To eliminate error ellipse size and other defects of seamless steel tubes produced by rolling and heat treatment, generally using the sizing process. As the final production of seamless steel pipe manufacturing sectors sizing process determines the size and geometry of the tubular body, and also affect its mechanical properties.
In sizing rolling, seamless steel pipe diameter is compressed at the same time, the wall thickness will also change, changes in diameter and ovality of the pipe depends mainly on the amount of reduction sizing, and if appropriate adjustment of the sizing press lower volume and temperature, it can eliminate the ovality of seamless steel tubes, while maintaining a predetermined diameter, which also allows seamless improved mechanical properties. However, during the seamless steel pipe sizing, but also make the pipe residual stress, reduce its mechanical strength. Therefore, to ensure the geometric tube
Heat treatment step is an important aspect of production, which can improve organizational performance metallic materials to improve the mechanical properties of the product. Quenching residual stress generated by the important factors also affect the mechanical properties of seamless steel pipe, which is mainly due to residual stresses inside and outside surfaces of the cooling rate of the steel pipe due to the inconsistent.
The residual stress is a common method of project. Mechanism of heat treatment to reduce the welding residual stress is a view that the yield stress of the material increases as the heating temperature decreases, the elastic modulus of the material has declined, so the temperature of the heat treatment process requirements, internal welding materials residual stress exceeds the yield strength of the material at this temperature, plastic deformation occurs, the residual stress is because of this plastic deformation eased, but this time to eliminate the residual stress is limited, residual stress can not be reduced to The heat treatment temperature below the yield strength of the material. In accordance with this theory to develop a process generally choose a higher temperature. Another view is that the heat treatment to reduce the welding residual stress is caused by stress relaxation caused by the creep. Insulation material at higher temperatures, in the role of the internal residual stress will creep, causing stress relaxation and residual stress will drop. Theoretically if given enough time, you can completely eliminate the residual stress, residual stress and unlimited size.
In the sizing process, one seamless geometry is changed; the second is the contact surface contact with each other sizing rolls and seamless transfer of heat between the contact surfaces, and after contacting relationship change, separated from each other but also with Environmental medium heat exchange; Third seamless plastic deformation work volume will be converted into heat, and almost all the friction power irreversibly transformed into surface heat. However, since the time is short sizing rolling process, so heat roll and the environment is not sufficient, the temperature change is smaller rolling tube, in order to simplify the calculation, the temperature difference between the steel pipe can be neglected. Also, consider the amount of sizing seamless small elastic deformation of the roll sizing smaller, both strength and stiffness are significant differences between the sizing roll treated as a rigid body.
Optimum efficiency control of high frequency welded pipe in welding process
In most cases, optimized welding process, power loss can be reduced 50% and can improve the welding quality, reduce downtime, increase production.Stress on the trench corrosion of high-frequency straight seam resistance welding pipe
Trench etching is generally believed that acute heat in the welding process, the results of local tissue metal and chemical change caused by quenching.Technology of straight seam high frequency resistance welded steel pipe
Factors that affect the raw material for the steel pipe welding quality affect the quality of raw materials are mainly steel mechanical properties unstable surface defects and strip geometry deviation big three aspects, therefore, we should focus on these three aspects of control.