Welding brazing. Special welding and soldering methods. Welding metals: methods and types

Soldering methods are classified according to the heat sources used. The most common in industry are soldering with radiation heating, exoflux, soldering irons, flame, immersion, electric arc, induction, electrical resistance, soldering in furnaces.

Radiation heating soldering. Soldering is performed by radiation from quartz lamps, a defocused electron beam or a powerful luminous flux from a quantum generator (laser). The structure to be soldered is placed in a special container in which a vacuum is created. After evacuation, the container is filled with argon and placed in a device, on both sides of which quartz lamps are installed for heating. After the end of heating, the quartz lamps are removed, and the fixture, along with the parts, is cooled. When using laser heating, the thermal energy concentrated in a narrow beam ensures the evaporation and sputtering of the oxide film from the surface of the base metal and solder, which makes it possible to obtain junctions in an air atmosphere without the use of artificial gaseous media. With the radiation method of soldering, radiant energy is converted into thermal energy directly in the material of the solder and brazed parts. This soldering method is short-lived.

Exoflux soldering. Basically, corrosion-resistant steels are brazed in this way. A thin powdery layer of flux is applied to the cleaned junction. The surfaces to be joined are aligned, an exothermic mixture is placed on opposite sides of the blanks. The mixture consists of different components, which are laid in the form of a paste or briquettes several millimeters thick. The assembled structure is installed in the fixture
and placed in a special oven, in which the exothermic mixture is ignited at 500 ° C. As a result of exothermic reactions of the mixture, the temperature on the metal surface rises and the solder melts. This method is used to solder overlapped joints and finished construction blocks of small sizes.

Soldering with soldering irons. The base metal is heated and the solder is melted due to the heat accumulated in the mass of the metal of the soldering iron, which is heated before soldering or during the process. For low-temperature soldering, soldering irons with periodic heating, with continuous heating, ultrasonic and abrasive are used. Working part the soldering iron is made of red copper. A soldering iron with periodic heating during operation is sometimes heated from an external source of heat. Soldering irons with constant heating are made electric. The heating element consists of a nichrome wire wound on a layer of asbestos, mica, or on a ceramic sleeve mounted on a copper rod of a soldering iron. Soldering irons with periodic and continuous heating are more often used for flux soldering of ferrous and non-ferrous metals with soft solders with a melting temperature below 300-350 ° C. Ultrasonic soldering irons are used for flux-free low-temperature soldering in air and for soldering aluminum with low-melting solders. Oxide films are destroyed by ultrasonic frequency vibrations. Abrasive soldering irons can be used to solder aluminum alloys without flux. The oxide film is removed by rubbing the soldering iron against the metal.

The assembly of units for soldering is essential. The assembly should ensure the fixation of the relative position of the parts with the required gap and the flow of solder into the gap. In cases where the solder is pre-laid in a foil-like joint and then the assembly is heated (for example, in a vacuum oven), it is necessary to ensure that the parts are compressed at the soldering temperature with a certain force. If this force is not enough, the seam will be too thick with insufficient strength. Excessive compression can damage the brazed assembly.

Special devices are used to compress parts during soldering. The necessary compressive force is provided by mechanical clamps or the difference between the thermal expansion of the product material and the material of the fixture. The latter method is often the only one when brazing is carried out at high temperatures.

Flame brazing. When soldering, heating is carried out
flame of a gas burner. As a combustible gas, mixtures of various gaseous or liquid hydrocarbons (acetylene, methane, kerosene vapor, etc.) and hydrogen are used, which, when burned in a mixture with oxygen, produce a high-temperature flame. When soldering large parts, flammable gases and liquids are used in a mixture with oxygen, when soldering small parts - in a mixture with air. Soldering can be carried out both with special torches, giving a wide torch, and with normal, welding blowtorches.

Soldering by immersion in molten solder. The molten solder in the bath is covered with a layer of flux. The part prepared for soldering is immersed in molten solder (metal bath), which is also a heat source. For metal baths, copper-zinc and silver solders are usually used.

