普通(tong)低(di)(di)(di)(di)合(he)金(jin)(jin)鋼(gang)(gang)雖溫(wen)(wen)(wen)度(du)(du)降低(di)(di)(di)(di)強度(du)(du)有所(suo)增(zeng)加(jia)，塑韌(ren)性卻急劇降低(di)(di)(di)(di)，這類鋼(gang)(gang)不能用(yong)(yong)于(yu)低(di)(di)(di)(di)溫(wen)(wen)(wen)下(xia)(xia)(xia)工(gong)作的(de)結構(gou)上(shang)，而低(di)(di)(di)(di)溫(wen)(wen)(wen)用(yong)(yong)鋼(gang)(gang)在相應的(de)低(di)(di)(di)(di)溫(wen)(wen)(wen)條件下(xia)(xia)(xia)仍具有良好的(de)韌(ren)性和抗脆斷能力，能夠確保結構(gou)的(de)使用(yong)(yong)安全。低(di)(di)(di)(di)溫(wen)(wen)(wen)鋼(gang)(gang)主(zhu)要用(yong)(yong)于(yu)低(di)(di)(di)(di)溫(wen)(wen)(wen)下(xia)(xia)(xia)工(gong)作的(de)容(rong)器、管道和結構(gou)，如石(shi)油化工(gong)設備（化肥、乙烯、煤(mei)液化、液化石(shi)油氣等(deng)）、冷凍(dong)設備、食品工(gong)業及液態氣體儲存設備等(deng)。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(ban)用(yong)(yong)于(yu)-110~-20℃工(gong)況條件。按適(shi)用(yong)(yong)溫(wen)(wen)(wen)度(du)(du)范圍，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)可(ke)分為(wei)-40℃、-70℃、-90℃、-110℃鋼(gang)(gang)；按照(zhao)鋼(gang)(gang)材的(de)合(he)金(jin)(jin)體系，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)可(ke)分為(wei)不含鎳(nie)及含鎳(nie)的(de)兩大類。不含鎳(nie)的(de)低(di)(di)(di)(di)溫(wen)(wen)(wen)用(yong)(yong)鋼(gang)(gang)一般(ban)工(gong)作溫(wen)(wen)(wen)度(du)(du)在-40℃以(yi)(yi)上(shang)，而含鎳(nie)的(de)低(di)(di)(di)(di)溫(wen)(wen)(wen)鋼(gang)(gang)根據鎳(nie)含量的(de)高(gao)低(di)(di)(di)(di)，可(ke)以(yi)(yi)工(gong)作在較低(di)(di)(di)(di)的(de)溫(wen)(wen)(wen)度(du)(du)下(xia)(xia)(xia)，如2.5%Ni鋼(gang)(gang)可(ke)以(yi)(yi)用(yong)(yong)于(yu)-60℃以(yi)(yi)下(xia)(xia)(xia)，3.5%Ni鋼(gang)(gang)可(ke)以(yi)(yi)用(yong)(yong)于(yu)-110~-90℃。表1-10和表1-11列出了我國(guo)常(chang)用(yong)(yong)低(di)(di)(di)(di)合(he)金(jin)(jin)低(di)(di)(di)(di)溫(wen)(wen)(wen)壓力容(rong)器用(yong)(yong)鋼(gang)(gang)的(de)化學成分及力學性能。

  低(di)(di)合金(jin)低(di)(di)溫(wen)(wen)用(yong)(yong)(yong)鋼(gang)一般是通過合金(jin)元素的固溶強化(hua)、晶(jing)粒(li)細化(hua)，并通過正火(huo)(huo)(huo)或正火(huo)(huo)(huo)＋回火(huo)(huo)(huo)處理細化(hua)組織晶(jing)粒(li)，從(cong)而獲得良好的低(di)(di)溫(wen)(wen)韌(ren)性。在(zai)(zai)低(di)(di)溫(wen)(wen)用(yong)(yong)(yong)鋼(gang)中(zhong)常用(yong)(yong)(yong)合金(jin)元素是Mn、Ni、V、Nb等，如我(wo)國(guo)低(di)(di)溫(wen)(wen)壓力容器(qi)用(yong)(yong)(yong)鋼(gang)09Mn2VDR、15MnNiDR及(ji)09MnNiDR等，為保證(zheng)低(di)(di)溫(wen)(wen)韌(ren)性，在(zai)(zai)低(di)(di)溫(wen)(wen)用(yong)(yong)(yong)鋼(gang)中(zhong)盡量(liang)(liang)降低(di)(di)碳含(han)量(liang)(liang)，并嚴格控制硫、磷含(han)量(liang)(liang)。低(di)(di)合金(jin)低(di)(di)溫(wen)(wen)用(yong)(yong)(yong)鋼(gang)還(huan)有相應的鑄件(jian)(jian)、鍛件(jian)(jian)及(ji)管材，JB4727-2000中(zhong)對(dui)5種常用(yong)(yong)(yong)的低(di)(di)合金(jin)低(di)(di)溫(wen)(wen)鋼(gang)鍛件(jian)(jian)的化(hua)學(xue)成分、力學(xue)性能做出了規(gui)定，見表1-12及(ji)表1-13所(suo)示(shi)。