Papers by Keyword: Laser Welding

Abstract: Tailor welded blanks (TWB) are commonly used in the automotive industry to achieve heterogeneous components, particularly for creating high strength, lightweight parts. Laser welding is one method for joining TWB. Laser welding was used to create TWB composed of stainless steel 304L, with varied thicknesses, in a “patchwork quilt” pattern forming quadrants within the sample. The mechanical properties and quality of the weld were evaluated via tensile testing and microscopy. Truncated pyramids were then formed with weld seams along the faces, and springback and mechanical properties after forming were analyzed. Optical microscopy revealed that the weld seams remained intact after forming. The weld seam location in the center of the pyramid walls did not have a significant impact on the geometrical accuracy of the formed parts. The results of this study show promise for the use of SPIF with quilted TWB to achieve optimal formed part properties for the intended part application.

Abstract: This study evaluates the influence of selected welding parameters on temperature distribution during the production of butt welds in DSS 2304 (EN 1.4362) using a dual IPG YLS 5000 fiber laser with a wavelength of 1.06 μm and a maximum output power of 5 kW. Numerical simulations were performed using ANSYS 2022 R2 software to analyze temperature fields in the weld area. The thermophysical properties of DSS were calculated using JMatPro v6.1 software based on its chemical composition. The geometric model was designed considering test samples with a thickness of 5 mm. A progressive finite element mesh was generated, employing 3D SOLID70 elements with a length of 0.1 mm in the welding zone along the weld trajectory. A conical volumetric heat source model was utilized. Third-kind boundary conditions were applied to define the cooling of welded sheets by convection and radiation through argon and ambient air. Numerical simulations were employed to analyze and optimize performance parameters, including laser power, and the power beam ratio of tandem dual beams for welding DSS 2304. The resulting temperature fields were verified using their comparison with the macrostructures of the produced welds. The mechanical properties of the welded joints were tested through tensile testing and microhardness measurements.

Abstract: Additive manufacturing has significantly advanced in the last two decades and can now produce various mechanical components. However, some limitations exist, such as the size and surface finish of the part. This work reports preliminary results of joining dissimilar metals or alloys by additive manufacturing inspired by welding dissimilar joints. Single laser tracks were produced by laser surface alloying, simulating laser powder bed fusion, using homemade additive manufacturing equipment composed of a computer numerically controlled table and a ytterbium-doped fiber laser operating inside an Argon chamber. Mo, Co, and Cr powders were used to obtain additively manufactured layers on a Ti substrate, aiming to produce a gradient from the Ti to the Co-Cr-Mo alloy. The results showed that increasing the heat input increased the dilution of Ti in the Co-Cr-Mo modified layer and decreased the hardness and the formation of cracks. Obtaining an intermediate layer of Mo reduced the dilution in the upper layers. It increased hardness by 629 ± 20 HV, indicating the feasibility of manufacturing multi-material pieces made of commercially pure Ti with an intermediate layer in Mo and a Co-Cr-Mo alloy. Such pieces aim for future application in hip implants, in which, in addition to the more flexible Ti stem, a femoral head with properties close to the Co-Cr-Mo alloy for excellent wear resistance.

Abstract: In the field of metallurgy, joining dissimilar metals poses a significant challenge due to differences in their physical and chemical properties. One such combination that has gained attention is the joining of AISI 304 steel and Ti Grade 2. These two metals have unique characteristics that make them ideal for various applications, but their differences in thermal conductivity, melting points, and chemical reactivity make achieving a strong and durable joint challenging. Numerical simulations are currently widely used to predict the behaviour of materials during the joining process, as well as to optimize welding parameters in order to achieve a sound weld. In this study, the temperature fields during laser welding of 2 mm thick plates of AISI 304 steel and Ti Grade 2 were analysed based on the numerical simulations of the welding process using ANSYS software. A simulation model for the production of butt joints was developed to assess the impact of laser welding parameters, including laser power, welding speed, and laser beam offset towards the AISI 304 side, on the temperature distribution and weld-pool characteristics. The moving laser heat source was modelled using the conical model with a Gaussian distribution of the laser beam power. The material properties of AISI 304 steel and Ti Grade 2 were calculated as a function of temperature using JMatPro software. The cooling of welding plates by convection and radiation to the argon shielding gas and surrounding air was taken into account using a boundary condition of the third kind. Using the Design of Experiment (DoE) approach, the influence of technological parameters such as welding speed and power on the size of the molten zone on the top and root of the weld was analysed. An optimization of welding parameters was performed, resulting in a surface that represents a basic estimate of the location of admissible solutions in the design space. The results from the numerical simulation and the DoE experiment were compared, and then appropriate technological parameters were proposed for experimental laser welding of the considered dissimilar metals.

Abstract: The examination of WAAM UHS steel laser welds revealed effective material penetration, with desirable geometry showcased by a nearly I-shaped structure. Minor deficiencies were observed at the weld face, while excessive penetration was evident at the weld's root. Cross-sectional analysis indicated no discernible porosity or defects within the weld. Microstructural analysis highlighted fine-grained structures with dispersed precipitates in the WAAM UHS steel base material. Laser welding induced changes in the grain structure, resulting in finer grains and a mixture of ferrite and martensite in the weld zone. Significant increases in hardness were observed in the weld metal and HAZ near the fusion line, attributed to martensite prevalence induced by rapid cooling rates. The hardness of the base material measured around 294 HV, significantly rising in the weld metal, exceeding 401 HV. Mechanical properties altered post-welding, with yield strength decreasing from 749 MPa to 732 MPa. Laser welded WAAM UHS steel had 4% higher tensile strength compared to base material. However, ductility reduced from 27% to 22.5%. Bending fatigue tests revealed a considerable reduction in fatigue limit for laser-welded samples (80 MPa) compared to the base material (419 MPa), with fractures originating from the fusion line between the HAZ and the base material. Notably, the notch sensitivity of ultra-high-strength steels significantly reduces fatigue resistance.

