Cr18Ni25Si2鋼(gang)屬奧氏(shi)體鋼(gang)，它適合(he)在900~1000℃高溫下工作，是(shi)各(ge)種爐用鋼(gang)中的一(yi)種，其化學成分見表5-45.

  坡口采(cai)用(yong)(yong)(yong)(yong)(yong)60°V形坡口。裝(zhuang)配時留(liu)間隙（用(yong)(yong)(yong)(yong)(yong)2mm厚的(de)塞鐵），兩端(duan)用(yong)(yong)(yong)(yong)(yong)托架(jia)支承，以外圓找(zhao)正中心，在圓周上定位(wei)焊(han)(han)(han)(han)4~6處，定位(wei)焊(han)(han)(han)(han)縫長度25~35mm,焊(han)(han)(han)(han)條用(yong)(yong)(yong)(yong)(yong)A407,焊(han)(han)(han)(han)接電源(yuan)采(cai)用(yong)(yong)(yong)(yong)(yong)直(zhi)流反接。此種鋼的(de)破損件或缺陷(xian)鑄件焊(han)(han)(han)(han)補時，事(shi)先(xian)應在裂紋(wen)的(de)兩端(duan)用(yong)(yong)(yong)(yong)(yong)直(zhi)徑6~8mm鉆頭鉆孔，然后沿裂紋(wen)用(yong)(yong)(yong)(yong)(yong)風鏟(chan)開坡口（坡口角度60°),并用(yong)(yong)(yong)(yong)(yong)有機溶劑清(qing)洗坡口后，進行補焊(han)(han)(han)(han)。