Solid soldering. How to solder stainless steel and brazing technology

There are several methods of hard soldering. These methods can be classified (FIG. 212) according to the method of heating the metal during the soldering process. Hard solders are sometimes divided into refractory solders with a melting point of 875-1100 ° and fusible solders with a melting point below 875 °. A separate group is made up of aluminum solders. Ordinary hard solders

are divided into copper, copper-zinc, copper-nickel and silver. The most important hard solders are standardized.

Fig. 212. Methods of soldering with hard solders.

The composition and approximate purpose of copper-plated solders according to GOST 1534-42 are given in Table. 24. The composition and approximate purpose of silver solders according to OST 2982 are given in Table. 25.

In addition to these standard solders, solders are of known interest and can find industrial use, as indicated in Table. 26. In a number of cases commercially pure copper with a melting point of 1083° is used as solder.

Standard copper-zinc solders (composition in percent) Table 24

The basis of most fluxes for hard soldering is Na2B407 borax, which crystallizes with 10 parts of water to form large transparent colorless crystals of Na2B407 10H2O. Crystalline ten-water borax begins to melt at 75°, as the heating intensifies, it gradually loses water, strongly swelling and splashing, and passes into anhydrous salt - fused or burnt borax, melting at 783°. Borax in the molten state can be heated to high temperatures without noticeable evaporation, is very fluid, and vigorously dissolves oxides of many metals, especially copper oxides.

To enhance the action of the flux, boric acid B (OH) 3 is often added to the drill, due to which the flux becomes thicker and more viscous, requiring an increase in operating temperature. For pony
To increase the working temperature of the flux, which is especially important for low-melting solders, zinc chloride ZnCb, potassium fluoride K. F and other alkali metal halide salts are introduced.

Table 25

Standard silver pripon (composition in percent)

						Tempera - j round melt - i leya in °С	Approximate appointment
							soldering brass,
							less than 58% copper
							Soldering copper, armor
							PS, brass, steel
							Soldering copper and
							Ribbon soldering
							Soldering wires

For soldering stainless steel, a mixture of equal parts of borax and boric acid is used, kneaded to a paste density in a saturated aqueous solution of zinc chloride.

For brazing gray ductile iron, strong oxidizers such as potassium chlorate, manganese peroxide, iron oxide, etc. are often added to the fluxes to burn out the graphite and increase the clean metal surface wetted by the solder.

Table 26

B. Silver Melting point in °C Approximate appointment Universal, for soldering copper and copper alloys, steel, nickel Eutectic with high electrical conductivity, wire soldering Low-melting, self-fluxing - Xia, for copper and copper alloys, not suitable for ferrous metals Particularly fusible, universal, for copper and copper alloys, steel, nickel

Fluxes can be in powder or paste form. Fluxes are also used in the form of liquid solutions, for example, a solution of borax in hot water. Sometimes it is advisable to use solder rods coated with flux from the surface. The fluxing effect can be produced by the components of the solder itself. For example, phosphorus, oxidized to phosphoric anhydride, is a good flux for copper and copper alloys, reducing oxides and converting them into low-melting phosphoric acid compounds. Therefore, phosphorous copper solders do not require fluxes for soldering copper alloys, which is very convenient in practice.

Powdered fluxes can be sprinkled thinly on the edges, and the edges are often preheated so that the flux particles melt, adhere to the metal, and are not blown away by the flame of the torch during soldering. Powdered flux can also be dipped in the end of the solder rod, heated above the melting point of the flux, which adheres firmly to the rod.

Pastes and grouts are applied with a brush or solder is dipped into them. It is possible to make a flux paste with powdered solder and apply it to the edge before soldering.

