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Material World
Industry

Automotive manufacture

The industry that buys more of most engineering materials than any other, and changes them faster than any other.

Building road vehicles at a scale that makes it the largest single consumer of steel, aluminium, glass, rubber and a great many polymers. A modern car contains perhaps thirty thousand parts and thirty distinct material families, and the reason is that almost every component is optimised against a different constraint — crash energy, corrosion, temperature, weight, cost per unit at a million units a year.

It is the industry where material substitution happens fastest and most visibly, because a gram saved is multiplied by production volume and by every kilometre the vehicle is driven.

History

Mass production dates from Ford's moving assembly line in 1913, which changed materials as much as manufacturing: a process that could not stop favoured materials that behaved predictably. Steel bodies replaced wood and fabric in the 1920s and 1930s.

The two great material shifts since are lightweighting — aluminium, magnesium, high-strength steel and composites displacing mild steel under fuel economy regulation from the 1970s — and electrification, which has replaced a fuel system and an engine with a battery pack and moved the industry's most acute supply concerns to lithium, nickel, cobalt and graphite.

Economic significance

Around ninety million vehicles a year, and a supply chain deep enough that a shortage of one semiconductor stopped assembly lines worldwide in 2021. That episode is the clearest recent demonstration of a general point about materials: the constraint is rarely the expensive input, it is the one with no second source.

Its material choices propagate. An automotive qualification is expensive enough that a material which wins one tends to become cheap and available for everybody else, which is how carbon fibre, aluminium extrusion and lithium cells all reached other industries.

Medium confidence Weak evidence

How we know: checked recently · only one source, so there is nothing to cross-check it against · stated directly by the source.

How this connects

Where a connection has been confirmed by an outside reference, that reference is named beside it.

uses

  • Steel — alloy · still the majority of a car by mass, and increasingly as high-strength grades that allow thinner sections rather than as mild steel
  • 6000 series aluminium alloy — alloy · space frames and crash structures, where an extrusion can be designed to collapse in a controlled way
  • Zinc die-casting alloy — alloy · the small castings nobody looks at — handles, latches, brackets, and carburettor bodies historically
  • ABS — material · interior trim and instrument panels, and plated ABS for anything that looks like chrome and is not
  • Styrene-butadiene rubber — material · tyre tread, which is the largest single use of any synthetic rubber
  • EPDM — material · every door and window seal, and the coolant hoses — and it is exactly wrong for a fuel line
  • Polyurethane — material · seat foam, which is where most flexible polyurethane foam goes
  • Babbitt metal — alloy · historically in every engine bearing, and displaced by aluminium-tin and polymer-lined shells
  • Casting — process · engine blocks and housings, and die casting for the small parts by the million
  • Rolling — process · the continuous wide strip mill is what made the pressed-steel car body possible
  • Welding — process · a few thousand resistance spot welds assemble a body shell
  • Heat treatment — process · gears, shafts and springs, and case hardening to give a gear a hard face and a tough core
  • Silicon nitride — compound · turbocharger rotors, glow plugs and bearing balls, and it very nearly became an engine
  • Rubber — material · tyres take roughly seventy per cent of all rubber produced
  • Lithium iron phosphate — compound · in standard-range vehicles, which is now most electric cars by unit worldwide
  • NMC cathode — compound · in long-range vehicles, and steadily displaced from standard-range ones by LFP — the largest single materials shift the battery industry has made
  • Electrical steel — alloy · in the non-oriented grades, for traction motor stators — a demand that arrived at the same time as the grid's and competed with it

Sources

  • Material World
    Our own writing
  • Wikidata
    Wikimedia Foundation · Creative Commons CC0 1.0 Universal (public domain dedication)

Questions this page answers

Where it comes from, and what it becomes

Follow Automotive manufacture back to what it starts as, and forward into what it becomes. Each step is a documented one — a real route material takes, not a chain of inference.

Upstream — what it comes from

  • Automotive manufacture → uses (still the majority of a car by mass, and increasingly as high-strength grades that allow thinner sections rather than as mild steel) → Steel → is composed of → Iron → is produced by (as pig iron, high in carbon and brittle until refined) → Smelting → takes as input (as the element removed, not added) → Oxygen → is produced by (the largest output by tonnage, and the reason air separation units sit beside steelworks) → Air separation
  • Automotive manufacture → uses (interior trim and instrument panels, and plated ABS for anything that looks like chrome and is not) → ABS → is produced by (styrene and acrylonitrile polymerised in the presence of polybutadiene rubber, so the rubber phase is grafted in rather than blended) → Polymerisation → takes as input (as vinyl chloride, which is why more than half of PVC's weight is salt rather than oil) → Chlorine → is produced by (at the anode) → Chlor-alkali electrolysis → takes as input (as brine; the salt is the feedstock for both products at once) → Halite
  • Automotive manufacture → uses (every door and window seal, and the coolant hoses — and it is exactly wrong for a fuel line) → EPDM → is produced by (ethylene and propylene copolymerised with a Ziegler-Natta catalyst, plus a few per cent of a diene to give vulcanisation something to work with) → Polymerisation → takes as input (as vinyl chloride, which is why more than half of PVC's weight is salt rather than oil) → Chlorine → is produced by (at the anode) → Chlor-alkali electrolysis → takes as input (as brine; the salt is the feedstock for both products at once) → Halite
  • Automotive manufacture → uses (seat foam, which is where most flexible polyurethane foam goes) → Polyurethane → is produced by (a diisocyanate and a polyol reacting as they are mixed, so the polymer and the finished part are made in the same moment) → Polymerisation → takes as input (as vinyl chloride, which is why more than half of PVC's weight is salt rather than oil) → Chlorine → is produced by (at the anode) → Chlor-alkali electrolysis → takes as input (as brine; the salt is the feedstock for both products at once) → Halite
  • Automotive manufacture → uses (space frames and crash structures, where an extrusion can be designed to collapse in a controlled way) → 6000 series aluminium alloy → is produced by (and the composition window is narrow: the magnesium-to-silicon ratio decides whether the precipitate forms usefully) → Alloying and melting → takes as input (the base metal of both brass and bronze) → Copper → is produced by (as blister copper, refined electrolytically afterwards) → Smelting → takes as input (roasted to drive off sulfur, then reduced to copper) → Chalcopyrite
  • Automotive manufacture → uses (the small castings nobody looks at — handles, latches, brackets, and carburettor bodies historically) → Zinc die-casting alloy → is produced by (aluminium, magnesium and copper into zinc, to a composition tight enough that the name is an acronym of the four ingredients) → Alloying and melting → takes as input (the base metal of both brass and bronze) → Copper → is produced by (as blister copper, refined electrolytically afterwards) → Smelting → takes as input (roasted to drive off sulfur, then reduced to copper) → Chalcopyrite

These are the most distinct paths back. Automotive manufacture can be traced through others besides.