Hot Deformation Characteristics and Processing Map of FV520B Martensitic Precipitation-Hardened Stainless Steel
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JMEPEG https://doi.org/10.1007/s11665-019-03974-8
Hot Deformation Characteristics and Processing Map of FV520B Martensitic Precipitation-Hardened Stainless Steel Dan Huang and Wei Feng (Submitted April 3, 2018; in revised form February 23, 2019) Hot deformation characteristics of FV520B martensitic precipitation-hardened stainless steel were investigated in the temperature range of 850-1150 °C and strain rate range of 0.005-0.5 s21 with true strain 0.8 by using Gleeble-3500 thermo-mechanical simulator. Critical stress and corresponding critical strain for dynamic recrystallization initiation were calculated. The constitutive equation was developed by employing Arrhenius constitutive model to represent the nonlinear relationship of true stress and deformation parameters including temperature, strain rate and strain. The correlation coefficient and average absolute relative error are 0.9979 and 2.225%, which indicates the good predictive accuracy of the established constitutive equations. Processing maps were constructed at different plastic strains levels based on dynamic material model (DMM) and established constitutive equation. Combining the processing map with microstructure, the optimum region for good workability is designated as the temperature range of 10501125 °C and strain rate range of 0.027-0.23 s21 with peak efficiency of 0.32. Homogeneous fine and equiaxed dynamic recrystallization (DRX) grains can be found in this optimum according to the microstructure metallographic pictures. Keywords
constitutive equation, dynamic recrystallization, FV520B martensitic precipitation-hardened stainless steel, hot deformation characteristics, processing map
1. Introduction As a new kind of low-carbon martensitic precipitationhardened stainless steel, FV520B was developed on the foundation of Cr13 martensitic stainless steel by Firth-Vickers materials research laboratory (Ref 1, 2). FV520B stainless steel has been widely utilized in a variety of significant engineering structures due to its high strength and hardness, excellent corrosion resistance and weldability (Ref 3-5). Especially, FV520B stainless steel is the dominant material for the manufacture of impeller blades. However, the working environment of the blades is often extremely harsh, in the work blades not only withstand a large centrifugal load, thermal load and gas load, but also bear the gas corrosion and oxidation, which makes the blades prone to produce fatigue damage crack, fracture and reduce the service life of blades (Ref 6-9). At present, many scholars focused their attention on forming the blade using hot forging process, which is of a lot of advantages comparing with the conventional mechanical cutting method (Ref 10-13). During hot deformation process, the deformation resistance and microstructure of the material undergo complex
Dan Huang and Wei Feng, School of Materials Science and Engineering, Wuhan University of Technology, Wuhan 430070, China; and Hubei Key Laboratory of Advanced Technology of Automotive Parts, Wuhan 430070, China. Contact
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