, Welding is a method of joining and separating metals by means of an electric current and is based on the formation of an arc between the processing area — the first electrode, and the second electrode connected to the corresponding pole of the electric current, which is supplied to the handle area.
This method is used to connect parts, separate metals or cut them, drill and make cavities and holes, and weld layers.
- Electric arc
- Welding of metals
- Inverters: pros and cons
- Welding transformers
- Welding Rectifiers
- Semi-automatic machines: characteristics
- The choice of the model
Arc welding is widely used, because thanks to this technology, it is possible to make an integral connection of metal parts, and the strength of the seam is the same as that of the solid material.
This circumstance is due to the continuity of the formed structures and the molecular bonds between the parts.
The device of the welding aperture the temperature of thousands of degrees Celsius is provided by an electric arc, which is essentially a short circuit between two electrodes located close enough to each other.
The voltage that is applied to the electrodes increases until there is a breakdown of the air that is the insulator.
Breakdown: the emission of cathode electrons. The electrons heated by the current exit and are directed to the ionized atoms of the anode.
Then there is a discharge, the air of the gap is ionized, plasma is formed, the resistance of the air layer decreases, the current increases, the arc warms up, and becoming a conductor closes the circuit.
The process was called” ignition ” of the arc. The arc is stabilized by setting the required distance between the electrodes and maintaining the power supply characteristics.
Welding of metals:
The choice of a good electrode and welding method is extremely important, since it depends on whether its mechanical properties will be similar to those of the base metal.
The weld pool must be protected from exposure to air to avoid oxidation of the metal. For this purpose, a special environment is created in the work area, which is achieved in two ways:
MIG-MAG technology, when argon, helium or CO2 is supplied from a special cylinder.
Burning of the electrode coating and the formation of a protective slag or slag-gas “dome”.
How to choose a welding machine In the process of gorenje electrode coatings bind and remove oxygen from the seam.
In addition, the substances contained in them help to ionize the arc, refine and alloy the seam metal.
In terms of the stability of the power supply, welding is a rather capricious process, because the required temperature regime is directly dependent on the current parameters.
The stability of the electric arc must be ensured. Only a stable arc will prevent the appearance of seam defects, especially during ignition and damping.
The more massive the parts to be welded, the deeper the melting must be, the larger the diameter of the electrode used, and the more force and power required to work.
The operator can often determine the current strength only by experience, sometimes it is regulated during the welding process, and sometimes it is rigidly fixed. Gorenje arc from a DC source is more stable, without interruptions.
When using direct current, there is no polarity, less metal splashes are formed,and the seam is obtained better.
Alternating current welding is somewhat more difficult, because to maintain the arc, the worker must have serious skills, high-quality welding in this case is difficult to achieve.
It is recommended to cook aluminum and its alloys with alternating current.
Different types of welding machines have different technical features, their pros and cons.
Inverters: pros and cons
Welding machine types of devices These are the youngest welding machines, their mass production was established only in the 1980s.
Rectifiers with a transistor inverter. In these sources, electricity changes its characteristics many times.
When the current is passed through the semiconductor, it is rectified, and then a special filter smoothes it.
The constant of the standard network frequency of 50 Hz is converted to the variable again, but with a frequency of tens of kilohertz.
After the frequency inversion, the current goes to the miniature transformer, where its voltage decreases and the power increases.
Then the high-frequency filter and rectifier begin to perform their work — direct current is applied to the electrodes to form an arc.
Increasing the current frequency is the main achievement of the inverter.
The advantages also include:
- The principle of operation of welding apparatuses is high efficiency (85-95%).
- The ability to power from a regular outlet.
- Long period of continuous operation.
- Wide range of current values.
- Smooth adjustment of current and voltage.
- The operating mode is controlled by microprocessors and control circuits.
- Protection against voltage surges.
- High-quality welded seam.
- The ability to connect materials that are difficult to weld.
- Increased electrical safety.
Disadvantages of inverters:
- High cost.
- Poor reaction to the penetration of dust into the housing.
- The electronics are sensitive to moisture and cold, which can lead to condensation.
- The probability of interference in the main network.
How to choose a welding machine Today, these are the most common welding machines, relatively inexpensive and simple in design, reliable.
The conversion of electricity is carried out by a power transformer of the standard frequency of 50 Hz. The current is adjusted by mechanically adjusting the magnetic flux in the composite core.
