The Essential Goodies For Sheet Metal Factories - Laser Welding Machines

Laser Welding Machines

Laser welding is a new type of welding, mainly for thin-walled materials and precision parts, with the advantages of easy operation, beautiful welding seams and high speed. As an essential small machine for factories and homes, laser welding machines have become very popular in recent years. In this article, we will introduce laser welding machines in detail from several angles to help you better understand and buy laser welding machines.

Working Principle

Laser welding is the use of high-energy laser pulses on the material in a tiny area of local heating. The laser radiation energy is through heat conduction to the internal diffusion of the material. The material melted to form a specific melt pool. It is a new type of welding method, mainly for the welding of thin-walled materials, precision parts, spot welding, butt welding, stack welding, sealing welding, etc., with high depth to width ratio, small weld width, small heat affected zone, small deformation, fast welding speed, flat and beautiful weld seam, no treatment or only simple treatment after welding, high quality weld seam, no porosity, precise control, small focused spot, high positioning accuracy, easy to achieve automation The weld is easy to automate.

Main Types

Laser welding machines are also often called energy negative feedback laser welding machines, laser cold welding machines, laser argon welding machines, laser welding equipment, etc. According to its working method, it can often be divided into laser mould burner (manual laser welding equipment), automatic laser welding machine, jewellery laser welding machine, laser spot welding machine, fiberoptic transmission laser welding machine, vibrating mirror welding machine, handheld welding machine, etc. Special laser welding equipment are sensor welding machine, silicon steel sheet laser welding equipment, keyboard laser welding equipment. The weldable shapes are: points, lines, circles, squares or any flat shapes drawn by AUTOCAD software.

Key Parameters

Power density is one of the most critical parameters in laser processing. With a high power density, the surface layer can be heated to the boiling point within a microsecond time frame, producing a large number of vapors. Therefore, high power densities are beneficial for material removal processes such as punching, cutting and engraving. For lower power densities, it takes several milliseconds for the surface layer temperature to reach the boiling point and the bottom layer reaches the melting point before the surface layer vaporises, making it easy to form a good fusion weld. Therefore, in conduction laser welding, the power density is in the range of 104 to 106 W/㎡.

The pulse waveform is an important issue in welding, especially for thin sheet welding. When a high intensity beam is directed at the surface of the material, the energy that will be reflected from the metal surface is lost and the reflection rate varies with the surface temperature. The reflectivity of the metal varies considerably over the duration of a pulse.

Pulse width is one of the important parameters of pulse welding, both in terms of material removal and material melting, and also as a key parameter in determining the cost and size of the processing equipment.

The effect of the off-focus volume is due to the high power density in the centre of the spot at the laser focal point, which tends to evaporate into a hole. The power density is relatively evenly distributed in all planes away from the laser focal point. There are two types of defocusing: positive defocusing and negative defocusing. The focal plane is located above the workpiece for positive defocusing, and vice versa for negative defocusing. According to geometric optics theory, when the positive and negative of focus plane and welding plane distance are equal, the corresponding plane of the power density is approximately the same, but in practice the shape of the molten pool obtained is different. With negative defocusing, a greater depth of melt can be obtained, which is related to the formation process of the melt pool.

Advantageous Features

The laser welding machine has a high degree of automation and a simple welding process. The non-contact method of operation meets the requirements of cleanliness and environmental protection. The use of laser welding machines increases the efficiency of the workpiece, resulting in a beautiful appearance, small weld seams, large welding depths and high welding quality. Laser welding machines are widely used for dental denture processing, keyboard welding, silicon steel welding, sensor welding, battery sealing cap welding and many more. However, laser welding machines have limitations in these areas due to their high cost and the high precision required for the assembly of the workpiece.

Application Areas

Manufacturing

Laser welding technology is widely used in foreign car manufacturing. According to statistics in 2000, the global scope of cutting blank laser welding production line more than 100, the annual output of car components welded blank plate 70 million pieces, and continues to grow at a high rate. The domestic production of the introduction models also uses some cut blank structures. In Japan, CO2 laser welding is used instead of flash butt welding for the connection of rolled steel coils in the steel industry, and the research on welding of ultra-thin plates, such as foils with a plate thickness of 100 microns or less, cannot be welded, but the YAG laser welding with a special output power waveform is successful, showing the broad future of laser welding. Japan has also successfully developed YAG laser welding for the first time in the world for the repair of thin tubes of steam generators in nuclear reactors, etc. In Japan, laser welding technology for gears is also being carried out.

Powder Metallurgy

With the continuous development of science and technology, many industrial technologies on the special requirements of the material, the application of smelting and casting methods of manufacturing materials can not meet the needs. As powder metallurgy materials have special properties and manufacturing advantages, in some areas such as automotive, aircraft, tools and cutting tools, the manufacturing industry is replacing the traditional smelting and casting materials. With the increasing development of powder metallurgy materials, it is increasingly prominent in other parts of the connection problem, so that the application of powder metallurgy materials is limited. In the early eighties, laser welding with its unique advantages in the field of powder metallurgical materials processing, for the application of powder metallurgical materials opened up new prospects, such as the use of powder metallurgical materials commonly used in connection with the brazing method of welding diamond, due to the combination of low strength, heat-affected zone is wide, especially can not adapt to high temperature and strength requirements caused by high brazing material melting off, the use of laser welding can improve the welding strength as well as High temperature resistance.