For soldering, preparatory work is important, often determining the quality of the connection. Three main forms of solder joints are widely used: lap, butt, and mustache joints (Fig. 213). The most common is the lap joint, which is convenient to perform and very. durable. By increasing the overlap of the lap joint, it is possible to increase its strength and, in most cases, to achieve an equal
strength with base metal. The butt joint has a better appearance and, with good solders and proper execution, can often provide sufficient strength (tensile strength can reach up to 40-45 kg! mm1). A butt joint is used in cases where doubling the thickness of the metal is undesirable. Whisk joint, which requires complicated edge preparation, combines the advantages of butt and lap joints and provides a good appearance and no protruding edges and doubling of thickness. The connection in the mustache makes it possible to achieve equal strength with the whole section by increasing the working area of ​​​​the connection.

Of essential importance is the gap between the joined edges, which should be small both to improve the absorption of liquid solder by the action of capillary forces, and to increase the strength of the joint. For silver solders, a gap of 0.05-

0.08 mm, for soldering with copper in shielding gas, gaps of no more than 0.012 mm are recommended. Strict requirements for the size of the gap prescribe a fairly clean machining of surfaces, since rough processing, such as filing with a file or sandblasting, can cause excessive consumption of solder in the joint and a sharp drop in its strength.

To obtain good solder wetting, the surface to be soldered must be immaculately clean.

Degreasing can be done with hot alkali, trichlorethylene or carbon tetrachloride. Oxides are removed by etching in acids, followed by thorough washing and drying.

Mechanical cleaning is done by rubbing with ends, fine emery cloth, grinding with fine numbers of grinding wheels, brushes, etc. During assembly, pre-application of flux on the edges is often used with solder placed between the edges; in this case, solder is used in the form of foil or fine powder, or solder in the form of a wire or tape placed near the soldering point.

Assembled parts before soldering must be sufficiently firmly fastened with clamps, wire ties, studs, spot welding, etc. in order to eliminate the possibility of displacement of parts during heating and during the soldering process. The surface of products that should not be tinned is covered before soldering with a paste of chalk, clay, graphite or mixtures thereof, or wetted with a solution of chromic acid, etc. with substances that eliminate the adhesion of solder to the surface of the product.

In accordance with the above classification, here is a brief description of the main methods for performing the brazing process.

Gas soldering. With this method, the soldering point is heated by gas burners. For soldering small parts, burners operating in air with natural (methane) or other combustible gas or acetylene are used. For large parts, burners operating on oxygen with methane or other combustible gases, especially acetylene, are used. Oxy-acetylene torches are used as a special type for soldering, giving a wide flame, as well as normal, welding. Special torches for soldering give less concentrated heating and immediately cover a large surface with a flame; the flame is maintained with a slight excess of acetylene.

Soldering by immersion. With this method, soldering is performed by immersing the product in a bath of molten solder or in a bath of molten salts. For metal baths, copper-zinc solders are usually used. The molten solder in the bath is covered with a layer of flux. The surface of the product, which should remain clean from solder, is lubricated with pastes and solutions that prevent its wetting.

Salt baths for hard soldering are arranged like salt baths for heat treatment of steel. Bathtubs with electric heating are especially convenient. The salt mixture is usually composed of potassium and barium chlorides KC1 + BaC12. The composition of the bath for any temperature range can be selected by changing the ratio of the components of the salt mixture.

Parts are assembled by applying flux to the surface to be soldered and placing solder between the edges or near the joint, then bonded and dipped in a bath. The salt bath provides a constant temperature regime with an accuracy of ± 5 ° and protects the soldering place from oxidation. When the part is removed from the bath, it is protected from oxidation during cooling by a film of molten salts, which, upon cooling, can be removed by washing in hot water. The use of salt baths for hard soldering deserves great attention. It is highly probable that this method will be widely adopted in our industry in the coming years.

Soldering by immersion in baths is characterized by high productivity, uniform soldering quality and can be mechanized.

Electrical soldering. Electric heating of the soldering place can be carried out by various methods: an electric arc of direct or indirect action, passing current through the welding place, eddy currents that are induced in the metal of the product by alternating magnetic fields, due to heating of the contact between the surface of the product and the current-carrying electrode, etc.

