Welding Tip Research Articles

A Feasibility Study for the Hot-Air-Assisted Reflow Soldering Process Based on Computational Fluid Dynamics

In hard disk drive (HDD) manufacturing, a reflow soldering process (RSP) employs heat generated at the welding tip (WT) to bond tiny electrical components for assembling an HDD. Generally, the heat was generated by an electric current applied to the WT. This article reports a feasibility study of using hot air based on computational fluid dynamics (CFD), a choice to assist heat generation. First, the WT and hot air tube (HAT) prototypes were designed and created. The HAT is a device that helps to supply hot air directly to generate heat at the WT. Then, the experiment was established to measure the temperature (T) supplied by the hot air. The measure results were employed to validate the CFD results. Next, the prototype HAT was used to investigate the T generated at the WT by CFD. The comparison revealed that the T measured by the experiment was in the 106.2 °C–133.5 °C range and that the CFD was in the 107.3 °C–136.6 °C range. The maximum error of the CFD results is 2.3% compared to the experimental results, confirming the credibility of the CFD results and methodology. The CFD results revealed that the operating conditions, such as WT, HAT designs, hot air inlet velocity, and inlet temperature, influence the T. Last, examples of suitable operating conditions for using hot air were presented, which confirmed that hot air is a proper choice for a low-temperature RPS.

Ultrasonic complex vibration source equipped with a step horn with a welding tip and its welding characteristics

We have developed a different type of ultrasonic complex vibration source that can generate planar vibrations. The ultrasonic complex vibration source is equipped with a step horn with a hollow part that incorporates a welding chip to improve practicality for industrial applications. The hollow portion in the step horn attached to the ultrasonic complex vibration source enables the adjustment of the longitudinal and torsional vibration amplitude. In this work, we performed finite element method analysis to develop the ultrasonic complex vibration source equipped with a step horn containing a hollow part and a welding tip. The ultrasonic complex vibration source was manufactured and the vibration characteristics and welding properties were measured. The same welding strength was obtained under similar experimental conditions to conventional ultrasonic complex vibration sources. Our results demonstrate that ultrasonic complex vibration sources can be miniaturized and are practically useful.

Influencing mechanisms of weld root tip on microstructure and mechanical properties of electron beam welded joints of titanium alloy thick plates

The welding of titanium alloy thick plates often formed a narrow weld seam in the weld root, named as ‘weld root tip’, because of insufficient fusion, which could reduce the joint properties. In this study, 30 mm-thick Ti-5Al-5Mo-5V-1Cr-1Fe alloy was butt welded via electron beam welding to reveal the influencing mechanisms of the weld root tip on joint microstructure and mechanical properties. The subparallel or parallel weld seam with the weld angles of 0°–3° between the centre line and edge of the fusion zone removed the weld root tip, achieving almost the same mechanical properties with those of the welding zone.

A Development of Welding Tips for the Reflow Soldering Process Based on Multiphysics

A reflow soldering process (RSP) is generally implemented in advanced manufacturing factories for welding small electronic components together to create a product using heat generated at the welding tip (WT). Improper WT design and operating conditions may lead to defects in some products; therefore, optimizing both is immensely significant in developing the RSP. Accordingly, this article proposes a successful RSP development based on multiphysics in a hard disk drive factory consisting of transient thermal-electric and structural simulations. First, a new shape series WT was designed, and a conventional shape, parallel WT, was considered as a case study. Then, they were assembled and experimented with the RSP actual operating conditions to collect essential data. Next, the heat transfer was determined using a transient thermal-electric simulation (TES). The simulation results showed uneven WT temperatures depending on applied voltages, time, and shapes, which were consistent with the experimental results. The higher the applied voltage, the greater the temperature generated at the WT. Finally, after using TES results as loads, the structural simulation showed WT total deformations, which could be consistent with actually occurring defects. The findings from this research are a new design of series WT and proper multiphysics methodology for developing the RSP.

