The main methods and types of soldering. Soldering equipment, materials and soldering technology. Special Welding and Soldering Methods Welding Brazing

Applicable:

capillary soldering. The solder fills the gap between the surfaces to be joined. Solder and metal do not chemically interact. This is the most common soldering method.
Diffusion soldering - long exposure at high temperature. There is a hardening of the seam due to the mutual diffusion of the components of the solder and the base metal. There is no chemical interaction, a solid solution is formed.
Contact-reactive soldering. In this case, active reactions take place between the parts to be joined or between the parts and the solder, with the formation of a low-melting joint in contact.
Reactive flux soldering. The weld is formed by a displacement reaction between the flux and the base metal.
Soldering - welding, the seam is formed by welding methods, but solder is used as a filler material.

Soldering methods are determined by the chemical properties of the solder, flux and metal and the soldering mode (temperature, time, etc.) Depending on the heat source, soldering is carried out in the following ways:

soldering in furnaces;
resistance soldering;
induction soldering;
soldering with soldering irons;
soldering with gas burners.
soldering by immersion in molten solder;

Metal alloys are most often used as solder.

Basic requirements for solders:

1. Have a melting point at least 50-100 o C below the melting point of the soldered metals.

2. Provide good wetting of the metal and good filling of the solder seam.

3. Form strong, ductile and corrosion-resistant seams.

4. Have a coefficient of linear expansion that does not differ sharply from the coefficient of linear expansion of the soldered metals.

Solders are divided into two groups: soft (melting point below 500 o C), and hard (above 500 o C).

Soft soldering gives relatively low mechanical strength and is used for parts operating at low temperatures and small vibration shock loads: radiators, fuel tanks, electrical wires, etc. The most common tin-lead (tin in its pure form as a solder is not used) solders (the number in the name of the solder indicates the content of tin in it): POS-18 (17-18% tin, 2-2.5% antimony and 79-81% lead) is used for soldering non-critical parts; POS-30 and POS-40 - for seams with sufficient strength and reliability, POS-50 and POS-61 - for parts whose seams should not oxidize during operation (electrical equipment, etc.).

Hard soldering is performed when it is necessary to have a strong seam or a seam that operates at high temperatures (fuel and oil lines, relay contacts, etc.). Hard solders include: copper, copper-zinc, brass, aluminum and silver. Copper-zinc solders (the first figure in the name of the solder indicates the content of copper in the solder, the rest is zinc and a small amount of impurities): PMC-36 - for soldering brass products; ПМЦ-48 - for parts made of copper alloys that are not subjected to shock loads and bending; ПМЦ-54 - for soldering copper, bronze and steel that are not subjected to shock loads.

To obtain an elastic and durable connection, brass L-62 and L-68 are used as solders. (copper alloy with zinc - up to 80%, with additions of aluminum, lead, nickel - up to 10%).

For soldering critical structures, silver solders are used: PSR-12 (36% copper, 12% silver, no more than 1.5% impurities, the rest is zinc); PSr-45 for soldering brass, copper and bronze (contacts for parting electrical equipment); PSr-70 for soldering electrical wires that require low electrical resistance at soldering points.

For soldering parts made of aluminum and its alloys, aluminum-silicon solders (silumins) and aluminum-copper alloys (34A and 35A) are used. Solder 35A has higher mechanical qualities and a higher melting point than 34A.

Fluxes are used to remove oxide films from the surface and protect them from further oxidation, which either dissolve oxides or chemically interact with oxides and which float to the surface of the weld in the form of slag. Fluxes also help to improve the wetting of surfaces with solder. The melting point of the flux must be below the melting point of the solder.

When soldering with soft solders, ammonia (or ammonium chloride), an aqueous solution of zinc chloride and ammonium chloride with a concentration of 20-50% are used. Hydrochloric acid is not used as a flux, but an aqueous solution of zinc chloride is used, which is obtained by etching an aqueous solution of hydrochloric acid with zinc:

HCl + Zn2 → ZnCl2 + H2.

To prevent further corrosion of soldered parts, rosin is used, which must be applied to the place of soldering, but not to the soldering iron, because. when overheated on a soldering iron, it can lose its fluxing properties.

When soldering with hard solders, borax or its mixture with boric acid and boric anhydride is used as a flux. By selecting the amount of boric anhydride, the melting point of the flux is changed.

