How to Choose Welding Machine Types.
The structure and operation.
A welding machine is an electrical device with which welding is performed. It is this process that provides a long-lasting and reliable fastening of metal parts. With the help of welding, a huge number of works are performed in various fields, ranging from microelectronics to the creation of multi-ton structures.
Among the main advantages of electric welding is a reliable and fast connection of materials at a minimal cost.
If necessary with the help of this device you can even cut the metal. In recent decades, they have been manufactured using electronic components.
Thanks to this, their weight and dimensions were significantly reduced, which allowed them to expand their use.
Types and types
Welding equipment is characterized by a wide variety, which is due to the constant development of welding production, the creation of new techniques and methods of welding.
Based on the design features, including the principle of operation of the devices, the following types can be distinguished:
Welding straightener. It is equipped with a block of semiconductor diodes, as a result of which the current passes from AC to DC.
The main advantages are minimal splashing, welding of high-quality seams. It is used for welding ferrous and non-ferrous metals, cast iron, aluminum, steel.
The welding transformer. It works thanks to alternating current. There are several types – with increased and standard magnetic scattering. The welding process is quite time-consuming due to its heavyweight.
Semi-automatic welding machine. It is used for welding operations in the gas sector. Welding inverter. These are light and compact installations.
The base metal fusion welding equipment can perform the following operations: Fusion
- Arc welding and surfacing.
- Gas welding.
- Electro slag welding and surfacing.
- Electron beam welding.
- Surfacing and cutting.
- Special types of welding.
According to the degree of mechanization, welding machines can be:
- Manual ones.
The following classification of welding machines is as follows:
- Household items: They are distinguished by low productivity, they are not adapted for long-term work. However, their scope of application is very wide, such a unit is used for welding arches, boilers, pipes, and so on;
- Professional: They are distinguished by their heavyweight and dimensions, they operate from a 220 or 380 W network. Most of these models are equipped with special wheels to facilitate movement. They are used in many areas of construction, workshops, gas pipeline installations, factories, and the like.
The device of each inverter model may have a number of features, but most of the technical components are repeated. The equipment board mainly includes the following elements:
Each welding machine is a kind of energy converter. The unit receives an electric current from the network, then reduces its voltage, increases the current to the required value.
In this case, there is a change in the frequency of the current or a direct current is formed from the alternating current.
The only exceptions are devices where the electric arc is formed from the energy of generators with an internal combustion engine or batteries of accumulators.
The semi-automatic welding machine has the following device:
- A gas cylinder (argon or carbon dioxide).
- Gas supply hose.
- The cassette with the wire.
- The mechanism that feeds the wire.
- Wire feed line.
- Power supply.
- Gas burner.
- Gas equipment.
- The control unit.
- Control circuit wire.
Welding machine: The principle of operation
Consider a welding inverter. The whole essence of the inverter technology lies in the rectification of the alternating current of the network into a direct welding current with an intermediate frequency change.
A rectifier is an ordinary diode bridge. This unit receives an alternating current, which has an industrial frequency of 50 Hz.
The filter is made of a capacitor and a choke. The rectified current is routed to the filter, where it is smoothed out.
As a result, a direct current appears, the inverter converts it to an alternating current with a frequency of 20-50 kHz. At the moment, there are technologies that produce a current with a frequency of 100 kHz.
The power transformer reduces the high-frequency AC voltage to 25-40V. In addition, this element increases the current value to the required current for welding.
By converting high-frequency currents, the welding current reaches the required strength. Thanks to the multi-stage current conversion, it is possible to use a small transformer.
So to get a current of 160 A in the welding unit, you need to put a copper transformer weighing 18 kg. In the inverter, it is enough to put a transformer weighing 0.25 kg.
The high-frequency rectifier provides AC equalization. Then it is sent to the high-frequency filter, which allows you to get a constant welding current.
These energy conversion processes are controlled by a microprocessor control unit. This part of the welding machine is the most expensive element.
Today, inverter welding devices are manufactured using two different semiconductor technologies:
Their main difference is in the transistors, which differ in the switching current. MOSFET transistors, when compared to IGBT, are distinguished by their large size and weight, but their cost is lower. At the same time, they will need an order of magnitude more to ensure the same performance.
With the semi-automatic method, the welding machine works as follows:
The protective gas is directed to the electric arc zone, which allows you to protect the metal from the effects of air from oxidation and intruding.
