Traditional Welding Research Articles

Repair of Injection Moulds by Welding for Pre-Hardened 1.2714 Hh Steel

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.

Laser welding of dissimilar TiAl/Ti6-Al-4V materials: Effects of rapid in-situ laser pre-heating on microstructure and mechanical properties of the welding joint

TiAl alloy has broad application prospects in the aerospace field. In practical working environments, connecting with other materials is considered an important means of fully utilizing their excellent properties. This study employed a laser in-situ pre-scanning method to preheat the weld seam, achieving the connection between TiAl alloy and Ti-6Al-4V. On this basis, the microstructural evolution of the fusion zone (FZ), fusion line (FL), and heat-affected zone (HAZ) of the welded joint was analyzed in detail. By comparing with traditional welding processes, the effects of laser in-situ preheating on the microstructure and properties of the welded joints were studied. The results showed that the FZ area consists of α2 and martensitic α-Ti, while the FL on the TiAl side features a transition layer of β/B2 phases, providing plasticity and toughness to the welded joint. The in-situ scanning method reduced the cracks generated during welding, resulting in a more uniform distribution of the transition layer. The obtained FZ exhibited higher microhardness. The room temperature tensile strength of the welded joint reached 650 MPa. As the temperature increased, at 400 °C, the tensile strength and elongation reached 571 MPa and 3 %, respectively, significantly higher than the 450 MPa and 1.5 % achieved by conventional welding at the same temperature. When the temperature further increased to 500 °C and 600 °C, Ti-6Al-4V experienced significant softening, becoming the weak point of the welded joint.

Study of the rotating arc on the tribological behavior of hardbanding for oil drilling tubes

In this work, four welded coupons were evaluated with a welding speed of 5, 9, 11 and 13 mm/s. A semi-automatic welding process was used under gas protection, using a 1.6 mm diameter tubular wire. The chemical composition was analyzed on each welded coupon, the dilution percentage was determined, the dimensional of the beads was carried out and the microstructure was characterized by optical microscopy and scanning electron microscopy. In addition, the Vickers microhardness HV2 in the middle of the bead were measured. It was found that the dilution decreased up to 22% (a decrease of 80% compared to traditional welds). Furthermore, the beads presented less refusion with the base material, increasing their width and penetration. A microstructure formed by an “α matrix” was observed, with complex metallic carbides and carboborides which increased in quantity when considering the effects of the rotating arc method Also, it was observed a microstructure formed by a matrix α with complex metal carbides and carboborides that increased in quantity with the effect of the rotating arc. The hardness of the beads varied between 720 and 780 HV2. The weight loss and the friction coefficient decreased with the application of the arc rotation. These changes would be related to the increase in non-metallic phases.

Intelligent Grinding System for Medium/Thick Plate Welding Seams in Construction Machinery Using 3D Laser Measurement and Deep Learning

With the rapid development of the construction machinery industry, thick plate welds are increasingly needing efficient, accurate, and intelligent processing. This study proposes an intelligent grinding system using 3D line laser measurement and deep learning algorithms to solve the problems of inefficiency and inaccuracy existing in traditional weld grinding methods. This study makes use of 3D line laser measurement technology and deep learning algorithms in tandem, which perform automated 3D measurement and analysis to extract key parameters of the weld seam, in conjunction with deep learning algorithms applied on image data of the weld seam for the automatic classification, positioning, and segmentation of the weld seam. The entire work is divided into the following: image acquisition, motion control, and image processing. Based on various weld seam detection algorithms, the selected model was MNet-based DeepLab-V3. An intelligent trimming system for welding seams based on deep learning was constructed. Experiments were conducted to verify the feasibility and accuracy of the 3D line laser measurement technology for weld seam inspections, and that the deep learning algorithm can effectively identify the type and location of the weld seam, thus predicting the trimming strategy. With an accuracy far superior to conventionally based methods in accurate detection and regrinding of weld surface defects, the system proves advantageous for improved weld regrinding productivity and quality. It was determined that the system presents significant advantages in reinforcing weld regrinding when it comes to efficiency and quality, thus initiating a paradigm of using intelligent treatments for medium/thick plate welds in the construction machinery industry.

