Transactions of Materials and Heat Treatment

Title：Design and optimization on hot die forging process for a crankshaft

Authors： Liu Shaobo Li Xiaofeng

Unit： College of Intelligent Manufacturing and Automobile Chongqing Technology and Business College

KeyWords： crankshaft hot compression Hansel-Spittel model die forging hot processing map

ClassificationCode：TG316；TG146.4

year,vol(issue):pagenumber：2023,48(8):57-65

Abstract：

To control the die forging quality of a crankshaft and avoid forging defects, the rheological data of 40Cr steel at different temperatures and strain rates were obtained by hot compression experiments, and the constitutive relationship of 40Cr steel was obtained by fitting with Hansel-Spittel equation to provide accurate material data for die forging process simulation. Isothermal compression experiment shows that the strain rate and temperature have significant effects on the stress level of 40Cr steel. When the strain rate and strain are the same, the stress decreases with the increasing of temperature, and when the temperature and strain are the same, the stress increases with the increasing of strain rate. Under the condition of low strain rate and high temperature, the material has a significant stress peak. This is because that the higher the temperature is, the lower the strain rate is, the material has enough energy and time for dynamic recrystallization softening during the deformation. Subsequently, the hot processing map of 40Cr steel was established based on the metal stable hot processing theory, and the rationality of the hot processing map was verified by microstructure analysis of compressed samples. Based on the hot processing map, the recommended forming temperature range of a certain crankshaft is 900-1000 ℃, and the strain rate is 0.01-0.1 s-1. Finally, in order to solve the problem of insufficient filling for a certain crankshaft balance block, a strategy based on Latin hypercube sampling, numerical simulation for sample obtainment, Kriging model for response surface construction and genetic algorithm optimization was proposed. The results of numerical simulation and production trial production verify that the strategy can obtain crankshaft forgings with complete filling and no forging defects, improve the forming quality, and reduce the cost of trial and error. In addition, the trial production also verifies that the selected forming temperature and strain rate can obtain the forgings with fine and uniform structure.

Funds：

重庆市教委科研项目（KJQN201904001）

作者简介：刘绍波（1986-），男，学士，实验师,E-mail：LSB3119@163.com

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