Influence of Vanadium on the Microstructure and Mechanical Properties of Medium-Carbon Steels for Wheels

Pengfei Wang,Caifu Yang,Shitong Zhou,Guobiao Lin,Qilong Yong,Zhaodong Li

doi:10.3390/met8120978

Abstract

Steels used for high-speed train wheels require a combination of high strength, toughness, and wear resistance. In 0.54% C-0.9% Si wheel steel, the addition of 0.075 or 0.12 wt % V can refine grains and increase the ferrite content and toughness, although the influence on the microstructure and toughness is complex and poorly understood. We investigated the effect of 0.03, 0.12, and 0.23 wt % V on the microstructure and mechanical properties of medium-carbon steels (0.54% C-0.9% Si) for train wheels. As the V content increased, the precipitation strengthening increased, whereas the grain refinement initially increased, and then it remained unchanged. The increase in strength and hardness was mainly due to V(C,N) precipitation strengthening. Increasing the V content to 0.12 wt % refined the austenite grain size and pearlite block size, and increased the density of high-angle ferrite boundaries and ferrite volume fraction. The grain refinement improved the impact toughness. However, the impact toughness then reduced as the V content was increased to 0.23 wt %, because grain refinement did not further increase, whereas precipitation strengthening and ferrite hardening occurred.

Highlights

Steels for high-speed train wheels must have good strength, toughness, and wear resistance.Pearlite steel, which has a lamellar microstructure obtained by special processing, is exceptionally strong and is often used for this application
V has a high solubility in γ-Fe, and it exists in solution or as a precipitate below austenitizing temperatures
The dissolution and precipitation of V in medium-carbon steel has a beneficial effect on microstructure refinement and ferrite content, and increases the steel strength [5,6]

Summary

Introduction

Steels for high-speed train wheels must have good strength, toughness, and wear resistance.Pearlite steel, which has a lamellar microstructure obtained by special processing, is exceptionally strong and is often used for this application. Steels for high-speed train wheels must have good strength, toughness, and wear resistance. The performance of the microstructure mainly depends on the proeutectoid ferrite and pearlite content, and the size of the pearlite substructure. Microalloying is used to improve the performance of wheel steel by increasing its strength and preventing crack propagation via obtaining a microstructure with good toughness. V has an important effect on the toughness of steel [1,2,3]. Adding 0.1 wt % V to eutectoid steel can delay the pearlite transformation and effectively refine the pearlite colony size and interlamellar spacing [4]. The dissolution and precipitation of V in medium-carbon steel has a beneficial effect on microstructure refinement and ferrite content, and increases the steel strength [5,6]

Methods

Discussion

Conclusion