The protective gas in this case can be active in the form of carbon dioxide or inert in the form of helium and argon. Working with metal in an inert gas environment is called MIG. Working with metal in an active gas environment is called MAG.
The welding wire is fed into the welding zone by means of an electric motor, a gearbox, and feed rollers.
An all-in-one connection is obtained in a gas environment under the action of an electric arc by melting the electrode wire that enters the burner.
The necessary surfaces are glued together using molten metal created by thermal energy. The result is a strong, long-lasting seam.
The semi-automatic welding method is so-called due to the fact that the wire is fed automatically, while the control of the feed, as well as the welding process, is performed by the welder manually.
The tip acts as a welding contact, it is supplied with power from the main unit. The current strength is selected according to the characteristics of the processed material. The feed rate is set using a gear or gearbox.
Advantages and disadvantages of welding machines:
The welding machine is widely used. It is often used in everyday life, as well as in professional activities.
Without such a device, you cannot do in many areas of production, industries and specialized workshops, for example, car repair.
These devices are used for reliable welding of metal frames and other critical structures in construction. Installation of oil pipelines and gas pipes is also impossible without the use of professional welding equipment.
Transformers are very heavy and cumbersome devices. They are highly sensitive to voltage fluctuations and consume a lot of electrical energy.
This is not a cheap device. You can cook them both butt-to-butt and overlap. An experienced welder is able to well weld even a critical seam with the help of a transformer.
By means of alternating current, only certain grades of cast iron and steel of “running” grades are usually welded.
Semi-automatic welding is ideal for both home and production. In our country, about 70% of all welding operations are performed by semi-automatic welding machines.
This is due to the ease of operation, high welding quality, and wide functionality of the equipment.
The semi-automatic welding machine is convenient for welding thin metal, especially car bodies. Semi-automatic machines are almost always found in car service companies.
The rectifiers have high stability of the electric arc, which makes it possible to weld high-quality and sealed seams of uniform depth. This significantly reduces the spatter.
The connection, thanks to the protection of the arc, is quite strong and uniform. There is no need for additional cleaning of products from drops of “splashing” melt. In this case, you can work with all types of electrodes.
The scope of application of rectifiers is much wider: non-ferrous metals (nickel, titanium, copper, their alloys), and steel (including high-alloy), and cast iron.
Inverters. Recently, they have been very popular. They stand out for their functionality, power, compactness, and low weight. This welding machine is optimal for beginners.
Specialists can use them to increase their productivity. They are used everywhere because they allow you to weld even thin-walled metal.
You can cook non-ferrous and ferrous metals of any thickness in different positions in space with inverters. All types of electrodes are used.
How to choose a welding machine
The welding machine can be three-phase or single-phase. For domestic use, you need a 220 V device. You can also choose the universal unit “220/380”.
No-load voltage: Determines the ability of the device to initiate and re-ignite the electric arc, including to maintain its grange. It is believed that the higher the idle voltage, the better.
Power: You should choose devices with at least a small margin of power, about 30%.
Protection class: The welding machine must be standardized and have a two-digit IP code, for example, IP23. Deuce — objects with a thickness of more than 12 mm will not get inside the case.
The second figure is protection from moisture: The number 3 means that water, even at an angle of 60 degrees, will not be able to get into the body of the unit.
Many modern devices are equipped with additional options: “Anti-sticking on shutdown”, “Arc forcing” or “Hot start”. They will help with welding, especially for a beginner.
The welding machine can be used as a car battery charger. However, it must be borne in mind that such a device must have an adjustment for lowering amps and volts.
If you have such a device, you need to switch it to the start-charger mode. You should set 12 volts at the output, and set the amps to 1 to 20 of the battery power (if the power is 60A, we charge 3A).
Charge the battery for about 40-60 minutes. This is quite enough to start the engine. For a thorough charge, you will need to reduce the current by half and increase the time by 3 times.
WHAT GAS IS USED FOR SEMI-AUTOMATIC WELDING
The semi-automatic welding machine makes it possible to increase the productivity and quality of work.
The equipment does not involve the use of traditional electrodes. Instead, a special filler wire is used, which is wound on the coil.
The advantage of this approach is that the specialist does not have to tear the seam to change the rod. The operation is performed continuously, preserving the integrity of the seam and saving time.