Soldering by immersion in molten salt. The composition of the bath is selected depending on the soldering temperature, which must correspond to the recommended bath temperature of 700–800 ° C when working with a mixture of a certain composition. The bath consists of sodium, potassium, barium chloride, etc. This method does not require the use of fluxes and a protective atmosphere, since the composition of the bath is selected such that it fully ensures the dissolution of oxides, cleans the brazed surfaces and protects them from oxidation when heated, i.e. .is a flux.

The parts are prepared for soldering, solder is placed on the seam in the right places, and then dipped into a bath with molten layers, which are flux and a heat source, where the solder melts and fills the seam.

Electric arc soldering. In arc brazing, heating is carried out by a direct arc burning between the parts and the electrode, or by an indirect arc burning between two carbon electrodes. When using a direct arc, a carbon electrode (carbon arc) is usually used, less often a metal electrode (metal arc), which is the solder rod itself. The carbon arc is directed to the end of the solder bar touching the base metal so as not to melt the edges of the part. A metal arc is used at currents sufficient to melt the solder and very slightly melt the edges of the base metal. For direct arc brazing, zinc-free high temperature brazing alloys are suitable. With the help of an indirect carbon arc, it is possible to perform the brazing process with high-temperature solders of all types. For heating in this way, a special coal burner is used. The current is supplied to the electrodes
from an arc welding machine.

Induction brazing ( soldering with high frequency currents). With induction brazing, the parts are heated by eddy currents induced in them. Inductors are made of copper tubes, mostly rectangular or square, depending on the configuration of the parts to be soldered.

In induction brazing, the rapid heating of the part to the brazing temperature is achieved by using high energy concentration. Water cooling is used to protect the inductor from overheating and melting.

Soldering with electrical resistance. With this method of soldering, an electric current of low voltage (4–12 V), but of a relatively high strength (2000–3000 A), is passed through the electrodes and in a short time they are heated to a high temperature; parts are heated both due to the thermal conductivity from the heated electrodes, and due to the heat generated by the current during its passage in the parts themselves.

When an electric current passes, the soldered joint is heated to the melting temperature of the solder, and the molten solder fills the seam. Contact soldering is carried out either on special installations that provide power supply with high current and low voltage, or on conventional machines for resistance welding.

Soldering in ovens. For brazing, electric ovens and, less often, flame ovens are used. Heating of parts for soldering is carried out in conventional, reducing or protective environments. Soldering with high-temperature solders is performed using fluxes. When brazing in controlled atmosphere furnaces, parts of cast iron, copper or copper alloys to be brazed are assembled into assemblies.

Soldering of metal compounds with non-metallic materials. Brazing can be used to obtain metal compounds with glass, quartz, porcelain, ceramics, graphite, semiconductors and other non-metallic materials.

Post-soldering treatment involves removing flux residues. Fluxes partially remaining on the product after soldering spoil it appearance, change the electrical conductivity, and some are corrosive. Therefore, their remnants after soldering must be carefully removed. Residues of rosin and alcohol-rosin fluxes usually do not cause corrosion, but if, according to the operating conditions of the products, they need to be removed, the product is washed with alcohol, alcohol-gasoline mixture, acetone. Aggressive acid fluxes containing hydrochloric acid or its salts are thoroughly washed
successively with hot and cold water using hair brushes.

Typical solder joints are shown in fig. 2.1. Brazed seams differ from welded seams in their structural form and method of formation.

The type of soldered joint is selected taking into account the operational requirements for the assembly and the manufacturability of the assembly in relation to soldering. The most common type of connection is lap soldering.

Rice. 2.1. Typical solder joints

In units operating under significant loads, where, in addition to the strength of the seam, tightness is required, the parts should only be overlapped. Lap seams provide a strong connection, are easy to perform and do not require adjusting operations, as is the case with butt or whisker brazing.

Butt joints are usually used for parts that are irrational to be made from a whole piece of metal, as well as in cases where it is undesirable to double the thickness of the metal. They can be used for lightly loaded nodes where it is not required
tightness. The mechanical strength of the solder (especially low-temperature) is usually lower than the strength of the metal being joined; in order to ensure the uniform strength of the soldered product, they resort to increasing the seam area by means of an oblique cut (in a mustache) or a stepped seam; often a combination of a butt joint with an overlap is used for this purpose.

