1. Laser welding
The laser radiation heats the surface to be processed, and the surface heat diffuses to the inside through heat 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.
（1）Spot welding and fixing of welded parts
（2）Continuous laser welding
Laser welding can be realized by a continuous or pulsed laser beam. The principle of laser welding can be divided into heat conduction welding and laser deep penetration welding. The power density is less than 10~10 W/cm in heat conduction welding. At this time, the penetration depth is shallow and the welding speed is slow; when the power density is greater than 10~10 W/cm, the metal surface is recessed into “holes” under the action of heat to form deep penetration welding. Features of fast welding speed and large aspect ratio.
Laser welding technology is widely used in high-precision manufacturing fields such as automobiles, ships, airplanes, and high-speed railways. It has brought significant improvements to people’s quality of life and has led the home appliance industry into the era of precision manufacturing.
Especially after the 42-meter seamless welding technology created by Volkswagen has greatly improved the integrity and stability of the car body, the leading home appliance company Haier Group grandly launched the first washing machine produced with laser seamless welding technology. Advanced laser technology can help The lives of the people have brought huge changes.
2. Laser hybrid welding
Laser hybrid welding is a combination of laser beam welding and MIG welding technology to obtain the best welding effect, fast and weld bridging ability, and is the most advanced welding method currently.
The advantages of laser hybrid welding are fast speed, small thermal deformation, small heat-affected area, and ensuring the metal structure and mechanical properties of the weld.
In addition to the welding of automotive thin-plate structural parts, laser hybrid welding is also suitable for many other applications. For example, applying this technology to the production of concrete pumps and mobile crane booms. These processes require the processing of high-strength steel. Traditional technologies often require other auxiliary processes (such as preheating) to increase costs. Furthermore, the technology can also be applied to the manufacturing of rail vehicles and conventional steel structures (such as bridges, fuel tanks, etc.).
3. Friction stir welding
Friction stir welding uses friction heat and plastic deformation heat as the welding heat source. The friction stir welding process involves a cylinder or other shape (such as a threaded cylinder) extending into the joint of the workpiece, and the high-speed rotation of the welding head causes it to rub against the welding workpiece material, thereby making the connection part The temperature of the material increases and softens.
In friction stir welding, the workpiece must be rigidly fixed on the back pad during the welding process, and the welding head rotates at a high speed, and the joint of the edge of the workpiece moves relative to the workpiece.
The protruding section of the welding head extends 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 state material, and at the same time can play a role in removing the surface oxide film.
At the end of the friction stir welding, a keyhole is left at the end. Usually, this keyhole can be cut off or sealed by other welding methods.
Friction stir welding can realize welding between dissimilar materials, such as metals, ceramics, and plastics. 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.
4. Electron beam welding
Electron beam welding is a method of welding using the heat generated by accelerated and focused electron beam bombardment of weldments 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, electrical and electrical instruments because of its advantages of no welding rod, not easy to oxidize, good process repeatability, and small thermal deformation.
（1）Principle of Electron Beam Welding
The electron escapes from the emitter (cathode) in the electron gun. Under the action of the accelerating voltage, the electron is accelerated to 0.3 to 0.7 times the speed of light, which has a certain kinetic energy. Then through the action of the electrostatic lens and the electromagnetic lens in the electron gun, the electron beam with a high success rate is concentrated. This electron beam hits the surface of the workpiece, and the kinetic energy of the electrons is converted into heat energy, which makes the metal melt and evaporate rapidly. Under the action of high-pressure metal vapor, a small hole is rapidly “drilled” on the surface of the workpiece, which is also called 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 it cools and solidifies to form a weld.
（2）Main features of electron beam welding
The electron beam penetration ability is strong, the power density is extremely high, and the welding seam aspect ratio can reach 50:1, which can realize the one-time forming of large thickness materials, and the maximum welding thickness can reach 300mm. Good welding accessibility, fast welding speed, generally above 1m/min, small heat-affected zone, small welding deformation, and high welding structure accuracy. The electron beam energy can be adjusted, and the thickness of the metal to be welded can be as thin as 0.05mm to as thick as 300mm. It can be welded at one time without grooves, which is unattainable 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.
5. Ultrasonic metal welding
Ultrasonic metal welding is a special method that uses mechanical vibration energy of ultrasonic frequency to connect the same or dissimilar metals. When metal is ultrasonically welded, it neither delivers current to the workpiece nor applies 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 workroom. The metallurgical bonding between the joints is solid-state welding that is achieved without the base material being melted.
It effectively overcomes the phenomenon of spatter and oxidation caused by resistance welding. The ultrasonic metal welding machine can perform single-point welding, multi-point welding, and short-strip welding on thin wires or sheet materials of non-ferrous metals such as copper, silver, aluminum, and nickel. Shaped 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 be transmitted to the metal surface to be welded. Under pressure, the two metal surfaces are rubbed against each other to form a fusion between molecular layers.
The advantages of ultrasonic metal welding are that it is fast, energy-saving, has high fusion strength, good conductivity, no sparks, and is close to cold processing; the disadvantage is that the welded metal parts cannot be too thick (generally less than or equal to 5mm), and the welding point cannot be too large. Pressurize.
6. Flash butt welding
The principle of flash butt welding is to use a butt welder to make the two ends of the metal contact, through a low voltage strong current, after the metal is heated to a certain temperature and softened, the axial pressure upsetting is carried out to form a butt-welded joint.
Before the two weldments are in contact, they are clamped by the two clamp electrodes and connected to the power source. The movable fixture is moved, and the end faces of the two weldments are lightly contacted to be energized and heated. The contact point blasts due to the heating to form liquid metal, and the jet sparks to form a flash. The movable fixture is continuously moved, flashing occurs continuously, and both ends of the weldment are heated. After reaching a certain temperature, the end faces of the two workpieces are squeezed, the welding power is cut off, and the welding is firmly welded together. Use resistance to heat the weldment joint to make the contact point flash, melt the metal on the end face of the weldment, and quickly apply top force to complete the welding.
Rebar flash butt welding is to install two steel bars in a butt joint form and use the resistance heat generated by the welding current through the contact points of the two steel bars to melt the metal at the contact points, produce strong splashes, and form flashes, accompanied by pungent odors, and release traces Molecule, a pressure welding method completed by rapidly applying upsetting force.
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