Flat steel: hot-rolled (HRC), cold-rolled (CRC) and galvanised (HDG)
HRC is made by rolling slab at around 1,100 °C to 1.2–25 mm; its surface carries scale, and it is used for pipe, sections, ships and structures and is the main benchmark of global steel prices. Pickling HRC and reducing it at room temperature to 0.2–3 mm gives CRC, with a smoother surface and tighter tolerances for appliances and automotive. Hot-dip zinc coating of CRC gives galvanised sheet (GI, DX51D+Z), aluminium-zinc gives Galvalume (AZ), and painting gives pre-painted steel (PPGI).
Related terms
Steel grade designation (EN, ASTM, AISI, JIS, GB)
Steels carry different names in different standard systems. In the European system (EN 10027) a letter shows the use and a number the minimum yield strength: S235JR is a structural steel with 235 MPa and impact tested at 20 °C, while S355J2 is tested at –20 °C. Approximate equivalents are ASTM A36 or A572 Gr.50, JIS SS400 in Japan and GB Q235/Q355 in China; for stainless, AISI 304 ≈ EN 1.4301. Equivalents are not identical, so chemistry and mechanical values should be checked on the certificate.
Coating weight (Z100, Z275, AZ150)
For galvanised and Galvalume sheet it shows the total coating on both surfaces in g/m² (EN 10346): Z275 means 275 g/m² of zinc on both sides together, roughly 20 µm per side. Coating weight directly determines corrosion life: Z100–Z140 is typical for indoor and appliance use, Z200–Z275 or AZ150 for roofing, cladding and outdoor use. Price rises with coating weight, so it must always be stated in offers and verified on the certificate.