Brazing can be used to manufacture complex configurations of units and whole structures, consisting of several parts, in one production cycle(heating), which allows us to consider soldering (as opposed to welding) as group method joining materials and transforms it into a high-performance technological process, easily amenable to mechanization and automation.

When soldering, the following defects are possible: displacement of the soldered elements; shells in the seams; porosity in the solder joint; flux and slag inclusions; cracks; do not drink; local and general deformations.

In today's unstable world and aggressive external environment a person especially carefully tries to preserve the space around him, to make his "small" world more reliable. A car has long been a necessary element of everyday life, but when we go out on the road, we find ourselves in a zone of increased danger. When purchasing a car, the buyer great attention pays attention to security issues. Any participant in the movement wants not only to avoid possible accidents on the roads, but also to stay alive if an accident does occur.

Since 1997, the European Committee EuroNCAP has been conducting independent crash tests of car safety, checks cars in various non-standard emergency situations, evaluates its safety for drivers and passengers, and compiles a safety assist rating for cars.

All of these crashing efforts are aimed at testing the effectiveness of passive vehicle protection systems. And it is not in vain, since in the event of an accident, the reliable operation of these systems can save the lives of the driver and passengers.

Car manufacturers pay due attention to the safety of passengers. For example, the Ford Fusion body has a specially designed structural frame to absorb impact energy in the event of a collision, and the doors are reinforced with steel bars. The body of the Audi A3 is designed with increased rigidity and energy-absorbing legroom for passengers, which will provide the driver and passengers with reliable protection in the event of an impact.

New requirements - new steels

To increase competitiveness, manufacturers are trying to create economical and safe vehicles. New requirements for a modern car body are dictated by the desire to get a more economical, and therefore lighter body; at the same time, the requirements for passive safety should be in fact high level... All of this is pushing automakers forward.

New body structures, innovative technologies

New concepts of car body construction are directly related to innovative technologies... Typically, this is a lightweight construction using ultra-high-strength steel, light metals such as aluminum and magnesium alloys, the use of fiber-reinforced plastic, or various combinations of all these materials in one body structure. All this is dictated by both the economic problems solved in mass production and the desire of consumers to get an economical and safe car.

Today there are two paths that manufacturers follow: technologies of hybrid joints, light alloys, with the use of glue, which allows to distribute the loads in the joints over the entire contact surface, and mechanical-thermal methods of joining. The goal is to find processes that are easily implemented in production and subsequently reproducible when restoring the body after an accident. Now it is impossible to say which of the methods will become more widespread, since metal suppliers, in collaboration with car manufacturers, are constantly developing new alloys and metal processing methods in order to obtain the required characteristics. Often new alloys and new metal working methods open up new application possibilities.

Types of steels and alloys used in car body structure

Steel

Mild steel up to 200 N / mm2

High-strength steel HSS 210-450 N / mm2

Extra strong steel EHS 400-800 N / mm2

Aluminum alloys

Aluminum magnesium AlMg approx. 300 N / mm2

Aluminum silicon AlSi approx. 200 N / mm2

New steels - new repair technologies

MIG brazing - new technology joints, also called brazing welding, are used to join high-strength steels of automobile body panels. High strength steels such as Boron have achieved their high stiffness ratings through heat treatment. But in conventional welding with a semiautomatic device, the temperature of the weld pool is 1500–1600 ° C, which leads to changes in the characteristics of the metals being joined and, as a consequence, to changes in the entire body structure. As a result, we get a "disabled body", which carries a latent threat.

MIG brazing process is a brazing process hard solder... The welding process MIG-brazing (Metal-Inert-Gas), as the name implies, takes place in an inert gas argon. The gas protects the arc, molten solder and the edges of parts from the influence of ambient air. The process itself is simple, like MIG / MAG welding, and is applicable in body rebuilding conditions. Due to the lower melting temperature of the solder - about 1000 ° C - no diffusion of metals occurs, and due to the relatively low temperature of the bath, the inherent properties of the steels being joined are preserved. This method practically eliminates deformation of the sheets to be joined.