Weld Pool Flow Characteristics in Double-Wire Arc Welding of Aluminum Alloys: Research by Numerical Simulations

Double-wire arc welding involves simultaneously feeding two wires into a molten pool, improving the efficiency and flexibility of traditional welding techniques. However, the interactions between the two wires and the molten pools are complex, which increases the difficulties in process and composition control. This work focuses on the weld pool flow characteristics in double-wire TIG arc welding. A CFD model incorporating a liquid bridge transfer model was developed to simulate the fluid flow phenomenon. Results show that the bead-forming appearances and flow characteristics of double-wire arc welding show no significant differences from single-wire arc welding. Welding current and welding speed have significant effects on the weld bead dimensions, while only welding current has effects on the flow characteristics. Wire feed XOZ angles show no significant influences on weld bead forming appearances and molten pool flow characteristics. Wire feed XOY angles influence the symmetry of the weld bead and the fluid flow. In 5B71/7055 heterogeneous double-wire arc welding, achieving a uniform distribution of alloy elements is difficult due to the complex convection patterns within the molten pool.

Realization of Friction Stir Welding of Aluminum Alloy AA5754 Using a Ceramic Tool

When engaging in the friction stir welding of aluminum/aluminum joints, the conventional use of tools made of hard metal and steel involves a complex and costly production process. These tools experience wear over welding distances and require frequent replacement to ensure the consistency of the welded seams. The exploration of silicon nitrite as a tool material emerges as a promising alternative in this scenario. The heightened hardness of non-oxide ceramics anticipates a diminished wear rate compared to traditional welding materials, translating into an extended operational lifespan. Nevertheless, the adoption of ceramics introduces challenges initially perceived as detrimental to friction stir welding. The inherent brittleness of silicon nitrite makes it susceptible to breakage under specific loads, and thermal stresses within the component can lead to failure. To mitigate these vulnerabilities, a ceramic material with high thermal shock resistance and a low proportion of sintering additives was used. Employing these accurately designed tools friction stir welding (FSW) was performed on sheets of AA5754, followed by a comprehensive examination of their microstructural and mechanical properties. It was demonstrated that a joint efficiency of 88% can be achieved, and that an increase in hardness within the stir zone occurred as a consequence of grain refinement. Furthermore, the Portevin–Le Chatelier effect, which is characteristic of this alloy, was influenced by the FSW process.

Experimental investigation into friction stir welding of AA6061-T6 and magnesium AZ31B alloy using copper backing plate

Aluminium-magnesium alloys are lightweight and possess superior properties, making them ideal for applications in aerospace, railway, automotive, and marine structures. However, these alloys are challenging to fabricate using traditional fusion welding due to various metallurgical issues. This study investigates the feasibility of joining 3 mm thick dissimilar alloys of aluminium AA6061-T6 and magnesium AZ31B using the friction stir welding (FSW) process with copper as a backing plate. The effects of FSW process parameters, including tool rotational speed (380, 545, 765 rpm), weld speed (20, 31.5, 50 mm min−1), and tilt angle (1°, 2°, 3°), on tensile properties were examined using Taguchi-based grey relational analysis. Temperatures were recorded during the FSW process under different conditions on both sides of the joint. The highest tensile strength of 130.72 MPa, with a joint efficiency of 67.85%, was achieved at a tool rotational speed of 765 rpm, a welding speed of 50 mm min−1, and a tilt angle of 2°. Analysis of variance (ANOVA) for the grey relational grade indicated that the tilt angle had the highest percentage contribution of 43.60%. This study demonstrates the significant influence of FSW parameters on the mechanical properties of aluminium-magnesium joints and highlights the optimal conditions for achieving high joint strength and efficiency.

Transient characteristics of ultra-high frequency adjustable multi-pulse gas tungsten welding arc

In response to the shortcomings of traditional Gas Tungsten Arc Welding (GTAW), such as low penetration, slow welding speed, and low production efficiency, an Ultra-High-Frequency Adjustable Multi-Pulse Gas Tungsten Arc Welding (UFMP-GTAW) process is proposed. This process more effectively concentrates the temperature distribution of the welding arc. To characterize the arc morphology and its dynamic changes, high-speed photography captured ten images of the UFMP-GTAW welding arc within one cycle. The arc image processing algorithm proposed in the paper was used to study the arc's variation characteristics over one cycle. This algorithm includes binarization, arc segmentation, and edge detection to obtain arc morphology parameters. The arc symmetry algorithm is used to symmetrize the arc images for Abel inversion, resulting in the emission coefficient distribution. Further calculations provide the temperature distribution, electrical conductivity distribution, and current density distribution of the arc. Analysis reveals that changes in arc temperature, electrical conductivity, and current density lag behind changes in current. The temperature of the arc spreads from the central axis to the surrounding arc space. When high-frequency current variations occur, the heat input generated by the current increase takes time to transfer to the entire arc space. Conversely, if the current suddenly decreases, the heat input rapidly diminishes. However, because heat transfer takes time, the arc space remains relatively stable for a short period, making the ultra-high-frequency arc form more stable.