Soldering parts with soft solders is most often performed using soldering irons (copper and electric), and with hard solders - gas burners or induction heating. The working part of the soldering iron is rubbed with ammonia to remove oxides, tinned. The surface of the seam is degreased with flux, the soldering iron melts and the solder is transferred to the place of soldering and evenly distributed over it.

The parts of the undercarriage of construction and road machines have a very large wear. In this case, to restore them, it is advisable to use liquid metal pouring (cast welding), since. other methods (automatic surfacing, setting bandages, etc.) do not provide good quality and are very expensive.

The part is heated and placed in a chill mold, also heated to 200-250 ° C. Liquid iron or steel is poured into the mold through letniks, which fill the space between the worn part and the mold wall, metal is welded to compensate for wear. Undercarriage parts do not require post-machining. Compared to other methods, the cost of restoration is reduced by two to three times, and the durability is at the level of a new part.

lot

Soldering operations are quite common not only in professional areas in production and construction, but also in everyday life. They are used to obtain interatomic between small parts and elements. There are different types of soldering, differing in technological nuances, consumables used, workpieces, etc.

General information about technology

This is a joining method that uses a bonding melt (solder) with characteristics suitable for specific conditions. Both the active soldering element and the workpieces are subjected to preheating, which forms a structure of materials that is malleable for joining. The temperature regime must exceed the peak heating point, bypassing which the metal parts soften and begin to transition to a liquid state. An important characteristic of any type of soldering is the thermal exposure time under the melt. This is the interval from the start of heating to the hardening of the solder after the connection is made. On average, the operation takes 5-7 minutes, but there may be deviations from this range - it depends on the characteristics of the workpiece and the area of the processed unit.

Soldering lamps

The most common tool for soldering various workpieces, which allows you to get high-temperature heating by burning alcohol, kerosene and other types of liquid fuels. In the process of operation, a flare fuse escapes from the nozzle of the apparatus, which is subsequently directed to the target area of the melt. Such devices can be used not only for joining parts, but also for heating structures and mechanisms. Also, soldering machines are used before removing paintwork. The average heating temperature of a lamp soldering iron is 1000 - 1100 ° C, so it can also be used in welding. The most productive models include gasoline lamps. They quickly reach optimum operating temperature and handle most standard soldering operations. The design of the devices provides for a cartridge for fuel, as well as a flame regulator that allows you to vary the power of thermal exposure.

Soldering torches

A wide range of gas soldering irons that can be connected to a fuel canister or to a central fuel source. The first supply option has the advantage of autonomy. A burner with a spray can, as well as can be used regardless of external communications. When choosing such a device, one should take into account the power, operating temperature, type of gas used, ready-to-work time, etc. For example, a standard gas soldering torch runs on propane-butane and reaches a heating temperature of up to 1300°C. The period of continuous thermal exposure can reach 3 hours, but this time will also depend on the volume of the connected cartridge. Burners are also distinguished by the type of ignition system. The simplest models are switched on mechanically, and in more modern modifications, piezo ignition is used.

Electric soldering irons

It is also a common type of soldering equipment in the domestic environment, which is safe (compared to gas appliances) and compact in size. But it is worth emphasizing the shortcomings as well. Firstly, such devices are dependent on the mains, which limits their scope. Secondly, electric soldering equipment maintains a low heating temperature in the range of 400 - 450°C. This is due to the fact that part of the energy is lost in the process of converting electricity into heat.

When choosing a device, the maximum voltage must be taken into account. So, in workshops and industries, standard 220 V models are used. In domestic conditions, devices operating from 12 and 24 V transformers are often used. Tasks that can be solved with electric soldering irons are mainly limited to repairing small equipment, restoring microcircuit contacts, connecting plastic parts, etc.

Soldering stations

To perform batch or in-line soldering operations, multifunctional equipment is used. The soldering station is characterized by a wide range of adjustment options for operating parameters, as well as higher heating temperatures. Suffice it to say that devices of this type operate at a power of 750 - 1000 W, connected to networks with a voltage of 220 V. As a rule, these are professional soldering equipment, but there are also household counterparts. For example, devices for group operations at home may include several interchangeable tips of different sizes, stands, desolderers, wire cutters, and other auxiliary accessories. Now it is worth getting acquainted with different technological approaches to soldering processes.

The main types of soldering

There are techniques for performing operations on the joint and clearance. So, if the gap between the connected elements is less than 0.5 mm, then the soldering will be with a gap. Exceeding this interval means that the connection is made end-to-end. Moreover, the joints can have different configurations - for example, X- and V-shaped. Gap soldering is performed only with liquid solder, which is sent to the intermediate zone during operation. butt soldering involves filling free space with solder under the influence of gravity.