I would especially like to note that due to the lower melting temperature of the solder, there is a minimum burnout of zinc during brazing (zinc melts at 419 ° C, evaporates at 906 ° C). The resulting seam is highly resistant to corrosion. Brazing wires are made of a copper-based alloy with silicon (CuSi3) or aluminum (CuAl8) additives. The solder combines with zinc, and the result is a weld with high anti-corrosion properties.

The welding-brazing process takes place at lower current settings, much lower than conventional mild steel, which is necessary to obtain a low pool temperature. In this case, the pushing method is used: the torch is guided at an obtuse angle in the direction of the weld. The burner must be tilted no more than 15 ° from the vertical so that the gas is not blown out of the bath area and protects it. The gas consumption must be within the range of 20–25 l / min, for this it is necessary to use a reducer with a flow meter.

When welding-butt-brazing two sheets, it is necessary to create a gap between them, approximately equal to the thickness of the sheet to be welded (about 1–1.2 mm), and leave a place for filling with solder. The wire feed speed is higher than usually used for welding.

You can check how strong the weld-solder seam is; we got about 30 cycles of bending the seam. The result can be seen in the photographs: the seam remained intact, the joint turned out to be stronger than the main steel plate. The test was carried out with simple steel plates, the first sample with high-strength steel did not break; apparently, this requires a special device, and not just a vice.

New repair technologies - new repair equipment

The quality of repair of a damaged body requires not only uncompromising accuracy of restoring the body structure in accordance with the manufacturer's data, but also the use of those methods that will not violate the strength characteristics of the structure. If you are going to carry out repairs in accordance with the requirements of the car manufacturer, it is necessary to apply modern repair methods, which are solved with the help of OEM (Original Equipment Manufacturer) equipment.

MIG / MAG semi-automatic machines with the ability to weld-solder are now available for body shops. The French manufacturer GYS offers two models with this feature: TRIMIG 205-4S and DUOGYS AUTO. Both units are designed specifically for body repair. Of greatest interest is the DUOGYS AUTO model, which we will consider in more detail.

The DUOGYS AUTO professional semi-automatic welding machine is ideal for body repairs at service stations working with modern bodies. It is designed for working with steel, aluminum and welding-brazing of high-strength steels using CuSi3 or CuAl8 wires.

■ Wire CuSi3 is used on technological requirement OPEL and Mercedes.

■ Wire CuAl8 is used according to the technological requirements of Peugeot, Citroen, Renault.

■ Aluminum wire AlSi12 is used for welding automotive sheets with a thickness of 0.6–1.5 mm.

■ Aluminum wire AlSi12 is used for welding automotive sheets with a thickness of more than 1.5 mm.

This machine is equipped with two four-roller mechanisms with the possibility of connecting a torch with an integrated Spool Gun feeder. It comes with two three-meter 150 A torches: one for working with steel, and the other for welding-brazing, and a Spool Gun with a four-meter sleeve. Thanks to the synergistic mode, the device can be easily reconfigured for different operating modes.

DUOGYS AUTO has two tuning modes: automatic and manual. IN automatic mode it is necessary to select the type and diameter of the welding wire, supply required level current on the seven-position switch, and the wire feed speed will automatically adjust according to the set conditions. At the same time, there is an opportunity for fine adjustment of the speed. If necessary, you can always go to manual mode and work as with a conventional semiautomatic device.

The device has two useful modes. The spot SPOT mode is convenient for sticking operation. Delay mode is convenient for welding thin sheets of steel and aluminum, while limiting the risk of burn-through or deformation of the welded sheets.

For body stations with low traffic, we recommend the professional welding semiautomatic device TRIMIG 205-4S. It has exactly the same power generator as its older sibling DUOGYS AUTO, but with only one built-in two-roller drive mechanism and will require additional time to reinstall the wire spools.

Otherwise, it is the same machine, with its help you can weld steels, welding-soldering, and by connecting a torch with a built-in Spool Gun wire feeder, and aluminum welding.

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 possibilities to protect steel from corrosion, zinc is of particular importance due to its anti-corrosion qualities, on the one hand, and its low price, on the other.

