Skip to content Skip to a section

🔩How it is made

Steel · The iron–carbon workhorse of buildings, ships, rails and tools — endlessly recast.

At a glance
Score intensity

Darker cells mean a higher score for this topic on that metric.

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

Start with this section - How it is made

Making Steel is a chain: feedstock, conversion (bloomery c. 1800 BCE / Bessemer 1856), forming, heat, finish, install.

Skip a step and the properties chapter is describing a different object.

Process steps

01 Ironmaking

Blast furnace or DRI turns ore + reductant into hot metal or sponge iron.

02 Steelmaking

BOF or EAF adjusts carbon, phosphorus and alloys, then vacuum degasses if needed.

03 Casting

Continuous casters freeze slabs, blooms or billets.

04 Hot rolling

Reheat and reduce to plate, strip, sections or rod.

05 Cold mill / heat treat

Skin pass, anneal, quench-and-temper or galvanize.

06 Fabrication

Cut, weld, bolt, form — residual stress and HAZ hardness become the real spec.

Routes

BF–BOF

Primary ore route; high CO₂ unless CCS or hydrogen later.

EAF scrap

Mini-mills recycle steel with electricity; residual copper limits some grades.

DRI–EAF

Gas or hydrogen reduction plus arc furnace — the green-steel bet.

Foundry

Cast steels and irons for complex shapes that rolling cannot make.

Diagrams

Steel process path

Feedstock to installed product.

  1. Feed — in
  2. Convert — mill
  3. Form — shape
  4. Finish — coat
  5. Install — out
  6. Spec — code
  7. Scrap loop — rec

Steel heat & fire

Energy in, class out.

  1. Heat — in
  2. Steel — mat
  3. λ / char — out
  4. Ignition — fire
  5. Euroclass — class
  6. Assembly — sys

Hard limits

Corrosion

Plain carbon steel rusts unless coated, alloyed or kept dry.

Fire softening

A1 does not mean “safe in a blaze”; protection is a separate layer.

Weld HAZ

High carbon equivalents crack unless preheat and hydrogen control are real.

Process energy and scrap quality belong in the carbon passport, not in a footnote.

Keep exploring

More in Metals