Numerical simulation of full penetration laser welding of thick steel plate with high power high brightness laser

A comparison of residual stresses in multi pass narrow gap laser welds and gas-tungsten arc welds in AISI 316L stainless steel

https://www.research.manchester.ac.uk/portal/files/65058553/OLEN_5119_edit_report.pdf

Comparison of microstructure and mechanical properties of ultra-narrow gap laser and gas-metal-arc welded S960 high strength steel

In laser welding, typical welding penetration depths are in the order of 1–2 mm/kW laser power. The multipass laser welding technique, based on the narrow-gap approach, is an emerging welding technology that can be applied to thick-section welds by using relatively low laser power, but the process is more complicated since it is necessary to introduce filler wire to narrow-gap weld configurations. The aim of this work was to understand significant process parameters and their interactions in order to control the weld quality in ultra-narrow-gap (1.5 mm gap width) laser welding of AISI grade 316L stainless steel. A 1-kW IPG single-mode fiber laser was used for welding plates that were 5 to 20 mm in thickness using the multiple-pass narrow-gap approach. Design of experiments and statistical modelling techniques were employed to understand and optimise the processing parameters. The effects of laser power, wire feed rate, and welding speed on the weld homogeneity, integrity, bead shape, gap bridgability and surface oxidation were studied. The results were evaluated under different optimising constraints. The results show that the models developed in this work can effectively predict the responses within the factors domain.

Understanding the process parameter interactions in multiple-pass ultra-narrow-gap laser welding of thick-section stainless steels

Through-thickness microstructure and mechanical properties of electron beam welded 20 mm thick AISI 316L austenitic stainless steel

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 plates without filler wire could be carried out at 0.3 m/min welding speed with no porosity or other welding defects. As for 50 mm thick plate, a good weld bead could be obtained with bead-on-plate welding from both sides at 0.2 m/min welding speed.

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

The present invention provides a method of manufacturing a core shroud for a nuclear plant and a nuclear power plant structure in which a groove portion is easily assembled in the case of manufacturing the core shroud having a weld structure of a nuclear power plant by a laser welding, and it is possible to obtain a weld joint portion in which a plastic distortion region and a residual stress are as small as possible, going with a solidification shrinkage of the weld portion. At a time of welding butted portions of a plurality of members constructing a core shroud, a root face is provided in the butted portion, a length of the root face is set to 25% to 95% of a thickness of the thinner one of the butted portions of a plurality of members, a narrow groove is provided in the other than the root face, and the butted portions are welded by a laser welding using a weld wire.

Method of manufacturing core shroud for nuclear power plant and structure of nuclear power plant

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.

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

Yusuke Anma

Papers

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

Method of manufacturing core shroud for nuclear power plant and structure of nuclear power plant

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

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