For soldering with a direct arc, copper-zinc solders are not very suitable, due to the volatility of zinc and its strong evaporation and burnout under the action of a high arc temperature. The most suitable refractory copper solders containing phosphorus or silicon. For soldering, a carbon arc is used, which is directed mainly to the end of the solder rod touching the base metal, and should not melt the edges of the product.

An indirect carbon arc (arc burner) replaces a gas burner and makes it possible to perform the soldering process with all types of hard solders, both copper-zinc and silver. Technologically, an arc torch is less convenient than a gas torch, and is usually used only for a small amount of soldering work.

Electrical resistance soldering can be carried out on normal contact welding machines or on special electrical soldering machines. The soldering point is heated by passing a high current through it. The current is obtained from a low-voltage transformer built into the body of the soldering apparatus and constituting one with it.

More versatile electrical devices for soldering are devices that work by the method of hot contact between a carbon or graphite electrode and the product. Such a device consists of two main parts: a step-down transformer, movable or fixed, and soldering pliers connected to the transformer terminals by flexible wires, which can be of considerable length, which gives the installation flexibility and versatility of use.

The step-down transformer is made according to the type of transformers for electrical contact machines. The primary winding of the transformer is made sectioned, which makes it possible to regulate the voltage of the secondary winding and the working current by switching the turns of the primary winding, as is done in contact machines. The primary winding of the transformer is connected to the electrical circuit by a push-button contactor. The power button is placed on the handle of the soldering tongs (Fig. 214) or taken out in the form of a separate portable pedal. The working current-carrying contacts of the soldering tongs are made in the form of interchangeable prismatic blocks - bars of electrode carbon or graphite. The part is clamped with a clamping screw, the heating current is switched on with a button on the handle of the tongs. Working currents for soldering are usually in the range of 500-1000 A.

Soldering tongs are connected to the secondary winding of the transformer with flexible wires of sufficient cross section and the required length (usually up to 2-3 m). For soldering copper, phosphorous copper solders are usually used, and for soldering steel, silver
solders. Phosphor-copper solders are unsuitable for soldering ferrous metals.

Soldering with high frequency currents. Recently, a new, very effective method of soldering with high-frequency currents has been rapidly developing and is beginning to find wide industrial application. The method is based on heating the metal at the place of soldering with eddy currents, which are created by a high-frequency alternating magnetic field. An alternating magnetic field, in turn, is created by magnetizing windings - inductors. When the inductor approaches the surface of the product, eddy currents arise in the metal zone subjected to the magnetic effect of the inductor. The action of the inductor is the stronger, the smaller the distance between the inductor and the heated metal. To possibly reduce the distance, inductors with refractory enamel insulation are used; in this case, the distance between the inductor and the heated metal can be reduced to 0.3-0.5 mm.

Heating by high frequency currents is concentrated in a very thin surface layer of the metal, in which eddy currents occur. The underlying layers heat up due to heat conduction. The small volume of the heated metal allows heating very quickly with high efficiency.

The soldering process is clean, easy to perform, easy to mechanize and can be well adapted to the conditions of mass production of the same type of parts. All these advantages provide high-frequency heating with the possibility of wide industrial use in soldering. An obstacle to the use of high-frequency currents is still the rather high cost and some complexity of installations for obtaining these currents. As installations become simpler and cheaper, they will be widely used for the soldering process.

Soldering in ovens. Heating for soldering can also be carried out in various furnaces similar in design to steel heat treatment furnaces. For example, spectacle furnaces with oil heating are used, muffle furnaces are widely used, and electric muffle furnaces are especially convenient. Soldering is carried out by heating parts with pre-applied flux and solder, which is laid between the edges to be joined or

placed next to the soldering point. Soldering in furnaces using flux is laborious, requires a fairly skilled workforce and does not have prospects for a particularly wide industrial application. Much more important is soldering in furnaces in a reducing atmosphere; this type of soldering has prospects for widespread use in mass production.

