Welding is a fabrication or sculpting process that joins metals or thermoplastics. During welding, the workpiece and solder melt to form a molten area (molten pool), which cools and solidifies to form a joint between the materials. This process usually involves the application of pressure. The difference between normal soldering and hard brazing and soft brazing is that soft brazing forms a joint by melting a solder with a lower melting point (lower than the melting point of the workpiece itself), without heating and melting the workpiece itself.
There are many different sources of energy for welding, including gas flames, electric arcs, lasers, electron beams, friction and ultrasound. In addition to being used in factories, welding can be performed in a variety of environments, such as in the field, underwater and in space. Regardless of the location, welding can pose a danger to the operator, so it is important to take appropriate protective measures when performing welding. Possible injuries to the human body from welding include burns, electrocution, visual impairment, inhalation of toxic gases, and excessive exposure to ultraviolet light.
Before the end of the 19th century, the only welding process was the wrought metal welding that blacksmiths had used for centuries. The earliest modern welding techniques appeared at the end of the 19th century, starting with arc and oxy-fuel welding, followed a little later by resistance welding.In the early 20th century, the high demand for military equipment in the First World War and the Second World War led to a focus on inexpensive and reliable metal joining processes, which in turn contributed to the development of welding technology. After the war, several modern welding technologies emerged, including the most popular manual arc welding, as well as automatic or semi-automatic welding technologies such as fusion arc welding, submerged arc welding, flux-cored wire arc welding and electroslag welding. in the second half of the 20th century, the development of welding technology has been rapidly changing, and laser welding and electron beam welding were developed. Today, welding robots are widely used in industrial production. Researchers are still delving into the nature of welding and continue to develop new welding methods and further improve the quality of welding.
Arc welding
Arc welding (Arc welding) uses a welding power source to create and maintain an electric arc between the electrode and the weld material, causing the metal in the weld joint to melt and form a molten pool. They can use direct or alternating current and consumable or non-consumable electrodes. Sometimes some kind of inert or semi-inert gas, known as a shielding gas, is introduced near the molten pool, and sometimes welding filler material is added.
The arc welding process consumes a large amount of electrical energy, which can be supplied by a variety of welding power sources. The most common welding power sources include constant-current power sources and constant-voltage power sources. In the arc welding process, the voltage applied determines the length of the arc, and the current input determines the heat output. Constant current power supply output constant current and fluctuating voltage, mostly used for manual welding, such as manual arc welding and tungsten gas shielded arc welding. Because manual welding requires the current to remain relatively stable, and in practice, it is difficult to ensure that the position of the electrode remains unchanged, the arc length and voltage will also change. Constant voltage power supply output constant voltage and fluctuating current, so commonly used in automatic welding processes, such as fusion electrode gas shielded arc welding, flux cored wire arc welding and submerged arc welding. In these processes, the arc length is kept constant because any fluctuations in the distance between the weld head and the workpiece are compensated for by variations in the current. If, for example, the spacing between the weld head and the workpiece is too close, the current will increase rapidly, causing a sudden increase in heat generation at the weld joint, and the weld head will partially melt until the spacing is restored to its original level.
The type of electricity used has a big impact on welding. Power-consuming welding processes, such as manual arc welding and fusion electrode gas shielded arc welding usually use direct current, the electrode can be connected to the positive or negative pole. In welding, there is a greater concentration of heat in the part connected to the positive electrode, so changing the polarity of the electrode will affect the performance of the weld. If the workpiece is connected to the positive electrode, the workpiece will be hotter and the depth and speed of the weld will be greatly increased. Conversely, if the workpiece is connected to the negative electrode, a shallower weld will be produced. Welding processes that consume less power, such as tungsten gas shielded arc welding, can be powered by either direct current (with any type of joint) or alternating current (AC). However, the electrodes used in these welding processes are such that they only produce an arc and do not provide solder, so when DC is used, a shallow weld is produced when connected to a positive electrode, while a deeper weld is produced when connected to a negative electrode. Alternating current causes a rapid change in the polarity of the electrode, which will produce a weld with a medium degree of penetration. One of the disadvantages of using alternating current is that the arc must be rekindled after each change in voltage passes through the voltage zero point. To solve this problem, some special welding power sources produce a square-wave type of alternating current instead of the usual sinusoidal type, which minimizes the negative effect of the change in voltage as it passes through the zero point.
