Analysis of five laser welding processes in the field of industrial manufacturing

With the rapid development of the global manufacturing industry, the application of welding technology has become more and more extensive, and the level of welding technology has also become higher and higher. New welding technology methods are constantly emerging, and professional welding equipment is changing day by day. At the same time, domestic and foreign welding equipment manufacturers have also demonstrated their strengths in various ways, especially by exhibiting a wide range of products and advanced technologies at the exhibition. From the development of carbon arc welding at the end of the century to the present, it has only a history of more than one hundred years, and 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-scale, complex and high-parameters.

Processing principle of laser welding technology

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.

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. The power density is less than 10～10 W/cm is 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 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 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.

The processing principle of laser hybrid welding

Laser hybrid welding is the combination of laser beam welding and MIG welding technology to obtain the best welding results, fast and weld bridging capabilities, 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 ensure 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) and lead to increased costs. Furthermore, the technology can also be applied to the manufacturing of rail vehicles and conventional steel structures (such as bridges, fuel tanks, etc.).

The processing principle of 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 material temperature rises and softens.

In friction stir welding, the workpiece must be rigidly fixed on the backing pad during the welding process, and the welding head rotates at a high speed, and the seam 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. 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, and is easy to achieve mechanization, automation, stable quality, low cost and high efficiency.

The processing principle of 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 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 it has the advantages of no welding rod, not easy to oxidize, good process repeatability and small thermal deformation.

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 to make 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, 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.

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. The welding accessibility is good, the welding speed is fast, generally above 1m/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 welded metal can be from as thin as 0.05mm to as thick as 300mm. Without grooves, it can be welded at one time, which is unattainable by other welding methods. The range of materials that can be welded by electron beam is large, and it is especially suitable for welding active metals, refractory metals and workpieces with high quality requirements.

The processing principle of 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, neither electric current nor high-temperature heat source is applied 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 work room. The metallurgical bonding between the joints is a 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, high fusion strength, good conductivity, no sparks, and 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.

The advantages, characteristics and application fields of laser welding, at present, there are more and more companies using mechanical welding machines in the market. Because of its unique advantages, it has been successfully applied to 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, automobiles, steel and other industrial fields. Wuhan Jinmi Laser has been devoted to researching and manufacturing advanced school teaching laser equipment, providing high-functional and easy-to-operate industrial laser equipment for Guangzhou University, and combining advanced technology at home and abroad to provide laser welding, cutting, Cladding and marking equipment.