Computer Simulation And Experimental Investigation Of Quenching Process

With the rapid development of computer technology and increasing requirements of hardening quality, the computer simulation of quenching process has attracted more and more attentions and become indispensably important means of the present quenching process research and technological design. Because during the real quenching process, complicated physical phenomena will occur inside test-pieces and quenching mediums, for instance, the medium flow field and the temperature field, microstructure field and internal stress field of a test-piece vary drastically with the time. The quantitative changes of these fields are influenced by many factors, including their interactions. At present, the simulation research on these fields is still not mature that further research is needed, such as modeling, numerical methods and the experiment verification of simulated results.This thesis studies particularly the medium flow field in a quenching tank and its relationship with the temperature field, the microstructure field and the internal stress field of a shaft-type test-piece, by using computer simulation and experiment examination. First, the finite-element computing model of the medium flow field in quenching tank is set up. In the light of actual constraint condition, the medium flow field in quenching tank is simulated by the use of the finite-element software ANSYS, and the flow speeds of certain characteristic points in the flow field are measured through the ultrasonic Doppler speed meter. The simulated results are quite match with those of the experiment, so the reliability of numerical simulating is verified. According to the simulated results, the flow-equalizing equipment is improved in order to make the medium flow field in a quenching tank more homogeneous.Then, based on the experiment, the general convective heat-exchange coefficient is worked out by using the method of anti-heat-transfer. Under the full consideration on the interaction of the temperature field, the microstructure field and the internal stress field of a quenching test-piece, the numerical calculation models of the three kinds of fields of a shaft-type test-piece are set up. The finite-element software MARC is applied to build the calculation program of them, and some specific examples are numerically simulated. Through the microstructure analysis and residual stress measurement on a quenching test-piece, the feasibility of the numerical simulation is proved.Finally, on the basis of the numerical simulated results, the relation between themedium flow field in a quenching tank and the temperature field, the microstructure field internal stress field of a shaft-type quenching test-piece is established. Moreover, through the experiment results, the relation between the mediums flow field and the performance of a quenched test-piece is also established. These relations provide a scientific foundation for designing the intelligent quenching tank, planning the quenching process and realizing the intelligent control of quenching process.