The strength of 45 thick wall seamless steel pipe is slightly higher than that of 15 steel, with little quenching and no tempering brittleness. It is generally used for bending, calendering, bending, hammer arch and other processing. The welding performance of arc welding and contact welding is good. When gas welding, the thickness is small, and the shape is strict or complex, cracks are easy to occur on the parts. The machinability of cold drawing or normalizing is better than that of annealing. Generally, it is used for manufacturing with little stress and high toughness requirements