1. Laser welding
Laser radiation heats the surface to be machined, and the heat is guided into internal diffusion through heat transfer. By controlling the laser pulse width, energy, peak power, and repetition frequency, the workpiece is melted to form a specific molten pool.
Spot weld the weldment
Continuous laser welding
Laser welding can be achieved through the use of either a continuous or pulsed laser beam.
The principle of laser welding can be divided into two categories: heat conduction welding and laser deep penetration welding.
When the power density is less than 10^10 W/cm^2, it is considered heat conduction welding.
When the power density is greater than 10^10 W/cm^2, the metal surface is concave and forms “holes” due to heating, resulting in deep fusion welding. This process is characterized by its fast welding speed and high depth-to-width ratio.
Laser welding technology is widely used in high-precision manufacturing industries such as automobiles, ships, airplanes, and high-speed railways. It has greatly improved people’s quality of life and pushed the home appliance industry into the era of precision manufacturing.
In particular, Volkswagen’s creation of the 42-meter seamless welding technology has significantly enhanced the body integrity and stability.
Haier Group, a leading home appliance enterprise, has proudly launched the first washing machine produced using laser seamless welding technology.
The advanced laser technology holds the potential to bring significant change to people’s lives.
2. Laser hybrid welding
Laser hybrid welding combines laser beam welding and MIG welding technology to produce the optimal welding effect, fast welding speed, and excellent weld bridging ability.
It is currently the most advanced welding method.
The benefits of laser hybrid welding include high speed, minimal thermal deformation, a small heat-affected area, and preservation of the metal structure and mechanical properties of the weld.
Laser hybrid welding is not only suitable for welding automobile sheet structures, but also for many other applications.
For instance, when this technology is used in the production of concrete pumps and mobile crane booms, these processes require the use of high-strength steel and traditional technologies often need additional processes, such as preheating, which increases the cost.
Additionally, the technology can also be applied in the manufacture of rail vehicles and conventional steel structures, such as bridges, fuel tanks, and others.
3. Friction stir welding
Friction stir welding utilizes friction heat and plastic deformation heat as its heat sources.
Friction stir welding (FSW) is a process in which a cylindrical or other shaped (such as a threaded cylinder) pin is inserted into the joint of the workpiece.
The welding head rotates at a high speed and rubs against the material at the joint, causing its temperature to rise and soften.
In the friction stir welding process, the workpiece must be securely fixed to the back pad. The welding head rotates at a high speed while the seam of the edge workpiece moves relative to the workpiece.
The welding head’s protruding section extends into the material for friction and stirring, and its shoulder rubs against the surface of the workpiece to generate heat, which is used to prevent the overflow of plastic material and remove the surface oxide film.
Friction stir welding results in a keyhole at the end of the process.
This keyhole can typically be removed or sealed with another welding method.
Friction stir welding is capable of welding a variety of dissimilar materials, such as metals, ceramics, and plastics.
It boasts many benefits, including high-quality welding, minimal defects, ease of mechanization and automation, consistent quality, and high cost-efficiency.
4. Electron beam welding
Electron beam welding (EBW) is a type of welding method that uses the heat energy generated by accelerating and focusing an electron beam that bombards the material to be welded in a vacuum or non-vacuum environment.
Electron beam welding (EBW) is widely utilized in industries such as aerospace, atomic energy, national defense, military, automobile, electrical instruments, and many others due to its benefits such as the absence of electrodes, reduced oxidation, excellent process repeatability, and minimal thermal deformation.
Working principle of electron beam welding
The electrons are released from the cathode of the electron gun.
Under the influence of the accelerating voltage, the electrons are accelerated to speeds ranging from 0.3 to 0.7 times the speed of light and gain a certain amount of kinetic energy.
The electron beam with high density can then be focused by the electrostatic lens and electromagnetic lens within the electron gun.
As the electron beam strikes the surface of the workpiece, its kinetic energy transforms into heat energy, causing the metal to rapidly melt and evaporate.
Due to the high-pressure metal vapor, a small hole known as a keyhole is quickly formed on the surface of the workpiece.
With the relative movement of the electron beam and workpiece, the liquid metal flows around the keyhole and solidifies to form the weld at the back of the weld pool.
Main characteristics of electron beam welding
The results show that the electron beam has strong penetration and a high power density, resulting in a large depth-to-width ratio of the weld, which can reach 50:1. It is capable of welding large thickness materials in a single pass, with a maximum welding thickness of up to 300 mm.
Electron beam welding also has the advantage of good accessibility, fast welding speed (generally over 1m/min), a small heat-affected zone, minimal welding deformation, and high welding structure precision. The energy of the electron beam can be adjusted to accommodate a wide range of metal thicknesses, from 0.05mm to 300 mm, without the need for a groove, making it a versatile option compared to other welding methods.
Additionally, electron beam welding is suitable for welding a variety of materials, particularly active metals, refractory metals, and high-quality workpieces.
5. Ultrasonic metal welding
Ultrasonic metal welding is a unique method of connecting similar or dissimilar metals by utilizing the mechanical vibration energy of ultrasonic frequency. Unlike other welding methods, ultrasonic metal welding does not require an electrical current or high-temperature heat source to be applied to the workpiece.
Instead, under static pressure, the vibration energy from the frame is converted into friction work, deformation energy, and a limited increase in temperature. This results in metallurgical bonding between the joints, creating a solid-state weld without the base metal melting.
It effectively overcomes the spatter and oxidation during resistance welding.
It can be used for single-spot welding, multi-spot welding, and short strip welding of materials such as copper, silver, aluminum, nickel, and other non-ferrous wires or sheets. The welding machines are widely used in the welding of SCR leads, fuses, electrical leads, lithium battery pole pieces, and pole lugs.
Ultrasonic metal welding utilizes high-frequency vibration waves that are transmitted to the metal surface to be welded. Under pressure, the two metal surfaces are rubbed against each other to form a bond between molecular layers.
The advantages of ultrasonic metal welding include speed, energy efficiency, high fusion strength, good conductivity, a lack of sparks, and a process similar to cold processing. However, its disadvantages are that the welded metal parts should not be too thick (generally not exceeding 5mm), the welding spot should not be too large, and pressure must be applied.
6. Flash butt welding
The principle of flash butt welding is to use a butt welding machine to bring the two ends of metal into contact. A low voltage and high current are applied, heating the metal to a certain temperature until it becomes soft. The welding joint is formed by applying axial pressure and forging.
The principle of flash butt welding is to use a butt welding machine to bring the two ends of the metal into contact. A low voltage and high current is applied, causing the metal to heat up to a specific temperature and become soft. An axial pressure forging is then performed to create the butt welding joint.
The two pieces to be welded are held in place by two clamp electrodes, which are then connected to the power supply before making contact. When the movable clamp is moved, the two end faces of the pieces make a slight contact, which electrifies and heats them.
This results in a spark, which forms the flash as the contact point explodes due to the liquid metal formed by the heating. As the movable fixture continues to move, flash continues to occur, heating both ends of the pieces.
Once they reach the desired temperature, the ends of the two workpieces are extruded and the welding power is cut off, solidifying the pieces together. The resistance of the joint is used to heat the weldment, causing the contact point to flash and melt the metal on the end face of the weldment. A top force is then applied quickly to complete the welding process.
Steel flash butt welding involves inserting two steel bars into a butt joint. The welding current passing through the contact point of the two steel bars generates resistance heat that melts the metal at the contact point and produces a strong spark. This forms a flash and releases trace molecules, accompanied by a pungent odor. The pressure welding process is then quickly completed by applying forging force.
