In addition to the basic requirements of raw materials for producing ordinary high frequency welded steel pipe, the raw material for precision welded pipe must meet the following requirements:
1. Chemical composition:
When smelting, the most important thing is to improve the purity of steel and reduce the content of nonmetallic inclusions in steel. The content of sulfur and phosphorus should be less than 0.03%. In order to adapt to the after-processing such as cold deformation, the sulfur content is better within 0.02%. At the same time, in order to ensure the product has good mechanical properties, cold bending, welding and other technical properties, Nb, Ni, V and other elements should be added into the material in a proper quantity.
2. Shape and size of steel strips:
AGC and flatness control system should be adopted to improve the strip thickness accuracy and strip shape accuracy. At the same time, the control cooling method is adopted to improve the strength and toughness of the steel strip. The accuracy of width during strip slitting should be controlled, and the edge of steel strip should be free of indentation and burr to improve the quality of welding.
3. Corrosion of steel strip surface
The yellow rust on steel strip surface is the water of crystallization of iron oxide. During the welding process, high temperature can make the precipitation of oxygen and hydrogen. If this can not be discharged, and stay in the weld seam area, it will be easy to produce gas hole and micro crack inside of welding seam and change the organizational structure in metal, leading to low material plasticity and elongation, so to avoid the corrosion of the metal surface. So it is important to keep the surface of steel strip material clean.
Post time: May-22-2018