The primary winding is powered from the mains, the core is magnetized, and an alternating current of lower voltage (50-90 V) and greater force (100-200 A) is induced on the secondary winding, it forms an arc.
The fewer turns on the secondary coils, the lower the voltage and the greater the current.
- Low cost (two to three times cheaper than inverters).
- The simplicity of the design.
- Large weight and dimensions.
- Due to the alternating current, it is difficult to get a high-quality seam.
- The difficulty of holding the arc.
- Relatively low efficiency (no more than 80%).
- The inability to connect to the intra-house network.
Inverter welding network current in these devices does not change the frequency and is induced on the wingdings with a voltage drop.
After the conversion, it passes through another block of selenium or silicon rectifiers. Direct current flows to the electrodes. Thanks to this, the electric arc is very stable, without significant interruptions and jumps.
In most cases, fan cooling is required. Often, the devices have additional chokes to improve the characteristics of the outgoing current, which is smoothed and filtered.
Complete with rectifiers can be protective, measuring and start-up equipment. Here, the stability of temperature and current is important, so wind relays, thermostats, fuses, automatic machines are installed. Three-phase rectifiers are the most common.
Advantages of welding rectifiers:
- High-quality seam.
- Ease of maintaining the arc.
- Minimal spatter of the additive material.
- Large melting depth.
- Smaller dimensions and weight in comparison with AC transformers.
- The possibility of welding cast iron, non-ferrous metals, heat-resistant steel.
- Disadvantages of the model are high cost.
- The need for careful monitoring of the state of the cooling system.
- The absence in most cases of the possibility of power supply from the household network.
- The efficiency is less than that of an inverter.
- A relatively complex design.
The welding wire is fed by a special mechanism to the working area, where it is melted in the active gas and sent to the welding bath.
The gas displaces the air near the weld pool, protects the seam from oxygen. Carbon dioxide, argon, helium, and combinations of these gases are used for this purpose. With the use of flux wire, the gas can not be supplied to the working area.
- Easy welding of sheet metal parts.
- The quality of the seam, the possibility of obtaining a “short seam”.
- A wide range of materials to be welded.
- High performance.
- Wide range of settings and adjustments.
- High price.
- High cost of consumables.
- It is necessary to use cylinders or connect to a special network.
- The difficulty of working on the street, where the gas environment needs to be protected from deflation.
The choice of the model
The power of the welding machine is the mains voltage. It can be one-or three-phase.
For non-industrial applications, we recommend a 220 V device or a universal machine “220/380”.
Most machines can fail or stop cooking due to power surges. In this regard, inverters are equipped with protection against voltage surges.
In household units, the range is wider by 10-15%, and professional models need a voltage of 165-270 V.
No-load voltage. This characteristic determines the ability of the device to ignite an electric arc and maintain its gorenje.
For the arc to be excited, the voltage must be approximately 1.5-2.5 times the voltage of the stable gorenje electric arc.
Power: The data sheets often indicate the maximum power of the welding machine’s power supply, corresponding to the maximum network loads.
If the unit of measurement is kW, it means that it refers to the active power, if kVA – to the total power, which is usually higher due to the correction factor.
The actual power is determined by the current that the device is able to give out. This indicator determines the thickness of the metal to be welded and the maximum diameter of the electrode.
Protection class: The passport must contain a 2-digit I. P. code. The index of the average welding power supplies is IP21-IP23.
The deuce says that objects with a thickness of more than 12 mm will not penetrate inside the case. The second number indicates protection from moisture-1-means that water drops falling vertically on the casing will not cause harm; 3 means that even at an angle of 60°, water will not penetrate the body of the device. But cooking in the rain is forbidden!
Patriot welding machine Temperature range: According to GOST, manual welding can be carried out at a temperature of-40-40 ° C.
However, not all welding machines can be put into operation at temperatures below zero degrees. Most often, problems occur with inverters, in which, at subzero temperatures, the overload indicator simply lights up, and the welding machine turns off.
Operation from the generator: This function is useful for working in the field. Not all devices can be powered by household generators with internal combustion engines.
Many power sources make it easier to hold the arc: “Anti-sticking on shutdown”, “Hot start”, “Forcing the arc”, “Ignition on the rise”.
It is useful to pay attention to the indication of parameters, functionality, breadth of working adjustments, overload protection, marking quality, electrical safety, completeness, ergonomics, maintainability.
It is recommended to purchase a device with the maximum technical characteristics in the passport.