Laser Welding Process History
Laser welding is a method of welding metal, which is designed for particularly precise connection of products. It is often used in the presence of a complex configuration of the contact of the elements that are being welded. This technology is not used so often, but still it has a lot of positive features.
With the help of it, you can get an aesthetic, smooth and smooth seam without deformed, curvatures. Welding is suitable for joining products made of stainless steel, aluminum and even silver. Of course, these are not all the characteristic qualities of this type of welding, there are other features that deserve special attention.
- General characteristics
- Laser welding technology
- Advantages and disadvantages
- Conditions and methods of laser welding
- Types of lasers
- Application of hybrid installations
- Features of welding of thin-walled products
- Application of laser welding for glass and plastic products
- Models of laser welding machines
- How to make a laser cutter for a garage
- Possible seam defects
Laser welding of metals is performed using special equipment. This method appeared not so long ago, but it has managed to gain high popularity.
It is used in various fields of industry to create a strong all-in-one connection. This welding method has high accuracy, good performance and excellent connection quality.
Heating and melting in the working area occurs using a laser beam. The luminous flux generated by the laser is monochrome. All waves have the same length indicators.
This is what makes it much easier to control the flows, which is done by focusing lenses and deflecting prisms. The laser shows the phenomenon of wave resonance, which increases the starting power many times.
All these properties help to understand what laser welding is. During this technology, various welding machines can be used – semi-automatic, automatic and even robotic, which carry out work without the presence of a person. Each of them delivers a laser beam that heats and melts the selected area of the metal product.
The principle of operation of laser welding is based on the following properties:
- coherence. This indicator is based on the relationship of the phases of the thermal field of the laser beam in different zones;
- monochromaticity. This property is characterized by a small width of the spectral lines that are emitted by the source;
- orientation. During the welding process, the beam is not scattered when it moves from the source to the product being welded.
Thanks to these indicators, the power of the laser beam increases, it provides accurate measured melting and evaporation of metals in the welding zone.
The source can be at some distance from the welding zone, and the presence of a vacuum is not required in the area of the welding laser bath.
So how does laser welding work? When connecting products using a laser beam, the following processes are observed:
The elements that are prepared for connection are tightly connected to each other along the line of the future connection. Next, a laser beam is aimed at the joint area.
The generator turns on. During this, the uniform heating, melting and evaporation of particles on the edges begins.
Due to the fact that the cross-section of the laser beam has a small size, the molten metal fills all the micro-dimensions and defects of products that fall within the range of the laser beam.
Important! Laser welding has a positive feature – during it, a welded joint with a high density is formed. But porosity and other defects that are inherent in other welding methods are absent during this technology.
Due to the fact that the laser beam moves along the connected surfaces at a high speed, metal oxidation does not occur during the welding process. With the help of the beam, you can make two types of seam – continuous and intermittent. Using the first option, stainless steel pipes are welded, where high tightness is required. The second type is used when welding small structures that have surface damage.
Advantages and disadvantages
The advantages of laser welding have made this technology popular and in demand. But it also, like other welding works, has negative aspects that must be considered beforehand.
Among the advantages of welding, we can distinguish:
- Laser beam welding can be used for a variety of materials-from metals and magnetic alloys to thermoplastics, glass, ceramics.
- There is a high accuracy and stability of the trajectory of the heating spot. Small size of the welded joint.
- This is what makes it invisible.
- There is no heating of the near-ear region. As a result, minimal deformation of the welded parts is observed.
- During heating, no combustion products are formed, X-ray radiation does not appear.
- High chemical purity of the welding process. This is due to the fact that additives, fluxes, and electrodes are not used during welding.
- It is suitable for welding in hard-to-reach places, can be used at a great distance from the laser location zone.
- It can be used for welding elements that are located behind transparent materials.
- Quick reconfiguration when switching to the manufacture of a new product.
- The welds are of high quality and strength.
Despite the fact that laser welding is a popular method that is excellent for repairing the car body, for working with various structures, metal products, it is still worth considering the pros and cons of the technology. As we understood, it has quite a lot of advantages, but do not forget about the disadvantages.
Special attention should be paid to the following negative qualities:
- laser welding equipment has a high cost. Also, accessories, spare parts are quite expensive. For this reason, this technology is used only in production facilities, enterprises. And some craftsmen resort to making laser welding with their own hands, but this requires some knowledge, and it is also necessary to have diagrams, drawings, instructions;
- laser-arc welding has a low efficiency index. For solid-state alloys, it is 1%, and for gas alloys it can be 10 %;
- dependence of the efficiency of the welding process on the reflectivity of the workpiece;
- high requirements for the qualification of service personnel;
- special requirements for the premises where the laser equipment is located. This applies to the indicators of vibration, humidity and dustiness.
Conditions and methods of laser welding
Laser welding of stainless steel, alloys and materials must be carried out in accordance with certain features. To get an increased beam power, its precise focusing is required.
