Hello my dear readers! I became interested in aluminum soldering about 5 years ago, when I urgently had to solder the cooling radiator of my Grasshopper. Below I will show a photo of it and the place of soldering on the radiator, which is still working. Recently I was asked what is the best way to solder aluminum? I decided to read all the relevant articles and personal opinions on aluminum soldering and put it on one page. This is how this article was born. Go!
Why is aluminum difficult to solder?
Anyone who has tried to solder aluminum knows that ordinary solder does not stick to it at all. This is all due to a stable film of aluminum oxide, which has poor adhesion to solder. Moreover, this film covers aluminum and its alloys very quickly. Before you have time to clean it, the light metal has already oxidized. Therefore, all methods of aluminum soldering first deal with the film, and then take care of adhesion.
Aluminum oxide (Al 2 O 3) in mineralogy is called corundum. Large transparent corundum crystals are gemstones. Due to impurities, corundum comes in different colors: red corundum (containing chromium impurities) is called ruby, and blue corundum is called sapphire. Now it is clear why the oxide film does not solder at all.
How to remove oxide film?
The aluminum oxide film is removed in two ways: mechanical and chemical. Both methods remove aluminum oxide in an airless environment, that is, without access to oxygen. Let's start with the most difficult, but most correct and reliable method of removal - chemical.
Precipitate copper or zinc
The chemical soldering method is based on the preliminary deposition of copper or zinc onto aluminum by electrolysis. To do this, apply a concentrated solution of copper sulfate to the desired location and connect the negative of the battery or laboratory power source in a free place. Then take a piece of copper (zinc) wire, connect a plus to it and immerse it in the solution.
Through the process of electrolysis, copper (zinc) is deposited onto the aluminum and adheres to it at a molecular level. Then aluminum is soldered on top of the copper. True, it is not clear how all this passes through the oxide barrier. I think that this instruction skips the step of scratching aluminum under a film of copper sulfate or other chemical exposure. Although the practice from the video below shows that you don’t have to scratch.
After deposition, copper or zinc can be processed without problems using standard fluxes. It seems to me that this method makes sense to be used on an industrial scale and for particularly critical work.Use oil without water
The second most difficult method is to remove aluminum oxide. In this case, the oil should contain a minimum of water - transformer or synthetic oil will do. You can hold the oil at a temperature of 150 - 200 degrees for several minutes so that the water evaporates from it and it does not splash when heated.
Under the oil film, you also need to remove the oxide. You can rub it with sandpaper, scratch it with a scalpel, or use a serrated tip. When I needed to solder the engine cooling radiator, I used the chip method. We take a nail, saw it with a file to get steel shavings.
Next, apply oil to the soldering area and sprinkle chips. Using a soldering iron with a wide tip, we try to rub the soldering area so that there are shavings between the tip and the aluminum. In the case of a massive radiator, I additionally heated the tinning area.
Then we take a drop of solder onto the tip, immerse it in oil at the soldering site and rub it again. For better tinning, you can add rosin or other flux. The so-called surfacing under a layer of flux occurs. The video shows a good example of soldering aluminum with oil.
Solder with active flux
There are separately developed active fluxes for soldering aluminum. They usually contain acids (orthophosphoric acid, acetylsalicylic acid) and salts (sodium salt of boric acid). Strictly speaking, rosin also consists of organic acids, but in practice it gives a weak result on aluminum.
Due to their activity, acid fluxes must be washed off after soldering. After the first wash, you can additionally neutralize the acid with alkali (soda solution) and wash it a second time.
Active fluxes give good and quick results, but inhaling the vapors of this flux is strictly prohibited. Vapors irritate mucous membranes, damage them, or can enter the bloodstream through the respiratory tract.
Fluxes for aluminum soldering
Let's look at all the common fluxes for soldering aluminum.
Rosin
Liquid fluxes are good because they can be applied in a thin layer. They evaporate more actively and often have scalding vapors. More suitable for soldering with a soldering iron.
- Flux F-64 contains tetraethylammonium, fluorides, deionized water, wetting additives and corrosion inhibitors . It is capable of destroying a strong oxide film of considerable thickness, which means it is suitable for soldering large workpieces. Suitable for soldering aluminum, galvanized iron, copper, beryllium bronze, etc.
- Flux F-61 contains triethanolamine, zinc fluoroborate, ammonium fluoroborate. It can be recommended for low-temperature soldering at 250 degrees or tinning of products made of aluminum alloys.
- Castolin Alutin 51 L contains 32% tin, lead and cadmium. This composition works best when using solders from the same manufacturer at temperatures of 160 degrees and above.
- There are also, but I won’t list them - they should all be equally good.
Solder for soldering aluminum
Solder HTS-2000
This is the most advertised solder. Soldering aluminum with it is very simple. Watch the promotional video about soldering HTS-2000 from New Technology Products (USA). They say it is even better and stronger than aluminum. But it is not exactly.
And here is the real experience of soldering with HTS-2000 solder. The solder doesn't stick well at first, but then it seems to work. A pressure test showed that the soldering area was etching. There is an opinion that HTS-2000 should only be soldered with flux. Draw your own conclusions.Castolin solder
Solder Castolin 192FBK consists of aluminum 2% and zinc 97%. 192FBK is practically the only solder for soldering aluminum to aluminum in the list of offers of the French company Castolin. There is also AluFlam solder 190, but it is designed for capillary soldering and does not have flux inside. The line also includes Castolin 1827 solder, designed for soldering aluminum with copper at a temperature of about 280 degrees.
Castolin 192fbk tubular solder contains flux in the core, so you can solder without the recommended Castolin Alutin 51 L liquid flux. The video below shows the soldering process. Good solder - you can buy it for 100 - 150 rubles. per rod weighing 10 grams.