Magnetic controlled arc welding technology: a review

PurposeThe purpose of this study is to optimize and improve conventional welding using EMF assisted technology. Current industrial production has put forward higher requirements for welding technology, so the optimization and improvement of traditional welding methods become urgent needs.Design/methodology/approachExternal magnetic field assisted welding is an emerging technology in recent years, acting in a non-contact manner on the welding. The action of electromagnetic forces on the arc plasma leads to significant changes in the arc behavior, which affects the droplet transfer and molten pool formation and ultimately improve the weld seam formation and joint quality.FindingsIn this paper, different types of external magnetic fields are analyzed and summarized, which mainly include external transverse magnetic field, external longitudinal magnetic field and external cusp magnetic field. The research progress of welding behavior under the effect of external magnetic field is described, including the effect of external magnetic field on arc morphology, droplet transfer and weld seam formation law.Originality/valueHowever, due to the extremely complex physical processes under the action of the external magnetic field, the mechanism of physical fields such as heat, force and electromagnetism in the welding has not been thoroughly analyzed, in-depth theoretical and numerical studies become urgent.

Effects of Preheating on the Microstructure of Laser-DED AISI 420

AISI 420 stainless steel (420 SS) is a martensitic type known for its high strength and abrasion resistance, and it is extensively used in hard-facing applications (Refs. 1, 2). However, Type 420 SS contains untempered martensite in the as-welded condition and is generally considered to have poor weldability. Successful arc welding of 420 SS requires proper preheating, post-weld heat treatment, and strict adherence to low hydrogen practices. Direct energy deposition (DED) is a fusion-based additive manufacturing (AM) process that melts metal powders to produce complex shapes and can be used for surfacing or hard-facing operations. However, as small-volume AM deposits undergo self-quenching, the cooling rate can be much faster than in welding. Consequently, the phase transformations in the AM deposit deviate further from equilibrium relative to traditional welding processes, resulting in heterogeneous microstructures and mechanical properties, potentially limiting the direct use of AM components without post-AM heat treatment (Ref. 3). Our prior work with laser-DED (L-DED) hard-facing 420 SS powder without preheat combined experiments, characterization, and kinetic modeling to rationalize the presence of remnant δ-ferrite and austenite quantitatively in room temperature microstructures. This study aimed to quantify the effects of preheating above the Ms temperature on the extent of solidification segregation and microstructures for a wall build for L-DED processing of the same heat of 420 powder. The results of the current work are contrasted with our prior study, which allows for a greater understanding of L-DED opportunities with 420 SS.

Microstructural and mechanical characterization of electron beam welded low-nickel nitrogen-strengthened austenitic stainless steel

In this paper, the Electron Beam Welding (EBW) was used to join thin plates of low-nickel nitrogen-strengthened austenitic stainless steel (LNiASS), a material valued for its superior mechanical properties and cost-effectiveness. Traditional welding techniques often lead to issues such as hot cracking, reduced toughness, and undesirable microstructures. The objective was to address these challenges using EB·W., which offers precise control, minimal heat input, and deeper penetration.Methodology included joining LNiASS plates with E.B.W. and analyzing the resulting microstructures and mechanical properties through optical microscopy, tensile testing, microhardness testing, and scanning electron microscopy (SEM). The findings indicated the presence of various ferrite morphologies without significant precipitation of deleterious phases like carbides and sigma phase. The weldment strength was ∼90 % of the base alloy, with fractures occurring near the weld cord due to nitrogen loss and grain coarsening in the (HAZ). Microhardness increased by ∼12.9 %, attributed to microstructural evolution and a fine-grained structure. Impact testing in Charpy V-Notch (CVN) configuration showed the weld absorbed ∼50 % more impact energy than the base material, due to refined Microstructure and enhanced hardness. Longitudinal residual stress analysis indicated compressive nature below mid-thickness, resulting from thermal expansion and contraction during welding. These results demonstrated E.B·W.'s effectiveness in preserving mechanical properties and enhancing the performance of nitrogen-strengthened stainless steel welds.

Microstructure investigation and optimization of process parameters of ultrasonic welding for Al–Cu dissimilar joints using design of experiment

Ultrasonic Metal Welding (UMW) employs high-power ultrasonic vibrations to join thin metal sheets of different materials, effectively addressing the thermal damage issues associated with traditional welding methods. This study aimed to optimize the joining of thin aluminum (Al) and pure copper (Cu) metal sheets using high-power ultrasonic vibration. The investigation focused on the effect of input parameters, including time, static pressure, and welding power, on the output parameter of joint strength. The results indicated that the welding time had the most significant effect on the load obtained from the Tensile-shear test. The optimal condition was determined to be a welding time of 0.98 s, a pressure of 2 bar, and a power of 85%, resulting in a maximum predicted tensile-shear test load of 753.3 N, with an error value of 11.4% obtained from the software. Microscopic images reveal that the welding mechanism in ultrasonic welding involves continuous plastic deformation, dispersion of oxide layers, and the formation and extension of micro-bonds along the weld line.

