Silumin - what is this alloy and where is it used?

Tin-aluminum alloy

Tin is a common metal in nature, but its alloys, such as tin and aluminum, are also popular.
When combined with tin, pure metals acquire improved properties as before the smelting process.

In its pure form, tin is used to create various products for the food, light, aviation, radio engineering, textile, etc. industries. industry. Aluminum is common in thermal structures, cryogenic technology, and light industry.

Aluminum and tin are very different elements. Aluminum is light and easily soluble in acids, so the smelting procedure is very difficult. But due to its positive properties, this alloy is often used in industry.

The alloy system is one of a kind. The alloy becomes solid at 650 ºС, but tin remains liquid up to 225 ºС. In order to eliminate the problem, a high solidification rate is used when melting

With the development of the machine industry, the mixture is suitable for parts of various equipment, and is used for laying out high-voltage lines.

6% alloys with small amounts of nickel and copper are used for bearings. It is tin that provides sliding in these joints, and the products themselves become unique among others.

Thanks to tin in the alloy itself, aluminum's resistance to corrosion improves, especially when combined with copper.

The alloy is very advantageous because it is strong, light, economical and easy to process at low temperatures. It easily conducts heat and electricity, which makes it possible to use it in construction. The compound is also highly reflective.

Despite its positive qualities, the aluminum-tin alloy has a low linear expansion coefficient.

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What is silumin

Silumin is a metal alloy made from aluminum. In general, various aluminum alloys are widely used in industry, just like alloys containing lead.

The formula of silumin is quite simple, the main components are aluminum and silicon, depending on the type of silumin, the silicon content in percent can be from 10 to 20. Moreover, alloys with the addition of silicon are more durable than aluminum with a lead additive.

Soldering aluminum with tin

Aluminum is often found in the manufacture of cookware, in electrical wiring, casings of various products and other places. To solder aluminum I use different types of solders. One of the most common is tin, since it is the easiest to find, and its properties are quite suitable for obtaining a high-quality compound. Soldering of aluminum with tin involves the use of fluxes and can be carried out both in the workplace and at home. The solder itself often contains some additives, such as zinc, which promotes better soldering and spreading of the filler material.

Tin is a low-melting solder, which is great for working with aluminum because its melting point is relatively low. If you use hard-melting solders, then with strong heating, aluminum may lose its qualities, or even melt before the filler material itself. Several soldering methods can be used here, and are equally effective.

Alloy composition

Depending on the type, silumin has a different composition. The most common types are:

• an alloy of aluminum with silicon, with silicon containing about 10%;
• the second type of silumin has higher strength. The alloy composition contains about 20% silicon;

In addition, other aluminum alloys are often used in industry:

• an alloy of aluminum with magnesium and silicon, often used for the manufacture of automobile bodies;
• an alloy of aluminum and tin, used in the production of cast bearings;
• aluminum-magnesium alloys are used in aggressive environments, for example, in the exterior decoration of buildings.

Advantages

• Soldering aluminum with tin is relatively inexpensive, since the cost of solder is low;
• The material is universal and suitable for working with both thick and thin workpieces;
• Solder melts well when exposed to temperature and spreads well over the surface, forming a high-quality connection, penetrating into all small cracks and recesses;
• Due to the low melting point, the process is relatively fast;
• The material is always available for sale and there are no problems with its search and selection.

Flaws

• After completion of the process, the finished product will have a lower melting point at the soldering site;
• The strength of the connection is not designed for high mechanical loads;
• Soldering aluminum with tin at home does not provide such a high-quality connection as other connection methods and can be used mainly for minor repairs of products with little responsibility during operation.

Nuances when soldering

The main feature when soldering aluminum is the fight against oxide film. It has become the biggest problem that needs to be solved even before the soldering process using cleaning, solvents and other methods. Soldering aluminum with hard solders requires strict adherence to the modes, since too high a temperature can ruin the metal itself, and too low a temperature will not allow you to make a high-quality connection. When working with large thicknesses of metal, soldering is carried out in several layers.

Soldering aluminum with regular tin

If you don’t have argon arc welding or special electrodes at hand, but you need to solder aluminum, then you can get by with just tin. Aluminum products are the most affordable and widespread, so you often have to repair them yourself.

And although aluminum is easy to machine, it is not easy to solder. The main problem that arises when soldering aluminum is the oxide film on its surface. Heated aluminum cools quickly, which instantly leads to the formation of oxides.

