IMPROVEMENT ON RESISTANCE ULTRA-HIGH STRENGTH STEEL TO STRESS CORROSION CRACKING

 BY STRAIN-AGING

Gao Ming  Jing Tianfu  Zhang Jingwu   

(Yanshan University)

Xu Shoutian

(The mechanical and Electrical Engineering College of Tianjin)

Zhang Qi Xiong Zhifu

(The Third Institute of Astrogation Ministry)

Abstract: The effect of strain-aging strengthening and toughening of 15CrMnMoV, a low carbon martensitic high strength steel, was compared with the effect of conventional quench-tempering strengthening and toughening of three medium carbon martensitic ultra-high strength steels 40iMnCrNiMoV（300M），45CrMnMoV（D6AC）, 28Cr3SiMnCrNiMoWV（28Cr3）. A high strength (δ0.2=1500~1800MPa) and a high toughness (KIC=85~110 MPa√m, KISCC=76~95MPa√m, KISCC/KIC>0.85) were achieved via strain-aging for ISCrMnMoV steel, moreover, its temper brittleness and cryogenic toughness were improved. In addition to solid-solution hardening, the analysis results of SEM. TEM and inverse pole figures indicate that numerous potential cleavage interface formed by intense texture have a remarkable effect of strengthening and toughening on strain-aged 15CrMaMoV steel. The aging following deformation has a small effect on strength, but the overaging has a remarkable effect on toughness. The combination of delaminating and overaging gives rise to a very high threshold KISCC of strain-aged 15CrMnMoV steel in 5% NaCl aqueous solution.
Key words: Strain-aging  Stress corrosion cracking  Ultra high strength steel
Received 19910608, received in revised form 19921117