Soldering is one of the oldest ways to securely fasten metal parts, which was discovered by Egyptian masons more than five thousand years ago. The essence of this method is to create an inseparable compound of metals using surface diffusion, by filling the joints with solder, which is a low-melting material with a melting point much lower than that of the parts to be joined.
An excellent material for work is copper, the cleaning of the surface of which does not require the use of aggressive substances. Therefore, soldering copper at home with their own hands was widespread when it was necessary to repair household items and various radio engineering devices.
Copper Alloy Properties
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 conductivity coefficient of a copper material exceeds the characteristics of many engineering metals. The addition of alloying elements and impurities to the composition of a pure metal reduces its conductivity, but significantly increases its strength.
- The property of thermal conductivity, as well as 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, salt and alkaline solutions, but nitric and inorganic acids can destroy the structure of this metal.
- The ductility of the 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 600â700 degrees, followed by cooling in natural conditions.
- The appearance and color of copper alloys have a characteristic shade, which can significantly change under the influence of weather and atmospheric phenomena. Copper has a specific color from orange-pink to dark bronze. Atmospheric effects can provoke 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 does not cause much difficulty, even for people who do not have experience with a soldering iron. Therefore, it will be more useful to dwell on the soldering of metal pipes.
Methods for soldering copper parts
The permanent connection of pipes at 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 the melting of solder at a temperature of 600â900 â.
- The low-temperature method is used for soldering copper at home. When using a soft solder, the soldering point heats up to 450 â, and the use of solid solder requires heating above 450 â.
Soldering technology
The whole process of brazing copper can be divided into preparatory operations and directly the stage of joining parts. Basic connection operations:
- High-quality pipe cutting is easier to do with a cutter. To do this, it must be installed on the surface to be machined so that the cutting roller exactly matches the cut line. Clamping the cutting plane with the clamping screw to the product, turning around the product axis we cut the metal. After two revolutions, by turning the screw, we press the torch to the pipe. Copper can be trimmed with a conventional metal 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 resistance to the flow of gas or water, and the outer edge is removed to facilitate the assembly process of the product. Such operations can be performed by special devices, both built into the cutter, and by individual devices.
- Next, you need to clean the edges of oxides. Mechanical cleaning of the inside of the pipe is carried out with a special brush, mesh or sandpaper, screwed onto the pin. The external surface is cleaned either with a device with an opening framed by a metal brush or with fine abrasive paper. After cleaning the surface, it is necessary to remove residual dust and abrasive, which reduce the quality of brazing of copper.
- After removing debris, it is necessary to apply a flux to the surface, and the paste-like composition is applied with a brush. Next, we immediately connect the details.
- During assembly, the parts are turned 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 cloth.
- Before heating the soldering place, remove all rubber and plastic elements that may be damaged by heating.
- Burner flame must be normal. The balanced flame of a copper brazed burner is small and bright blue. The joint must be heated evenly, smoothly moving the flame from all sides of the product. When the optimum melting point is reached, the solder begins to blur. After the joints are completely filled with solder, the burner must be taken away from the place of brazing of copper and allowed to allow the joint to cool naturally.
- The final step will be the removal of flux residues with a damp rag soaked in an alcohol solution.
In order to solder metal at home, in addition to prepared parts, it is necessary to have a tool for heating, as well as the corresponding flux and solder.
Tools for heating the junction
There are several ways to heat soldered parts. The most common are methods of heating the junction with a soldering iron, gas burner or hair dryer. The use of these tools is optimal for conducting quality work at home.
Soldering iron application
A soldering iron is a device in which the tip is heated to the required temperature under the influence of electrical energy. The selection of the device for power is carried out depending on the thickness of the connected parts.
A soldering iron is used mainly for low-temperature soldering. Heating of metal and solder occurs due to the thermal energy of the tip of the device. The tip is pressed tightly to the junction of the metal, resulting in its heating and melting of the solder.
Gas-burner
The burner is the most versatile type of equipment for heating the place of soldering. This category also includes blowtorches that are refueled with kerosene or gasoline.
There are several types of gas burners for brazing copper from high-performance models to household appliances:
- with a disposable container;
- using a stationary type balloon;
- acetylene-oxygen burners, which make up the whole units for soldering copper pipes.
By power, burners are classified as follows:
- for heating metal and soldering with soft solder (household);
- for work with soft and hard solder (semi-professional);
- for soldering (professional).
The use of a building heat gun allows soldering with fusible solder. This tool is capable of emitting a stream of hot air up to 650 â.
Varieties of fluxes
The use of flux is of great importance for the formation of a high-quality and reliable joint. 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 protection against oxygen ingress to the soldering point, which significantly increases the adhesion of the solder to the metal surface.
According to the content of active substances, flux for brazing copper can be of the following varieties:
- acidic;
- acid free;
- activated;
- anticorrosive.
To create a strong connection, 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, should be evenly distributed over the entire surface of the joint.
- Effectively dissolve the oxide film, preventing its re-appearance on the product.
- The destruction of the composition under the influence of high temperatures should not occur.
- The ability to solder both on horizontal surfaces and on vertical joints.
- And of course, contribute to the creation of a neat appearance of the connecting seam. The process of brazing copper silver is most successful when using fluxes, which include fluoride compounds of potassium and boron.
Types of Solders
As solder for brazing copper, some pure metals, as well as their alloys, can be used. To create a reliable contact, the solder should moisten the base metal well, otherwise it is impossible to solder.
The melting point of the solder is less than the same index of the metals being joined, but higher than that at which the joint will be strong.
Fusible solders
Melting of fusible (soft) solders occurs up to 450 â. 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 durable, therefore, they are almost not used when soldering parts with a high load or operated at a temperature of more than 100 â.
Refractory Solders
This group includes solders based on silver and copper. Copper-zinc solders are used to connect parts with a static load, because they have a certain fragility.
The process of brazing copper with brass is carried out using solid 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 work under shock and vibration conditions.
Invalid soldering errors
The reason for the poor-quality connection of the two parts is often rushing, so you should not forget to control the edges of the product for the absence of extraneous small objects that may form after cutting.
When applying flux, try not to miss a single smallest part of the surface, because any defect can cause poor contact. If any part of the surface is slightly warmed up, this will lead to weak fusion of the two metals. Overheating can lead to combustion of the flux and the formation of scale or oxide at the place of soldering, which affects its reliability.
Soldering copper material is not particularly 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.