Solder Chemet
Solder Chemet Aluminum 13 used for welding aluminum and its alloys with a melting point above 640 degrees. It consists of 87% aluminum and 13% silicon. The solder itself melts at a temperature of about 600 degrees. Cost - about 500 rubles. for 100 grams, in which there are as many as 25 rods.
Its older brother Chemet Aluminum 13-UF has flux inside the tube, but costs more - 700 rubles. for 100 grams and 12 rods.
I didn’t find any sane videos on soldering with this solder. Of course, this list of solders is not exhaustive. There are also Harris-52, Al-220, POTs-80, etc.
Domestic solders
- . Why not? When I was soldering an aluminum radiator, this was the only one I had on hand. And it has held up well for 5 years.
- Aluminum solder 34A- for soldering with a gas-flame torch, in a furnace in a vacuum or with immersion in a melt of aluminum salts and its alloys, except for D16 and containing > 3% Mg. Melts at 525 degrees. Solders aluminum alloys AMts, AMg2, AM3M well. For 100 grams you will have to pay about 700 rubles.
- Solder grade A— manufactured in accordance with TU 48-21-71-89 and consists of 60% zinc, 36% tin and 2% copper. Melts at a temperature of 425 °C. 1 rod weighs about 145 grams and costs about 400 rubles.
- SUPER A+ used with SUPER FA flux and manufactured in Novosibirsk. Positioned as an analogue of HTS-2000. For 100 grams of solder they ask for about 800 rubles. There are no reviews yet.
Comparison of solders for aluminum soldering
In this video, the Master compared HTS-2000 solder with Castolin 192fbk and domestic aluminum solder “Aluminum Cucumber”. The cucumber is practically made of aluminum, so its strength is high, but it must be soldered in a stove. Reviews of HTS-200 solder are extremely negative, but Castolin 192fbk solders well and has good wettability when heated.
Another Master compared HTS 2000 with Fontargen F 400M flux and Castolin 192FBK solder.The results are:
- HTS 2000- solder is malleable, you have to resort to steel tools to level the solder over the metal surface. The situation with flux is much better.
- Castolyn 192FBK- high fluidity and wicking. Small holes are soldered with it quickly. It is difficult for them to solder large holes - it may fall inside the radiator.
Cored wire
Flux cored wire - needed for welding aluminum, not for soldering. Don't confuse these two concepts. The advantage of this wire is welding without the use of gas. This is electric welding for aluminum. An interesting thing, but expensive. I'll show you a good video about flux-cored wire welding.
Soldering iron for soldering aluminum
Soldering aluminum using a soldering iron must take into account the area of the parts being soldered. Aluminum, like copper, is a good conductor of heat, which means more heat should come from the soldering iron than the parts being soldered dissipate.
An approximate calculation is 1000 sq. cm aluminum can effectively dissipate about 50 W of thermal power. It turns out to solder two parts with a total area of 1000 square meters. cm, you need to take at least. Then soldering aluminum will be fast enough so as not to turn into torture.
You can also solder with a low-power soldering iron. For example, when I soldered the radiator of my Grasshopper with a 60 W soldering iron, a hot-air soldering station helped me, which acted as a heater.
Aluminum soldering torches
When the power of the soldering iron and heating are not enough to solder, for example, thick aluminum sheets, then they come to the rescue.
I have already written a separate article about burners -. The power and size of the burner nozzle also depends on the areas that need to be heated. The advantage of the heating pad is the contactless delivery of heat and high heating speed. Often the edges of the workpiece do not have time to heat up, and the joint is already soldered.
Observe safety precautions when working with burners!
Here's what you can do with a simple canister torch.
What is better - welding or soldering aluminum?
The debate over the answer to this question is not going to subside. It turns out it all depends on your purpose. More precisely, the purpose of your connected parts.
If you need to solder a car radiator, then soldering aluminum is better suited because it is cheaper. For critical work (load-bearing structures) and food containers (for example, a milk flask), welding is better suited because it is more reliable. This is how I would formulate the answer to this question.
It is clear that it is easier for a master with gas welding to weld a radiator, rather than solder it, and vice versa - it is easier for a master with a soldering iron to solder.
Now look at TIG welding for beginners. Very helpful and well filmed.
How to make money soldering aluminum?
And now the most interesting thing is how and how much to earn from soldering aluminum. I opened Avito and searched cost of aluminum soldering work. Here's what happened:
- soldering of a car radiator, refrigerator, air conditioner - from 1000 rubles.
- soldering of electrical wiring - 15 rubles. for soldering.
- repair of bicycle frames - from 500 rubles.
- soldering of aluminum for food, for example, pans - from 100 rubles.
Expenses:
- Gas cartridge with burner 700 - 1000 rubles.
- Solder Castolin 192FBK - 150 rub. per bar * 5 = 750 rub.
- Training radiator - free or for 500 rubles. in scrap metal.
- Desire is priceless!
Business plan:
- Spend 2000 rubles. for tools and experience
- Recover the costs for 2 repairs.
- There will still be at least 3-4 repairs left.
- Profitability 200 - 300%!
And now what was promised. This is what my radiator looked like.
At this point, the fan casing bent due to heat and began to rub against the radiator. Three holes formed through which antifreeze leaked. I remember this night. It's good that it was within the city limits.
In the entire Rostov region I saw only one such machine. Once in the city of Kamensk-Shakhtinsky, she and I stood at a traffic light one behind the other. It looked funny.
That's all. I hope that now soldering aluminum is not something special for you. Master Soldering worked for you. What do you use to solder aluminum?
