Soldering is one of the oldest methods of secure fastening of metal parts, which was discovered by chasers from Egypt more than five thousand years ago. The essence of this method is to create a permanent connection of metals using surface diffusion, by filling the seams with solder, which is a fusible material with a melting point much lower than that of the parts to be joined.
An excellent material for work is copper, the surface cleaning of which does not require the use of aggressive substances. Therefore, do-it-yourself copper soldering at home has become widespread when it is necessary to repair household items and various radio engineering devices.
Properties of copper alloys
Copper is the most versatile and affordable material. The positive properties of the metal ensure the widespread use of its alloys in many industries.
These properties include:
- The electrical conductivity of copper is the main quality indicator that determines its widespread use. The electrical conductivity coefficient of copper material exceeds the characteristics of many engineering metals. The addition of alloying elements and impurities to the composition of pure metal reduces its conductivity, but significantly increases strength.
- The thermal conductivity property, like electrical characteristics, also depends on the percentage of impurities in the copper alloy.
- The corrosion resistance of copper is determined by the properties of the surface film, which is insensitive to external influences, and therefore effectively protects the base metal from decomposition. Copper is resistant to organic acids, saline and alkaline solutions, but nitric and inorganic acids can destroy the structure of this metal.
- The ductility of a material during its manufacture or machining (stamping, rolling) can be significantly reduced. This property is easily returned by annealing the metal, that is, heating it to 600-700 degrees, followed by cooling in natural conditions.
- The appearance and color of copper alloys have a characteristic shade that can vary significantly under the influence of weather and atmospheric phenomena. Copper has a specific color from an orange-pink hue to a dark bronze color. Atmospheric influences can cause surface staining up to green. Some copper alloys are widely used for decorative purposes.
I would like to note that the process of connecting a variety of copper wires is not particularly difficult, even for people who do not have experience with a soldering iron. So it's better to stopon soldering metal pipes.
Methods for soldering copper parts
Permanent connection of pipes in industrial enterprises, as well as copper soldering in domestic conditions, is carried out in two ways:
- The high-temperature method is used when connecting copper parts of pipelines operating under heavy load. This method involves melting solder at a temperature of 600-900℃.
- The low temperature method is used for soldering copper at home. The soldering point when using soft solder heats up to 450℃, and when using hard solder requires heating over 450℃.
Soldering technology
The whole process of copper soldering can be conditionally divided into preparatory operations and the stage of joining parts itself. Basic connection operations:
- Quality pipe cutting is easier with a cutter. To do this, it must be installed on the surface to be treated so that the cutting roller exactly coincides with the cut line. With a clamping screw, we press the cutting plane to the product, by turning around the axis of the product, we cut the metal. After two turns, turn the screw to press the cutter against the pipe. Cutting copper can also be done with a conventional hand hacksaw, but it will be very difficult to achieve a perpendicular cut.
- Then you need to remove the inner and outer edges of the part. The inner chamfer is removed to reduce the resistance to gas or water flow, and the outer edge is removed to facilitate the assembly process of the product. Suchoperations can be performed with special tools either built into the cutter or separate devices.
- Next, you need to clean the edges from oxides. Mechanical cleaning of the inside of the pipe is carried out with a special brush, mesh or sandpaper screwed onto the pin. The outer surface is cleaned either with a device with a hole framed with a metal brush or with fine abrasive paper. After cleaning the surface, it is necessary to remove the remaining dust and abrasive, which reduce the quality of copper soldering.
- After removing the debris, you need to apply a flux to the surface, and the paste-like composition is applied with a brush. Next, immediately connect the parts.
- When assembling, the parts are rotated relative to each other so that the flux is completely distributed over the surface, and the elements of the product are fixed in a position convenient for soldering. Excess flux is removed with a cotton rag.
- Before heating the soldering point, remove all rubber and plastic parts that may be damaged by heating.
- The burner flame should be normal. The balanced flame of a copper soldering torch is small and bright blue. The junction must be heated evenly, smoothly moving the flame from all sides of the product. When the optimum melting temperature is reached, the solder begins to spread. After the joints are completely filled with solder, the burner must be taken away from the copper soldering point and allowed to cool down naturally.
