Microstructure and mechanical properties evaluation of high Ti-V microalloyed steel after coiling process at different temperatures in a hot strip rolling simulation process

Abstract

Today, reducing greenhouse gas emissions is a crucial concern, making the development of steel alloys with optimal desired properties and reduced weight an urgent priority, especially in automotive industries, as it leads to decreased fuel consumption, hence the continued interest in developing high-strength low-alloy steels (HSLA). In this research, the impact of coiling temperature on the final microstructure and mechanical properties of Ti-V HSLA microalloyed steel was investigated. The Gleeble 1500 was used to simulate the hot rolling and coiling processes. The results indicated that reducing coiling temperatures led to a transition in microstructures from polygonal ferrite and pearlite to acicular ferrite and bainite. The optimal coiling temperature for achieving high diffusion rates of microalloying elements and optimal precipitation kinetics to form nanosized precipitates was determined to be 650 °C, where the smallest precipitates were observed of 30 nm. However, the specimen subjected to a lower coiling temperature of 550 °C exhibited the highest yield stress (781 MPa), ultimate tensile strength (971 MPa), and hardness (324 HV), which were attributed to microstructural characteristics such as high dislocation density and a finer grain size of 3 µm compared to 6 µm at 700 °C.