Brands and grades of construction steel
For those who are not very familiar with all the technical details in the field of construction steels, the following question arises: „How do we correctly interpret the notation of some brands and classes of steel defined in letters and numbers?”
The quality standards of construction steels according to EN 10025-2/2004 are the following:
S185
S235JR S235JO S235J2
S275JR S275JO S275J2
S355JR S355JO S235J2 S355K2
This alphanumeric symbolization includes the steel brand (S185, S235, S275, S355) and the corresponding quality class (JR, JO, J2, K2).
Brands and classes of steel – their description
The steel mark contains the symbol S (which refers to the steel group – construction steel) and the number 185, 235, 275 or 355 which expresses the minimum value of the expressed yield strength. Steel brands differ from each other in mechanical characteristics.
Within each steel brand, several quality classes are defined:
JR – quality class for products with the minimum value of breaking energy when bending by shock of 27J at +20 degrees C.
JO – quality class for products with the minimum value of breaking energy when bending by shock of 27J at 0 degrees C.
J2 – quality class for products with the minimum value of breaking energy when bending by shock of 27J at -20 degrees C.
K2 – quality class for products with the minimum value of breaking energy when bending by shock of 40J at -20 degrees C.
The quality classes, which differentiate the steels within the same brands. These highlight, on the one hand, good welding behavior. And on the other hand, the safety of welds and welded parts, by ensuring toughness and avoiding brittle breaks. The steels of the quality classes JR, JO, J2 and K2 generally have welding capacity for all welding processes. Weldability increases from JR to K2.
Not all types of steel are weldable. The chemical composition of the alloy influences its behavior during welding. The higher the carbon content in the chemical composition of the steel, the more delicate the welding becomes.
When choosing the quality class of steel, when executing welded metal constructions, you must take into account:
– the nature of the requests;
– the thickness of the product;
– the construction temperature.
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