Analysis of fatigue cracking of orthotropic steel decks using XFEM

The cutouts of diaphragms and the weld tips of the U-rib-to-diaphragm connections are the very complex structural details in orthotropic steel decks, and are accordingly highly vulnerable to fatigue cracking. The majority of fatigue cracks in these details appear as a result of the stress concentrations and initial weld defects. To determine the reason for the high probability of occurrence of fatigue cracks at these types of fatigue detail categories, a numerical model was established using the extended finite element method (XFEM) to analyze the cracking of diaphragm of an experimental 1:2 scaled deck segment model. This numerical analysis indicated that the cracks that appear at the diaphragm cutouts and near the weld toes of U-rib-to-diaphragm connections are induced by the relative horizontal displacement between the deck plate and diaphragm along the longitudinal axis of the bridge rather than by vertical deflection or moment due to live load. Additionally, stress concentrations play an important role in the initiation and propagation of cracks in these regions. The contribution of the out-of-plane displacement to fatigue cracking may be the most significant, and can frequently result in crack initiation and propagation prior to any cracking caused by vertical deflection or in-plane stresses. The XFEM approach is a useful numerical method for modelling the fatigue cracking of orthotropic steel decks.

Development of Condition Monitoring System for Electric Resistance Spot Welding Used to Manufacture Railway Car Bodies

Stainless steel railway car bodies are assembled by joining the outer plates and the pillar materials using resistance spot welding. In recent years, more and more car bodies are being assembled using laser welding in addition to the resistance spot welding. For this laser welding system, we developed a condition monitoring system considering the processes before and after laser welding as a single system, and obtained and put into practical use an appropriate condition that suppresses spatter generation during laser welding. On the other hand, in resistance spot welding, the current, weld time, electrode load, and electrode tip shape are the main factors that determine the welding quality. Therefore, the configuration of the equipment is less complicated than that of laser welding system, and the condition monitoring is easier than that of the laser welding. In this study, by transferring the concept of the condition monitoring system developed for laser welding to resistance spot welding, we achieved a reduction of more than 60% in terms of electricity consumption and improved the appearance of the car body by optimizing the indentation shape. In addition to this technical achievement, we also present in this paper a case study showing the opportunity for innovation by restructuring the technological paradigm of the resistance spot welding in the production of stainless steel car body shells.

Welding characteristics of coated twisted wire and copper plate by ultrasonic vibration source using a transmission rod with helical slits

Conventional ultrasonic welding uses one-dimensional linear locus vibrations. However, this method is problematic in that it produces low weld strengths due to low vibration energy. We focus on generating a two-dimensional planar locus by simultaneously driving two orthogonal vibrations. This paper describes our investigation of an ultrasonic vibration source with a welding tip having helical slits capable of producing two-dimensional planar vibration. Using three types of vibration, including the planar vibration produced by this ultrasonic vibration source, we performed welding experiments under varying conditions for static pressure, welding time, and vibration amplitude, and further observed stripping of coating from a coated twisted wire. The results show the superiority of planar vibration over other types of vibration in terms of weld strength and stripping of coating.

Effect of Cd and SPD on structure, physical, mechanical, and operational properties of alloy of Cu-Cr-Zr

Abstract An increase in the service life of electrical products from copper and its alloys is directly related to an increase in the wear resistance of materials. Structural refinement and alloying with cadmium are known to have a positive effect on the strength characteristics and wear resistance of copper, which makes it possible, with a Cd content of 1% by weight, to increase the wear resistance of copper several times, but cadmium is considered an environmentally unsafe element. In this regard, the paper presents the results of studies of a widely used Cu-Cr-Zr alloy system in the ultrafine-grained (UFG) state, micro-alloyed with cadmium (0.2%, weight), in order to improve physical, mechanical, and operational properties, as well as environmental safety. Severe plastic deformation, providing structure refinement to ~150 nm, and microalloying with cadmium of a Cu-Cr-Zr system alloy, after a complete processing cycle, provides a tensile strength of 570±10 MPa and 67% electrical conductivity. At the same time, the abrasion resistance increases by 12 and 35% relative to the industrial systems Cu-Cd and Cu-Cr-Zr, respectively. The obtained characteristics are very promising for improving the operational properties of continuous welding tips, collector plates, and contact wires operating under conditions of intense wear.

