Do-it-yourself thermite pencil. Thermite welding. Application in industry and everyday life. Thermite pencil. General information and composition

Thermal action on individual parts of metal structures allows them to provide a high-strength connection. Thermite welding is a well-known and simple type of these work, which is easily performed at home even by craftsmen with minimal experience.

Technological features

Thermite or powder welding GOST 2601-84 is a type of cooking, in which termites serve as a heat source, is used to connect rails, ECP, etc. Termite is a powder mixture of various metal materials, in particular, aluminum and magnesium and iron dross.

There are such types of thermite welding:

Crucible (aluminum-thermal);
Muffle.

The crucible is used to create ground loops and when connecting small diameter electrical cables. The technology involves the use of a thermite mixture in the ratio of aluminum / iron in the proportions of 23/70. When the termite is completely burned, iron is released, which is used to join the joints. The combustion process itself depends on the grain size of the thermite powder. When working with copper or other compounds, sometimes other metal compounds are added to the powder to increase the strength of the seam.

Photo - work on rails

Aluminum is used when it is necessary to create a surfacing on the surface of a certain structure, to repair tram rails or when working with fragile materials. One of the key advantages of this technology is the ability to weld cast iron using the weldless method.

Photo - schematic diagram

At the same time, crucible welding cannot be used to join aluminum, therefore muffle welding is used here. The peculiarity of the muffle operation is such that, upon direct contact, the high melting temperatures of the termites contribute to the evaporation of certain areas of the aluminum compounds. Therefore, to create such mounts, it is necessary to use pads or thermite cartridges. These sockets make it much easier to work with solid and stranded wires. They are a tip equipped with a metal chill mold. The difference between the muffle type and the crucible type is that liquid-type welding products do not appear during operation. Magnesium, under the influence of high temperatures, does not spread over the surface to be joined, but is absorbed into it, forming a seamless connection.

Photo - seam

Aluminum cables require exposure to flux prior to thermite welding. It will dissolve the oxide film that interferes with the welding of individual parts of the aluminum, but can cause rusting of the wires. Therefore, professionals rarely use this technique. To connect this type of cable, chill molds or filler rods are used, into which the ends of the wires are inserted and heated to the desired temperature.

Photo - types of thermal effects

Thermite welding, which contains magnesium, is used to process small-section wires (telephone, Internet cables), various electrical connections etc. To create a termite requires about 20% magnesium or aluminum in the mixture and 80% iron (its scale). At the same time, the main source of oxygen in the process is iron oxide, and heat is released by the pure metal.

Dignity:

Simplicity. This technology of joining joints of steel, aluminum, cast iron and other metals can be used even by beginners in welding. The work does not take much time and is carried out with compact equipment, which is convenient to store at home;
Termites provide excellent connection quality. The joints are strong and durable. When working with aluminum, to reduce corrosive processes, fluxes of the VAMI type are used;
Availability. Thermite welding equipment does not need a lot of electrical energy.

Photo - termite mixture

But this type of welding also has certain limitations:

To carry out this type of welding, auxiliary and preparatory processing of metal structures and cables will be required;
The welding process cannot be traced, so only professionals with NAKS certification will be able to work with seamless equipment.

Process

For thermite welding, special equipment is required. It:

Crucible equipped with a drain;
Thermite pencil. A very handy device for doing work at home. It does not need to be heated, baked or melted down. After plugging into the network, the device is already ready for use;
Devices for supporting and clamping welded structures;
Cutter, metal saw, inverter torch, thermometer;
Other additional tools (abrasive wheel, wire brush).

Let's look at an example of how aluminum-based termite welding is carried out. To ignite such a powder, it is necessary minimum temperature 1300 degrees. Under its influence, metal structures evaporate, microcracks form on their surface. Heated aluminum is able not only to restore the metal, but also to provide a tight and durable connection of individual parts. The parts to be joined are fixed in a form that can be made from improvised means or bought in a special store. Parts are processed by the selected type of welding, cooled and cleaned.

Photo - termite powder

Thermite welding for rails, cables, etc. is of the following types:

With intermediate casting;
End-to-end;
Combined;
Duplex.

During intermediate casting, thermite powder becomes a liquid metal when exposed to high temperatures. The melted mixture has the same characteristics as its solid (powder) form. During this, the connected parts of a separate metal structure are fixed in a special shape. Termite is poured into it, due to which the metal parts are melted and joined. It should be noted that the duplex layout is very similar to intermediate casting. The process is identical, except that after the termite is poured into the mold and solidified, the resulting joint is additionally pressed.

Photo - welding process

Termite butt welding is used to connect various plates, cathode and drain leads, and other similar elements. Before starting work, parts of the structure are fired in a furnace, while the termite is fired in another crucible. After that, the metal structures are crimped with a press and welded with fired thermite powder. The technique involves careful processing of the edges and ends of the plates, so it is rarely used at home.

