The production technology of large diameter thick wall steel pipe generally includes hot-rolled, hot rolled, casting and other production methods! The large diameter thick wall steel pipe more common in double-sided submerged arc welding production process, product by bending, commissure, welding, outside welding, straightening, first-class multi-level process, to achieve the American Petroleum Institute standard requirements. The large diameter thick wall steel pipe used in more than a large steel structure construction, to do the main support section, for example, a bridge piling, the undersea piling, high-rise buildings piling. The material is generally used Q345B, Q345C. Lower temperature region will be used Q345D Q345E.