100 years of stainless steel


100 years of stainless steel

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2013 marks the centenary of the invention of stainless steel. TM talks to UK manufacturers who process and use the material about its continuing significance in today’s world. Jane Gray reports.

A century after its discovery, the UK produces almost 330,000 tonnes of stainless steel in a year. Around 213,000* tonnes is used by manufacturers in sectors from nuclear energy components through catering equipment, healthcare, construction, domestic appliances, automotive, oil & gas, renewable energy and more. It is a vital staple for thousands of UK manufacturing and precision engineering firms.
What makes stainless steel so special? Its resistance to corrosion means that it is a durable metal which will not oxidise (rust) or react with many substances, from bodily fluids to beer. It is also resistant to heat, therefore suitable for use in environments from up to 1,200°C down to -196°C depending on the grade of steel. And it is cheap compared to other, specialist, non-corrosive alloys which have been discovered more recently. Chromium is a key ingredient that makes this steel so popular. Chromium reacts with oxygen in the air to form a passive chromium oxide film on the surface of the metal and, in general, the higher the chromium content the more resistant to corrosion.

Harry Brearley is widely attributed with the invention of the first true stainless steel, which had a chromium content of 12.8%.

There are now around 100 grades of stainless steel commercially available spread across four main family groups; martenistic, ferritic, austentic, and duplex. These have varying quantities of other alloying metals (nickel, titanium, copper) added to them, as well as carbon and nitrogen, to enhance characteristics such as corrosion resistance, ductility, formability and weldability.

Brearley’s invention is a landmark in British industrial history which has made his home town of Sheffield renowned as a global centre for metallurgy. This year Sheffield will be the focal point for several events to celebrate the importance of stainless steel to its economic heritage and its future. A key event for stainless steel-using companies is the Harry Brearley Stainless Steel Centenary Conference and Exhibition which will be hosted by the British Stainless Steel Association (BSSA) and the Sheffield Metallurgical and Engineering Association on June 12.

Banister End for Stainless steel handrails

These institutions are keen to emphasise that while stainless steel production is a global industry, with China now unsurprisingly the largest producer, the home town of stainless steel remains at the heart of developments in production technologies and applications.

For example, the world’s largest stainless steel producer and distributor, Outokumpu, a sponsor of the Brearley conference, employs around 600 people in Sheffield at its melt shop, bar mill and service centre. Outokumpu sells 80,000- 100,000 tonnes of stainless steel to British manufacturers every year (p32). In 2010 the company completed an investment of Eu10 million to establish an integrated manufacturing route for small bar and reinforcing bar products. This new line compliments Outokumpu’s existing melt shop and wire-rod mill.

Meanwhile, at the Nuclear Advanced Manufacturing Research Centre in Rotherham, important research into deephole boring techniques for stainless steel components in the nuclear industry is ploughing ahead. A big challenge for this project is to develop boring techniques which can cope with the high ductility of the 304 stainless steel used in nuclear applications. High ductility is needed to avoid “neutron embrittlement” during use in the nuclear cooling process, but it increases the risk of clogging and exploding drill bits during the machining process.

Stainless steel business cards

Tapping into growing industrial and societal concerns about the sustainability of commonly used materials, the conference will also want to emphasise the sustainable credentials of stainless steel which is 100% recyclable. Indeed the BSSA claims that every new melt of stainless steel made today contains around 65% recycled material. The association is also closely tracking investment in the development of various renewable energy technologies in the UK. Stainless steel is used, to varying degrees, across many of the technologies which may become integral to our energy generation infrastructure in the future, including tidal, biogas, solar and carbon capture and storage.

This article is courtesy of The Manufacturer.