RESEARCH OF FACTORS INFLUENCING THE PROCESS OF FORMATION OF WELDED MICROCONNECTIONS IN ELECTRONIC MODULES

The features of the formation of microconnections in electronic modules on an aluminum-polyimide basis by the method of ultrasonic welding, which allows to obtain reliable mounting joints of different thickness aluminum without preliminary removal of oxide films where the use of contact welding and soldering are practically difficult or impossible, are investigated. The influence of technological modes (power of an ultrasonic generator, oscillation amplitude of a welding tip (tool), welding force and welding time) on the reliability of mounting microconnections is considered

Designing of Ultrasonic Horns to Improve Amplitude Uniformity in Ultrasonic Metal Welding

The ultrasonic metal welding has been used extensively in many fields because it can weld thin layers of highly conductive and dissimilar materials with high reliability. In particular, one-wave length horns with four welding tips on both sides of the horn are widely used for welding positive and negative electrodes and tabs of rechargeable lithium ion batteries. As the vibrational amplitude of each tip is known to be non-uniform, this causes some problems in welding performance. In this study, the one-wave length horn which has four welding tips on both sides of the horn is newly designed to improve amplitude uniformity of each tip. The design of experiment technique is employed to determine the optimum configuration of the horn. The modal analysis and harmonic response analysis are repeatedly conducted to obtain the uniform amplitude of horn tips, and stress distribution in the horn is analyzed finally. It is shown that the uniformity of amplitude can be improved by making appropriate grooves on both sides of the conventional horn.

Tip-replaceable Horn with Full Wavelength for Ultrasonic Welding

Ultrasonic welding is faster, environmental friendly, and more efficient than conventional welding. Ultrasonic welding stack, the key part in ultrasonic welding equipment, is composed of transducer, booster, and horn. In the case of ultrasonic welding, wear in the welding tips or breakage of horn occurs because ultrasonic vibration of tips is transmitted directly to the welding material. If grinding of the tips is repeated several times, the mass of horn is reduced and the frequency characteristic is changed. So, there is a limit to refurbishment. In additions, as materials of horn are relatively expensive, some cost problems could be occurred for replacing horns. This study, in order to reduce the manufacturing cost of horn, devised a tip-replaceable ultrasonic horn so that its tip can be easily replaced whenever it is worn. For the designed shape, natural frequency and vibration mode are analyzed using FEA. Through the FEA, the optimal tip-replaceable horn with resonance frequency of 40 kHz is proposed.

Transient Thermal-Electric Simulation and Experiment of Heat Transfer in Welding Tip for Reflow Soldering Process

Welding tip is an appliance for making footprint to connect the arm and head gimbal assembly (HGA) together in reflow soldering process. The welding tip is made from 3 materials: copper alloy, stainless steel, and haynes 230. It works based on Joule heating effect. The haynes 230 head tip is the area used to create a footprint. In the past, failure in the reflow soldering process of a hard disk drive factory was found resulting in defective products; therefore, a solution to resolve this problem must be researched. This article reports a solution to the aforementioned problem by using transient thermal-electric simulation to investigate the heat transfer in the welding tip and a simple experiment to verify the simulation. By using ANSYS, the simulation results revealed the temperature of welding tip. The maximum temperature was 406°C on the head tip at t=0.7s and then it rapidly decreased. The reflow soldering process failure occurred when footprint was done after 0.7s causing the temperature to be too low for melting the solder so the arm and HGA were unable to connect to each other. We proposed simple solutions and ways to improve the efficacy of the reflow soldering process; e.g., footprints should be done at 0.7s, and the welding tip’s material should be changed from haynes 230 to 556. After the factory implemented our results, the problem could truly be resolved. Not only do products have a higher quality but also miscellaneous expenses from defective products are saved.

