| China has been the biggest country for steel production capability in the world in the past several years, but till now, it isn't still able to be regarded as a stronger country for steel production. In aspects of production for steel products of high quality and high technique, our country has a big different with developed countries. Many steel products of high quality and high technique have to be imported from developed countries. To change the situation, Chinese steel companies have to improve the processing condition for production, and develop products of high properties and high technique. In the industries for steel production, rolling is an important way for steel production. Due to the complexity of steel rolling process, the research on rolling process is mainly based on empirical methods and experiments previously. For the design of processing condition, the experiments will be conducted again and again, which results in the prolongation of research period and the rise of cost. Recently with the development of computer technique and finite element method, the method of numerical simulation based on FE theory becomes an important tool for the research of rolling process. Through the simulation and analysis of rolling process, the results such as the workpiece deformation, temperatures change, equivalent strain change, equivalent strain rate change, and microstructure evolution can be obtained, and it may provide a foundation for the optimization of processing parameter of rolling.The simulation system for microstructure evolution during GCr15 steel continuous-hot rolling process is developed, and the continuous-hot rolling process ofφ8 mm GCr15 rod-wire steel at Dongbei Special Steel Group is selected as the research object and simulated. According to the practical situation,φ8 mm GCr15 rod-wire steel continuous-hot rolling process is divided into the phases of the 1-26 pass controlled rolling process and the controlled cooling process after rolling, and studied separately. The main research content and results are as follows:(1)Before the numerical simulation for microstructure evolution of GCr15 steel continuous-hot rolling process, the austenite grain evolution model of GCr15 steel must be developed at first. Therefore, the grain growth tests, single hit compression tests, and double hit compression tests are performed on Gleeble-3800 thermal-mechanical simulator, and the austenite grain evolution model of GCr15 steel is obtained, which can be applied in numerical simulation and includes grain growth model, dynamic recrystallization model, metadynamic recrystallization model, and static recrystallization model, and so on.(2) With the aid of the commercial FE software MSC.Marc, FE model of the 26 passes controlled rolling process ofφ8 mm GCr15 rod and wire steel is established. The process from the outlet of heat furnace to the end of finishing rolling is simulated. Due to the limit of computer speed, the whole process is divided into several sections to be modeled separately. The results such as the workpiece deformation, temperatures change, equivalent strain change, and equivalent strain rate change are analyzed. Also, based on the FE software MSC.Marc, the subroutine system of austenite grain evolution during GCr15 steel rolling process is developed. The model of austenite grain evolution for GCr15 steel is incorporated into the subroutine system to simulate the grain evolution of austenite during GCr15 steel rolling process. The simulated results of temperature agree well with measurements. The simulated results and measured results of grain size agree well with each other.(3) With the aid of FE software MSC.Marc, FE model of GCr15 steel controlled cooling process after finishing rolling is established. Based on the FE software MSC.Marc, the subroutine system of austenite microstructure transformation during GCr15 steel cooling process after rolling is developed, and it can be coupled with FE model of GCr15 steel controlled cooling process in calculation. The TTT curve and the transformation latent of GCr15 steel are considered in the subroutine system to obtain temperatures change and austenite microstructure transformation of GCr15 steel during cooling process. The microstructure obtained by simulation is all pearlite, which agrees with the experiment results. In addition, the subroutine system of austenite microstructure transformation for GCr15 steel is utilized to study austenite microstructure transformation of GCr15 steel under different cooling speed and the same temperature, which is valuable to the optimization of cooling process after rolling.The developed simulation system for microstructure evolution of GCr15 steel continuous-hot rolling process can be utilized to simulate the workpiece deformation, temperatures change, equivalent strain change, equivalent strain rate change, and microstructure evolution during GCr15 steel rolling process, which is valuable to the optimization of rolling process.
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