Welding copper and alloys based on it requires a special approach due to the low melting point and other characteristics of the metal. There are many options for joining copper blanks. They differ depending on operating conditions and material composition.
- Preparation
- Preparation
- BUDDY TIG 160 from ESAB
Currently, there are several copper welding technologies. They are actively used in various spheres of production and life. Improved technological processes make it possible to eliminate the formation of most defects, including the appearance of pores and cracks. The work is carried out using an inverter familiar to any welder in a protective gas environment; consumables – wire and electrodes.
Weldability of copper
Copper welding is a complex operation. To perform it correctly, a person must have a good understanding of the properties and chemical purity of this reddish metal and its alloys, which are obtained by combining popular elements with it. Therefore, it will be useful for all interested parties to know the features of welding copper and its alloys.
First of all, the weldability of reddish metal is affected by the presence of alloying elements, which can be toxic and volatile. Therefore, during work, proper and effective ventilation is required to protect the personnel.
Note! In production, welding processes are carried out in a specially equipped place. It is equipped with a set of equipment that is technologically interconnected. Such a stationary place is also equipped with all the necessary tools and accessories. When performing work at home, a welding station is used for soldering copper. It is equipped with cylinders with gas mixtures, reducers and a burner.
To improve the various properties of copper, the following alloying elements are most often introduced into its composition:
- Zinc, which reduces the weldability of brass alloys. The decrease in this characteristic occurs in proportion to its quantity. Zinc boils at a low temperature. Welding copper-zinc alloys produces toxic fumes.
- Tin, which has a positive effect on the occurrence of hot cracks during the welding process, if its percentage in the alloy is from 1% to 10%. This element is less toxic and volatile than zinc. However, it often oxidizes during welding, which is why oxides appear. They reduce the strength characteristics of the seam.
- Silicon, which has a beneficial effect on weldability, as it promotes deoxidation.
- Aluminum, beryllium and nickel are elements that form oxides. They must be removed before the welding process. To prevent the formation of these oxides during operation, a shielding gas or flux and the appropriate current for the process are used.
- Oxygen, which causes an increase in pores and reduces the strength of seams if the required percentage of deoxidizers is missing in copper alloys, the most popular of which is phosphorus. These also include manganese, aluminum, silicon and iron. If copper alloys contain these elements, then it is possible to reduce the amount of oxygen, which can be in the form of cuprous oxide or in the form of a free gas.
- Lead, sulfur and selenium are included in copper alloys to increase their machinability. However, these elements not only increase weldability, but also increase the likelihood of hot cracks forming. Among them, the most harmful is lead.
- Manganese and iron do not have a significant effect on the weldability of copper alloys, since their percentage content is insignificant. Usually it is 1.4-3.5%.
Other factors also influence the weldability of both copper and its alloys:
- Thermal conductivity, which increases with decreasing number of alloying elements. Therefore, when creating a joint, such a current and shielding gas are selected so that the maximum amount of heat is introduced into the seam. It is often necessary to preheat parts to be welded that have low thermal conductivity. This process is carried out depending on the thickness of the products.
- Hot cracks appear in all copper alloys during solidification. Their number can be reduced if the parts to be joined are securely fixed during welding. Heating products also helps reduce the number of hot cracks. This process slows down the cooling of parts and reduces welding stresses.
- Welding position because copper metals have unstable characteristics. Usually work is performed in the down position. In the horizontal plane they are carried out in exceptional cases. This is the creation of corner and T welds. During their execution, the edges are cut.
- Porosity that occurs during the evaporation of elements with a low boiling point. These include phosphorus, cadmium and zinc. This effect can be reduced by fast work execution and minimal use of filler materials.
The surface condition of copper and its alloys is another factor affecting weldability. Before work, all oxides and fats must be removed from the metal. Typically a wire brush is used for these purposes. Knowing the listed features of copper welding, it is possible to make high-quality connections. However, to achieve a positive result, you still need to choose the right welding technology.
Bronze
Bronzes are alloys of copper and aluminum. They are designated by two letters “Br”, the initial letters of the Russian names of alloying elements and a series of numbers indicating the content of these elements in%.
Thus, the BrAZhMts 10-3-1.5 grade means that bronze contains 10% aluminum, 3% iron, 1.5% manganese. Some grades of cast bronze have the letter “L” at the end.
