Experimental and mechanistic study of mechanical property deterioration mechanism of Q235B steel under local stress corrosion action

Abstract

To investigate the corrosion behavior and the mechanism of mechanical property degradation in Q235B steel(6 mm-thick) under the coupling action of axial tension and local corrosion, stress corrosion tests were conducted using a self-designed testing device. This study performed three-dimensional scanning on the corrosion morphology and static tensile testing on locally stress-corroded specimens. The findings indicate that after 3 days of corrosion, the steel's corroded section exhibited a characteristic necking phenomenon, significantly affecting the cross-sectional integrity. A mechanical property degradation model for locally stress-corroded steel, incorporating stress ratio and pit depth parameters, were established through multiple linear regression analysis. The model demonstrates enhanced predictive accuracy, with errors constrained within 15 %. The modified second plastic flow model fits well with the constitutive model of local stress corrosion in Q235B steel. Fracture due to local stress corrosion occurs in the corroded section, with cracks expanding from their formation site to the location of surface pits until eventual fracture. The strength degradation model for corroded steel proposed herein facilitates the safety assessment of in-service corroded steel structures.