All about welding

 

 

All about welding

It is necessary to know everything about portable welding machine, at least in general terms, for all managers, customers and those who evaluate the result. There are various types of welding, including orbital, electroslag and diffusion techniques, but their characteristics are not familiar enough to non-specialists. To know only autogen welding, in short, it is completely frivolous in the XXI century.

 What is it?

The history of the development of welding is no less fascinating than another exciting novel. It can even be considered that welding is almost the same age as civilization. Already at the first forging processes, the practices of metal welding by pressure were introduced. But, of course, over the past centuries and millennia, it has significantly developed and improved. Forge welding and soldering were an integral part of everyday life until the end of the XIX century, and in some places were actively used until the middle of the XX century.

 But scientific and technological development has laid the foundations for many types of welding, which in the past could only be dreamed of. First of all, the practice of electric welding appeared. Later, various gas and modified electric, plasma and ultrasonic methods were introduced. The welders were served by an explosion and powerful pressure, ultrasound and water pressure, laser devices and robotic systems. However, the essence of the process remains the same as it was 5000 years ago – there are 2 or more fragments of metal or alloy that need to be qualitatively connected.

 Among the methods and types of welding, there is such a well-known (even for non-professionals) option as welding with an autogen. Its essence is very simple: due to the combustion of gas, a very strongly heated flame jet appears. The temperature in it exceeds 3000 degrees. None of the metals and alloys used in everyday life or in transport can withstand such strong heating. Therefore, we can say that autogenous welding is universal.

 The most complex component of the "autogen" is a special cutter. Industrial equipment of this type can operate with a variety of gases. But in most cases, they still use proven acetylene and propane-butane. They have actually proved their suitability for welding almost any structures and products.

 It should be emphasized that, despite the availability and comparative simplicity, it is possible to work with autogen only according to a strictly verified scheme — deviation from it leads to a deterioration in quality.

 Speaking about the pros and cons of welding with acetylene, it is necessary to point out:

 autonomy from power grids and electrical equipment (but sometimes you can't do without using it if you are solving a responsible or" very subtle " task);

changing the degree of heating of the welding bath only by adjusting the location of the burner;

ease of burn prevention — due to the same maneuver;

mobility of equipment;

explosion, fire hazard and gas toxicity;

relatively low process performance;

a high heating area (a lot of energy is wasted, and unnecessary heating of the metal has a negative effect on it);

mandatory high qualification of the performer;

low suitability for large-scale mass production.

 An important place in the classification of welding techniques is occupied by orbital welding. No, they are not engaged in it at orbital stations. We are talking about the fact that an electric arc describes an orbit around the pipe being welded. This option is considered technically difficult – the most experienced welders respect those who own such technology. The advantage is that you can get a very reliable seam, regardless of the cross-section and size of the connected parts.

 All the equipment for orbital welding is fully automated. It consists of:

 the electrodes are particularly refractory made of tungsten;

"head" (with a fixing system on the pipe);

protective gas supply device;

electronic control system.

 One of the most interesting types is artistic welding. Here the distinction is not based on the device used (the one that is more convenient at the moment is used), but on the aesthetic perfection of the created structures. The welder-artist is obliged to make the most thin, but at the same time exceptionally strong and stable seams. Artistic welding techniques are suitable for forming:

1.  wickets;
2. fences;
3. gates;
4. decorative figures;
5. household items;
6. facade structures and a number of other things.

 In working with pipes, the induction method is now increasingly used. This is electric welding, in fact, but with an important feature-you need to supply high-frequency currents. The technique allows you to work with a variety of grades of alloy steels. The electricity consumption for the same volume of the processed metal is noticeably less (however, the spreading of current over the entire surface devalues this result). Contact current lines are most often used.

 The ring induct or can be located inside the workpieces being processed or outside them. Sometimes rod inductors are also used. They allow you to significantly reduce the current consumption. Another advantage is that due to the use of several inductors, the degree of heating can be varied. It should be taken into account that maintaining a uniform gap is one of the most difficult problems.

 The extrusion technique is mainly used for welding polymers. It is suitable only if the workpieces are made of identical thermoplastics.

 The slightest dissimilarity of the composition turns into insurmountable difficulties. The connection of thick-walled tubular parts is provided. The pace and quality of welding will be very high.

  Features:

 the surfaces to be welded should form a "groove" or "angle" between the sheets;

the pressure is applied through an additive (usually a welding shoe);

in some cases, a heat gun is built into the extruder, effectively warming up the air.

 Thermal classes

 Arc

It is this type of welding technologies that most often "works" on construction sites and industrial facilities. The electric discharge warms up to such an extent that even the best gas burners are completely inaccessible. Under the influence of the arc, a welding bath is formed, during the subsequent solidification of which a weld is generated. But behind this apparent simplicity there is a very thorough work, and a welder's mistake can lead to very unpleasant consequences

 Arc welding happens:

 manual;

partially automated;

fully automated (the higher the degree of automation, the greater the requirements for the qualification of performers and the quality of equipment).

