Plasma welding - video on how to weld metal using plasma welding Multiplaz

Plasma welding will increase efficiency and also reduce the time required for metal cutting. Devices for this type of welding are gaining increasing popularity among equipment used for plasma welding. You can watch the video by following the link on our website.

Many companies around the world are developing this market segment, producing both the devices themselves and related accessories. It also released its devices in Russia, which in all respects are worthy competition to foreign ones. Welding is carried out by machines, some of which are capable of cutting.

What is plasma welding

The emergence of new types of metal alloys in modern technologies has forced specialists to develop new techniques and drawings of equipment for welding products made from them. Since many modern metals do not lend themselves well to traditional welding techniques. As a result, a new plasma method for welding metal samples has emerged, which is successfully used in various repair and installation processes.

The main differences between plasma welding technology

Plasma welding is somewhat reminiscent of argon welding, but there are characteristic differences. For example, it has an operating temperature that is much higher. The welding arc can have a temperature from 5 to 30 thousand degrees. Thanks to this quality, using plasma welding technology, it is possible to connect elements of building structures that cannot be welded with homemade and standard factory equipment, the arc temperature of which does not exceed 5 thousand degrees.

Operating principle of plasma welding

The essence of this welding: by exposing the metal surface to a flow of ionized gas conducting an electric current, the metal melts. When the arc is heated, the gas undergoes ionization, the level of which increases with increasing gas temperature. A plasma jet, which is characterized by ultra-high temperature and increased power, is formed from an ordinary arc after compression, injection into the arc formed by a plasma-forming gas, which is usually argon (hydrogen and helium are rarely used).

The kinetic energy of the chemical elements present in the gas during the ionization process significantly increases the thermal energy of the plasma arc. Moreover, the arc, when compared with a conventional one, has the ability to significantly increase the pressure on the metal surface due to a decrease in its own diameter.

What does it consist of?

A plasma welding machine consists of several components: a power source, a special welding torch, a cathode and cable packages. Let's take a closer look at them.

Power supply

The previous generation plasma welding machine used a conventional transformer as a power source. Such a source itself was rather large and heavy, and therefore significantly increased the final dimensions and weight of the apparatus. As a result, old-style plasma devices were bulky and very heavy, which caused many problems.

Fortunately, progress did not stand still and over time, alternative power sources using transistors appeared. They began to be used in inverters, semi-automatic devices and, of course, plasma devices. Thanks to this breakthrough, it was possible to design compact and lightweight devices, which also became even more functional compared to their previous “brothers”.

The modern power supply, powered by IGBT transistors, ensures extremely stable arc burning and allows you to accurately and quickly adjust the welding current using a single handle. Professional plasma machines are equipped with additional functionality such as non-contact ignition of the arc or a pilot arc mode when welding at a low current value.

Welding torch

A welding torch is an essential component for plasma welding and cutting. Shielding gas is supplied through it, a plasma arc is formed through it, and a cathode is installed in it. There are many types of burners, all of them differ in their design and capabilities. In most cases, the torch is selected in accordance with the power of the welding machine.

Low-power and medium-power burners can be used manually. And burners for high-current devices are installed on a special robotic manipulator.

Cathode

The cathode is used to transmit current and can be made of various materials. In devices intended for household and semi-professional use, tungsten or copper cathodes doped with hafnium are used. They are the safest for the welder’s health. Professional-level plasma torches and plasma cutters can use beryllium or thorium cathodes. They can be dangerous for the welder because they emit harmful fumes. To reduce the negative impact, it is necessary to provide powerful ventilation of the workplace.

Cable package

The plasma welding machine must be connected to the torch. A special cable package is used for this. It consists of two hoses (for supplying shielding gas and for supplying working gas), two hoses for water supply, as well as current supply cables for the starting spark and for the control circuit. All of these components are housed in one large bundle-type hose, hence the name cable bundle. Despite the rich “filling”, this cable package bends perfectly and can be used without fear of breaking all the components inside.

Advantages of plasma technology

• Unlike gas welding, the cutting speed of metal 5-20 centimeters thick using the plasma method is three times higher.
• The high precision of the seams obtained as a result of melting and welding of metal, the quality of the work performed practically eliminates the need for subsequent processing of the edges of the products.
• Plasma cutting is used to process almost any type of metal. For example, you can cook samples from Zaporozhye steel, cast iron, copper, aluminum.
• When welding, the metal is not subject to deformation even when it is necessary to cut out complex shapes. The plasma welding technique makes it possible to cut on an unprepared metal surface, for example, rusty or coated with a layer of paint. In this case, the paint in the working area of ​​the plasma arc does not ignite.
• There is no need for argon, acetylene, or oxygen. This significantly reduces financial costs.
• High degree of safety of work, since gas cylinders are not used. This indicator indicates the environmental friendliness of the process.

