Research On Hot Extrusion Processing Properties For 304LN Stainless Steel Pipe

Steam Generator heat-transfer tube in PWR power station are one of the most important components of domestic which are in urgent need. In this dissertation, mainly basing on experimental research,the hot workablity of 304LN stainless steel,such as ,high temperature deformation behavior, thermal processing map and simulation of tube extrusion were analyzed and studied, And through comparing the simulation experiment, to get the suitable processing parameters.In the dissertation,through by isothermal and equal-strain rate hot compression experiments,we get the deformation behavior on high temperature,and found the 304LN stainless steel is sensitive to temperature and strain rate.During the high temperature deformation process,we can find the dynamic softening by the true stress-strain curve. Through theoretical analysis, the mechanism of softening occurs mainly due to dynamic recrystallization occurred.The establishment of 304LN stainless steel constitutive equation is set up with Zener-Hollomon parameter , the hot deformation activation energy Q and the related material parameters are get.According to the processing map theory given by Prasad, the establishment of the 304LN stainless steel processing maps is based on the dynamic material model. In the parameters scope of Gleeble experiments get from,determine the 304LN stainless steel thermal processing parameters of the optimal range and should be avoided range of the parameters.In the dissertation,we use finite element software Deform to do simulation of the pipe extrusion,based on the rigid-plastic coupled thermo-mechanical FEM theory. According to the plastic deformation area of the temperature and strain rate, whether in the security area of processing map to judge whether the selected parameters accord with the hot extrusion process. Through different extrusion ratio and extrusion speed contrastand ,gives the material processing optimal parameters required for processing.