Abstract:In high speed gas metal arc welding (GMAW) process, the weld formation quality will get worsen and weld defects like humping bead and undercutting will appear when welding speed exceeds the critical value. The previous investigations have proved that the backward flowing molten jet with high momentum in the weld pool is responsible for the formation of humping bead in high speed GMAW process. An external electromagnetic field generator is developed to conduct proactive control of the

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... ckward flowing molten jet in the weld pool, and adjust the weld pool fluid flow field, in order to suppress the occurrence tendency of the humping bead. Bead-on plate welding experiments are performed on mild steel Q235 test-pieces, and the weld bead appearance under different magnetic flux density are obtained. The high speed camera is used to capture the images of the arc and the weld pool during the welding process. The influences of the exerted magnetic flux density to the arc behavior, the fluid flow inside the weld pool, and the weld bead shape are investigated. The reason why the external electromagnetic field can suppress the humping bead is explained. The results show that external magnetic field can remarkably adjust the weld pool fluid flow field and decrease the momentum of backward flowing molten jet. Therefore, weld defects like humping bead and undercutting can be effectively suppressed, the quality of weld bead is remarkably improved, and the critical welding speed is notably increased. Key words:external magnetic field;fluid flow in weld pool;high speed GMAW;humping bead 0 前言 1