Experimental investigation on mechanical properties of butt welds under high temperature

The mechanical properties of weld joints are important indexes for evaluating the quality of the welding process. This work was performed to supplement the deficiency in studies on the mechanical properties of the weld joints of ship steel structures. In this work, butt weldments composed of Q345B base metal and E5015 electrodes (Q345B-E5015) were subjected to a steady-state tensile test. The mechanical properties of welds subjected to temperatures ranging from 20℃ to 800℃ were investigated. The failure modes of butt weldments under different temperatures were analyzed, and the metallurgical structures that developed in the welding-heat-affected zone and weld joint at different temperatures were observed in accordance with the test results. Next, the parameters of mechanical properties, including the weld tensile strength, elastic modulus, ultimate tensile strength, and ductility, were analyzed in reference to the stress-strain curves of welding specimens subjected to specific temperatures, and the reduction factors of related parameters under different temperatures were obtained. Comparative analysis with relevant design codes revealed that the recommendation of existing codes for the mechanical parameters of Q345B-E5015 weldments based on homogeneous metal materials is not fully applicable to reduction factors. In particular, the recommendations for reduction factors would render butt welds unsafe at temperatures of 500℃ or above. The experimentally obtained relevant parameters and their reduction factors are applicable to the butt-welding fire design of ships and in structural fire safety evaluation. © 2019, Editorial Department of Journal of HEU. All right reserved.