Research On Hot Deformation Behavior Of 26Cr2Ni4MoV Steel Used For Large Forgings

As a high-strength alloy structural steel,26Cr2Ni4 MoV steel has the excellent thermal fatigue resistance and the excellent structure stability even under the long-term action of high temperature and continuous stress.The large forgings of 26Cr2Ni4 MoV steel are widely used as the steam turbine rotors for thermal power generation and the generator shaft for wind power generation.Large forgings are forged from cast steel ingots.There will be defects such as shrinkage porosity,element segregation,and columnar grain in the steel ingots.These defects seriously restrict the performance of the forgings and need to be improved by the subsequent open die forging process.Therefore,the open die forging process of large forgings has become an important part of ensuring the performance of forgings.Reasonable forging process design can not only eliminate internal defects of forgings and meet the performance requirements,but also save raw materials,reduce forging procedures and meet the shape and size requirements of forgings.The true stress-strain curves of 26Cr2Ni4 MoV steel were obtained via the isothermal compression experiment.Then the constitutive equation and the processing map based on the dynamic material model(DMM)of the steel were constructed.The finite element model of the 26Cr2Ni4 MoV steel for open die forging were built using DEFORM finite element analysis software.The equivalent strain and temperature of the forging piece during the upsetting and stretching processes were analyzed.Combined with the hot processing diagram,the process stability of the upsetting and stretching process was analyzed,and then a reasonable billet forging process was obtained.The specific content is as follows:(1)A single-pass experiment of uniaxial compression of the cylinder was carried out on the Geeble-3500 thermal simulator to obtain the true stress-strain curve of the 26Cr2Ni4 MoV steel alloy,and construct the constitutive equation of the 26Cr2Ni4 MoV steel open die forging process.(2)Based on the dynamic material model(DMM),the hot processing map of the alloy was constructed to determine the parameters of stable deformation range and dynamic recrystallization region for forging process.(3)Based on the finite element method,the DEFORM finite element analysis software was used to construct the finite element model of open die forging process for the26Cr2Ni4 MoV steel,and combined with the hot processing map,the deformation stability of the forging piece upsetting and stretching process was analyzed.