For the straight welded steel pipe which gradually rolls the steel strip into a loop and welds the joint into a steel pipe, it can be divided into continuous furnace welding (forged welding) steel pipe, electric resistance welded pipe and electric arc welding key according to the welding process used in the production. Three kinds of tubes.
1. Continuous furnace welding (forging) riveting,
The continuous furnace welding (forging) steel pipe is a steel pipe having a straight seam formed by heating the steel strip in a heating furnace and then welding the edges of the crucible by mechanical pressing. Its characteristics are: high production efficiency and low production cost; but the weld quality is poor and the comprehensive mechanical properties are poor. At present, it is mainly suitable for water and compressed air systems with a design temperature of 0-100 ° C and a design pressure of not more than 0.6 MPa.
2. Resistance bare steel
The electric resistance welding riveting pipe is produced by electric resistance welding or electric induction welding, and has a straight welded steel pipe. The utility model has the advantages of high production efficiency, high degree of automation, small deformation and residual stress after welding; but the equipment investment is high, the quality requirement of the welded joint is relatively high; and the joint plasticity is inevitable due to the presence of impurities at the joint. Impact toughness is low. At present, it is mainly suitable for designing water, gas, air, heating steam, etc., which are not higher than 200 °C, and medium and low pressure pipelines, which can be used in the oil and gas industry.
3. Arc breaking tube
The arc welded steel pipe is a steel pipe produced by an electric arc welding method. It is characterized by a complete metallurgical bond of the joint, and the mechanical properties of the joint can fully meet or achieve the mechanical properties of the base metal. After proper heat treatment, the conditions for the use of arc welded straight seam steel pipes can be replaced by the conditions for the use of smls pipes. At present, it is mainly suitable for designing pipes with a design pressure of less than 5.0 MPa, such as water, gas, air, and heating steam, which are not higher than 200 °C.