... Derry Fengda International Trade Co., LTD. and Cangzhou OK Anticorrosion Thermal Insulation Project Co.,LTD., Cangzhou Spiral Steel Pipe Co., LTD Laiwu ... SY/T5037-2000, GB/T9711 and API SPEC 5L, the material can be Q235A/B,Q345B, L245,L360 and X42-X80 ... is strictly tested in all process from contact signing, raw material purchasing, producing, to inspection and after sale service, and passed ...