Repairing the refrigerant circulation system in the refrigerator is a process that requires not only theoretical knowledge, but also honed practical skills. Soldering copper tubes is a key stage of restoration the tightness of the circuit, on which the efficiency of the entire unit directly depends. Errors at this stage can lead to freon leakage, moisture entering the system, or even failure of an expensive compressor.
Before taking on the burner, you must clearly understand the physical and chemical properties of copper and the consumables used. Copper has high thermal conductivity, which requires rapid and uniform heating of the joint area, but at the same time creates the risk of overheating of neighboring areas. Refrigeration circuit works under high pressure, so the quality of the weld must be impeccable in order to withstand cyclic loads without the formation of microcracks.
In this material we will analyze all the nuances of the process: from the choice correct solder until the final leak test. You will learn why you cannot use regular tin solder and how to avoid the formation of an oxide film inside the tube. The melting point of hard solder is about 600-700 degrees Celsius, which is significantly higher than the boiling point of water, ensuring the strength of the connection.
Required tools and materials for soldering
The quality of the work performed directly depends on what you use. To create a reliable connection, you will need specialized equipment, since a household soldering iron is powerless here. The main tool is gas torchoperating on propane or a mixture of propane and oxygen, which is capable of creating a high-temperature torch.
In addition to the fire source, the correct choice of solder is critically important. Refrigeration systems use refractory alloys, often containing silver, phosphorus or copper. The use of soft lead-tin solders is unacceptable, since they will not withstand the operating pressure and vibration of the compressor. You will also need a pipe cutter, a chamfer and flaring tools.
Don't forget about safety. Working with open fire and gas requires a fire extinguisher, as well as personal protective equipment. Forced or natural ventilation must be organized in the room, since the combustion of flux and heating of the metal can release harmful substances.
- 🔥 Gas burner with a flame regulator for precise temperature adjustment.
- 🔩 Hard solder (silver-containing or copper-phosphorus) in rods or rings.
- 🧪 Soldering flux (borax or specialized compounds) to remove oxides.
- 🛡️ Safety glasses and heat-resistant gloves to prevent burns.
⚠️ Attention: Never use lead-containing solders for repairs refrigerators. Lead is chemically incompatible with modern refrigerants and oils, which can lead to the formation of acids and blockage of the capillary system.
Safety precautions and workplace preparation
Soldering refrigerator pipelines is considered high-risk work. An open flame near flammable materials or electrical wiring insulation may cause a fire. Therefore, the first step should always be thorough preparation of the workplace. Remove all flammable objects, provide free access to the ventilation openings and make sure that the unit being repaired is stable.
Particular attention should be paid to the residual pressure in the system. Before starting any work or heating the tubes, it is necessary to bleed off all the refrigerant. Even if the refrigerator has not been operating for a long time, gas under pressure may remain in the circuit. Sudden heating of a sealed container with gas is guaranteed to lead to an explosion.
When working with a gas burner, keep the container in an upright position and away from the heat source. Hoses must be intact, without cracks or abrasions. If you smell gas, stop working immediately, turn off the valve and ventilate the room.
After ensuring safety it is necessary to prepare the tubes themselves. The copper surface must be perfectly clean. Any contaminants, oil or oxides will prevent the solder from flowing and reduce adhesion. Use fine sandpaper or a special brush to clean the ends of the pipes to a characteristic shine.
Preparing copper tubes for connection
The success of soldering depends 80% on the quality of edge preparation. Copper refrigerator tubes have thin walls, so they are easily damaged by careless handling. For cutting, use only a special one, which gives an even cut without burrs and does not deform the geometry of the pipe. pipe cutter, which gives an even cut without burrs and does not deform the geometry of the pipe.
After cutting, metal shavings often remain on the inner edge. Removing it is a mandatory step. If chips get inside the circuit, it may clog capillary tube or the filter drier, which will cause serious damage to the compressor. Turn the tube over with the hole facing down and tap it on a hard surface to release the remaining metal.
Next you need to remove the chamfer. This is done so that one pipe can easily fit into another with the necessary clearance for the drip effect. The gap should be minimal, but sufficient for solder to flow. The optimal depth of insertion of one pipe into another is from 5 to 10 mm, depending on the diameter.
- ✂️ Cut the tube perpendicular to the axis, avoiding squeezing the walls.
- 🌀 Remove the internal and external chamfer using a rimmer or a needle file.
- 🧹 Clean the joint surfaces to a shine, removing the oxide film.
- 📏 Check the tightness of the fit of the pipes into each other before soldering.
The choice of solder and flux for refrigeration systems
The choice of consumables determines the durability of the repair. For copper-to-copper joints in refrigeration, copper-phosphorus solders are the most common. They have the property of self-fluxing, that is, they do not require the use of aggressive fluxes that could cause corrosion inside the system.
If dissimilar metals are connected, for example, copper and brass (often found in compressor valves), the use of flux becomes mandatory. Flux protects the metal from oxidation when heated and promotes better spreading of molten solder. However, after soldering, flux residues must be carefully removed, as they are hygroscopic and can cause corrosion.
Silver-containing solders are considered a more professional choice. The addition of silver lowers the melting point, improves fluidity and increases the mechanical strength of the weld. Such connections better withstand vibration, which is important for components located near an operating compressor.
| Solder type | Composition | Melting point | Application |
|---|---|---|---|
| Copper-phosphorus | Cu, P | ~700°C | Copper-Copper, Copper-Brass |
| Silver (30%) | Ag, Cu, Zn | ~600°C | Highly loaded units |
| Tin-lead | Sn, Pb | ~180°C | Not used in refrigerators |
| Copper-zinc | Cu, Zn | ~850°C | Steel-Copper (rarely) |
When purchasing materials, pay attention to the diameter of the rod. For thin tubes of household refrigerators, rods with a diameter of 2-3 mm are convenient. A rod that is too thick will be difficult to control, and there is a risk of overheating the soldering zone while waiting for it to melt.
The technological process of soldering copper connections
The soldering process itself requires coordination of movements. You hold the torch with one hand and apply the solder with the other. The burner flame should be adjusted so that it is soft, without a strong whistle. It is not the solder itself that needs to be heated, but the pipe connection. The metal should melt the rod with its heat.
Start heating from the wide part of the connection (fitting or main pipe), gradually moving the torch onto the tube that is being inserted. This ensures even heating. When the metal reaches the desired temperature (it will turn a dark cherry color), touch the solder to the gap. If the temperature is sufficient, the solder itself will flow into the gap under the action of capillary forces.
☑️ Soldering checklist
It is not important overheat the copper. When exposed to excessive heat, copper begins to oxidize, turn black and become brittle. There is also a risk of burning through the thin wall of the tube. If you see that the copper begins to melt or "boil", remove the burner immediately.
⚠️ Attention: Never direct the flame into the tube or onto adjacent insulating materials. The inner walls of the tube oxidize faster, and these oxides will then come off and clog the system.
After the solder has filled the joint, allow the joint to cool naturally. Do not cool it with water or a damp cloth, as sudden changes in temperature may cause cracks in the seam or deformation of the copper. While the solder is liquid, the joint cannot be moved - this will lead to a rupture of the crystal lattice of the metal and the formation of a fistula.
What to do if the solder does not flow into the gap?
If the solder melts from the flame, but does not flow into the joint, it means that the connection itself is not heated enough. Remove the solder and continue heating the pipes, distributing the heat evenly around the perimeter. Often the problem is uneven heating, when one side is cold. Also check if the gap between the pipes is too large.