Terminology

• 304 / 316: austenitic grades; 304 is about 18 percent chromium ("18/8"); 316 adds molybdenum
• L grade (304L, 316L): low-carbon version of the grade
• Passive film: chromium oxide surface layer that resists corrosion
• Austenitic / ferritic / martensitic / duplex / PH: the five stainless families
• PREN: pitting resistance equivalent number, weighting chromium, molybdenum, and nitrogen
• ISSF: International Stainless Steel Forum

History and demand

Invention

• October 17, 1912: Krupp engineers Benno Strauss and Eduard Maurer patented the austenitic type (Nirosta, later 18/8 or AISI 304)
• 1913: Harry Brearley in Sheffield found a martensitic alloy while seeking a corrosion-resistant gun barrel steel; announced in January 1915 as "rustless steel," later named stainless steel for cutlery
• 1950s and 1960s: AOD refining, continuous casting, and the Sendzimir mill allowed large tonnages at affordable cost

First uses in construction

• 1929: Brearley's alloy, marketed as Staybrite, clad the Savoy Hotel entrance canopy in London; more than 25,000 tons were produced and sold in the United States that year

Sourcing

• 2025 melt shop production was 64.2 million tonnes; China made more than 40.8 million tonnes, 64 percent; Europe more than 5.6 million tonnes and the United States about 2.1 million (World Stainless Association via Recycling Today)

Demand trend

• Rising: world melt shop production was 64.2 million tonnes in 2025, up 2.1 percent from 2024, and 15.8 million tonnes in Q1 2026, up 2.5 percent (World Stainless Association); flat and long output was 38.5 million tonnes in 2013
• Austenitic grades are about two-thirds of production

Composition and production

Raw materials

• Iron with at least 10.5 percent chromium
• Type 304 (UNS S30400): chromium 17.5 to 19.5 percent, nickel 8.0 to 10.5 percent, carbon 0.07 percent maximum

Grades and types

• Austenitic (304, 316): largest family, about two-thirds of production; nonmagnetic face-centered cubic structure
• Ferritic (430): magnetic, 10.5 to 27 percent chromium, little or no nickel; ISSF states Type 430 can often replace 304 in non- or lightly corrosive interiors
• Martensitic: magnetic, hardenable by heat treatment
• Duplex: mixed austenite-ferrite structure with roughly twice the yield strength of austenitic grades
• Precipitation hardening: defined by heat treatment
• 316 over 304: recommended for marine or heavily polluted sites; molybdenum improves the passive film

Properties

Physical

• Density: 7.5 to 8.0 g/cm³ by alloy (about 468 to 499 lb/ft³); Type 304 0.285 lb/in³

Mechanical

• Type 304 yield strength: 30 ksi minimum (ASTM A240)
• Type 304 tensile strength: 75 ksi minimum
• Type 304 elongation: 40 percent minimum
• Type 304 hardness: 92 HRB maximum
• Type 304L (ASTM A240): yield 25 ksi, tensile 70 ksi minimum

Fire behavior

• Melting range: 2,417 to 2,786°F (1,325 to 1,530°C) by alloy

Standards

Material specifications

• ASTM A240: chromium and chromium-nickel stainless plate, sheet, and strip
• ASTM A480: general requirements for flat-rolled stainless products, including finishes
• AISC 370: structural stainless steel (austenitic and duplex)
• ASCE 8: cold-formed stainless steel structural members

Uses in buildings

Building elements

• Domestic Water Piping: press-fit tube and fittings
• Drinking Fountains and Bottle Fillers, Lavatories and Sinks: basins and bubblers
• Floor Drains and Cleanouts: bodies and strainers
• Water Heaters, Hydronic Boilers: storage tanks, condensing heat exchangers, and Category IV vent systems
• Automatic and Revolving Doors, Frameless Glass Doors: cladding, fittings, and rails
• Standing Seam Metal Roofing, Metal Wall Panels: roof panels and wall cladding

Pros and cons

Pros

• Passive film resists corrosion without coatings
• Wide grade range for corrosion, strength, and cost
• Duplex grades offer roughly twice the yield strength of austenitic grades
• Recyclable

Cons

• Nickel content ties price to the nickel market
• Type 304 is not recommended for marine or heavily polluted sites; 316 is
• Ferritic grades are limited to non- or lightly corrosive interiors

Finishes and treatments

• Mill, brushed, and polished finishes: flat-rolled finishes defined in ASTM A480
• Passivation: restores the chromium oxide film after fabrication

Sustainability

Embodied carbon

• Outokumpu 2023 stainless output: 1.52 kg CO2e per kg, against a cited global average of 7 kg CO2e per kg (producer announcement; not an industry-average EPD)

Recycled content and end of life

• Fully recyclable

Manufacturing and cost

Main manufacturers and suppliers

• Outokumpu
• ATI
• Cleveland-Cliffs
• North American Stainless

Trade association: Specialty Steel Industry of North America.

Sources

• Wikipedia: Stainless steel, https://en.wikipedia.org/wiki/Stainless_steel
• World Stainless Association: melt shop production 2025, https://worldstainless.org/media/press-releases/stainless-steel-melt-shop-production-increases-by-2-1-in-2025/
• ATI: ATI 304 austenitic stainless steel, https://www.atimaterials.com/Products/ati-304
• ATI: ATI 304L austenitic stainless steel, https://atimaterials.com/Products/ati-304l
• ISSF: Building interiors, the ferritic solution, https://extranet.worldstainless.org/Files/issf/non-image-files/PDF/ISSF_Building_interiors_The_Ferritic_Solution.pdf
• Ancon: The use of stainless steel in construction, https://www.ancon.co.uk/downloads/127/The_Use_of_Stainless_Steel_in_Construction.pdf.pdf
• UpCodes: 2024 IBC Chapter 22 steel, Chapter 22 Steel: Department of Defense Building Code 2024 | UpCodes
• UpCodes: 2024 IBC Chapter 15 roof assemblies (Table 1507.4.3), Chapter 15 Roof Assemblies and Rooftop Structures: Department of Defense Building Code 2024 | UpCodes
• Tube & Wire trade fair news: Outokumpu environmental product declarations, https://www.tube-tradefair.com/en/Media_News/News/Industry_News/Outokumpu_presents_Environmental_Product_Declarations_to_promote_a_sustainable_stainless_steel_supply_chain
• Wikimedia Commons: Stainless steel 1.4034 X46Cr13 bearing ball 60mm G100.jpg, photo by Lucasbosch (CC BY-SA 3.0), https://commons.wikimedia.org/wiki/File:Stainless_steel_1.4034_X46Cr13_bearing_ball_60mm_G100.jpg
• Recycling Today: stainless steel production, China, Europe, USA, 2025, https://www.recyclingtoday.com/news/stainless-steel-production-china-europe-usa-2025