Weld Spatter Research Articles

Review on Vacuum Laser Beam Welding

Vacuum laser beam welding (VLBW) exhibits better welding characteristics, e.g., deep penetration, less pore, and spatter generation, compared with the conventional laser welding technique under atmospheric pressure. Low ambient pressure affects the vaporization temperature of the base material and the interaction between laser and plasma plume, which affects the behaviors of laser-induced plasma plume, keyhole, and weld pool flow. This review introduces improvements in welding characteristics such as penetration depth, pore, and spatter generation in the VLBW process. The effect of ambient pressure on welding characteristics was reviewed, and the behavior of laser-induced plume, keyhole, and molten pool under reduced ambient pressure was discussed to understand the mechanisms for enhanced weldability.

Influence of Surface Tension and Evaporation on Melt Dynamics of Aluminum Alloys for Laser Powder Bed Fusion

One of the most important factors during Laser Powder Bed Fusion is a robust and stable process to generate reproducibly dense and crack-free components with the same homogenous and fine-grained microstructure. Among other factors, surface tension influences the robustness of this process. Three aluminum alloys were investigated by means of 3D laser printing with respect to their ability to form lightweight and high-performance structures. The alloys include two Al-Cr based alloys (Zicromal®: Al-Cr-Zr-Mn, Scancromal®: Al-Cr-Sc-Zr) and an Al-Mg based alloy (Scalmalloy®: Al-Mg-Sc-Mn-Zr). The surface tensions of their liquid melts were measured by means of the oscillating droplet method in electromagnetic levitation. Scalmalloy® exhibited a surface tension that was by 3-8% smaller than the other two alloys, over a temperature range of 500 K above their liquidus temperature; the evaporation analysis showed that Scancromal® exhibits significantly less evaporation compared to the other two alloys by an order of magnitude. During the Laser Powder Bed Fusion process, Scalmalloy® presented the most unstable melt dynamics, and Scancromal® appeared to be more robust and stable with less weld spatters and negligible dust deposition, as evidence from the high-speed video observations. The results support the idea that surface tension and evaporation are potentially crucial factors influencing the melt dynamics and also demonstrate the capability of additive manufacturing that produces customized aluminum alloys for aerospace applications.

Characterization of keyhole dynamics in laser welding of copper by means of high-speed synchrotron X-ray imaging

Laser welding of copper is of great importance for industrial applications, e.g., for manufacturing of electrical components such as hairpins. Solid state lasers are widely used due to the high power and beam brilliance, but the implementation can be challenging in terms of process instabilities and resulting weld defects, i.e., spatter and pore formation. In order to understand the formation thus avoid these defects, the development of the understanding of the keyhole and its interaction with the surrounding melt pool is required. In this paper, high-speed synchrotron X-ray imaging (frame rate: 20,000 Hz) demonstrated its capability to study the keyhole geometry to quantify and describe the dynamic behavior inside the workpiece. Thus, novel insights into fundamental processes are provided and a new methodic approach was introduced to describe the time-dependent behavior of the keyhole and its interaction with the melt pool during laser beam deep welding of copper (Cu-ETP/CW004A).

Effect of welding parameters on spatter formation in full-penetration laser welding of titanium alloys

The spatter formation process was observed by high-speed imaging during the full-penetration laser welding (FPLW) process of 4 mm-thick TC4 alloy plates. The effects of process parameters on spatter formation were studied. The results showed that the process parameters have obvious effects on the fluid flow characteristics in the melt pool and the dynamic behaviors of metal vapor in the keyhole, which and then affects the spatter behaviors. When using low-power and low-speed parameters, the fluid flow in the melt pool is unstable. When the melt flow impacts the keyhole, the keyhole opening diameter shrinks instantly, resulting in an immediate increase in the metal vapor eruption velocity at the keyhole opening and leading to the formation of weld spatter with a small size and high flying speed. When using high-power and high-speed parameters, a large amount of metal vapor erupts at high velocity from the keyhole opening transiently, resulting in the formation of a higher liquid column on the keyhole wall. The liquid column fractures to form weld spatter with a large size and low flying speed. When the pressure of the metal vapor in the keyhole is too large, the surface tension of the liquid metal under the keyhole cannot withstand it, causing an explosion on the backside of the melt pool. During the explosion, a large amount of spatter and plasma is ejected from the keyhole exit, and the plasma plume above the melt pool is weakened.

