Mechanical properties of steel welds at elevated temperatures

Abstract

The performance of welded members and connections in fire-induced steel structures depends on the mechanical properties of welds at elevated temperatures. At present, the fire resistance of steel welds is estimated by considering the high-temperature strength to be the same as those of structural carbon steel. This is because of the lack of data on mechanical properties of steel welds at elevated temperatures. This paper presents results from an experimental investigation on high-temperature mechanical characteristic of steel welds made using shield metal arc welding (SMAW) process, and E6013 and E7018 electrodes. Steady-state tension tests were conducted on weld metal specimens at 20–800 °C temperature range. Results from these experiments were utilized to evaluate stress-strain response, tensile strength, ultimate strength and the modulus of elasticity as a function of temperature for steel welds. Furthermore, the influence of electrode type in welding process and test temperature on the failure mode and microstructure of steel welds was investigated. Data from the experiments indicate rapid reduction in strength of steel welds at temperatures greater than 400 °C reaching to 50% and 8% of its original ultimate strength at 600 and 800 °C, respectively. Test data also indicate that the yield stress of steel welds decreases faster than that of structural steel at 450–800 °C. Electrode type in the welding process is an important factor besides the exposure temperature, which has a great effect on strength characteristics of steel welds at elevated temperatures.