 Gas station

There are various methods of welding with combustible gas. But all of them, no matter what gas is used, and no matter what task is solved, are definitely ahead of electric welding in terms of mobility and flexibility. You can work almost anywhere where you can put the cylinders, stretch the hoses. At the same time, however, even the most massive combination of acetylene and oxygen is more expensive than electricity. Other gases cost even more.

 It is important — gas welding is much more effective than arc welding in relation to:

•  copper;
• lead; cast
• iron;
• brass products and structures

Its full name is electron beam welding. As it is easy to guess, the energy of electron beams produced inside the cathode tube is used here. Such a method has appeared relatively recently, but is being rapidly improved, and its scope of application will only expand in the coming years. Since the electron beams are very strongly delayed by air, high efficiency is achieved only in vacuum chambers.

 Of course, this greatly limits the ability to perform the task outside of equipped industrial sites.

 Thermite

This method is used when it is necessary to work outside of a well-equipped settlement, and for some reason gas welding is impossible. Heating is provided by thermite (hence the name), that is, a combination of various substances in the form of a powder. When it is burned, a huge amount of heat is released. The temperature during ignition rises to 1350 degrees in a short time. It is possible to achieve ignition of the thermite mixture:

 with the help of an exploding pyropatron;

a short but powerful electric discharge;

due to a special initiating cord.

Important: there is no need to obtain atmospheric oxygen for the reaction. The required amount of oxidizer is directly in the composition of the mixture. Therefore, welding in an inert gas environment is realized much easier than it can be imagined. The main requirements for the welding process are fixed in GOST 2016.

 Thermite welding is widely used in various branches of mechanical engineering.

 Electroslag

 Despite the seemingly strange and even "garbage" name "electroslag welding" is a very useful procedure. This technique allows you to weld blanks and structures of almost any thickness, which the RD (manual arc) technique is completely incapable of. The current is supplied through a bath of molten slag. In most cases, they work "in the lower position", because it is as convenient as possible. For electroslag welding, they are used:

 fusible mouthpieces;

wire-based electrodes;

large cross-section electrode instruments.

Electroslag welding guarantees a very high productivity of the welder. It is also worth noting:

 

impressive savings on flux, which requires a little;

reduction of current consumption by several times in comparison with electric arc flux and manual electric welding;

minimization of welding defects (of course, if the procedure is performed correctly);

mandatory further processing of the seam at high temperature (otherwise the optimal operating parameters will not be restored).

 

Electroslag welding (ESW) is used to work with:

 

castings and forgings;

titanium and alloys based on it;

various brands of heat-resistant steel;

metal with a thickness of 2 to 300 cm;

nickel-based alloys.

We will complete the characteristics of electric welding by the reverse-stage method. The essence is simple: the seam is first divided into consecutive sections. Then they are scalded one by one, moving in the direction of reducing the length of the seam. Important: you should select exactly the same areas in size.

 This technique is designed to reduce the risk of warping and the formation of other deformations that greatly spoil the life of welders.

 Magnetron sputtering systems

 

Blacksmith Shop

This technique is recommended for working with low-carbon steels (ferrous metal). Using it for high-carbon metal is almost impossible. Forge welding has been practiced for several thousand years, during which time, of course, it has been honed to the smallest detail. This method is used to:

 make sculptures and many other decorative products;

perform urgent repair of parts of various machines;

produce plows, axes and other improvised agricultural tools;

get small downpipes.

 Contact information

The surfaces that need to be connected are simultaneously heated and squeezed. It is possible to process a single connection in a fraction of a second. With any other welding methods, there is nothing to dream of such a thing. There is no need to use oxygen, protective gas, vacuum chambers, additives and electrodes. Everything is relatively simple and environmentally friendly, but the equipment is expensive and is designed for at least 1000 A.

 Diffusion

 Those who know the physical terminology will immediately understand that we are talking about a compound due to mixing of layers at the molecular level. In most cases, this is provided by induction heating. Welding is carried out at a temperature that provides rapid plastic deformation. Under pressure, the surface contact is as tight as possible. It is better to maintain the pressure at the level of the yield strength of the substance.

 A controlled atmosphere based on:

1.  of helium;
2. argon;
3. purified nitrogen;
4. pure hydrogen;
5. combinations of 92-94% nitrogen with 6-8% hydrogen.

Mechanical classes

Friction welding

 This type of welding was invented in our country, in the mid-1950s. Its characteristics are best suited for the aircraft industry and the construction of cars. Friction welding is about the same as pressure welding. The rubbing surfaces are warmed up, which provides the necessary thermal impulse. The maximum effort always develops at the very end, when there is a forging.

