IS 6911 : 2017Stainless steel plate, sheet and strip - Specification

IS 6911:2017 is the Indian specification for stainless steel sheet and strip — cold-rolled, hot-rolled, and continuously-produced — covering grades from austenitic (304, 316, 321) through ferritic (430, 441) and martensitic (410, 420). It is the procurement and acceptance code for any architectural, kitchen, industrial, or process-equipment stainless application in India.

Typical applications: - Architectural cladding, handrails, façade panels — usually 304 or 316L (marine/coastal) - Kitchen utensils, food-processing equipment — 304 (food contact), 316 (high-acid/chloride) - Roof/wall panels in chemical plants — 316L for chloride exposure, duplex for higher - Decorative interiors, lift cars — 430 ferritic (lower cost, magnetic, less corrosion-resistant) - Cutlery, fasteners — 420 martensitic (hardenable)

The code aligns with ASTM A240/A240M, JIS G4305, and EN 10088-2 conceptually, but Indian designation 'X04Cr18Ni10' (which is 304) uses the BIS naming convention. Cross-reference tables are included in Annex A of the standard.

Indian designation follows the format `X[carbon×100]Cr[Cr%]Ni[Ni%]Mo[Mo%]`. Common equivalents:

• X04Cr19Ni10 ≡ AISI 304 — austenitic; 18-20% Cr, 8-10.5% Ni; C ≤ 0.08%
• X04Cr18Ni10Mo3 ≡ AISI 316 — austenitic; 16-18% Cr, 10-14% Ni, 2-3% Mo; C ≤ 0.08%
• X02Cr18Ni10Mo3 ≡ AISI 316L — low-carbon (≤ 0.03%) variant for weldability/corrosion
• X07Cr17 ≡ AISI 430 — ferritic; 16-18% Cr, no Ni; C ≤ 0.08%
• X20Cr13 ≡ AISI 420 — martensitic; 12-14% Cr, hardenable to ~50 HRC

Key mechanical-property minima (cold-rolled, annealed condition, tested per IS 1608):

| Grade | Rp0.2 (MPa) | Rm (MPa) | A min (%) | Hardness HV max | |---|---|---|---|---| | 304 | 205 | 515 | 40 | 200 | | 316L | 170 | 485 | 40 | 200 | | 430 | 205 | 450 | 22 | 200 | | 420 | 205 | 450 | 20 | 235 |

Mechanical properties are lower than mill-cold-worked stainless (e.g., quarter-hard, half-hard) — those have separate property tables in Annex B.

Finish designations are critical for procurement — visible finish drives both cost and corrosion performance:

• No. 1 — hot-rolled, annealed, descaled; rough matt; used for industrial tanks where visual is irrelevant
• No. 2D — cold-rolled, annealed, pickled; uniform dull matt; general purpose
• No. 2B — cold-rolled, annealed, pickled, light cold-rolled to a smooth reflective finish; most common architectural finish
• No. 3 — coarse polished (80-120 grit)
• No. 4 — fine polished (150-180 grit); the 'brushed stainless' finish on appliances and elevators
• BA (Bright Annealed) — mirror-bright; for visible kitchenware, decorative trim
• No. 8 — mirror polish; lifts, façade signage

Pickling and passivation per IS 6911 Clause 8.4: mandatory for hot-rolled product, optional but recommended for cold-rolled. Inadequate passivation is the #1 cause of premature rust spotting on architectural stainless installed in coastal India — embedded iron particles from grinding wheels or unwashed swarf become initiation sites for chloride-induced pitting within months.

1. Specifying 304 in coastal Mumbai/Chennai/Goa — chloride from sea breeze pits 304 within 2-5 years. Always specify 316L or higher (duplex 2205, super-duplex 2507) for marine atmospheres. Cost premium ~25% over 304; pays back many times in maintenance.

2. Welding 304 without post-weld treatment — heat-affected zone (HAZ) chromium-carbide precipitation between 425-870°C causes sensitization and intergranular corrosion. Either use 304L/316L (low carbon — no precipitation) OR re-passivate with citric/nitric acid post-weld.

3. Using carbon-steel wire brushes on stainless — embeds free iron. Always use dedicated stainless brushes, stainless wool, or non-metallic abrasives. Same applies to angle-grinder discs.

4. Mixing stainless with carbon-steel fasteners — galvanic couple in damp environment; carbon-steel fastener corrodes preferentially and stains the stainless. Use A2/A4 (304/316) stainless fasteners throughout.

5. Confusing 'grade' with 'finish' — 304 No. 4 (brushed) and 304 No. 8 (mirror) are the same grade, same corrosion resistance, different visual. Don't pay mirror-finish premium for hidden structural members.

6. Not specifying pickling on hot-rolled — IS 6911 makes pickling optional unless invoked. Always invoke it for visible installations to remove the dark mill scale (Fe₃O₄) that's both ugly and a corrosion initiation site.

• IS 1608 Part 1:2005 — tensile testing (used to verify Rp0.2, Rm, A)
• IS 1500 Parts 1-3 — hardness testing (Brinell / Vickers / Rockwell)
• IS 6603:2001 — stainless steel bars and flats (companion code for round/flat sections)
• IS 6529:2003 — chromium-nickel-molybdenum austenitic stainless steel plate, sheet, strip (older, partially superseded)
• IS 12379:1988 — corrosion-resistant high-alloy steel bars
• IS 800:2007 — general construction in steel (extended to stainless for composite buildings)
• EN 10088-2 — international (European) stainless flat product spec; engineers often supplement IS 6911 with this for exact chemistry tolerances on imported coils
• ASTM A240/A240M — US equivalent; common on EPC projects with US engineering

IS 6911:2017 is the current revision (replacing IS 6911:1992) and is well-aligned with international practice. The major change in 2017 was the addition of duplex grades (2205-equivalent) and lean-duplex (LDX 2101, 2304) — these are increasingly used in Indian water-treatment plants, urban infrastructure, and bridge railings for the cost/performance sweet-spot between 304/316 and full superaustenitic.

For design-and-build EPC projects: IS 6911:2017 is sufficient for procurement, but most designers also reference EN 10088-2:2014 + EN 1993-1-4 for design rules (since IS 800 doesn't formally extend to stainless). For purely architectural cladding/handrail jobs, IS 6911 grades and finishes are universally accepted by Indian fabricators.

One gap worth knowing: surface roughness Ra values (critical for hygienic stainless in food/pharma) are NOT specified in IS 6911 — refer to EN 10088-2 Annex C or ASME BPE for hygienic-grade surface requirements. IS 6911 only classifies the visible finish category (No. 2B, No. 4, etc.) without Ra limits.