Over the past few decades, the most common form of joining parts of many metal structures is manual welding. Of course, designers are constantly developing other types of welding that are more efficient, but their accessibility and the nature of the work cannot compete with the arc method.
For home use, manual arc welding technology is the most popular, as it is the easiest to learn method of joining metals. All tools and materials of this type of welding are affordable and cost-effective. On sale there is a huge variety of models of welding transformers, inverters, as well as a wide selection of electrodes for welding any metals.
Features of the use of welding
In almost any area of the national economy, welded joints are used by manual arc welding. Power supplies for this type of work are widely used in domestic conditions, since many of them work from a standard electrical network. The quality and reliability of the resulting weld are quite acceptable for the installation and repair of many metal structures in a home workshop, as well as for the creation of new products at industrial enterprises in various fields of activity.
According to GOST 5264-80, manual arc welding allows you to connect carbon steel metals in any spatial position, and the use of special electrodes makes it possible to weld parts of cast iron and various non-ferrous metals, including alloyed steel. In this connection joints are obtained with a high degree of resistance to fracture and tear resistance.
The possibility of surfacing surfaces of worn parts for their subsequent machining is another functional feature of this method of the welding process.
Welding principle
The technology of manual arc welding is based on the melting of the base metal and the electrode rod under the influence of an electric arc. During melting, the materials to be connected and the consumable electrodes are mixed to form a weld pool. After the solidification of this mixture, a solid metal structure is formed - a weld.
To protect the weld pool from the harmful effects of nitrogen, oxygen and other gases contained in the air, a special coating is applied to the welding electrodes. During welding, these components, being melted together with the base metal, create a protective film on the surface of the weld pool in the form of a gas cloud and slag.
For high-quality melting of metals, it is necessary to constantly maintain an electric arc between the connected elements, which arises from a special welding machine (inverter). The temperature inside the weld pool reaches 4000 ℃. Slag floats to the surface of the junction, protecting the working area from oxygen. In the future, after cooling the seam, the slag film is removed mechanically.
Arc Welding Benefits
The cost of manual arc welding with coated electrodes directly depends on the functionality of the welding machines. The more options that the used unit is capable of giving out, the higher its price. But not only the low cost of the unit determines all the advantages of manual arc welding, there are a number of advantages of this method of joining metals:
- the ability to weld parts in hard to reach places;
- welding joints in all spatial directions;
- quick replacement of the joined material;
- a diverse range of manufactured electrodes allows you to dock products from various types of metal;
- a manual arc welder does not have to have technical knowledge, because such a simple equipment can be mastered by anyone;
- small overall dimensions of the welding machine make it easy to transport it to the desired place of work;
- the ability to perform work throughout the working day;
- obtaining a weld of high strength.
Some disadvantages of an arc joint
Among the minuses of arc welding can be noted:
- harmful working conditions due to vapors and exposure to electromagnetic fields;
- relatively low efficiency compared to other types of welding;
- insufficient experience of the welder, which can lead to poor quality of the welded joint.
However, if you carefully follow the parameters of the correct connection and allowable weld dimensions, according to GOST 5264 for manual arc welding, you can qualitatively and reliably connect metal structures in a garage, cottage or country house.
Varieties of Arc Welding
From the very beginning of the development of manual arc welding and to the present, the connection process has been performed on two types of electric current:
For transformer welding, special transformers are used. The welding process is performed using melting electrodes. This type of welding is most popular when working at home, as the equipment is not very difficult to make on your own.
To make a DC connection, special rectifier devices are used. This type of welding greatly reduces the amount of spray molten metal, which improves the quality of the welded joint.
Any of these types is used not only for joining products, but also for depositing a certain layer of metal on the surface of a worn part, which is of particular use for many repairs.
Down welding technology
First of all, it is necessary to conduct the correct preparation of the welded surfaces, for which it is necessary to cut the edges at an angle of 45 °. In the case of welding parts thicker than 6 mm, it will be necessary to set a gap of 2-3 mm in order to produce a good penetration of the joint.
The ignition of the arc is carried out by lightly tapping the electrode on the mass. It is advisable to perform this operation on a separate metal plate, and then bring the heated electrode to the place of welding. After completing the preparatory operations, grab the surfaces to be welded in several places.
The electrode during manual arc welding is held at an angle of 45 ° with respect to the plane of the surface being welded. In this case, the root seam is applied first. It is done by leading from one side to the other of the electrode in smooth and even movements.
Further, according to GOST, welded joints by manual arc welding are performed by transverse-oscillatory movements to fill the entire weld zone and expand it. When conducting a spiral-like translational movement, it is necessary to control the distance between the electrode and the metal plane (5 mm). It is better to provide a slight inclination of the welded parts so that the hot slag flows to the side. If this is not possible, this operation is performed by the welder himself with the tip of the electrode.
The end of the weld must be overlapped to avoid a funnel.
Vertical seam technology
Manual arc welding can connect products in an upright position. For this, it is necessary to carry out the work with discontinuous arc technology. Liquid metal has a relatively large weight, so the continuous heating of the junction will cause the molten metal to flow down. In this case, the seam is made in the form of shelves, i.e., is superimposed on top of each other in layers. Of course, with such a connection, the execution time of the work increases, but the welding quality does not suffer.
Using the same technology, welding of ceiling joints is also performed. The main thing in such conditions is to choose the right welding mode.
Welding speed
The speed of the electrode during arc welding is selected in accordance with the thickness of the parts to be welded, as well as depending on the dimensions of the weld. The basic principle of weld quality is the complete filling of the weld pool with molten metal. If there were sagging or undercuts, then the welding speed was chosen incorrect.
A quick movement of the rod leads to lack of penetration of the joint, since the temperature does not have time to reach the melting value of the base metal and the seam is thin. After cooling, cracks and deformation of the seam may occur.
When the electrode moves slowly, a mass of molten metal is formed in front of the arc, which also prevents optimal weld penetration.
Selection of current parameters
An increase in welding current has virtually no effect on the width of the seam. The main influence is on the depth of the melt - the larger the current, the deeper the value of the effect of temperature and, conversely, when the current decreases, the depth of the melt decreases.
Particular importance should be given to the nature of the current. DC operation allows you to get a narrow weld.
Also, the depth of temperature depends on the diameter of the electrode. At the same current, a smaller cross-section of the rod reduces the width of the seam and increases the penetration of the metal. But the change in arc voltage affects only the width of the seam, while almost without changing the value of the metal penetration. It is a change in voltage that regulates the width of metal deposition in automatic welding devices.
Welding Safety
Despite the fact that welding works, at first glance, is a simple task, however, actions with high temperature and electric current require focus and attention from the welder of manual arc welding.
To protect human health, the following safety requirements must be strictly observed during welding.
- The main requirement for safe operation is the presence of a protective welding mask with tinted glass. The use of these tools will save the welder from damage by metal scale and will effectively protect the eyes from the harmful effects of electrode sparking.
- In order not to be affected by electric current, all work must be carried out with rubber gloves. At the same time, it is necessary to ensure that they are without holes and are not wet.
- The welding cable must not have cracks in the insulation. Routing the cable through snow melt or puddles can result in electric shock.
- Since the weld pool contains molten metal, all measures must be taken to avoid contact with liquid material.
The welding technology is constantly being improved, however, despite this, manual arc welding has been and remains the most popular type of metal joining - not only in industrial enterprises, but also in everyday life. If you master this type of welding correctly, then you can quickly and efficiently perform almost all work with metal products.