Analysis of Factors Affecting Longitudinal Welded Pipe Process

　　The main process parameters of high-frequency straight seam LSAW steel pipe include welding heat input, welding pressure, welding speed, opening angle, position and size of the induction coil, position of impedance, etc. These parameters have a greater impact on improving the quality.

　　1. Welding heat input: In the welding of high-frequency straight seam welded pipes, the welding power determines the amount of welding heat input. When the external conditions are constant and the input heat is insufficient, the edge of the heated strip cannot reach the welding temperature and remains A solid structure that forms cold welds that do not even fuse.

　　2. Welding pressure (diameter reduction): Welding pressure is the main parameter of the welding process. After the edge of the strip is heated to the welding temperature, the metal atoms are combined to form a weld under the extrusion force of the extrusion roller. The size of the welding pressure affects the strength and toughness of the weld

　　3. Welding speed: The welding speed is also the main parameter of the welding process, which is related to the heating system, the deformation speed of the weld, and the crystallization speed of metal atoms. For high-frequency welding, the welding quality increases with the increase of welding speed, because the shortening of heating time narrows the width of the edge heating zone and shortens the time for forming metal oxides; if the welding speed is reduced, not only the heating zone becomes wider, That is, the heat-affected zone of the weld becomes wider, and the width of the melting zone changes with the input heat, and the inner burrs formed are also larger.

　　4. Opening angle: The opening angle is also called the welding V angle, which refers to the angle between the edge of the strip steel in front of the extrusion roller. Usually, the opening angle varies between 3° and 6°. The size of the opening angle is mainly determined by the position of the guide roller and The thickness of the guide plate is determined.

　　5. The size and position of the induction coil: An induction coil is an important tool in high-frequency induction welding, and its size and position directly affect production efficiency. The power transmitted by the induction coil to the steel pipe is proportional to the square of the surface gap of the steel pipe.

　　6. The function and position of the resistor: the magnet rod of the resistor is used to reduce the high-frequency current flowing to the back of the steel pipe, and at the same time concentrate the current to heat the V angle of the steel strip to ensure that the heat will not be lost due to the heating of the pipe body.