Currently, aluminum and its alloys have become widely used in electrical appliances, such as aluminum electrical wires, etc. Since aluminum and its alloys quickly oxidize in contact with air, conventional soldering methods do not give satisfactory results. Below we describe various methods of soldering aluminum at home using tin-lead solders POS-61, POS-50, POS-90.
1. To solder two aluminum wires, they are pre-tinned. To do this, the end of the wire is coated with rosin, placed on sandpaper (with medium grain) and pressed against the sandpaper with a hot tinned soldering iron, while the soldering iron is not removed from the wire and rosin is constantly added to the desired end. The wire is tinned well, but all operations have to be repeated many times. Then soldering proceeds in the usual manner. The best results are obtained if, instead of rosin, you use mineral oil for sewing machines or alkaline oil (for cleaning weapons after shooting).
2. Soldering of sheet aluminum or its alloys is carried out as follows: rosin with fine iron filings is applied to the seam with a hot soldering iron. The soldering iron is tinned, and they begin to wipe the seam area with it, adding solder all the time. Sawdust, with its sharp edges, removes oxide from the surface, and the tin firmly adheres to the aluminum. Solder with a well-heated soldering iron. For soldering thin aluminum, a soldering iron power of 50 W is sufficient; for aluminum with a thickness of 1 mm or more, a power of 90 W is desirable; if the thickness is more than 2 mm, the soldering area must be heated with a soldering iron and only then apply flux and solder. Here, mineral oil can also be successfully used as a flux.
3. An original method of soldering aluminum wires and aluminum surfaces. Before soldering, the aluminum surface of the aluminum part is pre-copper-plated using the simple electroplating setup described earlier. But it can be made simpler.
—
+
Rice. 1
To do this, take a thick brush for watercolor paints, and its metal rim, touching the hairs, is wrapped with bare copper wire (Fig. 1). The other end of the wire is connected to the positive terminal of a DC source (rectifier, flashlight battery, or rechargeable battery). The aluminum part is connected to the negative pole. The soldering area is cleaned with sandpaper. When starting to coat the part, you need to thoroughly moisten the brush in a saturated solution of copper sulfate and move it over the part, as when painting. After some time, a layer of red copper settles on the surface of the aluminum part, which, after washing and drying, is tinned in the usual way (with a soldering iron).
Note. In industry and repair practice, solders of the P150A, P250A and P300A brands are used for soldering mounting elements made of aluminum and its alloys, as well as connecting them with copper and other metals. Soldering is carried out with a conventional soldering iron, the tip of which is heated to a temperature of 350 ° C, using a flux that is a mixture of oleic acid and lithium iodide.
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- Stages of tinning
- Tinning of aluminum wires
To obtain a reliable connection when soldering with tin-lead solder, it is necessary to strip and tin the wires.
If you neglect these steps, it is unlikely that the soldering will be of high quality and durable.
First of all, you should prepare the soldering iron and, if necessary, carry out its maintenance: remove scale with a knife, clean the soldering iron tip using a fine-grained emery wheel or using a needle file.
Before starting soldering, the soldering iron must be warmed up to operating temperature. Then you should dip the tip into rosin, touch solid tin or tin-lead
If a thin shiny layer of solder has formed on the soldering iron tip (and not a hanging drop), you can proceed to further work.
All metals in the air oxidize. Their surface is covered with an oxide film, which prevents the metal from being wetted by molten solder. Therefore, all soldered surfaces must be cleaned to a metallic shine with a knife or fine sandpaper; additionally, they can be degreased with solvents.
Use a soldering iron to heat the wire, apply rosin to it, and rub solder into it with leisurely movements.
If the entire section of the conductor is evenly
digging with solder, tinning can be stopped.
Tinning copper wires does not cause any particular problems. Even novice soldering workers can handle this job. But not all craftsmen know how to tin an aluminum wire.
It is difficult to solder aluminum wire at home; many craftsmen do not undertake such work.
How to solder aluminum
The problem is that if the oxide film is removed, the aluminum in the air almost instantly oxidizes and the film is restored. But with patience, you can get a fairly high-quality solder.
- prepare flux by dissolving rosin in diethyl ether;
- prepare steel filings;
- strip the wire in the usual way;
- immediately apply flux to the wire;
- sprinkle the soldering area with metal filings;
- Tin carefully by rubbing solder into the aluminum.
Metal filings play the role of abrasive particles and constantly destroy the resulting oxide film.
As necessary, they should be poured onto the adhesion site.
This method does not always guarantee the achievement of the desired result. The contact between the soldered wires may be of poor quality and short-lived.
Professionals prefer to use special solders and fluxes. In this case, the soldered wire should be heated not with a soldering iron, but with a gas torch or blowtorch. The heating temperature of the solder and tinned wire must be at least 600°C.
Another simple way to tin aluminum wires using copper wires.
It is based on the phenomenon of electrolysis. To do this, you need to stock up on a concentrated solution of copper sulfate and a direct current source with a power of at least 10 W. Apply a few drops of copper sulfate to the cleaned aluminum at the soldering site and wrap it with several turns of copper wire.
An aluminum conductor is connected to the negative pole of the current source, and a copper conductor is connected to the positive pole. An electric current arises in the circuit, electrolysis occurs, and the aluminum conductor is coated with a thin layer of copper. A layer tinned with copper is formed on the aluminum conductor. This method cannot be used for tinning massive parts, but it is quite suitable for soldering thin conductors.
If copper sulfate is not available, it can be replaced with hydrochloric acid.
In the place of intended soldering, you need to move the copper conductor with pressure. Electrolysis in this case proceeds more efficiently. But you need to remember that the soldering area using acid oxidizes over time, so after finishing work it must be washed with clean water or a weak alkali solution.
