F. Curcio

FEM simulation of metal sheets laser welding with wire filler material

Worldwide manufacturers have already recognized the advantages of using laser welding for a number of applications. Although laser welding is usually performed autogenously, the use of wire filler allows a broader range of welding applications. In this paper a finite element model for key-hole laser welding sources based on experimental observations is presented. The shape for the heat source can be easily changed so to simulate both autogeneous and wire filler laser welding. In the thermal and mechanical calculations the material properties were considered with full temperature dependence. Austenitic stainless and aluminum alloy welds were chosen to validate the model. Simulations of out-of-plane welds were computed using a local coordinates system. A personal computer was used for the calculations. For different plate thicknesses and weld geometries, the calculated fused zones were found in very good agreement with the experimental ones, which proved that the thermal history was computed correctly. When materials with thermal induced microstructure changes are welded, the microstructure in every point of the heat affected zones can be determined as a function of the local temperature cycle.

A basic study on the high power diode laser welding of a titanium alloy

High power diode lasers (HPDLs) have only recently been introduced for materials processing. The advantages of HPDLs include higher energy efficiency and lower running costs. Besides, because of the mass production possibility of semiconductors, the prices of HPDL are currently dropping fast, making these lasers very competitive for future large-scale materials processing systems.This paper describes the application of High Power Diode Laser (HPDL), with maximum output power 2.3 kW and rectangular laser beam spot, for the welding of Ti6Al4V sheets, 1 and 1.5 mm thick. Bead on plate and butt welds were studied and tested using two different covering gases, He and Ar, and flow rates. A metallographic analysis of the cross-sections of welded specimens was carried out in order to measure the morphological characteristics of the welded joint, micro-hardness and tensile tests were performed to complete the mechanical characterization. The results of tests showed that the shape of weld pool and mechanism of laser welding with a rectangular pattern of 808 nm laser radiation differs distinctly from other laser welding mechanisms, reported by the same authors in previous published works.High power diode lasers (HPDLs) have only recently been introduced for materials processing. The advantages of HPDLs include higher energy efficiency and lower running costs. Besides, because of the mass production possibility of semiconductors, the prices of HPDL are currently dropping fast, making these lasers very competitive for future large-scale materials processing systems.This paper describes the application of High Power Diode Laser (HPDL), with maximum output power 2.3 kW and rectangular laser beam spot, for the welding of Ti6Al4V sheets, 1 and 1.5 mm thick. Bead on plate and butt welds were studied and tested using two different covering gases, He and Ar, and flow rates. A metallographic analysis of the cross-sections of welded specimens was carried out in order to measure the morphological characteristics of the welded joint, micro-hardness and tensile tests were performed to complete the mechanical characterization. The results of tests showed that the shape of weld pool and mechanism of lase...

High-speed joining of polymeric plastics using different laser sources (CO2, Nd-YAG, and H.P.D.L.)

In this work five different laser sources, three different CO2 lasers, a ND-YAG and an High Power Diode Laser (H.P.D.L.) have been used to evaluate the joining quality of PE, PP and PC both in thin films (from 0.01 to 0.1 mm thick) and rigid sheets (from 2 to 5 mm thick), as well as in particular lap joints (thin films on rigid sheets). Joining process parameters, such as laser power level, welding speed, pressure and type of covering gas, focusing lens, different joint types, using similar or different polymers, have been analyzed to investigate their influence on the quality of the obtained joints.

Study of titanium sheets HPDL welding phenomenon

Butt joints of titanium alloy Ti6Al4V (AMS 4928Q) thin sheets 1.0 and 1.5 mm thick were continuous-wave High Power Diode Laser (HPDL) laser welded. During course of experiments HPDL ROFIN SINAR DL 020 laser of maximum output power 2.3 kW and a rectangular laser beam spot of 1.8x6.8 mm at focusing distance 82 mm, and 1.8x3.8 mm at 30 mm was used. To provide precise positioning of the laser beam to weld joint and welding track, CNC positioning system was used. The heat input of surfacing was controlled by proper combination of the following parameters: laser beam spot size, beam spot position, laser power and welding speed. Bead on plate welds were produced, to avoid the influence of the sheet edges preparation, the joint fit-up, the welding gap and the laser beam alignment with the welding gap on the welding process. Special clamping device to provide total gas protection of weld root side was used and also special shape trailing shield was used to protect face area of the weld. The commercial grade argon and helium were used as shielding gases. Metallographic examinations and static and dynamic images of the weld pool have proved that the laser welding parameters have very strong influence on the shape of the weld pool, penetration depth, shape of the fusion zone and weld width.Butt joints of titanium alloy Ti6Al4V (AMS 4928Q) thin sheets 1.0 and 1.5 mm thick were continuous-wave High Power Diode Laser (HPDL) laser welded. During course of experiments HPDL ROFIN SINAR DL 020 laser of maximum output power 2.3 kW and a rectangular laser beam spot of 1.8x6.8 mm at focusing distance 82 mm, and 1.8x3.8 mm at 30 mm was used. To provide precise positioning of the laser beam to weld joint and welding track, CNC positioning system was used. The heat input of surfacing was controlled by proper combination of the following parameters: laser beam spot size, beam spot position, laser power and welding speed. Bead on plate welds were produced, to avoid the influence of the sheet edges preparation, the joint fit-up, the welding gap and the laser beam alignment with the welding gap on the welding process. Special clamping device to provide total gas protection of weld root side was used and also special shape trailing shield was used to protect face area of the weld. The commercial grade argon ...

Laser welding optimization of stainless steel lap joints by design of experiment method

This paper reports the findings of a research Design of Experiment (DOE) based to assess the impact of changes in a set of technological parameters on the morphological characteristics - in particular the microhardness of the welded section - of laser welded stainless steel (AISI 304 and AISI 430) lap joints. The Authors also highlight future research directions.