Electrode Sticking Research Articles

Micro Resistance Spot Welding Optimization for Ultra-Thin Mo-Re Sheet Used in TWT

<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$30~\mu $ </tex-math></inline-formula> m ultra-thin Mo-Re sheet had been joined by micro resistance spot welding (MRSW) and successfully applied to the low heating power cathode of traveling wave tube (TWT). The effects of different welding parameters, surface state and protection conditions on the joint’s appearance, micro-structure and lap shear strength (LSS) were analyzed in this paper. The results showed that a 63.5 N LSS of the MRSW joint was obtained under the following conditions: electrode force <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$F=9.0$ </tex-math></inline-formula> N, welding current <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$I=1000\text{A}$ </tex-math></inline-formula> , ramping time <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$t_{1}=5$ </tex-math></inline-formula> ms, welding time <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$t_{2}=2$ </tex-math></inline-formula> ms and dip in the alcohol for protection. The fracture occurs in the heat affected zone (HAZ). Using metallurgical microscopy observed the nugget, metallurgical fusion could be found, the diameter of nugget was about <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Phi 0.3$ </tex-math></inline-formula> mm, without gas pores. Scanning electron microscopy (SEM) was used to observe the fracture surface. It could be found some “whisker” shape diverged from the joint center to the surroundings in HAZ. The electrode tip was observed by energy dispersive spectroscopy (EDS) and optical profiler. It was found that the tip was uneven and adhered the base metal obviously after spark. Additional work about electrode sticking will be required. The thermal test data showed that the use of ultra-thin Mo-Re sheet can reduce a space TWT cathode heating power (CHP) by 0.57 W, which will effectively save satellite energy and improve the expected working life of vacuum electronic devices.

Effect of Electrode Patterning on Melting Behavior and Electrode Degradation in Resistance Spot Welding of A6014-T4 Alloy

In this study, the effects of electrode surface design on the resistance spot weldability and degradation of the electrode following resistance spot welding (RSW) of aluminum 6014-T4 alloy were investigated. A new patterning method that can be produced through repetitive pressurization was applied to the electrode, producing a lattice-like pattern shape on the resulting patterned electrode. When RSW was performed using the lattice patterned electrode, the contact resistance decreased because of the effective removal of the oxide film from the surface of the aluminum alloy. As a result, heat generated by resistance on the E/S interface was reduced. Moreover, the growth rate of the weld nuggets formed with the patterned electrode in the thickness direction was lower than that of the nuggets formed with the as-received electrode, and there was comparatively less Cu-Al alloying of the patterned electrode. In addition, a continuous RSW process was performed on the alloy to observe the effect of the electrode surface design on electrode sticking. The results indicated that electrode surface shape can significantly influence resistance heat generation and electrode cooling effects, as well as produce welds with different weld morphology and microstructure. Finally, it was proved that the patterned electrode suffered less electrode degradation through EPMA on the electrode surface after the continuous RSW was completed.

Electrode wear in short-pulse resistance spot welding of aluminum AA 6016-T4

The influence of current pulse width on electrode wear during resistance spot welding of thin sheets (1 mm, 0.04 in) of aluminum alloy 6016-T4 was studied, and an increase in sheet surface roughness and electrode erosion was evident with increasing pulse time for the same weld nugget size. Aluminum alloy 6016-T4 is an especially critical material concerning electrode wear for resistance spot welding due to rapid onset of electrode sticking and erosion of the electrode surface. Typically, welding of this material therefore requires electrode redressing operations after approximately 20 to 30 welds to maintain constant weld size and sheet surface quality. It was demonstrated that a reduction of current pulse width is a means of reducing electrode wear without affecting joint properties. The electrode wear process involved a pickup of aluminum material from the sheets followed by alloying process, leading to formation of intermetallic phases and erosion of material from the surface of the electrodes with increasing number of welds made. A reduction of current pulse width positively affected electrode wear properties by reducing temperatures at the electrode and sheet surfaces, thereby delaying electrode wear and reducing its severity.

