The effects of Cr addition on the phase transformation, microstructure and mechanical properties of advanced high-strength steel

Zabihi Gargari, Mohammad; Shahverdi, Hamid Reza; Emami, Mohammad; Askari-Paykani, Mohsen

The effects of Cr addition on the phase transformation, microstructure and mechanical properties of advanced high-strength steel

Document Type : Original Article

Authors

Mohammad Zabihi Gargari ¹

Hamid Reza Shahverdi ¹

Mohammad Emami ²

Mohsen Askari-Paykani ¹

¹ Department of Materials Engineering, Tarbiat Modares University, Tehran, Iran

² Faculty of Engineering, Materials Engineering. University of Bonab. Bonab. Iran.

Abstract

The present study investigates the effects of adding 2.5 wt,% of chromium on the phase transformation, microstructure, and mechanical properties of an advanced medium-manganese high-strength steel containing 4.5 wt.% of manganese. The addition of chromium enhanced the hardenability and a fully martensitic structure formed after the hot-rolling process and air-cooling the rolled sheet and consequently austenitization and rapid cooling which are part of the production route of medium-manganese steel sheets was eliminated. Also, the addition of chromium made it possible to choose higher annealing temperatures because of transforming the carbide phases into carbides stable at higher temperatures. The investigation of the microstructure, phases, and hardness verified the formation of martensite with a Vickers hardness of 461 after hot rolling. Performing intercritical annealing at 700°C for 10 min caused the austenite phase to return to the structure and produced satisfactory mechanical properties, including an ultimate tensile strength of 940 MPa and an elongation of 17%. The reverse austenite phase, the considerable reduction in hardness, and the enhancement of elongation after annealing verified the intercritical annealing process.

Keywords

Chromium

Advanced High-strength Steel

Austenitization and quenching process

Air Cooling

Intercritical annealing

Subjects