A steel marking looks like a jumble of numbers and letters, but it is actually fairly easy to read. Here are the basics — so you understand what a supplier is offering and can consciously choose the metal for your product.
How to read the marking
In carbon structural steels, the number after the letters shows the carbon content in hundredths of a percent: steel 20 contains roughly 0.2 % carbon. The more carbon, the harder and stronger the steel, but it welds worse and becomes more brittle.
In low-alloy steels, the letters denote alloying elements and the numbers after them the approximate content. The grade 09Г2С reads like this: about 0.09 % carbon, manganese (Г) about 2 %, silicon (С) up to one percent. It is the manganese and silicon that give this steel its higher strength and resistance to low temperatures.
Stainless steels are more often named by the American AISI standard: AISI 304, 316, 430. Domestic equivalents have their own markings — for example, 12Х18Н10Т is close to 304, where Х is chromium, Н is nickel and Т is titanium.
The most common grades and where they belong
- Ст3, С235, С245 — ordinary structural steels. They weld well, machine easily and are cheap. This is the basis of most frames, chassis, fences and steel structures.
- 09Г2С — low-alloy, stronger than Ст3 and better in frost. It is chosen for loaded assemblies and structures that work outdoors all year round.
- Steel 20, 45 — for machined parts: shafts, axles, bushings. Steel 45 is stronger but welds worse.
- AISI 304 — the all-purpose stainless: food production, kitchens, handrails, decor. Non-magnetic, welds well.
- AISI 316 — the same plus molybdenum, so it resists salts and chemicals better. For coastal areas, pools, chemical environments.
- AISI 430 — a cheaper stainless, magnetic, for dry rooms and decorative elements.
Stainless or galvanized
A frequent question, and the answer depends on the conditions. Galvanized steel is cheaper and holds up well as long as the zinc layer is intact. But any cut or weld destroys the coating along the edge — and that is exactly where corrosion begins. So galvanized steel makes sense for products that are hardly cut or welded after coating.
Stainless steel is more expensive but resistant through its entire body: it can be cut, drilled and welded without losing its protection — provided the welding is done in an argon atmosphere, otherwise the weld zone will still lose its resistance.
How to choose if you don't know the grade
You don't have to be an expert in grades to place an order. It is enough to answer three questions: where the product will be installed (indoors, outdoors, near the sea, in contact with food), what load it will carry, and whether appearance matters. From these answers our engineer will select the metal — and will not specify a more expensive one where ordinary structural steel is enough.
Describe your task through the form on the website — we will suggest a grade and quote the fabrication cost right away.