Copper is one of those materials that are better soldered than welded, especially when it comes to pipes with thin walls, which are actively used in heating, plumbing and gas systems in utilities and other areas. In order for the process to go well, you should choose the right solder for soldering copper pipes. This metal lends itself well to soldering, so even a person without much experience can cope with this process. This mainly applies when working with pure metal, and not so on. During this process, the structure of the pipe metal does not change, and the solder itself has good enough characteristics to withstand the upcoming loads.

hard solder

The need for soldering arises both during the installation of equipment and during its repair, since often thin-walled pipes can be damaged. Copper solder, like copper itself, must have high anti-corrosion properties. Also, it should not be overgrown with various deposits of biological origin. With all this, it must be suitable for high-quality soldering, so as not to spoil the structure of the metal and it was possible to last several decades after use.

Solder for soldering copper pipes is excellent for both copper itself and its alloys with zinc, lead, tin, antimony, phosphorus, iron, manganese or nickel. Although there are oxides in metal alloys, they are easily removed with a flux, so copper solder does not encounter problems in its path. Other metals can form oxides that are difficult to dissolve with fluxes, therefore, problems can already arise with them. When soldering copper pipes, an overlap type of connection is used. This allows the structure to achieve maximum strength, which increases its service life. In order for the joint to have sufficient strength, the overlap must be at least 5 mm. Unlike those cases when it happens, here you can make a seam of any thickness and this will not affect the quality of the connection in any way. When soldering, a small gap is left so that the solder for soldering copper pipes is evenly drawn into the hole and fills all the gaps to create an airtight patch. Modern versions of this consumable are manufactured in accordance with GOST 52955-2008.

Copper pipe soldering process

Varieties

1S refers to soft solders. It has silver in it. It is suitable not only for copper pipes, but also for bronze products, brass, which are used for both hot and cold water supply. There is no flux in its composition, so you have to use it additionally or use a paste.

Rosol 3 is a soft solder that requires the addition of a flux in order to work. Its melting point is relatively low at 240 degrees Celsius, which helps to work seamlessly with thin products. It is suitable for copper, brass, bronze pipes and fittings. After application, it performs equally well at both high and low temperatures.

Solder Rosol 3 for soldering copper

Rolot 94 is a hard solder. It is a high quality material for working with copper, brass and red bronze. It is best used for slot and capillary soldering of pipes that are installed without fittings. This solder for soldering copper pipes has a high enough working temperature, which reaches 730 degrees Celsius, so it should not be used with thin-walled materials. Its distinctive feature is a large melting range.

Copper solder rolot 94

Rolot 2 is a special hard solder, as it is not standardized. It contains a low level of silver content. It is suitable for standard soldering procedures and provides good installation procedures.

Solder Rolot 2 for soldering copper pipes

Solders for soldering food copper can be attributed to a special category, since they should not contain any harmful substances that could harm health. Among them are the following options:

• Tin-Copper is a low-temperature material that melts quickly while forming a high-quality, corrosion-resistant bond. Composition - (S-SN97Cu3).

• Copper, with the addition of zinc and silver, while the main material here is silver, as it makes up as much as 44%, while copper is only 30%, and zinc is 26%. It is a high-temperature solder for soldering copper pipes, which gives a ductile, but at the same time strong connection that is not susceptible to corrosion and has a high thermal conductivity.

• Silver-tin is a low-temperature material that melts quickly, while forming a high-quality compound that is resistant to corrosion. Composition - (S-Sn97Ag5).

• Copper Phosphate is a high temperature material that can be used without additional flux. It gives a strong seam, the elasticity of which is directly dependent on temperature. In the composition, copper occupies 94%, and phosphorus - 6%

• Solder for soldering copper with silver is a high-temperature solder. The seam is strong and plastic at the same time. Additional flux should be used. The big disadvantage is the high cost.

Physicochemical characteristics

The physical properties of the material are determined by its composition and should correspond as much as possible to the metal with which they will be soldered, but at the same time, the solder for soldering copper tubes must have a lower temperature than the base metal so as not to damage it and not change the structure, which is especially dangerous with thin wall tubes. Based on all this, we can distinguish two main physical properties by which these materials are divided:

• Low-temperature, which have a relatively low melting point, which does not exceed 450 degrees Celsius. As a rule, this affects the strength of the seam, since the soldering is not designed for high loads. The physical properties of the metal do not change, including strength.

