How to cook pipes: types of welding and welded joints
Connection of separate elements of pipelines is carried out by various methods, but, the most popular of all - welding. This method is used in everyday life, and at different industrial plants when connecting parts of pipelines of different materials (metal, plastic). Pipe welding technology allows you to join parts on the pipeline in any position, which is very convenient. exept this, welded joints are characterized by increased strength and tightness, unlike threaded.
Welding is the most reliable and durable connection, used in the installation of pipelines for various purposes
Features of pipeline connection by welding
Connection of separate elements of pipelines or household branches is carried out according to uniform standards. The master uses special equipment, regulated by GOST, which affects the pipe in one way or another (depending on the case).
Useful Information! The whole process is to connect the individual sections of the pipeline with a seam. Welded elements must be inspected after completion (so-called quality control).
According to the type of welding effort, pipes are divided into four types:
- thermal;
- thermomechanical;
- mechanical;
- cold.
In the thermal method, the edges of the pipe are heated. In thermomechanical - the connection of pipes is carried out by heating a special wire. The mechanical method is used, usually, for industrial purposes and can be carried out due to the force of friction or directed explosion. And there is cold welding, which is performed using special chemical compounds. The tool is applied to the edge of the pipes, designed for welding, and press them, as a result after some time the strong enough seam is formed.
Most often, metal and polymer pipes are connected by thermal welding
Welding of pipes of different diameters is carried out with the use of special conductors. This can affect the reliability of the connection, however, if all the work is done correctly, then the joint will be strong and tight and will last a long time.
Types of welding and their differences
Quarreling is a physico-chemical way of connecting sections of pipeline, which forms a tight connection of two parts of the structure. This is either due to the alloy or due to plastic deformation under pressure. The technology of forming the weld may be different depending on the type of welding:
- hot;
- cold.
According to the method of execution, this process can be:
- manual;
- automatic.
The manual method implies, that all stages of welding work are performed by man. The automatic method is performed using special machines. In automatic welding, all stages are mechanized and do not require human intervention, but, at the stage of preparation of the master make the necessary settings, setting the welding program. The price for such machines is quite high and, therefore, they are used very rarely, usually, at large enterprises, who perform large amounts of work.
To date, there are close 50 types of welding and a huge variety of welding equipment. The most common species today are:
- electric welding;
- cold;
- gas;
- diffuse.
Electric welding requires the use of special equipment, mains operated
electric welding
To date, the use of electric welding is the most popular method. Although a few years ago the championship was given to gas burners. Such popularity of electric welding is caused ??simplicity and low cost of works. It is often called arc or contact. By the type of effort it is attributed to the arc group of thermomechanical work.
To perform such work, requires an inverter or transformer. This equipment performs the following function - supplies charge to the electrode. The edges of the welded element are treated with an electrode. At collision of materials the arc electric charge of huge power is formed. This reaction is accompanied by the release of high temperatures, which makes it possible to process the pipe.
Coating layer (coating) the electrode allows to maintain special conditions during work, which prevent the flow of oxygen to the melting point.
Consider, on what factors the width of a seam depends:
- from the thickness of the electrode;
- from the material of the products, welded;
- welding devices may include different welding modes, which also affects the characteristics of the seam;
- from the speed of the arc and the voltage in the network.
The above parameters determine not only the characteristics of the weld, but also on the amount of slag, formed during welding.
Importantly! It's worth remembering, that the formed slag is subject to removal.
Electric welding of pipes is considered cheaper, than gas, however, it takes more time to create a seam in this way. Other advantages of electric welding include:
- functionality;
- versatility.
Electric welding cannot be performed without electrodes, the size of which is chosen depending on the type of processed pipes
choice of electrodes
Welds can be different, usually, their quality depends on it, which electrode was used for welding pipes. The choice of electrode depends on several important factors:
- material, of which it is made ??pipe;
- pipe cross-section indicator;
- wall thickness.
Useful Information! Thick-walled electrodes use thick electrodes 2-3 mm. Welding of thick-walled pipes is carried out by electrodes with a diameter 4-5 mm.
All electrodes differ depending on the thickness of the coating. The percentage of the mass of the coating to the total mass of the electrode can vary from 3 to 20%. Coating layer, applied to the electrode rod, creates the necessary environment, in which the process takes place without access to oxygen. There is a certain pattern - the amount of slag, affecting the quality of the seam, depends on the thickness of the coating layer.
When choosing an electrode, you must take into account all the above parameters. To obtain a quality seam, you should pay attention to many factors, affecting the compatibility of different types of electrodes with pipes.
Cold welding
Cold welding for pipes is regulated by the relevant documentation and is a method of obtaining integral, sealed connections. This method eliminates the heating of parts, welded, and the joining itself is performed due to deformation. Cold welding is performed by pressure, what is done in detail. As a result of such welding, the oxide layer is destroyed and the connection is made at the atomic level (diffusion of atoms).
Cold welding is carried out on special equipment in industrial conditions
Such welding is divided into three types depending on the technology:
- point;
- suture;
- Butt.
Cold spot welding is performed using a punch. The punch is a device, which performs pressing of materials. The second type - seam welding, performed in two ways: welding along the entire length and execution of welding points, subsequently forming a continuous seam. Butt variant is performed due to strong compression, fixed in the clamps of the elements.
Consider the main areas of use of the cold method:
- joining parts, made of one metal;
- production of rolled metal, which has several layers, represented by various metals;
- when reinforcing aluminum wires. Reinforcement is made of copper.