용접 불티 포집기의 흡입 조건에 따른 포집효율 상관관계 분석

This research was conducted to analyze the collection efficiency of the welding spatter collecting device used for the reduction of fire accidents accompanied by welding work. The welding spatter collection device suggested in this study was mainly consisted of suction blower fan and collecting filter. The suction velocity and the mass of welding spatter collected by the device were measured for three types of filter porosity and three different blower powers. The relationship between collection efficiency and suction conditions was derived from the theoretical approach and the empirical model constants were determined by analysis of measuring data. The results showed that at the given blower power, the increase in pore size and rate of filter increased the suction force and the spatter collection efficiency.

Comparative Experimental Analysis of Temperature Distribution in Mini Size Permeable and Non-Permeable Varying Salt Density Solar Pond

Varying salt density solar pond is a method that is best suited to absorb and store solar energy. This examination includes the test enhancement of the permeable and non-permeable sunlight-based ponds dependent on its exhibition in different conditions. This experiment was done in Salem, Tamil Nadu, India. This particular topographical area has a high level of solar radiation and is a tropical district. Readings for a period of 30 days were taken; the temperature circulation, a measure of heat energy stored and concentration of salt density was assessed. For examination, two comparable solar ponds of volume 0.02 m3 and a height of 0.32 m was built. Black granite pieces, broken glass pieces, and welding spatter were used as a permeable medium in the lower convective zone (LCZ) in one of the two solar ponds. The temperatures of the permeable solar pond and non-permeable solar pond reached the highest values of 42.3℃ and 40.6℃ respectively. The solar pond with a permeable medium demonstrated an increase of 4.18% in temperature. The difference in amounts of stored thermal energy is 4.54 kJ. From the obtained parameters, the optimization is done and the permeable medium solar pond is found to store more amount of heat energy than the non- permeable solar pond. For the optimization of the mixed medium, criterion parameter βelk has been acquired in the solar pond.

3D Numerical Study of External Axial Magnetic Field-Controlled High-Current GMAW Metal Transfer Behavior

For gas metal arc welding (GMAW), increasing the welding current is the most effective way to improve welding efficiency. However, much higher current decreases the welding quality as a result of metal rotating-spray transfer phenomena in the high-current GMAW process. In this work, the external axial magnetic field (EAMF) was applied to the high-current GMAW process to control the metal transfer and decrease the welding spatters. A unified arc-droplet coupled model for high-current GMAW using EAMFs was built to investigate the metal rotating-spray transfer behavior. The temperature fields, flow fields in the arc, and droplet were revealed. Considering all the heat transferred to the molten metal, the Joule heat was found to be the dominant factor affecting the droplet temperature rise, followed by the anode heat. The conductive heat from the arc contributed less than half the value of the other two. Considering the EAMFs of different alternating frequencies, the arc constricting effects and controlled metal transfer behaviors are discussed. The calculated results agree well with the experimental high-speed camera observations.