Classification of soldering by temperature conditions

To date, soft, hard and high-temperature soldering is used, which is used mainly in manufacturing and construction. The first two techniques are similar in many respects - for example, in both cases, the operating temperature is 450 ° C and below. For comparison, high-temperature connections are made in the mode of at least 600°C, and more often - above 900°C.

At the same time, low-temperature processing can provide a high-quality connection. The most advantageous will be the use of hard solder, due to which high strength and refractoriness of parts are achieved. Adding copper to the gap or joint will also increase the ductility of the workpiece. If it is required to obtain a flexible and elastic structure, then soft soldering is used.

Solder classification

It is conditionally possible to divide modern solders into two groups:

melting at low temperatures.
Melting at high temperatures.

As already noted, low temperature soldering is performed at 450°C and below. The solder itself for this kind of operation should already soften at 300°C. Such materials include a wide group of tin alloys with the addition of zinc, lead and cadmium.

High temperature melt media are used for soldering at temperatures in the order of 500°C. These are mainly copper compounds, which also include nickel, phosphorus and zinc. It is important to note that, for example, in addition to a lower melting point, it will differ from copper alloys in mechanical strength. The ratio of resistance to physical pressure can be represented as follows: 20 - 100 MPa versus 100 - 500 MPa.

Types of fluxes

Under thermal action, an oxide coating is formed on the surface of the metal workpiece, which prevents the formation of a high-quality connection with the solder. Various types of soldering fluxes are used to eliminate such obstacles, some of which also eliminate traces of rust and scale.

Fluxes can be classified just by compatibility with solders (hard and soft) or by temperature resistance. For example, for soft soldering of heavy metals, products labeled F-SW11 and F-SW32 are used. For solid connection of heavy alloys, soldering fluxes of the F-SH1 and F-SH4 types are used. Light metals like aluminum are recommended to be pre-treated with compounds of groups F-LH1 and F-LH2.

Induction soldering method

This soldering technology has several advantages over the classical hot melt joining method. Among them, one can single out the minimum degree of oxidation of the workpiece, which in some cases eliminates the need to use fluxes, as well as a low warping effect. As for the target materials, they include both soft and hard alloys, as well as ceramics with plastics. For example, the optimal solder for copper in this case will be marked L-SN (modifications SB5 or AG5). As a source of thermal energy during induction exposure, both hand-held lamp devices and machine units of the appropriate power can act. In production, generator sets are also used when it is necessary to obtain a long-term soldering of large-area nodes. Also, a multi-place inductor is included in the work, which can take workpieces in turn. According to this technology, in particular, hand cutting tools are made.

Another modern high-tech soldering method, the development of which was caused by the need to eliminate a number of characteristic shortcomings of electrochemical joining methods. A key feature of this technique is the ability to replace conventional flux as a means of eliminating oxides. The stripping function is performed by the energy of ultrasonic waves, which causes the process of cavitation in the liquid solder. At the same time, the tasks of thermal binding action from the melt are fully preserved.

The superiority of technology in terms of connection speed is also noted. If we compare ultrasonic radiation with the effect that gives tin-lead solder, then the intensity of the collapse of the cavities of the processed node will be several times higher. As observations show, ultrasonic waves with a frequency of 22.8 kHz provide a solder closing speed of 0.2 m/s.

There are also economic advantages of this method. They are also associated with a change in approaches to the use of fluxes and solders. In the production of electrical devices, when assembling monolithic capacitors, current converters and other devices, metallization with palladium, silver and platinum pastes is widely used. The process of ultrasonic soldering allows you to replace precious metals with cheaper analogues without losing the performance of the future product.

Features of soldering-welding

Soldering as such has many similarities with traditional welding technologies. Also used is the heating of the workpieces and third-party material that affects the formation of the seam. But, compared to welding techniques, brazing does not provide for an internal melt of the workpiece structure. The edges of the parts, as a rule, remain solid, although they are heated. And yet, a complete melt of the workpiece gives a stronger connection. Another thing is that to achieve such a result, more powerful equipment may be required. When using liquid solder for copper, non-capillary soldering with dense filling of the seam is quite feasible. This connection method is partly related to welding, since it increases the adhesion of the structures of two or more workpieces. It is recommended to perform non-capillary soldering with electric arc devices or an oxy-acetylene torch.