In addition, the equipment allows you to weld workpieces of different thicknesses: from 0.2 mm to several centimeters. At the same time, the welder can work with workpieces made of different materials or alloys.
In order to take advantage of all these advantages, gas is required for semi-automatic welding. It will prevent the penetration of atmospheric moisture and other elements contained in the air into the welding bath.
- What gas is needed for semi-automatic welding
- Welding mixture for semi-automatic machine
- Technology of work execution
- Features of welding under gas
- The main advantages of semi-automatic gas welding
What gas is needed for semi-automatic welding
The technological regulations for the operation of semi-automatic welding provide for the use of an inert or active gas as a flux.
The active one reacts chemically during welding and changes the physical and chemical properties of the weld.
The protective gas does not react but protects the working environment from oxidizing processes. This method is especially relevant in cases of welding of aluminum alloy workpieces, which are quickly oxidizable.
The most common inert gases are helium and argon. The active group consists of common elements: carbon dioxide (CO2), oxygen, nitrogen.
The most popular connections:
- a mixture of argon and carbon dioxide. The inert-active medium minimizes the amount of spray
- composition of helium and argon. An inert environment that allows you to increase the arc temperature
- argon-oxygen gas environment. An inert active compound that is used when working with alloy and low-alloy steel
- carbon dioxide combined with oxygen. An active environment is used to improve the performance of semi-automatic equipment.
Welding mixture for a semi-automatic machine
When choosing a mixture for a semi-automatic machine, the specialist takes into account the following criteria:
- the type of material of the workpieces
- the diameter of the wire used
- the optimal thickness of the weld.
In practice, to select a mixture, it is enough to compare the data given in special tables. Here, the optimal variants of compositions for working with specific materials are already selected, taking into account the technological features of the process.
An experienced welder also takes into account the concomitant effects of using a particular gas mixture. For example, the use of carbon dioxide makes it possible to reduce the spatter. Therefore, they are often chosen for the formation of ceiling joints.
Technology of work execution
There is no fundamental difference from arc welding, since it is based on the same physical and chemical processes.
A potential difference is created between the electrode and the working surface, which makes it possible to form an electric arc.
It is heated to a temperature that is sufficient to melt metals. The molten filler wire binds to the workpiece body at the atomic level. After cooling, a solid structural element is formed.
The joint strength of the additive and the body of the workpiece is approximately 90% of the index of the main structural material.
It is necessary to take into account the features that are characteristic of semi-automatic welding:
The filler wire is fed into the working area continuously through a special electrically conductive mouthpiece.
In this case, the material consumption can be adjusted manually by holding or releasing the feed button.
Instead of the usual flux in solid form, from the melting of which a gas cloud is formed, a ready-made gas mixture or a clean medium is supplied here.
Gas comes in all the time: both with an active and extinguished electric arc.
Thanks to this solution, the number of splashes is reduced, the arc performance is more stable, the welder’s labor productivity is increased, and, accordingly, the labor intensity of welding processes is reduced.
Features of welding under gas
The technique of welding with semi-automatic devices is practically no different from the techniques that are used in traditional electric arc welding.
With the help of semi-automatic machines, you can form horizontal or vertical seams, make a “tack”, make the joints sealed, make butt-to-butt, or overlap joints.
The formation methods remain exactly the same as when using the classic MMA-series devices.
Moreover, according to the general scheme, the optimal current and welding mode are determined – based on data on the joint thickness and the diameter of the electrode.
The only feature that almost all users note is the ease of connecting thin sheets of metal. Therefore, semi-automatic machines are most often used in body repairs and when welding metal structures made of thin sheets.
The main advantages of semi-automatic gas welding
- High temperature affects a limited area of the workpiece. Therefore, metals do not change their physical properties.
- No smoke in the work area. This greatly facilitates visual control of the welding process.
- Versatility. The technology is excellent for joining different metals: from aluminum and titanium to high-alloy structural steel.
- There are no restrictions on the spatial location of the workpiece. It is enough to adjust the power of the burner in order to put an inclined or ceiling seam.
- There are no restrictions on the minimum thickness. The technology makes it possible to work with sheets with a thickness of 0.2 mm. The maximum thickness of the workpiece depends on the skills of the specialist.
- It is not necessary to constantly clean the seams, even with multi-layer welding. The gas flux evaporates immediately after the mixture is stopped.
- High installation performance.