A reinforcement is a construction consisting ofrolled bars of various shapes and sizes. Its main task is to redistribute the compressive and tensile stresses within the building object. Accordingly, the rigidity of such a design is subject to increased requirements. The stiffness index, in turn, is determined by the quality welding fittings. Currently, several methods of welding are used. The features of some of them will be considered in the article.
The most common types of connections are:
The GOST defines the design, geometric parameters, types of joints produced by electric arc and contact welding armature.
The provisions of the standard apply to rods with a cross section of not more than 30, but not less than 4 mm, as well as a metal wire with a cross section of more than mm.
GOST defines three types:
Welding of fittings overlapping is done by 2-reliefs and seams(electric-arc manual method). The T-joint is made in the inventory form (using one electrode in the bath), under the flux (in this case, the filler wire is not used), mechanized, manually, contact (by continuous reflow of the product with resistance).
Buttock welding of reinforcement is carried out in various ways. The most common are:
This method is used, as a rule, for the connection:
Perfectly suited this method Welding fittings for foundation and other large reinforced concrete products, complex frameworks for the construction of different buildings. It ensures the preservation of the strength of the parameters and the rigidity of the structure along the entire length. Such a welding of reinforcement allows you to create a single power frame.
The connection can be made both horizontally and vertically. Bathroom fittings for column reinforcement and other vertical products can thus be carried out without moving them and bringing them to a horizontal position.
Another advantage is that standard joints are used to perform the connection, as in electric arc welding.
A key condition for obtaining high-quality joints bathroom welding fittings - a clear alignment of the bars. It is necessary to ensure that the axes of the rods do not move more than half their cross-section relative to each other.
To comply with this condition, conductors of various types are used. In them, the geometric parameters and arrangement of rods at welding armature remain unchanged.
Before direct welding to rodsattach (weld) the steel mold. It forms a bath with molten material. For this, an electric arc is used. The ends of the bars under high temperature melt. This leads to the creation of a single bath of seam material.
Before welding of fittings The ends and surfaces of the bars are cleaned. Scales, corrosion, dirt are removed from them. For this, a rigid brush with steel bristles is used.
After cleaning, the rods are placed coaxially. There should be a gap between the ends. Its size is less than 1.5 diameters of rods.
When welding column reinforcement as a moldelement is a sheet stamped form. It is attached to the bottom by welding without the use of additives. Fusion of the joint over the entire cross-sectional area is performed by performing oscillatory gradual movements of the electrode. With respect to the axes of the rods, such motions are perpendicular.
Slag excess is removed using a scoop. Then the end of the upper rod is attached to the end of the lower rod, after which the metal is guided into the mold.
The slag is discharged from the mold through a special hole, which is burned by the electrode. After the connection of the rods is completed, it is brewed.
In practice, three methods are used:
The most economical option is considered whenwhich are not used when connecting the rods. The fact of the matter is that it takes time and metal to make them. In the absence of lining, in addition, provides a compact connection.
Welding in the bath is performed at high currents. It can be 450 amperes if 5-6 mm electrodes are used.
If the connection of the products is carried out at low temperatures, the current is used about 10% higher than the standard one. Professionals recommend using the rods SSSI-13/55.
When using three-phase weldingleave a gap of 1.5-2 cm more than the diameter of the electrode. The mismatch index of the rods of the reinforcement bars should not be more than 5% of the area of the electrode cross-section. Experts recommend to give a "back deflection" bars, if they have a long length.
Quite often the ends of the rods when executedwelded joints are slagged. This is due to the rapid heat dissipation. As a result, the reliability of the connection is significantly reduced. To reduce the possibility of slagging, you can:
It is used to secure the joint from below. A staple is used from sheet steel with a low carbon content or made of rods.
The girth allows you to hold the liquid metal and prevents it from flowing. To increase the effectiveness of fixing along the edges of the bracket, limiters are installed, which do not allow spreading of slag along the rod.
Do not use overhead elements made of copper, brass, bronze alloys. As a rule, they are made of pure copper. Such staples serve for quite some time.
It is considered one of the most commonWelding methods. The contact point of the products is fused by heating to the temperature of deformation and squeezing. This is done by passing the current through the circuit, the links of which are also the rods themselves. The current appears in a closed circuit, and the greatest resistance is concentrated in the contact area of the bars. At the same time, heat is released, which ensures maximum heating of this area.
Reduce the welding time by increasing the currentup to 10, and in some cases up to 20 thousand amperes. In this case, the melting of the metal occurs almost instantaneously. Accordingly, the time of passage of the current along the circuit decreases substantially.
The contact connection of products can be carried out by a butt or dot method. The first one is used when the end parts are located butt-end. Spot welding of reinforcement It is used when the rods overlap. They connect in several points simultaneously.
To connect the rods, the contact method uses a professional apparatus. Welding of fittings must be carried out at a certain current strength and the level of compression of the contact area, within a given time.
All equipment is conditionally divided into mobileand stationary. The simplest device can be assembled independently. It should include 2 functional nodes. The first is the power supply, the second is the electrode holders of the remote type.
Its technology is based on the use ofheat at the ends of products. Heating occurs by passing through these areas of electric current. It is fed after the circuit is closed by connecting the ends. Provides heating with high resistance.
After completion of current transmission and disconnectionthe "sediment" of the heated section is produced. To quickly heat the metal in the region of the connection and prevent heat loss, a high current load mode is used.
Butt welding is used for joiningsmooth rods, whose diameter is not less than 14 mm. To connect a reinforcement made by a hot method and having a profile, this method is used if the diameter of the rods is not less than 32 mm.
Butt welding technology is divided into two types:
Priority is given to the second type.Before the beginning of work, the valves are cleaned of slag formations, paint debris, rust. For this, a chisel, a hammer and a metal brush are used. Cleanliness of the ends is essential for the quality of welding.
It is used mainly in the creation of reinforcing cages, reinforcing nets of bars with a small cross-section.
You can use spot welding and at home, for example, when repairing household appliances.
There are two ways to connect. In the first case, the metal in the bond region is brought to a molten state and before the cast core is formed. In the second - the metal just heats up.
If at the intersection pointthe contacting rods will pass a large current, in this region there will be a high heat transfer. This is due to the fact that the resistance of the bars of the reinforcement is higher than the copper conductors included in the secondary circuit of the welding apparatus.
The process should be carried out at high ratescurrent. Due to this, not only performance is increased, but also the quality of the connection. For this, powerful, expensive equipment is used. At home, you can use a compact device, made, including independently.
The key node of the device for the spotwelding protrudes transformer. It generates a large current. A transformer of the standard type OSM-1 can be used in the apparatus. However, it needs to be slightly upgraded to obtain a secondary winding of higher power.
The work is carried out in stages:
It involves fixing the rods partially overlapping each other. Using this method, the rods form one line with a mutual overlap of its length at the joining areas.
The lap joint is used to distribute the longitudinal compressive / tensile load on the surface of the rod. When doing work, you must follow certain rules:
Lap welding products for industrial use,it is recommended to perform using arc welding by hand. It is carried out by one or two seams from the flanks. To make the joint qualitative, the length of the seam should exceed the diameter of the rods by at least 10 times.
Manual arc welding is performed, as a rule, inhorizontal position of the rods. For operation, conventional equipment is used, which includes a transformer, a gas burner, or apparatus with a neutral gas.