Gas welding and cutting of metals. Gas welding technology. Gas Welding Equipment
Gas welding is a type of welding when parts need to be heated to a molten state by means of a high-temperature flame. This method is widely used in the creation of structures based on thin carbon steel, in the repair of products made of cast iron, as well as the need for welding defects in various products obtained by casting from ferrous or ferrous metals.
What gases are used?
Gas welding uses combustible gases — natural, acetylene, gasoline vapors, and hydrogen. These gases are distinguished by good combustion in air, without developing a high temperature, and an oxygen stream is sufficient for incineration. Gas welding is most often based on acetylene, which is created on the basis of water and calcium carbide.It burns at a temperature of 3200-3400 degrees.
What are the features?
The advantages of gas welding include the following:
- Simple technology.
- No need for a source of welding current.
- The simplicity of the equipment, on the basis of which gas welding is performed.
On the other hand, this process does not have high performance. Welding is performed only by hand, and the mechanical and performance properties of finished products are not always of high quality.
When welding, oxygen comes from a special cylinder - it is painted in blue or blue. In order to ensure normal operation, oxygen must be supplied to the burner evenly and with a slight pressure. For these purposes there is a reducer on the cylinders - it regulates the gas supply. In this case, gas-welding hoses — acetylene and oxygen — are supplied to the torch. Oxygen is supplied to the central channel, where the jet discharges more, sucks acetylene, which enters the burner under slight pressure. Gases are mixed in the chamber, then go out of the tip.
When performing gas welding, it is important to obtain a high-quality connection, so much attention is paid to the careful preparation of the welded edges, the choice of the method of joining the metal, setting the torch to the desired position and determining the required parameters of the burner power. Gas welding technology suggests that the edges should be thoroughly cleaned of various contaminants. The bevel is performed using a manual or pneumatic chisel, and sometimes special machines are involved. Dross and slag can be removed with a metal brush. Tacking edges helps to prevent their changing position during welding.
Gas welding can be carried out in several ways. The first is left-side welding, which is most common. It is used when working with thin and fusible metals. The burner moves from right to left, and the filler wire is led in front of the flame, aimed at the non-welded portion of the seam. In right-hand welding, the burner goes from left to right, and the filler wire moves behind the burner. With this method, the heat of the flame is dissipated to a lesser extent, and therefore the angle of opening of the seam is not 90 degrees, but less - 60-70.
Right welding is advisable to use for joining a metal whose thickness is from 3 mm and above, as well as metals with a high level of thermal conductivity. It is recommended to use filler wire whose diameter is equal to half the thickness of the metal being welded.
The technology of gas welding involves the process, which is conducted through the roller. In this case, the sheets are set vertically to the gap - it is equal in size to half the thickness of the sheet. Using a torch, the edges are melted to form a round hole. Then it is melted on all sides until the seam is welded. This method is good because the welded sheets have a tight seam without pores and slag inclusions.
Welding trays is good for welding joints and corners of joining metals, which have a maximum thickness of 3 mm. As soon as a bath is formed on the seam, the end of the filler wire is introduced into it, which melts slightly, then the end of the wire is moved to another part of the seam. The peculiarity of this approach is in the weld of excellent quality, especially if thin sheets and pipes made of steel (low-carbon and low-alloyed) were welded.
Gas welding and cutting can be carried out on the basis of multilayer welding. This method has several features:
- the heating zone is small;
- the underlying layers during the surfacing of the next are simply annealed;
- each seam can be forged before putting the next seam on it.
This has the effect of improving the quality of the seam. On the other hand, this method has a small productivity, requires a high gas flow rate compared to single-layer welding, so it is used when necessary to create responsible and high-quality products.
Features of welding various seams
For working with horizontal seams, the right method is used, which makes it possible to easily form a seam, and the metal of the bath itself does not flow down. Welding of vertical and inclined seams is carried out by the left method, and if the thickness of the metal is higher than 5 mm, a double roller is used. Welding ceiling joints involves heating the edges until they are melted, then filler wire is introduced into the bath - its end is quickly melted. The process itself is conducted in the right way.
Gas welding equipment for gas welding is a wide range of devices that allow a number of works. This type of welding is considered simple, and the equipment itself is quite concise and easy to operate.Depending on the type of fuel gas-welding devices are propane-oxygen or acetylene-oxygen, gasoline or kerosene-oxygen. Most often, welding is performed on the basis of propane-oxygen and acetylene-oxygen welding, since the flame of these gases has the highest temperature.
Gas welding equipment for gas welding is also a generator, which is complemented by different types of gas. Also during the work you will need an oxygen cylinder and gearboxes. The most common are acetylene generators for gas welding, which make it possible to directly obtain acetylene by mixing calcium carbide and water. This type of generator is presented in five types, which allows you to choose the best option for a particular material.