Leather - Aluminum
The aluminum mold is not used to facilitate soldering and is produced after zinc treatment of the product and.
For soldering and tinning aluminum, use an ultrasonic soldering iron.
Aluminum in the air is known to quickly become covered with a layer of oxide film, which prevents the solder from bonding to the metal. Under the influence of ultrasound, the oxide film is destroyed and removed from the aluminum surface.
Aluminum is especially difficult to harden. Ultrasonic quenching, used for narrow seam soldering, is not suitable for thinning large surfaces such as aluminum tires.
At the Dynamo plant they developed a method for abrasive and abrasive crystal parts of aluminum tires.
Aluminum is especially difficult to clean. Ultrasonic hardening, used for soldering narrow gauges, is not suitable for thinning large surfaces of aluminum bars.
Aluminum is especially difficult to clean.
Ultrasonic hardening, used for soldering narrow gauges, is not suitable for thinning large surfaces of aluminum bars. At the Dynamo plant they developed a method for abrasive and abrasive crystal parts of aluminum tires.
In addition to ultrasonic soldering machines, abrasive solvents are used for abrasive processing of aluminum. Unlike conventional soldering irons, abrasive grinding parts 5 (Fig.
68), pressed from solder powder and asbestos, which acts as an abrasive.
Problems in soldering, welding and milling of aluminum and its alloys, due to the presence of an extremely stable oxide film on their surface, can be easily eliminated by ultrasound.
In addition to ultrasonic soldering machines, abrasive solvents are used for abrasive processing of aluminum.
Unlike conventional electric soldering irons, abrasive grinders have a working stick 5 (Fig. 68), pressed from solder powder and asbestos, which act as an abrasive.
An important advantage over the above mentioned methods of potassium aluminum is the use of ultrasound.
Ultrasonic soldering is used for soldering and tinning of aluminum.
Category: “Working with metal”
Aluminum in the air is quickly coated with a layer of oxide, which prevents the solder from bonding to the metal. Using ultrasound, the oxide film is crushed and removed from the surface, whereby the solder is exposed to the aluminum surface.
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Soldering any metal parts at home is not a difficult task; many boys, especially those who are passionate about radio engineering, can easily cope with it. For soldering, or tinning, you need a soldering iron itself (the most primitive one, requiring heating on a heat source, or a more advanced one - with an adjustable temperature), solder, flux and rosin.
Parts prepared for soldering are cleaned and degreased using sandpaper, gasoline or solvents.
Then flux is applied to the surface, which prevents oxidation processes on the parts being soldered.
Using a soldering iron, the tip of which is first dipped in rosin, solder is applied to the soldering site.
How to solder aluminum yourself
However, not everything is so simple - some metals and alloys are difficult to solder.
How to solder aluminum? The whole difficulty is that aluminum alloys oxidize in air in a fraction of a second, forming films that make soldering using conventional methods impossible.
However, there is a method that allows you to solder aluminum surfaces using the most ordinary soldering iron, solder and rosin.
Soldering aluminum will require a fairly powerful soldering iron (60-100 W), since this metal has very good thermal conductivity.
It may be necessary to additionally heat the parts to be soldered over the flame of a gas stove.
The secret is that the joint is rubbed with brick, sand, mortar and immediately filled with rosin.
Use a soldering iron tip to wipe the parts being soldered, removing the oxide film.
As a result, we get a very strong connection without any special costs.
Solder for aluminum, consisting of tin and zinc (tin and bismuth), coupled with a flux of paraffin and stearin, also gives a good result if the soldering site is protected from oxidation with rosin.
How to solder aluminum when it comes to wires? In this case, you can probably do without soldering altogether: for example, use a terminal block.
If you need to connect wires in a limited space, where is it impossible to place a terminal block or similar connector?
Then it’s better to just twist it (wind the wire one on top of the other) and solder it and crimp it with pliers.
Flux for soldering aluminum, active, based on orthophosphoric acid, is quite accessible today.
You can buy it at any store that sells various types of radios - and electronic parts and components.
This is perhaps the easiest and most effective way to solder aluminum.
More on the topic:
The composition of fluxes for high-temperature soldering is given in the corresponding section.
The table shows the composition, temperature ranges of activity and purpose of some fluxes developed from 1973 to 1984. Among organic acids and other substances suitable as flux activators for soldering aluminum and its alloys at temperatures<300 °С, пригодны только алифатические кислоты, их амиды, а также триэтаноламин, имеющий свойства основания.
Among aliphatic acids, the most active are monobasic acids: stearic, elaidic, oleic, lauric, copric, caprylic, caproic, valeric, butyric, propionic, acetic, formic. The activity of these acids increases with increasing relative molecular weight and melting point. When they interact with Al2O3 oxide, the following reactions occur:
Al2O3 + 6RCOOH → 2 (RCOO)3Al + ZH2O (1)
2Al + 6RCOOH → (RCOO)3Al + ZN2 (2)
The reaction occurs most vigorously with formic and acetic acids, less vigorously with caproic acid.