The method of cold welding is quite popular today. Its popularity is due to ??the following benefits:
- at cold welding deformation of metal details is excluded. It has to do with that, that the workpiece is not heated;
- using this method allows you to get a very neat seam, characterized by high strength and tightness. exept this, it does not require additional processing;
pay attention! There are cases, when cold welding is the only way out. Example, aluminum and copper joints can only be made by cold welding.
- no waste remains after this process (electrode residues, metal splashes, etc.. d.);
- the work is carried out without the use of electricity;
- such a method, among other things, is environmentally friendly, because the work is performed without the release of toxic substances, as well as without radiation harmful to human eyes.
- the possibility of connecting large areas when using blast welding.
Gas welding allows you to get the most aesthetic seam at the junction of parts
Gas welding
The connection of different types of pipes using a gas burner is very old, but also a reliable way to install communications. Special gas burners are used for these purposes, which are able to heat the pipe to high temperatures.
Due to the heating of the edge with the connecting wire quickly reaches the melting point. As a result, the metal floats on top of each other and a strong integral connection is obtained, which is resistant to mechanical influences.
Consider the main advantages of using gas welding for the installation of pipelines of different directions:
- high efficiency of the method;
- using a gas burner allows you to get neat, quality seam;
- the process is not particularly difficult;
The disadvantages of this method include:
- work with a gas burner should be carried out only by a specialist, who has certain skills in this area;
- gas welding is a rather expensive method, as expensive resources are used.
diffuse welding
All previous pipe welding methods are used to connect metal pipes, but today such products compete in the construction market with plastic parts. A special method is used to connect the individual elements of plastic communications, which has gained great popularity - diffuse welding.
Diffuse welding is a method of connecting polymer pipes - polypropylene, PE and others
The main advantages of such welding include:
- obtaining an aesthetic seam;
- minimum required tools;
- high speed of installation;
- attractive price.
Special devices are used to obtain a one-piece connection between two plastic pipes, which heat the plastic. Such devices are completed with various nozzles. All nozzles have their own diameter, corresponding to the cross-sectional dimensions of a particular pipe.
Let's consider the main stages of connecting two plastic pipes with the help of such a device:
- Focusing on the diameter of the pipes, connecting, the necessary nozzle is selected.
- Pipes are laid inside the device.
- The pipe material is heated and their ends are compressed inside the device.
- After, as the connecting seam is formed, the machine turns off.
The connection can be used in a few hours. This method is quite simple and fast, and the line of welding of a pipe differs in durability and accuracy.
Types of welded joints
For different types of pipes (by material and purpose), is the norm for the use of various welding methods. However, in almost all cases, electrical alternating current is required. This is due to the financial benefit, as the use of other options for electricity entails more costs. Welded joints are two or more parts, which were joined together by welds.
The butt weld does not deform the workpiece and is the most reliable
Let's look at the main types of welded joints:
- butt;
- angular;
- overflow.
Importantly! When welding pipes with a wall thickness of more than 3 mm requires processing of their edges. The opening angle of the joint should be no more 60-70 °. When processing the pipe for welding it is necessary to remove the chamfers from the ends. This can be done mechanically or by any other suitable method.
Butt. This type of weld is very common because of this, which are practically not subject to deformation in the course of cooking. exept this, such joints have the lowest internal stress. They also have high strength characteristics as static, and under dynamic loads. Seams at such welding can be:
- single (for pipes with cross-sectional indicators up to 500 mm);
- double (for pipes with higher cross-sections 600 mm).
Angular. Angle joints are a subtype of butt welding and, usually, are used to join the pipe with any additional parts at an angle. Welding the pipe at an angle is performed in two ways:
- with beveled edges;
- without bevel.
The strength characteristics of the corner joints are not so good, as in butt, however, still quite good.
Outbreak. This connection is not used for welding metal pipes. Usually, they are joined by individual parts or plastic pipes. It has to do with that, that such a connection is the most unreliable.
Welding of thick-walled pipes is performed by two welders at the same time
Thick-walled pipe welding technology
Welding of thick-walled pipes is carried out in the case, if the wall thickness exceeds 20 mm. Such welding is carried out in layers of increased thickness. This allows you to increase the strength of the connection 10-15%. This type of work is carried out, usually, two welders at the same time. The first welder makes a normal seam, and the other is a thick layer.
How to weld pipes with thick walls:
- The quarrel begins in the ceiling position with a gradual increase in the thickness of the seam (the line of welding of thick-walled pipes should be as smooth as possible).
- Next you need to go to the semi-vertical position.
- With the help of the electrode is a horizontal platform.
- Then welding is performed in the lower position. This allows the use of electrodes with a thickness of up to 5 mm.
Welding of pipes on a gleam
Many people are wondering: how to weld pipes under the lumen? And even some experts do not fully understand, how to cook pipes by this method. This is especially true for young people, just graduated from technical schools and vocational schools.
First of all at welding of a pipe under a gleam it is necessary to seize pipes. This will eliminate the possibility of root deformation. How many attachment points need to be performed is determined based on the size of the pipes. Capture details this way, so that the gap at the joint is not immediately.
After performing the joint grip, it must be cleaned. exept this, it is very important to remember, that if you in the process of welding under the lumen found defects in the root (example, cracks), you need to delete them. After, how the cleaning of surfaces is performed, the seam is filled. Usually, filling the seam is considered the easiest step, however, in some cases to fill it goes to 30% root.
It is recommended to leave a small indentation when filling the seam. There will be enough depth in 1,5 mm. This is necessary to perform cladding. If to do so - facing material will lie down very accurately in this small furrow and the aesthetic seam will turn out.. It is important to remember two rules: when filling the seam it is necessary to maintain the working angle, and cook on a short arc.
