Solder for soldering copper: types of solder and their characteristics + tips for choosing

Copper pipes are parts for global or local communication systems transporting gas, water, petroleum products, coolants and other important resources. To combine individual fragments into a single network, copper solder is used. It is selected depending on the conditions under which the system is operated.

A properly designed connection ensures the tightness of the entire complex and prevents leakage of the supplied composition into the environment. And their incorrect connection can result in a lot of problems in the future.

Let's try to understand the types of solder and which one is better to give preference in a particular situation.

What is solder?

Solder is a pure metal or thermoplastic alloy made from several components. Designed to connect copper parts into a common integrated network.

When exposed to high temperatures, the solder melts, spreads across the processing area and seals the surface. After final cooling, a strong, even seam without errors is formed on the pipe material

The technology of joining two fragments, carried out according to this principle, is called soldering.

Among the main advantages of the technique it is worth highlighting:

• connection without deformation;
• preservation of the original shape of the processed parts;
• absence of any internal tension;
• excellent strength and high level of tightness of the created seam;
• resistance of the bonded area to different temperature conditions, including intense heating;
• simple separation of seam sections in case of need to change the system format.

Soldering is carried out with special equipment - a soldering iron, a gas torch or a blowtorch. Immediately before work, the area is thoroughly cleaned of surface defects and technical oils, and only then work begins.

The process of connecting pipe fragments is easy and quick, but requires mandatory compliance with basic safety rules. To avoid problems and injuries, you should wear thick work gloves on your hands, cover your face and eyes with special goggles or a mask, and protect your clothes with a thick apron. This will protect the technician from potential accidents.

For soldering at home, a soldering iron is most often used. A torch or lamp is used where the power capabilities of a soldering iron are not enough or where it is necessary to connect parts of great thickness and impressive mass.

Classification of solders for copper pipes

Solders for high-quality and reliable soldering of copper pipes are made from different components. Products differ from each other in shape and chemical composition.

The type and parameters of the connecting elements are determined by the area of ​​subsequent operation of the pipe system made of copper parts.

Melting point differences

Based on the level of temperature treatment, solders are divided into three types:

• low temperature;
• medium temperature;
• high temperature.

Low temperature variants melt in the range from 150 to 450 °C. They do not change the original physical parameters of the parts.In the connection area, a neat but not too strong seam is created. Intended for use in heating and water supply networks that are not subject to heavy loads.

Ensure the tightness and integrity of pipes with a diameter of up to 10 cm installed in communication systems transporting coolant with temperatures up to 130 °C.

Medium temperature And high temperature materials soften at temperatures ranging from 450 to 1100/1850 °C. They guarantee the most durable, strong connection, not sensitive to external influences.

High-temperature solders are characterized by good reliability and are suitable for use in centralized and private heating systems and gas pipelines. Allows you to make an additional outlet without resorting to dismantling the entire complex

The area connected by medium-temperature or high-temperature solder exhibits resistance to mechanical damage and calmly tolerates active thermal loads.

Separation by chemical composition

According to the chemical composition, modern, practical solders are divided into soft, fusible and hard, refractory.

The first category includes the following items:

• lead – contain only pure lead and melt at temperatures from 180 to 230 °C;
• tin – consist of tin and melt at 220 °C, creating a durable and ductile seam;
• lead-tin – may contain from 15 to 90% tin. The melting temperature of such elements is 183-280 °C;
• tin-copper – 97% made of high-quality tin and 3% copper. They are among the most popular and are sold at a reasonable price. Form a strong connection with good corrosion resistance;
• copper with silver - 95% copper and 5% silver. They are characterized by high strength characteristics and provide reliable adhesion between fragments.

Soft, low-melting components are used to combine pipes with a diameter of 6 to 108 mm into a single complex. In the joint area, a neat seam with a width of 7 to 50 mm is formed.

Soft low-temperature solders are relevant for organizing heating networks, individual and centralized water mains. This option is absolutely not suitable for gas communications.

Lead is considered an element harmful to human health. The use of lead-containing solders is strictly prohibited in networks supplying water to apartment or private buildings, enterprises or public institutions. This prohibition does not apply to other types of communications.