The zinc layer applied to 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, the construction industry, in ventilation and air conditioning equipment, in household appliances etc.

Due to cathodic protection, zinc has great importance to protect steel from corrosion. If the protective layer of zinc is damaged, then the zinc coating affects the iron by cathodic protection. This also affects the distance 1 - 2 mm on an uncoated surface. Due to the remote effect of zinc cathodic protection, both non-galvanized edges of sheet cuts and microcracks, which arise as a result of cold working by pressure, are protected, as well as the surrounding of the weld, in which zinc evaporates. In the same way, on the basis of cathodic protection, underfilm corrosion of the zinc layer of the cut edges is excluded.

What is the essence of welding - brazing 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, defects welding joints and an unstable arc. Therefore, it is more favorable for galvanized parts if less heat is installed. An alternative for welding - brazing 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. The advantages of using these wires are:

no corrosion of the weld;
minimal spatter;
low burnout of the coating;
low heat input;
simple post-treatment of the seam;
cathodic protection of the base material in the immediate area of the seam.

Due to the high copper content, these filler materials have a relatively low melting point (depending on the alloy composition - from 950 to 1080 ° C). The base material does not melt, which means that the connection is more like soldering. Hence the designation "Welding - brazing, or MIG brazing" also originates. A shielding gas is recommended, usually argon.

Filler materials

The following copper alloys are recommended for welding - brazing galvanized sheets:

CuSi3; CuSi2Mn; CuA18

In practical applications, filler materials such as CuSi3 are used most often. Their significant advantage is low strength, which facilitates subsequent machining. The flowability of the filler material is determined in a significant way due to the silicon content. With an increasing silicon content, the melting becomes viscous, therefore, it is necessary 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, its machining is more difficult than with other copper alloys. This wire is primarily used where no further machining is required. Welding filler material of the SiA18 type is used primarily for aluminum-coated steel.

In the process of welding - brazing, a predominantly controlled transition of material into the seam is used, therefore, a pulsed welding arc. In some cases of application, especially with thick layers of zinc from 15 microns, a large amount of fumes can lead to instability of the soldering or welding process. Therefore, it is more convenient in cases of this type to use a short welding arc, which can be held more stable. In this case, high requirements are imposed on the power supply and its regulation characteristics.

In an environment of an argon-rich shielding gas, a controlled, short-circuit-free transition of the material into the seam is achieved by proper selection of the parameters of the main and pulse currents (Fig. 1).

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

At optimal choice parameters, a drop of filler material is detached from the wire electrode by impulse. As a result, the process is almost spatter-free. Research has shown that different filler materials and shielding gases require different pulse shapes. This resulted in a “cut-off” pulse shape for each filler material. This is especially true for bronze and copper wires.

In order to keep the evaporation of zinc as low as possible in thin sheets, the process must be carried out at a low current strength. Therefore, the main requirement is that the current source in the lower power region provides a particularly stable arc. A low setting of the main current is just as important as a fast-reacting arc length control so that the arc length can be kept for a short time. The consequence is a slight heating of the base material and a decrease in the amount of zinc evaporation. As a result of both effects, there is a small number of pores (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 pulsed arc welding (plate thickness 1.5 mm)

Synergy mode

A good result of MIG brazing of 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 multitude of infinitely adjustable parameters (approximately thirty parameters), it is possible to improve droplet separation in pulsed arc welding without any problems, or to use short circuit in short arc welding for a large number of filler materials. These additional parameters complicate the maintenance of the power supply and would therefore limit the range of users to only experts.

Using the so-called synergy mode ( digital control) with preprogrammed parameters for each wire and gas combination, this process is very easy to operate for the user.

Manufacturer welding machines takes on the task of optimizing parameters for many different base and filler materials as well as shielding gases. This scientifically substantiated result is recorded in an electronic storage device in the form of a data bank. The user gets a choice of parameters for any filler material right at the power source. The built-in microprocessor takes care of the infinitely variable power selection in the range from minimum to maximum.

