A hot rolled coil is a semi finished product, not a sheet
A hot rolled coil leaves the mill at 2 to 8 mm, coiled hot, then annealed and pickled. It is the input to almost every cold rolled product: the cold mill takes a 3 mm hot band and rolls it to 1 mm or 0.5 mm. That is why the price of a cold rolled sheet tracks the hot band price with a rolling conversion on top, and why a buyer who understands the hot coil market understands where the cold price is going.
For a fabricator, a hot rolled coil is bought for two reasons. Either the finished part is thick enough that cold rolling adds nothing (a 4 mm tank shell, a 6 mm structural bracket), or the part will be slit into strip and formed without any surface requirement that needs cold rolling.
The grades on this page are the common ones: 201 and 304 for general work, 316L for chloride, 430 for magnetic and appliance applications, and 310S when the part sees high temperature.
No.1 finish means annealed and pickled, and that is the whole point
A hot rolled coil straight off the mill carries a dark oxide scale that is abrasive, electrically resistive and impossible to weld through. No.1 finish is the process that removes it: the coil is annealed to soften the hot rolled structure, then pickled in acid to dissolve the scale, then rinsed and usually brushed.
The result is a grey, matte, slightly rough surface with a Ra around 2 to 3 micrometres. It is not decorative and it is not meant to be. It is a clean, weldable, formable surface, and it will show roll marks and a certain amount of colour variation from coil to coil.
Two failures are worth watching for. An under pickled coil has patches of residual scale, usually along the edges where the coil was tighter, and those patches become corrosion sites under a coating. An over pickled coil has a roughened, pitted surface from excessive acid exposure, which shows up as a poor weld bead and a rough finish after blasting.
Coil parameters that decide whether it will run on your line
Inner diameter. 508 mm and 610 mm are the two standards. A 508 mm coil will not mount on a 610 mm mandrel without an adapter, and the adapter changes the pay off geometry. State the mandrel size, not the coil ID you think you need.
Coil weight. 3 to 5 tonnes is a slitting or cut to length coil; 15 to 25 tonnes is a mill coil for a service centre. A small fabricator with a 5 tonne uncoiler cannot take a 20 tonne coil, and re-coiling it costs more than buying the right size.
Coil OD and width. Both are constrained by the line and by the container. A 1500 mm wide coil at 20 tonnes will not fit through a standard door on a forklift.
Edge. Mill edge for a coil that will be slit downstream; slit edge for a coil that goes straight to a roll former.
Camber and coil set. A hot rolled coil can carry a memory of the coiling curvature, called coil set, which shows as a lengthwise bow when the strip is uncoiled. Tension levelling removes it; nothing else does.
Specification
| Parameter |
Value |
| Grade |
201, 304, 304L, 316L, 321, 310S, 430, 409L |
| Thickness |
2.0 to 8.0 mm hot rolled |
| Width |
1000, 1219, 1500 mm, slit to order from 20 mm |
| Finish |
No.1 annealed and pickled, or mill finish |
| Inner diameter |
508 or 610 mm |
| Coil weight |
3 to 20 tonnes, or cut to a stated weight |
| Edge |
Mill edge or slit edge |
| Standard |
ASTM A240, A480, EN 10028-7 |
| Inspection |
TUV or BV third party, EN 10204 3.1 |
Cut length is available directly from coil: the coil is uncoiled, levelled, cut on a flying shear and stacked. That is normally the cheapest way to buy a flat 4 mm sheet, because it avoids the handling of a mill plate.
Slitting a master coil into strip
A slitting line takes a master coil, cuts it into several narrower coils in one pass, and rewinds them on separate mandrels. The economics depend on how well the widths nest: a 1500 mm master coil slit into five 300 mm strips wastes nothing, while the same coil slit into three 400 mm strips leaves 300 mm that has to be sold as a narrow width or scrapped.
This is why a strip price is not simply the coil price divided by weight. The slitting yield, the knife set up, and the number of coils produced all move the number. If the width is unusual, tell us the annual quantity; a width that can be nested with another customer's order is cheaper than one that runs alone.
What the TUV or BV certificate actually covers
Third party inspection means an independent body has witnessed the test, not that the material has been redesigned. In practice the inspector confirms the heat number against the mill certificate, witnesses the tensile and yield test, checks the chemical composition, and sometimes witnesses the dimensional check and the visual inspection.
What it does not cover is the thing buyers most often assume: it is not a guarantee that every square metre of the coil is defect free. For that you need a surface inspection report or an agreed defect acceptance standard, and those are separate agreements. Say which one you need at the enquiry stage, because the inspection charge is per coil visit and adding it later means a second visit.
Frequently asked questions
Can you supply a 2 mm hot rolled coil?
Yes, 2.0 mm is the thin end of the hot rolled range. Below that it becomes cold rolled.
Is No.1 finish suitable for a visible surface?
No. It is a working surface. For visible work, specify cold rolled 2B or a polished finish.
What is the minimum coil order?
One coil, typically 3 to 5 tonnes for a slit coil.
Do you supply cut sheets from coil?
Yes, levelled and cut to length, which is usually the cheapest route to a flat sheet under 8 mm.
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