Cr18Ni25Si2鋼屬奧(ao)氏體鋼，它適合在900~1000℃高溫(wen)下工作，是(shi)各(ge)種(zhong)爐用鋼中(zhong)的(de)一種(zhong)，其化學(xue)成分見表5-45.

  坡(po)(po)口(kou)采用(yong)(yong)60°V形(xing)坡(po)(po)口(kou)。裝配時留間隙（用(yong)(yong)2mm厚的(de)塞鐵），兩端用(yong)(yong)托(tuo)架(jia)支承，以外圓(yuan)找(zhao)正中心(xin)，在(zai)圓(yuan)周(zhou)上定位焊(han)(han)4~6處，定位焊(han)(han)縫(feng)長度(du)25~35mm,焊(han)(han)條用(yong)(yong)A407,焊(han)(han)接電源采用(yong)(yong)直流反(fan)接。此種(zhong)鋼的(de)破損(sun)件或缺陷鑄件焊(han)(han)補(bu)時，事先(xian)應在(zai)裂紋(wen)(wen)的(de)兩端用(yong)(yong)直徑6~8mm鉆頭鉆孔(kong)，然后沿裂紋(wen)(wen)用(yong)(yong)風鏟(chan)開坡(po)(po)口(kou)（坡(po)(po)口(kou)角度(du)60°),并用(yong)(yong)有機溶劑清洗坡(po)(po)口(kou)后，進行補(bu)焊(han)(han)。