易削切钢SUM11 SUM12 SUM21 SUM22 SUM23 SUM25 SUM31 SUM32 SUM22L SUN23L SUM24L SUM31L1110 1109 1212 1213 1215 1117 12L14 1135 11449SMn28.15S20.35S20.45S20.SUM22Y12.Y15.Y15Pb.Y20.Y30.Y40Mn.Y100Pb.Y100Bi.易切削不