Shielded metal arc welding
Shielded metal arc welding (SMAW) is the most common welding process. An electric arc is formed by applying a high voltage between the welding material and a consumable electrode, the core portion of which is usually made of steel and covered with a layer of flux. During the welding process, the flux burns to produce carbon dioxide, which protects the weld zone from oxidation and contamination. The electrode core then acts directly as filler material, without the need for additional solder.
This process is very adaptable and requires relatively inexpensive equipment, making it ideal for on-site and outdoor work. Operators can become proficient with minimal training. Welding times are slow because the consumable electrode electrodes must be replaced frequently. It is also necessary to remove the slag formed by the flux after welding. In addition, this technique is usually only used for ferrous metals, and special electrodes are required for metals such as cast iron, nickel, aluminum and copper. It is also often difficult for inexperienced operators to master welding in special positions.
Molten electrode gas shielded arc welding (Gas metal arc welding, GMAW), also known as metal - inert gas welding or MIG welding, is a semi-automatic or automatic welding process. It uses a continuous wire feed of welding rods as the electrode and protects the welded joint with an inert or semi-inert gas mixture. Similar to manual arc welding, it can be mastered by the operator with a little training. Because the wire supply is continuous, fused electrode gas shielded arc welding achieves higher welding speeds than manual arc welding. In addition, because of its smaller arc compared to manual arc welding, FEA is more suitable for special position welding (e.g., back welding).
Compared with manual arc welding, fusion electrode gas-shielded arc welding requires much more complex and expensive equipment, the installation process is also more cumbersome. Therefore, the portability and versatility of fusion arc welding is not good, and because of the need to use shielding gas, is not particularly suitable for outdoor work. However, the high welding speed of FEA welding makes it ideal for large-scale factory welding. The process is suitable for a wide range of metals, both ferrous and non-ferrous.
Another similar technique is flux-cored arc welding (FCAW), which uses similar equipment to FCAW, but employs electrodes with steel electrode cores capped with powder material. The wire is more expensive than standard solid electrodes and produces smoke and slag during welding, but it can be used to achieve higher welding speeds and greater depths of weld.
Gas tungsten arc welding (GTAW), or tungsten-inert gas (TIG) welding (sometimes incorrectly referred to as helium arc welding), is a manual welding process. It uses a non-consumable tungsten electrode, an inert or semi-inert shielding gas, and additional solder. With a stable arc and high weld quality, this process is particularly suitable for welding plate, but it is a demanding process for the operator and has a relatively low welding speed.
Tungsten gas-shielded arc welding is suitable for almost all weldable metals, and is most commonly used for welding stainless steel and light metals. It is often used to weld products that require high weld quality, such as bicycles, airplanes and offshore tools. Similarly, plasma arc welding (PAW) uses a tungsten electrode and plasma gas to generate an electric arc. The arc of plasma arc welding is more concentrated than that of tungsten shielded arc welding, which makes lateral control of the plasma arc welding particularly important, and therefore this technology requires a high level of mechanical systems. Due to its more stabilized current, this method offers greater weld depth and faster welding speeds than tungsten shielded arc welding. It is able to weld almost all metals that can be welded by tungsten gas shielded arc welding, the only one that cannot be welded is magnesium. Automatic welding of stainless steel is an important application of plasma arc welding. A variant of the process is plasma cutting, which is suitable for cutting steel.
Submerged arc welding (SAW), is a highly efficient welding process. The arc in submerged arc welding is generated inside the flux, and the quality of the weld is greatly improved because the flux is shielded from atmospheric influences. Submerged arc welding slag is often self-removing, eliminating the need for slag cleaning. Submerged arc welding can be automated by using an automatic wire feeder, which allows for very high welding speeds. Because the arc is hidden under the flux and produces little fumes, the working environment in submerged arc welding is much better than in other arc welding processes. This process is commonly used in industrial production, especially in the manufacture of large products and pressure vessels. Other arc welding processes include atomic hydrogen welding (Atomic hydrogen welding, AHW), carbon arc welding (Carbon arc welding, CAW), electroslag welding (Electroslag welding, ESW), gas welding (Electrogas welding, EGW), stud welding (Stud welding). Stud welding), etc.