Specifications

Plasma cutting of metals provides the following technical characteristics:

Thickness of sheets and blanks. To process workpieces of different thicknesses, the current strength, gas flow rate and distance between the electrodes are adjusted. This parameter significantly depends on the thermal conductivity of the metal: as it increases, the thickness decreases and vice versa. Small portable machines are capable of cutting metals up to 10-12 mm thick, and powerful equipment - up to 100 mm

It is important to consider that plasma cutting is effective when cutting steel workpieces with a thickness of no more than 50-60 mm, aluminum sheets - up to 120 mm, copper products - up to 80-85 mm, and cast iron - up to 90 mm. Special combined equipment provides cutting of metals up to 200 mm thick. Complex, shaped cutting is performed with workpiece thicknesses up to 100 mm. Sheet sizes

They depend on the dimensions of the machine’s work table. The modern equipment used allows processing sheets with a width of 2.5–3 m (gantry machines - up to 4 m) and a length of 4–5 m (large-sized machines - up to 6-7 m). Sheet movement speed. It depends on the shape of the workpiece and the thickness of the sheets. The speed of sheet movement is usually adjustable within the range of 50–800 mm/min. Modern CNC equipment is capable of cutting thin sheets at speeds of up to 20,000 mm/min. Most often, the following modes are set: for sheets up to 100 mm - up to 5000 mm/min, for shaped cutting - about 200–250 mm/min. Cutting angle. Most often, plasma cutting is used for perpendicular cuts. Without increasing the quality of the edges, the angle may deviate from perpendicular by 20–50°. Roughness. In the cutting zone it is standardized by GOST and can correspond to classes 1,2 or 3.

Complex, shaped cutting is performed with workpiece thicknesses up to 100 mm. Sheet sizes. They depend on the dimensions of the machine’s work table. The modern equipment used allows processing sheets with a width of 2.5–3 m (gantry machines - up to 4 m) and a length of 4–5 m (large-sized machines - up to 6-7 m). Sheet movement speed. It depends on the shape of the workpiece and the thickness of the sheets. The speed of sheet movement is usually adjustable within the range of 50–800 mm/min. Modern CNC equipment is capable of cutting thin sheets at speeds of up to 20,000 mm/min. Most often, the following modes are set: for sheets up to 100 mm - up to 5000 mm/min, for shaped cutting - about 200–250 mm/min. Cutting angle. Most often, plasma cutting is used for perpendicular cuts. Without increasing the quality of the edges, the angle may deviate from perpendicular by 20–50°. Roughness. In the cutting zone it is standardized by GOST and can correspond to classes 1,2 or 3.

The machines used provide high accuracy and high-quality cutting regardless of thickness by adjusting the parameters of the plasma flow. Does not affect the quality and presence of paint and other protective coatings (for example, galvanizing), as well as dirt and dust.

Types of plasma welding

Depending on the tools used, plasma welding can be:

• on currents of any polarity;
• with penetrating/non-penetrating arc;
• point, pulse;
• automatic, semi-automatic, manual;
• with and without filler wire.

In the case of using low currents, the connection technique is called microplasma, which is the most popular. This scheme is in demand in the production of structures up to 1.50 mm thick - this is usually the connection of thin-walled pipes, containers, welding of small elements to heavy structures, the manufacture of jewelry, thermocouples, as well as welding of foil samples. Thin-walled metal products are also welded using electric rivets.

If the connection is made using filler wire, then solid wire (cored wire) is used.

Advantages and disadvantages

The advantages of the plasma method include:

1. Availability. The plasma torch can be installed on basic welding machines.
2. Uniformity of the welded joint. Due to the high temperature, a uniform, thin seam is formed in the treated area.
3. Ability to control metal penetration.
4. High performance. The high speed of seam formation reduces the labor intensity of the work.
5. Wide scope of application. The universal method is used to join workpieces made of other materials.

The negative qualities of this welding method include:

• high cost of the plasma torch and work;
• difficulty in execution (the welder is required to have special skills);
• the need for additional care of the devices (you need to regularly clean the plasmatron, replace the electrode and burner);
• the need for a continuous supply of argon to the apparatus;
• the need to cool the main equipment components;
• high energy consumption.

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Features of microplasma connection

Plasma welding comes in three options, depending on the current used during operation:

• microplasma welding technology on currents - 0.1A-25A;
• connection with medium currents - 25A-150A;
• connection with high currents - 150A and above.

The first variation is more popular. In the process of connecting metal samples using a low-ampere current, a pilot arc is formed. It burns uninterruptedly between a water-cooling nozzle made of copper and a two-millimeter cross-section tungsten electrode.

The main arc is formed after bringing the plasmatron to the surface of the metal sample being processed. The gas that forms the plasma is supplied through a plasma nozzle, the diameter of which can be 0.5-1.5 millimeters.

The maximum diameter of the plasma arc is 2 millimeters. Thanks to this indicator, quite a large amount of thermal energy is generated on a relatively small element of the workpiece. This type of welding, like welding with electric rivets, is most effective for metal samples whose thickness is less than 1.5 millimeters.

Argon is used to form plasma, a protective gas environment, using this technology. Depending on what metal or alloy the sample is made of, additives can additionally be used to increase the efficiency of the “plasma”.

A plasma welding machine is capable of joining metal products in different modes. The range of welding uses is quite extensive:

• fastening membranes to large-scale structures;
• production of thin-walled pipes and containers;
• welding foil;
• jewelry manufacturing;
• many other connections.

