Silumin: what kind of material is it, alloy composition, properties, melting point

Marking [edit | edit code ]

A - aluminum
K - silicon,
## is the percentage of silicon in the alloy,
@@ - other chemical elements contained in the alloy (if any).

There is another marking: AL##

, Where:

AL - cast aluminum,
## — alloy number.

The most common brands:

AK12 - 12% silicon, eutectic alloy.
AK9 - 9% silicon.
AK7Ts9 - 7% silicon, 9% zinc.

Application [ edit | edit code ]

They are used for casting parts in the auto, motorcycle and aircraft industries (for example, crankcases, cylinder blocks, pistons), and for the production of household appliances (heat exchangers, sanitary shut-off valves, meat grinders), in sculpture technology, in cheap electro-pneumatic replicas of weapons , sometimes they make keys.

The disadvantage of silumin is the high porosity and rough coarse-grained eutectic of castings, which greatly affects the reproducibility (stability) of the strength properties of the resulting parts. [1]

Silumin is an alloy of aluminum with silicon. Chemical composition - 4-22% Si, base - Al, a small amount of impurities Fe, Cu, Mn, Ca, Ti, Zn, and some others.

Al-Si alloys (silumins) have the best casting properties. High fluidity, low shrinkage, absence or low tendency to form hot cracks and good tightness of silumins are explained by the presence of a large amount of eutectic in the structure of these alloys.

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The density of most silumins is 2650 kg/m3, i.e. less than the density of pure aluminum (2700 kg/m3). They weld well. Mechanical properties depend on the chemical composition, manufacturing technology (modification, casting method, etc.), as well as heat treatment. In double silumins, as the silicon content increases to the eutectic composition, the ductility decreases and the strength increases. The appearance of large crystals of primary silicon in the structure of alloys causes a decrease in strength and ductility. Despite the increase in the solubility of silicon in aluminum from 0.05% at 200°C to 1.65% at eutectic temperature, binary alloys are not strengthened by heat treatment. This is explained by the high rate of decomposition of the solid solution, which partially occurs already during quenching, as well as the high tendency of stable silicon precipitates to coagulate. The only way to increase the mechanical properties of these alloys is to refine the structure through modification.

AK##@@, where A is aluminum, K is silicon, ## is the percentage of silicon in the alloy, @@ are other chemical elements contained in the alloy (if any). There is another marking: AL##, where AL is cast aluminum, ## is the alloy number.

Currently, almost all industries use aluminum alloy. It is used everywhere, from the production of dishes to the production of spare parts for cars.

How to clean aluminum cookware at home

Immediately after purchasing an aluminum kitchen item, you should boil it by adding 5 tsp per 1 liter of water. salt. If the walls become dark after cooking, rinsing in water with added ammonia will help restore the shine. You can try rubbing the walls with a soft cloth and dry teeth cleaning powder.

If stains appear on aluminum cookware, remove them with an apple cut in half. Dark plaque is removed with a damp sponge soaked in vinegar. Immediately after cleaning, the aluminum object is washed with clean water. Washing with water with dissolved borax at the rate of 1 l/1 tbsp will help restore shine. l. Burnt food can only be removed by soaking for a day.

It is believed that such dishes are quite difficult to care for. Housewives are afraid of damaging the oxide film that forms on the surface. This film has a protective property and appears after a chemical reaction of the metal with oxygen. Factories use electrochemical oxidation, which creates a film with great strength.

Thanks to the oxide film, food does not interact with the metal, so the quality of food heated in an aluminum pan remains high.

The acids and alkaline agents you use when cleaning can damage the protective film. The same applies to powders, brushes, scrapers, and scourers with iron fibers. Due to the fact that conventional products are of little use when cleaning aluminum cookware, women are at a loss when it comes to removing heavy stains.

If food is burnt on an aluminum frying pan, you should simply soak it for several hours or pour water and put it on fire. Baking soda or vinegar, diluted with water, will help deal with blackened metal. Whey also helps with black spots.

Silumin

To begin with, there are several different alloys that use aluminum. However, this one is considered the most popular among others. Silumin is the next step after aluminum. It is obtained using a silicon alloy added to this chemical element. The combination of these two elements provides the resulting alloy with increased hardness, as well as increased resistance to wear of parts made from the alloy.