Conclusion

Obtaining a high-quality joint in the soldering process is influenced not only by the correct choice of technology, solder with flux and equipment. Often, small organizational procedures associated with the preparation of materials and subsequent processing are of decisive importance. In particular, the use of hard solder requires multi-stage cleaning of the target surface using abrasive grinding and chemical attack with carbon tetrachloride. The finished part should be clean, smooth and as level as possible. Directly during the soldering, it is also recommended to pay special attention to the method of fixing the workpieces. It is desirable to fix them in a clamping tool, but in such a way that the latter is protected from chemical and thermal effects.

Do not forget about safety precautions. Active consumables - flux and solder - require special care. For the most part, these are chemically unsafe elements that, under high temperature exposure, can release toxic substances. Therefore, as a minimum, it is necessary to protect the skin and respiratory organs during work.

Welding and soldering are by far the most popular and effective methods of joining metals and their alloys. People who know the basics of soldering and are able to assemble any metal products by soldering, as a rule, know the basics of welding as an alternative way to influence the material, as well as its alloy. Despite this, welding is still different from soldering. In this regard, each method is worthy of careful consideration.

Metal welding: methods and types

General information

Welding is a process of obtaining (mounting) a permanent connection by establishing interatomic bonds between the surfaces of metals and their alloys to be joined under general or local action (heating), plastic deformation.

Today, there are quite a few types of welding (about a hundred). Known species are classified according to physical, technological, as well as technical properties and characteristics. Depending on the form of the energy used, three classes can be distinguished according to physical characteristics.

Thermal;
Mechanical;
Thermomechanical.

It should be noted that the thermal class of parts represents all types of joining of metals and alloys using thermal energy (plasma, arc, gas).

The mechanical class represents all types of welding of metals, as well as their alloys, which are carried out by means of mechanical energy (friction, cold, ultrasonic, and explosion welding).

The thermomechanical class implies the types of welding of metals and alloys, during the application of which pressure is used, as well as thermal energy (diffusion, as well as contact).

The classification of types of welding is carried out according to certain technical features:

By the continuity of the process (intermittent, continuous);
According to the method of protecting the part in the work area (in vacuum, in air, submerged, in gas, in foam, using combined protection);
According to the degree of mechanization (mechanized, manual, automatic, automated);
By the nature of the protection of the part in the area of the arc action on the surface of solid materials (in a controlled atmosphere, with jet protection);
By type of shielding gas (in inert or active gases).

It is worth paying attention to the fact that the technological signs of welding are set for each type separately. In this regard, familiarization with the most popular types of processing, as well as the corresponding equipment, is required.

arc welding

The joining of metals using an electric arc makes it possible to achieve a connection by melting. The parts to be welded are heated by the heat of the electric arc.

Today, four main types of metal arc welding are used:

Manual work can be done in two ways: consumable and non-consumable electrode. In the first case, during operation, electrodes are used that can melt under the influence of electrical energy. This method is most often used in manual work. Thus, an electric arc is ignited, whereupon the electrode is melted and the material edge is subsequently melted. As a result of this effect of electricity, a bath of molten material is formed. After cooling, the bath turns into a seam. In the second case, the following happens with a non-consumable electrode: the edges to be joined come into contact, after which an arc is excited between the electrode (graphite or carbon) and the product; the edges of the product, as well as the filler material, are heated to the melting temperature, as a result of which a bath of molten material (alloy) is formed. After hardening, the material (alloy) forms a weld. A similar method can affect any non-ferrous metal, as well as its alloy.
Automatic and semi-automatic submerged arc welding can be performed by mechanizing the basic movements that a welder performs during manual processing of metals or when exposed to his alloy.
In protective gas, it is produced using a non-consumable (tungsten) electrode, or by using a consumable electrode. The weld is formed in the first case due to the melted edges. Thus, if necessary, filler material is fed into the arc zone. The second case involves the supply of an electrode wire to the arc region, which subsequently melts, thereby taking part in the formation of a seam of parts (it can also affect the alloy). The protection of the seam from the formation of an oxide film on it is achieved not without the participation of a jet of protective gas, which displaces air from the working area.
Electroslag treatment of metals, as well as their alloys, is achieved by melting the edges of the material to be joined, as well as the electrode, by means of heat from an electric current during passage through the slag. In addition, slag helps to protect the material from air, and, accordingly, from subsequent oxidation.

