Adjustment and control of heating temperature when using high-frequency induction heating machine to heat treat welds

When the weld seam is heated by a high-frequency induction heating machine, the uniformity, heat penetration and precise control of its temperature are important guarantees for the quality of the heat treatment of the welded pipe. Through heat treatment of the weld seam, the strength and toughness can reach the same level as the base material of the pipe body. This is the importance of adjusting and controlling the heating temperature of the weld seam.

The heat penetration process of using a high-frequency induction heating machine to heat the weld seam using a transverse magnetic field: the heat penetration process of the metal heated by a transverse magnetic field and the metal heated by a longitudinal magnetic field are similar. When the weld seam is heated below the Curie point, due to the strong skin effect of the induced current in the early stage of heating, the weld seam area on the surface of the welded pipe heats up very quickly, and the temperature difference between the inner and outer surfaces is large. At this time, the temperature difference caused by using the flat main coil for heating is larger than that of the grooved main coil. As heating continues, the outer surface weld temperature first reaches the Curie point. Subsequently, the skin effect of the induced current gradually weakens, and the surface heating rate slows down. At this time, the heat conduction from the surface to the inner surface accelerates, the inner surface heats up faster, and the temperature difference between the inside and outside gradually narrows. Finally, when the uniform temperature point is reached, the temperature of the inner and outer surfaces is the same. Achieve uniform temperature and heat penetration.

In the process of using a high-frequency induction heating machine to conduct heat penetration of the weld, the influence of the end shape of the main coil is not obvious. However, the surface power density configured to the main coil has a greater impact on the heat penetration time and the surface temperature difference during the heating process. . This is completely consistent with the characteristics of the longitudinal magnetic field heating process.