Effects of Electrode Face Thickness on Resistance Spot Weldability of Aluminium Alloy 6061

Aluminium alloy sheets are being utilized in automotive parts such as hood, trunk, and tailgate. However, the spot welding of aluminium alloy has many problems, such as electrode sticking and expulsion, and therefore research on the resistance spot welding of aluminium alloy sheets is necessary. In this study, we evaluated the effects of electrode face thickness on the resistance spot weldability of aluminium alloy 6061. The two electrode face thickness conditions were compared, and the electrode face thickness was determined to be an important process variable that affected the spot weldability of aluminium alloy 6061. Key words: Resistance spot welding, Aluminium alloy, Electrode face thickness, Sticking, Expulsion, Radius type electrode

Tailoring micro resistance spot welding parameters for joining nickel tab to inner aluminium casing in a cylindrical lithium ion cell and its influence on the electrochemical performance

In an automotive battery, a large number of individual cells are electrically connected to meet the energy and power requirement. The choice of suitable welding techniques is critical in terms of mechanical strength and electrical contact resistance of the joint. Although soldering, ultrasonic welding and laser welding are the common joining techniques used in lithium-ion cell fabrication, application of resistance spot welding in the manufacturing of lithium-ion battery for electric vehicles is rather limited due to the difficulties in forming large weld nuggets and electrode sticking to the material. In this work, micro resistance spot welding of nickel anode tab to the one side open inner aluminium casing is carried out in an in-house fabricated cylindrical lithium-ion cell. The welding parameters for high electrical conductive nickel-to-aluminium are optimized using the Taguchi design of experiments. The weld joints are assessed by microstructural, mechanical properties and contact resistance characterization. The optimum weld joint shows a well-defined nugget with a shear strength of 338.4 MPa and the electrical contact resistance of 0.052 mΩ. The cell shows high current rate capability and 2 °C increase in the cell temperature at 2C rate. This work paves the way for the application of spot welding technique for tab welding in one side open casing for the manufacturing of lithium-ion cell.

Effects of Surface Roughness and Force of Electrode on Resistance Spot Weldability of Aluminum 6061 Alloy

The effects of electrode surface roughness and force on the resistance spot weldability and sticking of the electrode during resistance spot welding (RSW) of aluminum 6061-T6 alloy were investigated. RSW was carried out using an as-received electrode and an abraded electrode polished with sandpaper, and the nugget size and properties such as tensile shear strength and hardness of the resulting welds were investigated at two different electrode forces. In addition, a continuous RSW process was performed on the alloy to observe the effect of the electrode surface roughness on electrode sticking. When RSW was performed using the abraded electrode, which had a rough surface, the contact resistance decreased because of the effective removal of the oxide film from the surface of the aluminum alloy; consequently, the heat generated by the resistance on the surface was reduced. In addition, the growth rate of the weld nuggets formed with the abraded electrode in the thickness direction was lower than that of the nuggets formed with the as-received electrode, and the sticking of the abraded electrode was comparatively less. Also, the influence of the electrode force on the sticking of the electrode was greater in the case of the as-received electrode.

Sustainably powering wearable electronics solely by biomechanical energy.

Harvesting biomechanical energy is an important route for providing electricity to sustainably drive wearable electronics, which currently still use batteries and therefore need to be charged or replaced/disposed frequently. Here we report an approach that can continuously power wearable electronics only by human motion, realized through a triboelectric nanogenerator (TENG) with optimized materials and structural design. Fabricated by elastomeric materials and a helix inner electrode sticking on a tube with the dielectric layer and outer electrode, the TENG has desirable features including flexibility, stretchability, isotropy, weavability, water-resistance and a high surface charge density of 250 μC m−2. With only the energy extracted from walking or jogging by the TENG that is built in outsoles, wearable electronics such as an electronic watch and fitness tracker can be immediately and continuously powered.

Evolution of joint formation in resistance microwelding of crossed Pt-10%Ir and 316 LVM stainless steel wires

The surface morphology, cross-sections, and joint break force (JBF) of joints welded under different electrode forces were studied. The defects, such as electrode sticking, notch, and excessive expulsions, were observed in the joints. No desirable joints were achieved with the consideration of weld geometries and joint performances. From the cross-sectional morphology, the joint evolution during the RMW of Pt alloy and 316 LVM SS wires was developed, which involved cold collapse and heat promoted set-down of Pt alloy wire, unbalanced heating at interface, molten phase squeezed out, and defect formation. Finally, the defect formation was also discussed.