Therefore, in most cases, active mercury fluxes and replaceable soldering iron tips are used for soldering aluminum products. However, if you try, you can solder aluminum with ordinary tin, using a gas burner, rosin and a soldering iron.

Effect of doping

Iron

Iron is always present in aluminum alloys and most often forms intermetallic compounds AlFeSi in combination with silicon and aluminum. These intermetallic compounds do not affect the strength properties of the alloy, but if the alloy is not properly heat treated, they can negatively affect its compressibility. Accurate control of iron content is important when anodizing profiles. Different iron content may result in differences in color shade or matte finish of the anodized surface.

Manganese

Manganese is added to 6xxx alloys for several reasons.

• Manganese reduces the duration of homogenization, helping to accelerate the conversion of β-AlFeSi particles to α-AlFeSi.
• It prevents the growth of coarse grains during heat treatments of high-strength alloys such as 6061 and 6082.
• Another benefit of manganese is that its addition increases the ductility of the alloy, as it helps prevent the precipitation of free silicon at grain boundaries.

In the most durable aluminum alloys of the 6xxx series, which have a high manganese content (more than 0.1%), it reduces compressibility and also increases sensitivity to hardening.

Chromium

Chromium acts in much the same way as manganese, but its effect on hardening sensitivity is more significant.

Copper

• Copper additives help improve the quality of mechanical processing (cutting, milling, etc.) of extruded profiles.
• The low copper content reduces the negative impact of the time delay in performing the artificial aging operation on the level of strength properties of high-strength alloys, for example, 6061.
• When the copper content is more than 0.2%, the corrosion resistance of the 6xxx series alloys decreases.

Zinc

• Zinc does not have any negative effect on the mechanical properties of the 6xxx series alloys.
• However, with a content of more than 0.03%, zinc can cause a defect consisting of selective (differentiated) etching of the surface of profiles during anodization.

Soldering aluminum with regular tin and rosin

After the surfaces of aluminum products are treated with stone, a thin layer of heated rosin is applied to them. You can use ready-made liquid rosin, or you can melt pine rosin using a soldering iron or gas burner.

Further, the process of soldering aluminum is not much different from soldering copper or other non-ferrous metals. To do this, take a soldering iron and apply heated tin to the place where the parts are soldered. You can heat the tin with a torch and then rub it into the aluminum with a soldering iron tip.

Even liquid tin, due to the characteristics of aluminum, will not spread on the surface of the part. Therefore, we take a soldering iron and carefully rub the tin into the joint. In this case, as mentioned above, due to the presence of dust on the surface of aluminum, the oxide film is destroyed.

After soldering, let the parts cool and check the connection for strength. And, as practice shows, the soldered connection of aluminum products thus turns out to be much stronger than those made of copper.

All this is explained by the fact that the melting point of copper is much higher than that of aluminum. Aluminum also has a greater ability to diffuse with other metals.

This is the simplest and most affordable way to connect two aluminum parts or “patch” a hole. It does not require any special tools or welding. It is quite possible that the method will be quite suitable for soldering parts made of other non-ferrous metals.

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The difference between silumin and other metals and alloys

To understand what is in front of you, silumin or steel, just remember and pay attention to a few simple things:

• color, silumin is distinguished by a gray surface color and a silvery color on the cut. Remembering this, you can easily distinguish it from copper, bronze or brass. The surface of these metals has a yellow or reddish tint;
• magnetic properties, silumin, unlike steel, is not magnetic;
• weight, silumin has less weight than similar steel products.

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Soldering aluminum with tin: methods and rules

Aluminum is a common material used to create wires, cookware, and more. Due to its characteristics, aluminum can deteriorate over time or other influences, which necessitates repair work. The best option in this case is soldering, which can be done in various ways and using different elements. The most convenient way is to use tin for soldering aluminum.

Peculiarities

Aluminum is a metal that has sufficient density, but is also lightweight. It is these advantages that have made it possible to use this material so widely for the manufacture of tableware. The process of using aluminum products is not complicated, but from time to time situations arise when it is necessary to eliminate a crack, hole, or solder parts of the cookware. In addition to kitchen utensils, aluminum is used to make wire, which is convenient to work with due to its softness but good strength.

There is only one drawback to this wire - it is very difficult to solder.