• High temperature solders for copper. The strength of the connection with this variety increases, but under the influence of temperature, the strength of the material itself may decrease, since in some cases the temperature reaches 800 degrees and above, which creates the effect of annealing on the metal.

Specifications

• Melting point: 630 - 730 degrees Celsius
• What metals can work with: copper, brass, red bronze, cast iron, copper and its alloys, steel of various grades, nickel and its various alloys
• Which flux is suitable: LP 5.

• Melting point: 650 - 800 degrees Celsius
• Operating temperature: 710 degrees Celsius
• What metals it can work with: copper, brass, red bronze, cast iron, copper and its alloys, steel of various grades, nickel and its various alloys.
• Which flux is suitable: LP 5.

Features of choice

A large dependence here is observed on the melting temperature, since the higher it is, the more influenced the pipe metal is. If this is not essential, as in thick pipes, which do not bear much responsibility, then it is better to choose brazing copper with a high melting point. Otherwise, if the walls are thin and do not need high joint strength, then soft solder for soldering copper pipes with a low melting point is suitable. Particular attention should be paid to edible copper, since the solder in this case should not contain toxic and poisonous components.

To choose which solder to solder copper pipes, you need to know the composition and melting point of the material on which it will be soldered.

Soldering Features

The bonding process is not much different from other metals. Here you also need to prepare the surface by cleaning it from the oxidation film. A flux should then be applied to improve the soldering properties, if required by the technology. Leave a gap of 0.5 mm between the parts. Then it is already possible to heat up the metal for the working temperature, as soon as it is reached, it is required to connect the solder to the workpiece so that the molten metal penetrates into all the required holes. Then let it cool naturally.

Popular brands:

• POS-10;
• POS-25;
• POS-45;
• POS-70;
• PMC-36;
• PMC-45;
• PMC-54;
• PSr-15;
• PSr-45.

Purpose

The instruction is a guide for soldering steels: structural, corrosion-resistant () and heat-resistant high-temperature solid silver solders PSr40; PSr MIN63; PSr21.5; and copper solders VPR1; VPR4 and their imported counterparts in gas burners, as well as in chamber furnaces and furnaces with a vacuum environment.

Equipment and materials

2.1 Gas burner GOST 1077-79
2.2 Chamber electric furnace with temperature up to 1300 degrees
2.3 Vacuum furnace type START
2.4 Necessary devices for mounting and fixing parts
2.5 Acetone GOST 2603-79
2.6 pure class "A" GOST 10157-79
2.7 Tweezers

SOLDERS AND FLUXERS

3.1 For soldering, use the solders indicated in Table.

brand solder	Soldering temperature o C
PSr40 GOST 19738-74	650-670
PSrMIN63	800-820
PSr21.5	1080
VLOOKUP1	1130
VLOOKUP4	1050

3.2 Heat treatment of the solder is carried out, if appropriate, if the solder is not sufficiently ductile.
3.3 For soldering, use the listed types of fluxes:
PV200 for soldering with solders PSr21.5 and VPR1;
PV201 for PSr40 and PSrMIN63;
Potassium tetrafluoroborate (КВF2) GOST 9532-75 for soldering PSr21.5 and VPR1 in a neutral environment.

