How is copper welded?

Copper refers to non-ferrous metals that have a certain distribution in engineering and construction. It has good electrical and thermal conductivity, corrosion resistance, perfectly amenable to machining. It should be noted that the welding of copper has its own characteristics, due to the physicochemical properties of this metal.

The design of transformers for spot welding copper

The design of transformers for spot welding of copper.

Depending on the chemical composition and purpose. copper according to GOST 859-78 produced five names:

  • cathode (contains a small amount of impurities in the range of 0.003-0.1%);
  • oxygen-free (oxygen content not more than 0.003%);
  • cathodic remelted (impurity content in the range of 0.01-0.5%);
  • deoxidized (impurity content in the range of 0.01-0.5%);
  • fire refining (impurity content in the range of 0.01-0.5%).

Cathode copper is used for the manufacture of conductive parts, cathodes, wires, other names of copper are used for the production of copper ingots and semi-finished products.

Features of welding copper materials

The technology of welding copper, like any other non-ferrous metal, has its own distinctive features, due to its chemical and physical properties. For example, the process of combining this material is significantly hampered by the high ability of copper to oxidize in the heated or molten state and its high fluidity and thermal conductivity.

It should be noted that various impurities contained in the composition of copper of different grades (oxygen, antimony, bismuth, arsenic, sulfur, phosphorus) also have a certain influence on the welding process. Especially negative effect on the welding process is bismuth.

During heating and melting, copper oxidizes to form monovalent oxide Cu2O, which, interacting with hydrogen dissolved in the metal, leads to the appearance of cracks in the material, i.e. to the so-called "hydrogen disease".

Copper welding modes

Copper welding modes.

It should be noted that cathodic electrolytic copper is best welded with a percentage of impurities up to 0.05%.

There are a number of ways to connect copper elements. To do this, use the following types of welding: gas, in a protective inert environment (nitrogen or argon), electric manual and automatic. It should be noted that any welding work should be carried out in a room where there is forced-air and exhaust ventilation. It is necessary to use overalls, safety shoes and personal protective equipment: leather gloves, a shield. Welding equipment must be in good condition.

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Manual arc welding

With this technology, copper welding requires the following devices and materials:

  • electrodes, flux and filler material of the appropriate type;
  • DC welding generator.

The technology of manual arc welding of copper materials is carried out using graphitized (carbon) or metal electrodes. For domestic products such as ZT, brass of L90 brand, copper wire of M1, M3, M2 brand, bronze wire Br, KMts3-1 (silicon-manganese), bronze rods of brand Br, 0F4-0.25 (tin-phosphorous) are used as rods.

Manual arc welding scheme

Scheme of manual arc welding.

The electrode rods are coated with special chemical compositions (coatings) according to the reference literature. The thickness of the electrode coating should be selected according to the reference literature, depending on the type of electrode. After the coating is applied, the electrodes must be dried for 3-4 hours in air at a temperature of + 20 ° ... + 30 ° C, then calcined for 90-120 minutes at a temperature of + 250 ° ... + 300 ° C.

Manual arc welding of copper materials by means of a metal electrode is carried out with a constant current (reverse polarity) according to the following parameters (I is the amperage, A, d is the electrode cross section, mm, S is the sheet thickness, mm):

  • S = 2, d = 3, I from 120 to 150;
  • S = 3, d = 3-4, I from 160 to 210;
  • S = 4, d = 4, I from 240 to 280;
  • S = 5, d = 5, I from 300 to 350;
  • S = 6, d = 5-6, I from 330 to 380.

In the process of copper connection using graphitized electrodes, rods having marks similar to those of metal electrodes are used as additives. In order to optimize the arc welding of copper parts and structures, a suitable flux is used with a graphite electrode, which at the beginning of work is added to the groove or coated with filler material. The chemical composition of the flux is chosen according to the directories.

Non-consumable electrode welding scheme

The scheme of welding with a non-consumable electrode.