Soldering and everything you need to know about it

Soldering has been used as a way to create a reliable connection between metals and alloys since ancient times. Metal products obtained as a result of processing were worn back in Babylon, Rome, Ancient Egypt, and also Greece. Of course, only a few technological rules of application have come down to our time, but these rules are far from known to everyone today. Thus, soldering methods should be known to anyone who wants to or already knows the basics of soldering.

What is soldering?

Soldering is the procedure for joining materials by introducing solder between the parts to be soldered. The solder, which acts as a binding material, fills the gap between the materials, thereby carrying out the installation of parts, after which, when solidified, it forms a single whole alloy, which is an inseparable connection. The procedure allows you to act on any material and its alloy.

During the procedure, the tinol acts on the metal and its alloy, heating it to the desired temperature, which is higher than the melting point of the base material. So, the solder acquires a liquid consistency, after which the surface of the soldered parts is wetted, thereby allowing it to fill the gaps between the parts to be joined. This is followed by the dissolution of the base material in tinol, mutual diffusion. When solidified, a reliable installation of two parts comes out.

What is the difference between soldering and cooking?

The assembly of parts by soldering is similar in appearance to welding assembly, but the essence of the procedure is fundamentally different from welding. Let's consider the differences in more detail.

Differences:

The base material during operation does not melt to a certain temperature, as it happens in.
The absence of melting of the metal of the base of the parts allows you to connect parts of sufficiently small sizes.
In the first case, the disconnection, as well as the connection of parts (assembly / dismantling) can be carried out without compromising the integrity of the material (the alloy or metal does not suffer).
The procedure can affect different metals, the alloy of each of them, and even non-metals in any combination.
Soldering is inferior to the welding process in terms of the strength of the joints. Thus, the assembly of parts by soldering, subject to significant mechanical stress, is not always preferable.

Connection types

Consider the types of soldering that you need to know, since tinning and soldering, as well as other processes, can be performed differently depending on the type of connection of parts chosen.

Kinds:

Low temperature. Advantages: possibility of processing miniature parts, cost-effectiveness, ease of use.
high temperature. Advantages: assembly of parts subjected to strong mechanical loads is available.
compositional the procedure affects the metal and alloy of the product, which has uneven or non-capillary gaps. Composite solders are used.
Ready solder- the most popular way.
Reaction flux soldering.

The above methods of work are now confidently used in many industries, occupying their own niches. In this regard, it is inappropriate to talk about the preference of one method.

Welding-brazing is a technological process based on the introduction of a low heat content into the base metal, which leads to the melting of only the filler material.

Increasing demands for improved corrosion resistance are leading to the use of pre-coated materials in many industries. Among the various options for protecting steel from corrosion, zinc is of particular importance due to its anti-corrosion properties, on the one hand, and its low price, on the other.

The layer of zinc deposited on the base material is, depending on the production method, from 1 to 20 microns. A large number of galvanized parts are used in the automotive industry, construction industry, ventilation and air conditioning equipment, household appliances, etc.

Due to cathodic protection, zinc is of great importance for protecting steel from corrosion. If there is damage to the protective zinc layer, then the zinc coating affects the iron with cathodic protection. It affects also at a distance of 1 - 2 mm on an uncoated surface. Due to the remote effect of zinc cathodic protection, both non-galvanized cut edges of sheets and microcracks that occur due to cold working, as well as the environment of the weld, in which zinc evaporates, are protected. In the same way, on the basis of cathodic protection, under-film corrosion of the zinc layer of the cut edges is excluded.

What is the essence of welding - soldering galvanized parts?

Zinc begins to melt at ~ 420 ° C and evaporate at ~ 906 ° C. These qualities adversely affect the welding process, since the ignition of the welding arc is accompanied by the evaporation of zinc. Evaporation of zinc and oxides can lead to the formation of pores, cracks, welding defects and an unstable welding arc. Therefore, it is more favorable for galvanized parts if less heat is installed. An alternative for welding - soldering galvanized sheets in a shielding gas environment is the use of a copper-containing filler wire.

Copper-silicon (Cu SI3) and aluminum-bronze wires are especially known. When using these wires, the following advantages can be mentioned:

no welding seam corrosion;
minimal spatter;
low burnout of the coating;
low heat input;
simple subsequent seam processing;
cathodic protection of the base material in the immediate area of the seam.

