... 1, Seamless carbon tubes2,OD:20-325mm3, W.T.:2-50mm4, Certificate: ISO9001, API 5L Perennial: stainless steel plate, seamless steel pipe, thick wall steel pipe, round steel, square ... ): (GB/T8162-2008), alloy tube, high pressure alloy pipe: (GB/T5310-2008) and a series of steel products.Material: 10#, 20#, 35#, 45 ...