Numerical Simulation Of 38CrMoAl Steel Rod During Hot Continuous Rolling Process

As the country's basic industry,there are huge demands for steel.Rods are widely used at home and abroad because of the simple cross-section shape and good re-workability.Hot continuous rolling is an important method for steel companies to produce rods,but the complex rolling conditions,varies levels of the rolling equipment and rolling process and other factors have seriously affected the quality of rolled piece.Meanwhile,the requirements for the quality of rods are constantly increasing,and the competition among steel companies is becoming increasingly fierce.So how to reduce the costs and ensure the quality of rolled products have become the main problem for steel companies.Compared with the traditional methods such as empirical method and trial-and-error method,numerical simulation technology is increasingly applied to rolling production because of its short cycle,low costs,and good visualization.The large-scale commercial finite element(FE)software MSC.Marc has been used to simulate the hot continuous rolling process of different sizes of rods.Then the relations between the rolling parameters of 38 CrMoAl steel rod hot rolling process and the stress field,strain field,temperature field,grain size distribution were established,the mechanism and conditions to ensure the properties of 38 CrMoAl steel rod are analyzed,which provides the theoretical basis for the optimization of the rolling process of large-size rod and the improvement of product quality.The research contents and conclusions of this article are as follows:1.With the help of the FE software MSC.Marc,the finite element models of the 38 CrMoAl steel rod of ?22mm and ?100mm in the hot continuous rolling process are established in this article.Based on the previous work and combined with the microstructure evolution model of38 CrMoAl steel,a subroutine for motion control and austenite grain evolution was written,and then embedded into the model through the secondary development function to predict the microstructure evolution behavior of the rolled product during the rolling process.Since there are so many rolling passes,in order to improve the calculation efficiency while ensuring the accuracy of the model,this article divides the whole hot rolling process into several parts according to different rolling stages.The data transfer technology is introduced to realize the information transfer between each part.2.Numerical simulation of the hot rolling process is carried out on the basis of the established 3D multi-field coupled FE models of different sizes,and the corresponding experiments are carried out for the verification of the model reliability.The distribution and evolution of the temperature field,strain field and microstructure field of the rolled piece are analyzed respectively.At the end of rolling process,the temperature differences between center and surface of the?22mm and?100mm rolled pieces are about 30?and 150?,respectively.And the differences in grain size are about 22?m and 60?m,respectively.In addition,the reasons for the uneven distribution of variables such as temperature and grain size in the rolled piece are analyzed,which provides a basis for the process optimization.3.Because of coarser grain size inside the rolled piece and uneven distribution along the cross-section at the end of rolling process of ?100mm rod,this paper designs 5 optimization schemes,including strong air cooling process and strong water cooling process and so on.Both the advantages and disadvantages of the original optimization scheme and the 5 optimization schemes are compared and the strong water cooling optimization scheme is finally determined as the best rolling process scheme of the ?100mm size of 38 CrMoAl steel rod.