... 2.WT: 3~30mm 3.ISO Standard,API certificate astm oil pipe 4 inch SpecificationOD 33mm - 406mm(1”~16 ... of 3~30mmStandardGB/T8162,GB/T8163 and DIN/JIS/ASTM standarda. DIN Standard 10#(ST37-2,ST35-8),20 ... #(JIS S45C), 16mn(STS49,STPT49) etc.c. ASTM/AISI Standard10#(ASTM a106/53 Gr.B,A192,A179-C),20 ... A210-A-1,A315-B,AISI1020),45#(AISI1045), 16mn(ASTM A210-C) etc.Usage Appilcation boiler use,water transport, ...