Wire feed

Compared to standard wires, bronze wires are very soft. Therefore, special requirements are imposed on the wire feeder. The filler wire must be fed freely, without friction. The 4-roller drive with the feed rollers involved transmits itself with a low clamping force sufficient force to feed the wire. Smooth rollers with a semicircular groove are commonly used. To maintain a small frictional resistance in the hosepack, a Teflon or plastic conduit must be used. Precise wire entry into the contact tip is another basic prerequisite for trouble-free wire feeding.

A precisely sized contact tip in the torch provides a reliable contact for transmitting current to the bronze wire.

Application examples for welding - brazing

Welding process - brazing can be used for both un-alloyed and low-alloyed, and for stainless steels... This method is mainly used for galvanized steel. Slight burnout of the layer both in the immediate area of the weld and on the back side is due to low heat input and low melting point of the filler material.

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

All types are suitable for welding - brazing. welding seams and welding positions that are known for gas-shielded welding. Both the vertical seams (bottom-up and top-down) and overhead positions are flawless. The welding speed for MIG brazing is identical to that for MAG (up to 100 cm / min).

It 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, the flame of a gas burner, laser energy or other sources of thermal energy are used to heat the metal.

Capillary soldering is the most common. Many, using it, do not even know about 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. Part surface wetting and solder retention is largely due to the capillarity effect.

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

Diffusion

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

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

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

The diffusion view requires strict adherence to the temperature and time regime. The heating temperature in the soldering zone is always higher than the melting point of the solder.

Contact-reaction

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

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

Low-melting materials are used - eutectics. So you can combine silver and copper, where a copper-silver alloy will be formed between the parts. Soldering of tin and bismuth, silver and beryllium, graphite and steel is carried out.

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

Reaction-flux

The reactive-flux type of soldering is based on a chemical reaction in which a solder is formed from the flux when combined with the metal. This can be clearly seen when aluminum parts are interconnected.

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

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

Sometimes, with this type of soldering, it is necessary to add in small quantities, as an addition to the main process. This is usually done when two pieces 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, instead of an additive, a solder is used. This type is most often used in order to close up defects and flaws on the surfaces of metal parts (cast).

The process itself can be carried out in different ways:

soldering in ovens;
dipping in;
resistance using electric current;
induction;
radiation;
using soldering irons and gas torches.

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

In ovens

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

In this case, heating in the furnace can take place in one of many existing methods, ranging from heating by a flame, and up to complex technological processes, such as induction, electrical resistance.

The design of the furnaces themselves differs from each other only by the hearths on which the brazed workpieces are laid. For large parts, furnaces are used in which the underneath 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. Furnace brazing can be fully mechanized, leading to increased productivity. And for industries with a mass output finished products this is ideal.

Application of induction and resistance

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

Two methods of soldering are realized here: stationary and with movement of the part or 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 both through the workpieces and through the soldering element. That is, the parts to be connected become part of the electrical circuit.

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

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

Immersion in the bath

Immersion soldering is carried out either in molten solder or in a mass of special salts. The last type of soldering is a quickly carried out operation due to direct heating of the workpieces from salts, which perform the functions of both a heating element and a flux. With regard to immersion in solder, it should be noted the possibility of full or partial immersion.

Radiation method

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

The technology appeared relatively recently, but has shown that in this way it is possible to achieve high quality soldering of two metal blanks. In addition, a real opportunity has appeared 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 of the soldered seam.

The gas envelope in the joint zone, formed due to the heating of the metals, makes it possible to not use fluxes during the joint. Therefore, when today they talk about soldering without flux, they mean laser technology.

Torch and soldering iron

As for soldering with torches, two technologies are most often used, which, in fact, do not differ from one another. There is simply heating of 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 stream at high speed). It should be noted that the method with gas burners is considered universal.

Plasma torches operate at high temperature conditions... 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 (up to a certain accuracy).

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

I would like to mention the ultrasonic soldering irons. That is, ultrasound itself is related to the soldering process only from the point of view of the destruction of the oxide film.

Therefore, it became possible to solder various metals in an air environment without flux materials. Soldering directly occurs from the heating of the solder.

Vacuum

Soldering in a vacuum is still not used always and not everywhere today. The complexity of this type is 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 that covers metal workpieces and solder.

