Research On Ship Steels By Fiber Laser-MAG Hybrid And Filling Wire Welding

Laser welding provides an unprecedented combination of excellent beam quality, high welding speed, narrow HAZ, little welding heat distortion and no vacuum. Now manual welding is widely used in shipbuilding industry, we need to use laser welding to improve welding quality and welding intelligentize. Laser welding with filler wire and hybrid welding technology can reduce the accuracy of the assemblability, improve the weld metallurgical characteristics and the mechanical properties of the joint.This paper was carried out basing on the 9 mm Q345 thick ship steel, using laser-arc welding and laser welding with filler wire, to provide technical information for ship steel’s laser welding. Laser welding with filler wire and hybrid welding need to adjust the welding process parameters, including wire feed speed, the amount of defocus, laser power, the light-wire distance, welding speed, current value, etc, so we can get good quality workpieces. Defocus amount determines the size of the heat affected zone. The light-wire distance of welding with filler wire must be controlled in-1 mm to+1 mm, But due to the complex interaction of laser welding and arc, when the light wire distance between 2 mm to 3 mm induced good shape. Laser power increases, penetration weld width increases; welding speed increases, penetration weld width is reduced. Because laser power and welding speed determine the power density, which determines the depth of penetration weld width. When the current value of hybrid welding is between 150 A to 220 A, the workpieces can have a good shape. In filler wire welding, wire feed speed also affects the distribution of laser energy to melt the wire and promotion of the bath.Laser welding with filler wire and hybrid welding improved the wrong side margin of welding and gap adaptation. In filler wire welding the wrong side of tolerance is 1.3 mm, the gap adaptation is 0.9 mm; and in hybrid welding the wrong side of tolerance is 1.8 mm, the gap adaptation is 1.4 mm. Laser welding with filler wire and laser-arc hybrid welding have better prospects in the actual production.In traditional welding mode, Q345 can produce porosity and hot cracking easily. Due to the high energy line of laser welding, small heat-affected zone, high cooling speed, after pre-treatment, under reasonable parameters, selection of argon oxygen mixture protective gas can obtain the weld that have nonporous, non-thermal cracking.The joints of hybrid welding and filler wire welding are made of the weld zone, heat affected zone, and base metal composition. For hybrid welding, weld microstructure includes partial bainite and bainite; heat affected zone has obvious feathery upper bainite and lath martensite; It has the not fully crystallized area, and at grain boundaries has the trend of nucleation growth again. With respect to the hybrid welding, filler wire welding has small organization, because the filler wire welding is under the effect of single laser heat effect, and the time staying in the bath statement is shorter.The tensile test specimens of filler wire welding and hybrid welding were broken at the base; The microhardness of filler wire welding and hybrid welding are lower than the metal heat affected zone, heat affected zone is less than the weld zone. Welding with filler wire’s maximum hardness is 340 HV,6% bigger than hybrid welding; the weld of welding with filler wire’s impact energy is 55 J,12% bigger than hybrid welding. Specimens positive bending angle and back bending angle can reach 180°. Tensile and impact fracture are distributed equiaxed dimples, welded joints are ductile fracture. Under blind hole testing, the residual stress are not high.