A Flow Stress Model of 300M Steel for Isothermal Tension.

Rongchuang Chen,Xianlong Liu,Shiyang Zhang,Fei Feng

doi:10.3390/ma14020252

Rongchuang Chen, Xianlong Liu + Show 2 more

Open Access

https://doi.org/10.3390/ma14020252

Copy DOI

Abstract

To investigate the effect of hot working parameters on the flow behavior of 300M steel under tension, hot uniaxial tensile tests were implemented under different temperatures (950 °C, 1000 °C, 1050 °C, 1100 °C, 1150 °C) and strain rates (0.01 s−1, 0.1 s−1, 1 s−1, 10 s−1). Compared with uniaxial compression, the tensile flow stress was 29.1% higher because dynamic recrystallization softening was less sufficient in the tensile stress state. The ultimate elongation of 300M steel increased with the decrease of temperature and the increase of strain rate. To eliminate the influence of sample necking on stress-strain relationship, both the stress and the strain were calibrated using the cross-sectional area of the neck zone. A constitutive model for tensile deformation was established based on the modified Arrhenius model, in which the model parameters (n, α, Q, ln(A)) were described as a function of strain. The average deviation was 6.81 MPa (6.23%), showing good accuracy of the constitutive model.

Highlights

The 300M steel, a kind of low-alloyed ultra-high strength steel, is an important structural material used for large parts in aircrafts, ships, and nuclear power plants
In order to eliminate the influence of necking on the flow behavior in tensile deformation, the true stress and the logarithmic strain could be corrected by measuring the cross-sectional area of the necking zone of the specimen
The flow stress curve shapes gradually transited from single peaked to exponential hardened when the strain rate increased

Summary

Introduction

The 300M steel (yield strength ≥ 1800 MPa), a kind of low-alloyed ultra-high strength steel, is an important structural material used for large parts in aircrafts, ships, and nuclear power plants. Those large structural parts are often hot forged. In the forming of large parts, folding defects usually occur due to the failure of precise material control because of inaccurate flow stress prediction. The understanding of the effects of hot working parameters (e.g., forging temperature, strain rate, strain) on flow behavior is vital for precise constitutive modelling. The strain rate and temperature effects were investigated by Ghavam et al [1] and Huang et al [2], and tensile flow stress models for IMI834 titanium alloy and 42CrMo steel were proposed

Methods

Results

Conclusion