- Welding machine models: how to choose. Tips & Tricks
- Selection of the diameter of the welding electrode, welding current, arc length
- Types of electrodes for welding with various types of metals
- DC different polarity welding
- Welding metal seams in the lower position
- Welding vertical seams
- Welding seams in several passes
- Weld seam treatment
- Safety when working with a welding machine
The article discusses the organization of welding, the choice of electrodes, the metal welding process, the choice of the most optimal welding machine for household needs. Also, advice is given to those who first encountered welding issues.
Welding work is a demanded service, and at the same time remains practically the most expensive on the installation work market. Depending on the complexity, only one seam can cost up to $ 5, while the need to perform these works arises quite often.
Welding machine models: how to choose. Tips & Tricks
In recent years, many decent and inexpensive welding machines have appeared, with which you can independently perform almost all household work related to welding. It is not difficult to buy it, but before buying it is necessary to determine exactly the type of welding machine and its capabilities..
At home, it is extremely rare that there is a need for welding non-ferrous metals or high-alloy, refractory steels, most often it is necessary to make various structures from low-alloy, ordinary steel of various thicknesses. Therefore, when buying equipment, you can give preference to transformer or inverter welding machines that produce the so-called MMA or RDS welding using stick electrodes with a special coating..
A feature of these electrodes is the so-called “coating”, which burns out during welding and at the melting point excludes contact of liquid metal with oxygen. Modern inverter and transformer welding machines are inexpensive and small in size. The welding current of these devices can reach 200-250 A, which is sufficient for working with electrodes up to 5 mm in diameter.
Welding models based on transformers are much heavier than inverter models, have a short step of output power regulation, low efficiency, but are practically insensitive to voltage drops in the network, can easily operate from a portable generator.
Inverter models are mobile, have smooth power control, due to the use of automatic control of the inverter, they allow to achieve a smoother seam overlay, simplify the process of igniting the arc and are equipped with better protection of internal elements than transformer models.
For those who want to make money on car body repair, these models of welding machines may not provide the necessary comfort and efficiency, it is better to opt for semi-automatic models of welding equipment. This technique performs the so-called MIG-MAG welding.
This technology is based on the use of an inert gas supply to the welding area, and a wire fed in an automatic mode is used for the welding process. Such an apparatus is ideal for welding thin automotive metal, does not create burn-throughs and welds, and during welding in an oxygen-free environment, practically no slag is formed, a thin wire used as an electrode does not have an applied flux coating and during combustion heats only a small area of the joint metal.
Unlike previous models, a semiautomatic device requires a cylinder filled with compressed carbon dioxide or inert gas, which negatively affects the mobility of the equipment. At the same time, this welding machine can work without a gas cylinder, but for this you need to use a special flux-cored wire containing the necessary flux in its composition, during such welding, slag deposits are formed on the surface of the welded metal, and the cost of work will be much higher than on MMA welding machines.
Comparison of various household welding machines:
|Welding machine type||Metal processing with a thickness of 0.5 mm||Welding machine cost||Consumables price||Maximum output current when operating from a 220 V network||Service||Welding machine weight||Welding type|
|Semiautomatic device||+||Max.||Max.||80-150||Max.||Max.||MIG / MAG|
The most popular welding machines in recent years have become machines manufactured using inverter technology. Despite its complexity (it contains several transformers, two rectifiers and an inverter), with a decrease in the cost of semiconductor elements, the cost of this equipment has reached an acceptable level, which, combined with simplicity in operation, has led to the dominance of this technology in everyday life. For work with both inverter and transformer welding machines, the general rules for the selection of working electrodes and welding technique apply. Let’s take a look at these rules.
Selection of the diameter of the welding electrode, welding current, arc length
The exact choice of the diameter of the electrode is the key to high-quality work, since the width and depth of the seam, as well as the power required for work, directly depend on this parameter. For most ordinary steels, an approximate table can be drawn up indicating the diameter of the electrodes and the parameters depending on this value:
|Electrode diameter, mm||1||1.5-2||3||3-4||4||4-5||6-8|
|Optimum thickness of the welded metal, mm||0.5||1-2||3||4-5||6-8||9-12||13-16|
|Current required for welding, A||10–20||30-50||65-100||100-160||120-200||150-200||200-350|
|Burning arc length, mm||0.6||2.4||3.5||4||4.5||five||6.5|
Failure to comply with the nominal parameters will lead to overheating of the metal at the welding site, burnouts, undercuts, lack of penetration, lack of fusion, beads and other types of defects in the welding joint.
Types of electrodes for welding with various types of metals
The metal has a complex structure and composition, therefore, for its high-quality connection by means of welding, it may be necessary to use electrodes that are different not only in diameter, but also in structure.
The main component that affects the properties of the electrode, in addition to the composition of the metal itself, is its “coating”. This mixture at the point of arc burning is also subject to combustion, during which oxygen is removed from the space surrounding the arc, providing conditions for stable metal fusion.
