In 1946, Defontaine  created its first industrial application for the flash butt welding process by developing starter motor ring gears for the automotive industry.

Many developments followed, such as starter motor ring gears for trucks and industrial engines, timing rings and flywheel inertia rings.

The Defontaine Automotive Department added the production of flywheels to this range in 1985 by opening its Ben Arous site in Tunisia.

In 2005, all Automotive and Aero-industry Department activities were brought  together in the Rings Department with its two business units: "Rings for Thermic Engines (R.T.E.)" and "Rings for Jet Engines (R.J.E.)".