1. Laser welding
The laser radiation heats the surface to be machined and the heat is directed to 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.
Weld spot welding
Continuous laser welding
Laser welding can be achieved through the use of 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/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 42-meter continuous welding technology has significantly improved the integrity and stability of the body.
Haier Group, a leading home appliance company, proudly launched the first washing machine produced with seamless laser welding technology.
Advanced laser technology has the potential to bring significant changes to people's lives.
2. Hybrid laser welding
Hybrid laser welding combines laser beam welding and MIG welding technology to produce ideal welding effect, fast welding speed and excellent solder bridging ability.
It is currently the most advanced welding method.
The benefits of hybrid laser welding include high speed, minimal thermal deformation, a small heat-affected area, and preservation of the metal structure and mechanical properties of the weld.
Hybrid laser welding is not only suitable for welding automotive sheet metal structures, but also for many other applications.
For example, 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 require additional processes, such as preheating, which increases the cost.
Furthermore, the technology can also be applied to the manufacture of railway vehicles and conventional metallic structures, such as bridges, fuel tanks, among others.
3. Friction stir welding
Friction welding uses frictional heat and plastic deformation heat as heat sources.
Friction stir welding (FSW) is a process in which a cylindrical or other shaped pin (such as a threaded cylinder) is inserted into the joint of the workpiece.
The welding head rotates at high speed and rubs against the material at the joint, causing its temperature to rise and soften it.
In the friction stir welding process, the workpiece must be securely fixed to the abutment. The welding head rotates at high speed while the edge piece seam moves relative to the workpiece.
The protruding section of the welding head 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 overflow of the plastic material and remove the surface oxide film.
Friction welding results in a keyhole at the end of the process.
This keyhole can usually be removed or sealed with another welding method.
Friction stir welding is capable of welding a variety of different materials such as metals, ceramics, and plastics.
It has many benefits, including high-quality welding, minimal defects, ease of mechanization and automation, consistent quality and high cost-effectiveness.
4. Electron beam welding
Electron beam welding (EBW) is a type of welding method that utilizes thermal 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 used in industries such as aerospace, atomic energy, national defense, military, automobile, electrical instruments and many others due to its benefits such as no electrodes, reduced oxidation, excellent process repeatability and deformation minimum heat.
Working principle of electron beam welding
Electrons are released from the cathode of the electron gun.
Under the influence of the accelerating voltage, 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 high-density electron beam can then be focused by the electrostatic lens and electromagnetic lens inside the electron gun.
As the electron beam hits the surface of the part, its kinetic energy transforms into thermal energy, causing the metal to melt and evaporate quickly.
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 the 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 high power density, resulting in a large weld depth/width ratio, which can reach 50:1. It is capable of welding thick materials in a single pass, with a maximum welding thickness of up to 300 mm.
Electron beam welding also has the advantages of good accessibility, fast welding speed (generally above 1m/min), a small heat-affected zone, minimal welding deformation and high precision of the welding structure. The electron beam energy can be adjusted to accommodate a wide range of metal thicknesses, from 0.05mm to 300mm, without the need for slotting, making it a versatile option compared to other welding methods.
Furthermore, electron beam welding is suitable for welding a variety of materials, especially active metals, refractory metals and high-quality parts.
5. Ultrasonic metal welding
Ultrasonic metal welding is a unique method of connecting similar or dissimilar metals using the mechanical vibration energy of ultrasonic frequency. Unlike other welding methods, ultrasonic metal welding does not require the application of an electrical current or high-temperature heat source to the workpiece.
Instead, under static pressure, the structure's vibration energy is converted into frictional work, strain energy, and limited temperature increase. This results in metallurgical bonding between the joints, creating a solid-state weld without melting the base metal.
It effectively overcomes spatter and oxidation during resistance welding.
It can be used for single-point welding, multi-point welding and short strip welding of materials such as copper, silver, aluminum, nickel and other non-ferrous wires or sheets. Welding machines are widely used in welding SCR cables, fuses, electrical cables, lithium battery pole parts and pole terminals.
Ultrasonic metal welding uses 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 the molecular layers.
The advantages of ultrasonic metal welding include speed, energy efficiency, high melt strength, good conductivity, lack of sparks, and a process similar to cold processing. However, its disadvantages are that the welded metal parts must not be too thick (generally not exceeding 5 mm), the welding spot must 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 the metal into contact. A low voltage and high current are applied, heating the metal to a certain temperature until it softens. 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 are 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 parts to be welded are clamped by two clamp electrodes, which are then connected to the power source before contact. When the movable clamp is moved, the two end faces of the parts make 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 heating. As the movable fixture continues to move, the flash continues to occur, heating both ends of the parts.
Upon reaching the desired temperature, the ends of the two pieces are extruded and the welding power is cut, solidifying the pieces. The resistance of the joint is used to heat the weld, causing the contact point to fail and melt the metal at the weld end face. A higher force is then quickly applied to complete the welding process.
Steel butt welding involves inserting two steel bars into a butt joint. The welding current that passes 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 the application of forging force.
