# Effects of Two-Way Cold Rolling and Subsequent Annealing on the Microstructure and Tensile Properties of Low-Carbon Steel with Different Initial Microstructures

## TL;DR

This study shows how two-way cold rolling and annealing affect the microstructure and strength of low-carbon steel with different starting structures.

## Contribution

The novel contribution is demonstrating how two-way cold rolling improves the strength-ductility balance in martensitic low-carbon steel.

## Key findings

- Two-way cold rolling promotes shear-band formation and increases strain homogeneity compared to one-way rolling.
- In martensitic steel, two-way cold rolling improves the strength-ductility balance by about 15% due to finer, equiaxed ferrite grains.
- Two-way cold rolling accelerates recrystallization in ferrite-pearlite steel when annealed below the Ac1 temperature.

## Abstract

We investigated the effects of two-way cold rolling and subsequent annealing on the microstructure and tensile properties of low-carbon steel with different initial microstructures. Two types of hot-rolled sheet specimens were prepared: specimen P, consisting of ferrite and pearlite, and specimen M, consisting of martensite. The hot-rolled sheets were cold-rolled in two directions and subsequently annealed. Two-way cold rolling promoted shear-band formation compared with one-way cold rolling. Furthermore, the two-way cold-rolled specimens showed higher strain homogeneity than the one-way cold-rolled specimens. When annealed below the Ac1 temperature, two-way cold rolling accelerated recrystallization in specimen P, but not in specimen M. In the intercritically annealed specimen P, two-way cold rolling increased the average size of recrystallized ferrite grains while reducing their aspect ratio. In addition, the strength–ductility balance of the two-way cold-rolled specimen P was similar to that of the one-way cold-rolled specimen P. In contrast, in the intercritically annealed specimen M, two-way cold rolling reduced the average size and the aspect ratio of recrystallized ferrite grains. As a result, the strength–ductility balance of the two-way cold-rolled specimen M was improved by approximately 15% compared with that of the one-way cold-rolled specimen. This improvement was attributed to the formation of fine and equiaxed recrystallized ferrite grains. The present findings provide a basis for applying two-way cold rolling as a microstructure-control strategy in high-strength steels.