Study on the microstructure and properties of spray formed 7055-T76 aluminum alloy joints by rotating magnetic field assisted friction stir welding

This study explores an electrically-magnetically-assisted friction stir welding (EMAFSW) method, conducting butt welding experiments on T76 tempered spray-formed 7055 aluminum alloy. Compared to traditional friction stir welding (FSW) processes, the EMAFSW method maintained basically consistent weld hardness, while tensile strength and elongation increased by 13.1% and 72.3%, respectively. The rotating magnetic field enhanced the mechanical stirring action of the welding tool, reduced the size of precipitates, promoted dislocation pinning, and increased the mobility of dislocations. The stirred zone (SZ) and thermo-mechanically affected zone (TMAZ) of EMAFSW weld joint showed significant grain refinement and increased recrystallization proportion, enhancing the weld joint toughness. The joint's fracture behavior shifted from brittle to ductile fracture.

Influence of pressure and powder characteristics on the properties and microstructure of Colmonoy-5 alloy sintered by spark plasma sintering

This study investigates the microstructure and final properties of Colmonoy-5, a nickel-based hardfacing alloy, consolidated via spark plasma sintering (SPS) as an alternative to traditional welding deposition on stainless steel substrates. Two batches of Colmonoy-5 alloy powders with different particle sizes used for sample processing. Sintering occurred at 900 °C under pressures of either 50 MPa or 60 MPa for 15 min. The evaluation of the sintered samples included density measurement through Archimedes' method, morphology assessment via confocal microscopy, phase composition analysis by X-ray diffraction (XRD), microstructural examination using scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), and hardness testing by Vickers method. Findings indicate that SPS is an effective technique for producing Colmonoy-5, achieving satisfactory densification. The study also reveals that the initial morphology of the precursor powders can influence the size of phases precipitated within the nickel matrix. Sintering pressure of 50 MPa seems to be the most effective in processing Colmonoy-5 via SPS.

Vibration-Assisted Welding of 42CrMo4 Steel: Optimizing Parameters for Improved Properties and Weldability.

This study advances the vibration-assisted welding (VAW) technique for joining medium-carbon, low-alloy steels, which are typically challenging to weld. Traditional welding methods suggest low linear energy and mandatory pre- and post-heating due to these steels' poor weldability. However, VAW employs a vibrating table to maintain part vibration throughout the automatic MIG/MAG welding process. This study tested the VAW technique on 42CrMo4 steel samples, achieving satisfactory weld quality without the need for pre- and post-heating treatments. This research revealed that while vibration frequencies between 550 Hz and 9.5 kHz minimally affect the appearance of the weld joint, the oscillation acceleration has a significant impact. The acceleration along the weld axis (ax), combined with the welding speed and vibration frequency, affects the weld surface's appearance, particularly its scaly texture and size. Lateral acceleration (ay) alters the seam width, whereas vertical acceleration (az) affects penetration depth at the root. Notably, if the effective acceleration (aef) surpasses 40 m/s2, there is a risk of molten metal expulsion from the weld pool or piercing at the joint's base. The quality of the joints was assessed through macroscopic and microscopic structural analyses, micro-hardness tests in the weld zone, and bending trials. The mechanical properties of the VAW samples were found to be acceptable, with hardness slightly exceeding that of the samples subjected to pre- and post-heating. Moreover, the VAW process significantly reduced energy consumption and operational time. The employed vibration system, with a power rating of 100 W, operates for just a few minutes, resulting in substantially lower energy usage compared to the traditional pre- and post-heating method, which typically requires a 5 kW electric furnace.

Evaluating the Microhardness Profiles in Friction Stir Welding of Dissimilar Alloys

Abstract: Friction stir Welding (FSW) advancement is used generally in the utilization of present-day flying and vehicle industry for predominant fundamental mentioning. Such a joining technique is displayed to avoid serious twists and the made excess weights are exhibited as low when it is stood out from the traditional welding structure. In this research, focus on to identify the parameters that will provide the dissimiliar alloys of aluminium AA6061 and AA8011 with good microhardness properties. From the current study microhardness strength of dissimiliar alloys of aluminium varies with the rpm, feed rate and shoulder diameter of the tool. At 2000 rpm and 15mm/min welding speed strength of joints is low and at high rpm 2400 and welding speed 20mm/min micro hardness strength is always low but at a rotation speed of 2200 rpm and welding speed 20 mm/min maximum strength of the weld joint . Hence at high rotational speed rise in the temperature occurs and cause dissolution of precipitates which lowers the hardness and at low rotational speed less heat generation at the tool workpiece interface causing less refinement of grains which lower the hardness value. During tensile strength test fracture and cracks occurs at weld center line.