These filler materials, due to the high content of copper, have a relatively low melting point (depending on the composition of the alloy, from 950 to 1080 ° C). The base material does not melt, which means that the connection corresponds more to soldering. The designation "Welding - soldering, or MIG - soldering" also comes from here. The shielding gas is usually argon.

Filler materials

For welding - soldering galvanized sheets, the following copper alloys are recommended:

CuSi3; CuSi2Mn; CuA18

In practical applications, filler materials of the CuSi3 type are used most frequently. Their significant advantage is their low strength, which facilitates subsequent machining. The flowability of the filler material is largely determined by the silicon content. With increasing silicon content, melting becomes viscous, so you need to pay attention to a tight tolerance in the content of alloying additives in the alloy.

A filler material of the CuSi2Mn type is also used for zinc coatings. The additional content of 1% manganese in the wire increases the rigidity. For this reason, it is more difficult to machine than other copper alloys. This wire is primarily used where post-machining is not required. Welding filler material type SiA18 is used primarily for steel with aluminum coating.

During the process of welding - soldering, a controlled transition of the material into the seam is used, therefore, a pulsed welding arc. In some applications, especially with thick zinc layers from 15 µm, a large amount of vapor can lead to instability in the soldering or welding process. Therefore, it is more convenient in cases of this type to use a short welding arc, which can hold more stable. In this case, high demands are placed on the power supply and its regulation characteristic.

In an argon-rich shielding gas environment, by properly selecting the parameters of the main and pulsed current, a controlled, short-circuit-free transition of the material into the weld is achieved (Fig. 1).

Variable pulse shape during welding - soldering (Iknt is the current strength at which the jet arc is applied, IM is the average current strength).

With the optimal choice of parameters, a drop of filler material is detached from the wire electrode by an impulse. As a result, the process is almost spatter-free. Studies have shown that different filler materials and shielding gases require different pulse shapes. This led to a separate for each filler material "cut off" by mass shape of the pulse. This is especially true for bronze and copper wires.

In order to keep the evaporation of zinc as small as possible in thin sheets, it is necessary to carry out the process at a low current strength. Therefore, the main requirement is that the current source in the lower power region provides a particularly stable arc. The low setting of the main current is just as important as the quick response arc length control so that the arc length can be held for a short time. The result is a slight heating of the base material and a decrease in the amount of zinc evaporation. As a result of both effects, a small number of pores are encountered (Fig. 2).

This has a positive effect both during the subsequent processing of the seam by grinding, and with an increased indicator of the strength of the joint by soldering.

Rice. 2. Fillet weld with pulse welding arc (sheet thickness 1.5mm)

synergy mode

A good MIG soldering result on galvanized sheets can only be achieved with a power source with a sufficiently rich level of freedom in the choice of parameters. Thanks to the many infinitely adjustable parameters (approximately thirty parameters), it is possible to improve droplet separation when welding with a pulsed arc or to use a short circuit when welding with a short arc for a large number of filler materials without any problems. These additional parameters complicate the maintenance of the power supply and would therefore limit the circle of users only to experts.

With the help of the so-called synergic mode (digital control) with programmed parameters for each combination of wire and gas, this process is very easy to operate for the user.

The welding machine manufacturer takes on the task of optimizing the parameters for many different base materials, filler materials and shielding gases. This scientifically substantiated result is recorded in an electronic storage device in the form of a data bank. The user gets the choice of parameters for any filler material directly in the power source. The built-in microprocessor takes care of the stepless choice of power in the range from minimum to maximum.

Wire feed

Compared to standard wires, bronze wires are very soft. Therefore, special requirements are placed on the wire feed mechanism. The filler wire must be fed freely, without friction. The 4-roller drive with the feed rollers involved transmits itself, with a small pressing force, sufficient force to feed the wire. Usually smooth rollers with a semi-circular groove are used. To keep a small amount of frictional resistance in the hosepack, a Teflon or plastic channel must be used. Precise entry of the wire into the contact tip is another basic prerequisite for trouble-free wire feeding.

Precisely sized contact tip in the torch provides reliable contact to transfer current to the bronze wire.

Application examples of welding - soldering

The process of welding - soldering can be used for non-alloyed and low-alloyed, as well as for stainless steels. This method is mainly used for steels with a galvanized surface. Slight burnout of the layer both in the immediate area of the weld and on the reverse side is due to low heat input and low melting temperature of the filler material.