Hard, refractory materials are suitable for high-temperature processing:

• copper combined with silver and zinc – contains 30% copper, 44% silver and 26% zinc. The adhesion area has good strength, retains ductility, effectively resists corrosion and demonstrates increased thermal conductivity;
• copper with phosphorus – an alloy of 94% copper and 6% phosphorus. The soldering process does not require the use of flux. Makes a strong and reliable connection, but partially loses its elasticity at low ambient temperatures;
• silver – during soldering requires the mandatory use of flux. Creates a strong, reliable seam with good ductility and high corrosion resistance. It is much more expensive than analogues made of simple metals and is not widely used.It is used where there is economic feasibility and increased demands are placed on the quality of the pipe connection.

Using refractory solders, complexes of pipes with a diameter of 12 to 159 mm are installed, including gas communication networks, heating lines and water mains with a diameter of 28 mm.

To prevent copper from losing its strength characteristics during the soldering process, you should not immerse the part with a fresh seam in water or subject it to artificial blowing for cooling. A reliable, strong and durable connection will be provided by metal that has cooled naturally

The use of classic copper-phosphorus or any other elements is allowed when creating overlap joints. This coupling option ensures maximum structural strength and increases the operating life of the pipeline.

Soft solders are usually made in the form of coils for ease of use. Solid elements are supplied in the form of wires of different lengths.

To enhance the integrity and increase the strength characteristics of the seam, the overlap should be at least 5 mm. During processing, you need to leave a microscopic gap so that the solder is drawn in evenly, fills the voids and forms a reliable sealed patch

Flux - features and purpose

Flux is a specific technical material for soldering copper pipes. Protects the surface of parts from oxidation and slag. Prevents contact of the welded seam with oxygen. Improves the overall quality of the joint and gives it good strength and optimal ductility.

In the room where copper pipes are sealed, it is necessary to organize high-quality ventilation.It is better to remove combustible and flammable substances in advance so that an accidental spark does not cause a fire or any other incident dangerous to human health.

Fluxes for soldering copper pipes are available in different consistencies.

Among the most sought after and popular:

• paste;
• powder;
• liquid.

Substance in the form soldering paste Copper pipes are more expensive than other materials, but fully justify their high price. Suitable for use immediately after purchase and does not require the technician to add anything to the composition to improve its performance.

The paste is purchased for critical soldering, which requires the most precise and high-quality sealing of the joint areas. The substance easily lies on the copper surface, adheres well to it and is well distributed over the treatment area during heating.

Flux paste is very simple and easy to use. Not only a specialized specialist with extensive practical experience, but also any home craftsman can work with it without any difficulties.

The finished seam looks neat and ensures the integrity of the adhesion of all fragments of the system. Residues of the substance are easily removed after completion of work.

Powder products are sold at a lower price and are stored well in special containers. Maximum efficiency is demonstrated in conjunction with reinforced, refractory solders. They are considered less convenient due to the difficulty of uniform application to the treatment area.

Liquid substances sold in closed bottles. They have normal contact with soft solders and adhere easily to the copper surface, providing high bonding strength.To ensure a high-quality connection, liquid flux and solder are always used simultaneously and not separately.

Regardless of consistency, flux must be applied immediately after stripping the copper fragment. If this moment is ignored, the metal surface will again be covered with oxides and it will not be possible to process it evenly.

After flux treatment, parts should be soldered immediately. This will eliminate the chance of foreign particles penetrating the work surface.

To apply paste-like flux, a special brush with elastic bristles of medium length is required. There is no need to use too much of the substance. This will not affect the quality and strength of the connection in any way.

When connecting parts, care and attention must be exercised. Contact of flux on the skin provokes not only thermal, but also chemical burns.

If this does happen, you should immediately stop soldering and wash the substance off your skin with plenty of soapy water.

Requirements for the quality of fluxes

There are some requirements for fluxes for individual and industrial use.

