High-temperature condition impact on tensile strength of typical steel grade

Abstract

Among influencing factors of steel mechanical properties, including tensile strength, the temperature is one of the common risk control aspects requiring careful evaluation. Risk management of thermal impact has been paid attention to because under high-temperature cases, steel structural mechanics properties can have irreversible change. Among them, deterioration in tensile strength of steel due to increment in temperature is crucial to structural preservation. Tensile strength changes due to deterioration performance under a high-temperature working condition are eligible to result in structural mechanism due to exceeding external load compared to remaining tensile strength. Typical types of steel grades have been studied. It was proven that there is no pure deterioration of steel tensile strength with respect to increasing temperature. To reveal the reason for the non-monotonous variation of tensile strength, based on their tensile strength performance, the corresponding hypotheses of causations have been presented. The general explanation is that due to the augment of temperature, there exist impacts on interfaces of steel microstructure lattice which will restrain tensile strength deterioration. Background information supporting each suspect has been introduced to verify the proposed explanation for steel tensile strength deterioration. Based on behaviors of different types of steel ultimate tensile strength deterioration and further analysis towards causations resulting from those behaviors, steel's ultimate tensile strength at high temperature is highly in positive correlation with its ultimate tensile strength at room temperature. Superior influencing factors in determining ultimate tensile strength at room temperature are surface energy between steel lattices in microstructure and steel internal structure deformation under thermal impact. It is suggested that the duplex phase of steel is relatively preferred in manufacturing enhanced ultimate tensile strength steel working in thermal conditions.