Thermal conductivity against densityHigher and further left: spreads more heat for its weightThermal expansion against thermal conductivityLower and further right: warps less when heated
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Sources6 documents: Cleveland-Cliffs, American Institute of Steel Construction, bauforumstahl (ArcelorMittal), National Institute of Standards and Technology, Ovako
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.
Steel
Generic structural steel, cited as ASTM A992 (the current US structural grade): ASTM A992 W-shapes; Fy/Fu specified minimums from AISC publications (AISC 360-16 Commentary; Modern Steel Construction); elastic constants AISC 360; physical constants from the bauforumstahl structural-steel EPD, which names A992 among covered product standards.
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
Updating Standard Shape Material Properties Database for Design and ReliabilityAmerican Institute of Steel Constructionarchived copySteel · Yield strength: typical: mean of 20,295 A992 flange mill-test coupons (1998 SSPC survey), as reported by AISCSteel · Ultimate tensile strength: typical: mean of 20,295 A992 flange mill-test coupons (1998 SSPC survey)Steel · Elongation at break: typical: mean of 24,847 A992 mill-test elongations, web and flange (1998 SSPC mill data), as reported by AISC
3
ANSI/AISC 360-16 Specification for Structural Steel Buildings, with CommentaryAmerican Institute of Steel Constructionarchived copySteel · Young's modulus (stiffness): design value (AISC 360-16)Steel · Poisson's ratio: design value (AISC 360-16 Commentary)
4
Environmental Product Declaration: Structural Steel Sections and Merchant Bars (2023)bauforumstahl (ArcelorMittal)archived copySteel · Density: nominal (constructional data)Steel · Thermal conductivity: nominal at 20 °CSteel · Thermal expansion: nominal (constructional data, no temperature range stated)
5
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)
6
S275JR Steel GradeOvakoSteel · Specific heat: base material: EN S275JR unalloyed structural steel (the EN counterpart of A36), typical, 50/100 °C
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 Steel?
Steel is stronger: its yield strength is 385 MPa against 186 MPa for Iron (2.07x).
Which is lighter, Iron or Steel?
Steel is lighter: 7,850 kg/m³ against 7,860 kg/m³ for Iron.
Which is stiffer, Iron or Steel?
Iron is stiffer: Young's modulus 207 GPa against 200 GPa for Steel, so the same part in Iron deflects less under the same load.
Which is lighter for the same job, Iron or Steel?
For the same stiffness or strength: Iron is lighter for a stiff rod or tie (tension), stiff beam (bending), stiff panel or plate; Steel is lighter for a strong rod or tie, strong beam, strong panel or plate.
Part that must be
Iron
Steel
Stiff rod or tie (tension)
lighter
3% heavier
Stiff beam (bending)
lighter
2% heavier
Stiff panel or plate
lighter
1% heavier
Strong rod or tie
2.07x heavier
lighter
Strong beam
1.63x heavier
lighter
Strong panel or plate
44% 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 Steel?
Iron stretches further before it breaks: 38% elongation at break against 24.2% for Steel.
Thermal
Which conducts heat better, Iron or Steel?
Iron conducts heat better: 73.2 W/m·K against 48 W/m·K for Steel.
Which expands less with temperature?
Steel expands less: 12 µm/m·K against 13.7 µm/m·K for Iron.