Approximate welding modes for bronze Br.AMts 9-2, Br.AZhMts 9-5-2 and brass LMNZH 55-3-1 in argon in the lower position (direct current, reverse polarity, wire Br. AMts 9-2)
| Type of connection | Size, mm | Welding process | Welding current, A | Arc voltage, V | Welding speed m/h | Electrode diameter, mm | Electrode extension, mm | Gas consumption, l/min | |
| S | b | ||||||||
| 3 | 0+1 | IDS KZ | 150-190 160-190 | 23-26 22-25 | 20-25 20-25 | 1-1,5 1-1,5 | 10-16 10-16 | 8-10 9-11 | |
| 4-5 | 0+1,5 | IDS KZ | 140-220 160-220 | 23-26 22-26 | 20-22 20-22 | 1-1,5 1-1,5 | 10-16 10-16 | 10-12 10-12 | |
| 8-10 | 0+1,5 0+2 | PAGE PAGE | 300-400 375-450 | 29-33 31-36 | 25-32 30-35 | 2-4 2-4 | 20-35 20-35 | 12-16 14-16 | |
| 14-16 | 0+2 | STR | 400-650 | 33-38 | 20-25 | 2-5 | 20-40 | 16-20 | |
| 24-26 | 0+2 | STR | 400-800 | 33-42 | 18-30 | 2-5 | 20-40 | 16-20 | |
The difficulty of welding bronzes is explained by their increased fluidity. When welding bronzes, difficulties arise due to the formation of aluminum oxide, so the welding method and technology are chosen the same as when welding aluminum, and the modes are characteristic of copper alloys.
Difficulties during welding
To perform the work efficiently, you need to find out exactly what the difficulty is in welding copper. The following features of the metal prevent the process from being carried out efficiently:
- high thermal conductivity, which is 6 times higher compared to iron;
- high fluidity, exceeding the same fatigue characteristic by 2 times;
- active oxidation, which is accompanied by the formation of cuprous oxide;
- good solubility in other molten metal, which promotes the appearance of cracks;
- high ability to absorb hydrogen and oxygen, as a result of which the seam becomes porous.
The significant linear expansion coefficient of the mussel also hinders high-quality work. Compared to steel, it is 1.5 times larger. This causes stress and deformation.
Manual arc welding
This technology for welding copper and its alloys is one of the most common methods. The popularity of this method was influenced by its technical and economic advantages. This option, when using metal electrodes, allows you to increase the speed of work. Its value is significantly higher compared to other copper welding methods.
Preparation of parts to be welded
It is recommended to carry out V-shaped cutting of metal ends when welding copper whose thickness ranges from 6 to 12 mm. In this case, the total opening angle of the ends of the part should be from 60 to 70 degrees. Its value can be reduced to 50 degrees if an underwelding seam is created on the reverse side.
Before starting work, the two parts are moved apart. The gap between them must be 2-2.5% of the length of the sheets or strips being welded. The work can also be done without first moving the parts apart, but in this case it is necessary to fix them with small words, the length of which is usually 30 mm. They should be located at a distance of 300 mm from each other. For tack welding, electrodes with a smaller diameter are used. As a result, the gap between the two parts should be from 2 to 4 mm.
Note! If the clearance is not completed, then the risk of numerous hot cracks increases significantly.
When performing arc welding of copper with a thickness of 12 mm, it is necessary to carry out an X-shaped cutting of the ends of the metal. In this case, you will have to create a seam on both sides. However, it is not always possible to open the edges in this way.
Therefore, the same V-shaped cutting is often carried out. However, this increases the work time and increases the number of required electrodes by almost 1.5 times. If you still managed to complete the required cutting, then the tacks are made on the back side of the 1st seam. After its creation they are deleted.
Connections with or without V-shaped ends are made on a flux pad. Copper, graphite or steel pads with a thickness of 40 to 50 mm are also used. They are pressed tightly to the joint. This always creates a forming groove.
Electrodes for manual arc welding process
This copper welding technology is carried out using coated electrodes. Otherwise, the seam will oxidize and the arc will become unstable. As a result, it will not be possible to make a high-quality connection, since defects form in it.
In other words, the seam will become porous. The electrodes used are in the form of copper wire. It often contains magnesium and silicon. Electrodes can also be bronze. The brand Br.KMts 3-1 is often used.
By using coated electrodes, the metal where the weld is made is ligated with manganese, silicon and phosphorus. The rods create a deoxidizing effect. The composition of the electrode coating must be selected so that during operation there is a stable arc and slag is formed. This will allow for high-quality welding of copper and its alloys, forming an excellent seam.