Welding Metal Parts with Oxy-Fuel Gas
The most common gas welding process is Oxy-fuel welding, also known as oxy-acetylene flame welding. It is one of the oldest and most versatile welding processes, but has become less common in industrial production in recent years. It is still widely used in the manufacture and repair of pipes, and is also suitable for the manufacture of certain types of metal artwork. Gasable welding can be used not only for welding iron or steel, but also for brazing, brazing, heating metal (so that it can be bent to shape), and gas flame cutting.
Gas-fired welding requires simple and relatively inexpensive equipment, and is generally accomplished by combusting a mixture of oxygen and acetylene to produce a flame with a temperature of about 3,100 degrees Celsius. Because the flame is more dispersed relative to the arc, gas-capable welding results in a slower cooling of the weld, which can lead to greater stress residue and weld distortion, but this characteristic simplifies welding high-alloy steels. A derivative application is known as gas flame cutting, where a gas flame is used to cut metal[5] . Other gas welding processes are air-acetylene welding, oxy-hydrogen welding, and pneumatic welding, which differ mainly in the use of different fuel gases. Hydrogen-oxygen welding is sometimes used for precision welding of small items, such as jewelry. Gas welding can also be used to weld plastics, generally using heated air to weld plastics, its working temperature is much lower than welding metal.
Resistance welding
Resistance welding (Resistance welding) is based on the principle that when two or more metal surfaces come into contact, there is contact resistance on the contact surfaces. If a high current (1,000-100,000 amperes) is passed through these metals, according to Joule's law, the portion of the metal with the high contact resistance heats up, melting the metal near the point of contact to form a molten pool. In general, resistance welding is an efficient and non-polluting welding process, but its application is limited because of the cost of equipment.
Spot welding machine
Spot welding, or resistance spot welding, is a popular resistance welding process used to join stacked metal plates, which can be up to 3 millimeters thick. Two electrodes deliver a strong electric current to the metal plates while holding them in place. Advantages of this method include higher efficiency in energy utilization, less distortion of the workpiece, faster welding speeds, ease of automated welding, and no need for solder. Due to the significantly lower weld strength of resistance spot welding, this process is only suitable for the manufacture of certain products. It is widely used in the automotive manufacturing industry, with thousands of welding points performed by industrial robots on an average car. A special spot welding process (Shot welding) is available for stainless steel spot welding.
A similar process to spot welding is called seam welding, in which pressure and current are applied through electrodes to join metal sheets. The electrodes used in seam welding are roll-shaped rather than spot-shaped, and the electrodes can be rolled to convey the sheet metal, which allows seam welding to create longer weld seams. In the past, this process was used to make cans, but it is rarely used today. Other resistance welding processes include flash welding, projection welding, and Upset welding.
Energy beam welding
Energy beam welding processes include Laser beam welding (LBW) and Electron beam welding (EBW). They are both relatively new processes that are popular in high-tech manufacturing. The principles of these two processes are similar, with the most significant difference being their energy source. Laser welding uses a highly focused laser beam, while EBW uses an electron beam emitted in a vacuum chamber. Due to the high energy density of both energy beams, energy beam welding has a large depth of fusion and a small weld joint. Both welding processes work very fast, are easily automated and are extremely productive. The main disadvantages are that the equipment is extremely expensive (although prices have been decreasing) and the welds are prone to thermal cracking. A new development in this field is laser-hybrid welding, which combines the advantages of laser welding and arc welding, and therefore enables higher quality welds to be obtained.
Solid-state welding
Similar to the earliest welding processes, forging, some modern welding processes do not require melting the material to form a joint. One of the most popular is ultrasonic welding, which joins sheets and wires made of metal and thermoplastics by applying high-frequency sound waves and pressure. The equipment and principles of ultrasonic welding are similar to resistance welding, except that instead of an electric current, high-frequency vibrations are input. This welding process does not heat the metal to the point of melting, but rather relies on horizontal vibrations and pressure to form the weld. When welding plastics, vertical vibration should be applied at the melting temperature. Ultrasonic welding is commonly used to make electrical interfaces in copper or aluminum, and is also used to weld composite materials.
Another, more common solid-state welding process is Explosion welding, which is based on the principle that materials are joined at high temperatures and pressures created by an explosion. The shock of the explosion causes the material to exhibit plasticity for a short period of time, resulting in a welded joint, with only a small amount of heat being generated in the process. This process is commonly used for welding together different materials, such as joining aluminum parts on a ship's hull or composite panels. Other solid-state welding processes include Co-extrusion welding, Cold welding, Diffusion welding, Friction welding (including Friction stir welding), High frequency welding, and Hot compression welding. High frequency welding), hot pressure welding (Hot pressure welding), induction welding (Induction welding), hot roll welding (Roll welding).