Rice. 3. Application examples of MIG soldering in the automotive industry and related industries: fuel line element, door hinge

For welding - soldering, all types of welds and welding positions that are known for welding in shielding gas are suitable. Both vertical seams (from bottom to top and top to bottom) and ceiling positions are executed flawlessly. The welding speed for MIG soldering is identical to MAG welding (up to 100 cm/min).

Appeared long before the invention of electric welding. It was used in ancient Rome and Babylon, as evidenced by archaeological excavations.

During this time, technologies have improved, and new types of soldering have appeared, in which electric current, a gas burner flame, laser energy or other sources of thermal energy are used to heat the metal.

Capillary type of soldering is the most common. Many, using it, are not even aware of such a name. The essence of the technology is as follows.

The solder is melted, it heats up and fills the space between the two prepared parts. The wetting of the surface of parts and the retention of solder is largely due to the effect of capillarity.

The capillary type of soldering is common in everyday life and in various industries. To carry it out, you will need a soldering iron or a burner. In fact, any type of soldering can be considered capillary to a certain extent, since each type has capillary wetting of workpiece surfaces with liquid solder.

diffusion

This type of soldering differs from the rest in the duration of the process, since diffusion takes time.

The solder inside the weld zone is kept at a certain temperature longer than, say, with conventional capillary soldering. The connection of two workpieces occurs due to the diffusion of solder and soldered metals.

The diffusion process itself consists in the penetration of molecules of one substance into the structure of another substance. Soldering occurs at the molecular level and makes it possible to obtain a stronger seam.

Diffusion type requires strict adherence to temperature and time conditions. The heating temperature in the soldering zone is always higher than the melting temperature of the solder.

Contact-reaction

The type of soldering called "contact-reaction" or "reactive" means the process of fusion when two parts from different metals come into contact.

There is a phase transition of the metal from a solid to a liquid state, followed by hardening and fusion. Often such a connection is carried out through a thin layer, which is applied to one of the blanks by galvanic or other means.

Eutectic materials are used. So you can combine silver and copper, where a copper-silver alloy will be formed between the parts. Conduct soldering of tin and bismuth, silver and beryllium, graphite and steel.

It is possible to solder aluminum with other materials through a layer of copper or silicon. The connection is strong, the soldering time takes a fraction of a second.

Reaction-flux

Reactive flux soldering is based on a chemical reaction in which solder is formed from a flux when combined with a metal. This is clearly seen when aluminum parts are connected to each other.

For their docking, a flux based on zinc chloride is used. When heated, zinc begins to interact with aluminum, turning into a metal solder.

It fills the entire gap space, making the place of the soldering zone a strong connection. In this case, it is very important to accurately observe the proportions of the applied flux. There must be a lot of it so that pure zinc in the required amount can stand out from the flux powder.

Sometimes with this type of soldering, you have to add in small quantities, as an addition to the main process. This is usually done if two workpieces are overlapped.

Soldering-welding

The technology got this name because the process itself is very much like welding metal with filler material (wire or powder).

But in this case, solder is used instead of an additive. This type is most often used to repair defects and flaws on the surfaces of metal parts (cast).

The process itself can be carried out in different ways:

soldering in furnaces;
dipping in;
resistance with electric current;
induction method;
radiation;
using soldering irons and gas burners.

Some species appeared relatively recently, are still being researched and refined.

In furnaces

The first option provides uniform distribution of the solder over the defective parts of the part and uniform heating, which is especially important when you have to solder large-sized workpieces with a complex configuration.

At the same time, heating in the furnace can take place by one of the many existing methods, ranging from flame heating to complex technological processes, such as induction, electrical resistance.

The design of the furnaces themselves differs from each other only in the hearths on which the soldered workpieces are laid. For large parts, furnaces are used in which the hearth does not move, and for small parts, they are movable in the form of conveyors on rollers.

The main task of this type of soldering is to create a special gaseous substance inside the furnace. Soldering in ovens can be completely mechanized, which leads to increased productivity. And for industries with a mass output of finished products, this is an ideal option.

Application of induction and resistance

As for the induction type, high frequency currents are used for it. Electricity is passed through the soldered parts, which is why they heat up.

Two soldering methods are implemented here: stationary and with the movement of a part or an inductor. In the case of joining large-sized workpieces, the second technology is used.

The resistance soldering method is somewhat similar to the induction type. It's just that in this technology, the current is passed through both the workpieces and the soldering element. That is, the connected parts become part of the electrical circuit.

