Numerical Simulation And Study On Hot Deformation Characteristics Of Heavy Forging Materials For Power Station Equipments

In order to speed up the development of our country’s power generation industryand reduce pollution, it is very necessary to improve turbine efficiency. As the keyheavy forgings of power equipments are used in extremely hard conditions and thecost is very high, it is not allowed to fail. Therefore it is needed to study thecharacteristics of the materials during thermal deformation and embed the models intocomputer simulation to study the macro-mechanical behavior and microstructureevolution. It is of great significance to work out rational forging processes andeffectively control the property and the shape.Based on the Gleeble-1500thermo-mechanical simulation tests of alloy steelX12CrMoNbN10.1.1and SA508-3which are separately used in thermal power andnuclear power generation, the models of flow stress characterized by dynamicrecrystallization for them were put forward. In the models the high flow stress curveswere divided into dynamic recovery region and dynamic recrystallization region. Thecharacteristic parameters of flow stress models were described as function ofZener-Hollomon parameter. By metallographic analyzing the samples and thedynamic recrystallization region of flow stress curves, the Kinetics of dynamicrecrystallization were modeled.Base on DEFORM-3D, a numerical simulation system for analyzing deformationand microstructural evolution of X12CrMoNbN10.1.1steel and SA508-3steel wasdeveloped in the windows platform. The distribution of equivalent strain, equivalentstrain rate, temperature, dynamic recrystallization volume fraction and dynamicrecrystallization grain size in specimen of hot pressing experiment were obtained. Theeffectiveness and reliability of the model were testified.Five experiments of forging processes for X12CrMoNbN10.1.1steel wereperformed. Metallographs and average grain sizes for different processes wereobtained after forging. By analyzing the results of numerical simulation andexperiment data, it can be found that the processes of upsetting three times with stretching three times and stretching three times with upsetting twice have bettereffect on refinement of grain size.