FAQ – Frequently Asked Questions
1. What is the difference between iron and steel?
Iron is a white, relatively soft forged metal, chemically quite resilient, while steel is an alloy of iron and carbon, where the carbon content is up to 2.06%.
2. What is the difference between hot and cold rolled sheet?
Apart from the process by which each of these two kinds of steel sheet is produced (cold rolled sheet is more expensive because it uses hot rolled steel as a basis, to which cold rolling is then applied), there are differences in application as well.
Cold rolled sheets are produced from cold rolled coils, which are produced by cold rolling, i.e. reducing the thickness, on continuous (tandem) mills for strip rolling which in tandem can have as many as 5 Sendzimir clusters. Cold rolled sheets are widely used, especially when the product has to have an aesthetically pleasing, smooth and flat surface as part of a finished product.
Hot rolled sheet has scales and various solid inclusions.
3. What is the quickest way to calculate the weight of a single steel sheet?
The thickness of the sheet in millimetres (mm) has to be multiplied by the width and length of the sheet in metres (m) and then the total multiplied by the factor of 8.0, for example:
thickness = 5 mm
width = 1,000 mm = 1 m
length = 2,000 mm = 2 m
factor = 8.0
5 x 1 x 2 x 8 = 80 kg
4. What is the difference between stiffness, hardness, strength and toughness, i.e. the most commonly discussed mechanical properties of materials?
Stiffness is the extent to which material resists deformation.
Hardness is the property of the material which enables it to resist penetration or indentation by another object.
Strength is the capacity of the material to resist any deformation once it is exposed to a load per unit area.
Toughness is primarily the capacity of the material to resist fracture, although, in static terms, it is the ability of the material to deform plastically and permanently before fracture, i.e. it should not fracture suddenly, which enhances the safety of the structure. In dynamic terms, toughness is the measure of resistance of a material to impact, and is expressed as the quantity of energy absorbed by the material when it fractures. Materials that cannot be permanently deformed before fracture are brittle, whereas material that can are called ductile.
5. What is the difference between DC01 and DC03, the two most commonly applied grades of cold rolled sheet?
The DC01 grade can be used mainly for angle bending, whereas the DC 03 grade can also be used for deep drawing.
6. What is the zinc coating that needs to be applied if we want to expose a structure to outdoor atmospheric influences?
The minimum zinc coating must be 200 gr/m2, but in any case it is desirable and advisable to use a zinc coating of 275 gr/m2; this determines the potential duration of resistance to atmospheric influences.
7. What is the maximum allowable thickness deviation for steel sheets?
According to EN 10029, this depends on the sheet thickness; for the 3 mm to 250 mm range, it can be from 0.4% to 1.5%.
8. What are the applications for fine grain (microalloyed) steel?
The purpose of such steel is to reduce the weight of the structure, for instance of a lorry chassis or of ships, bridges, containers, tanks, etc. Under its old name according to DIN, the small grain (microalloyed) steel has a code, for instance, of QSte380TM, where Q stands for high-quality steel, i.e. carbon steel with the minimal addition of alloying elements to enhance yield stress and hardness. It is important to mention that processing by deformation and strength can vary significantly, depending on the direction of rolling.
9. What is the meaning of toughness codes such as JR, JO, J2 or K2 in the following steel names: S235JR, S275JO, S355J2+N and S355K2+N?
- JR - means that the material has to withstand an impact energy of not less than 27 J at +20°C
- JO – means that the material has to withstand an impact energy of not less than 27 J at 0°C
- J2 – means that the material has to withstand an impact energy of not less than 27 J at -20°C
- K2 – means that the material has to withstand an impact energy of not less than 40 J at -20°C
10. What is the difference between the most commonly applied zinc coated sheet grades of DX51D and DX52D?
The difference is that the DX51D grade can be used primarily for angle bending of up to 900, whereas DX52D grade may also be used for round bending.
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