The choice of electrodes for welding is an essential point in such processes. Modern construction is rarely without the use of this type of work. And this applies to low-rise buildings (private and country houses) and to buildings of large commercial buildings.
The quality of welding, first of all, depends on the quality of the electrode, which was used for the work, therefore, it is necessary to approach its choice very carefully and responsibly.
Frameworks, containers, bases for garages and sheds, roofing elements - all the metal parts of these structures are interconnected by means of welding. In order for the seam to be high-quality, reliable and durable, it is necessary to have good equipment and consumables. Therefore, the choice of the electrodes for welding is one of the main in the preparation of works. The quality of the welded joint depends on how well the electrodes are selected.
There are several ways in which welding is performed:
Classification of types of welding.
- gas press;
- electric step.
But emit gas press and contact. In gas-press welding, acetyl oxygen flame is used. This method is chosen if it is necessary to achieve high performance of the work performed. Therefore, the industries where gas-press welding is used are oil and gas when laying trunk pipelines over long distances.
In contact welding, the process is carried out with the help of an electric current having a low voltage and a high amperage. This method is performed manually or mechanically. In this case, contact welding can be performed end-to-end, overlapped, parts can be applied to each other at any angle. The choice of the necessary equipment depends on the way the seam is adopted. As a result, the quality of work performed depends on the choice of the electrode and the welding units.
The choice of welding equipment should be approached from the specific conditions of work. Namely:
The supply voltage of the welder for domestic use is 220 V.
- Mains voltage. Under production conditions, it is 380 V, in household - 220V. With frequent power surges, it is more rational to use an inverter, which can protect the device from such effects and ensure reliable operation.
- Types and brands of metals that need to be connected. The direct current required for welding parts made of cast iron or non-ferrous metal can be provided by a welding generator or rectifier. The transformer is used for welding elements made of ferrous metal.
- Weight of the welding machine. Not always a lot of weight says about the duration of full use. Modern welding units, having a fairly low weight, can serve for a long time, performing all the tasks, in contrast to the weighty, obsolete models. This is especially true when frequent movement is required both between facilities and within the construction site.
- Operating time without possible overheating. This passport characteristic, which is indicated in the documentation for the equipment, indicates how long the device can work without interruption in order to avoid the threat of overheating. For example, if the figures are 5x20%, then this means the possibility of continuous operation for 1 minute, and then a break of 4 minutes is necessary.
- Output characteristics of the welding machine. At lower rates, the output characteristics of the current and voltage make it possible to perform work with a thick metal. However, in such devices the winding heats up faster, therefore, the thermostat can quickly cause the welding unit to shut off.
In addition to welding equipment in the process of welding 2 or more metal parts, the electrode participates. By choice, which must be approached responsibly. Not only the quality and durability of the weld, but also the amount of metal being deposited, its composition depends on it.Back to table of contents
The scheme of the welding electrode.
The manufacturer of welding equipment most often gives recommendations on which brands and types of electrodes can be used in conjunction with it. The wire that underlies the electrode must be of high quality initially. Further, the defining parameter of using a specific type of electrodes is its coating.
The choice of electrodes must be made on the basis of the parameters and characteristics of the surfaces being welded. It should be borne in mind that each of the types of electrodes has its own characteristics of use. If you use the wrong type of electrode, then the weld may not work.
Electrodes, according to regulatory documents, can be divided according to several parameters:
- destination use;
- type of coating and its thickness;
- mechanical properties and composition of the coating.
Wire coating can be:
Types of electrode coating for welding.
- Rutilov. It is made of titanium dioxide, which is used in powder form for spraying onto a wire. The use of this coating allows to obtain high-quality weld. Such electrodes contribute to stabilization during combustion. This brand is used to connect rusty or wet parts. The small amount of spatter produced during welding contributes to low metal consumption during work, the seam is neat. They are able to work both with the use of equipment operating on constant and alternating current. Their cost is quite high, but the breadth of this type of application is fully justified.
- Ilmenite. Iron is added to the titanium dioxide when the wire is coated. During the work the strong elastic seam is formed.
- The main.
Carbonate and fluoride compounds are used as coating materials.
They are resistant to changing ambient temperatures. But a significant disadvantage of this type of electrodes is that their use is limited only to parts that do not have a rusty edge. However, they can be used when working in any position and direction (top to bottom, bottom to top). They are used for welding structures that will later be operated at low temperature with variable or shock loads. A feature of the use of these electrodes is that they can only be used in welding works, which are conducted by a constant current of reverse polarity.
In addition, there are also rutile-base and rutile-cellulose coating. The electrodes, which are covered with the first of them, are used when laying pipelines of any purpose of medium or small diameter. The second coating is applied to the wire, which will be used when welding a thick coating.Back to table of contents
When performing DC welding, there are 2 ways to connect the electrode to the equipment:
Wiring diagram of the electrode when welding with a current of direct polarity.
- If the polarity is straight, the electrode is connected to the clip “-”, and the part to “+”.
- If the polarity is reversed, then the electrode is connected with “+”, and the part with “-”. This polarity is used when working with metals from a thin sheet, while burning is not possible.
The interaction of 3 welding characteristics (diameter of electrodes, thickness of the welding metal, current strength and type of current) determines the selection method. To do this, use the ratio that determines that for 30-40A current strength is taken 1 mm diameter of the wire. If the welding process is performed vertically, the current can be reduced by 15%.
This ratio looks like this:
Electrode selection table based on metal thickness and amperage.
- A diameter of 8-12 mm is applicable at a current of 450 A with a metal thickness of more than 8 mm. The length of the seams is 35-45 cm. The metal to be welded can be from any type of steel.
- A diameter of 6 mm is used with a current of 230-370 A, the thickness of the metal is 4-15 mm. The weld has a length of 35-45 cm.
- A diameter of 5 mm is used with a current of 150-280 A, metal parts are 4-15 mm thick. Formed seam length 35-45 cm
- A diameter of 4 mm is used if welding takes place at 100-220 A, the thickness of the metal is 2-10 mm. The type of choice of steel when performing welding is not important.
- A diameter of 3 mm is used when welding is performed at a current of 70-100 A, and the thickness of the metal is 2-5 mm.
- 2.5 mm is applicable if the current strength is 70-100 A with a thickness of 1-3 mm with a seam length of 25-35 cm.
- A diameter of 2 mm is used when the amperage is 50-70 A, the metal has a thickness of 1-2 mm. The seam should be no more than 25-30 cm.
Electrodes with a diameter of 3 mm or less are used in welding of parts for the production of which alloy steel is used.
In addition, the color of the coating can be used to determine which additives were involved in spraying it. Only tungsten is used for green coating. If the coating is blue, then lanthanum oxide is added to the tungsten. To obtain a white electrode coating, zirconium oxide is added to tungsten.