A Comparative Study on the Effect of Welding Parameters of Austenitic Stainless Steels Using Artificial Neural Network and Taguchi Approaches with ANOVA Analysis

In order to investigate the structure of welds, austenitic stainless steel (SS) studs with a diameter of 6 mm were welded to austenitic SS plates with a thickness of 5 mm using an arc stud welding (ASW) method. The effects of the welding current, welding time, and tip volume of the stud on the microstructure and ultimate tensile strength (UTS) of the welded samples were investigated in detail. The formation of δ-ferrites was detected in the weld zone because of the higher heat generated during the welding process. Higher welding current and time adversely affected the stud and significantly reduced the UTS of the samples. The UTS of the joints was also estimated using artificial neural network (ANN) and Taguchi approaches. The mathematical formulations for these two approaches were given in explicit form. Experimental results showed that the neural network results are more consistent with experimental results than those of the Taguchi method. Overall, it can be concluded that in order to achieve good welding joints and high strength values, ASW parameters should be investigated properly to determine the optimum conditions for each metal.

Analysis of ultrasonic welding process of mild steel and 5052 aluminium alloy

Ultrasonic welding of mild steel sheet (SPCC) and aluminium alloy sheet (A5052) was conducted using two different weld tips of a knurled tip (K-tip) and a curved shape tip without knurled edges (C-tip). Behaviours of the weld tip and the welded materials during the weld process were analysed using a high-speed camera observation and an image correlation. The C-tip welding shows a completely different displacement behaviour from the K-tip welding; a relative motion between the tool tip and A5052 in contact with the tip predominantly occurs in the C-tip in contrast to a relative motion between A5052 and SPCC observed in the K-tip. The joint strength using the C-tip was higher than that using the K-tip under the weld conditions in this study. It is demonstrated that the relative motion behaviour in the C-tip causes a macroscopic deformation of A5052 in the vibration direction. This phenomenon promotes growth of a bonded region, resulting in the increase of joint strength. It is surmised that Fe–Al intermetallic layer forms at the weld interface, and the joint strength consequently decreases for the longer weld time condition.

Ultrasonic metal welding with a vibration source using longitudinal and torsional vibration transducers

Conventional ultrasonic metal welding for joining dissimilar metals uses a linear vibration locus, although this method suffers from problems such as low overall weld strength. Our previous studies have shown that ultrasonic welding with a planar vibration locus improves the weld strength. However, the vibration source in our previous studies had problems in longitudinal-torsional vibration controllability and small welding tip. Therefore, the study of the optimal shape of the vibration locus was difficult. Furthermore, improvement of weld strength cannot be expected. We have developed a new ultrasonic vibration source that can control the longitudinal-torsional vibration and can connect to a large welding tip. In this study, we clarified the longitudinal-torsional vibration controllability of the developed ultrasonic vibration source. Moreover, we clarified that using the planar locus of the developed vibration source produced a higher weld strength than our previous studies, and clarified the optimal shape of the vibration locus.

Study and Applications of Dynamic Resistance Profiles During Resistance Spot Welding of Coated Hot-Stamping Steels

This work compares the role of press hardened steel coating type (Al-Si and GA) on resistance spot welding by analyzing the dynamic resistance curves measured during the weld cycles of the respective materials. It was seen that the dynamic resistance profiles for GA- and Al-Si-coated steels are similar. But the GA specimens exhibited higher resistance than Al-Si-coated specimens in the as-received condition, while the Al-Si-coated specimens exhibited higher resistance after hot stamping. From the early stages of the dynamic resistance profiles, data were obtained and applied for computing the values of components of resistances associated with the different coatings since each coating exhibits characteristic value at the early stages. The results revealed that at the start of the welding cycle, the resistance of the electrode/sheet interface was significantly higher than that of the faying surface or the bulk resistance regardless of whether the steel was Al-Si- or GA-coated. The possible uses of these resistance values in studying welding current requirement and electrode tip life were discussed.

