The main process parameters of high-frequency straight seam welded pipe include welding heat input, welding pressure, welding speed, opening angle, the position and size of the induction coil, the position of the impedance, and so on. These parameters have a great impact on improving the product quality, production efficiency, and unit capacity of high-frequency welded pipes. Matching various parameters can make manufacturers obtain considerable economic benefits.
1. Welding heat input
In the welding of high-frequency straight seam welded pipes, the welding power determines the amount of heat input to the welding. When the external conditions are constant and the heat input is insufficient, the edge of the heated strip cannot reach the welding temperature, and still maintains a solid structure to form a cold. Welding can’t even fuse. The lack of fusion caused by the welding heat input is too small. This lack of fusion is usually manifested as the failure of the flattening test, bursting of the steel pipe during the hydrostatic test, or cracking of the weld when the steel pipe is straightened, which is a serious defect. In addition, the welding heat input is also affected by the quality of the edge of the strip. For example, when there is a burr on the edge of the strip, the burr will cause ignition before entering the welding point of the squeeze roll, resulting in a loss of welding power and a reduction in the heat input. small, resulting in unfused or cold welds. When the input heat is too high, the edge of the heated strip exceeds the welding temperature, resulting in overheating or even overburning, and the weld will crack after being stressed. The blisters and holes formed by the excessive heat input are mainly manifested in the failure of the 90° flattening test, the failure of the impact test, and the burst or leakage of the steel pipe during the hydraulic test.
2. Welding pressure (reduction amount)
The 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 under the action of the squeezing roller to form the welding seam. The size of the welding pressure affects the strength and toughness of the weld. If the applied welding pressure is too small, the welding edges cannot be fully fused, and the residual metal oxides in the welding seam cannot be discharged to form inclusions, which will greatly reduce the tensile strength of the welding seam and cause the welding seam to crack easily after being stressed; if the applied welding pressure If it is too large, most of the metal reaching the welding temperature will be extruded, which not only reduces the strength and toughness of the weld but also produces defects such as excessive internal and external burrs or lap welding. The welding pressure is generally measured and judged by the diameter change of the steel pipe before and after the extrusion roller and the size and shape of the burr. The effect of welding extrusion force on burr shape. The welding extrusion amount is too large, the spatter is large and the molten metal is extruded, the burr is large and overturns on both sides of the weld; the extrusion amount is too small, there is almost no spatter, the burr is small and the burr is accumulated; When it is moderate, the extruded burr is upright, and the height is generally controlled at 2.5~3mm. If the welding extrusion amount is properly controlled, the metal streamlines angle of the weld is symmetrical up and down, left and right, and the angle is 55°~65°. The shape of the metal flow line of the weld when the amount of extrusion is properly controlled.
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 the metal atoms. For high-frequency welding, the welding quality increases with the welding speed, because the shortening of the heating time narrows the width of the edge heating zone and shortens the time for metal oxide formation; if the welding speed is reduced, not only does the heating zone become wider, but also That is, the heat-affected zone of the weld becomes wider, and the width of the melting zone changes with the change of the input heat, and the internal burr formed is also larger. Weld line width at different welding speeds. During low-speed welding, it is difficult to weld due to the reduction of the corresponding input heat, and at the same time, affected by the quality of the edge of the board and other external factors, such as the magnetism of the resistor, the size of the opening angle, etc., it is easy to cause a series of defects. Therefore, during high-frequency welding, the fastest welding speed should be selected for production according to the specifications of the product under the conditions allowed by the unit capacity and welding equipment.
Post time: Aug-17-2022