Repairing a refrigerator using soldering is a task that requires not only skills in working with a soldering iron, but also the correct choice of consumables. An error in selection solder can lead to repeated leakage of freon, corrosion of connections, or even breakdown of the compressor. In this article, we will look at what types of solder are suitable for different components of the refrigerator, how to use them correctly and what to pay attention to when working with copper, aluminum and steel parts.
The peculiarity of refrigeration equipment is that its systems operate under pressure and under conditions of temperature changes. Therefore ordinary tin-lead solder (for example, POS-61) is not suitable for all tasks. You will need to consider not only the composition of the alloy, but also its melting point, weld strength and refrigerant compatibility. Next is a detailed analysis of each aspect.
Why the correct choice of solder for a refrigerator is important
The refrigeration circuit is a sealed system where freon circulates under pressure up to 15 atmospheres. If the solder cannot withstand the load, the consequences will be critical:
- 🔥 Freon leakage - will lead to loss of cooling capacity and overheating of the compressor.
- ⚡ Short circuit - if the solder contains impurities that conduct current (for example, when soldering electrical contacts).
- 💧 Weld corrosion —poor-quality alloys oxidize, which leads to depressurization after 1–2 years.
- ❄️ Freezing tubes —when using solder with low thermal conductivity.
In addition, some refrigerants (for example, R600a isobutane) react aggressively with copper and its alloys. If you are soldering a system charged with such freon, the solder must contain silver or phosphorus to protect against corrosion. Ignoring this rule reduces the service life of the refrigerator by 2-3 times.
Types of solders for soldering refrigerators: comparative table
All solders for refrigeration equipment are divided into two large groups: soft (melting point up to 450°C) and hard (over 450°C). The former are used for soldering copper tubes, the latter for steel or aluminum parts. Below are the key characteristics of the most common brands.
| Solder grade | Composition | Melting point, °C | Application | Features |
|---|---|---|---|---|
| POS-61 | Tin (61%), lead (39%) | 183–190 | Copper, brass, low-temperature compounds | The most common, but not suitable for high pressures |
| POS-40 | Tin (40%), lead (60%) | 183–238 | Condenser, evaporator tubes | More durable than POS-61, but flows worse |
| PSR-40 | Tin (60%), silver (40%) | 220–250 | Systems with R600a, R290 (propane) | Resistant to corrosion, but expensive |
| LOK-62 | Tin (62%), zinc, aluminum | 250–300 | Aluminum tubes, radiators | Requires fluoroborate-based flux |
| Castolin 192 FBK | Copper, phosphorus, silver | 645–720 | Steel parts, highly loaded seams | Hard solder, soldered with a torch |
Critical important: for systems with R134a refrigerant, you cannot use solders with a copper content of more than 0.1% - this leads to the formation of copper sulfate and clogging of the capillary tube. If you are not sure about the composition of freon, use universal PSr-40 or POS-40.
Which solder to choose for different components of the refrigerator
There is no universal solder for all parts. The choice depends on the material, wall thickness and operating conditions. Let's take a closer look.
1. Copper tubes (condenser, evaporator, capillary tube)
For copper, soft solders based on tin and lead (POS-61, POS-40) or silver-containing alloys (PSR-40) are suitable. Main requirements:
- 🔹 Temperature melting not higher than 300°C (so as not to damage the insulation).
- 🔹 Good fluidity - to fill capillary gaps.
- 🔹 No pores in the seam (use flux F-38N or Borinol).
2. Aluminum parts (radiators, some models of evaporators)
Aluminum is more difficult to solder due to the oxide film. Special solders are needed here (LOK-62, Castolin 190) and active fluxes (F-34A) An alternative is argon welding, but it requires professional equipment.
3. Steel elements (compressor housing, fasteners)
For steel use hard solders (Castolin 192 FBK, LOM-6) or electric arc welding. Soft solders will not provide the required strength. Be sure to clean the seam from slag after soldering!
4. thermostat)
Or lead-free solder ( POS-61 or lead-free solder (Sn96.5Ag3Cu0.5) is suitable here. The main thing is to avoid overheating so as not to damage the plastic housings of the parts.
☑️ Preparation for soldering copper tubes
Soldering technology: step-by-step instructions
Even with Using the right solder can ruin the repair if you violate the technology. Follow this algorithm:
- Surface preparation
Remove the oxide layer mechanically (with sandpaper or a scraper) and degrease with a solvent. For copper, use oxalic acid, for aluminum - orthophosphoric acid.
