Deformation‐Inhibited Cementite Precipitation Effect and Its Influence on Residual Stress

• Published in: Steel research international Vol. 94; no. 8
• Main Authors: Yan, Chengbo, Ding, Wenhong, Liang, Liang, Lu, Xiaoxuan, Liu, Yisi, Lei, Xiaoling, Xiao, Shaolin
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01.08.2023
• Subjects: carbide precipitations; Carbides; Carbon content; Cementite; Deformation effects; Dilatometry; Dislocation density; Greenwood–Johnson effect; High strength steels; Low carbon steels; Predeformation; Residual stress; Strain energy; Stress relaxation; stress-affected tempering; Tempering
• ISSN: 1611-3683; 1869-344X
• DOI: 10.1002/srin.202200850

High‐strength steels with low carbon content have low stress relaxation during tempering and are prone to distortion during processing. To improve tempering stress relaxation, 10% compression predeformation is introduced. Carbide precipitation is characterized by dislocation density and dilatometry curves, and the evolution of residual stress during tempering is investigated. The results show that predeformation can inhibit cementite precipitation, increase the effective carbon concentration in the ferrite matrix, and induce the diffuse precipitation of alloy carbides. The dispersed alloy carbides provide more interfaces for Mn partitioning, strengthen the transformation plasticity, and enhance the stress relaxation. After tempering at 700 °C for 30 min, the average residual stress and the elastic strain energy of undeformed/predeformed specimens are 39.18/13.25 MPa and 25.40%/90.92%, respectively. Carbide precipitation can be characterized by dislocation density and dilatometry. Predeformation inhibits cementite precipitation during tempering. Inhibition of cementite leads to increased effective carbon concentration in ferrite. Alloy carbides are easier to precipitate due to high carbon concentration. Mn partitioning facilitates the movement of carbon atoms, further enhancing alloy carbide precipitation. Precipitation plasticity of alloy carbides relaxes residual stress.