Effect of Tempering Temperature on Microstructure and Properties of a New Type of Nitrogen‐Containing Hot‐Work Die Steel 3Cr7Mo2NiSiVN. Issue 8 (10th April 2022)

• Record Type: Journal Article
• Authors: Liu, Fubin; Kang, Congpeng; Qian, Ruiqing; Jiang, Zhouhua; Geng, Xin; Li, Huabing
• Is Part Of: Steel research international. Volume 93:Issue 8(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-04-10
• Subjects: hot-work die steels -- mechanical properties -- microstructures -- precipitates -- tempering; Steel -- Periodicals; Steel -- Metallurgy -- Periodicals; 669.142
• DOI: 10.1002/srin.202200013
• Languages: English
• ISSNs: 1611-3683

Abstract

Abstract : Herein, the effect of tempering temperature on the microstructure evolution and mechanical properties of a new nitrogen‐containing hot‐work die steel 3Cr7Mo2NiSiVN is investigated. The new type of hot‐work die steel is quenched at 1080 °C and then conducts a double tempering from 200 to 700 °C. The quenching microstructure contains martensite, film‐retained austenite, and undissolved precipitates, and these precipitates play a Zener pinning effect role in prior austenite grains growing. Based on the Thermo‐Calc thermodynamic calculation and experimental results, the die steel contains V‐rich M2 N nitride, Cr‐rich M23 C6 carbide, Mo‐rich M6 C carbide, and (Nb, V)‐rich M(C, N) precipitates. A secondary hardening phenomenon occurs and the brittle fracture turns to ductile fracture under the scanning electron microscope (SEM) field when the tempering temperature is 500 °C. Room strength decreases and the plasticity improves with the continual increase of tempering temperature. Many nano‐size spherical M2 N nitride and strip‐like M(C, N) carbonitride precipitate when the tempered temperature exceeds 550 °C with transmission electron microscope (TEM) observation. Finely dispersed M2 N nitride and M(C, N) carbonitride are beneficial for stabilizing microstructure at high temperatures and improving high‐temperature strength. Therefore, the high‐temperature strength of the new type of hot‐work die steel is much higher than that of the traditional hot‐work die steel. Abstract : Herein, a new type of nitrogen‐containing hot‐work die steel 3Cr7Mo2NiSiVN with excellent mechanical properties is investigated. Nitrogen addition induces M2 N nitride and M(C, N) carbonitride precipitates, which enhances precipitates' strengthening effect at high temperatures. The ultimate strength (535 MPa) of new‐type hot‐work die steel is much higher than the traditional H13 steel (300 MPa) under 700 °C test condition.