The residual stress and martensitic transformation of 304 stainless steel in pre-stress grinding: Influence and control on chloride induced SCC

Abstract

In order to investigate the effect of pre-stress grinding on SCC resistance and its mechanism, a series of experiments and simulations were conducted. In the beginning, the SCC behaviors of 304 stainless steel on machined surface were studied. Then the SCC-relevant parameters of the ground surface were characterized in terms of residual stress and microstructures. Following that, a calculation model for evaluating the surface residual stress considering martensitic transformation was proposed. The results suggest that the proper pre-stress in grinding helps reduce the SCC length and density, transform the crack forms and decrease the martensitic content. The higher pre-stress is beneficial to reducing the tensile residual stress and decreasing the depth of the tensile stress layer, thus inhibiting the initiation and propagation of SCC. The release of the pretension provided by the pre-stress during grinding introduces the compressive effect, which reduces the surface stress. The reduction is approximately equal to the value of the pre-stress applied. By validation, the proposed theoretical model has the accuracy required for prediction. Besides pre-stress, smaller cutting depth, lower feed speed, faster linear speed, and grinding wheels with smaller grain sizes are recommended to obtain higher SCC-resistant machined surfaces in pre-stress grinding.

Keywords

• Pre-stress grinding
• SCC resistance
• Residual stress
• Martensitic content
• Austenitic stainless steel