Iron vs. Stainless Steel 316

Compare Iron vs. Stainless Steel 316 strength, stiffness, weight and thermal properties.

IronWrought

Mechanical	Iron	Stainless Steel 316
Yield strength	186MPa1	265MPa242% stronger
Ultimate tensile strength	290MPa1	583MPa22.01x stronger
Elongation at break	38%1	61%21.61x more ductile
Young's modulus (stiffness)	207GPa1	200GPa2
Density	7,860kg/m³1	8,027kg/m³2
Strength to weight	23.7kN·m/kg	33kN·m/kg40% higher
Stiffness to weight	26.3MN·m/kg6% higher	24.9MN·m/kg
Poisson's ratio	0.2823	design value0.34
Shear modulus	80.7GPa5% stiffer in shear	76.9GPa
Bulk modulus	158GPa	167GPa5% higher
Speed of sound	5,132m/s3% faster	4,992m/s

Stiffness against densityHigher and further left: stiffer for its weight

Strength against densityHigher and further left: stronger for its weight

Thermal	Iron	Stainless Steel 316
Thermal conductivity	73.2W/m·K15.01x more heat through a fin	20–100 °C14.6W/m·K2
Thermal expansion	mean13.7µm/m·K120% less	mean16.5µm/m·K2
100 mm part over a 50 °C swing	68.5µm growth20% less	82.5µm growth
Specific heat	450J/kg·K1	at 20 °C450J/kg·K2
Heats up and cools (diffusivity)	20.7mm²/s5.12x faster	4.04mm²/s
Thermal shock resistance	3,447W/m4.2x more resistant	821W/m
Melting point	1,532°C1	melting range1,390–1,440°C2
Max service temperature	not sourced	oxidation871–899°C2

Thermal conductivity against densityHigher and further left: spreads more heat for its weight

Thermal expansion against thermal conductivityLower and further right: warps less when heated

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Sources4 documents: Cleveland-Cliffs, ATI, National Institute of Standards and Technology, Steel Construction Institute

Iron: Cleveland-Cliffs / AK Steel ARMCO Pure Iron Product Data Bulletin (07/2022): Table 1 typical physical properties, Table 2 typical mechanical properties after SRA/recrystallization anneal.
Stainless Steel 316: ATI 316 (UNS S31600), annealed 1.0 mm sheet, ATI technical data sheet (2012); Poisson's ratio from the Nickel Institute/SCI structural stainless design manual

1
ARMCO Pure Iron Product Data Bulletin (2022)Cleveland-Cliffsarchived copyIron · Yield strength: typical (0.2% YS), hot rolled + SRA/recrystallization annealIron · Ultimate tensile strength: typical, SRA/recrystallization annealIron · Elongation at break: typical, gauge 4D0Iron · Young's modulus (stiffness): typical, after SRA/recrystallization annealIron · Density: typicalIron · Thermal conductivity: typical at 20 °CIron · Thermal expansion: mean, 20-399 °CIron · Specific heat: typicalIron · Melting point: typical
2
ATI 316, 316L, 317 and 317L Technical Data Sheet (2012)ATIarchived copyStainless Steel 316 · Yield strength: typical (representative), annealed 1.0 mm sheetStainless Steel 316 · Ultimate tensile strength: typical (representative), annealed 1.0 mm sheetStainless Steel 316 · Elongation at break: typical (representative), annealed, in 2 in. (51 mm)Stainless Steel 316 · Young's modulus (stiffness): typical, in tensionStainless Steel 316 · Density: typicalStainless Steel 316 · Thermal conductivity: 20–100 °CStainless Steel 316 · Thermal expansion: mean, 20–100 °CStainless Steel 316 · Specific heat: at 20 °CStainless Steel 316 · Melting point: melting rangeStainless Steel 316 · Max service temperature: oxidation (scaling) limit in air
3
Elastic Properties of Metals and Alloys, I. Iron, Nickel, and Iron-Nickel Alloys, J. Phys. Chem. Ref. Data 2 (1973)National Institute of Standards and Technologyarchived copyIron · Poisson's ratio: NIST critically evaluated best value (polycrystalline iron)
4
Design Manual for Structural Stainless Steel, 4th Edition (P413)Steel Construction Institutearchived copyStainless Steel 316 · Poisson's ratio: design value (structural stainless steels)

Each number points to the document that states it, with the exact basis. Values without a number are computed from the sourced ones. "Not sourced" means no citable source states it (or only a specification minimum); figures computed from it are left out too.

Questions

Mechanical

Is Iron stronger than Stainless Steel 316?

Stainless Steel 316 is stronger: its yield strength is 265 MPa against 186 MPa for Iron (42%).

Which is lighter, Iron or Stainless Steel 316?

Iron is lighter: 7,860 kg/m³ against 8,027 kg/m³ for Stainless Steel 316.

Which is stiffer, Iron or Stainless Steel 316?

Iron is stiffer: Young's modulus 207 GPa against 200 GPa for Stainless Steel 316, so the same part in Iron deflects less under the same load.

Which is lighter for the same job, Iron or Stainless Steel 316?

For the same stiffness or strength: Iron is lighter for a stiff rod or tie (tension), stiff beam (bending), stiff panel or plate; Stainless Steel 316 is lighter for a strong rod or tie, strong beam, strong panel or plate.

Part that must be	Iron	Stainless Steel 316
Stiff rod or tie (tension)	lighter	6% heavier
Stiff beam (bending)	lighter	4% heavier
Stiff panel or plate	lighter	3% heavier
Strong rod or tie	40% heavier	lighter
Strong beam	24% heavier	lighter
Strong panel or plate	17% heavier	lighter

For the same stiffness or strength, mass scales with density over stiffness (or strength) raised to a power set by how the part is loaded: 1 for a rod in tension, 1/2 for a beam in bending, 1/3 for a panel (the standard material-selection indices).

Which is more ductile, Iron or Stainless Steel 316?

Stainless Steel 316 stretches further before it breaks: 61% elongation at break against 38% for Iron.

Thermal

Which conducts heat better, Iron or Stainless Steel 316?

Iron conducts heat better: 73.2 W/m·K against 14.6 W/m·K for Stainless Steel 316.

Which expands less with temperature?

Iron expands less: 13.7 µm/m·K against 16.5 µm/m·K for Stainless Steel 316.