The technology of manual welding of copper elements using a carbon electrode is carried out according to the following parameters (I is the strength of the welding current, A, d is the electrode section, mm, S is the sheet thickness, mm):

  • S = 1, d = 4, I from 135 to 180;
  • S = 2, d = 6, I from 195 to 260;
  • S = 4, d = 6, I from 250 to 330;
  • S = 6, d = 8, I from 315 to 430;
  • S = 12, d = 10, I from 420 to 550.

If the cross section of the sheet does not exceed 4.0 mm, then manual arc welding is carried out without dividing the edges. Without gaps, it is necessary to assemble butt joints.

Details over 0.5 cm thick before welding should be preheated to a temperature of + 200 ° ... + 300 ° C. Connections T-shaped and angular weld, positioning "in the boat."

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Arc welding of copper welding machine

The following materials and tools are needed for this type of copper welding:

  • electrodes, additives and flux of the appropriate type;
  • welding machine;
  • graphite lining.
Classification of methods of welding in protective gas

Classification of welding methods in protective gas.

Automatic electric arc welding of copper structures and parts is carried out using flux electrodes of two types: metal-melting and non-melting of graphite. A variety of flux and filler materials are selected according to the reference literature.

In the case of the use of a graphite electrode, welding is carried out by means of a special automatic type head moving along the weld at a fixed speed. In this type of compound, a filler metal, a graphite lining under the welded copper and a brass strip are used.

The technology of automatic arc welding of copper materials using a carbon electrode with a cross section of 20.0 mm has the following parameters (I is the current strength, A, V is the welding speed, m / h, S is the cross section of sheets, mm, U is the arc voltage, V):

  • S = 4, I = 780-800, U = 18, V = 22.4;
  • S = 6, I = 960-980, U = 18, V = 22.4;
  • S = 8, I = 1000, U = 18-19, V = 16.

Automatic arc welding of copper is performed by ordinary welding machines with a metal electrode. When this is used, the electrode copper wire grades M3, M1, M2 and a diameter of 1.6 to 3.0 mm. Such welding is carried out on a constant current (reverse polarity). Apply flux according to the references. Some types of fluxes allow, in particular, automatic welding of copper elements on a variable current.

Argon arc welding of copper

Argon arc welding of copper.

It should be noted that automatic arc welding of copper, depending on the type of connection, has its own distinctive features and certain modes. So, in the case of a one-sided seam, the material is welded with penetration through using a graphite lining.

In addition, sheets with a cross section of less than 8.0 mm are cooked without cutting edges, according to the following parameters (d is the wire diameter, mm, I is the amperage, A, S is the sheet thickness, mm, U is the arc voltage, V, V is speed, m / h):

  • S = 2, d = 1.6, I = 140-160, U = 32-35, V = 25;
  • S = 3, d = 1.6, I = 190-210, U = 32-35, V = 20;
  • S = 4, d = 2, I = 250-280, U = 30-35, V = 25;
  • S = 5, d = 2, I = 300-340, U = 30-35, V = 25;
  • S = 6, d = 2, I = 330-350, U = 30-35, V = 20;
  • S = 8, d = 3, I = 400-440, U = 33-38, V = 16.

In the course of welding of a thicker material (more than 8.0 mm), the cutting of the letter “V” at an angle of 60 ° is used. The process of joining joints with cut copper edges with double-sided seam is carried out according to the following parameters (angle of groove edges is constant and is 60 °, S is sheet thickness, mm, I is amperage, A, U is arc voltage, V, V is speed, m / h):

  • d = 10, dull edges = 5 mm, I = 540-560, U = 33-38, V = 15;
  • d = 12, dull edges = 6 mm, I = 580-600, U = 35-38, V = 15.
Argon welding

Welding in argon.

Copper joints with overlap are welded using the following technology according to such parameters (S is sheet thickness, mm, I is amperage, A, U = 30-35 V is arc voltage, V, V is speed, m / h):

  • S = 3, I = 220-240, V = 25;
  • S = 4.5, I = 300-340, V = 25;
  • S = 6, I = 350-400, V = 20.