The silicon content in such alloys ranges from 4 to 22%. It is also worth saying that some more elements may be added. These include copper, zinc, titanium, iron or calcium. It is also known that silumin contains from 5 to 14% silicon.

Properties of silumin

It is important that silumin is all alloys that were obtained based on silicon and aluminum, but it is necessary to understand that not all final materials have the same properties. You need to know that with an increase in the percentage of silicon content, the final strength of the material increases, but at the same time its fragility also increases. The main advantages that can be identified from this alloy include:

High strength.
Low physical weight.
High wear resistance of the material.
Also resistant to corrosion.
One of the important advantages is the price of silumin, which is considered quite low. Let's say kitchen utensils made from this material cost from 250 rubles. up to 2000-3000 rub.

All these advantages together were able to ensure the high popularity of this material.

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This material has only one drawback - its increased fragility. If we talk about mechanical stress, then silumin can withstand high loads, but if, for example, you drop a product made of this alloy, it will most likely crack. It is also worth noting that the melting point of silumin is not too high - only 580 degrees Celsius.

Production technology

Modern aluminum cookware has different properties, depending on the composition of the raw materials. For the production of kitchen items they use:

Primary metal grade A5. Food grade aluminum in its pure form has excellent thermal conductivity, but it is very soft. To give the product strength, additional elements are added to the metal. The resulting alloys (AK7, AK9, etc.) are safe for health, while retaining the beneficial properties of aluminum.
Aluminum cast iron.
The alloy inherited the best properties of two metals: heat capacity, corrosion resistance. Thick-walled kitchen items are made from raw materials: cauldrons, frying pans, ducklings. Important! The benefit of aluminum cast iron is that the kitchen item is lightweight. At the same time, the properties of cast iron are preserved - high heat capacity. Cooked food in aluminum cookware is less likely to burn and can even be preserved for a short time.
Bimetallic alloy. The raw materials are used for stamping kitchen items. Essentially, the material is sheets of aluminum and steel. Pots, kettles, and ladles retain an important property - thermal conductivity. However, due to steel, the walls of objects have become stronger and less porous.

If we talk about old aluminum cookware, the harm and benefit will be the same as from new modern kitchen appliances. Previously, pure food-grade aluminum without additives was most often used for production, as evidenced by the rapid appearance of dents in pans when dropped or hit.

The properties of cookware may vary depending on the technology of its production:

The sheet metal production technology is called stamping. The product is “squeezed” out of the sheet. After giving the object its shape, it is finished. Stamping is done by embossing or forging. The cheapest dishes are made using the embossing method. The object is extruded from the sheet by a rotating blank of the machine. Disadvantage: the positive properties of the metal are lost. Thermal conductivity and strength deteriorate. Thin-walled dishes are made using the embossing method, the bottom of which is often reinforced with an anti-deformation disk. Forging is used in the production of expensive tableware. The technology improves the properties of aluminum: thermal conductivity and strength increase.
The most expensive technology is based on the casting method. Molten aluminum alloy is poured into molds. The technology allows you to completely preserve all the positive properties of aluminum. The walls of the dishes are thick, durable, and difficult to deform.

Important! All kitchen items of complex shape are made by stamping. Cast ware has a simple configuration.

The bottom of a pan, ladle or other product can be multi-layered. The invention is very useful, as it reduces the likelihood of food burning. When overheated, the bottom deforms less and burns out less often. A thick aluminum plate is used as an additional layer. If the cookware is intended for an induction cooker, then an additional plate is installed from a copper alloy.

It has been proven that cooking sour dishes in aluminum cookware is harmful, since the metal releases toxic substances during the reaction. This is where the non-stick coating comes to the rescue. This useful invention was invented not only to prevent burning. Non-stick coating prevents aluminum from coming into contact with food. The dishes retain only their beneficial properties, even when cooking compote or other sour dishes.

Non-stick coating is applied by rolling or spraying. The second layer has more useful properties. The rolled coating is applied to the sheet. After stamping, many microcracks appear. Spraying is performed only on finished dishes. The more protective layers, the better the properties of the non-stick coating and the more benefits it will provide.

