Non science fiction, inventory of six most advanced welding technologies

01 laser welding

Laser welding: the surface to be processed is heated by laser radiation, and the surface heat is diffused internally through heat transfer. The workpiece is melted to form a specific molten pool by controlling the laser parameters such as laser pulse width, energy, peak power and repetition frequency.

Laser welding can be realized by 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 10 ~ 10 W / cm, it is heat conduction welding. At this time, the penetration is shallow and the welding speed is slow; When the power density is greater than 10 ~ 10 W / cm, the metal surface will be concave into “holes” under the action of heating to form deep penetration welding, which has the characteristics of fast welding speed and large depth width ratio.

Laser welding technology is widely applied in high-precision manufacturing fields such as automobile, ship, aircraft and high-speed railway, which has greatly improved people’s quality of life and led the household appliance industry into the era of precision industry.

Especially after the 42 meter seamless welding technology created by Volkswagen has greatly improved the integrity and stability of the car body, Haier Group, a leading household appliance enterprise, grandly launched the first washing machine produced by laser seamless welding technology. Advanced laser technology can bring great changes to people’s life.

02 laser hybrid welding

Laser hybrid welding is the combination of laser beam welding and MIG welding technology to obtain the best welding effect, fast and weld bridging ability. It is the most advanced welding method at present.

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.

Laser hybrid welding is suitable for many other applications in addition to the welding of automobile thin plate structural parts. For example, when this technology is applied to the production of concrete pump and mobile crane boom, these processes need to process high-strength steel, and the traditional technology often increases the cost due to the need for other auxiliary processes (such as preheating). Moreover, the technology can also be applied to the manufacturing of rail vehicles and conventional steel structures (such as bridges, oil tanks, etc.).

03 Friction stir welding

Friction stir welding uses friction heat and plastic deformation heat as welding heat source. The welding process of friction stir welding is that a mixing needle of a cylinder or other shape (such as a threaded cylinder) extends into the joint of the workpiece and makes it rub with the material of the welded workpiece through the high-speed rotation of the welding head, so as to increase and soften the material temperature of the connecting part.

In the process of friction stir welding, the workpiece should be rigidly fixed on the back pad, the welding head side rotates at high speed, and the joint of the edge workpiece moves relative to the workpiece.

The protruding section of the welding head extends into the material for friction and stirring. The shoulder of the welding head rubs with the workpiece surface to generate heat, which is used to prevent the overflow of materials in plastic state and remove the surface oxide film at the same time.

Leave a keyhole at the end of the friction stir weld. Usually, the keyhole can be cut off or sealed by other welding methods.

Friction stir welding can realize the welding between different materials, such as metals, ceramics, plastics and so on. Friction stir welding has high welding quality, is not easy to produce defects, is easy to realize mechanization, automation, stable quality and high cost efficiency.

04 electron beam welding

Electron beam welding is a method of welding by using the heat energy generated by the accelerated and focused electron beam bombarding the weldment placed in vacuum or non vacuum.

Electron beam welding is widely used in many industries, such as aerospace, atomic energy, national defense and military industry, automobile, electrical and electrical instruments, because it has the advantages of no electrode, difficult oxidation, good process repeatability and small thermal deformation.

Working principle of electron beam welding

The electron escapes from the emitter (cathode) in the electron gun. Under the action of accelerating voltage, the electron is accelerated to 0.3 ~ 0.7 times the speed of light and has a certain kinetic energy. The electron beam with high success rate density is converged by the action of electrostatic lens and electromagnetic lens in the electron gun. This electron beam impinges on the surface of the workpiece, and the electron kinetic energy is transformed into heat energy, which makes the metal melt and evaporate rapidly. Under the action of high-pressure metal vapor, a small hole, also known as “keyhole”, is quickly “drilled” on the surface of the workpiece. With the relative movement of the electron beam and the workpiece, the liquid metal flows around the small hole to the rear of the molten pool, and cools and solidifies to form a weld.

Main features of electron beam welding

The electron beam has strong penetration ability, high power density and large depth width ratio of weld, which can reach 50:1. It can realize one-time forming of large thickness materials, and the maximum welding thickness can reach 300mm. Good welding accessibility, fast welding speed, generally more than 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 from 0.05mm to 300mm. It is formed by one-time welding without beveling, which can not be achieved by other welding methods. Electron beam welding can be used for a wide range of materials, especially for the welding of active metals, refractory metals and workpieces with high quality requirements.

05 Ultrasonic metal welding

Ultrasonic metal welding is a special method to connect the same metal or dissimilar metal by using the mechanical vibration energy of ultrasonic frequency. During ultrasonic welding, metal does not transmit current to the workpiece or apply high-temperature heat source to the workpiece, but changes the frame vibration energy into friction work, deformation energy and limited temperature rise under static pressure. Metallurgical bonding between joints is a kind of solid-state welding without melting of base metal.

The ultrasonic metal welding machine can effectively overcome the phenomena of splash and oxidation during resistance welding. The ultrasonic metal welding machine can carry out single point welding, multi-point welding and short strip welding on the thin wire or sheet materials of non-ferrous metals such as copper, silver, aluminum and nickel. It can be widely used in the welding of thyristor leads, fuse blades, electrical leads, lithium battery pole pieces and pole lugs.

Ultrasonic metal welding uses high-frequency vibration wave to transfer to the metal surface to be welded. Under pressure, the two metal surfaces rub against each other to form the fusion between molecular layers.

Ultrasonic metal welding has the advantages of fast, energy saving, high fusion strength, good conductivity, no spark and close to cold machining; The disadvantages are that the welded metal parts cannot be too thick (generally less than or equal to 5mm), the welding spot cannot be too large, and pressure is required.

06 flash butt welding

The principle of flash butt welding is to use the butt welding machine to make the metal contact at both ends. Through the strong current of low voltage, after the metal is heated to a certain temperature and softened, carry out axial pressure upsetting to form a butt welding joint.

The two weldments are clamped by the two clamp electrodes and connected to the power supply before they are in contact. Move the movable clamp. The end faces of the two weldments are gently contacted, that is, they are powered on for heating. The contact point explodes due to heating, and the jet spark forms a flash. Move the movable clamp continuously, and the flash occurs continuously. The two ends of the weldment are heated. After reaching a certain temperature, squeeze the end faces of the two workpieces, cut off the welding power supply and firmly weld together. The resistance is used to heat the weldment joint to produce flash at the contact point, melt the end metal of the weldment, and quickly apply the top force to complete the welding.

Steel bar flash butt welding is a pressure welding method that installs two steel bars into a butt joint form, uses 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 splash, form flash, accompanied by pungent smell, release trace molecules, and quickly apply upsetting force.