Numerical Simulation And Experimental Study Of Immersion Quenching Cooling Process

Due to the need of environmental protection and energy saving,the lightweight of automobile has become the trend of the development of automobile industry worldwide.Increasing the proportion of lightweight and high-strength materials is the most direct way to achieve automotive lightweight.Immersion quenching is a heat treatment method widely used to improve material properties due to its excellent temperature uniformity.The immersion quenching process is very complicated,involving the temperature field,stress field,microstructure field of the quenching workpiece itself,the flow field of the cooling medium and their interaction.It is very important to predict the surface and internal temperature of the workpiece and control the cooling speed to improve the internal quality and performance of the product.In this paper,the immersion quenching process of 304 stainless steel sheet and 45 steel inner hexagonal wrench was studied by experiment and numerical simulation.The results show that:1.As an important boundary condition in numerical simulation,the critical heat flux coefficient will affect the simulation results of submerged quenching transition boiling and nuclear boiling.Increasing the critical heat flux coefficient will accelerate the cooling rate in the transition boiling stage,and the slope of the temperature curve after Leidenforst point will be steeper.2.Different immersion methods have obvious effects on cooling rate and uniformity of workpiece during cooling process.Horizontal water quenching cooling rate of inner hexagonal wrench is faster,but the cooling rate is not uniform;The cooling rate of the inner hexagonal wrench in vertical water quenching is slower and the cooling is relatively uniform.3.In the process of immersion quenching,too fast cooling speed of workpiece will result in gradient distribution of temperature and thermal stress.The workpiece deforms under the action of thermal stress,causing the surface debris to fall off.4.The numerical simulation method used in this paper can accurately simulate the variation of temperature at any position of the workpiece during the immersion quenching process and the formation of steam bubbles in the boiling heat transfer stage.The temperature field distribution obtained by simulation can be used as a reference for the prediction of thermal stress of workpiece and as a guide for the actual production process.