... and stable quality. Product Name Seamless Steel Tubes for Boiler, Pressure Vessel & Heat ExchangerAmerican Standard ASTM A53,ASTM A106,ASTM A333,ASTM ... ,GR6; GR.A-1,GR.CChinese Standard GB 3087,GB 5310,GB 6479,GB 9948,GB 18248,GB/T 18984Grade 10,20,20G,16Mn,37Mn,12CrMo ... .8,17Mn4,15Mo3,13CrMo44British standard BS 3059-1,BS 3059-2,Grade 320,360,440,243Japan Standard JIS G3454,JIS G3461 ...