4 SURFACE PREPARATION OF PARTS AND SOLDER

4.1 The size of the gaps should be, as a rule, from 0.7 to 0.15 mm for "telescope" type connections and up to 0.2 mm for other connections (lap, butt, tee) It is allowed to reduce the gap in the "telescope" type connection if this is due to the design features of the node.
4.2 Surfaces to be soldered must be finished to a roughness of at least 2.5.
4.3 On case-hardened products, after removing the copper coating, the solder surfaces should be mechanically cleaned to bare metal.
4.4 The presence of a chamfer at the place where the fillet is formed during soldering must be excluded. The edges of the groove in which the brazed part is placed must be blunted with a radius of ±0.1 mm.
4.5 Presence and corrosion on the soldered surfaces of the nodes after mech. processing is not allowed
4.6 Parts to be soldered must be washed.
4.7 Immediately before soldering, degrease the parts included in the assembly and solder in acetone or another solvent and dry in air for 10-15 minutes. Assembly after this procedure is carried out with tweezers or use cotton gloves.

5 PREPARATION OF EQUIPMENT AND RIGGING

5.1 When soldering in a chamber furnace in argon, the inner surface of the container must be cleaned of dirt and cleaned by washing with acetone or other solvent.
5.2 Vacuum furnace before loading units for soldering must be cleaned of dirt and oil according to the instruction manual.
5.3 The tooling must be washed in acetone or other solvent before soldering. If there are loose oxide films, it is allowed to blow the tooling with electrocorundum or hydrohoning.
5.4 When soldering in a neutral environment, before starting argon into the furnace, purge the pipeline system with argon. Change of cylinders during the soldering process is prohibited.

6 ASSEMBLY

6.1 Assemble the nodes to produce in fixtures that ensure the required position of parts and eliminate stress in the soldering area.
6.2 Solder fixation should be carried out on contact welding machines using a welding gun or welding tongs.

7 SOLDERING

a) Soldering with a gas burner
7.1 Dilute the flux in H2O or alcohol to a paste, then coat the surfaces to be joined.
7.2 Cover the solder with flux diluted in H2O or alcohol and sprinkle with flux powder
During the heating process, it is necessary to ensure that the metal surface at the gap is not exposed to flux and, if necessary, add flux powder.
7.3 Heat the area to be soldered to the temperature indicated in the table above. The temperature during soldering is controlled visually by the beginning of solder melting.
Heating of the connection zone should be carried out evenly along the entire length of the connection, avoiding overheating. When soldering parts with different wall thicknesses, heat the heavier parts first.
7.4 Avoid contact of the flux with the flame for more than 4-5 minutes due to the possibility of loss of flux properties. The optimal flux heating time when soldering in a gas flame is 20-60 seconds.

7.5 During the soldering process, the unit must not be subjected to mechanical stress until it has completely cooled down.

7.6 If necessary, to protect the inner surface of the pipes from excessive oxidation, apply flux to the inner surface of the pipe or let argon inside.

When soldering, place the pipe in the connection area, if possible, vertically. The armature must be at the bottom.

7.7 Work-hardened parts made of steel type 12Kh18N9T should be annealed before soldering (pipe parts after bending)

7.8 Bending pipelines after soldering is not recommended and absolutely not allowed at a distance of less than 20 mm from the soldering point. The influx of solder on the nipple is allowed to be filed.

b) Soldering in a chamber furnace

7.9 Produce in airtight containers with a steel cap screen in an argon atmosphere.

7.10 Fluxes 200, 201, 209 are diluted in water to a paste-like state and applied in a thin layer, then dried for 10-15 minutes. Potassium tetrafluoroborate powder is poured into a container. The amount of flux, temperature, exposure time, argon consumption, heating and cooling rates are specified in the technology.

7.12 Temperature control is carried out with a thermocouple inserted inside the container.

The hot junction of the thermocouple should be placed as close as possible to the surface of the workpiece to be soldered.

7.13 Cool parts under argon flow to room temperature. It is allowed to blow the container with compressed air in order to reduce the cooling time.

c) Vacuum soldering

7.14 Produce predominantly in an argon environment.

7.15 Place the assembled unit in the device on the furnace tray, closing it with a cap-screen made of steel type 12X18H10T.

7.16 Soldering in an argon environment is performed according to the following scheme:

• Purge the piping system up to the vacuum cock with argon
• Pump out air from the furnace to the residual pressure specified in the technology. It is allowed to flush the chamber with argon, which consists in the following: pumping out up to 10-3 mm Hg. Art., filling with gas and again pumping out to the required vacuum.
• Feed argon gas into the furnace chamber. Feed continuously for 8-10 minutes.
• Turn on the heat and solder.

