Ferrite
BCC ironSoft matrix in low-carbon steels; ductile, magnetic, limited strength.
Darker cells mean a higher score for this topic on that metric.
Strength88
Heat resistance72
Fire performance84
Insulation8
Workability80
Circularity64
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Last reviewed Sources & creditsMedia creditsMethodology
Quick answers
Is steel non-combustible?
As a metal it is Euroclass A1, but it loses yield in fire and usually needs protection for a rated duration.
Steel vs iron?
Steel is iron with controlled carbon (typically <2%) and alloys; cast iron has more carbon and a different solidification path.
Does steel insulate?
No. Thermal conductivity is tens of W/m·K. Insulation is a separate layer (mineral wool, boards, VIP).
Why does steel rust?
Iron oxidises in the presence of water and oxygen. Alloys, zinc, paint or concrete cover slow that.
Is stainless “stainless” forever?
No. Chlorides, crevices and wrong grades pit. 304 vs 316 is a chemistry choice, not a slogan.
Can steel be recycled endlessly?
Magnetically, yes as a family. Copper contamination and coatings constrain some high-spec loops.
heat 72 · fire 84
What holds Steel together is not the nickname. Formula Fe–C (±Mn, Si, Cr…), density 7.85 g/cm³.
Meters are atlas-relative. Grades are the SKUs buyers write.
Phases
Pearlite
Fe3C + ferrite lamellaeThe classic strengthening mix in medium-carbon steels after slow cool.
Austenite
FCC ironHigh-temperature phase; retained in some stainless and TRIP steels.
Martensite
BCT supersaturatedQuench product; hard, needs tempering for toughness.
Cementite
Fe3CHard carbide that pins dislocations; too much makes steel brittle.
Inclusions
MnS, oxidesNon-metallic particles that start fatigue cracks if not controlled.
Relative meters
Strength88
Strength is an editorial 0–100 mark relative to the other 31 materials in this atlas — not a laboratory certificate.
Heat envelope72
Heat envelope is an editorial 0–100 mark relative to the other 31 materials in this atlas — not a laboratory certificate.
Fire behaviour84
Fire behaviour is an editorial 0–100 mark relative to the other 31 materials in this atlas — not a laboratory certificate.
Insulation8
Insulation is an editorial 0–100 mark relative to the other 31 materials in this atlas — not a laboratory certificate.
Workability80
Workability is an editorial 0–100 mark relative to the other 31 materials in this atlas — not a laboratory certificate.
Circularity64
Circularity is an editorial 0–100 mark relative to the other 31 materials in this atlas — not a laboratory certificate.
Grades
S235 / A36
Mild structuralMild structural
S355
Higher-yield structuralHigher-yield structural
1045
Medium carbonMedium carbon
DP600 / DP800
Dual-phase AHSSDual-phase AHSS
Corten / weathering
Patina steelPatina steel
Bonds
Metallic bonding
Delocalised electrons give ductility and electrical conductivity.
Fe–C interstitial
Carbon in octahedral sites hardens iron far more than its weight share suggests.
Grain boundaries
Hall–Petch strengthening: finer grains raise yield without losing much toughness.
Precipitates
Carbides and copper-rich clusters pin dislocations in HSLA and ageing grades.
Change the grade, the coating or the moisture and you have a different material with the same English name.
Keep exploring
More in Metals
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Overall 59 ✈️Titanium
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Chromium passive films that keep kitchens, chemical plant and façades from rusting like carbon steel.
Overall 64