Currently, four main types of coatings are used for MMA welding:
- Acidic – A. The coating contains oxide of iron, silicon, manganese, the weld from an electrode with such a coating can crack in places where the metal is poorly prepared for welding (the presence of scale, rust on the surface to be welded).
- The main one is B. The coating consists of fluorine and carbonate compounds, the resulting seam is very plastic and shock-resistant, but the welding process can disrupt the presence of moisture or oil on the welded surface, inclusions of rust or scale.
- Rutile – R. The coating contains a concentrate of titanium dioxide – rutile, this coating provides powerful arc burning, the presence of moisture, rust has practically no effect on the quality of the finished welded joint. Slag formed during the welding process is easily removed from the metal surface.
- Cellulose – C. The coating can contain up to 50% cellulose or other organic matter, used for specific welding work.
There are also a large number of electrodes, the coating of which contains these components in various combinations, but the most universal electrodes are rutile and basic, they are suitable for most beginners.
DC different polarity welding
When welding with direct current, it is necessary to take into account the fact that the amount of heat released during welding depends on the polarity of the current connection to the electrode, the positive pole always heats up more than the negative.
This property is used to optimize the welding process, to connect a thin metal, “minus” is supplied to the workpiece, and “plus” is applied to the electrode, which corresponds to the conditional reverse polarity of the connection. Reverse polarity is suitable for joining high alloyed or hardened steels to avoid overheating. If necessary, during the welding process, heat up the thick metal as much as possible, the “plus” is connected to it, and the “minus” to the electrode, which corresponds to the direct polarity of the connection.
Welding metal seams in the lower position
It is easiest to learn how to weld metals when they are below the welding electrode, parallel to the ground. In order to start connecting metal blanks, you must perform the following operations:
- Select the type and diameter of the electrode.
- Set the welding machine to the required current.
- Place the electrode in the holder.
- Match the polarity of welding and fix the power cables accordingly.
- Kindle the arc.
- Smoothly guide the electrode parallel to the joint, controlling the state of the arc.
- Remove scale from the weld and reapply the weld if necessary.
The arc can be ignited in two ways. The first method resembles the process of setting fire to a match – the electrode is placed at an angle to the workpiece and quickly carried over it, after the appearance of sparks it slowly rises above the metal, while the arc is controlled. The second method – a touch-impact is performed with the electrode on the metal, while the electrode is brought to the welding surface quickly and moved away slowly.
Welding vertical seams
Since, under the action of gravity, liquid metal can flow out of the weld pool, in order to prevent this from happening, the seam is applied from its lower point with a smooth rise up along an indirect path of movement, for example, a crescent.
Welding seams in several passes
A high-quality connection of metal with a thickness of more than eight millimeters is performed in two passes, first on one side of the workpiece, then after turning it over – on the other. In this case, it is important to control the absence of lack of fusion, for which it is necessary to select the working current and the diameter of the electrode as accurately as possible.
To join thick metal blanks, the welded edges of the blank are cleaned at an angle of up to 30 degrees, a copper or refractory steel sheet is placed under the welded metal blanks, after which a root seam is applied with a 4 mm electrode. All subsequent passes can be made with thicker electrodes for faster filling.
Weld seam treatment
In the process of welding, in addition to the metal welding seam required in the future, the so-called slag is formed, which includes burnt coating, metal spatter from the electrode and the surface of the parts to be welded. All these elements, after applying the weld seam, are removed with a hammer and a metal brush.
If there is a need to apply several layers of welding on a metal surface, then cleaning is performed after each separate pass with an electrode.
After the completion of welding, the part of the weld seam protruding beyond the workpiece is removed using grinding wheels, files and other processing tools.
Safety when working with a welding machine
When performing welding work, special attention must be paid to safety.
- The first thing that needs to be monitored is electrical safety. The voltage at the output of the welding machine is much lower than the mains voltage, but under certain conditions it is sufficient to shock a person. To protect against electric shock, dielectric gloves are used, the connection of the second working wire from the welding machine to the workpiece is controlled.
- The second safety issue during welding, which must be constantly monitored, relates to fire-fighting measures. During the welding process, a large amount of hot spatter is released, the metal itself heats up to the combustion temperature of various flammable substances, therefore, during the welding process, it is necessary to control the presence of a fire extinguisher or other means necessary to extinguish a potential fire, to carry out preliminary preparation of the workplace.
- The third and most important safety issue relates to the need to maintain the health of the welder. During the combustion of the mixture and the steel melting, a large amount of harmful substances is released into the air, therefore it is necessary to control the presence of ventilation at the place of welding work and its sufficiency. Sprays of hot metal easily melt clothes made on the basis of synthetic fabrics; to work with a welding machine, it is better to use special overalls that are resistant to heat.
One of the main issues when welding with electric current is protecting the eyes from the bright glow of the arc. For these purposes, special shields with inserted darkening glasses are used, but this protection, although it helps to minimize the harmful effect on the retina, does not completely save.
The appearance of “chameleon” masks, which change their darkening properties depending on the brightness of the light source, allows you to minimize catching “bunnies”.