Such a process is carried out in electrolytes or in special contact machines, the operation of which is very similar to standard electric welding. Contact machines are usually used in industries where it is necessary to solder together thin sheet metal products.

Soldering in electrolytes is not often used today due to the complexity of setting the parameters of the technological process. After all, the process takes place according to the principle of the thermal effect that occurs between the cathode (soldered parts) and the anode.

A hydrogen shell is formed around the blanks, which has a very high electrical resistance. Hence the release of large thermal energy.

bath immersion

Soldering with immersion is carried out either in a medium of molten solder or in a mass of special salts. The last type of soldering is a fast operation due to the direct heating of the workpieces from salts, which act as both a heating element and a flux. With regard to immersion in solder, the possibility of full or partial immersion should be noted.

radiation method

The radiation type of soldering is produced due to a powerful light flux, which is formed by a quartz lamp, a laser or a defocused cathode beam.

The technology appeared relatively recently, but showed that in this way it is possible to achieve high quality soldering of two metal blanks. In addition, there was a real opportunity to control the process both in terms of the degree of heating and in terms of time. At the same time, the laser removes the oxide film from the solder and from the metal, which guarantees a high quality solder joint.

The gas shell in the connection zone, formed by heating the metals, makes it possible not to use fluxes when connecting. Therefore, when people talk about flux-free soldering today, they mean laser technology.

Torch and soldering iron

As for soldering with torches, two technologies are most often used, which, in fact, are no different from one another. There is simply a heating of the two parts and the solder placed between them in the gap.

In the first method - due to the combustion of gas, in the second - due to the formation of plasma (this is a combustible gas that moves in a thin jet at high speed). It should be noted that the method with gas burners is considered universal.

Torches that emit a plasma stream operate at high temperatures. And this allows you to solder together parts made of titanium, molybdenum, tungsten and other refractory materials.

The complexity of this technology lies in the fact that it is almost impossible to adjust the electric arc to a certain heating temperature (to a certain accuracy).

Soldering with a soldering iron has been used for a long time. If 5-10 years ago it was possible to talk only about electrical appliances or those heated by fire, today there are much more proposals.

I would like to note soldering irons powered by ultrasound. That is, ultrasound itself is related to the soldering process only from the standpoint of the destruction of the oxide film.

Therefore, it became possible to solder various metals in an air environment without flux materials. Direct soldering comes from heating the solder.

Vacuum

Vacuum soldering is still not always and everywhere used today. The complexity of this type lies in the fact that it is necessary to create a rarefied atmosphere without air in the soldering zone.

As you know, the oxygen present in the air is the cause of the formation of an oxide film, which covers metal workpieces and solder.

The film is very refractory; when soldering, temperature degrees are lost to heat the parts to be joined. Therefore, all scientists are still looking for ways to remove the oxide coating or carry out the process without it. Vacuum soldering is one such option.

The following factors prevent the introduction of a vacuum type into production:

low productivity of the process, because each individual part has to be heated;
in this way, only workpieces of small sizes can be soldered;
the complexity of creating machines and additional equipment;
the complexity of the soldering process.

However, if we talk about space, where there is no atmosphere, then the vacuum view is considered very promising.

Selective

It cannot be said that the selective type of soldering is fundamentally different from the capillary one. In the same way, solder and heat are used in it. But the solder is melted only in selective places (local points) on which it is planned to attach the elements.

Selective soldering is used mainly for the manufacture of boards and pins of pin components. It is similar to the wave method used for soldering smd chips.

The selective soldering unit is equipment belonging to the category of semi-automatic devices. It is not cheap, but it saves consumables by almost ten times compared to the wave, so it spreads wider and wider.

Temperature regime and materials

The classification of soldering processes is based on the methods of operation, the conditions under which the joints are obtained, and on the types of consumables. The concepts and types of soldering are described in detail by GOST 17325.

Soldering is called high-temperature or hard soldering if the solder is heated to a temperature of 450 ℃ and above. Otherwise, you have to deal with a low-temperature type (soft).

For low-temperature type, low-melting solders are used. These include alloys of tin and lead, bismuth, gallium, and indium. To refractory belong copper-silver, copper-zinc solders.

Due to the dictates of new materials and environmental safety requirements, soldering technologies are constantly changing. Lead solders are being used less and less, smoke detectors are being installed, and laser and ultrasonic equipment are being developed.

A significant role in the development of soldering is played by the introduction of robotic systems, which can significantly speed up work.

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