Experimentally validated numerical prediction of laser welding induced distortions of Al alloy parts for railcar body by inherent strain method combined with thermo-elastic-plastic FE model

A laser welding with wire filler feeding was developed to replace traditional arc welding process for joining aluminium alloy railcar body components. A three-dimensional (3D) thermo-elastic-plastic finite element (FE) model was applied to compute the plastic strains of weld zone in a downsized aluminium alloy plate with butt-joint, T-joint and fillet-joint configurations, respectively, combined with corresponding experimental validations. The achieved plastic strains at the weld zone were then input as inherent strain loadings into elastic structural FE model of fully sized aluminium alloy railcar body components to predict the welding induced distortion with the experimentally measured out-of-plane distortions. The experimentally validated FE model was then further applied for optimizing the inverse pre-deformation of plates to counteract the welding induced deformation, finally to mitigate the welding distortion issues.

Material selection for milling fixture of friction stir welding using simulia

Friction stir welding is an innovative welding technique that joins two different materials without the need for consumables. The process involves a profiled probe and shoulder tool that is rotated and plunged between the two workpieces at the interface during the friction stir process. The weld zone undergoes dynamic recrystallization, resulting in a strong bond between the materials. This method offers superior bonding compared to traditional arc welding. In the context of conventional or non-traditional milling machines, friction stir welding is performed. It is necessary to use a milling fixture to attach the plates that need to be butt and lap welded, fixture can be used in underwater FSW. To ensure the workpiece is securely held in place, a fixture or holder is necessary. In this article, friction-stir welding, and a fixture with a clamping setup are constructed. The fixture is carefully designed to consider the movement of the instrument and workpiece, and it is manufactured using CatiaV6 3D experience software. The fixture is then subjected to three different types of testing using Simulia software. The materials tested include cast iron, die steel, and tool steel. After simulation analysis, the best material for friction-stir welding operations is selected.

Intelligent design of reconfigurable flexible assembly fixture for aircraft panels based on smart composite jig model and knowledge graph

The current demand for aircraft panel assembly fixtures necessitates agile manufacturing solutions. Traditional welding fixtures struggle to meet diverse panel types, high quantities, and short manufacturing cycles. Conversely, reconfigurable flexible assembly fixtures offer universality, efficiency and ease of maintenance but heavily rely on designers' experience, hindering knowledge reuse. Existing research on computer-aided fixture design (CAFD) primarily addresses specialized fixtures, neglecting reconfigurable flexible ones, lacking fixture design knowledge systems. Aiming at the above problems, the study proposes an intelligent design method for the reconfigurable flexible assembly fixture for aircraft panels based on the smart composite jig model (SCJM) and knowledge graph (KG). Firstly, based on the SCJM of the aircraft panel type assembly fixture (PSCJM), a configuration design method is proposed to carry out the multi-level design of reconfigurable assembly fixture to instantiate PSCJM containing fixture configuration rules and a module library based on model definition (MBD). Then, a knowledge retrieval method is proposed to search the suitable fixture design knowledge based on KG, assisting designers in achieving the flexible design of aircraft panel reconfigurable assembly fixtures. Finally, practical engineering design validation confirms the method's feasibility and effectiveness in obtaining the reconfigurable flexible assembly fixture design scheme for aircraft panels.

Characterization of non-steady-stage during friction stir welding

Friction stir welding (FSW) has been widely applied in joining lightweight metals such as aluminum alloys. Similar to traditional arc welding, FSW also experiences a non-steady-stage in the initial stage of welding. Regarding the characteristics of the non-steady-stage during the FSW process, there has been a lack of research by scholars in this area. In this work, the Coupled Eulerian-Lagrangian (CEL) method was employed to perform a numerical simulation of the FSW process. Combined with related experiments, it was discovered that the instability of temperature and axial force leads to the characteristic transition from tunnel defects to void defects during the non-steady-stage. Furthermore, the length of the non-steady-stage was found to be 30 mm, and its duration is influenced by the welding conditions. Tensile tests have confirmed that the welding quality of the remaining part, after removing the keyhole at the weld’s end, is reliable.