The result of 30 years of Cambridge research, Super Bainite is the world's first bulk nanostructured metal. Now rolling off Tata Steel's Port Talbot mills, Super Bainite has brought back high performance steel armour production to the UK after a gap of 20 years.

Our research revealed a way of producing Super Bainite steel at temperatures more commonly associated with cooking pizza than treating steel

Professor Harry Bhadeshia, University of Cambridge

This cutting edge UK invention and the manufacturing agreement mean that the UK now has its own onshore supply of high-performance armour steel

Professor Peter Brown, MOD

The impact

Super Bainite was invented by Dr Francisca Caballero and Professor Harry Bhadeshia of the Department of Materials Science and Metallurgy in collaboration with researchers at the UK's Defence Science and Technology Laboratory (Dstl) and Tata Steel. Ploughshare Innovations and Tata Steel licensed Super Bainite in 2011, allowing the steel giant to manufacture and process it in the UK and Europe, as well as export it globally.

With a higher density of interfaces than any other type of metal, Super Bainite is the world’s first bulk nanostructured metal. And as Professor Peter Brown of the UK Ministry of Defence (MOD) demonstrated, in its perforated form the Super Bainite has a ballistic resistance superior to established armour materials.

The challenge

Since emerging from the Iron Age 4,000 years ago, steel is central to the world's industrial economy. And from the Bessemer and open-hearth process to Super Bainite, British science and engineering have underpinned technological advances in steel.

Although steel consists primarily of iron and carbon, it has myriad properties that depend on the type or amount of other elements added to the mix, and the temperature at which the steel is produced.

While making steel supremely versatile, this complex composition and cooking mean that for researchers, understanding and designing steel from the atomic level is a complex problem.

Bainite is a structure that forms when austenite – a high-temperature phase of steel – is cooled to temperatures between 250 and 500°C. As it cools, austenite's structure changes; carbides form and slender crystals of iron are incorporated into the structure, so although the bainite is hard, its carbides make it brittle and prone to cracking – a major challenge to solve.

The research

Working in collaboration with MOD's Brown, Bhadeshia and Caballero set out to refine and enhance bainite's properties. They discovered there is no lower limit to the temperature at which bainite can be produced. By heat-treating it at temperatures around 200°C – closer to those used for cooking pizza than manufacturing steel – for 10 or more days, a new form results: Super Bainite. And by adding elements such as silicon and molybdenum, crack-inducing carbides can be prevented from forming.

Super Bainite's slow cooking process made it cheap to produce, but limited its commercial applications, so with MOD and EPSRC funding, the team set out to speed up the process. Kinetic and thermodynamic modelling revealed that tailoring the composition and heat treating the Super Bainite at slightly higher temperatures meant it could be manufactured in hours rather than days.  And by adding perforations to the steel – an innovation made at Dstl – the steel armour is even better at protecting vehicles from bullets.