Joint type
Common types of welded joints: (1) I-shaped butt joints; (2) V-shaped butt joints; (3) lap joints; (4) T-shaped joints.
Welded connections between workpieces can have a variety of joint forms. The five basic types of joints are: butt joints, lap joints, angle joints, end joints, and T-joints. There are also a number of joints derived from this form exists, such as double V-shaped butt preparation joint, which is characterized by the two materials to be connected to the chip into a V-shaped sharp angle shape. Single and double U-shaped butt-prepared joints are also common, and their joints are machined into a curved U-shape. Unlike the straight lines of V-joints, lap joints can be used to join more than two pieces of material, depending on the welding process and the thickness of the material, and a single lap joint can be used to weld more than one workpiece.
Often, certain welding processes are unable or almost completely unable to process certain types of joints. For example, lap joints are often used for resistance spot welding, laser welding and electron beam welding. However, some welding processes, such as manual arc welding, can employ virtually any joint type. It is worth noting that some welding processes allow multiple welds to be made: after the weld from one weld has cooled, another weld is made on top of it. This enables thicker workpieces to be welded with V-shaped butt joints.
A cross-section of a welded joint, with the darkest part being the weld zone, or melting zone, the lighter part being the heat-affected zone, and the lightest part being the base material
After the welding is complete, the material in the vicinity of the weld seam displays several distinctly differentiated areas. The weld seam is known as the melting zone, more specifically the area filled with melted flux. The material properties of the melting zone are largely dependent on the flux used and the compatibility of the flux with the base material. Surrounding the melting zone is the heat affected zone (HAZ), where the material in the zone undergoes microstructural and property changes during the welding process, which depend on the properties of the base material in the heated state. The metal in the heat-affected zone tends to perform less well than the base material and the melting zone, and residual stresses are distributed in this region [28].
[edit] Welding quality
The primary measure of weld quality is the strength of the weld joint and its surrounding material. Many factors affect strength, including the welding process, the form of energy injection, the base material, filler material, flux, the form of joint design, and the interactions between these factors. Welding quality is usually checked using either destructive or non-destructive testing, the main objects of which are defects in the welded joint, the degree of residual stress and deformation, and the nature of the heat-affected zone. Welding inspection has a set of norms and standards to guide the operator to use the appropriate welding process and determine the quality of welding.
[edit] Heat-affected zone
The blue portion of the diagram shows the oxidation of the metal caused by the welding process at around 600°C. It is accurate to judge the temperature during soldering by the color, but the color area does not represent the size of the heat affected zone. The true heat affected zone is actually a very narrow area around the weld.
The effect of the welding process on the properties of the metal in the vicinity of the weld can be calibrated, and different welding materials and welding processes can create heat-affected zones of varying sizes and properties. The heat diffusion coefficient of the base material has a great influence on the nature of the heat affected zone: a larger heat diffusion coefficient allows the material to cool faster, forming a relatively small heat affected zone. In contrast, if the heat diffusion coefficient of the material is small and heat dissipation is difficult, the heat affected zone is relatively large. The amount of heat input to the welding process also has a significant effect on the heat-affected zone, such as oxyacetylene welding, because the heat input is not centralized, the formation of a larger heat-affected zone. Processes such as laser welding are able to centralize the output of a limited amount of heat, resulting in a smaller heat-affected zone. The heat-affected zone caused by arc welding, on the other hand, lies between the two extremes, and operator level often determines the size of the heat-affected zone in arc welding [29][30].
The following equation can be used to calculate the heat input of arc welding:
Q = \left(\frac{V \times I \times 60}{S \times 1000} \right) \times \mathit{Efficiency}
The equation Q is the heat input (kJ/mm), V is the voltage (V), and V is the heat input (V). mm), V is the voltage (V), I is the current (A), and S is the welding speed (mm/min).The value of Efficiency depends on the welding process used: 0.75 for manual arc welding, 0.9 for gas-metal arc welding and submerged arc welding, and 0.8 for tungsten gas-shielded arc welding [31].
