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With the rapid development of the global manufacturing industry, welding process technology has become more and more widely used, and the level of welding technology has become higher and higher. New welding process methods are constantly emerging, and professional welding equipment is changing with each passing day. At the same time, domestic and foreign welding equipment manufacturers have also demonstrated their strengths in various ways, especially with the help of the exhibition to display a wide variety of products and advanced technologies.
Since the development of carbon arc welding at the end of the century, it has only a history of more than 100 years, hundreds of methods have been formed, and the level of welding technology has reached a new height. Welded structures are developing in the direction of large size, complexity, and high parameters.
Laser Welding Technology Processes Principle
Laser radiation heats the surface to be processed, and the surface heat diffuses to the interior through thermal conduction. By controlling the laser parameters such as the width, energy, peak power, and repetition frequency of the laser pulse, the workpiece is melted to form a specific molten pool.
Laser welding can be realized by the continuous or pulsed laser beam. The principle of laser welding can be divided into heat conduction welding and laser deep penetration welding. When the power density is less than 106-107 W/cm2, it is thermal conduction welding. At this time, the penetration depth is shallow and the welding speed is slow; when the power density is greater than 106-107 W/cm2, the metal surface is concave into “holes” under the action of heat, forming deep penetration welding. The welding speed is fast and the aspect ratio is large.
Laser welding technology is widely used in high-precision manufacturing fields such as automobiles, ships, aircraft, and high-speed rail, which has brought a significant improvement to people’s quality of life and has led the home appliance industry into the era of precision work.
Especially after the 42-meter seamless welding technology created by Volkswagen, which greatly improved the integrity and stability of the car body, Haier Group, a leading home appliance company, grandly launched the first washing machine produced with laser seamless welding technology. People’s lives have brought huge changes.
Laser Hybrid Welding Processes Principle
There are many forms of laser-hybrid welding, including Laser-MAG/MIG hybrid welding, Laser-TIG hybrid welding, laser-plasma arc hybrid welding, etc. Among them, the commonly used laser light sources at this stage are fiber lasers and semiconductor lasers. For example, Raycus continuous fiber laser 4000W, 6000W, and fiber output semiconductor laser 4000W.
Laser-MAG hybrid welding has two welding heat sources, namely laser and MAG arc, which can form an effective molten pool when welding as a heat source alone, but the characteristics of the molten pool are different: the characteristics of the laser welding molten pool are “deep and narrow” ”, the opening area is small and the depth is large, which is not conducive to welding seam forming; the characteristics of MAG arc welding molten pool are “shallow and wide”, the opening area is large, and the depth is small, which is conducive to welding seam forming and strong bridging ability.
The advantages of laser hybrid welding are: high speed, small thermal deformation, small heat affected area, and ensure the metal structure and mechanical properties of the weld. In addition to the welding of automotive sheet metal structures, laser hybrid welding is also suitable for many other applications. For example, this technology is applied to the production of concrete pumps and mobile crane jibs, which require the processing of high-strength steel, and the traditional technology often leads to an increase in cost due to the need for other auxiliary processes such as preheating. Furthermore, the technology can also be applied to manufacture rail vehicles and conventional steel structures (such as bridges, fuel tanks, etc.).
Friction Stir Welding Processes Principle
Friction stir welding uses friction heat and plastic deformation heat as welding heat sources. The welding process of friction stir welding is when a stirring needle of a cylinder or other shape (such as a threaded cylinder) is inserted into the joint of the workpiece, and the high-speed rotation of the welding head makes it rub against the welding workpiece material, so as to make the connection part The material softens as the temperature rises.
In friction stir welding, the workpiece should be rigidly fixed on the back pad during the welding process, the welding head rotates at a high speed, and the seam along the workpiece moves relative to the workpiece.
The protruding section of the welding head protrudes into the material for friction and stirring, and the shoulder of the welding head rubs against the surface of the workpiece to generate heat and is used to prevent the overflow of the plastic material, and at the same time, it can remove the oxide film on the surface.
A keyhole is left in the terminal at the end of the friction stir weld. Usually, this keyhole can be cut off, or it can be sealed by other welding methods.
Friction stir welding can realize welding between dissimilar materials, such as metals, ceramics, plastics, etc. Friction stir welding has high welding quality, is not easy to produce defects, easy to achieve mechanization, automation, stable quality, low cost, and high efficiency.
Electron Beam Welding Processes Principle
Electron beam welding is a welding method using the thermal energy generated by the accelerated and focused electron beam bombarding the weldment placed in a vacuum or non-vacuum.
Electron beam welding is widely used in many industries such as aerospace, atomic energy, national defense, and military industry, automobiles, and electrical and electrical instruments because of its advantages of no electrode, not easy to oxidize, good process repeatability, and small thermal deformation.
The electrons escape from the emitter (cathode) in the electron gun. Under the action of the accelerating voltage, the electrons are accelerated to 0.3 to 0.7 times the speed of light and have a certain kinetic energy. Through the action of the electrostatic lens and the electromagnetic lens in the electron gun, the electron beam current with high power density is converged. This electron beam hits the surface of the workpiece, and the kinetic energy of the electrons is converted into thermal energy to melt and evaporate the metal rapidly. Under the action of high-pressure metal steam, a small hole is quickly “drilled” on the surface of the workpiece, also known as a “keyhole”. With the relative movement of the electron beam and the workpiece, the liquid metal flows around the small hole to the back of the molten pool. And cool and solidify to form a weld.
The electron beam penetration ability is strong, the power density is extremely high, and the aspect ratio of the welding seam is large, which can reach 50:1. The welding accessibility is good, the welding speed is fast, generally more than 1 m/min, the heat-affected zone is small, the welding deformation is small, and the welding structure precision is high. The energy of the electron beam can be adjusted, and the thickness of the metal to be welded can be as thin as 0.05mm to as thick as 300mm, without grooves, and one-time welding, which cannot be achieved by other welding methods. The range of materials that can be welded by the electron beam is large, and it is especially suitable for the welding of active metals, refractory metals, and workpieces with high-quality requirements.
Ultrasonic Metal Welding Processes Principle
Ultrasonic metal welding is a special method of joining the same metal or dissimilar metals by using the mechanical vibration energy of ultrasonic frequency. When the metal is ultrasonically welded, it does not transmit current to the workpiece, nor does it apply a high-temperature heat source to the workpiece, but under static pressure, the vibration energy of the frame is converted into friction work, deformation energy, and limited temperature rise in the workplace.
The metallurgical bond between the joints is solid-state welding achieved without melting the base metal. It effectively overcomes the phenomenon of spatter and oxidation caused by resistance welding, and the ultrasonic metal welding machine can perform single-point welding, multi-point welding, and short strip welding of copper, silver, aluminum, nickel, and other non-ferrous metal filaments or sheet materials shape welding. It can be widely used in the welding of SCR leads, fuse pieces, electrical leads, lithium battery pole pieces, and tabs.
Ultrasonic metal welding uses high-frequency vibration waves to transmit to the metal surface to be welded. Under pressure, the two metal surfaces are rubbed against each other to form a fusion between the molecular layers. The advantages of ultrasonic metal welding are that it is fast, energy-saving, has high fusion strength, has good electrical conductivity, has no spark, and is close to cold processing; pressurized.
Advantages, characteristics, and application fields of laser welding, at present, there are more and more companies using mechanical welding processes machines in the market. Due to its unique advantages, it has been successfully used in the precision welding of micro and small parts. The emergence of high-power laser equipment has opened up a new field of laser welding. Deep penetration welding based on the pinhole effect has been obtained, and it has been widely used in machinery, automobile, steel, and other industrial fields.