... to ISO9001:2008 and IQNet strictlyMaterialCarbon steel (seam & seamless) ASTM A234and A105 WPB S23520 Greed and 35.8 IStandardASTM / ... GD87-1101HG/T21635-1987 HG/T21631-1990 MaterialCarbon steel :(ASTM A234WPB,,A234WPC,A420WPL6. 20#,Q235,10#,20#,A3, Q235A ... , Cr5Mo, 12Cr1MoV, 10CrMo910,15CrMo, 12Cr2Mo1, ect)Stainless steel :(ASTM A403 WP304,304L,316,316L,321. 1Cr18Ni9Ti, 00Cr19Ni10,00Cr17Ni14Mo2, ect ...