For the welding of rails, switch mechanisms, etc., a combined technique is used. Here, end-to-end and under-molded welding is combined. Before starting work, the rails are cut to create sharp edges. A steel plate is installed between the individual parts of the rails, which is pressed into them using a powerful press. Accordingly, a small gap is formed at this place, into which liquid thermite is poured under pressure. After it has solidified, the seam is additionally processed and welded.

Photo - mold for rails

Video: how to conduct thermite welding
https://www.youtube.com/watch?v=VMUOrfl-JcY

Safety engineering

Regulations indicate that, despite the apparent simplicity, thermite welding is a difficult and dangerous type of work. Consider the security requirements:

Thermite powder can only be stored in heated, ventilated rooms;
Do not use wet termite;
If welding work is carried out outdoors, then the joint is cleaned from snow, dirt and other foreign bodies in a diameter of 50 centimeters;
It is impossible to weld if the thermometer dropped below 10 degrees;
Do not ignite the charge from the arc;
The instruction for the use of thermite inverters requires filling the thermite with sand when burning, equipping the oxygen line with an additional protective valve and turning off the supply of the combustible mixture in the event of a burner breakdown;
The welder must wear a special suit.

You can buy equipment for thermite welding in a special store, its price depends on the type and brand of the inverter. For example, the price of such a welding machine in Voronezh and Krasnoyarsk starts at $ 500.

Technological features

There are such types of thermite welding:

Crucible (aluminum-thermal);
Muffle.

Photo - work on rails

Photo - schematic diagram

Photo - seam

Photo - types of thermal effects

Thermite welding, which contains magnesium, is used to process small-section wires (telephone, Internet cables), various electrical connections, etc. To create a termite, about 20% magnesium or aluminum in the mixture and 80% iron (its ). At the same time, the main source of oxygen in the process is iron oxide, and heat is released by the pure metal.

Dignity:

Simplicity. This technology of joining joints of steel, aluminum, cast iron and other metals can be used even by beginners in welding. The work does not take much time and is carried out with compact equipment, which is convenient to store at home;
Termites provide excellent connection quality. The joints are strong and durable. When working with aluminum, to reduce corrosive processes, fluxes of the VAMI type are used;
Availability. Thermite welding equipment does not need a lot of electrical energy.

Photo - termite mixture

But this type of welding also has certain limitations:

To carry out this type of welding, auxiliary and preparatory processing of metal structures and cables will be required;
The welding process cannot be traced, so only professionals with NAKS certification will be able to work with seamless equipment.

Process

For thermite welding, special equipment is required. It:

Crucible equipped with a drain;
Thermite pencil. A very handy device for doing work at home. It does not need to be heated, baked or melted down. After plugging into the network, the device is already ready for use;
Devices for supporting and clamping welded structures;
Cutter, metal saw, inverter torch, thermometer;
Other additional tools (abrasive wheel, wire brush).

Let's look at an example of how aluminum-based termite welding is carried out. To ignite such a powder, a minimum temperature of 1300 degrees is required. Under its influence, metal structures evaporate, and microcracks form on their surfaces. Heated aluminum is able not only to restore the metal, but also to provide a tight and durable connection of individual parts. The parts to be joined are fixed in a form that can be made from improvised means or bought in a special store. Parts are processed by the selected type of welding, cooled and cleaned.

Photo - termite powder

Thermite welding for rails, cables, etc. is of the following types:

With intermediate casting;
End-to-end;
Combined;
Duplex.

Photo - welding process

Photo - mold for rails

Video: how to conduct thermite welding
https://www.youtube.com/watch?v=VMUOrfl-JcY

Safety engineering

Regulations indicate that, despite the apparent simplicity, thermite welding is a difficult and dangerous type of work. Consider the security requirements:

Thermite powder can only be stored in heated, ventilated rooms;
Do not use wet termite;
If welding work is carried out outdoors, then the joint is cleaned from snow, dirt and other foreign bodies in a diameter of 50 centimeters;
It is impossible to weld if the thermometer dropped below 10 degrees;
Do not ignite the charge from the arc;
The instruction for the use of thermite inverters requires filling the thermite with sand when burning, equipping the oxygen line with an additional protective valve and turning off the supply of the combustible mixture in the event of a burner breakdown;
The welder must wear a special suit.

Question of M. Gorbachenkov, Moscow

In one of the issues of "Do it yourself" was published material about thermite welding. Could you return to this topic and talk about thermite welding in more detail? I am interested in everything from the method of producing small aluminum filings to the chemical composition of the fluxes used in this process. But I am especially interested in the possibility of replacing the incendiary composition of berthollet salt with some other substance. Since this salt is extremely difficult to get.

