Prediction and optimum control of micro-structure in hot deformation of metals for energy saving

采用S15 C材料进行了钢的热变形过程组织预测试验。在加热温度1200℃、镦粗温度1000℃、应变速率10/s、道次间隔时间0- 100 s的工艺条件下，对两步法热镦粗进行了实验和有限元分析研究。研究结果表明：初始晶粒尺寸、动态再结晶速率、动态再结晶晶粒尺寸等微观结构的实验结果与模拟分析结果吻合较好。以多道次镦粗为例，通过实验研究了两道次镦粗过程中道次间保温时间对静态再结晶速率、晶粒尺寸和晶粒长大的影响。此外，通过对再结晶晶粒分布的变形、传热和流变应力三要素的三维有限元协调分析，验证了与实验结果的一致性。三维有限元兼容分析同样验证了预测复杂形状两步热镦粗再结晶晶粒分布的可行性。使用各种碳钢和不锈钢。通过本研究计画期间所测得的热变形加工流变应力-应变曲线资料，建构成数位化的通用资料库共同使用。为了将含Nb Fe-C-Mn钢的流变应力模型应用于普通Fe-C-Mn钢的流变应力模型，提出了一种改进的模型。通过与亚琛大学热变形流变应力数据的比较，发现润滑条件的影响要高出约4 MPa。

The S15C material is used for prediction experiments of microstructure in the hot deformation processing of steel. And, the experiments and the FEM analysis research for the two steps type hot upsetting under the processing conditions of heating temperature 1200℃, upsetting temperature 1000℃, strain rate 10/s and inter-pass time 0-100s, were done. The following results of the research were achieved.A good agreement of the experiment results and the modeling analysis results of microstructures of initial grain size, dynamic re-crystallization rate, dynamic re-crystallization grain size etc. was obtained. As an example of multi-step upsetting processing, the influence of the inter-pass holding time between passing on the microstructure change with the static re-crystallization rate, the grain size and the grain growth in two steps hot upsetting processing, is experimentally clarified. In addition, it was verified to agree to the experiment result well by 3D-FEM compatible analysis with three elements of the deformation, the heat transmission, and the flow stress for the re-crystallization grain distribution. It was similarly verified by 3 D-FEM compatible analysis that it is possible to predict the re-crystallized grain distribution in the two steps hot upset forging of complex shape. Various carbon steels and stainless steels are used. The flow stress-strain curve data of hot deformation processing measured through this research project period, was constructed for the general-purpose data base digitalized together to use. To use the flow stress modeling of Nb addition Fe-C-Mn steel in addition to the flow stress modeling of a usual Fe-C-Mn carbon steel, the modified model was proposed. On comparing the Aachen university's data of flow stress in hot deformation, it has been understood that the influences of the lubrication condition is about a little 4MPa higher.