Effect of cold working on mechanical properties of pure-304L stainless steel with variable temperature - an experimental study

ABSTRACT

In the current investigation, cold work influence on mechanical strength, microstructure, hardness and ductile to brittle transition (DBT) in pure (P) 304 L-stainless steel (SS) (with ultra-low content of sulphur (0.001%) and phosphorus (nil) at several levels of cold work (5%, 10%, 20% and 30%) are reported, which provide valuable information regarding beneficial effects of reduced level of sulphur for the material selection in structural design. The cold work results in dual-phase (γ +$\mathit{\alpha }{ }^{\mathrm{\prime }}$) with distinct values of dislocation densities and grain size that are used in the modified Hall-Petch equation to obtain the corresponding change in yield strength. Cold working up to 30% increased yield strength (${\mathit{\sigma }}_y$) from 280 to 900 MPa, whereas ultimate tensile strength (${\mathit{\sigma }}_u$), increased from 620 to 950 MPa, i.e. an increase of 34.73%. The hardness values increased from 172 to 360 Hv, i.e. an enhancement of 110.5% for a cold work of 30%. The material showed a remarkable enhancement in the impact energy absorption from 200 to 390 J for a temperature change from 77 to 473 K. It is observed that cold working at 5% level reduces the impact energy absorption from 390 to 250 J, i.e. reduction of 35.89% at 298 K. The value of impact energy absorbed by P-304 L-SS was 37% higher than the commercial grade 304 L-SS (sulphur (0.03%), phosphorous (0.04%). The study succinctly brings out the importance of reduced content of sulphur and phosphorus in obtaining superior mechanical properties through cold work.

KEYWORDS:

• Cold deformation
• deformation-induced martensite transformation (DIMT)
• impact energy
• P-304L-SS
• modified-hall-petch equation
• phase transformation

Disclosure statement

No potential conflict of interest was reported by the authors.

Data availability statement

Data is not available due to the nature of this research, participants of this study did not agree for their data to be shared publicly, so supporting data is not available.

Notes

1. *(Here ‘P’ in austenitic steel stands for pure. Although this designation is not used in technical literature, however to distinguish it from commercial grade 304 L SS, letter P has been added for reference purpose only).