- The final step will be to remove the flux residue with a damp cloth soaked in an alcohol solution.
To solder metal at home, in addition to prepared parts, you must have a heating tool, as well as the appropriate flux and solder.
Join heating tools
There are several ways to heat parts to be soldered. The most common are the methods of heating the junction with a soldering iron, gas burner or building hair dryer. The use of these tools is optimal for doing quality work at home.
Using a soldering iron
A soldering iron is a device in which the tip is heated to the required temperature by electrical energy. The selection of the device by power is carried out depending on the thickness of the connected parts.
A soldering iron is mainly used for low temperature soldering. The heating of the metal and solder occurs due to the thermal energy of the tip of the device. The tip is pressed tightly against the junction of the metal, as a result of which it heats up and melts the solder.
Gas burner
The torch is the most versatile type of equipment for heating the soldering place. This category also includes blowtorches that are fueled with kerosene or gasoline.
There are several varieties of copper brazing gas torches from high performance models to home appliances:
- with disposable container;
- using a stationary balloontype;
- oxy-acetylene torches that make up whole units for soldering copper pipes.
By power burners are classified as follows:
- for metal heating and soft soldering (household);
- for work with soft and hard solder (semi-professional);
- for brazing (professional).
The use of a building temperature dryer allows soldering with fusible solder. This tool is capable of blowing hot air up to 650℃.
Varieties of fluxes
For the formation of a high-quality and reliable connecting seam, the use of flux is of great importance. It is a composition that promotes good spreading of solder, while cleaning the surface of the part from oxides and dirt. An important function of the flux is to protect against the ingress of oxygen to the place of soldering, which significantly increases the adhesion of the solder to the metal surface.
According to the content of active substances, the flux for soldering copper can be of the following varieties:
- acid;
- acid-free;
- activated;
- anti-corrosion.
To create a strong bond, the flux must meet several requirements:
- The density and viscosity of the composition should be lower than that of the solder.
- The applied flux, regardless of type, must be evenly distributed over the entire surface of the joint.
- Effectively dissolve the oxide film, preventing its reappearanceon the product.
- The composition should not be destroyed by high temperatures.
- Ability to solder on both horizontal surfaces and vertical joints.
- And, of course, to help create a neat appearance of the connecting seam. The process of soldering copper with silver is most successful when using fluxes, which include potassium and boron fluorides.
Types of solders
As a solder for soldering copper, some pure metals, as well as their alloys, can be used. To create a reliable contact, the solder must wet the base metal well, otherwise it will not be possible to solder.
The melting point of solder is less than that of the metals being joined, but higher than that at which the joint will be strong.
Fusible solders
Fusible (soft) solders are melted up to 450 ℃. This group includes materials consisting of lead and tin in various proportions. Cadmium, bismuth, antimony can be added to give the composition special properties.
Tin-lead solders are not very strong, so they are almost never used when soldering parts with a large load or operating at temperatures above 100 ℃.
Refractory solders
This group includes solders based on silver and copper. Copper-zinc solders are used to join parts with static load because they have a certain brittleness.
The process of soldering copper with brass is carried out using hard copper-phosphorus solder.
Silver types of solders are among the highest quality materials. Such alloys may contain, in addition to silver, zinc and copper. These solders are used for joining workpieces that operate under conditions of shock and vibration.
Unacceptable soldering errors
The reason for the poor-quality connection of two parts is most often haste, so you need to remember to control the edges of the product for the absence of foreign small objects that may form after cutting.
When applying flux, try not to miss even the slightest surface area, because any defect can cause poor contact. If any part of the surface is slightly heated, this will lead to a weak fusion of the two metals. Overheating can cause the flux to burn off and form dross or oxide at the soldering site, affecting solder reliability.
Soldering copper material is not difficult, even for a beginner. The main thing is to strictly observe all technological stages, while not forgetting about safety measures when working with combustible elements.