It should be noted that copper sheets with a thickness of 8 to 12 mm must be boiled on both sides. Also, in order to quickly ignite the welding arc, it is advisable to pour brass chips under the wire of electrodes before starting welding.

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Copper welding in a protective inert gas environment

In addition to the above types of compounds, copper materials can also be welded in nitrogen or argon with two types of electrodes: consumable metal and non-consumable tungsten. The most common variant of this type of compound is welding in an inert argon medium with a non-consumable tungsten electrode on a current of direct polarity and a constant value.

Effect of preheating temperature on the wetting angle during copper welding

Effect of preheating temperature on the wetting angle when welding copper.

The following components and devices are necessary for this type of copper welding:

  • electrodes, flux and filler material of the appropriate type;
  • welding holders, dried argon (99.8% purity), welding machine for argon-arc connection.

In the role of the additive material are rods (mark M2, M1, M3). The technology of this type of connection of copper elements has the following parameters (I - current strength, A, Dp - diameter of the filler wire, mm, Qa - argon consumption, l / min, S - sheet thickness, mm, De - diameter of tungsten electrode, mm) :

  • S = 1.6, Dn = 2.4, De = 2.4, I = 80-110, Qa = 2.8-3.3;
  • S = 3.2, Dn = 3.2, De = 3.2, I = 200, Qa = 6;
  • S = 6.4, Dп = 4.8, De = 4.8, I = 300, Qa = 7;
  • S = 10, Dn = 4.8, De = 4.8, I = 350, Qa = 7;
  • S = 12, Dn = 6.4, De = 4.8, I = 400, Qa = 8;
  • S = 16, Dn = 6.4, De = 4.8, I = 400, Qa = 8.

In the case of copper welding in a protective gas environment with a consumable metal electrode, the connection is carried out on a current of constant force and direct polarity. The material of the electrodes in this case is chosen according to the reference literature.

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How is gas welding done?

For this type of connection of copper elements the following materials and tools are needed:

  • electrodes, flux and filler material of the appropriate type;
  • acetylene generator, charged with water and calcium carbide, or acetylene cylinder;
  • oxygen bottle;
  • hoses;
  • burner.
Copper Gas Welding Scheme

The scheme of gas welding copper.

Gas welding of copper parts and structures is the most common type of welding of copper elements. When using this type of joining sheets with a thickness of less than 5.0 mm, filler materials from copper grades M1, M2, M3 are used.

If it is necessary to conduct welding of thicker copper sheets, then a wire with a phosphorus content of 0.2% and silicon of 0.15-0.3% or a copper wire with a phosphorus content of 0.2-0.7% should be used. In this type of work, fluxes are used according to the reference literature.

The technology has the following parameters (S is the thickness of copper sheets, mm, No. is the number of the tip of the welding torch, Dp is the diameter of the filler wire, mm):

  • S < 1, Dп = 1.5, № 00-0;
  • S = 1-1.5, Dп = 1.5, № 1;
  • S = 1.5-2.5, Dp = 2, No. 2;
  • S = 2.5-4, Dп = 3, № 3;
  • S = 4-8, Dп = 5, № 4-5;
  • S = 8-15, Dп = 6, № 6;
  • S > 15, Dп = 8, № 6-7.
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Heat treatment

At the end of the copper welding in any way, the joints should be forged through joints. If the cross section of welded sheets is less than 0.5 cm, then the metal is forged without heating. If the cross section of the sheets is more than 0.5 cm, then the copper should be forged by heating to a temperature of + 250 ° ... + 350 ° C.

Heating over + 350 ° C is impractical; This leads to a decrease in the strength properties of the metal. At the end of the forging, it is necessary to conduct a thermal annealing operation at a temperature of + 500 ° ... + 600 ° C with further water cooling. This operation allows you to make the weld seam ductile and improve its mechanical and strength properties.

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