Papers by Author: Qing Hua Lu

Abstract: In this paper, the influence of double wire submerged arc welding parameters on the mechanical properties of high strength low alloy has been investigated. The 20mm steel plate has been welded by double wire submerged arc welding process using different welding parameters. The Charpy absorbed energy of specimens is assessed using impact test at the temperature of -50°C. Testing results show that high heat input parameters will lead to low strength of welded joint. Impact toughness of fusion line is lower than that of other areas of welded joint.

Abstract: The tension, Charpy notch impact and fracture toughness tests on structural steels Q235B and Q345 were carried out under different prestrains. Ductile to brittle transition curves are investigated using Charpy impact tests. The results indicate that the prestrain decreases the impact toughness of both base metal (BM) and weld metal (WM); and increases the ductile-brittle transition temperature as well as the risk of fracture. The prestrain is also found to have a more significant effect in a less ductile material. River marking, the characteristic of cleavage fracture, is observed in the Q235B WM specimens 10% prestrain conditions at 0°C. The fracture surfaces of Q345 WM specimens are characterized by dimple-like structures. The depth of these dimples is decreased under prestrain applied before welding. The CTOD-prestrain curves are obtained using Boltzmann relation.