However, the introduction of these acids into fluxes is of little promise due to their intense boiling at the soldering temperature and a decrease in the energy of COO-HC bond cleavage with increasing molecular weight of the acid. Salts of carboxylic acids obtained by reactions (1) and (2) are thermally unstable. For example, aluminum acetate decomposes at a temperature of 200°C.
| Brand or number of flux | Flux composition, % | Temperature activity interval, °C |
Note |
| 1 |
4-7 ammonium borofluoride; 4-7 cadmium borofluoride; epoxy resin rest |
<450 |
For soldering aluminum and Al alloy - 2% Mg(AMg2). High corrosion resistance |
| F59A |
10±0.5 cadmium fluoroborate; 2.5±0.5 zinc fluoroborate; 5±0.5 ammonium fluoroborate; 82±1 triethanolamine |
150-320 |
For soldering aluminum or AMts alloy with copper and steel with solders based on: Sn - Zn, |
| F61A |
10 zinc fluoroborate; 8 ammonium fluoroborate; 82 triethanolamine |
150-320 |
For soldering aluminum, beryllium bronze, galvanized iron, copper with solders based on Sn - Zn, Zn - Cd |
| F54A |
10 cadmium fluoroborate; 8 ammonium fluoroborate; 82 triethanolamine |
150-320 | |
| 3 |
7 bismuth bromide; 47.9 acetic acid; 55.1 oleic acid |
<380 |
For tinning in liquid tin it is more active than F54A flux |
| 4 | <350 |
For tinning aluminum alloys, slightly corrosive and active |
|
| 5 |
1.5 triethanolamine; 4 salicylic acid; 94.5 ethyl alcohol |
150-320 |
For soldering aluminum with copper, beryllium bronze, galvanized iron with solders based on Sn-Zn and Zn-Cd |
| 6 |
30 g lithium iodide; 200 ml oleic acid |
<450 |
For soldering aluminum |
| 7 |
4.2-10 titanium iodide; 16.8-22 rosin; caproic acid - the rest |
<450 | |
| 8 | <450 | ||
| 9 |
10-15 zinc tetrafluoroborate; triethanolamine rest |
≥350 |
For soldering aluminum wires with insulation (increases its stability) For soldering aluminum |
| 10 |
7.5 aniline fluorohydrate; 92.5 rosin |
<250 | |
| 11 |
83 triethanolamine; 9 cadmium fluorine borate; 7 ammonium acid fluoride; 1 rosin |
> 150 |
Among dibasic saturated acids, which are stronger than monobasic acids, the first three members of the homologous series of acids (oxalic, malonic, succinic) do not have activity when soldering aluminum, which is due to their decarboxylation when heated.
Higher acids have the same activity in fluxes as monobasic acids, with the same number of atoms in the radical.
Acid anhydrides are not active during soldering. Halogen-substituted acids have higher activity in fluxes for soldering aluminum, which is explained by the simultaneous effect of both the carboxyl group and the halogen atom on aluminum oxide.
It was discovered that some solid amino acids are active in fluxes: α-aminopropionic and phenylanitronyl, which ensure good spreading of solder.
Taking into account the physical properties, degree of toxicity and activity in fluxes among organic acids, the most suitable can be considered higher liquid unsubstituted acids, their solid analogues and amino acids.
The fluxing ability of mixtures of acids in any ratio does not exceed the activity of the component with the highest molecular weight.
Salicylamide and urea are equivalent in activity to caproic or elaidic acid.
Adding salts to acid solutions
The activity of ammonium salts of organic acids is close to the activity of the original mono- and dibasic acids. These salts have advantages over amides - less volatility during soldering and better solubility in acids.
It is characteristic that the introduction of organic acids and their derivatives into triethanolamine does not increase its activity when fluxing aluminum alloys.
A further increase in the fluxing activity of acidic organic solutions is achieved by adding halide salts of amines or metals to them.
The introduction of LiI and SnCb into decyl alcohol (boiling point 231°C) or into caproic acid (boiling point 205°C) LiBr, LiI, NaI, SnCb in the form of crystalline hydrates activates the solution.
The introduction of 95% ethyl alcohol into acid fluxing salt solutions deactivates them due to the displacement of water according to the reaction:
Al (OR)3 + 3H2O → Al (OH)3 + 3ROH.
However, the presence of water of crystallization in an alcohol solution of tin chloride does not affect its activity during soldering
Reactive organic fluxes
Reactive organic fluxes have been proposed for soldering aluminum with low-melting solders.
The basis of these fluxes is the organic amino alcohol triethanolamine, and the activators are fluoroborates of heavy metals and ammonium. At the points of contact of fluoroborates with aluminum, metals are deposited through discontinuities in the Al2O3 oxide film: cadmium and zinc. During heating, triethanolamine residues transform into an inert, resin-like substance that does not cause corrosion of solder joints. These fluxes and their residues after soldering have pH = 8, which also confirms their non-corrosive activity.
All these fluxes do not differ in corrosive activity when soldering aluminum, but when soldering it with the AMts alloy, copper and its alloys, the F59A flux is the most effective. The temperature range of activity of these fluxes is 150-300°C. Fluxes of this type are unsuitable for lap soldering with solder placed at the gap of deformable alloys AMg, D1, D16, V95 and cast aluminum alloys. They can only be used when tinning the soldered aluminum surface followed by soldering, for example with LTI-120 flux.
In this case, the temperature between the soldered parts during soldering should not differ by more than 10°C.
How to solder aluminum with a soldering iron
Residues of fluxes are easily washed off with water or wiped with a damp cloth moistened with water or ethyl alcohol, and do not cause any noticeable corrosion for more than 1000 hours. Studies have shown that, in comparison with fluxes containing acetic, nylon, oleic, lauric as a solvent acids, and bismuth chloride as an activator, F54A flux provides a large area of spreading of P250A solder over AD1 aluminum; but it is less active in soldering corrosion-resistant steel, brass and copper than fluxes containing bismuth chloride.
Fluxes F54A, F59A and F61A are suitable for soldering in the specified temperature range with P200A, P250A, P300A, P170A and P150A solders.
To do this, use temperature-controlled electric soldering irons, induction heating, and soldering by immersion in molten solder. Soldering with these fluxes when heated with an open flame is unacceptable due to the possibility of their combustion. At temperatures above 350 °C, solder joints are formed in the soldered seams of contacting joints made with these fluxes. With rapid heating (electrical contact, induction methods) in pure argon, soldering with these fluxes is possible at a temperature of 320 °C.