V. Pronzhenko

SIMPLE THERMITE PENCIL

(with seed)

Homemade thermite pencils ("electrodes") are applicable for welding metal structures in the field, that is, in places where there are no suitable energy sources (in the country, at home, on the road). I would advise every motorist and motorcyclist to always have them in their arsenal.

What is this homemade "electrode"? Its basis is a piece of wire made of ordinary carbon steel of the lowest quality with a carbon content of less than 0.22% (Fig. 1). The diameter of the wire (2. ..5 mm) depends on the thickness of the parts to be welded. The termite itself consists of 23% aluminum sawdust (silumin is not suitable!) And 77% iron scale, the particle size of which should not exceed 0.5 mm. And let the reader M. Gorbachenkov not worry about the problem of where to get the aluminum sawdust, since they will be completely replaced by the commercially available aluminum powder for obtaining the silver paint. Dross and sawdust (powder) are tied with glue (BF-2, "Moment").

On one side of the termite pencil, a seed is applied, which acts as sulfur on ordinary matches. It consists of 2 parts of berthollet salt (KSU 3) and 1 part of fine aluminum sawdust (parts are taken by weight). The binder for Berthollet's salt and aluminum filings is the same as for the termite electrode.

Now we will tell you how a thermite pencil is formed (made). All three components of the termite (scale, sawdust and glue) are mixed well in glass or porcelain (earthenware) dishes, after which the resulting composition (it should have the density of sour cream) is evenly applied to the prepared piece of wire with an ordinary stick, or the wire is rotated over the dishes, little by little " winding "thermite composition on it.

It is not difficult to make a simple adaptation-form to obtain a dozen "electrodes" at once. To do this, a suitable corrugated aluminum strip is nailed onto the wooden base. If there is no such strip, bend it yourself. Two aluminum "walls" are tightly pressed to the ends of the mold, in which holes are provided for installing wire rods of the

Puc.l. / - wire;

Termite "electrode" 2 - thermite; (pencil): 3 - seed

Today we will talk about how we can connect to each other, figuratively speaking, two pieces of metal, if there is no welding machine at hand. There are moments, especially in your home, when you need to weld something small and insignificant, but badly needed. You will not, for example, weld a couple of metal rods to, buy welding machine? After all, it is not cheap. But, do not give up and run around the village, bullying neighbors for finding them necessary equipment... Everything can be solved much easier, namely, to make a homemade termite pencil. Of course, for this you still have to visit special shop to purchase all the ingredients you need to make a termite pencil. But, the costs for you in this case will be practically zero, compared to the purchase of a welding inverter. So let's get started.

Ingredients of thermite stick for metal welding

To make a thermite pencil, we need to find a piece of carbon steel. On this wire, we will apply the thermite mixture. The thermite mixture is very thickly mixed with nitrocellulose glue, which dries much faster than any other glue. By the way, I forgot to say, the wire must also be selected by diameter. If your welded ones are quite massive, then the wire, respectively, needs to be taken thicker. And vice versa. If the parts are small and light, then thin wire can be used. Typically, the thickness of the wire for a thermite pencil varies from two to five millimeters, depending on the massiveness of the parts being welded.

And now, so to speak, the composition of the termite mixture. We need aluminum sawdust, which will make up 23% of the total mass of the prepared termite mixture. As well as 77% iron scale powder. The size of aluminum chips and dross should not exceed 0.5 mm. After we apply the thermite mixture to the wire, we need to equip its end with a special seed, a kind of match head. For the seed mixture, we use Berthollet's salt and aluminum sawdust in a 2: 1 ratio by total weight. The seed is also mixed with glue. So. The wire was coated with a layer of thermite mixture. A seed mixture was applied to the tip. Dried it all out and got a termite pencil. It will somewhat resemble a sparkler.

Thermite reaction (from the ancient Greek therm - heat) - the process of combustion of a termite, consisting of a mixture of aluminum (or magnesium) powder with various oxidized metals (most often it is iron).

The reaction proceeds with intense heat release. The temperature of thermite combustion is more than 2300 degrees Celsius and as a result of its combustion, metal and aluminum slag are formed. If we delve deeper into the history of the discovery of the process, then for the first time the reaction was received by the Russian researcher N.N. Beketov. The scientist saw the practical use of termite mainly in the production of steels. However, the thermite reaction became popular almost half a century later thanks to the work of a German chemist (literally "goldsmith"), who suggested using it for welding railroad rails. Goldschmidt developed a welding technology, drew drawings of a crucible in which a high-temperature mixture is burned.

The use of thermite welding made it possible to obtain a durable and reliable weld without technological lack of penetration, and the effectiveness of the method made it possible to introduce it on an industrial scale.

