(hua)(hua)石油氣(qi)等(deng)）、冷凍設備、食品工業及液態氣(qi)體儲存設備等(deng)。低(di)(di)(di)(di)合金低(di)(di)(di)(di)溫(wen)(wen)(wen)用(yong)(yong)鋼(gang)(gang)一般用(yong)(yong)于(yu)(yu)-110~-20℃工況條件。按適用(yong)(yong)溫(wen)(wen)(wen)度(du)范(fan)圍，低(di)(di)(di)(di)合金低(di)(di)(di)(di)溫(wen)(wen)(wen)用(yong)(yong)鋼(gang)(gang)可(ke)分為(wei)-40℃、-70℃、-90℃、-110℃鋼(gang)(gang)；按照鋼(gang)(gang)材(cai)的(de)(de)合金體系(xi)，低(di)(di)(di)(di)合金低(di)(di)(di)(di)溫(wen)(wen)(wen)用(yong)(yong)鋼(gang)(gang)可(ke)分為(wei)不含鎳及含鎳的(de)(de)兩大類。不含鎳的(de)(de)低(di)(di)(di)(di)溫(wen)(wen)(wen)用(yong)(yong)鋼(gang)(gang)一般工作(zuo)溫(wen)(wen)(wen)度(du)在-40℃以(yi)(yi)上(shang)，而(er)含鎳的(de)(de)低(di)(di)(di)(di)溫(wen)(wen)(wen)鋼(gang)(gang)根據鎳含量(liang)的(de)(de)高低(di)(di)(di)(di)，可(ke)以(yi)(yi)工作(zuo)在較(jiao)低(di)(di)(di)(di)的(de)(de)溫(wen)(wen)(wen)度(du)下，如(ru)2.5%Ni鋼(gang)(gang)可(ke)以(yi)(yi)用(yong)(yong)于(yu)(yu)-60℃以(yi)(yi)下，3.5%Ni鋼(gang)(gang)可(ke)以(yi)(yi)用(yong)(yong)于(yu)(yu)-110~-90℃。表1-10和(he)表1-11列出了我國常用(yong)(yong)低(di)(di)(di)(di)合金低(di)(di)(di)(di)溫(wen)(wen)(wen)壓(ya)力(li)容器(qi)用(yong)(yong)鋼(gang)(gang)的(de)(de)化(hua)(hua)學成(cheng)分及力(li)學性能。

  低(di)(di)(di)(di)合(he)金(jin)(jin)低(di)(di)(di)(di)溫(wen)(wen)(wen)用(yong)(yong)鋼(gang)(gang)一般是通(tong)過合(he)金(jin)(jin)元素的固溶強化、晶粒細(xi)化，并通(tong)過正(zheng)火或正(zheng)火＋回(hui)火處理(li)細(xi)化組織(zhi)晶粒，從而獲得良(liang)好的低(di)(di)(di)(di)溫(wen)(wen)(wen)韌性(xing)。在(zai)(zai)低(di)(di)(di)(di)溫(wen)(wen)(wen)用(yong)(yong)鋼(gang)(gang)中(zhong)常用(yong)(yong)合(he)金(jin)(jin)元素是Mn、Ni、V、Nb等(deng)，如我國低(di)(di)(di)(di)溫(wen)(wen)(wen)壓力容器用(yong)(yong)鋼(gang)(gang)09Mn2VDR、15MnNiDR及(ji)09MnNiDR等(deng)，為保證低(di)(di)(di)(di)溫(wen)(wen)(wen)韌性(xing)，在(zai)(zai)低(di)(di)(di)(di)溫(wen)(wen)(wen)用(yong)(yong)鋼(gang)(gang)中(zhong)盡量降低(di)(di)(di)(di)碳含量，并嚴格控制硫、磷含量。低(di)(di)(di)(di)合(he)金(jin)(jin)低(di)(di)(di)(di)溫(wen)(wen)(wen)用(yong)(yong)鋼(gang)(gang)還有相應(ying)的鑄件(jian)、鍛(duan)件(jian)及(ji)管材，JB4727-2000中(zhong)對5種常用(yong)(yong)的低(di)(di)(di)(di)合(he)金(jin)(jin)低(di)(di)(di)(di)溫(wen)(wen)(wen)鋼(gang)(gang)鍛(duan)件(jian)的化學(xue)成分、力學(xue)性(xing)能做出了規定，見表(biao)1-12及(ji)表(biao)1-13所示。