... .OD:5-630mm 3.WT:0.5-120mm seamless black steel pipe1.Material: ASTM A53/A106, GB8162, 12CrMoV,15CrMo,30CrMo,St37 ... of seamless steel pipe according to GB standard and international standards. Material include carbon constructional quality steel, low alloy structure steel, alloy structure steel etc.