普通低(di)(di)(di)合(he)金(jin)(jin)(jin)鋼(gang)(gang)(gang)雖溫度(du)(du)(du)降低(di)(di)(di)強(qiang)度(du)(du)(du)有(you)所增(zeng)加，塑韌(ren)性卻(que)急(ji)劇降低(di)(di)(di)，這類(lei)鋼(gang)(gang)(gang)不(bu)能(neng)用(yong)(yong)于(yu)(yu)低(di)(di)(di)溫下(xia)工作的結構上，而低(di)(di)(di)溫用(yong)(yong)鋼(gang)(gang)(gang)在(zai)相應的低(di)(di)(di)溫條(tiao)件下(xia)仍具有(you)良(liang)好(hao)的韌(ren)性和抗脆斷(duan)能(neng)力，能(neng)夠確保(bao)結構的使用(yong)(yong)安全。低(di)(di)(di)溫鋼(gang)(gang)(gang)主要用(yong)(yong)于(yu)(yu)低(di)(di)(di)溫下(xia)工作的容器、管道和結構，如(ru)石(shi)(shi)油化工設(she)備（化肥、乙烯、煤(mei)液(ye)化、液(ye)化石(shi)(shi)油氣等）、冷凍設(she)備、食(shi)品(pin)工業及液(ye)態(tai)氣體儲存設(she)備等。低(di)(di)(di)合(he)金(jin)(jin)(jin)低(di)(di)(di)溫用(yong)(yong)鋼(gang)(gang)(gang)一(yi)(yi)般用(yong)(yong)于(yu)(yu)-110~-20℃工況條(tiao)件。按適用(yong)(yong)溫度(du)(du)(du)范圍，低(di)(di)(di)合(he)金(jin)(jin)(jin)低(di)(di)(di)溫用(yong)(yong)鋼(gang)(gang)(gang)可分為(wei)-40℃、-70℃、-90℃、-110℃鋼(gang)(gang)(gang)；按照(zhao)鋼(gang)(gang)(gang)材(cai)的合(he)金(jin)(jin)(jin)體系，低(di)(di)(di)合(he)金(jin)(jin)(jin)低(di)(di)(di)溫用(yong)(yong)鋼(gang)(gang)(gang)可分為(wei)不(bu)含(han)鎳(nie)及含(han)鎳(nie)的兩大類(lei)。不(bu)含(han)鎳(nie)的低(di)(di)(di)溫用(yong)(yong)鋼(gang)(gang)(gang)一(yi)(yi)般工作溫度(du)(du)(du)在(zai)-40℃以(yi)上，而含(han)鎳(nie)的低(di)(di)(di)溫鋼(gang)(gang)(gang)根(gen)據鎳(nie)含(han)量的高低(di)(di)(di)，可以(yi)工作在(zai)較低(di)(di)(di)的溫度(du)(du)(du)下(xia)，如(ru)2.5%Ni鋼(gang)(gang)(gang)可以(yi)用(yong)(yong)于(yu)(yu)-60℃以(yi)下(xia)，3.5%Ni鋼(gang)(gang)(gang)可以(yi)用(yong)(yong)于(yu)(yu)-110~-90℃。表1-10和表1-11列出(chu)了我國常用(yong)(yong)低(di)(di)(di)合(he)金(jin)(jin)(jin)低(di)(di)(di)溫壓力容器用(yong)(yong)鋼(gang)(gang)(gang)的化學成(cheng)分及力學性能(neng)。

  低(di)(di)合金低(di)(di)溫(wen)(wen)(wen)(wen)用(yong)(yong)鋼一般是(shi)通過合金元素的固溶(rong)強化(hua)(hua)、晶粒(li)細(xi)化(hua)(hua)，并(bing)通過正火或正火＋回火處理細(xi)化(hua)(hua)組織晶粒(li)，從而獲得良好的低(di)(di)溫(wen)(wen)(wen)(wen)韌性(xing)(xing)。在低(di)(di)溫(wen)(wen)(wen)(wen)用(yong)(yong)鋼中常(chang)用(yong)(yong)合金元素是(shi)Mn、Ni、V、Nb等，如(ru)我國低(di)(di)溫(wen)(wen)(wen)(wen)壓力容(rong)器(qi)用(yong)(yong)鋼09Mn2VDR、15MnNiDR及09MnNiDR等，為保(bao)證低(di)(di)溫(wen)(wen)(wen)(wen)韌性(xing)(xing)，在低(di)(di)溫(wen)(wen)(wen)(wen)用(yong)(yong)鋼中盡量(liang)降低(di)(di)碳含量(liang)，并(bing)嚴格控制硫、磷(lin)含量(liang)。低(di)(di)合金低(di)(di)溫(wen)(wen)(wen)(wen)用(yong)(yong)鋼還有相(xiang)應的鑄件(jian)、鍛(duan)件(jian)及管材，JB4727-2000中對5種常(chang)用(yong)(yong)的低(di)(di)合金低(di)(di)溫(wen)(wen)(wen)(wen)鋼鍛(duan)件(jian)的化(hua)(hua)學(xue)成分、力學(xue)性(xing)(xing)能(neng)做出了(le)規定，見表(biao)1-12及表(biao)1-13所(suo)示。