There are three types of protective layer:

Ceramics. The protective layer has a negative property - it reacts poorly to prolonged contact with liquid. The remaining compote or soup will have to be poured into another storage container.
Teflon. The coating is capricious. It is unacceptable to use metal spoons or ladles to avoid scratches.
Mineral stone. The most practical coating, unless you come across a fake.

Any protective coating is useful, but such dishes become difficult to care for and require more careful storage.

Important! Expensive cookware made of cast aluminum will not cause harm even when preparing acidic food, since it is usually made with a protective coating.

Modern aluminum cookware in everyday life has an attractive appearance. The decorative coating adds beauty. It could be:

enamel;
varnish;
sprayed porcelain suspension that has been fired;
anodizing.

The benefit of decorative coating is maintaining an attractive appearance. There is zero harm to food since there is no direct contact. Decorative coating is applied to the outside of aluminum cookware.

Cheap products don't cover anything. They can only be sanded. A new pan will shine, but after a few uses the sides will become dull.

Marking

Since silumin is an alloy of aluminum and silicon, and also just one of its varieties, a special marking has been developed that allows you to quickly and easily determine the percentage of components, as well as which chemical elements were used in the manufacture of the alloy. In order to mark the silumin alloy, alphabetic and numerical designations are used. For example, AK12 or AK9TS7. The first letter always indicates the aluminum content in the alloy, and the second the silicon content. The numbers indicate the exact percentage of this chemical element in silumin. In this case it is 12%. Since other elements can be added, their letter is also indicated. The second example shows the marking of aluminum - A, silicon - K 9% and zinc - C 7%.

It is also important to note that the alloy has increased fluidity in the molten state, as well as good weldability. If we consider that the melting point of silumin is only 580 degrees Celsius, then this can be included in the list of advantages of the material.

What kind of material is this?

The chemical composition of domestically produced silumins is determined by GOST 1583-93. The alloys in question (aluminum is the base) contain:

Silicon,% – 10...13;
Iron,% - 0.35...0.70;
Manganese,% - 0.03...0.50;
Titanium,% - 0.03...0.25;
Copper,% - 0.02...0.03;
Zinc,% - 0.04...0.08.

Important: in silumins, which are used for the manufacture of food utensils and other products for similar purposes, the content of toxic chemical elements is limited - arsenic (no more than 0.015%), lead (no more than 0.15%) and beryllium (no more than 0.0005%) .

Silumins have less weight than regular aluminum or other competitors, in particular steel or titanium. The addition of high-purity silicon provides the metal with a lower coefficient of thermal expansion, improving the fluidity of the foundry melt. Finally, silicon reduces shrinkage as the alloy solidifies, adding ductility and strength.

Types of silumin

Most often they say that silumin is an alloy of aluminum and silicon. However, this is not an entirely true statement. This name is given to alloys in which the content of an element such as silicon is in the region of 12-13%. This group of alloys is usually called eutectic, normal or ordinary silumins. However, there is another classification of this material.

The first type of alloy is called hypoeutectic. A characteristic feature of this group is that the silicon content as a percentage is only 4 to 10% of the total amount. In addition, elements such as magnesium, manganese or copper can be added.
A group of wear-resistant silumins - the silicon content increases to 20% of the total alloy.
To perform specific tasks, special silumin alloys are made, for example, zinc alloys.

Reviews

Irina Petrovna Usikova, 49 years old, Tula

I used a set of stainless steel pans for a month. Did not like. Food constantly burns, despite the double bottom. Water takes a long time to boil. Returned to traditional aluminum. I try not to think about the harm. It is not yet known what kind of stainless steel Chinese pans are made of.

Olga Aleksandrovna Vishnevskaya, 37 years old, Novosibirsk

I always buy thick-walled aluminum pans. There are simple ones and non-stick ones. Somehow the stainless steel didn't work. I don’t feel any harm from aluminum on my health. My grandmother used it all her life and nothing was wrong, everything was fine.

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Properties of normal silumins

The first group of aluminum silumins are eutectic. Their strength parameters are quite small, but the advantage of this type is different. They have excellent casting parameters. Materials from such an alloy are used in the casting of thin products, which in the future will be used in environments with increased vibration or under the influence of shock loads.