There is data on the use of low-melting solder Sn - (8-15)% Zn - (2-5)% Pb with a melting point of 190 ° C with flux in the form of a solution of boron-fluoride and ammonium fluoride in monoethanolamine for soldering aluminum alloys.
In fluxes for low-temperature soldering of aluminum and its alloys, instead of rosin, it is proposed to use pentaerythritol benzoate, which is more heat-resistant than rosin, and its residues are non-corrosive and, in the form of an elastic film, protect solder seams from oxidation. Carboxylic acids are used as flux activators. Soldered joints (P250 solder) are not destroyed in a saline solution for 200 days. Solder wire (Sn-Pb-Ag) with a core of the specified flux is suitable for soldering all aluminum materials that contain less than 3% Mg and 3% Si.
Craftsmen have no problems with soldering copper, brass and steel wires and parts, but if we have to deal with aluminum surfaces, the solder does not hold the product, and soldering turns into torture. The problems are caused by the fact that a thin but very strong oxide film of Al2O3 forms on the surface of this metal. This film can be mechanically removed - for example, to clean the product with a nail sticker - but when it comes into contact with air or water, the metal will immediately be coated with the film.
Despite the problems we face, aluminum products can be soldered. There are several ways to solder aluminum.
Soldering of aluminum alloys
Excellent results can be obtained with the following alloys:
- two parts zinc and eight pieces tin
- one piece of copper and 99 pieces of tin
- one piece of bismuth and 30 pieces of tin
Before soldering, both the alloy and the part must be well heated.
You should also remember that soldering acid should be used in this soldering method.
Aluminum soldering with special currents
Standard currents do not dissolve the oxide film on the surface of aluminum, so special active currents must be used.
Aluminum soldering flux is used to work with pliers with a working temperature of 250-360 degrees. This flow, during soldering and hardening, clears the oxide film, cleans the metal surface and, therefore, the solder spreads better over the surface.
All this leads to the creation of a tighter and more durable connection of the molten parts. Excess of this flow can be easily removed with solvents, alcohol or special liquids.
Other methods of soldering aluminum
There are also non-standard ways to solve this problem, for example:
- Thoroughly clean the soldering iron of any aluminum products and add a few drops of concentrated copper sulfate.
A small piece of copper wire, peeled in a circle with a diameter equal to the soldering point, and the free end of the wire is connected to the "plus" output of the battery for 4.5 volts. A piece of wire with a rolling circle falls onto a small amount of copper sulfate. The negative battery should be connected to the part on which a certain layer of copper will be installed after a certain time.
How to Solder Aluminum Using a Tin Can
Once dry in this room, you can usually weld the necessary parts or wires.
- In this case, use abrasive powder with a small amount of transformer oil to obtain a liquid paste.
This paste is used for refined soldering products. Then the soldering iron is good and apply these places until the tin layer is separated on the surface. Then rinse the parts and then solder as usual.
- This method requires a transformer.
Its disadvantage is associated with the product, and the connection is connected to a copper wire of a large part, consisting of small vessels. If you connect this wire to a future soldering site for a short time, a micro-soldering joint of copper and aluminum will be made, which will allow the wire to be connected in the normal way in the future.
To simplify the process, you can use soldering acid.
Soldering aluminum utensils (without soldering iron)
Some household needs use aluminum accessories, sometimes it breaks and does not buy a new one (which is very expensive), you can fix these products by soldering without a soldering iron.
The following method is suitable for sealing small holes (up to 7 mm in diameter).
- The soldering point should be cleaned with a metallic shine using sanding paper or a file. If the containers are enameled, the holes around the enamel must be removed within a radius of 5 millimeters.
To do this, the light touches a hammer from a container, which is thrown away by the enamel. Then you need to clean the metal.
- The soldering point is lubricated with blown acid or covered with earth rosin. From the inside, a piece of the pot is placed over the hole and then the heater is heated over the fire of the stove.
If the containers are enamel, it is preferable to heat them over a light bulb - this allows the area to heat up more, so the other sponges are not affected by the heat.
- When heated, the mucus melts and closes the hole in the pan.
At the same time, a soldering iron is not needed.
There is an opinion that before soldering aluminum at home, you should stock up on special quality solder, as well as a special soldering tool (a gas torch in particular). In this case, the following facts are given as explanations: firstly, there is always an oxide film on the surface of aluminum and, secondly, the heating temperature is quite high.
And, indeed, due to the characteristic metallic coating, tinning and soldering aluminum at home is associated with certain difficulties. Special solders used simultaneously with active fluxes for aluminum will help solve this problem.
Let's look at each of the consumables presented above in more detail.
High temperature solder
The composition of traditional low-melting solder includes such essential components as tin (Sn) and lead (Pb) with small additions of bismuth (Bi), cadmium (Cd) and zinc (Zn). Using this soldering composition, it is possible to process copper and steel workpieces, during soldering of which the surfaces rarely heat above 300 degrees.
Before soldering aluminum using conventional means, you should be aware that the specified compositions are not suitable for processing this metal, since the operating temperature of its heating must be much higher. For work in this category, special solders for aluminum will be required, which include high-temperature silicon. As additives, they contain copper and other active components (silver and or zinc components, for example).
Important! They should also include an aluminum component.
Note! By increasing the amount of zinc, aluminum solder becomes highly resistant to corrosion.
Thus, it is customary to classify high-temperature solders as those that contain essential components such as silicon, copper and aluminum (zinc). As an example, we can consider a well-known example of domestic aluminum solder - 34A, as well as its imported analogue under the designation “Aluminium-13”. They usually contain up to 87% aluminum and approximately 13% silicon, which allows the soldering temperature to be raised to approximately 590-600°C.