Automotive Industry

In the late 1980s, kilowatt-class lasers were successfully used in industrial production, and today laser welding lines have appeared on a large scale in the automotive manufacturing industry, becoming one of the outstanding achievements of the automotive industry. European car manufacturers were the first to use laser welding for roof, body and side frame sheet metal welding as early as the 1980s, and in the 1990s the US competed to introduce laser welding into automotive manufacturing, which developed rapidly despite a late start. Italy used laser welding in the welding assembly of most steel sheet components, Japan in the manufacture of body coverings are used in the laser welding and cutting process. High strength steel laser welded assemblies, because of their excellent performance in car body manufacturing, are increasingly used, according to the U.S. metal market statistics, to the end of 2002, the consumption of laser welded steel structures will reach 70,000 t than in 1998, an increase of three times. According to the characteristics of the automotive industry batch, high degree of automation, laser welding equipment in high-power, multi-path type direction. In the process of the United States Sandia National Laboratory and PrattWitney joint research in the laser welding process to add powdered metal and metal wire, Germany Bremen Institute of Applied Beam Technology in the use of laser welding of aluminum alloy body skeleton in a large number of studies, that the addition of filler metal in the weld helps to eliminate thermal cracking, improve welding speed, to solve the problem of tolerance. The line developed is already in production at the factory.

Electronics Industry

Laser welding is widely used in the electronics industry, especially in the microelectronics industry. Due to the small heat-affected zone, rapid heating concentration and low thermal stress of laser welding, it is being used in the packaging of integrated circuits and semiconductor device housings, showing unique superiority. Laser welding has also been used in the development of vacuum devices, such as molybdenum focusing poles with stainless steel support rings and fast-heating cathode filament assemblies. Sensors or temperature controllers in the elastic thin-walled corrugated sheet its thickness in 0.05-0.1 mm, the use of traditional welding methods difficult to solve, TIG welding easy to weld through, plasma stability is poor, the impact of many factors and the use of laser welding effect is very good, widely used.

Biomedical

Laser welding of biological tissues began in the 1970s, with laser welding of fallopian tubes and blood vessels and the success of the superiority shown, so that more researchers try to weld a variety of biological tissues, and extended to the welding of other tissues. Research on laser welding of nerves at home and abroad has focused on laser wavelength, dose and its functional recovery as well as the selection of laser welding materials and other aspects of research. Liu Tongjun conducted laser welding of small blood vessels and skin and other basic research based on welding studies on the common bile duct of rats. In comparison with traditional suturing methods, laser welding has the advantages of fast anastomosis, no foreign body reaction during the healing process, maintaining the mechanical properties of the welded area, and the growth of the repaired tissue in accordance with its original biomechanical properties.

Other Areas

In other industries, laser welding is gradually increasing, especially in special materials welding. China has conducted many studies, such as laser welding of BT20 titanium alloy, HEl30 alloy, Li-ion batteries, etc. Germany has developed a new technology for laser welding of flat glass.

Welding Methods

Resistance welding is used to weld thin metal parts by clamping the welded workpiece between two electrodes to melt the surface contacted by the electrodes through a high current, i.e. by resistive heating of the workpiece to implement the welding. The workpiece is easily deformed and resistance welding is carried out by welding both sides of the joint, whereas laser welding is carried out from one side only. The electrodes used in resistance welding need frequent maintenance to remove oxides and metal adhering from the workpiece, while laser welding of thin metal lap joints does not touch the workpiece. In addition, the beam can also enter areas that are difficult to weld with conventional welding and welding speed is fast.

Argon arc welding is the use of non-consuming electrodes with shielding gas, commonly used to weld thin workpieces, but the welding speed is slower, and the heat input is much greater than laser welding, prone to deformation.

Plasma arc welding is similar to argon arc, but the torch produces a compressed arc to increase the arc temperature and energy density, which is faster and deeper than argon arc welding, but inferior to laser welding.

Electron beam welding relies on an accelerated stream of high energy density electrons hitting the workpiece, producing a huge amount of heat in a small dense area on the surface of the workpiece, creating a "small hole" effect and thus implementing a deep melt weld. The main disadvantages of electron beam welding are the need for a high vacuum environment to prevent electron scattering, the complexity of the equipment, the size and shape of the welded part is limited by the vacuum chamber, the quality of the welded part assembly requirements are strict, non-vacuum electron beam welding can also be implemented, but due to electron scattering and poor focus affects the results. Electron beam welding also has magnetic deflection and X-ray problems, as electrons are electrically charged and can be affected by magnetic deflection, so electron beam welding workpieces are required to be demagnetised before welding. Laser welding does not require a vacuum chamber or pre-welding demagnetisation of the workpiece, it can be carried out in the atmosphere and does not have X-ray protection problems, so it can be operated in-line and can also weld magnetic materials.

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