At the moment when the beam intensity indicators become higher than the maximum value, it is passed through the central area of the front mirror and then through the system of guiding prisms to the working area.
Laser welding of stainless steel and other metals can be carried out at different locations of the products being welded.
The depth of penetration of the metal structure can be adjusted in a wide range – from surface to through. The working process can be carried out by a continuous beam or intermittent pulses.
Please note! Laser pulse welding is suitable for joining and processing products made of thin sheet metal. In addition, this technology can easily weld profiles with a complex design and parts with a large thickness.
It should be borne in mind that laser welding of aluminum, copper, stainless steel and other metals can be carried out in several ways:
Butt method. It does not require additives, flux. There may be a joint between metal products, but its size should not be more than 0.2 mm.
The same indicator is considered the limit for focusing the laser beam on the joint. The welding process is carried out using a “dagger” penetration of metal surfaces to the entire thickness, while the intensity of laser radiation is observed up to 1 MW/cm2.
In these situations, the seam must be protected from oxidation, argon or nitrogen is suitable for this. But helium will be able to prevent breakdowns of laser radiation.
The overlapping method. During welding, the sheets are superimposed on each other, their connection is made by powerful radiation.
During welding, local clamping of products is applied. The maximum gap between the surfaces of metal products during operation should be no more than 0.2 mm.
Types of lasers
Laser welding of aluminum alloys, copper, stainless steel and other metals, materials can be carried out with different lasers. Devices can be solid-state and gas-type.
Each type is selected according to the purpose of the equipment application. But at the same time, do not forget about the important characteristics of each species.
Laser welding of copper, aluminum, stainless steel, silver, plastic and even glass is carried out with a solid-state laser. It requires the main component-a ruby rod, it can also be made of glass with neodymium. Usually this element is located inside the lighting chamber.
At the moment when light with a high power is supplied to the chamber with a certain frequency, the excitation of atoms occurs in the crystal at this moment.
All this leads to the emission of light, which has waves with the same length. The end parts of the rod element consist of reflecting mirrors. One of them is partially transparent. Energy is released through it in the form of laser radiation.
It is worth noting! Solid-state lasers have a low power. This indicator can vary from 1 to 6 kW.
Gas-type lasers are considered more powerful and productive devices, in which a gas mixture acts as an active body. However, laser welding of titanium, copper, aluminum, stainless steel, which is carried out using these devices, has important features:
The gas is pumped from the cylinders by a pump. For this purpose, a gas-discharge pipe is used.
An electric current discharge occurs between the electrodes, which causes an energetic excitation of the gas mixture.
In the end zones of the gas discharge pipe there are special mirrors through which laser beams are passed.
When performing laser welding of frames, car body and other products, the electrodes are connected to a power source. The cooling process of laser devices is carried out by a water system.
But still, gas devices have a significant drawback – large dimensions. But laser units with transverse gas pumping have small dimensions.
The total power indicators of the equipment start from 20 kW and higher. Thanks to this, metals with a thickness of up to 2 cm can be welded at a speed of up to 60 meters per hour.
Laser welding of silver, copper, aluminum, titanium, stainless steel and other metals is performed under atmospheric conditions. It requires a vacuum, but at the same time there must be protection of the molten metal from the influence of air.
Gases, usually argon, are used for this purpose. Due to the fact that there is a high thermal power of the beam on the surface of the welded element, there is an increased evaporation of the metal. The vapors are ionized, as a result of which the scattering and screening of the laser beam occurs.
Laser welding of glass, plastics and products made of different metals, during which gas mixtures are used, is characterized by the fact that in addition to the protective gas, a plasma-suppressing gas penetrates into the welding area.
Helium is used as it, which is much lighter than argon, it will not scatter the laser beam. To simplify the process, many experienced welders often use combined gas mixtures that have plasma-suppressing and protective properties.
Features of gas-dynamic lasers
Gas-dynamic units have high power indicators. Carbon monoxide acts as the active body. It is heated to 3000 K and passed through the Laval nozzle. At the outlet of the nozzle, there is a rapid decrease in pressure, and a gradual cooling of the gas mixture.
Application of hybrid installations
Laser welding of the car body, various structures with thick elements and components with a gap is carried out using additional additive materials.
For these purposes, a wire feed is used, which ignites an electric arc. Thanks to this, the space between the plates is filled and a connection with high strength is created.
Important! When conducting laser welding of a car, thick metal structures, the welding bath is protected by blowing with an inert gas, which is supplied through a nozzle fixed next to the laser head.
Laser welding of the body and other products with a high thickness is performed on a table or stands from the equipment. The process is carried out in several stages:
At the initial stage, the metal is cleaned of scale, oil stains, signs of water, moisture.
Then the parts are tightly fitted butt-to-butt.
Chemical etching of the surface of the metal product is performed.
Laser welding is configured with the required parameters depending on the type of metal being welded.
Next, the head from the welding equipment is moved to the start line of the connection, the welding start button is pressed.
During the welding process, it is necessary to constantly monitor the penetration of the beam into the joint area.
