Laser-Assisted Friction Stir Welding (LAFSW) Technology
Abstract
Laser-assisted friction stir welding (LAFSW) is a novel welding technique developed by combining friction stir welding and laser welding. The technique applies a laser beam to the peaks of the stir pins and intense heat input to the fuse the materials around the pins, then stirs using an external force to create the desired weld. With advantages of better process quality, high joint strength, fast welding speed and more versatility than fusion welding, the LAFSW technology has increasingly gained scrutiny from both industry and academia, and applications have been expanding rapidly. This paper summarises the theory, characteristics and applications of the LAFSW technology.
1. Introduction
Laser-assisted friction stir welding (LAFSW) is a novel welding technique developed by building on traditional friction stir welding (FSW). LAFSW is an efficient metal welding process that is capable of producing welds with better process quality, high joint strength, fast welding speed and increased versatility compared to traditional fusion welding technologies.
In traditional FSW, a cylindrical tool with a specially designed stir pin connected to its end is inserted into the joint to be welded and driven into the two materials by a machine. As the stir pin is pushed into the workpieces, it causes frictional heat to be generated at the contact zone between the circumferential shoulder and the workpieces due to the plastic deformation of the materials. This heat softens the materials and makes them easier to be welded together.
In conventional FSW, the stirred material is joined together by the frictional heat from the stirring tool without any external heat input. The process is limited in terms of the type of material, thickness or configuration. The introduction of laser energy in the LAFSW process provides an additional heat source which increases the melting temperature of the weld material and increases the initial plastic deformation of the welding zone. This allows the FSW process to be used on a much wider variety of materials, including those with higher strength and hardness, as well as wider widths and thicknesses.
2. Theory of LAFSW
In the Laser-assisted friction stir welding process, a laser beam is applied to the peaks of the stir pins as the FSW tool is inserted into the joint. As the stir pin is driven into the joint, the laser beam melts the peak of stir pins, resulting in intense heat input to the materials. This heat is then distributed to the local area due to the stirring action of the pin. The melted material around the stir pins is pushed to the side of the joint, forming the weld seam.
At the same time, the external force used to drive the pin is applied to the weld zone, causing frictional forces to arise. This additional frictional heat softens the stirred materials and facilitates their fusion. The stirred material can also be further melted by the laser energy, as well as undergoes a plastic deformation as it is stirred, resulting in a stronger joint. The end result of the process produces welds with better process quality, high joint strength, fast welding speed and increased versatility compared to traditional fusion welding technologies.
3. Characteristics and Advantages of LAFSW
The LAFSW process has several benefits over traditional welding technologies. The welding process can be performed without filler materials, as the stir process takes place in the area around the piercing point, resulting in an environmentally friendly and cost-effective process. Moreover, the joint strength achieved by LAFSW is superior to conventional welding. The process provides flexibility for welding a variety of materials with different widths, thicknesses and configurations.
Other advantages of the LAFSW process include higher heating, low distortion, more accurate joining, improved metallurgical properties, improved fatigue resistance and superior appearance. The welding process can be used on materials such as aluminum, titanium, steel and nickel alloys, and is suitable for applications in aerospace, automotive, energy and shipbuilding industries.
4. Application of LAFSW
Due to its benefits, the LAFSW process has found applications in several industries. In the aerospace industry, laser-assisted FSW has been used to weld titanium components such as the titanium turbine blades and tip assemblies of airplane engines. The process has also been applied to the welding of aluminum automobile bodies and frames.
In energy generation, LAFSW can be used in the welding of nuclear and coal-fired power plants. The process has been applied to the welding of steel pipelines, boiler tubes and other components in the oil and gas industry.
In the shipbuilding industry, LAFSW has been used in the construction of large ships to weld structural steel and galvanized steel plates. The process has also been employed in the welding of aluminum and titanium components.
5. Conclusion
In conclusion, Laser-assisted friction stir welding (LAFSW) is a novel welding technique combining friction stir welding and laser welding. The process has several advantages including better process quality, high joint strength, fast welding speed and more versatility than traditional fusion welding, which has made it increasingly popular in industry and academia. The process has already been applied in various industries such as aerospace, energy, and shipbuilding.
The LAFSW process has also improved the joining of materials that are difficult, expensive and hazardous to join with welding techniques such as brazing and arc welding, resulting in safer and more reliable structures. The process has the potential to reduce costs and increase efficiency in manufacturing.