The film is very refractory; during soldering, temperature degrees are lost for heating 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 brazing is one such option.

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

low productivity of the process, because each individual part has to be heated;
in this way, only small workpieces 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

This is not to say that the selective type of soldering is fundamentally different from capillary. Similarly, it uses solder and heating. But the solder is melted only in selective places (local points) to which the elements are planned to be attached.

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

Selective soldering plant - equipment belonging to the category of semiautomatic devices. It is not cheap, but it saves consumables almost ten times compared to the wave, so it spreads wider and wider.

Temperature conditions and materials

The classification of soldering processes is based on the methods of operations, the conditions under which the joints are obtained, and on the types Supplies... 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 view (soft).

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

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

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

15.05.2013

The last article briefly described the problem of joining body parts of a modern car made of high-strength steel. One of the solutions welding-brazing, a word familiar only in narrow circles of professionals in body repair.

What welding-brazing What tasks it solves, what equipment is needed for welding in this way and what materials are used to join parts made of high-strength steel, we will try to summarize in our article.

High strength or multiphase: These steels of the latest generation have been further processed in order to increase their strength up to 1600 MPa. They are mainly used to create anti-shock zones in the car body. For example: Porsche 997, OpelCorsa 07.

High strength or multiphase steels are a compound of bainite, austenite and ferrite. These steels provide high strength and good deformability. They are used in the production of complex parts that are important for the stability of the vehicle.

With all the advantages, high-strength steel also has disadvantages. A more complex production process, a decrease in strength with strong heating, the need to use special equipment at the service station and the use of modern working methods, the obligatory replacement of a body element in case of damage, straightening of damaged parts is prohibited, the use of semi-automatic welding with steel wire is strictly prohibited.

MIG brazing in shielding gas is the most modern method welding for the latest species steels. This method is also called MIG brazing or copper MIG welding.

This welding method is more and more used by various car manufacturers and is more and more recommended for repairs (Mercedes, Opel, VW, Peugeot, Toyota, Honda). The term is used soldering because the sheets of metal that are connected do not melt, in contrast to welding MIG / MAG orsemi-automatic welding . The reason for this is operation at a lower temperature, around 900 ° C.

Due to the low temperature of the weld pool, the zinc layer is practically not damaged, and thus the anti-corrosion protection is preserved. For modern steels with a high elastic limit, the material properties do not change and the deformations are insignificant. This method also helps reduce spatter when welding.

The melting point of copper alloys is much lower: between 750 ° C and 1080 ° C. Since the melting point of steel is approximately 1500 ° C, MIG brazing will not melt the steel sheet or alter the original properties of special steels.

MIG brazing only melts the wire, not the sheets to be welded

The wire used is made of an alloy of copper and zinc. It is a more noble metal with very good anti-corrosion properties. The most commonly used wire is 0.8 - 1.0 mm in diameter, depending on the apparatus and, as a rule, it is CUSI3. Principle welding-brazing consists in fusing a CUSI3 or CUAL8 wire onto a wall piece at a not very high temperature. Wire diameter 0.8 mm for the device with the program " Welding-brazing»And 1 mm for a pulsed device.

In MIG brazing, the bonding takes place by diffusion. It is a superficial but very stable seal that allows very good filling. The filler metal (copper) is transferred by capillary action (good filling in joints and cracks) and thus completely protects the bare edges of the sheet metal in the brazing area.

Along the edge of the braze, the zinc layer melts and combines with the copper to form a protective layer. In other words, the back of the weld is protected from rust.

For welding-brazing(high tensile metal) using a copper-silicon alloy wire CusI3 or a copper-aluminum alloy CuAl8 (Ø 0.8mm and Ø 1mm), the welder must use a neutral gas: pure argon (Ar). Ask a gas sales specialist for advice on gas selection. Gas flow between 15 and 25 L / min.

Welders RedHotDot HOTMIG-19, HOTMIG-27 and HOTMIG-29 perform welding-soldering, for this it is necessary to connect a cylinder with Argon, select the NORMAL 2T mode, select a wire diameter of 0.8 or 1.0, select a position on the CuSi / CuAl control panel.