Cr18Ni25Si2鋼屬奧氏體鋼，它適(shi)合在900~1000℃高溫下(xia)工作，是(shi)各(ge)種爐用鋼中(zhong)的(de)一種，其化學成分見(jian)表5-45.

  坡口(kou)(kou)采用(yong)(yong)(yong)(yong)60°V形坡口(kou)(kou)。裝配(pei)時(shi)留間隙（用(yong)(yong)(yong)(yong)2mm厚的塞鐵），兩(liang)端(duan)用(yong)(yong)(yong)(yong)托(tuo)架支(zhi)承，以外圓(yuan)找(zhao)正(zheng)中心，在圓(yuan)周(zhou)上定(ding)位焊(han)(han)4~6處，定(ding)位焊(han)(han)縫(feng)長度25~35mm,焊(han)(han)條用(yong)(yong)(yong)(yong)A407,焊(han)(han)接電源(yuan)采用(yong)(yong)(yong)(yong)直流反(fan)接。此(ci)種鋼的破(po)損(sun)件(jian)或缺陷鑄件(jian)焊(han)(han)補時(shi)，事先(xian)應在裂紋的兩(liang)端(duan)用(yong)(yong)(yong)(yong)直徑(jing)6~8mm鉆頭(tou)鉆孔，然后(hou)沿(yan)裂紋用(yong)(yong)(yong)(yong)風(feng)鏟開坡口(kou)(kou)（坡口(kou)(kou)角(jiao)度60°),并用(yong)(yong)(yong)(yong)有機溶劑清洗坡口(kou)(kou)后(hou)，進行補焊(han)(han)。