Experimental study on deep penetrated laser welding under local subatmospheric pressure

Unlike the normal vacuum chamber that a workpiece is put inside, a new vacuum chamber was designed to put on the welding zone of a workpiece, which has no size limit with this chamber, so that a large and thick plate could be welded with laser under low pressure. In this new vacuum chamber, a local subatmospheric pressure on the welding zone was achieved with side draught by a vacuum pump. A series of spot welding experiments were performed with fiber laser under subatmospheric pressure, normal atmospheric pressure with and without shielding gas side-blowing, respectively. The feature of weld surfaces and cross-section profiles for above different conditions were compared. A high-speed camera was applied to observe the behavior of plasma plume. The results indicated that the deeper welding penetration and narrower weld bead width could be obtained under subatmospheric pressure. The characteristics of spot weld bead under local subatmospheric pressure were quite different from the one under normal atmospheric pressure with shielding gas side-blowing method. The plasma plume was suppressed more effectively by local subatmospheric pressure than that by shielding gas side-blowing. Additional experiments of continuous laser welding under local subatmospheric pressure were tried and sound welds could be obtained.