Effects of Welding Time and Electrical Power on Thermal Characteristics of Welding Spatter for Fire Risk Analysis

To predict the fire risk of spatter generated during shielded metal arc welding, the thermal characteristics of welding spatter were analyzed according to different welding times and electrical powers supplied to the electrode. An experimental apparatus for controlling the contact angle between the electrode and base metal as well as the feed rate was prepared. Moreover, the correlations among the volume, maximum diameter, scattering velocity, maximum number, and maximum temperature of the welding spatter were derived using welding power from 984–2067 W and welding times of 30 s, 50 s, and 70 s. It was found that the volume, maximum diameter, and maximum number of welding spatters increased proportionally as the welding time and electrical power increased, but the scattering velocity decreased as the particle diameter increased regardless of the welding time and electrical power. When the measured maximum temperature of the welding spatter was compared with an empirical formula, the accuracy of the results was confirmed to be within ±7% of the experimental constant C=112.414×Pe−0.5045. Results of this study indicate quantitatively predicting the thermal characteristics of welding spatter is possible for minimizing the risk of fire spread when the electrode type and welding power is known.

연속 은닉 마르코프 모델을 이용한 GMA 용접품질 실시간 모니터링에 관한 연구

Welding technology is a fundamental basis that determines the performance and life of nuclear power plants. The piping is more complicated than normal industrial plants and has more welded parts. It is necessary to have overall technical capabilities ranging from design, manufacturing, and construction to cultivate a competitive foreign nuclear industry. As the power generation equipment manufacturing part consists of welding more than half of the whole process, welding technology has an absolute influence on enhancing competitiveness. In particular, high-performance materials and higher-level welding techniques are required to prevent corrosion defects, etc., occurring in the use of equipment. When manufacturing nuclear power plants of nuclear reactor pressure vessels and piping systems, welding techniques in which welding defects are extremely reduced are required. In this paper, a prediction model to determine the correlation between welding parameters and spatter in the GMA welding process is developed and verified. Based on model using the CHMM of machine learning, a model is developed to predict the defects using correlation analysis of process variables and spatters. To verify the reliability of the developed defect prediction model, the welding spatter obtained from the actual welding experiment and the prediction model are compared and analyzed, and the accuracy is evaluated.

Analysis of the Thermal Characteristics of Welding Spatters in SMAW Using Simplified Model in Fire Technology

In this study, the thermal characteristics of welding spatters were analyzed to predict the risk of fire spread in the shield metal arc welding. The mean diameters and the distribution shapes of the particles were investigated with the variation of the distribution coefficients using the modified gamma distribution function. To quantify the heat source of the welding spatters, the previous empirical equation for the heat transfer coefficient of Ranz and Marshall was analyzed regarding the particle velocity and surface temperature. The order of magnitude for the convection and the radiation were as performed to the particles and the base metal, respectively. The results, which are only valid for Tp,m = 750 K and Tb,s = 2300 K, show that the radiation term is only 10% for a particle but the convective term is only 6% for the base metal. Finally, the simplified model for the temperature of the welding spatters was obtained and the validation results were within ±13%. The variations of electrical power, droplet size, number of particles, and surface temperature were systematically analyzed with the prediction model. The importance of safety conditions to prevent the fires spread by welding spatter was suggested with electrical power, particle velocity, and numerical density of the particles.

Effects of Reduced Ambient Pressure and Beam Oscillation on Gap Bridging Ability during Solid-State Laser Beam Welding

In recent decades, beam welding processes have been set up as a key technology for joining applications in automotive engineering and particularly in gearbox manufacturing. Due to their high beam quality, energy efficiency, reliability as well as flexible beam guidance, modern solid-state lasers offer numerous advantages, but also pose increased requirements on the production and positional accuracy of the components for the joining process. In particular, small-focus diameters present a challenge for components with process-induced tolerances, i.e., disc carriers in automatic transitions. Furthermore, welding processes utilizing solid-state lasers show an increased spatter formation during welding at high welding speeds. Accordingly, the primary objective of the presented work consists in extending the current areas of application for solid-state laser beam welding in gearbox manufacturing through an improved process reliability regarding tolerance compensation and spatter formation. Therefore, this experimental study aimed to describe the effects of a dynamic beam oscillation in combination with a reduced ambient pressure in the process environment on both gap bridging ability and spatter formation during the laser beam welding of case hardening steel. For basic process evaluations, laser beam welding at reduced ambient pressure and laser beam welding with dynamic beam oscillation were initially studied separately. Following a basic process evaluation, samples for 2 mm full-penetration-welds with varying gap sizes were analyzed in terms of weld seam geometry and weld spatter formation.