Modes of arc manual welding process
During operation, direct current with reverse polarity is used. If it is variable, then it will not be possible to ensure the required stability of the arc. A positive result is achieved only when electrodes containing iron are used. In addition, you will have to increase the current strength to about 50%.
Note! When using alternating current, the electrode metal often splashes.
The mode of manual arc butt welding of copper sheets using copper electrodes and direct electric current is selected depending on the thickness of the metal. Knowing this value, the electrode diameter, current strength and operating voltage are selected.
Manual Arc Welding Process Technique
If copper of considerable thickness is welded, then the work is carried out using several layers. Any seam should always be thoroughly cleaned before applying the next one. When the thickness of the copper is small or even medium, then in this case the work is carried out in one go.
The seams during such welding are created in reverse steps. Their length is usually from 200 to 300 mm. The welded area is divided into two zones. One of them should have a length of 2/3 of the length of the entire seam, and the other - 1/3. The long section is welded first. The seam should be created in the direction of the smaller area. This technology reduces the likelihood of multiple cracks occurring.
During work, the electrode is tilted in the direction opposite to welding. It must be located at an angle of 15 to 20 degrees. Often the seam created has to be corrected with a hammer, since the welded edges often bulge if the gap between the parts being joined is reduced.
Manual welding of copper pipes
Copper pipes, with a wall thickness of 3 mm or more, were connected at the waist using manual welding back in the USSR. During operation, coated electrodes are used - these are Komsomolets 100. They are also recommended to be used if copper is welded with an inverter.
The process is carried out using direct current, which must have reverse polarity. In this case, the electric current density must be 50 A/mm2. During operation, preheating is also carried out. The heating temperature is usually no more than 300 °C. In this case, complete heating is carried out during the connection of pipes, the maximum diameter of which is 50 mm. If the pipeline diameter is more than 5 cm, then local heating is performed. During welding, tack welds are also created, but they are cut out when welding a specific area. Otherwise, the metal will become porous as it is heated a second time.
Manual welding of copper pipes is carried out at a speed of approximately 15 m/hour. Do not overheat the base metal during operation. Temperature should not exceed 350 °C.
What you need to know about electrodes used for welding copper parts
To ensure a high quality weld, it is recommended to use electrodes coated with a special compound. Such a coating is necessary for the production of slag formed with metal oxides. It will prevent air from coming into contact with the weld. The coating fills the voids formed during welding of parts due to burnout of components and subsequently introduces new components into the seam. This coating contributes to better stability of the electric arc. The slag layer produced by this coating will slow down the cooling of the molten copper, causing more gases to escape from the weld.
Electrodes used in the welding process are divided into two types:
- melting - wire made of copper, steel, aluminum, cast iron is used for their production;
- non-melting - synthetic graphite and electrical coal are used for their production.
When choosing electrodes, you need to look at their color:
- yellow electrodes are intended for samples made of heat-resistant, corrosion-resistant steels;
- red - used for electric arc welding of copper products;
- gray – for blanks made of non-ferrous metals;
- blue - designed for connecting heat-resistant components.
Manual welding using carbon electrodes
If unimportant parts are connected, then copper welding with a carbon electrode is mainly used. It is better to use this method when the metal has a thickness of no more than 15 mm. Carbon electrodes must be sharpened before use. Their ends should take the shape of a cone. In this case, the length of these parts must be 1/3 of the size of the electrode. Welding is carried out with a long arc using a direct electric current of straight polarity. In this case, the current density on the electrode rod must be 200-400 A/cm2.
When welding copper at home with a carbon electrode or in production, the filler rod is not immersed in the weld pool. There should be a distance of approximately 5 mm between them.
The filler rod must also be at an angle to the product. Its value is 30 degrees. In this case, the electrode should also be held at an angle, but from 75 to 90 degrees. Flux is also used during operation. It protects the metal from oxidation. It must contain fused borax in an amount of at least 94% and 6% metallic magnesium. Before applying flux to the rod, the latter is always wetted in liquid glass.
When welding metal whose thickness is more than 5 mm, then the edges are cut before the main process. Their total angle should be from 70 to 90 degrees. In this case, the gap between them must be 0.5 mm. The welding process itself is performed on a backing made of asbestos or graphite. The electrode should be held at an angle of 10 to 20 degrees, pointing forward.