7.18 Temperature control is performed using a thermocouple recorded on a recorder. The hot junction of the thermocouple should be placed as close as possible to the surface of the solder assembly. It is allowed to measure the temperature in the chamber, provided that the experimentally determined temperature difference on the surface of the product and in the chamber is taken into account.

8 REMOVING FLUX RESIDUES

In hot, then in cold running water, followed by hydrohoning blowing.

9 SEAM CONTROL

9.1 Control of the condition of the nodes should be carried out at all stages of the technical process of surface preparation, assembly and soldering, the introduction of flux and solder, and the elimination of flux residues after soldering.

9.2 The materials used must be GOST or have specifications. Check the expiration date of the flux.

a) external examination;

b) radiographic analysis;

c) checking the nodes for strength and tightness;

d) metallography;

9.4 Subject 100% of the nodes to an external examination using a magnifying glass 4-7 times magnification.

It is necessary to inspect the brazed seam and the area adjacent to it of the base metal at a distance of at least 10 mm.

9.5 The seam must be clean, without porosity, cavities, fistulas, non-solders, foreign inclusions, flux residues, etc. provided that the solder filled the gap and formed a fillet.

10 TROUBLESHOOTING

10.1 Inadmissible non-solders, pores, cavities and other defects should be eliminated by soldering not more than 2 times with the same solder used for soldering or with a lower melting temperature.

As with soldering with soft solders, before soldering with hard solders, the soldering points are cleaned of dirt and fatty substances, the parts to be soldered are tightly adjusted to each other. The soldered seams are cleaned mechanically and chemically.

The assembled and fitted parts at the soldering points are coated with the appropriate flux, depending on the metal being soldered and the solder.

Solder mixed with borax is applied to the seam, and the product is heated to the melting temperature of the solder in various ways: with a blowtorch, on a furnace, in a furnace. The seam must be soldered evenly along the entire length.

When soldering with silver or brass solders, the latter are applied to the heated place of the seam or injected into the preheated seam. If the solder does not disperse along the seam, flux is again poured onto it.

After soldering, the flux remaining on the seams is removed by short boiling for 10-15 minutes in a solution containing 10% caustic soda, 5% machine oil and 85% water.

The soldered and boiled product is thoroughly washed in water, wiped with a dry cloth and dried.

If necessary, the soldered product is tested for tightness.

An example of brazing a tee joint. A tee connection (Fig. 228, b) consists of a coupling, a branch pipe and three outlet pipes. Soldering is carried out with copper-zinc solder PMTs-54.

In preparation for soldering, the parts to be joined (coupling, branch pipe and outlet pipes) are cleaned at the soldering points, degreased, assembled into a knot and tied with steel wire. In mass or serial production, special devices are used to connect parts during soldering.

When soldering this compound, borax is used as a flux, which is heated and dried over low heat before soldering, since raw borax during soldering, swelling with bubbles, bursts and splashes along with the solder. Dry borax is mixed with solder and stored in a box. A mixture of borax and water, used to coat the seams during soldering, will be placed in the second box.

The tee connection is soldered first on one side, then on the other. First, the left end of the coupling is soldered with a drain tube inserted into it (Fig. 228, c), while the connection is held obliquely by the right end (Fig. 228, d). Then they proceed to soldering a tee coupling with nozzles (Fig. 228.5), then solder the right end of the connection, holding the product by the left end in an inclined position (Fig. 228, e).

After that, the soldered joint is turned over and the final soldering of the seams is carried out on the other side.

Soldering a tee joint is a rather complicated process, as it involves heating the joint to a high temperature, at which it is easy to burn it. To avoid this, heating is carried out evenly throughout the soldering point, for which the connection is moved relative to the flame, or vice versa.

