Thermal Stress Analysis And Structural Optimization Of Furnace Lining Of Medium Frequency Induction Melting Furnaces

The medium frequency induction furnace has the advantages of flexibility,energy saving and high efficiency,and has been widely used in the modern thermal processing industry.During the use of the induction furnace,the breakage and cracking of the lining directly affect the production safety,melting quality and production cost of the induction furnace.The breakage and cracking of the furnace lining are closely related to the refractory materials,structure,heating process and operating conditions,and the key reason is the change of thermal stress in the furnace lining.Therefore,in response to the defects of easy cracking in the existing integral furnace lining,this paper proposes a new type of composite furnace lining and conducts numerical simulation and experimental research on the variation law of its thermal stress.The specific research content and conclusions are as follows.Firstly,taking the conventional induction heating furnace with a melting capacity of1 t as an example,the temperature field changes in the furnace during the induction heating process was analyzed by using the COMSOL finite element simulation software.And then,the temperature of the outer surface of the charge was used as the temperature load of the furnace lining,and the temperature field and thermal stress field of the furnace lining after continuous melting of 8 furnaces were analyzed by the ANSYS software.The results show that: 1)The heating rate is large when the furnace temperature is below 720 ℃ during the induction heating process,and the heating rate slows down significantly after the furnace temperature exceeding 720 ℃.The reason is that the iron material becomes paramagnetic after reaching the Curie point temperature.The simulation results are consistent with the actual operating conditions,which verifies the reliability of the simulation method;2)With the increase of the number of melting,the maximum thermal stress of the inner wall of the furnace lining also gradually increases,from 126.2 MPa in a single furnace to 193.2MPa after continuous melting for 8 furnaces,and the stress concentration point appears at the low corner of the inner wall.Secondly,the material,operation mode and structure of the traditional furnace lining were optimized.The optimized results are: 1)A composite lining composed of "high aluminum ramming material + mullite fiberboard + high aluminum pounding material" was adopted.After continuous melting of 8 furnaces,the minimum temperature of the outer wall was 187.62 ℃,which is 210.6 ℃ lower than the traditional furnace lining;2)An expansion joint structure that can effectively reduce the thermal stress of the furnace lining was proposed,When the vertical expansion joint is 1mm and the horizontal expansion joint is 1.2mm,the pressure of the contact surface is 31.2 MPa and 37 MPa respectively,which are 58.1% and 53.8% lower than the furnace lining without expansion joints,respectively;3)The low angle stress concentration of the inner wall was arc-shaped,and when the radius R is 50 mm,the maximum stress value of the lining after continuous melting of 8 furnaces decreased by 50.1%.Finally,based on the intensity attenuation theory,the lifespan of the composite lining was predicted.Through the experimental platform testing,it was verified that the service life of the new composite lining has increased by 25.9% compared with the traditional furnace lining.