Effect of nitrogen content on the microstructure and mechanical properties of titanium-bearing nonquenched and tempered steel after hot forging

• Published in: Baosteel Technical Research Vol. 17; no. 2; pp. 1 - 6
• Main Authors: Dajiang, Yu, Jiaqiang, Gao, Sixin, Zhao
• Format: Journal Article
• Language: English
• Published: Shanghai Baosteel Technical Research 01.06.2023; Research Institute,Baoshan Iron & Steel Co.,Ltd.,Shanghai 201999,China
• Subjects: Carbon; Energy; Equilibrium; Ferrite; Grain size; Hot forging; Impact strength; Laboratory tests; Mechanical properties; Medium carbon steels; Microstructure; Nitrogen; Solid solutions; Steel; Temperature; Titanium; Toughness; Yield stress; forging; microstructure; titanium; nonquenched and tempered steel; mechanical properties; nitrogen content
• ISSN: 1674-3458
• DOI: 10.3969/j.issn.1674-3458.2023.02.001

The microstructure and mechanical properties of titanium (Ti)-bearing medium-carbon nonquenched and tempered steel with different nitrogen content before and after hot forging were investigated through smelting, forging, and laboratory tests. The results show that the grain size of nonquenched and tempered steel was gradually refined, and the ferrite content gradually increased with an increase in nitrogen content. The grain size of the material with low nitrogen content increased abnormally, and its impact properties significantly decreased after hot forging. The grain size of nonquenched and tempered steel with higher nitrogen content was slightly larger than that before forging, and the tensile and yield strength increased, but the impact toughness was not significantly reduced. The Ti-bearing nonquenched and tempered steel showed better strength and toughness after hot forging with the addition of 0.010%-0.015% nitrogen.