[edit] Twisting and fracture
As metals are heated to melting temperatures during welding, they shrink as they cool. Shrinkage creates residual stresses and causes distortion in the longitudinal and circumferential directions. Distortion can lead to uncontrolled product shape. To eliminate distortion, sometimes an offset is introduced into the weld to counteract the distortion caused by cooling [32]. Other methods of limiting distortion include clamping the workpiece, but this may lead to an increase in residual stresses in the heat affected zone. Residual stresses can degrade the mechanical properties of the base material and form catastrophic cold cracks. This problem was seen in several free ships built during the Second World War [33] [34]. Cold cracking is only seen in steel materials and it is associated with the formation of martensite as the steel cools, with fracture occurring mostly in the heat affected zone of the parent material. To minimize distortion and residual stresses, the heat input of the weld should be controlled, and welding on individual materials should be done in one pass rather than in multiple passes.
Other types of cracks, such as hot and hardened cracks, can occur in the weld melting zone of all metals. To minimize the occurrence of cracks, metals should be welded without external restraints and with appropriate fluxes [35].
[edit] Weldability
The quality of the weld also depends on the base and filler materials used. Not all metals can be soldered, and different base materials need to be paired with specific fluxes.
[edit] Steel
The weldability of different steel materials is inversely proportional to their inherent hardening properties, which refer to the ability of the steel to produce martensite during cooling after welding. The hardening behavior of steel depends on its chemical composition, and if a piece of steel material contains a high proportion of carbon and other alloying elements, its hardening behavior index is higher, and therefore weldability is relatively low. To compare the weldability of different alloy steels, a method called equivalent carbon content can be used, which reflects the weldability of different alloy steels relative to ordinary carbon steel. For example, chromium and vanadium have a higher influence on weldability than copper and nickel, while the influence factor of these alloying elements is smaller than that of carbon. The higher the equivalent carbon content of an alloy steel, the lower its weldability. If ordinary carbon and low alloy steels are used to achieve high weldability, the strength of the product is relatively low - there is a delicate trade-off between weldability and strength of the product. high strength low alloy steels developed in the 1970's overcame the contradiction between strength and weldability by providing high strength and good weldability at the same time. while also having excellent weldability, making them ideal for welding applications [36].
The analysis of weldability of stainless steel is different from that of other steels because it contains a high percentage of chromium. The austenite in stainless steel has good weldability, but austenite is sensitive to twisting due to its high coefficient of thermal expansion. Some austenitic stainless steel alloys tend to fracture, thus reducing their corrosion resistance. If care is not taken to control ferrite generation during welding, thermal fracture may result. To solve this problem, an additional electrode head can be used to deposit a weld metal containing a small amount of ferrite. Ferritic and martensitic stainless steels also have poor weldability and must be preheated and welded with a special welding electrode [37].
[edit] Aluminum
The weldability of aluminum alloys varies greatly with the alloying elements they contain. Aluminum alloys are highly sensitive to thermal fracture, so high welding speeds and low heat input are usually used in welding. Preheating reduces the temperature gradient in the weld area and thus reduces thermal fracture. However, preheating also reduces the mechanical properties of the base material and cannot be applied while the base material is being fixed. The use of proper joint forms and better compatible filler alloys can reduce the occurrence of thermal fracture. Aluminum alloys should be surface cleaned prior to welding to remove oxides, oils, and loose contaminants. Surface cleaning is very important because when aluminum alloys are welded, excess hydrogen can cause foaming and excess oxygen can form slag [38].
[edit] Welding in extreme environments
Underwater welding
In addition to working in controlled environments such as factories and repair stores, some welding processes can be carried out in a variety of environments, such as outdoors, underwater, and in a vacuum (e.g., space). In outdoor work, such as building construction and repair work, manual arc welding is often used. Welding processes that require shielding gas cannot usually be performed outdoors because the uncontrolled flow of air can lead to weld failure. Manual arc welding can also be used for underwater welding, such as welding ship hulls, underwater pipelines, and offshore work platforms. Other processes more commonly used for underwater welding include flux-cored wire arc welding. Welding in space is also feasible: in 1969, the Soviet cosmonauts for the first time in a vacuum environment to test the manual arc welding, plasma arc welding and electron beam welding. In the decades since then, space welding technology has evolved considerably. Today, researchers are still trying to transfer different welding techniques to be performed in a vacuum, such as laser welding, resistance welding and friction welding. These welding techniques played a great role in the construction of the International Space Station (ISS), where sub-modules of the station built on the ground were able to be assembled and molded in space through vacuum welding techniques [39].
