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

采用S15C材料对钢的热变形过程进行了组织预测实验。在加热温度为1200℃、镦粗温度为1000℃、应变速率为10/s、间道时间为0 ~ 100s的条件下，对两步式热镦粗工艺进行了试验和有限元分析研究。研究结果如下：实验结果与初始晶粒尺寸、动态再结晶速率、动态再结晶晶粒尺寸等微观组织的建模分析结果吻合较好。以多步镦粗为例，实验阐明了两步热镦粗过程中，次间保温时间对组织随静态再结晶速率、晶粒尺寸和晶粒长大的变化的影响。此外，通过对再结晶晶粒分布的变形、传热和流动应力三要素进行三维有限元兼容分析，验证了该方法与实验结果吻合较好。三维有限元相容分析同样验证了预测复杂形状的两步热镦锻的再结晶晶粒分布是可能的。使用各种碳钢和不锈钢。本课题期间测得的热变形加工流动应力-应变曲线数据，建立了通用数据库，并进行了数字化处理。为了在常规Fe-C-Mn碳素钢流动应力模型的基础上，采用Nb加入Fe-C-Mn钢的流动应力模型，提出了修正模型。通过对亚琛大学热变形流动应力数据的比较，了解到润滑条件的影响要高出约4MPa。

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.