Most metals can be heated and soldered, but aluminum is a special substance that oxidizes when exposed to air and becomes coated with an oxide film that no metal can sit on top of. To solder this material, you need to select a suitable flux.

Flux is a substance or several components that can be used to remove oxides from metals that need to be soldered. Thanks to the organic and inorganic compounds of fluxes, it will be possible to remove surface tension and improve the spreading of liquid solder. In addition, it allows you to protect the material from environmental influences.

Since aluminum is an unusual metal, it is worth looking for a special flux for it. Soldering aluminum with tin is considered the simplest and most convenient option in which you can get the desired result. The advantages of using tin for aluminum smelting include:

• low price of the material;
• the ability to use tin for parts with different thicknesses;
• high melting rate and the ability to cover the entire surface of the aluminum part on which work is being carried out;
• low melting point, which allows you to quickly cope with the task;
• general availability of tin.

Properties of silumin

Silumin has properties that have made it a very popular material on the modern market. It is quite durable and reliable, and the low cost and ease of manufacturing complex elements often make this material irreplaceable. Let's take a closer look at its properties.

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Chemical properties

Silumin alloy is similar in its chemical properties to pure aluminum, it all depends only on the amount of impurities. For example, unlike duralumin, silumin is not susceptible to corrosion in conditions of high humidity, including sea water.

Physical properties

In terms of its physical properties, silumin is often compared to stainless steel, but at the same time it is much lighter. The alloy has the following physical properties:

• the strength of the material is not much inferior to its steel counterparts. It becomes possible to achieve a ratio of low weight and high strength with a lower density of the alloy compared to steel;
• in appearance, silumin is very similar to pure aluminum, the color of the products is gray, and in cross-section - silver;
• the material has high fluidity, which makes it possible to manufacture products of complex shapes from it;
• the melting point of silumin is relatively low, about 700 °C;
• Along with excellent strength, silumin has high fragility;
• silumin is not magnetic.

Mechanical properties

Mechanical properties directly depend on the chemical composition of the alloy and its manufacturing process. The main mechanical characteristics of silumin can be considered:

• fragility, the material may crumble during processing;
• high density;
• low microhardness.

Foundry properties

Aluminum-silicon alloys are excellent for making cast products. At the same time, the material has high specific strength, low weight and resistance to corrosion. An additional advantage is the low cost of the finished product.

Despite the obvious advantages, silumin also has a drawback - increased gas porosity, however, modern technological processes make it possible to eliminate this feature during the casting process.

Methods

In the process of melting aluminum with tin, an oxide film appears, which can only be removed with the help of solvents or metal brushes. To properly melt the base metal, you need to choose the right temperature. At high rates, aluminum will be destroyed, at low rates, it will not be possible to successfully solder the materials.

There are several methods of tin soldering.

1. Using a gas burner, which is attached with a hose to the cylinder, which makes it possible to adjust the power of the incoming gas. The fire temperature can be adjusted by changing the pressure inside the cylinder.
2. Using gasoline burners. It is used for joining thin layers of metal due to the impossibility of changing and increasing the flame temperature.
3. Using a soldering iron. For work, additional materials are required, such as rosin. The soldering iron needs to be heated to a temperature that melts both rosin and tin.

For such work, it is necessary to use flux for aluminum F-59A, F-61A and active flux for soldering aluminum. When melting metal, you need to have the following tools with you:

• solvent;
• metal brush;
• soldering iron or torch;
• cutting tool;
• flux.

Once you have everything you need, you can get to work.

Cast aluminum alloy 850.0

Alloy formula:

6.2Sn-1Cu-1Ni

Chemical composition:

• copper: 0.7-1.3%;
• magnesium: 0.10 max;
• silicon: 0.7% max;
• iron: 0.7% max.
• tin: 5.5-7.0%;
• nickel: 0.7-1.3%;
• titanium: 0.20% max;
• others: 0.30% max;
• aluminum: the rest.

Impact of impurity content:

• high content of iron, manganese or magnesium reduces ductility and increases hardness;
• high silicon content improves sliding characteristics.

Typical mechanical properties in T5 condition:

• tensile strength: 160 MPa;
• yield strength: 75 MPa;
• relative elongation: 10%;
• hardness: 45 HB;
• Poisson's ratio: 0.33;
• modulus of elasticity: 71.0 GPa.

Physical properties:

• density: 2.880 g/cm3;
• liquidus temperature: 650 ºС;
• solidus temperature: 225 ºС.