How steel chain is made

Each link is bent from a rod, threaded through the one before it, and only then welded shut.

stations: 7
things upstream: 26
raw sources: 12
steps from the ground: 6

The short version

Wire is lubricated and drawn through a die until thin and strong. A machine cuts a length, passes it through the last link and bends it around a form with its arms, closing a new link. The cut is welded shut. The whole chain then runs through a coil to 940 °C, is quenched in water, reheated more gently and cooled again, and is finally calibrated to exact link size.

Draw the wire

Wire unwinds from a coil, passes a lubricant box and is pulled through a die narrower than itself onto a rotating drum, which thins and strengthens it.

Goes in
Steel wire
Cut to link length

The straightened wire is sheared by a steel cutter into pieces sized for one link.
Bend through the last link

The piece passes through the previous link, and arms force it around a form. The machine turns the new link upright, and the cycle repeats.
Weld the cut shut

A welder closes the join in each link, so the strand holds together under load.
Harden in water

A heating coil brings the whole chain up to orange heat, and it drops into water. The sudden change in temperature makes the steel hard and brittle.

940 °C
Temper for toughness

A second coil reheats the chain to a lower temperature before another water cooling, giving back some elasticity.
Calibrate the strand

Following heat treatment the strand is calibrated to the right geometry. High grades get a mild final heating that relieves the stress calibration leaves behind.

End of the lineSteel chain

Worth repeating

The Tibetan siddha Thangtong Gyalpo built chain bridges in eastern Bhutan in 1433.
Wire rope grew out of wrought iron chains because a flaw in one link can break the whole chain, while a flaw in one wire matters much less.
A chain is floppy when you push it but acts like a rigid rod when you pull it.