STUDY OF THE OPERATING TIME OF THE PROTECTIVE COATING OF SURFACES OF ASSEMBLY AND WELDING EQUIPMENT

The subject of the study is the issues related to determining the service life of protective coatings protecting the surfaces of assembly and welding fixtures from the effects of welding spatter and mechanical wear when performing certain assembly and welding operations of welded metal structures. The development in Ukraine of various industries, especially the precision engineering industry (instrument making), is characterized by a transition to market management methods, increasing demand for competitive and liquid products. This can be achieved by the systematic and rapid introduction of technically new products, improving their quality, increasing labor productivity, and automating production. Welded metal structures are widely used in the designs of modernized and new types of products, the high-quality production of which is impossible without the use of assembly and welding equipment. The reliability and durability of these devices depends on the protection of their surfaces to the effects of welding spatter and scoring during assembly and welding operations. Analytical and experimental studies of the resistance of protective coatings to an experimental welding drop of metal showed that of the most tested coatings, the most durable is the developed protective coating containing a mixture of molybdenum disulfide powder, graphite powder, epoxy varnish and certain solvents. Purpose: determination of the service life of the developed protective coating when exposed to a number of significant factors, including the effects of real welding spatter. Tasks: to identify the main - significant technological factors affecting the service life of the protective coating; develop a planning matrix based on a full factorial experiment; to conduct experimental studies of the resistance of the coating to the effect of an experimental metal drop under the influence of significant technological factors, to obtain the equations of regression of resistance; conduct analytical and experimental studies to determine the temperature of the experimental drop of molten metal; conduct analytical studies of the temperature of a real welding spray; conduct a study of the resistance to friction; conduct analytical studies to determine the quantitative characteristics of the reliability and durability of the proposed coating composition. Results: the article presents the research data by the authors of the service life of the proposed protective coating that protects the surfaces of assembly and welding fixtures when exposed to welding spatter and coating wear when moving metal structures in the fixture. The quantitative characteristics of the reliability and durability of the coating are obtained. Conclusions: A methodology has been developed for determining the service life of protective coatings protecting the surfaces of assembly and welding fixtures from the effects of welding spatter during welding operations and coating wear when moving elements of the welding structure in the fixture during assembly.

Behavior and stability of droplet transfer under laser-MIG hybrid welding with synchronized pulse modulations

In order to explore the synergetic effect on the process combination of pulsed laser and pulsed MIG hybrid welding, two kinds of coupling modes were performed by modulating the laser power to synchronize the arc current. The results showed that under the in-phase coupling mode, the addition of a high power laser during the peak period of the arc current increased the formation and separation time of the droplet and resulted in the deviation of droplet from the wire axis. This caused the droplet to be easily hit by the laser beam and reduced the stability of the droplet transfer. Moreover, the enlarged laser-induced plasma led to a significant loss of the laser energy. In contrast, under the anti-phase coupling mode, the application of a low power laser during the period of the highest arc current suppressed the arc length becoming longer and resulted in faster droplet separation, fewer weld spatters and smoother droplet transfer. At the same time, compared with the weld of in-phase laser-MIG hybrid welding, the weld of anti-phase laser-MIG hybrid welding had the advantages of deeper penetration, fewer weld spatters, less porosity and better tensile properties.