Resistance microwelding of crossed Pt–10Ir and 316 LVM stainless steel wires

Resistance microwelding of dissimilar materials such as Pt–10Ir and 316 low carbon vacuum melted stainless steel is becoming increasingly important for making electrical connections in medical devices. The joining of dissimilar materials increases flexibility in design while providing economic advantages, where more cost effective materials can be substituted for traditional materials. In this work, the performance of joints made using different electrode forces was studied by examining the surface morphology, cross-sections, joint break force and dynamic resistance measurements from resistance microwelding joints. Electrode sticking and excessive expulsion were observed with low electrode forces, whereas joints with undesirable cracks and notches were produced at higher electrode forces. Based on the analysis of single pulse welds, a new process variation using multiple pulses was developed, which improved the weld surface quality while obtaining a joint strength near 90% of the Pt–10Ir wire tensile strength.

Microelectromechanical switches based on amorphous diamondlike carbon films

We report on the development and investigation of radio frequency (RF) switches (including complete relay pairs) that employ single-crystal microelectromechanical systems (MEMSs) with mobile elements based on high-ohmic amorphous diamondlike carbon films. The use of these films in RF-MEMS switches eliminates problems related to electrode sticking, significantly decreases signal losses (to 100 dB), and ensures short switching times (∼10 ns) for commutated signals at ultrahigh frequencies (up to 2 GHz for films on silicon substrates and above 10 GHz for films on gallium arsenide substrates).

Optimization of resistance spot welding on the assembly of refractory alloy 50Mo–50Re thin sheet

Resistance spot welding (RSW) was employed to pre-join refractory alloy 50Mo–50Re (wt%) sheet with a 0.127mm gage. Five important welding parameters (hold time, electrode, ramp time, weld current and electrode force) were adjusted in an attempt to optimize the welding quality. It was found that increasing the hold time from 50ms to 999ms improved the weld strength. Use of rod-shaped electrodes produced symmetric nugget and enhanced the weld strength. Use of a ramp time of 8ms minimized electrode sticking and molten metal expulsion. The weld strength continuously increased with increasing the weld current up to 1100A, but the probabilities of occurrence of electrode sticking and molten metal expulsion were also increased. Electrode force was increased from 4.44N to 17.8N, in order to reduce the inconsistency of the welding quality. Welding defects including porosities, columnar grains and composition segregation were also studied.

Electrode sticking during micro-resistance welding of thin metal sheets

The electrode sticking mechanism and factors affecting the sticking, including welding current, weld time, electrode tip coating, electrode force and electrode spacing, were studied during micro-resistance welding of very thin nickel-plated steel to nickel sheets in the assembly of a cell-phone battery package. The results indicated that electrode sticking was caused by local metallurgical bonding between the electrode and the nickel-plated steel sheet. The sticking force was proportional to the total area of the local bonds and to the bonding strength between the electrode and sheet. Reducing welding current and weld time, and increasing electrode force and electrode spacing were found to reduce electrode sticking. Welding electrodes with tips coated with TiC metal matrix composite were tried as an alternative to the regular CuCrZr electrode and were found to be more resistant to sticking.

接合部形成現象の検討および接合条件の選定 高電流密度・短時間通電方式スポット溶接の研究 ２

In the high-current density resistance spot welding process, the fusion layer at the interface of the joints is much thinner than one of the conventional spot welding process, the strength of the joints is sufficiently high, and its indentation is very small, and so the contact resistance at the interface is used efficiently to form nugget and the thermal loss is obstructed due to the pulsed high current density with very short duration.As this joining process utilizes the contact resistance at the interface efficiently, the current path is main factor to be determined the joining area. The current path is mainly under the control of the electrode diameter, sheet thickness, electrode force, and current value. For obtaining the joints with sufficiently high strength, the current density in the current path among sheets must be larger than the certain value (2.0 kA/mm2). Furthermore, if the current density at the current path between electrode and sheet is larger than the certain value (2.6 kA/mm2), the electrode sticks on the sheet.Thus, for obtaining the satisfactory joints with sufficiently high strength and without the electrode sticking on the sheet surface, the proper joining conditions exist under certain range of sheet thickness and electrode tip diameter for joining.

交流アーク熔接機のアークドライブの方法

In order to prevent electrode sticking, arc-drive circuits of two types are used in case of an a. c. arc welding machine. They act on the principle that the short circuit between the electrode and the work decreases the reactance of welding transformer, resulting in the increase of short circuit current.Considerations on the ideal characteristics of arc welding machines are also given.