Through-Thickness Microstructure and Strain Distribution in Steel Sheets Rolled in a Large-Diameter Rolling Process

Tadanobu Inoue,Hai Qiu,Rintaro Ueji

doi:10.3390/met10010091

Abstract

The rolling condition for fabricating a low-carbon niobium-microalloyed steel sheet with an ultrafine-grained (UFG) structure was examined through rolling experiments and finite element analysis. A large-diameter rolling process was proposed to create a UFG structure. The rolling was conducted near the transformation point, Ar3, from austenite to ferrite. The Ar3 was measured at the surface and the center of the sheet. First, the through-thickness microstructure and equivalent strain distribution in a 1-pass rolled sheet 2.0 mm thick were examined. In the rolling experiments, the embedded pin method was employed to understand through-thickness deformation. The magnitude of the equivalent strain to obtain a UFG structure was estimated to be 2.0. Based on these results, the fabrication of a 2 mm UFG steel sheet by 3-pass rolling for an initial thickness of 14.5 mm was attempted by the proposed large-diameter rolling process.

Highlights

Research on metallic materials with an ultrafine-grained (UFG) structure is constantly being conducted all over the world, because they have improved mechanical and physical properties without the addition of alloying elements [1,2,3,4,5,6,7,8]
Since a large strain is needed for creating grain refinement, severe plastic deformation (SPD) techniques have been proposed [3], and the mechanical properties and microstructures of UFG materials fabricated through these techniques have been studied in detail
This study aims to determine a rolling condition for fabricating UFG steel sheets through a combination of rolling experiments and finite element analysis (FEA), which is a powerful tool for understanding deformation behaviors during the plastic deformation process

Summary

Introduction

Research on metallic materials with an ultrafine-grained (UFG) structure (below ~2 μm) is constantly being conducted all over the world, because they have improved mechanical and physical properties without the addition of alloying elements [1,2,3,4,5,6,7,8]. The strain introduced in materials by plastic deformation is as important a factor as the deformation temperature for creating UFG structures. Since a large strain is needed for creating grain refinement, severe plastic deformation (SPD) techniques have been proposed [3], and the mechanical properties and microstructures of UFG materials fabricated through these techniques have been studied in detail. Most SPD techniques use batch processes, and a large strain is achieved by repeating the plastic deformation. These SPD techniques do not directly lead to the production of bulk UFG materials on a commercial level

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Conclusion