Abstract: The welding of injection molds by laser deposition is a very common procedure in recent years in the maintenance departments of plastic injection factories. This is due to the advantages it has compared to traditional welding methods, namely the speed of the laser welding process, a lower deposition of the metal composition in the repaired area (small volume of deposited material), as well as the accuracy of the deposition on the surface the piece. But, in addition to these advantages, there are also a number of disadvantages compared to classic welding. As the main disadvantage in the case of laser welding of injection molds, the maximum weldable thickness is limited. This paper presents an analysis of weld quality and mechanical fracture of laser deposition according to deposition types and welding techniques of 1.2714 HH pre-hardened steel. The material 1.2714 HH is a basic material used in recent years in the production of molds due to its hardness, namely 40-45 HRC units. In laser welding, different welding strings are possible, each influencing the laser deposition preparation process, the possibility of performing the deposition in the respective area, as well as obtaining a desired mechanical stability. Starting from these considerations, a number of factors will be analyzed using 1.2714HH steel samples: welding strings, welding strings depth, filler material and welding parameters. V – notches were made and filled for welded samples with laser welding deposits. V – notches were made and filled for welded samples with laser welding deposits.

Abstract: In this study, use of adhesive double-sided tape in laser welded ultra-high-strength steel lap joints was evaluated. The test material in the study was abrasion resistant steel (AR400). Optical microscopy was used to investigate macroscopic morphologies of the welds and hardness profiles were measured. Static properties of the joints were evaluated by performing tensile shear strength tests. Fatigue strength of the joints were evaluated by conducting axial fatigue tests. The use of tape resulted in a gap between the welded plates which has several advantages. The gap between the plates markedly increased the width of the weld at the interface of the plates. According to the hardness measurements the hardness of the weld metal was 12% higher compared to the hardness of the AR steel base material. The gap between the plates increased the strength of the joint by up to 20%. The adhesive tape itself did not have a significant effect on the shear strength of the joints. The main advantages of using the tape were a constant air gap and its function as a fastener in welding, so that separate fasteners are not needed.

Abstract: Over the past decade, there has been a steady rise in the application of laser sources; this has led to reduced costs and enhanced output. One aspect that has played a part and helped to the quickening of this phenomena is the invention of new techniques such as laser beam welding systems. These developments in technology have made it feasible to produce both tiny and large parts. The usage of nickel alloy can provide considerable benefits in a wide variety of contexts. The advantages acquired from combining difficult materials, such as metal alloys, are responsible for these benefits. Manufacturing equipment for the chemical, nuclear, maritime, aeronautical, and automotive industries all rely on components made from Inconel 625. It can withstand potentially corrosive situations without losing its outstanding mechanical qualities. Investigation of nickel alloy weldments is required for the improvement of the production method. The goal of this piece is to develop an ANFIS (Adaptive Neuro Fuzzy Inference System) based on Grey theory that can reliably forecast LBW variables. The values predicted by the model were compared with the results of the experiments, and it was discovered that the values found in the experiments are closely related to the values anticipated by the model. The manufacturer can make decisions that are more in accordance with the available facts due to the evidence provided by the performance investigation.

Abstract: The Ultrahigh strength Q&P automotive steel, i.e. QP980, has a broad application prospect in lightweight due to its high strength and good plasticity. In this study, the range of heat input (30 ~ 40 J/mm) was selected by controlling laser power in laser welding of QP980 in order to investigate the microstructure and properties of welded joint. At the heat input of 30 ~ 40 J/mm, the joint of QP980 had acceptable penetration. The weld widths were 417.93 mm, 582.02 mm and 521.56 mm, respectively. The macroscopic morphology of the joint is hourglass type. The microhardness of the welded joint hardening zone is higher than that of the base metal, and the maximum value is 519 HV_0.5. When the heat input is 35 J/mm, the tensile strength of the welded joint is 1109 MPa. The maximum joint factor is 91.88 %. The fracture is close to the base metal. A large number of dimples are observed on the fracture surface, implying as ductile fracture. Based on the EBSD results, the proportion of low angle grain boundary was consistent with mechanical properties. A large number of deformation twins are formed in the 35 J/mm sample through deformation, which has a great contribution to the strength of the weld.

Abstract: Ni base superalloys are commonly employed in the industrial fields of aerospace, automotive and energy production due to their excellent mechanical properties and corrosion resistance at high temperature. Superficial defects and cracks may occur during both manufacturing process of components and their service life. High energy density welding techniques, electron beam (EBW) and laser beam (LBW) welding, can be used to create efficient repairs. Joints, obtained by EBW and LBW of IN792 directionally solidified (DS) superalloy, have been investigated to determine the presence of defects, and evaluate the mechanical properties related to specific microstructural features. The results showed that a pre-heating temperature (PHT) higher than 200 °C is always necessary to prevent the formation of hot cracks in the molten zone (MZ) and heat affected zone (HAZ). The process parameters have been optimized to get a good quality of the seams (lack of macro-defects, a good penetration depth and width). Some preliminary test of post-welding heat treatments (PWHTs) have been investigated to homogenize as far as possible the microstructure and the mechanical properties across the seams. The results obtained by the two techniques, EBW and LBW, have been compared and discussed.