Welding by means of an aluminothermic reaction is still used today in the construction of railway tracks. Thermite welding - simple and effective method obtaining continuous welded joints at minimal cost. It can also be used to weld reinforcing bars in construction, power transmission lines (PTL) wires, and large steel and cast iron parts. Metal surfacing is used to repair worn-out parts of parts. For example, you can "build up" a worn out or chipped gear tooth.

The termite reaction is written with the following formula:

Fe2O3 + 2Al => Al2O3 + 2Fe + 760 kJ, where

Fe2O3 - trivalent iron oxide (visually looks like ordinary rust);
2Al - aluminum powder;
Al2O3 - slag composition;
Fe is pure iron.

The reaction is very violent and lasts 15-30 seconds. From one kilogram of termite, 0.55 kg of metal and 0.45 kg of slag are obtained. For welding, thermite mixture is prepared mainly in the following proportions: 1/4 - powdered Al and ¾ - iron oxide. Termite is additionally alloyed to obtain a welded joint with specified fur. properties and filled with steel scraps to increase the quantitative yield of molten reaction products.

For the formation of liquid metal, molds are used, consisting of two split halves. Welding is performed with casting metal, which melts the edges of the parts and fills the gap between them. The size of the gap is 10-15 mm.

There are two methods of welding: the first allows you to save termite consumption, the second - to increase the speed of work.

In the first case, the connection, on which the mold is pre-installed, is heated with a burner, which is supplied through its upper part, to T- (850 -900) degrees Celsius. Upon reaching the temperature, the molten composition is kept for 5-6 s and descends into the mold.

The second case does not imply the use of preheating (thanks to which time savings of 15-20 minutes) of the welded product with a gas-flame burner. The metal of the welded joint is heated by the termite itself, which is burned in an increased amount (in the foundry, a similar technique is also used when the chill mold is heated by the metal itself, for example, in aluminum gravity casting). Here welded joint formed by casting overheated metal. The crucible part is separated from the poured volume by a metal shutter. The thickness of the flap is calculated so that it melts before the end of the process.

Parts must not contain moisture. Water will cause metal to splash. Thermite welding operators should be familiar with the safety rules. They must wear PPE: high temperature-resistant transparent glasses, special shoes, clothes treated with a fireproof compound (read the article).

Termite at home. (welding without welding machine)

In one of the episodes of the action-packed series Breaking Bad, the thermite compound helped the protagonists open the door of the warehouse where barrels of substance for the synthesis of methamphetamine were kept. We in no way suggest that you follow Walter White and commit any illegal / illegal actions (unless you can open your personal safe using traditional methods). Nevertheless, this is a vivid Hollywood example of the fact that the thermite reaction can be used not only in industrial / production, but also for domestic purposes. If with the help of termite it is possible to smelt metal (cutting), then the reverse process - welding - is also fair.

For example, with the help of a very simple invention called the termite pencil, two iron parts can be welded in the field without electricity. The method is convenient in the country if the electricity is turned off or if you need to cook something without having to purchase an inverter and spend some money on it.

Making a pencil with your own hands is very simple. We find on the farm or buy a metal bar (most likely you will come across ferrous metal - low-carbon steel, as it is most often found), or we cut it from a wire. They take a rod of ø2-5 mm, depending on the thickness of the product (the thicker it is, the larger the diameter of the rod) and apply a coating mixed with glue. The coating is 23-24% aluminum powder and 76-77% ferrous oxide. Particles of these two components should be of a fine fraction no more than 0.5 mm.

In order for the mixture to stick to a metal rod, add nitrocellulose or synthetic glue (quick-drying) to it and stir it all to a paste.

The coating is applied as follows

You need to roll a cylinder out of tracing paper. His inner diameter should be 3 times the diameter of the bar. Next, it is filled with a pasty composition, into which a steel bar is inserted in the center. After the coating dries and adheres to the metal part, you can cut the paper stationery knife and use a termite pencil.

Note.

Previously, the template was made from tracing paper, which was a transparent paper used by draftsmen to copy drawings on a draloscope (light table). In connection with the development of copying technology, draloscopes went down in history, like tracing paper. Although she may remain with someone from her student days. Be that as it may, if you do not have tracing paper, it seems to us that foil can be used in place of it.

The end of the pencil can be primed to make it easier to ignite. The seed consists of berthollet salt and aluminum powder in a 2: 1 ratio. The seed can be made separately in the form of an ignition match, and also not be used at all, using a sparkler for igniting. The easiest way is to set the pencil on fire with gas burner which have now become very portable.

As mentioned above, the combustion temperature of the termite is very high. The reaction will proceed with intense heat generation and splashing of molten metal. And this is no longer a joke. You need to think about your health, stock up on personal protective equipment. Use protective goggles (read about) and clothing made of thick fabric (in no case should you wear synthetics -).