Geomechanical analysis of a welding salt layer and its effects on adjacent sediments

We simulate welding of the source layer of a salt diapir with a forward finite-element model and study stresses and deformation in the salt layer and the diapir, as well as in their adjacent sediments. Welded salt layers are abundant in mature salt basins, where most or all of the salt has withdrawn into diapirs. However, there is little understanding of the stress field in these layers and their adjacent sediments. We show that salt flow along the source layer leads to significant stress anomalies inside the layer and in adjacent sediments. In the source layer, salt pressure becomes higher than overburden stress in nearly welded areas and becomes lower than overburden stress in adjacent thicker areas. When the source layer welds, stresses increase significantly in sediments near the weld tip, which helps compaction of these sediments and possibly their fracturing and faulting. Our model illustrates that all sediments overlying the weld experience this stress increase and the associated material changes as the weld tip propagates along the weld. We present natural examples fitting our predictions and discuss the importance of our results for the exploration, characterization, and production of reservoirs near welded salt layers.

Microstructural and mechanical performance of aluminium to steel high power ultrasonic spot welding

Welding of Aluminium 6111-T4 to bare and two different zinc coated steels was successfully carried out using high power ultrasonic spot welding. The thermal behaviour and non-uniform heat distribution at the local weld area were investigated. The effect of heat generation on precipitates dissolution and natural aging of Al6111-T4 was studied. The maximum hardness in TMAZ was 10-15Hv higher than natural aging which is because of higher rate of precipitation due to reduction in grain/subgrain size. The performance of soft hot-dipped DX56-Z and hard galvannealed DX53-ZF zinc coated steels was discussed in terms of mechanical properties and joinability, in comparison with uncoated steel. The highest peak load (3.25kN) and fracture energy (∼5kNmm) was reached in the case of aluminium to hot dipped DX56-Z zinc coated steel joints owing to the maximum ductility. In contrast, in aluminium to galvannealed DX53-ZF zinc coated steel joints failure was promoted earlier with low mechanical properties of 2.6kN shear strength and 1.25kNmm fracture energy as a result of damage to the zinc layer. Formation of brittle Al–Fe intermetallic layer at the interface of aluminium to bare steel was the main effect of reduction in ∼3.0kN lap shear strength at the maxima. Surface damage due to sonotrode welding tip penetration was seen to be more severe in aluminium to bare DC04 steel compared to other weld combinations that resulted strength loss when the thickness of the weld nugget is reduced at the optimum condition.

New Standard in Scanning of Welding Electrodes by Using Visualization

This article discusses the use of machine optical vision in the control of tip of welding electrodes for resistance spot welding. The aim of the research was carried out to design a fully functioning device for the assessment of immediate functional area of dimensional quality welding tip using the visualization process. The main objective of this work was the proposal of sensing device which satisfies the conditions of functionality, high precision, rapid assessment, reliability, minimum dimensions, production costs and maintenance costs. The launch of the device is the ability to reach a comprehensive solution in production, such as planning the appropriate exchange of tips electrodes, evaluation of area before and after renovation. The output is to ensure a longer lifetime of tips thereby reducing production costs.

Hot spot stress analysis on rib–deck welded joint in orthotropic steel decks

Orthotropic steel decks are used in beams and cable-supported bridges. Fatigue cracks of the vertical rib–deck welded joint have been found in some of the bridges. In this paper, the structural hot spot stress (SHSS) approach is applied to evaluate the rib–deck fatigue. Refined solid models are built using a multi-sub-model technique. Stress around the weld tip is analyzed and effects of the weld profile, the weld toe radius and mesh size are discussed. The SHSS is analyzed using the surface stress extrapolation method, the stress linearization method and the 1mm stress method. Fatigue strength of the joint based on the SHSS is proposed. Results of this study show that the refined multi-sub-model considering the weld detail can reflect the mechanical behavior of the rib–deck joint. Variation of the SHSS by the three methods decreases to less than 10% and a convergent SHSS is achieved using the refined models. The derived fatigue strength for the rib–deck joint using the SHSS of the refined models is close to FAT100. A more precise fatigue strength prediction can be achieved using the refined model while the coarse models result in a conservative design.