Analysis of the heating process of a medium-frequency induction heating pipe bending machine

Medium-frequency induction heating pipe bending machines are commonly used hot-bending equipment, enabling a continuous bending process involving heating, bending, and cooling. These automatic pipe bending machines consist of both mechanical and electrical parts. The mechanical part includes the clamping and force application mechanism, while the electrical part includes the motor and medium-frequency generator. When bending pipes with a medium-frequency induction heating pipe bending machine, the gap between the induction coil and the inner side of the pipe should be smaller, and larger on the outer side, to ensure better heating of the inner pipe wall.

The induction heating width depends on the medium-frequency power, the width of the induction coil, and the relative position of the induction coil and the pipe blank, and is generally about 10-20mm. Stainless steel pipes can be bent using medium-frequency induction heating pipe bending machines. Special attention must be paid to the heating temperature when bending pipes with an automatic pipe bending machine, ensuring it does not fall below 900℃. This is because stainless steel is prone to inter-grade corrosion when heated for extended periods within the temperature range of 500-850℃; new stainless steel should only be cold-bent or hot-bent at a temperature of 1100-1200℃.

Depending on the method of applying bending moment during bending, pipe bending machines are divided into two types: tension bending and pull bending. The tension bending type, using medium-frequency induction heating, completes the bending process by applying axial tension to the pipe blank while simultaneously heating, bending, and cooling with water spray. This type is mainly used for bending pipes with a wall thickness <30mm. This automatic pipe bending machine has a simpler structure than the tension bending type because it does not require longitudinal or transverse jacking mechanisms; it only uses an electric coiling machine to drive a fan-shaped disc to complete the bending operation.

The medium-frequency power supply is used to heat the steel pipe while simultaneously pulling it forward at a uniform speed, causing the heated portion of the pipe to move along a pre-set track, thus forming a bend with a specific bending radius and angle. First, the pipe is installed in place. The bending radius is adjusted by the screw and nut drive of the rocker arm. The pipe is heated to a certain temperature by a medium-frequency induction heating coil and then bent. During bending, hydraulic power is used to pull the steel pipe backward by a trolley. The pipe is bent along the adjusted bending radius at the heated point. After the pipe is deformed, it is cooled by spraying water to obtain the required bent pipe fitting.