If a metal whose thickness does not exceed 5 mm is being welded, then heating is not carried out. Otherwise, the area is first heated to a temperature of 800 °C, and then the area is rapidly cooled. It is recommended to carry out welding work in one pass. This will create a seam with the best mechanical properties.
Preparatory work
Before you start working with the wires, you need to check again that there is no voltage on them.
For further work you will need a knife or special cutting tools, emery cloth, solvent, pliers or pliers, insulating tape or heat-shrinkable tubing. If heat-shrinkable tubing is used for insulation, it is very convenient to use a hair dryer, which gives a tight fit with the film.
To obtain a high-quality connection, preparatory work is carried out in the following sequence:
- Carefully remove a section of the insulating coating of at least 7 cm from the core for a core with a cross section of 1.5 mm² . If the wires are thicker, then for every 0.5 mm² of core diameter, reduce 5 mm of insulation. The cutting is carried out along the conductor with a knife or a special tool - a stripper;
- bare areas of the wire are cleaned with emery cloth;
- the surface of the conductors is degreased with acetone or white spirit;
- carefully, so as not to damage the wires, twist them into a flagellum with your hands or pliers , trying to ensure they fit snugly against each other;
- use wire cutters or mounting scissors to cut off the end of the harness to align the wires.
Manual argon arc welding
Argon welding of copper is carried out using tungsten electrodes. In this case, the current must be constant and have straight polarity in argon, which is characterized by high purity. During operation, heating must be performed if the metal thickness exceeds 4 mm. The metal heats up to 800 degrees.
Welding is also performed using copper rod. It is a filler material. It can also be used as a copper-nickel alloy or bronze. The technology for welding copper with argon with a metal thickness of more than 6 mm involves giving the edges of the parts a V-shape. Their total opening angle should be between 60 and 70 degrees.
The welding itself is carried out from left to right. In this case, the electrode should be tilted forward. The angle between it and the vertical must be from 80 to 90 degrees. At the same time, the filler rod should be inclined from 10 to 15 degrees. In this case, the extension of the electrode rod must be from 5 to 7 mm.
Semi-automatic welding
If a semi-automatic machine is used, then the work is performed using copper wire. Despite the fact that it has a small thickness, the final seam is of high quality. When welding metal with a thickness of more than 6 mm, edge preparation is carried out. They are given a V-shape. In this case, the edges can be blunted up to 4 mm. To reduce the porosity of the seam, semi-automatic welding of copper is carried out without vibrations in the transverse direction.
During the work, it is allowed to use M2 wire. Its thickness is 2 mm. In this case, it is recommended to provide a voltage of 30 V, 300 A. During the welding process, movements are performed in the transverse direction. It is recommended to additionally use flux. After proper semi-automatic welding, a seam is obtained whose performance is not inferior to the base metal.
Alternative connection methods
It is not always possible to weld current-carrying conductors. Difficulties are caused by the lack of an inverter (welding machine) or insufficient experience in performing this type of work. In this case, it is recommended to consider alternative wire connection options.
Methods for forming reliable contact between several cores:
- Twisting (crimping). It differs from the process described above in the absence of a welded joint. It is not recommended to do this, since there is a high probability of lack of direct contact between several wires, which can lead to a resistive effect - heating.
- Soldering. Unlike welding, solder and flux are used. They should fill the space between the twisted wires. Convenient for connecting small cross-section cores.
- Contact clamps. They can be screw or mechanically fixed. The former are used for switching a large number of wires. Mechanical fixation is recommended for connecting large diameter cores for networks with a high load rating.
For each technique, an individual procedure for performing work is adopted. But in any case, generally accepted safety rules are followed.
Gas welding
The connection of copper sheets, the thickness of which does not exceed 10 mm, is carried out using a welding flame. Its power is selected depending on the thickness of the copper parts. To weld one millimeter of copper, a power of 150 l/hour is required. If the process is carried out with a carburizing flame, then pores and cracks will appear in the weld.
Gas welding of copper is carried out in one layer. Otherwise, cracks will form. To prevent overheating of copper, welding is performed with rapid heating and cooling. Flux is also used during work. It could be pure borax.
Spot resistance welding
One type of resistance welding of copper is spot joining of parts. When using this method, the metal is heated to a temperature at which it begins to melt, using the heat generated by the passage of a large electric current at a specific point where the products are connected. During the process and some time after its completion, compression of the 2 parts being welded is also performed. This allows the metal of the products to fuse.
Copper spot welding has the following nuances:
- Short work time. The process can last tenths of a second.
