Vliv intenzivního tváření za tepla pomocí simulačního modulu MAXStrain na výslednou strukturu

Abstract

From the point of view of the useful properties of the material, the grain size is, among other things, very important. This depends on the deformation history under the given thermomechanical conditions (i.e. at the given deformation temperature and strain rate). Intensive plastic deformation methods are very effective in this respect. Many of these methods are implemented at temperatures lower than the recrystallization temperature of the deformed material. In this case, the refinement of the grain is mainly due to its fragmentation due to the enormous deformation introduced. Another possibility is a large cumulative strain, especially during hot forming. This issue will be the subject of this work. Grain refinement in this case is given by the combined effect of various recrystallization processes. It can also be supported by a suitable cooling regime during which a phase transformation takes place. This is what forming on the MAXStrain II simulation module allows. During the forming of the material on this device, it is problematic to determine the amount of deformation in the partial strains. The main goal of this work was to compile a new computational model for calculating the required strain in individual removals during the deformation cycle on the simulation module MAXStrain II. Following this, a set of tests was performed under different strain conditions in order to analyze the resulting structure after processing on the MAXStrain II simulation module. For these experiments, a DCCT diagram of the investigated steel 25CrMo4 was created using a dilatometric study, on the basis of which the heating and cooling regime was designed. This study was supplemented by metallographic analysis and hardness measurement. The created computational model is a unique solution to the problem of setting the movement of the crossbar during multiple strains on the MAXStrain II simulation module. With its simplicity and practical applicability, it surpasses the computational procedures that have been mentioned so far in the professional literature. Based on the obtained results and the compiled computational model, the parameters of physical simulations of real hot forming processes can be optimized and the results from these simulations can thus have a greater telling value.