It is also important to note that when casting this group of alloys, requirements such as elongation of the microstructure may be imposed on it. To fulfill this requirement, it is necessary to modify silumin with sodium during the casting operation into a chill mold or into a mold.

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It is also important to note that only those characterized by high purity of the composition are highly resistant to the effects of aggressive environments on the alloy. In other words, such materials must contain a minimum content of various impurities, such as iron and others.

Alloy groups

There are several groups into which silumin is divided. This division is carried out according to the use of this material for various purposes.

Eutectic silumin, which is marked AK12, that is, only 12% silicon content, and is not hardened by heat treatment and does not develop shrinkage strength, is recommended for use for the manufacture of sealed parts of devices or units of low load.

As an example of hypoeutectic silumin, we can take the AK9ch alloy. For its manufacture, hardening is already used at a temperature of 530 degrees with a holding time of 2 to 6 hours. After this, the material is cooled in hot water and the aging process is activated at a temperature of 175 degrees, which lasts for 15 hours. The use of silumin of this group is carried out for the manufacture of loaded and large-sized parts.

The third group of alloys is highly alloyed hypereutectic silumin, marked AK21M2. This material belongs to the piston group of alloys. This material is intended for use in environments with elevated temperatures, as it has increased heat resistance and a high wear resistance coefficient.

How to choose a silumin mixer?

To purchase a suitable silumin faucet or mixer, you need to decide on the location of its installation: kitchen or bathroom; Designed for sinks, washbasins, bathtubs, bidets or shower stalls. As a rule, silumin taps are selected with a high jib, under which it is convenient to slide various kitchen utensils. To save space in the work area, you can choose a model with a wall mounting method.

Washbasin devices are characterized by compact dimensions, which is due to the small size and depth of the former. An exception is products for counter-mounted sinks, where the mixer is installed on the countertop and has an increased body height. A characteristic feature of silumin faucets for bidets is the presence of a rotary aerator. With its help, you can easily adjust the flow in the desired direction.

In addition to their purpose, mixers differ in how they are controlled.

Single lever . The water pressure and temperature are adjusted using a cartridge mechanism. For setting, the user has access to only one lever, which, when lifted up, opens the supply, and when turned left/right, changes the ratio of cold and hot water.
Two-valve . These faucets are equipped with two faucet axle boxes: one is responsible for supplying cold and the second hot water. To adjust the temperature in this type of plumbing fixture, both taps must be turned.
Thermostatic . A special mechanism is responsible for maintaining temperature and pressure. The user only needs to configure all parameters once, after which the mixer automatically adjusts to them every time the supply is opened.

The last parameter that you definitely need to pay attention to is coverage. The top decorative layer is chrome or paint. In the first case, you get a classic plumbing fixture with a characteristic shine. Painted faucets are available in black, white, brown, and beige. They are chosen for rooms stylized to a specific design.

Repair

Since it may happen that cracks or breaks appear on parts made of this alloy, it is possible to carry out repair work. Most often, a special substance is used to carry out this type of work - epoxy glue. However, if the part must be used in an environment with increased loads, it is best to use welding. However, it is necessary to take into account the composition of the alloy, since not all of them are able to withstand the operating temperature of the welding machine; some of them may simply melt.

Can I use aluminum cookware on an induction cooker?

Not many people know what kind of cookware can be used for an induction cooker. The developers of this technique recommend buying special dishes that have a flat, weighted bottom, plus magnetism.

Special cookware is suitable for an induction cooker, but not aluminum

Is it possible to use, for example, aluminum cookware for cooking? Of course not. Traditional cookware that we are used to is not suitable for such a stove. You can replace it with kitchen utensils that are made of stainless steel, cast iron, with an enamel surface.

Welding

Repairing silumin at home using argon arc welding is considered the simplest method. However, everyone recognizes that the best solution for repairing parts is to turn to professionals, but independent welding is also quite possible. It is important to note that argon arc welding must be carried out in an inert gas environment.

Most often, argon gas is used directly to achieve this goal, but in some cases it is possible to use a mixture of argon and helium. It is also important to note that after carrying out welding work to repair parts made of silumin, all welding seams must be processed. After this procedure, the stitches will be almost invisible.