| Duplex stainless steel has ferrite and austenite two-phase structure, so it has goodperformance of welding of single phase austenitic stainless steel and high strength, goodresistance to chloride stress corrosion performance characteristics of single phase ferriticstainless steel. It is a kind of high performance structural material in the true sense, andnow it is increasingly used in chemical, petrochemical, paper and petroleum industries.But because of its large difference on the hot deformation characteristics two phase, thehot workability of the steels is poor during hot working processes. It is easy to producecracks and scrap, so the study on the hot deformation behavior characteristics of duplexstainless steel and how to improve the hot workability of duplex stainless steels isimportant.Hot working performance and the hot deformation behavior of2205duplex stainlesssteel were investigated by using Gleeble-3800thermal simulator system. The constitutiveequation and peak resistance and/or steady stress model were obtained. Combining withthe finite element analysis, the characteristics of stress and strain distribution betweentwo-phase in the hot deformation process was calculated, and the mechanism of thermalcracking of duplex stainless steel was discussed. Besides, the characteristic ofmicrostructure for2205duplex stainless steel was obtained under different deformationparameters, the main results were as follows:(1)In the thermal deformation process, the redistribution of main elements of Ni, Cr,and Mo in duplex stainless steel may lead the austenite phase angles to become obtuse,whereby the stress concentration can be reduced. Also, the stress concentration caused bymorphology, distribution and properties of inclusions will affect hot working performanceof duplex stainless steel.(2) The deformation activation energy Q base on the peak tress pand/or thesteady-state stress sare obtained to be450kJ/mol and461kJ/mol, respectively and thestress index n are obtained to be3.85and4.11, respectively, whereby the hot deformationequations is determined. The results is close to each other so the correctness of the equations is verified. Moreover, the flow curve exists " yield point elongation-like effect ",so that the linear relationship between p, sand ln Zare deviated. By regressionanalysis, the critical ln Zvalue are obtained to be about39.42and40.39, respectively.The research results can provide more understanding for the hot working process of2205duplex stainless steel.(3)The finite element model of stress-strain curve of duplex stainless steel isestablished. According to the stress-strain curve of single-phase ferritic and austeniticstainless steel, the simulated flow curve of the test steel is obtained. Comparing themeasured flow curve and the simulated results, it is indicate that the finite elementanalysis model is reasonable due to well fitness.(4)Base on the mixing law, the prediction model for flow curves is obtained.Combining with the finite element results, the austenite phase and the ferrite phase stressand strain distribution model between the austenite phase and the ferrite phase is obtained. |
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