An important role when working with welding is played by safety valves, their task is to ensure safety during welding. With their help, flame backfire that occurs during welding is prevented. In addition, due to non-return valves, the backflow of gas into rubber hoses is prevented during gas-flame treatment of metals and work with compressed gases.
Gas welding equipment includes cylinders and valves for them.The cylinder is a cylindrical vessel that has a threaded hole in the neck where the stop valve is screwed into. It is created from alloyed or carbon steel, and each such product has its own color depending on the gas contained in it. Valves for cylinders are made of brass, because the steel is highly resistant to corrosion.
Gearboxes: types and features
A gas pressure regulator is a device that constantly lowers or keeps gas pressure at a certain level. Gas welding and cutting of metals are carried out on the basis of different types of gearboxes:
- Oxygen is used in gas welding and metal welding. This gear is performed with a blue marking. It can be used in an aggressive environment, because it is made of corrosion-resistant metals.
- Acetylene reducers are widely used in gas welding. They are marked in white; fastening to the cylinder is carried out with a hose strap. This type of gearbox has two pressure gauges, one of which keeps the gas pressure in the cylinder under control, the second one - the gas pressure in the working chamber.
- Carbon dioxide gears are widely used in industry - food, chemical. They have one or two gauges and can only be connected to a vertical gauge.
In argon-arc welding, argon gearboxes that can work with non-combustible gases are widely used.
Features of gas burners
Gas welding of steel is a process that requires the use of a variety of devices. Gas burners are an integral part of equipment that is used in various industries. The design of the product is about the same: each burner consists of a body. Several elements are fastened to it at once: a tip, a valve regulating the supply of fuel, and a lever that regulates the height of the flame. The connection with the cylinder is carried out by the reducer, while the burner itself can often be supplemented by piezo igniting, flame protection and other components.
The propane-based gas torch is safe to operate, ensuring the high temperature of the flame: it is enough to perform a variety of jobs. Many types of welding are based on acetylene torches, which work on a mixture of acetylene and oxygen.
Types of gas cutters
Gas cutters are of different types: acetylene, propane and working on gas substitutes or liquid fuel. The product design includes a handle, nipples to which the gas hoses, the body, the injector, the mixing chamber, the tube, the head of the gas cutter and the valve tube are attached. Gas welding of metals and its quality depend on how well the cutter is chosen.
The essence of his work is as follows: from the cylinder oxygen enters the gearbox, the sleeve, and then enters the body - here the cutter splits into two channels. Part of the oxygen passes through the valve and is sent to the injector. From here, the gas comes out at a high speed, and during this process combustible gas is sucked in. When combined with oxygen, it forms a combustible mixture, which is directed into the space between the mouthpieces and burns. As a result, a warming flame appears. Oxygen, which was directed through the second channel, goes into the tube, due to which a cutting jet is formed. It is he who processes the area of metal.
Features of pipe welding
Welding of gas pipes is carried out in several stages.First, the metal is prepared, that is, the marking is carried out, pipes are cut and assembled. Due to the circular cross-section of the pipe, cutting is performed with a thermal cutter. Most of the work on welding is the assembly of parts for it, when you need to take into account many details - from a series of products to their diameter and other factors. The assembly is performed by welding tacks that prevent the possible displacement of pipe sections, which affects the appearance of cracks during cooling.
The arc ignites. This is done in different ways. Then begins the melting of metals - the main and electrode. For high-quality seam it is important to pay attention to the angle of the electrode.
Gas cutting technology
Oxy-fuel cutting is carried out using metals and their alloys that burn in a stream of technically pure oxygen. This type of cutting is performed in two ways - dividing or superficially. The first method allows you to cut the workpiece, cut the metal, cut the edges of the weld under welding. With the help of surface cutting, the surface metal is removed, grooves are cut off, and surface defects are removed.This procedure is performed on the basis of special cutters.
Gas welding is a process that requires careful attention. Hazardous situations can occur in several cases:
- Welding should not be carried out near flammable and flammable materials (gasoline, kerosene, tow, chips).
- If welding is performed in a confined space, workers should periodically go to fresh air.
- Works should be carried out in well ventilated areas.
- If flame treatment of metal is carried out, the room must be ventilated in order to remove harmful gases.
- Cutting and welding are carried out at a distance of up to 10 m from the bypass ramps, acetylene generators.
- Sections of loading boxes should not be overfilled with carbide.
- The generator housing must always be filled with the right amount of water.
- It is forbidden to work with an oxygen cylinder whose pressure is below normal.
- The flame of the burner is directed in the direction opposite to the gas supply source.
Welding work should be carried out with maximum observance of safety rules and using only high-quality equipment.This will make the process safe, and the connection of metals - reliable.