A group of cast alloys, the basis of which is aluminum, containing silicon from 4 to 22%, is called silumin. Alloys are highly resistant to corrosion in humid environments and sea water. The composition of silumin (alloy) also includes a small amount of impurities of manganese, zinc, titanium, iron, copper and calcium. They have good casting and mechanical properties, they are easy to cut. The appearance of the material is more reminiscent of cast iron, and it is difficult to recognize it without having experience with it.
Basic properties
Its properties are often compared with steel (stainless). It should be noted that in comparison with the latter it has a lower specific gravity. Silumins are alloys of aluminum with silicon. They have the following properties:
- specific strength. The performance of the alloy and steels are close in value, but, given that the weight of silumin is less, the constructions from it are more advantageous;
- resistance to wear;
- anti-corrosion. A protective film forms on the surface of the metal, which protects it from the negative effects of the environment;
- low specific gravity of 2.8 g / cm 3 ;
- ductility. When casting in alloy molds, parts having complex configurations are obtained. Thanks to good fluidity, the casting process is cheaper;
- low melting point. It is approximately 600 degrees Celsius, which is significantly lower than the melting temperature of steel. This property also affects casting and reduces the cost of work;
- affordable price.
The listed properties of silumin (alloy) show that this material is beneficial to use in the manufacture of various products. However, it should be noted that it has increased fragility. When dropped, a part made from silumin may crack.
Marking
Silumins are aluminum-based alloys. They add silicon and some other elements to improve properties. For quick and accurate selection of material with a certain composition and percentage of incoming elements, alloy marking was developed.
It includes a combination of numeric and alphabetic characters. The letters indicate the constituent components, and the numbers indicate their percentage, except aluminum. The letters are arranged in descending order of the percentage of the element. The record AK12C3 means that the alloy contains 12% silicon, 3% zinc, and everything else - 85% - aluminum.
Types of silumin
Silumin in non-ferrous metallurgy are divided into:
- Deformable (pre-eutectic and eutectic). In casting, pre-eutectic alloys use 4–10% doped only with silicon. Sometimes a small amount of impurities from copper and manganese is allowed. Eutectic has about 13% silicon.
- Foundry (hypereutectic). They have increased fluidity, which ensures the manufacture of castings having a complex shape and thin walls, low shrinkage, and a low tendency to form cracks. The silicon content reaches up to 20%.
Repair of products from silumin
Silumin is an alloy with increased fragility, therefore, products from it can crack during operation.
To restore them, use epoxy glue. The appearance will be restored, but use it under heavy loads is not worth it. For bonding:
- degrease the place where the glue will be applied, allow to dry;
- to spread glue according to the attached instruction and to put on a fat-free surface;
- tightly connect the broken parts and forget about them for a day.
Welding Repair
In some cases, it is better to weld the damaged product. This procedure is carried out independently at home or consult a specialist. During work, the temperature of the material rises, as a result of this, an oxide film appears on the alloy, which prevents the parts of the product from joining. To eliminate these negative phenomena, argon is used for welding, which provides protection from negative factors. For work it is necessary:
- prepare non-consumable tungsten electrodes and solder for welding aluminum structures;
- degrease the surface;
- fix the product;
- heat up the surface to 220 degrees Celsius. To remove heat, put the welded part on a steel gasket;
- weld a seam using alternating current;
- to make seams for aesthetics of appearance.
The product is ready for use under light loads.
Application
Low cost combined with manufacturability makes it possible to use silumin alloy, which includes aluminum with silicon, to be widely used in the national economy:
- mechanical engineering - pistons, parts for the body, cylinders, engines;
- aircraft industry - cylinder blocks, pistons for cooling, aviation units;
- weapons business - boxes for trunks, components for air rifles;
- gas turbine equipment - generators, heat exchangers;
- the manufacture of household appliances - pots, pans, cauldrons, cauldrons, smokehouses;
- sculptural technique.
Silumin (alloy) may contain additives of zinc, titanium, iron, potassium, copper in small quantities. All its brands have significant casting qualities, fluidity, and are simply welded. The alloy is characterized by wear resistance and strength, but it is a brittle material. Silumin products withstand a large load, but can fall if dropped. This is the main disadvantage of the material.
Alloy groups
There are several groups of silumin associated with its use:
- Eutectic. Its marking AK12, refers to casting alloys, contains 12% silicon. It is characterized by resistance to corrosion, small casting shrinkage, significant hardness, and tightness. It is used for casting equipment, parts of equipment, devices of complex shape. Due to fragility, it is not recommended to cast critical parts for work under load.
- Pre-eutectic. Marked AK9ch, has high casting technological properties, corrosion resistance and mechanical strength. It is used for the manufacture of complex parts of large and medium size. Preserves properties at temperatures up to 200 degrees Celsius. Oversized parts from it work under heavy load.
- Hypereutectic. Highly alloyed alloy AK21M2 is characterized by high heat resistance and wear resistance. Used for the manufacture of shaped castings. It is used for the manufacture of pistons operating in an environment of elevated temperatures.
Conclusion
Silumin is an alloy in which aluminum is the main element. The addition of silicon makes the material hard and durable. Upon receipt of silumin casting does not form cracks. There is not a single sector of the economy where aluminum alloys are not used.
Silumin is used for the manufacture of firearms, spare parts for cars, motorcycles, ships, dishes. All alloys of aluminum with silicon are called silumin. And they all have different properties. This depends on the content of silicon in the composition of silumin (alloy), which can be 4–22% of the total volume. The more it is in the alloy, the harder it is, but at the same time it becomes more fragile.