The substance must meet the following criteria:

• lower structure density and viscosity indicators than solder (for correct replacement);
• ability to distribute evenly over the working surface;
• dissolution of the oxide film;
• prevention of re-oxidation of copper elements;
• resistance to aggressive high temperatures;
• the ability to carry out soldering on both horizontal and vertical sections of the communication system;
• creating a neat, aesthetic seam.

When using good quality fluxes, dust and dirt formed as a result of soldering are removed easily and quickly, without leaving any traces on the pipe element that spoil the appearance. The connection is reliable and maintains structural integrity for many years.

Fluxes based on powders and rosin must be prepared immediately before soldering. The working substance is mixed with anhydrite in a certain portion and immediately applied to the treatment area

Popular types of material

There is a wide range of fluxes for soldering copper pipes on the market.

The most popular substances are:

• with high anti-corrosion ability;
• with noble materials in the composition;
• based on rosin.

Anti-corrosion flux consists of several complex elements, solvents and phosphorus. During the heating process, they dissolve in the liquid, react and form organic components.

Protect the seam area from oxidation and premature corrosion. Promote the drainage of excess moisture from the soldering zone.

The use of flux in the process of soldering copper pipes prevents the formation of pores in the structure of the seam. The connection is solid and does not contain foreign inclusions that reduce the strength of the joint

In the second type of flux, the main active ingredient is salicylic acid. During use, it dissolves in a composition of ethanol, gold-containing substances and industrial petroleum jelly.

Creates a perfectly smooth, neat and aesthetic connecting seam that does not require additional complex processing. Does not damage the material of the pipe adjacent to the treatment area

Classic active flux contains rosin and a certain amount of sodium salt.The substance has pronounced protective characteristics and effectively protects the pipeline from corrosion. Rosin covers the seam with a thin and durable protective film, and sodium salt inhibits oxidative processes.

Mixtures that form acid or contain it initially clean the surface efficiently and remove the oxide layer. To prevent the metal from deteriorating in the future and to retain its basic physical characteristics, the treated area after soldering must be thoroughly washed

This flux is sold for a reasonable price and provides a strong, reliable connection. However, the finished weld remains highly visible and is immediately noticeable on the outer portions of copper piping.

Regardless of the type and basic composition, the flux must be applied as evenly as possible, avoiding even a millimeter gap. If any part of the metal does not have this coating, the pipe will begin to rust over time and will need to be replaced.

The main disadvantage of rosin-based flux is its thermal weakness. It does not tolerate high temperatures well and with constant overheating it becomes charred.

How to choose the right solder?

Correctly selected solder will help you organize a communication system of any complexity without much effort. If we are talking about working at home, it is worth using a material that melts at low temperatures.

The use of high-temperature hard-melting elements in everyday life is problematic, since it requires heating the working alloy to 600-900 degrees. Achieving this without special equipment is quite difficult.

Soldering of edible copper can be carried out using special solders that do not contain toxic, noxious and aggressive elements that can harm health

The use of metals and their derivatives that melt at high temperatures involves some risk. During processing, they can damage or even burn through thin-walled copper pipes.

To prevent this from happening, it makes sense to take strong but low-melting soft solder, and leave the hard option for thick-walled copper communications.

When large loads are not expected on the system, it is not at all necessary to use refractory solder, unless otherwise required. In basic household systems, soft light-alloy solders are sufficient to create a reliable connection.

To connect copper pipes in gas networks, you should choose silver-containing solders. They provide maximum seam strength, vibration neutrality and high resistance to external and internal influences.

You will have to pay a little more for silver, but the safety, reliability and durability of the system will pay off all financial costs over time.

Conclusions and useful video on the topic

The video will talk about how to solder copper pipes:

The following video will discuss which fluxes to choose for soldering copper pipes at home:

Method of soldering copper pipes using soft solder:

Proper use of solder allows you to quickly and easily connect copper pipes into a single system. The finished seam is neat and ensures the tightness of the network of any configuration.

You no longer have to worry about leaking or wasting a valuable resource. The line, combined into an integral complex with the help of high-quality solder, works reliably and lasts a long time, without requiring constant attention or painstaking care from the owners.