Features of welding of thin-walled products
The main advantage of laser welding is its variety. Suitable devices and devices can be selected for each type of work. But all when choosing them, it is worth relying on the type and features of the materials that will be welded.
Usually, solid-state lasers and gas-based devices are used for thin-walled products. But all the first option is considered the most preferable.
Laser welding of small thicknesses is always performed using solid-state lasers. It is suitable for working with small products. Often these are microelectronic elements, for example, thin leads made of wire with a diameter of 0.01 to 0.1 mm.
Often, a solid-state installation performs spot laser welding using a solid-state laser device. But it is suitable for products made of foil structure with a point diameter of 0.5-0.9 mm. Using this method, a sealed cathode connection is made on the kinescopes of modern televisions.
The connection of small and thin-walled products is carried out at a minimum power. If welding is performed in pulse mode, then it will be necessary to increase the pulse duty cycle and reduce its duration. But in continuous mode, it is necessary to increase the speed of the laser.
Application of laser welding for glass and plastic products
Laser welding of plastics and glass is performed using solid-state installations. They have a simple device – two electrodes are installed in the reflecting tube, and in the space between them there is a mixture of ionizing gases.
Please note! Solid-state equipment is often used in the repair of glasses made of plastic and glass. It has become particularly popular when welding frames, this is due to the fact that this process does not require the use of solder.
Welding of plastic and glass products is performed in the same sequence as the connection of metal elements:
- the surfaces of the parts to be welded are thoroughly cleaned of dust, stains, and various contaminants;
- then the installation and the electrode are prepared for subsequent work;
- the focusing lens is adjusted. If a defocused lens is used, the laser beam will be blurred and it will not be possible to create a local melting of the metal. A properly focused beam should have a round shape;
- the required value of the welding power is set.
Models of laser welding machines
We have considered what laser welding of metal is and how it is carried out, but it is still necessary to know the models of devices that are used for its implementation. Mobile and compact type equipment can be used for it.
The following laser devices are often used in industry:
Kvant-15 laser welding: The device is the most expensive and multifunctional. It is used in seam and spot welding technology for joining various metals and alloys with a penetration depth of up to 2-3 mm. It is also used for cutting tool, structural, high-alloy alloys.
LAT-s: This installation is used for laser welding and metal surfacing. It has high power and performance. The equipment can be equipped with coordinate tables, it is due to this that it is possible to process complex products.
MULE-1: This is a small-sized equipment that is used for laser welding and metal surfacing. With the help of it, soldering of silver and gold products can be performed. The use of laser welding in jewelry makes it possible to easily weld with high accuracy. Even the connection of the frames of plastic glasses is allowed.
Manual laser welding is carried out using devices:
WELD-WF: A portable device suitable for welding hard-to-reach places. Its device includes a manipulator that connects to the fiber. The power is 1.5 kW;
CLW120: Manual unit with low power. It is suitable for the jewelry field, which requires maximum precision. It can also be used for spot laser welding. The power is 10 kW.
How to make a laser cutter for a garage
Many people are interested in how to do laser welding yourself? Since the equipment is quite expensive and not everyone can afford it, you can try to make a simple cutting machine using a laser yourself.
With it, it will be possible to cut a variety of patterns on strong steels, cut metal components or connect simple steel products.
For manufacturing, you will need a laser pointer. Additional components will also be needed:
- a flashlight that runs on batteries;
- an old DVD-ROM from which you will need to extract the matrix with a laser drive;
- soldering iron and screwdrivers for tightening.
At the initial stage, it is necessary to completely disassemble the drive of the old disk drive for the computer. It is from it that you need to remove the device.
Everything should be done carefully and carefully, so as not to damage the main device. The disk drive must be a writing drive.
After the red diode is removed, it is he who burns the disk while recording information on it. With the help of a soldering iron, the diode fasteners are soldered. This element is very sensitive, it does not need to be thrown.
Next, the laser pointer is analyzed, how it is done can be viewed on the video on the Internet. The diode from the pointer is replaced by a red light from the drive. The body part is made of a flashlight. And rechargeable batteries will be needed to power the laser cutter.
Possible seam defects
Laser welding tests are often carried out at production facilities, which allow to prevent possible seam defects. But still, even proper preparation does not always protect against deformations, non-cookers and other unpleasant situations.
The following defects of laser welding are distinguished:
- Non-welding of the seam.
- Formation of pores and cracks.
- Swells, craters, welded shells.
- Extraneous inclusions.
These phenomena are often formed when the technology is not followed. The welder must always correctly set the settings in the equipment, depending on the metal being welded.
In addition, he must clearly control the process and monitor the movement of the laser beam along the welded area.
Laser welding technology is a popular method of joining different metals, as well as products made of glass, plastic and precious metals, which allows you to get a high-quality and strong connection.
But still, before starting it, it is necessary to carefully consider the important features, the principles of technology, on which the final result depends. In addition, in order for the process to be carried out correctly, it is necessary to have experience and skills.