- High welding current. Its value exceeds 1000 A.
- A little tension. Typically it has a value of 2 to 3 V.
- Significant force that is created at the spot welding site. It can reach several hundred kilograms.
- Minimum metal melting zone.
Spot welding is most often used for overlapping copper sheets. It is very rarely used for materials in the form of rods. Typically, the thickness of welded copper ranges from 0.1 to 6 mm.
During spot welding, there is no need to use electrodes, filler rods, fluxes or other materials. At the same time, the work is completed quite quickly and conveniently. As a result of their implementation, neat connections are obtained. The process is always carried out using a special welding machine for copper welding, which is characterized by high productivity.
Features of welding copper with other metals
To connect copper and various metals, you need to know a number of subtleties. First of all, you need to take into account its properties. These are the ones that need to be taken into account in order to ultimately get a high-quality seam.
Copper and steel
If it is necessary to weld copper with steel, the welding arc must be shifted to the side a short distance from the joint. It is also required to be diverted away from the copper part. If copper is fused onto steel using flux, and the process itself is carried out in protective gases, then in this case it will be possible to create a high-quality connection. It will have good resistance to stress and good ductility.
It is best to weld copper and steel using the argon arc method. In this case, the seam will contain a minimum of iron. Its amount will not exceed 10%. This value is much lower compared to the cold connection method. Welding copper with iron must be carried out using tungsten electrodes.
It is also recommended to use a plasma jet of special wire as an additive during operation. In this case, the metals and the electrode will be protected from oxidation by the inert gas that is supplied during the process.
Copper and stainless steel
It is often necessary to weld copper to stainless steel. To carry out this process, the argon arc connection method is also used. The work is performed by welding copper with a refractory tungsten electrode.
In some cases, nitrogen is used instead of argon. If this method of joining metal is used, then the tungsten rod is replaced with a graphite electrode. This is done due to the high consumption of tungsten. When welding copper and stainless steel, it is necessary to use a 10% caustic soda solution. It is used to process the edges of two metals.
Note! The difficulties when welding copper-nickel alloys are the same as when joining pure copper. This is hydrogen disease and the appearance of pores. It is also necessary to take measures to prevent water released from the coating and flux from entering the molten metal.
This is achieved by drying the filler material and adding deoxidizing agents, which include silicon manganese. The process of joining copper-nickel alloys is best done by gas welding.
You can also use the manual arc method together with a metal electrode. Semi-automatic submerged arc welding and a joining method in a protective gas environment, which is argon, are also used. In addition, resistance welding is used.
Welding copper at home
At home, copper has to be connected during installation of the heating and plumbing systems. To carry out this process, you can use the gas or argon arc method. However, you need to know that welding copper at home is much more difficult than soldering it. This statement is especially true when it comes to pipes with thin walls. To carry out this work, it is recommended to prepare in advance:
- portable welding station for soldering copper pipes;
- solder;
- flux;
- brushes;
- copper fittings;
- abrasive paper.
The copper pipe soldering station is used when making high-temperature connections. To carry out this process, it is necessary to create a temperature whose minimum value is 450 degrees. This results in strong connections. However, during the process, copper is burned out.
High-temperature soldering is always chosen when heating installations need to be carried out. At the same time, to install cold water plumbing systems, you can use a low-temperature method of connecting pipes. The same soldering method is used if copper pipes with a diameter of up to 40 mm are installed.
The process of soldering copper at home is carried out in the following sequence:
- the pipe is cut to the required length;
- with the help of a deburring device the soldering area is protected;
- flux is applied;
- the connection is heated;
- solder is applied;
- Excess flux is wiped off.
The process of soldering copper pipelines can be handled by a person without experience. Especially if she has all the necessary tools at hand. Today it is available at affordable prices from different manufacturers. Therefore, almost everyone can do the necessary work at home.
Submerged
Automatic welding can provide high quality seams. It is used in industry, since the mechanized process allows for increased productivity. Welding is carried out with a non-consumable electrode using flux. Parts require preliminary preparation. If there are gaps, it is necessary to use a lining.
The filler wire is made of M1, M2 or M3 copper. The wire is pre-hardened. In the absence of such an opportunity, bronze BrOF 40-.3 or BrKMts 3-1 is used. It should be remembered that it is copper that guarantees the absence of cracks in the weld area. To carry out such work, you need equipment with a wire feed mechanism. Most modern inverters for semi-automatic welding are equipped with a similar function, so you can work with copper at home.
