Stainless steel coil is bought by grade far more often than by temper, and that ordering is backwards for anyone who has to form it. An annealed coil and a half hard coil of the same 304 are the same chemistry on the same certificate, but the second will crack in a deep draw the first handles without comment. Temper, edge condition and surface protection decide whether a coil runs on the press or becomes scrap, and all three belong in the enquiry.

Temper is a processing state, not a grade

Coil and strip in this range is classified by material type across six conditions: soft, deep draw, extra deep draw, quarter hard, half hard and full hard. On the austenitic grades the hardness comes from cold reduction, so the 302 that leaves the mill soft picks up strength and a slight magnetic response as reduction rises, which is why spring temper strip is dimensionally stable but no longer non-magnetic. Ferritic and martensitic grades work differently. 410 and 410S stainless steel coil is noted for high strength, excellent machinability and hardening after heat treatment, so hardness there comes from the quench and temper cycle rather than from how far the mill rolled it. Specify temper by the operation and let the supplier map it back to a condition.

Which grades actually travel as coil

Ferritic 430 stainless steel coil strip is the workhorse of appliance and decorative parts. Its thermal conductivity is better than the austenitic grades, its coefficient of thermal expansion is lower, and it resists thermal fatigue, with titanium added as a stabilising element. Where cost pressure drives the decision, 202 stainless steel coil strip is a low-nickel, high-manganese 200 series grade: manganese runs 7.5 to 10.0 percent, nickel 4.0 to 6.0 percent and chromium 17.0 to 19.0 percent, which places it below 304 on corrosion performance while staying formable and weldable. Anyone moving to 202 for price should check the service environment rather than the certificate, because the reduced nickel is precisely what limits it in chloride and acidic service; the austenitic 304 and 304L coil remains the reference point most enquiries are measured against.

For parts needing spring properties or higher carbon, 302 stainless steel plate is the higher-carbon relative of 304, UNS S30200 to AMS 5516, supplied non-magnetic when annealed and used for stamping and forming items such as flat washers, since cold working raises hardness at the cost of a slight magnetic response. Where service temperature is the constraint, 321 and 321H stainless steel sheets and plates carry titanium as a stabiliser and are intended for prolonged service between 427 and 816 degrees Celsius, where creep and stress rupture performance exceeds 304 and 304L and post-weld heat treatment is normally unnecessary.

Strength rather than corrosion leads to the duplex grades. Duplex stainless steel coil in 2205 and 2507 gives higher strength than the 300 series with better corrosion resistance, and the hot rolled version is a genuinely heavy product: 2507 duplex stainless steel coil is supplied from 1.2 mm to 10 mm in widths of 600 mm to 2000 mm with coil weights up to 40 tonnes, with density listed at 7.93 g/cm3 as for the austenitic range. Grade equivalents for 2507 are S32750, 00Cr25Ni7Mo4N, 022Cr25Ni7Mo4N and 1.4410, and mills use them interchangeably, so quote every one of them on the drawing. A second listing covers hot rolled 2507 duplex stainless steel coil for buyers comparing availability. Where a part is machined from annealed stock and hardened afterwards, 17-4PH annealed stainless steel is the precipitation hardening route: it welds by all standard methods, hardens in a short low-temperature cycle to a yield strength approaching 180 ksi, and is not intended above 572 degrees Fahrenheit.

Slitting, edge and width

Coil is bought at mill width or at slit width, and the two carry different risks. The range spans 0.2 mm to 60 mm thickness and 3.2 mm to 2000 mm width, so almost any strip width is achievable, but a slit edge is a sheared edge: it carries a burr, a small camber and a work-hardened zone, and it is the edge most likely to start a crack in a stretch form. Cold rolled material is commonly offered at 1030, 1250, 1540, 1840 and 2040 mm, with hot rolled at 1000, 1219, 1500, 1800 and 2000 mm, and those are the widths that price best because they are the widths the mills actually roll. Ask for the burr tolerance on a slit edge before committing to a press feed line, and have edge condition stated on the packing list rather than only the width. Coil at these widths also feeds the tube mills that roll and weld hollow sections, which is where square stainless steel pipe originates, so the same width and edge decisions propagate downstream into welded pipe tolerances.

Thickness tolerance is quoted at plus or minus 1 percent, which matters more than it sounds at 0.3 mm. A press set for nominal sees the top of the tolerance band as a heavier blank and the bottom as a lighter one, and both change springback, so fix one point of the band with the supplier and hold it across the programme.

Surface protection between mill and press

Finish is chosen with the steel, and NO.1, 2B, 2D, 2H, 2R, No.4, hairline, Scotch Brite, satin, No.8 and BA are all available on coil and strip. Material that will stay visible normally carries a PVC film, and that film has a shelf life: left on a coil in a humid warehouse the adhesive migrates and the residue is difficult to remove. For 8K and BA surfaces headed for architectural work, write the film type and a maximum storage period into the order, or specify interleaved paper where the surface must stay free of adhesive residue.

Packing follows sea freight rather than internal handling. A 20 ft general purpose container takes roughly 24 to 26 CBM, a 40 ft around 54 CBM and a 40 ft high cube about 68 CBM, which is why coil weight and outside diameter are quoted together; coil weight in this range runs 3 to 10 tonnes or as required.

What to put in the enquiry

Six lines settle most of the price: grade with UNS or EN equivalents, temper expressed as the forming operation, finish, thickness with the point of the tolerance band, width and whether the edge is mill or slit, and coil weight. Minimum order is one tonne and lead time typically 7 to 15 working days after a 30 percent deposit, with supply running to 5,000 tonnes a month across the range. The full programme starts from the stainless steel catalogue, which lists coil, strip, plate and pipe from the same mills.