Eiji Ashida

Welding of thick stainless steel plates up to 50 mm with high brightness lasers

Thick-section stainless steels are widely used in the components and structures for nuclear power plants. Laser welding is being considered as a high-efficiency method instead of arc welding for some components, so as to improve the production efficiency and reduce the residual stresses of the heat-affected zone. In this paper, multipasses narrow-gap welding of 50 mm thick Type 316L plates with an 8 kW disk laser was first investigated. The effect of welding conditions on the weld bead geometry and welding defects was studied. It shows that lack of fusion could be prevented by optimizing the relationship between laser power intensity and the deposited metal volume. Butt joint of 50 mm thick plates with narrow gap could be performed with eight-layers welding at laser power of 6 kW and welding speed of 0.4 m/min. In order to reduce the weld passes further, gas jet assisted laser welding was tried to weld thick Type 316L plates with a 10 kW fiber laser. The result shows that butt-joint welding of 40 mm plate...

Properties of welded joint for narrow gap laser welding of austenitic stainless steels

Thick-section austenitic stainless steels are widely used in components and structures for nuclear power plant. Laser welding is being considered as a high-efficiency method instead of arc welding for some components, in order to improve production efficiency and reduce residual stresses of the heat-affected zone. In this paper, multi-passes narrow gap welding of 50mm thick SUS316L plates with 8 kW disk laser was investigated. The metallurgical and mechanical properties of the weld metal were discussed. It was found that the solidification crack, which usually occurs in the build-up metal for narrow gap laser welding, could be suppressed by controlling the chemical composition of the filler wire, so that the ferrite content of the weld metal could be controlled in an appropriate range. The mechanical properties and the welding residual stress of the narrow gap laser welded joint were evaluated. The maximal tensile residual stress and the range of the tensile stress of the laser welded joint were lower than those of the conventional gas tungsten arc welding (GTAW).Thick-section austenitic stainless steels are widely used in components and structures for nuclear power plant. Laser welding is being considered as a high-efficiency method instead of arc welding for some components, in order to improve production efficiency and reduce residual stresses of the heat-affected zone. In this paper, multi-passes narrow gap welding of 50mm thick SUS316L plates with 8 kW disk laser was investigated. The metallurgical and mechanical properties of the weld metal were discussed. It was found that the solidification crack, which usually occurs in the build-up metal for narrow gap laser welding, could be suppressed by controlling the chemical composition of the filler wire, so that the ferrite content of the weld metal could be controlled in an appropriate range. The mechanical properties and the welding residual stress of the narrow gap laser welded joint were evaluated. The maximal tensile residual stress and the range of the tensile stress of the laser welded joint were lower tha...

High-power fiber laser welding of thick steel at low welding speed

This paper investigated the weld bead formation in welding of thick section stainless steel at 0.2m/min-2m/min welding speeds with a 10kW fiber laser. The influence of shielding conditions, beam spot size and defocused distance on weld bead shape was studied at low welding speeds. The result showed that meandering bead occurring at the laser power of 10kW and the welding speed of 0.3m/min was due to the severe oxidization of the molten pool. This bead meandering could be prevented by adjusting shielding conditions. Beam spot size had a significant influence on the penetration depth, and the penetration depth at 0.1mm beam spot size was smaller than that at 0.2mm beam spot size. The defocused distance where the maximal penetration could be obtained at 10kW laser power and 0.3m/min was about -7mm. In the final, the instability of penetration depth induced by thermal lens effect was also discussed.This paper investigated the weld bead formation in welding of thick section stainless steel at 0.2m/min-2m/min welding speeds with a 10kW fiber laser. The influence of shielding conditions, beam spot size and defocused distance on weld bead shape was studied at low welding speeds. The result showed that meandering bead occurring at the laser power of 10kW and the welding speed of 0.3m/min was due to the severe oxidization of the molten pool. This bead meandering could be prevented by adjusting shielding conditions. Beam spot size had a significant influence on the penetration depth, and the penetration depth at 0.1mm beam spot size was smaller than that at 0.2mm beam spot size. The defocused distance where the maximal penetration could be obtained at 10kW laser power and 0.3m/min was about -7mm. In the final, the instability of penetration depth induced by thermal lens effect was also discussed.

Welding of thick stainless steel plates up to 50mm with high brightness lasers

Thick-section stainless steels are widely used in the components and structures for nuclear power plant. Laser welding is being considered as a high-efficiency method instead of arc welding for some components, so as to improve the production efficiency and reduce the residual stresses of the heat-affected zone. In this paper, multi-passes narrow gap welding of 50mm thick Type 316L plates with an 8 kW disk laser was firstly investigated. The effect of welding conditions on the weld bead geometry and welding defects was studied. It shows that lack-of-fusion could be prevented by optimizing the relationship between laser power intensity and the deposited metal volume. Butt joint of 50mm thick plates with narrow gap could be performed with 8-layers welding at laser power of 6 kW and welding speed of 0.4 m/min. In order to reduce the weld passes further, gas jet assisted laser welding was tried to weld thick Type 316L plates with a 10 kW fiber laser. The result shows that butt-joint welding of 40 mm plated without filler wire could be performed at 0.3 m/min welding speed without porosity and other welding defects. As for 50 mm thick plate, good weld bead could be obtained with bead-on-plate welding from both sides at 0.2 m/min welding speed.Thick-section stainless steels are widely used in the components and structures for nuclear power plant. Laser welding is being considered as a high-efficiency method instead of arc welding for some components, so as to improve the production efficiency and reduce the residual stresses of the heat-affected zone. In this paper, multi-passes narrow gap welding of 50mm thick Type 316L plates with an 8 kW disk laser was firstly investigated. The effect of welding conditions on the weld bead geometry and welding defects was studied. It shows that lack-of-fusion could be prevented by optimizing the relationship between laser power intensity and the deposited metal volume. Butt joint of 50mm thick plates with narrow gap could be performed with 8-layers welding at laser power of 6 kW and welding speed of 0.4 m/min. In order to reduce the weld passes further, gas jet assisted laser welding was tried to weld thick Type 316L plates with a 10 kW fiber laser. The result shows that butt-joint welding of 40 mm plated wi...