Schematic diagram of the device

A typical drawing of a homemade plasma cutter shows the following elements:

1. Electrode. This component receives voltage from the power supply, due to which the gas environment is ionized. To produce the rod, refractory metals are used - titanium, hafnium, zirconium.
2. Nozzle. The unit allows air to pass through and creates a directed stream of ionized gas.
3. Cooler. Removes heat from the nozzle, preventing overheating of the plasma torch.

We recommend reading: How to choose a gasoline welding generator

The device, assembled according to a standard scheme, has the following operating principle:

1. Pressing the “Start” button turns on the relay. It supplies electricity to the control unit.
2. The second relay directs current to the inverter. After this, the burner purge system is turned on. A powerful air stream enters the chamber, cleaning it.
3. The oscillator is activated, which ionizes the working gas circulating between the anode and cathode. At this stage, the primary arch appears.
4. When the torch is brought close to the metal, a discharge occurs. A cutting arc is formed.
5. Using a reed switch, the ignition current supply is turned off. If the cutting arc disappears, it is resumed.
6. After cutting is completed, the relay turns on the compressor. The air it pumps cools the nozzle and removes metal combustion products.

DIY welding

This type of metal welding was not initially used at home, as it required a highly qualified welder. Today, thanks to the improvement of the methodology itself and the equipment used, there are welding units that can be used at home. The working method is very simple. To perform welding work, you need to purchase the appropriate equipment, filler wire, electrodes, and read the operating instructions for the device.

Tips for Beginners

• The electrode must first be sharpened to a cone-shaped shape, and the sharpening angle should be a maximum of 30 degrees.
• Important! Correct installation of the electrode. Its axis must coincide with the axis of the nozzles for gas formation.
• The welding joint is subjected to similar processing as when welding with argon.
• It is imperative to clean and then degrease the edges of the workpiece.
• It is necessary to ensure that there are no gaps larger than 1.5 millimeters.
• Additionally, the tack areas are cleaned; they must be of the same quality as the weld.
• You can start welding work.
• Do-it-yourself welding is carried out using direct current. Its value must be within the specified range.
• Before welding the samples, gas is supplied 10-15 seconds, which is turned off after 15 seconds after the arc breaks.
• During operation, the plasma torch should be located from the workpiece at a distance of less than one centimeter.
• It is recommended to hold the welding arc until the seam connection is completely completed.
• Do not overheat the metal during welding. After reaching the critical point, welding is suspended, the metal sample is cooled, after which welding work can be resumed.
• The gun (torch) must be moved evenly, then you can count on obtaining a high-quality welded joint.

Good Chinese plasma cutters

The design of an air plasma cutting machine is not so complex that it can be reproduced with errors.
At least this is what those who bought cutters in China say. Products from this country are an excellent choice if you have a limited budget. And when it comes to Chinese models, people most often remember the inexpensive CUT50p. The price of such a compressor is around $350. It is capable of delivering a current of 10 amperes, weighs 13 kilograms and has an operating mode of 60%. (After 6 minutes of work, take a break for 4 minutes.)

The advantages to note are the following:

• Light burner;
• Availability of consumables included;
• Everything is collected in one building. (this plasma cutter has a built-in air compressor);
• Power supply 220/110 volts;
• Good “features-price” ratio;

The disadvantages are obvious: if the transformer winding burns out, or the device is damaged, it will hardly be possible to return it.

But if you decide to purchase an inexpensive plasma cutter with a ready-made compressor from China, it is better to pay attention to the DWT company. It is an international company with headquarters in China and Switzerland. The company has representative offices in Russia, which means there is somewhere to turn for service.

Inverter plasma cutter DWT CUT-40

A basic inverter plasma cutter from DWT can be purchased for $200 and up.

Welding machine "Gorynych"

Multifunctional welding "Gorynych" is one of the most popular welding units of domestic production. This is a really high-quality tool that allows you to do welding work at home with your own hands. It should be noted that the Gorynych line of equipment includes devices of various capacities (8,10,12A).

For household work, an 8A device is perfect; a 10-amp device is characterized by price/performance, but more powerful 12A equipment is already considered professional. The welding unit of the Gorynych brand is quite popular both in Russia and in Ukraine (in particular, in Zaporozhye), and in Belarus.

How to cut a round blank

An even circle can be easily cut using a CNC plasma cutter.
But it is quite difficult to do this with a hand cutter. A plasma cutter compass solves this situation. You can buy a compass for a plasma cutter, but if you have a lathe, you can make it yourself. The design is based on a magnet, which is attached to a metal table or directly to the workpiece (if it is magnetic).

A key with a bearing or bushing is installed on the magnet. A movable guide with a removable core at the end is attached to the bearing.

The parts of the future workpiece are marked with a core, and then a plasma cutter is inserted in place of the removable core, and the movement is repeated.

A plasma cutter compass also eliminates the need to maintain a 90-degree angle. And plasma cutting, done by yourself, will no longer seem as complicated as before.

The ruler for the plasma cutter with magnets has a similar design. The only difference is that it is intended for straight cuts, and not radial ones, as is the case with a compass.