Aluminium circle, Dnipropetrovsk region.

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In accordance with GOST 21488-97, an aluminum circle is a rod of round cross-section made of aluminum grades AD1, AD0, AD, as well as its alloys AMC, AD31, D16, D1, AK8, AK6, AK4-1, AK4 and others. The standard length of the circle is 0.5-6 meters, and the diameter is from 8 to 400 mm. Such a circle is a relatively cheap, light material and is easily machined. Thanks to the oxide surface film, it is resistant to the effects of the external environment and to corrosion. It is non-toxic, durable and has a good aesthetic appearance.(//tractor-service.com)
According to a number of indicators, such a circle even surpasses steel: for example, in terms of manufacturability, aluminum is one of the lightest metals in the world, and its alloys with magnesium or silicon are very resistant to seawater.
In accordance with GOST 21488-97, duralumin circles are produced from the following brands: D16T, D16, B95, B95T1. The chemical composition corresponds to GOST 4784-97. Dural is alloyed with Mg, Cu, Mn. Such a circle differs in fatigue strength, viscosity and static strength up to 500 MPa. Compared to steel, it is cheaper and much lighter. Additional heat treatment of such a circle (artificial or natural aging, hardening) allows it to be significantly strengthened. This material is subject to corrosion, so a film made of pure aluminum is applied to duralumin products. Dural circle is indispensable in transport engineering: in the construction of ships, airplanes, cars, light and strong frame structures are made from it."