- Selection of flux
For soft solders: F-38N (for copper), F-34A (for aluminum). solid: borax or fluoroborate fluxes.
- Heating parts
Use a gas torch with a narrow flame or a blowtorch. The temperature should be 50–100°C above the melting point of the solder.
- Applying solder
Touch the rod to the heated part, and not to the flame! Solder should spread under the action of capillary forces.
- Cooling and cleaning
Allow the seam to cool naturally. Remove any remaining flux with water or a special solution (for example, Flusoff).
Important nuance: When soldering tubes with freon, first bleed off the gas (in a well-ventilated area!), and then purge the system with nitrogen. This will prevent oxidation and explosion when heated.
What to do if the solder does not stick?
If the solder rolls up into balls, it means the surface is oxidized or not heated enough. Try:
1. Repeat cleaning and degreasing.
2. Increase the heating temperature (but do not overheat!).
3. Change the flux to a more active one (for example, F-64 for copper).
4. Check the composition of the solder - perhaps it is of poor quality or expired.
Top 5 mistakes when soldering a refrigerator and how to avoid them
Even experienced craftsmen sometimes make mistakes that negate the entire repair. Here are the most common:
- Overheating of tubes
At temperatures above 350°C, copper loses strength and the insulation melts. Use thermocouples or an infrared thermometer for control.
- Using acid flux for aluminum
Acids corrode aluminum and lead to leaks. Use only fluoroborate-based fluxes.
- Pressure soldering
If there is freon left in the system, it will expand when heated and can rupture the tube. Always bleed off the gas before repairs!
- Saving on solder
Cheap alloys with a high lead content (POS-90) produce brittle seams. This is unacceptable for refrigerators.
- Ignoring the leak test
After soldering, be sure to check the seam with a soap solution or a leak detector. The pressure in the system must be maintained for at least 24 hours.
Safety when soldering: what not to do
Refrigerator repairs are associated with risks of poisoning, fire and injury. Follow these rules:
⚠️ Attention: Never solder a refrigerator connected to the network! Even if the compressor is turned off, voltage up to 300 V can remain on the capacitors.
- 🔥 Do not work in enclosed spaces —freon and flux vapors are toxic. Use a hood or respirator.
- 💨 Do not point the burner flame at plastic parts —they may ignite or emit toxic smoke.
- 🧤 Do not touch heated parts with bare hands —the temperature of the tubes may exceed 200°C.
- 🚫 Do not use water to cool the seam - this causes microcracks in the metal.
If you are soldering a system with freon R600a (isobutane), remember: it is heavier than air and accumulates at the bottom. If there is a leak, it can explode from a spark! Work only with open windows and away from sources of fire.
⚠️ Attention: Some refrigerator models (for example Liebert, Thermoking) use special alloys for tubes. Before soldering, check their composition in the technical documentation - standard solders may not be suitable.
FAQ: Frequently asked questions about soldering refrigerators
Is it possible to solder a refrigerator with a regular soldering iron?
For small jobs (for example, soldering thermostat contacts) a soldering iron with a power of 40–60 W is suitable. But for soldering tubes you need gas torch or blowtorch a soldering iron will not provide the required temperature.
Which solder is better: POS-61 or POS-40?
POS-40 stronger and suitable for systems with pressures up to 20 atm, but spreads worse. POS-61 more convenient for beginners, but does not withstand high loads. For refrigerators it is optimal POS-40 or PSR-40 (if the system is filled with R600a).
What is the danger of soldering aluminum?
Aluminum quickly oxidizes, and its oxide film prevents adhesion to the solder. Without a special flux (F-34A) and proper preparation, the seam will be fragile. In addition, aluminum. melts at 660°C - overheating leads to deformation of parts.
Is it necessary to flush the system after soldering?
Yes! Flux residues cause corrosion. Rinse the system acetone or with a special solution. (Flusoff), then blow with nitrogen. This will remove moisture and oxides.
How much does solder cost for a refrigerator?
Prices depend. from composition:
- POS-61/POS-40: 300–500 rub/kg.
- PSR-40 (silver): 1500–2500 rub/kg.
- Castolin 192 FBK (solid): 3000–5000 rub/kg.
- LOK-62 (for aluminum): 800–1200 rub/kg.
For a one-time repair, 50–100 g of solder is enough.