When the borax begins to melt and becomes liquid, the solder will begin to melt along with it, the spreading of which must be monitored. If the solder collects on one side, then that side is hotter. In this case, the other side is heated so that the solder goes along the seam.

If heating does not give a positive result, add more solder with borax.

When the solder fills the solder joint, remove the flame from the tee joint. Having finished soldering, the product is allowed to cool down gradually, after which the quality of soldering is checked and any defects are eliminated.

The connection of copper is a complex technological process that allows you to perform a permanent connection.

The development of suburban housing construction has led to the fact that in engineering networks everyone uses pipes made of non-ferrous metals and their alloys. In order for the pipeline system to work smoothly, and most importantly safely, it is necessary to ensure a high-quality connection between the elements of pipeline fittings. Such connections are made using soldering.

Which solder to choose

Copper pipes can be soldered using two types - soft or hard. The temperature of the first melt is 425°C, the working temperature of the second is from 460 to 560°C. A gas burner is used for soldering.

The type of alloy is used based on the ratio of copper and other substances that are part of it. If silver is included in the composition of the soldering agent, then such an alloy is called silver. By the way, the more it is, the lower its melting point. In addition, the presence of a large volume of this metal provides high wettability and flow around the place of soldering.

Another type of copper material work mix that is widely used for copper brazing is copper-phosphorus. But, its melting point is much higher, and such a parameter as wettability is also inferior to silver mixtures.

They are used in the production of refrigeration equipment, which is also used in the food industry.

When soldering copper with copper-phosphorus solder, and its analogues, the use of flux is not required. For soldering copper parts with brass flux is needed. When they are used, a capillary gap is formed with a size of 0.025 to 0.15 mm. A similar gap when using such solders is from 0 to 0.15 mm

copper phosphorus

The connection of parts made of copper can be made with copper-phosphorus solder in the composition, which includes silver. Its share can reach 15%. This alloy is used to work with refrigeration equipment.

The operating temperature of copper-phosphorus solders is not very high. Substances of this class have sufficient fluidity. By the way, when working with this solder, there is no need to use any fluxes. This is due to the fact that it contains phosphorus. It is phosphorus that protects the joint processing zone from the effects of the atmosphere.

The seams formed in the course of work are durable. This is what determined its use for working with refrigeration equipment containing copper parts. The thing is that during his work there is always vibration, in such conditions the strength of the seam will not be superfluous.

When connecting copper components of pipe fittings, it is necessary to cool the elements of the assembly, which have poor resistance to overheating. During operation, the working area can be blown with dry nitrogen. This requires the use of special equipment. Dry nitrogen protection helps to protect the weld from scale.

Solders of this type are unacceptable for working with steel. The point is the presence of phosphorus, which contributes to the formation of a film.

The three-component composition, which includes 2% silver, is brand 102. The scope of this solder is installation, maintenance of refrigeration complexes that are not subject to vibration.

Grade 105 contains 5% noble metal. It is plastic and has a slow spreading. As a result, it has the ability to fill gaps of a certain size. This brand is able to withstand minor loads of a vibration or shock nature.

Grade 115 contains 15% silver. Because of this, it has high plasticity. The seam obtained with its help is able to withstand moderate vibration or shock loads that occur during the operation of refrigeration units.

Silver solders

Silver is a noble metal, in its pure form it has good ductility. The melting point is quite high (962 °C). This makes it impractical to use pure silver as a raw material for joining parts.

But if some substances are added to silver, such as iron, bismuth, etc., then such a composition can be used to create permanent joints.

Silver materials melt well when its volume is reduced. This reduction translates into lower energy costs and lower assembly times for copper blanks.

Silver materials well envelop the parts to be joined, and this contributes to obtaining seams of the required quality. Seams obtained with the use of these products are not subject to oxidation, and are well tolerated by various kinds of mechanical and vibration loads.

The composition of all silver alloy parts used for joining is regulated by GOST. The marking of these materials begins with the letter combination PSr. And it is followed by numbers that show the percentage of silver in the alloy.

Download GOST 19738-74