Thermal creep of austenitic stainless steel plate material under transient heating conditions

Owing to its exceptional features, ASTM Grade 304 (EN 1.4301) austenitic stainless steel is the material of choice for numerous industrial, structural, and architectural applications, particularly where high resistance to corrosion and elevated temperatures is required. Like other metals, stainless steel undergoes time-dependent inelastic deformations at fire temperatures, called ”thermal creep”. The thermal creep of Grade 304 stainless steel has been previously studied under steady-state (isothermal) conditions. However, due to the complexities involved in testing and data analysis, the ”transient creep”, i.e. thermal creep under transient heating regimes, of this material has not yet been studied. In response to this knowledge gap, the present study investigates the thermal creep of Grade 304 stainless steel plate material when subjected to continuously rising temperatures. First, the thermal expansion and the transient stress–strain curves of the stainless steel are obtained at elevated temperatures up to 900 °C. Then, by comparing the material's response under two different heating rates of 5 and 20 °C/min, an analytical creep model is developed that is not only capable of simulating all three stages of creep under transient conditions, but also computationally efficient. Finally, to demonstrate the practical applicability of the developed model for component-level analyses, it is implemented as a user-defined subroutine in ABAQUS finite element software to simulate transient creep in a typical plate structural component. Results show that by reducing the heating rate from 20 to 5 °C/min, due to the transient creep effects, the plate's buckling and failure temperatures can drop by up to around 12% and 6%, respectively, suggesting the significance of transient creep effects in the stainless steel plates.