Effect of thermomechanical treatment on the microstructure and mechanical properties of a low-carbon low-alloy steel

A S Dolzhenko,R O Kaibyshev,A N Belyakov

doi:10.1088/1757-899x/1014/1/012007

A S Dolzhenko, R O Kaibyshev + Show 1 more

Open Access

https://doi.org/10.1088/1757-899x/1014/1/012007

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Abstract

The effect of thermomechanical treatment on the microstructure, tensile strength and impact toughness of low-carbon low-alloy steel is considered. The developed microstructure is characterized by grain elongation along the rolling direction. Both the yield strength and the ultimate tensile strength increase with a decrease in test temperature. The ultimate strength at room temperature is 797 MPa, and at 77 K the ultimate strength increases to 1198 MPa. The steel samples subjected to tempforming exhibit impact toughness of KCV = 410 J/cm2 at room temperature. A decrease in the test temperature to 233 K leads to a slight decrease in the KCV value to 340 J/cm2. It should be noted that the impact specimens are not completely fractured even at a test temperature of 233 K, suggesting higher real values of impact toughness.

Highlights

High-strength low-alloy steels are one of the most widely used classes of materials
The ultimate strength at room temperature is 797 MPa, and at 77 K the ultimate strength increases to 1198 MPa
The steel samples subjected to tempforming exhibit impact toughness of KCV = 410 J/cm2 at room temperature

Summary

Introduction

High-strength low-alloy steels are one of the most widely used classes of materials. One of the significant disadvantages of such steels is their relatively high temperature of the ductile-brittle transition, below which the impact toughness of the steels drops sharply, i.e., the steel becomes brittle, which can lead to a sudden catastrophic failure of the construction. An interesting approach to increase the impact toughness and decrease the temperature of the ductilebrittle transition in carbon steels was proposed by Japanese scientists [4] This approach consists in the formation of a lamella type structure with a transverse grain size of about 100 nm and a uniform distribution of dispersed nanoscale particles of secondary phases by means of warm rolling under conditions of tempering. Such thermo-mechanical processing was called tempforming, which allows us to get a promising combination of mechanical properties in low alloyed steels. Besides its high impact toughness, processed steel has high strength due to the reduction of grain size and precipitation hardening

Experimental

Results and discussion

Impact Toughness

Conclusion