Design Of Inner-Hole Induction Heater And Its Numerical Study On The Effect Of Temperature Field On Heating Of Large-Scale Cylinders

This article takes the container type cylinder as the research object.This type of cylinder generally has the characteristics of large pipe diameter,thick wall,and large degree of constraint.After the welding operation,it is easy to produce residual stress and even cracks.Therefore,preheating and post-weld heat treatment are performed on such large container type cylinders by means of electromagnetic induction heating in order to achieve the purpose of hydrogen elimination and reduction of residual stress,thereby improve their performance and quality.Since the container type cylinder studied in this paper have many protruding structures on the outer wall(tube seat,etc.),so conventional induction heating coils cannot be used,only from the inside of the cylinders can be considered to heating the cylinder walls.Therefore,a special shape and structure of the heating coil is designed so that it can adapt to the needs of induction heating of the inner wall of the large cylinder.Then based on the basic principle of induction heat treatment of intermediate frequency,ANSYS software was used to establish the mathematical model of the coupling field of induction heating problem,and the boundary conditions were determined.Secondly,using the established model,the induction heating temperature field of this kind of cylinder pressure vessel is analyzed.Through the coupling calculation of electromagnetic field and temperature field,the effects of different induction heating parameters such as number of turns,crucible spacing,distance,current and frequency on electromagnetic induction heating were studied.The relationship among the coil structure parameters and the induction heating electric parameters,the heating effect was obtained through simulation analysis: with the increase of the number of turns of the induction coil,the effect of induction heating becomes better and better.As the pitch distance increases,the heating efficiency gradually decreases.The closer the distance from the workpiece to the induction coil,the magnetic flux leakage decreases and increase the heating efficiency.However,the closer the coil is to the workpiece,the more severe the high-temperature thermal damage of the workpiece,so the distance from the induction coil to the workpiece needs to be considered comprehensively.The effect of the induction coil current and frequency on the temperature is the same.With increasing current or frequency,the heating effect becomes better and better.Through comparison and analysis of various induction heating parameters,we finally determined the induction heating parameters for preheating before welding: current 300 A,frequency 8 kHz,coil-to-workpiece distance 15 mm,coils closely arranged.Induction heating parameters for post-weld heat treatment: current 525 A,frequency 10 kHz,coil-toworkpiece distance 15 mm,coils arranged closely.Finally,the induction heating experiment was carried out using the optimal induction heating parameters.The experimental results were compared with the simulation results.It was found that the two were in good agreement and verified the accuracy of the simulation calculation results.