Flux component
Flux for soldering aluminum is usually selected taking into account the chemical activity of its components in relation to this metal. For these purposes, such well-known domestic mixtures as F-64, F-59A, F-61A, which include ammonium components and other additives active in relation to aluminum, are quite suitable.
Containers with these soldering reagents usually have labels with special marks “for aluminum soldering.”
To work with this metal, a flux can be used, produced under the brand name “34A”, which includes chloride compounds of potassium, zinc and lithium in the required proportion, as well as sodium fluoride (10%). These mixtures are considered most suitable when soldering aluminum with copper or other non-ferrous metals is intended.
Soldering procedure
Surface preparation
Soldering aluminum with tin with active additives begins with preparing the surfaces of the jointed parts or products. To do this, you need to perform the following operations on them:
- Thoroughly degrease them using a soft flannel soaked in acetone;
Additional Information. Instead of acetone, any traditional solvent that replaces it (gasoline, for example) can be used.
- Clean the area to be soldered, for which it is recommended to use fine-grained sandpaper;
- As a backup option, surface etching with special active compounds can be proposed, however, due to its specificity, this procedure is used extremely rarely.
It should be remembered that it is not possible to completely remove the oxide film in one go, since a new thin layer immediately forms in this area. Surface cleaning is not carried out to completely remove the unwanted coating, but to partially neutralize it before flux treatment. Once this operation is completed, the surface can be sealed quite easily.
Heating the soldering area
In order to solder small-sized aluminum workpieces, a low-power soldering iron (no more than 100 watts) is sufficient. To solder massive products or parts, you will need to use a higher-power soldering iron. A special powerful tool or a gas torch is best suited for these purposes.
Soldering aluminum with a gas torch (sometimes a blowtorch is used for these purposes) has special specifics, manifested in the following features:
- Firstly, it is not recommended to overheat aluminum as it may partially melt. To prevent this effect, during soldering you should periodically touch the solder to the surface being treated. Its melting will mean that the required temperature has already been reached;
- Secondly, it is undesirable to use oxygen as an enricher of the gas mixture, since it can provoke oxidation of the metal.
Soldering instructions
In order to obtain a soldered connection of aluminum products, you should be guided by a standard methodology, which involves the following procedure :
- First, the surface at the soldering site is degreased, after which this area is thoroughly cleaned;
- If you need to solder one part to another, both of them are securely fixed in a vice or clamp;
- After this, you can begin to warm up the joints;
- During the soldering process, a special aluminum solder containing an activator is used to touch the joint several times. When using conventional solder, a special flux will be required to actively affect the oxide film.
Note! To reliably destroy the surface film of aluminum oxide, it is recommended to use a brush with steel wire bristles. Using this simple tool, during the soldering process it is possible to evenly distribute all the solder along the plane of the aluminum workpieces being processed.
What to do if you don’t have the required materials
In a situation where the household does not have the consumables necessary for soldering, you can use traditional solders. In this case, the flux is replaced with ordinary alcohol rosin, with which the aluminum surface is poured after its preliminary cleaning. This provides protection against oxidation and the formation of unwanted oxide films.
With this approach, the soldering iron is simultaneously used as a tool that destroys this obstacle. For this purpose, a special scraper is installed on the tip of the soldering device, through which it is possible to constantly clean off the resulting oxide layer. In addition, it is possible to increase the productivity of this process if you add a little sawdust generated when cutting metal to the rosin.
In this case, solder the parts as follows:
- First, a well-heated soldering iron with a pre-tinned tip melts a small amount of rosin at the soldering site;
- After it completely covers the entire heated area, rub the soldering iron tip over its surface with force. At the soldering site, you need to add a small amount of metal filings, which, together with the tip, effectively destroy the oxide film;
- Upon completion of the tinning procedure, the aluminum workpieces being processed are connected to each other and thoroughly heated with a conventional soldering iron.
In the final part of the review, we note that soldering without the use of special equipment and active consumables is a very labor-intensive and troublesome procedure that does not guarantee a positive result. It is for this reason that only well-trained users with extensive experience working with soldering equipment can resort to this soldering method.
In the case where you do not have absolute confidence in your abilities, it is best to purchase all the necessary materials and try to rent the required tool (a gas burner in particular).
Video
Seal
Flux for soldering aluminum
Once upon a time, I thought that aluminum soldering was done in factories and was not done at home. However, over time, this misconception has dissipated. This article is about how to solder aluminum at home and what to use to solder aluminum.
At school, the topic of aluminum was previously discussed in chemistry and physics lessons about its properties; it has excellent electrical conductivity and thermal conductivity, but is very difficult to solder. The difficulty of soldering it is due to the fact that an oxide film instantly forms on the cleaned surface, which is very resistant to various aggressive environments.
Once upon a time I came across such information that soldering is carried out with a solder consisting of tin and zinc or tin and bismuth. However, practice shows that it can be soldered quite normally with conventional POS 40 and POS 60 solders. It doesn’t matter what you solder with, the main thing is how.
The mechanical strength of such soldering is small, but what is mainly required is not the strength, but the electrical conductivity of the joint. I can’t say what else can be used to solder aluminum besides these solders; I haven’t tried it. You can also solder with lead, the main thing is that the soldering iron has enough power and heats it up to a sufficient temperature.
Soldering iron
As mentioned above, aluminum has increased thermal conductivity, which is why cooling radiators are made from it. Therefore, for soldering large elements, the power of the soldering iron should be high, 100 - 200 W. If, of course, these are two small wires, then perhaps 60 - 100 W will be enough power.
