Abstract: A new heat transfer coefficient model with part region is presented, and a plain strain component is regarded as the study objective in this model. Five design variables are selected to do the design of central composite experiment with five factors and five levels. The levels of design variables attained from the experiment design are regard as the technical parameters of gas quenching to simulate the gas quenching process using the FEM software clesigned by ourselves. Some mathematical models of response surface are attained. These mathematical models show the dependencies of distortion, average equivalent residual stress, the standard deviation of surface hardness and average surface hardness with respect to the design variables. The optimization model of multi-objec- tives is presented, and the model is optimized by the non-linear method. The optimization data are regard as the technological parameters to simulate the gas quenching process using the FEM software. The quenching results of after optimization are compared with those of before optimization. The comparison shows that the quenching quality using technological parame- ters after optimization is much better than the quenching qual- ity using technical parameters before optimization. All the items of evaluation objectives are improved after optimization.

Key words: Gas quenching, Multi-objective, Optimization method, Technological parameter