For the straight steel pipe will be gradually rolled into the circle, and the seam welded into steel pipe, according to its production using the welding process can be divided into continuous welding (forging) steel pipe, resistance welding pipe and arc welding key tube three kinds.
1. Continuous welding (forging) riveting,
Continuous steel welding (forging)steel pipe is a steel pipe which has a straight seam and heated in the heating furnace and then welded to the formed edges by mechanical pressing. Its characteristics are: high production efficiency, low production costs; but the weld quality is poor, comprehensive mechanical performance is poor. At present, it is mainly applied to the design temperature of 0-100 ℃, the design pressure does not exceed 0.6MPa of water and compressed air system.
2. Resistance bare steel
Resistance welding rivet is produced by resistance welding or electric induction welding method, with a straight seam of the steel pipe. Which is characterized by high production efficiency, high degree of automation, welding deformation and residual stress is small; but its high investment in equipment, welding joints of the quality requirements are relatively high; and because the joints are difficult to exist impurities, so the plastic and Low impact toughness. At present, it is mainly applied to the design of water temperature is not higher than 200 ℃, gas, air, heating steam and oil and natural gas industry can be in the reservoir fluid and non-renewable fluid, low pressure pipeline.
3. Arc bad tube
The arc welded steel pipe is a steel pipe produced by an arc welding method. Which is characterized by a complete metallurgical combination of joints, mechanical properties of the joints can be fully achieved or to achieve the mechanical properties of the base metal. After proper heat treatment, the use conditions of the arc welding straight seam steel pipe can be replaced by the condition of the seamless steel pipe. At present, it is mainly applicable to the design of the degree of water is not higher than 200 ℃, gas, air, heating steam and other design pressure is less than 5.0MPa pipe.
