Seamless steel pipes are precision-machined to prevent stress corrosion cracking, facilitating on-site welding operations. The high-frequency induction coil should be as close as possible to the extrusion roller position. The internal stress of the steel pipe is small and evenly distributed, which is highly effective. Burrs inside the pipe are generally not removed. After the two edges of the billet are heated to the welding temperature, the casing pipe, under the extrusion of the roller, forms a strong weld by the mutual penetration and crystallization of the common metal grains. The welding temperature is mainly influenced by the high-frequency eddy current thermal power, which, according to relevant formulas, is primarily affected by the current frequency. The eddy current thermal power is proportional to the square of the current excitation frequency; while the current excitation frequency is influenced by the excitation voltage, current, capacitance, and inductance. If the extrusion force is too small, the number of common crystals formed is reduced, leading to a decrease in the strength of the weld metal and potential cracking under stress. After welding and extrusion, weld scars may appear and need to be removed. The removal method involves fixing a cutting tool on the machine frame and using the rapid movement of the welded pipe to flatten the scars. Seamless steel pipes have a longitudinal weld, with both the inner and outer welds being formed by a single submerged arc welding process.
News Center Co., Ltd.