Experimental research on formation mechanism of porosity in magnetic field assisted laser welding of steel

The dynamic keyhole behaviors are directly observed in laser welding of AH36 steel/glass, and Zirconia particle is used to observe the convective pattern. The weld bead formation, keyhole instability and porosity formation are analyzed. Moreover, the differences in keyhole instability and porosity formation between no magnetic field assisted and magnetic field assisted laser welding are analyzed. With the magnetic field is added, the weld width, small concave, the formation of the keyhole collapse and the convective pattern are similar in laser welding of steel, and the generated Lorentz force hinders the flow of liquid metal. Widening of bottom weld width without undercut defect can be obtained with magnetic field assisted. The lower fluctuation of the weld depth, the longer time of plasma plume above the weld pool, fewer undercuts and spatter defects contributes to the increase of the keyhole stability, and thus restrains the porosity formation. Besides, an easier keyhole open, the larger bubble escape velocity and the lower solidification rate also promote the reduction of the porosity formation.

Effect of Process Parameters on Weld Spatter in Robotic Welding

This research deals with the investigation of a real-life industrial problem of excessive weld spatter produced in an automated welding robot cell using gas metal arc welding process. Spatter generation was attributed to a number of sources including incorrect machine settings, surface contaminants, and erratic wire feeding. Random variation of different welding process parameters such as voltage, wire feed speed, and torch travel angle, affected spatter production, which served as a motivation to embark on a systematic study involving design of experiments. A total of ten most significant parameters were identified through a brainstorming process involving robotic cell operators, section managers, and subject matter experts. Using the selected ten parameters, preliminary experiments were conducted to determine the appropriate operating range for each process parameter that has the most significant impact on weld spatter. An Orthogonal L16 Array from Taguchi’s designs was chosen with four parameters at 4-levels, four parameters at 2-levels, and two parameters were held constant at 1-level. Following the establishment of a defined set of parameters and corresponding ranges of values, a series of designed experiments were conducted to measure the effect of process parameters on weld spatter production. During each designed experiment, six different responses were recorded that included, the weight of wire used, the weight of the weld bead deposited, the mass of spatter collected in a tray, audio signals generated, the spatter particle count using ImageJ, and the quality of the weld bead. The optimal process parameters identified in this study were of practical significance, and as such the recommended parameters were implemented in the industry.

The method for determining the amount of interference formed during the assembly of the rim and disk of the wheel of automobile and tractor

The disk-rim system is a complex structure with a variety of properties that have not yet been fully studied. The vehicle wheel is an axisymmetric structure consisting of a rim and a disk for attaching it to the hub. On the one hand, the outer diameter of the disk (flange) is welded around the circumference to the inner diameter of the rim (shelf), forming a rigid one-piece connection. On the other hand, using a bolted connection, the disk is attached to the hub, forming a wheel-hub assembly. The assembly line of the rim and wheel disk of a truck consists of the following technological operations: pressing the disk into the rim, welding the outer seam, welding the inner seam, cleaning the surface from welding spatter, punching the valve hole, curing burrs on the valve hole, and controlling the runout. When pressing the disk into the rim, it is necessary to know the amount of interference, as well as the distribution of radial and tangential stresses. Determining the amount of interference is an urgent task, since this characteristic is fundamental when assembling the rim and wheel disc. It was found that for radial stresses the compression is observed. Its largest value is located at the boundary of the disk and the rim. For tangential stresses the tension is observed. Its largest value is located at the boundary of the disk and the rim. Calculations showed that for a 400 mm wheel disk, a 300 mm wheel rim an elastic modulus is 2∙104 MPa, a force modulus is 600 MPa, an interference fit is 0,0865 mm.

On Heat Treatment and Surface Characterization of Spark Eroded Nickel-Based Superalloy Developed by Additive Manufacturing

