Resistance Welding Technology: A Survey of International Developments
Abstract
The aim of this paper is to provide an overview of the state of the art in resistance welding technology, both in terms of material technology and the techniques and processes used in the industry. The paper reviews the various types of resistance welding processes and materials, including spot-, seam-, and projection welding. Different types of welding machines and the welding process parameters that influence the weld quality are outlined. Furthermore, recent developments in welding machines and welding process technologies are discussed. Finally, some of the challenges faced by the resistance welding industry and recent developments in fault detection and modeling of the welding process are discussed.
1. Introduction
Resistance welding is a well-established joining process for metals, combining the use of heat along with pressure to join the materials. This process is well-suited for mass production and is used in various industries such as aerospace, automotive, and electronics manufacturing. Due to its versatile nature, the resistance welding activity is present in almost every major manufacturing facility in the world.
Resistance welding can be used to join both similar and dissimilar metals. It is used for applications ranging from sheet metal assemblies to precision stainless steel welding. The welds can be of highest quality if the welding parameters are chosen correctly. The development of sophisticated welding machines and welding parameters has made possible the relatively high welding speed that is required in mass production.
2. Resistance Welding Processes
Several types of resistance welding processes are commonly used to join metals. These processes are generally defined by the shape of the material joint, which can be a spot, seam, or an overlap joint.
In spot welding, two (or more) metal pieces are joined at specific points with electrical energy. The electrical energy is pulsed through the parts and causes an intense heat, thereby welding the pieces together. Some of the most common materials for spot welding include mild steel, copper alloys, and stainless steel.
Seam welding is also known as butt welding, and is used to join two overlapping pieces of metal along their adjoining edges. Seam welding is used for similar applications as spot welding, and is used for making lap and Tee joints.
In projection welding, the two pieces of metal are mechanically held together and then resistance heated at the intersection of two or more projections. The process is used to join hard alloys, aluminum alloys, and stainless steels.
3. Welding Machines
The type of welding machine used to join metals is an important factor in determining the quality of the weld. The majority of welding machines use a type of transformer, which is designed to deliver extreme levels of heat and pressure. This transformer is usually driven by a combination of an AC and DC current.
The transformer usually contains an induction coil, which is used to generate the necessary heat for welding. The electricity is then passed through the coil in order to create a strong electromagnetic field, which is sufficient to cause the desired welding process. The amount of electricity used is determined by the welding parameters, such as voltage, amperage, frequency, and pulse duration.
The welding machine also contains a set of electrodes, which are used to hold the work pieces in place during the welding process. Different types of electrodes are available, and the selection of the electrode depends on the application.
4. Welding Parameters
The weld quality can be improved by adjusting the welding parameters. The welding parameters are chosen based on the welding process, materials, and the size and shape of the parts to be joined. The most commonly adjusted parameters include voltage, amperage, frequency, and pulse duration.
Voltage- The voltage is the most important parameter, and it is determined by the thickness of the pieces to be welded. Lower voltage is used when welding thinner sheets, while higher voltage is used when welding thicker parts.
Amperage- The amperage determines the amount of heat generated during the welding process. The amperage is usually adjusted in order to obtain the desired welding speed.
Frequency- The frequency is determined by the amount of energy required for the welding process. The higher the frequency, the higher the energy required.
Pulse Duration- The pulse duration determines the length of time the welding current is applied to the work pieces. It is generally selected to achieve a good weld quality.
5. Developments
In recent years, there have been several developments in welding machines and welding process technologies.
The use of water-cooled welding heads has enabled welding at higher speeds, with improved heat dissipation as compared to air-cooled welding heads.
The development of microprocessor-controlled welding machines has allowed precise feedback and control of the welding process. It has also enabled automatic welding setups, which improve the quality and consistency of the welds.
In addition, the introduction of laser welding has replaced the traditional resistance welding processes in some areas. Laser welding is more precise and faster than traditional welding processes, and can be used for precise welds in complex components.
6. Challenges
In addition to cost considerations, the resistance welding industry faces several challenges that need to be addressed. These include:
Lack of knowledge- The process of resistance welding is quite complex and requires an in-depth knowledge of welding parameters and welding machines. The welding industry needs to improve the level of training and knowledge among its workers.
Inconsistent weld quality- Controlling the weld parameters to obtain good welds is a continuous process, and welds that are produced with even small variations can have significant differences in the final product.
Fault detection- There is a need for new technologies that can quickly detect weld defects and help to assess the quality of the weldment.
7. Conclusion
In conclusion, resistance welding technology has advanced significantly over the last few decades. This paper has provided an overview of the types of resistance welding processes, machines and materials, and welding parameters that are used in the industry. Furthermore, recent developments in welding machines and welding process technologies have enabled higher efficiency and improved weld quality. Finally, some of the challenges faced by the resistance welding industry have been discussed, as well as recent developments in fault detection and modeling of the welding process.
