普(pu)通低(di)(di)(di)(di)合金(jin)鋼(gang)(gang)(gang)(gang)(gang)(gang)雖溫(wen)(wen)(wen)度(du)降(jiang)低(di)(di)(di)(di)強度(du)有所增(zeng)加(jia)，塑(su)韌(ren)(ren)性(xing)卻急劇(ju)降(jiang)低(di)(di)(di)(di)，這類鋼(gang)(gang)(gang)(gang)(gang)(gang)不(bu)(bu)能用(yong)于(yu)(yu)(yu)低(di)(di)(di)(di)溫(wen)(wen)(wen)下(xia)(xia)(xia)工(gong)(gong)作的(de)結構(gou)上(shang)(shang)，而(er)低(di)(di)(di)(di)溫(wen)(wen)(wen)用(yong)鋼(gang)(gang)(gang)(gang)(gang)(gang)在(zai)相(xiang)應(ying)的(de)低(di)(di)(di)(di)溫(wen)(wen)(wen)條件下(xia)(xia)(xia)仍具有良(liang)好的(de)韌(ren)(ren)性(xing)和抗脆(cui)斷能力，能夠(gou)確(que)保結構(gou)的(de)使(shi)用(yong)安全。低(di)(di)(di)(di)溫(wen)(wen)(wen)鋼(gang)(gang)(gang)(gang)(gang)(gang)主(zhu)要用(yong)于(yu)(yu)(yu)低(di)(di)(di)(di)溫(wen)(wen)(wen)下(xia)(xia)(xia)工(gong)(gong)作的(de)容器(qi)(qi)、管(guan)道和結構(gou)，如(ru)(ru)石油化(hua)工(gong)(gong)設備(bei)（化(hua)肥、乙烯、煤液(ye)化(hua)、液(ye)化(hua)石油氣等）、冷凍設備(bei)、食品工(gong)(gong)業及液(ye)態氣體(ti)儲(chu)存(cun)設備(bei)等。低(di)(di)(di)(di)合金(jin)低(di)(di)(di)(di)溫(wen)(wen)(wen)用(yong)鋼(gang)(gang)(gang)(gang)(gang)(gang)一般用(yong)于(yu)(yu)(yu)-110~-20℃工(gong)(gong)況(kuang)條件。按適用(yong)溫(wen)(wen)(wen)度(du)范圍，低(di)(di)(di)(di)合金(jin)低(di)(di)(di)(di)溫(wen)(wen)(wen)用(yong)鋼(gang)(gang)(gang)(gang)(gang)(gang)可(ke)分為-40℃、-70℃、-90℃、-110℃鋼(gang)(gang)(gang)(gang)(gang)(gang)；按照鋼(gang)(gang)(gang)(gang)(gang)(gang)材(cai)的(de)合金(jin)體(ti)系，低(di)(di)(di)(di)合金(jin)低(di)(di)(di)(di)溫(wen)(wen)(wen)用(yong)鋼(gang)(gang)(gang)(gang)(gang)(gang)可(ke)分為不(bu)(bu)含(han)鎳及含(han)鎳的(de)兩大(da)類。不(bu)(bu)含(han)鎳的(de)低(di)(di)(di)(di)溫(wen)(wen)(wen)用(yong)鋼(gang)(gang)(gang)(gang)(gang)(gang)一般工(gong)(gong)作溫(wen)(wen)(wen)度(du)在(zai)-40℃以(yi)上(shang)(shang)，而(er)含(han)鎳的(de)低(di)(di)(di)(di)溫(wen)(wen)(wen)鋼(gang)(gang)(gang)(gang)(gang)(gang)根據鎳含(han)量(liang)的(de)高低(di)(di)(di)(di)，可(ke)以(yi)工(gong)(gong)作在(zai)較低(di)(di)(di)(di)的(de)溫(wen)(wen)(wen)度(du)下(xia)(xia)(xia)，如(ru)(ru)2.5%Ni鋼(gang)(gang)(gang)(gang)(gang)(gang)可(ke)以(yi)用(yong)于(yu)(yu)(yu)-60℃以(yi)下(xia)(xia)(xia)，3.5%Ni鋼(gang)(gang)(gang)(gang)(gang)(gang)可(ke)以(yi)用(yong)于(yu)(yu)(yu)-110~-90℃。表1-10和表1-11列(lie)出了我國常用(yong)低(di)(di)(di)(di)合金(jin)低(di)(di)(di)(di)溫(wen)(wen)(wen)壓(ya)力容器(qi)(qi)用(yong)鋼(gang)(gang)(gang)(gang)(gang)(gang)的(de)化(hua)學(xue)成分及力學(xue)性(xing)能。

  低(di)(di)合(he)金低(di)(di)溫(wen)(wen)用(yong)鋼一般是通過(guo)合(he)金元(yuan)素(su)(su)的固溶強化、晶粒(li)細化，并(bing)通過(guo)正火或正火＋回(hui)火處理細化組織(zhi)晶粒(li)，從而獲得良好的低(di)(di)溫(wen)(wen)韌性(xing)。在低(di)(di)溫(wen)(wen)用(yong)鋼中常用(yong)合(he)金元(yuan)素(su)(su)是Mn、Ni、V、Nb等(deng)，如我國低(di)(di)溫(wen)(wen)壓力(li)容(rong)器用(yong)鋼09Mn2VDR、15MnNiDR及09MnNiDR等(deng)，為保證低(di)(di)溫(wen)(wen)韌性(xing)，在低(di)(di)溫(wen)(wen)用(yong)鋼中盡(jin)量(liang)降低(di)(di)碳含量(liang)，并(bing)嚴格控制硫、磷含量(liang)。低(di)(di)合(he)金低(di)(di)溫(wen)(wen)用(yong)鋼還有(you)相(xiang)應的鑄件、鍛(duan)件及管材，JB4727-2000中對5種常用(yong)的低(di)(di)合(he)金低(di)(di)溫(wen)(wen)鋼鍛(duan)件的化學(xue)成分、力(li)學(xue)性(xing)能做出(chu)了規定，見(jian)表1-12及表1-13所示。