In this study, a nickel-based superalloy Inconel 718 material was developed through direct metal laser sintering process. To enhance the mechanical properties, printed material was heat-treated at two different conditions in the combination of solution and ageing. The transformations of microstructure from original anisotropic phase were studied using optical microscope. The changes in mechanical properties were evaluated. The hardness of the heat-treated samples obtained is 35HRC and 39HRC for the heat treatment plan at 1100 °C + 845 °C and 980 °C + 720 °C (solution + ageing), respectively. Further, micro-holes were machined on these two material samples using spark erosion micro-machining or micro-electric discharge machining (µEDM) process. Applied voltage, capacitance and material hardness were three major variable parameters. Experiments were performed with hollow tungsten carbide rod of 300 µm in diameter as a drill tool rotating at a speed of 1500 rpm for a constant machining time of 30 min. Optical and scanning electron micrographs were used to analyse the hole quality and therefore the performance of µEDM. Perfect concentric drill hole was produced with 35HRC sample than the other. Weld spatters and metal drops were found around the surface of 39HRC sample. The range of drill hole varied to a maximum of ϕ385 µm in low-hardness and ϕ400 µm in high-hardness samples. The depth of drill hole was maximum with high hard sample at 100 V and 100 nF process condition. Light spectroscope-based roughness characterization revealed that the minimum surface roughness measured was 6.946 µm in low hard and 9.829 µm in high hard material.

Effect of Parameters Change on the Weld Appearance in Stainless Steel Underwater Wet Welding with Flux-Cored Wire

The underwater wet welding (UWW) technology is rapidly developing as a crucial method in the maintenance work of marine equipment and offshore platform. The rapid development of UWW technology has also exposed the problems to be solved urgently. Therefore, the influence of welding parameters on the weld appearance and welding spatters was investigated in this paper. The main welding parameters used in the study are welding current, arc voltage, welding speed and the contact tip-to-work distance (CTWD). Through the orthogonal test, it is found that, as each welding parameter increases within a certain range, the amounts of welding spatter decreases first and then increases, and the weld forming effect first becomes better and then deteriorates. The amount of wet welding spatter is mainly affected by the welding speed. When the welding speed is low, the splash is more, and the change of the welding current and the arc voltage has a little effect on the number of spatters. When the welding speed is large, the spatter is most with a small welding current and a large arc voltage. After evaluating the weld morphology obtained by welding under various parameters, a set of optimal parameters was obtained. The best parameters for the underwater wet welding of stainless steel with self-shielded flux-cored wire are determined to be 200 A-29 V-2.0 mm/s-15 mm (CTWD).

A Study on Spatter Tracking Algorithm for a Vertical GMA Welding Process

GMA (Gas Metal Arc) welding has the advantage of no slag formation and is becoming the most suitable technology for automated welding. Recently, robot welding and machine welding have been replaced by GMA welding. However, welding spatter has always been a problem with GMA welding, especially GMA welding using CO2 gas as a shielding gas. Therefore, it is necessary to minimize the occurrence of spatter. In this paper, the spatter generation process was analyzed and the amount of generated spatters was minimized by controlling the unstable waveform of the current. In addition, we developed a spatter tracking algorithm to confirm the effect of spatter reduction. Key words: Gas metal arc, Spatter, Spatter tracking algorithm, Welding automation

Optimization of magnetic oscillation system and microstructural characteristics in arc welding of Al/Mg alloys

AZ31B magnesium alloy and 6061 aluminum alloy were welded by the longitudinal magnetic field hybrid cold metal transfer (CMT) welding process. Three magnetic pole structures were designed and the distributions of magnetic field were simulated. The results show that the platform-shaped magnetic pole structure can improve the longitudinal direction of magnetic field in weld zone, which was suitable to redistribute welding heat source and decrease welding spatters. With the applied magnetic oscillation the welding width increased, the welding penetration and wetting angle decreased, meaning the wetting behavior of molten metal improved. The welding pores in the weld zone were suppressed with the increase of coil currents. The magnetic oscillation obviously reduced the thickness of Mg2Al3 layer and dispersed the distribution of strengthening phases Mg2Si that can prevent the crack propagation. The microhardness value at the interface layer was increased and the shear strength of the Al/Mg joints reached a maximum of 1411 N with magnetic oscillation, increasing by 30% compared to the normal welded joint. Fracture of the Al/Mg lap joints occurred at the Mg2Al3 layer/weld interface and Al side around the fusion line.