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How to solder copper with a gas torch

How to solder copper elements: general information

The most common problem is the need to solder twisted copper wires. But no matter what metals you solder, it is always necessary to clean the surfaces from grease and oxide. This is done with rosin, copper pipe solder paste or soldering acid.

In order to ensure that the elements are soldered firmly, it is recommended that they are first treated individually with flux, then tinned. to apply a thin layer of solder to their surfaces. Then they can be joined together and, after adding a little solder, you heat them thoroughly. The tin will melt and join the pieces as tightly as possible.

solder, copper, torch

In some cases a gas torch is used instead of a soldering iron. This is used if the soldered parts are too big. In these cases, even the most powerful soldering iron is not able to heat them, which means that you can forget about a strong connection. The torch heats them more thoroughly.

Peculiarities of working with soft solder

With the help of low-temperature method produces installation of water pipes and heating systems, as well as soldering tubes of air conditioners and refrigerators, the temperature of the environment which does not exceed 130 degrees. You can join pipes with the cross section of not more than 10 cm in this way. In the course of work copper products are rolled, cleaned, treated with flux and inserted into each other. Connecting section should be heated to 200-250 degrees, with a further application of solder on the junction edges.

Using a torch, it is important not to overdo it, because its temperature sometimes rises up to 1000 degrees. Therefore, it is recommended to heat the bonded surfaces in series for 15-20 seconds by constantly moving the flame. The reference point for the heating level is usually the color of the flux (it should darken). Next, the soft solder is introduced into the work area: in contact with the copper base melts and the tin flows over the flux into the seam. It is necessary to achieve complete filling of the space from the socket to the pipe with heated material.

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Soldering methods

There are three basic methods of soldering the heat exchanger in the gas heater. They differ in the tools you use.

Using a soldering iron

In this case, you need a good soldering iron, more than 100W of power, solder and flux.

First of all, flux is applied to the soldering place. a special paste, rosin or aspirin. This component allows to clean the surface from oxide, so that the solder is distributed more evenly.

Next, the copper tube is heated with a soldering iron and the solder is gradually applied to it. It is desirable that the solder melts from the hot surface of the pipe, not in contact with the soldering iron.

The soldering layer should reach 1-2 mm so that the soldering point can withstand the pressure of the heat carrier in the circuit.

Gas torch

To braze holes in the heat exchanger in this way you need a torch, a cylinder with liquid gas, solder and flux. After connecting the burner it is lit, adjust the intensity of the flame. it should not be high, so as not to damage the coolant elements of the gas boiler during soldering.

Dry out the fistula in the copper pipe with a torch to remove any residual moisture. Apply flux (usually borax powder). Then begin to gradually heat the pipe itself so that the solder that is applied next begins to melt.

After the flux is done, remove it thoroughly so that it does not corrode the surface of the heat exchanger tube.

Cold welding

When using the chemical method of soldering with cold welding, it is desirable to use a material that will retain strength and will not melt in contact with hot water. Otherwise, a fistula will reappear in the plate solder heat exchanger, and you will have to start over.

When working with cold welding gloves are required to protect the hands. A little substance should be kneaded in your hands for about 3 minutes. When the weld begins to cure the patch is placed on the leak and pressed on until it is completely cured.

solder, copper, torch

In cases where the heat exchanger is leaking in several places at once, or the fissures are very large, it is desirable to solder a patch of copper plate or a piece of copper tube.

Soldering iron

The main difficulty in working with brass, unlike other non-ferrous metals soldering torch or soldering iron, is the oxide film that is formed by the evaporation of zinc after heating the brass.

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To solder this alloy with a soldering iron, you need a quality unit with a power of at least 1000 watts. This requirement is due to the high melting point of the brass and the solder used. The exception is copper brass alloys whose melting point is much lower.

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A soldering station with temperature control is considered the best choice. The use of such equipment allows you to easily select the optimal working parameters without the risk of overheating the surface.

High-temperature bonding

Choosing this method and determining what to solder copper, the master heats the parts also with a gas burner. It also moves all around the joint. Even and fast movements are performed.

The technician heats until the surface is a dark cherry color. This indicates that the parts have cracked to a temperature of 750°. After that the solder is applied.

Once the entire gap has been filled, leave the joint untouched until it has cooled down completely. Then the joint is wiped clean with a rag.

Soldering copper tubes with a gas torch (instructions)

Working with a gas torch and molten solder will make anyone nervous, whether a beginner or a professional. An important point: the consequences of soldering errors practically range from a leaky pipe seam to a real house fire. However, as with most practiced crafts, the key to successfully brazing copper tubing with a gas torch is practice and planning.

Brazing mistakes

Beginning craftsmen who are inexperienced in joining copper tubing may make the following mistakes:

solder, copper, torch
  • Poor heating. Inexperienced users are afraid of overheating copper parts, which leads to poorly heated surfaces. The result is a low-strength joint that will break under the slightest load.
  • Overheating. The opposite situation, which threatens to burn off the flux from the surface. Contact elements without protection will be covered with scale, which negatively affects the quality of the connection.

To develop the necessary skills, it is recommended to do a test soldering on unwanted pipe scraps.

The soldering iron is used only for joining small parts, and the soldering process is performed at 350 ℃. Large workpieces, because of their increased thermal conductivity, should only be soldered with burners.

As for baths and furnaces, there are two positions that differ from each other in the filler. This can be solder or salt. It should be noted that the salts perform two functions: a heating element as source of temperature, and a flux.

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That is, in technologies where salt furnaces or baths are used, fluxes are not used.

In principle, regardless of the metal of the workpieces, the joining process is the same for all materials. And it is divided into six steps:

    Cleaning of copper billets by mechanical means to remove the oxide film;

  • degreasing;
  • the introduction of flux into the soldering zone;
  • Heating the area.
  • introduction of solder;
  • Cleaning the joint from flux and solder material.

Soldering of bronze is also done. The main difference is the necessary brand of solder and flux. Since bronzes are an alloy of copper, tin, and some other elements, the choice of solder is easy.

Bronzes also include alloys of copper and cadmium, copper and beryllium, alloys with lead, aluminum. It is necessary to pay attention to the composition of the bronze, depending on which changes the properties of the material.

Soldering with powder flux

Another way to neutralize the oxide film (Al2O3), is to use powder fluxes when brazing copper with aluminum. In these cases, a gas torch is most often used, and the powders are called solder powders. Probably someone represents to itself soldering as work with the soldering iron, but it is not quite so, after all for wires of section of 10 mm2 and more the soldering iron is simply unsuitable, as can not heat them up properly. Therefore, powder fluxes should not be discounted.

Here are some of the powdered fluxes (powder fluxes):

  • Sodium salt of boric acid, also known as borax (Na₂[B₄O₅(OH)₄]-8H₂O), is a white powder with a melting point of 700°C (the solid becomes viscous). Such flux is inexpensive, dissolves in water, and washes off well with citric acid solution.
  • Активный флюс Ф34-A. Согласно ТУ 48-4-229-87 состоит на 50% из хлорида калия (KCl), на 8% из хлорида цинка (ZnCl₂), на 32% из хлорида лития (LiCl) и на 10% из фторида натрия (NaF). Данная субстанция гигроскопична и хорошо растворяется в воде.

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Kerariel

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