 Important: all those films of fat, oil that remained on the treated surfaces eventually disappear anyway, so you can not be afraid of problems due to not too high-quality preparation.

 Cold

This name has a particularly strong type of glue. It should be understood that the same quality as the "hot" method cannot be provided. There are two-component and one-component compositions. They also distinguish:

1.  liquid;
2. plastic;
3. universal types.
4. Experts recommend:

 protect foreign surfaces with masking tape;

carefully dose the composition;

pre-remove all dust and dirt.

 Ultrasonic

 High-frequency sound vibrations provoke a voltage that gradually exceeds the elastic limit. The absence of strong heating is a clear plus. You can safely weld metals of various compositions. Successful welding of thin and especially thin blanks is ensured. The procedure is easily automated.

1.  Ultrasonic welding:
2.  it is produced very quickly;
3. suitable for polystyrene and other polymers;
4. allows you to create non-woven materials;
5. it strongly depends on the damping coefficient of vibrations in the material;
6. it makes it possible to connect plastic with metal.

 Explosion welding

This technology is used to produce bimetallic blanks. It is allowed to work with a variety of materials. Important: there can be no precise calculations and clear modes here. The reason is simple — the approach itself is not fully developed. The control of the blast wave is very complex, it is necessary to conduct many experiments before the necessary experience is accumulated.

 Explosion welding is possible in both air and vacuum environments. The speed of movement of the plates reaches several hundred meters per second. The explosion makes it possible to perform cladding of steels with exceptional properties. Another important advantage is the ability to produce blanks of unlimited scale. However, it is impossible to automate welding by explosion by 100%.

 At the same time, it is potentially dangerous for the employees present.

 Process

Welding with your own hands in an apartment or garage can be performed in a very large number of cases. But before you start working, you should thoroughly study it, get acquainted with a number of subtleties that lie in wait in various cases. A common mistake of many beginners is the idea that they can perform connections without drawings, relying only on their little experience and intuition. Tellingly, high-class professionals never do this. On the contrary, they carefully check all the drawings and technical specifications, consult with other people if necessary.

 When welding metal, there may be various defects in the production of works. Any specialist is obliged to know all of them and take into account preventive measures, understand how to deal with such problems. The main danger is represented by:

•  violations of the integrity of the metal layer;
• poor shape of the suture roller;
• too large or too small grains in the phase transition region;
• cracking (due to poor temperature conditions);
• undercuts (against the background of an excessively high arc voltage or a shift of the melt baths).

At large enterprises, welding carriages are increasingly used. Such equipment is often used in shipyards. Some copies are equipped with a pair of burners, which significantly increases the efficiency of using the equipment. As for cutting the edges of the product for welding, this procedure is very important both for manual and industrial work. This is the only way to ensure reliable contact. The exact requirements for cutting edges are fixed in GOST for a specific format of work.

 Often welders use ceramic linings. Such products facilitate the welding of complex joints in hard-to-reach areas. Thanks to the lining, there is no need for complex preparation and subsequent processing. But the quality of the substrate is critically important! Also, in a number of situations, a universal welding plate is used, which provides accurate positioning of large and small parts.

 As an additive, including when welding the "automatic" box, the steering tip, the ICE blocks, you can use the welding wire "prima". It guarantees:

 good copper plating;

stable chemical composition;

efficient processing of low-alloy alloys in a carbon dioxide cloud.

For connection to the oxygen cylinder, during gas welding, only a hose designed for a suitable pressure level can be used. Inspection of these hoses is carried out daily before the start of work and at its end. If the site was left unattended for some time, you need to inspect everything again. Note: if possible, it is better to abandon the use of carbide, and it is much safer to purchase factory — made acetylene.

 When selecting a welding converter, you should not focus on reliability — it is still less than that of other devices for electric welding. However, this technique is supported by its immunity to voltage drawdowns. Such a circumstance is very important on construction sites. Finally, it is worth analyzing a few subtleties of working in specific cases. In some cases, it is necessary to weld pipes with a different number of bends – this is a really difficult task.

 Required by all means:

 control the amount of edge shift;

center the products;

cook the first seam on direct current.

 Quite often, silumin welding is needed. It is processed strictly under argon protection! Only silumin of foundry brands is subject to processing, but not of other varieties. Welding of the ceiling seam is carried out at a limited current, therefore it is important to take measures to avoid non-welding. The electrode is driven slightly sideways to weaken the spreading of the metal, and the edges of the workpieces are cleaned as well as possible.

Welding of corner seams can also be carried out in horizontal placement. It is necessary to connect the structures strictly at 90 degrees. If the thickness is less than 1.4 cm, it is not necessary to mow the edges. But with a thickness of more than 4 cm, a double-sided bevel is already required. When creating a T-joint, you should carefully avoid the appearance of:

pores;

poorly cooked areas;

craters.