Fluxes
Nowadays there are no problems with the choice of means, but previously I had to use anything to tin aluminum - aspirin, technical petroleum jelly, grease. For soldering aluminum at home, I chose two good fluxes F-64 and FTBf - A, and FIM flux also has good results. This is perhaps the most important thing, the better the flux, the easier the soldering.
The main thing is not to run into a fake, but there is enough of that now, you buy this “Flux for soldering aluminum”, but it’s no good. By the way, regarding the question of what else can be used to tin aluminum, there is such a flux F-34, this can be said just by its composition that it is aspirin. Aluminum can also be tinned with soldering oil.
Tinning methods
With good flux, the process of tinning and soldering is not a problem. It’s another matter if you don’t have one at hand, here the process becomes more labor-intensive.
The most important thing in the tinning process is to prevent contact of the surface being cleaned with oxygen. Therefore, the surface to be cleaned is thickly lubricated or filled with flux, and if necessary, it can be heated a little. You can simply, if the product is small, for example wires, clean them directly in the solution, pouring it into something.
Regarding the method of soldering aluminum with a soldering iron with a rosin solution, I did something like this. I pre-cleaned the surface, lubricated it with a solution and sprinkled it with copper or iron filings. Then, pressing with the soldering iron tip (the harder the better) and stripping off the oxide, I tinned it with regular solder.
Sometimes, if it was necessary to solder two wires, aluminum for example and copper, I used this method. I twisted the two ends of the wire and welded them with a current discharge using a graphite core from a battery. For such “welding” I used a 6-12 volt transformer with a current of 3 amperes. We connect one end of the wire from the transformer to a twist, and screw the battery rod to the second (you can use a brush from the engine). When touched, an arc appears and the ends are soldered into a ball.
So soldering aluminum at home is quite possible and not such a difficult task. A little practice and that's it.
Aluminum is a material with good strength and high thermal and electrical conductivity. These positive qualities contribute widespread use of metal in industry and everyday life. Quite often there is a need to connect aluminum parts or seal a hole in an aluminum container. But not everyone knows how to solder aluminum at home.
Soldering aluminum
One of the most well-known methods of joining metals, especially in electrical work, is soldering. It provides lower resistance of connections, and, as a result, less heating under the influence of electric current. Because the aluminum along with copper- the main conductive material in electrical networks and devices, the need for soldering arises quite often.
The difficulty is that the “winged metal” in air is instantly covered with a film of oxide, to which the molten solder does not stick. It is necessary to remove the oxide layer using mechanical cleaning, but it forms again almost instantly.
In order to avoid the re-formation of the oxide film, many techniques have been developed. Among them:
- Cleaning small parts under a layer of liquid flux.
- The use of fluxes in conjunction with abrasive materials.
- Using copper sulfate to create a copper film on an aluminum product.
- Application of special fluxes and solders.
Cleaning under the flux layer
Small aluminum parts, such as conductors, can be cleaned by dipping part of the part into a liquid flux, which can be a regular rosin solution or soldering acid. Liquid flux will protect the area being cleaned from contact with oxygen and film formation. Regular transformer oil has the same protective effect.
Abrasive materials
Iron filings are often added to the flux (the same rosin). During the soldering process, it is necessary to rub the heated area with the tip of the soldering iron. Under the influence of friction, the sawdust peels off the oxide layer, and the rosin blocks the access of oxygen to the liberated metal. Instead of sawdust, any crumbling abrasive can be used: sandpaper or even brick.
Using copper sulfate
An interesting method using galvanostegy. Two aluminum electrodes are dipped into a solution of copper sulfate and connected to the poles of an electric battery. The electrode connected to the positive is stripped. As a result of electrolysis, copper begins to deposit on the cleaned surface. When the aluminum is completely covered with a copper film, the part is dried. After this, soldering is much easier, because copper is an excellent material for this type of connection.
Special solders
The highest quality connection at home can be obtained using low-melting solders based on tin and copper and special fluxes. The most popular domestic flux is F64, which allows you to solder aluminum parts without mechanical stripping. So, for example, soldering aluminum to copper can be done without problems, or an aluminum tube can be sealed from the inside, which cannot be cleaned by any other means.
In this case, conventional low-melting tin-lead solders with a melting point of 200−350 degrees are used. The soldering iron should be quite powerful - from 100 W and above. The reason is the high thermal conductivity of aluminum. An insufficiently powerful soldering iron simply will not be able to heat the soldering area to the melting temperature of the solder. Only very small parts(mainly in radio electronics) can be connected with a 60 W soldering iron.
A soldering iron is not suitable for soldering large aluminum parts. Here it is better to use any gas burner that provides heating up to 500-600 degrees, and one of the specialized solders. One of the most popular is HTS-2000 - a flux-free solder for soldering aluminum, copper, zinc and even titanium.
He has several advantages:
- Low melting point (390 degrees Celsius).
- Can be used without flux.
- Reliability of the connection (in many cases it can replace argon welding).
True, HTS-2000 does not exclude the stripping process. Moreover, during the soldering process it is necessary to remove the oxide film with a solder rod or a wire brush to ensure a reliable connection. However, this method allows you to perform such work as sealing leaky aluminum containers, for example, cans, or even car aluminum radiators.
In addition, HTS-2000 is practically the only (with the exception of argon) way of joining two “winged” metals: aluminum and titanium.
There are other high temperature solders designed specifically for aluminum soldering. For example, 34A, which contains two-thirds aluminum, as well as copper and silicon. But the melting point of such solders is 500−600 degrees Celsius, which is close to the melting point of aluminum itself.
Therefore, using high-temperature solders at home is dangerous - an aluminum part can be irreparably damaged when heated to such high temperatures.