[edit] Protective measures
Welders wear protective helmets, gloves, and suits to perform arc welding operations
Welding without protection is dangerous and unhealthy. The risk of accidents and fatalities during welding can be greatly reduced by adopting new technologies and appropriate protective measures. Commonly used welding techniques often use an open arc or flame, which can easily cause burns. Welders avoid exposing their bodies to high temperatures and flames by wearing additional personal protective equipment, such as rubber gloves and long-sleeved protective jackets. In addition, the intense light in the welding area can cause diseases such as photophthalmitis, as the large amount of ultraviolet light produced during welding can irritate and damage the cornea and retina. When arc welding, it is necessary to wear eye protection goggles or protective helmets. New protective helmets have been developed in recent years that change the transmittance of the goggle lenses in response to the intensity of incident ultraviolet light. In order to protect people close to the welding site other than the welder, the welding work site is often surrounded by a semi-transparent protective screen. These protective curtains, usually plastic curtains made of polyvinyl chloride, protect nearby uninvolved persons from the high-intensity ultraviolet rays generated by the arc, but the protective curtains are not a complete substitute for goggles and helmets [40].
Welders are also at risk from hazardous gases and spatter materials. Welding processes such as flux-cored wire arc welding and manual arc welding produce fumes containing a variety of oxides that can cause occupational diseases such as metal fume fever. Small particles in welding fumes can also affect workers' health; the smaller the particle size, the greater the hazard. In addition, many welding processes produce hazardous gases and fumes, commonly such as carbon dioxide, ozone and heavy metal oxides. These gases can be very hazardous to operators without experience and effective ventilation. It is also worth noting that the shielding gases and raw materials used in many welding processes are flammable and explosive, and appropriate protective measures need to be used, such as controlling the level of oxygen in the air and separating flammable and explosive materials into separate piles [41]. Welding fume extraction equipment is commonly used to evacuate hazardous gases and filter them through high-efficiency compartmentalized air filters.
[edit] Economics and trends
The economic cost of welding is an important influence on its industrial application. Many factors affect the cost of welding, such as equipment, labor, raw materials and energy costs. The cost of welding equipment varies greatly for different processes, from relatively low cost for manual arc welding and gasable welding to high cost for laser and electron beam welding. Due to the high cost of certain welding processes, they are generally only used to manufacture critical components. The equipment costs of automated welding equipment and welding robots are also high, so their use is limited accordingly. Labor costs depend on the speed of welding, the hourly wage and the total working time (including welding and subsequent processing). Raw material costs include the cost of purchasing base metal, weld filler material, and shielding gas. Energy costs, on the other hand, depend on the arc working time and the energy requirements of the weld.
For manual welding, labor costs often account for a large portion of the total cost. Therefore, manual welding costs are often reduced by reducing the time spent on the welding operation, which can be done by increasing the welding speed and optimizing the welding parameters. Slag removal after welding is also a time-consuming and laborious task. Therefore, reducing welding slag can improve safety, environmental friendliness, as well as reduce costs and improve welding quality [42]. Mechanization and automation of operations can also effectively reduce labor costs, but on the other hand increase the cost of equipment and require additional time for equipment installation and commissioning. When there are special demands on the product, the cost of raw materials tends to rise with it. Energy cost, on the other hand, is usually unimportant, as it generally represents only a few percentage points of the total cost [43].
In recent years, in order to reduce the labor costs of welding in high-end products, a large number of automated welding equipment has been used for resistance spot and arc welding in industrial production (especially in the automotive industry). Welding robots can effectively complete the welding, especially spot welding. As technology advances, welding robots are also being used for arc welding. Frontier areas of development in welding technology include: welding between dissimilar materials (such as iron and aluminum parts of the welded joints), new welding processes, such as friction stir welding (friction stir welding), magnetic pulse welding (magnetic pulse welding), conductive heat seam welding (conductive heat seam welding) and laser composite welding (laser welding) ) and laser-hybrid welding. Other research focuses on expanding the applications of existing welding processes, such as laser welding in the aerospace and automotive industries. Researchers also hope to further improve the quality of welds, especially in controlling the microstructure and residual stresses of welds to minimize weld deformation and fracture
.