Little did he know he was making history when Harry Brearley (1871-1948), melted and cast a high-chromium steel composition in mid-August 1913. At the time, Brearley, son of a Sheffield steelworker, was working at Brown-Firth Research Laboratory in the UK on a project to develop a more erosion-resistant steel for rifle gun barrels. According to folklore, he tossed the experimental steel on the scrap heap and was surprised to find later that this material had not rusted. Recognising the significance of his discovery, he approached his employer with the idea of developing a ‘rustless’ cutlery steel but was turned down. So he sought the aid of a local cutlery manufacturer, R F Mosley & Co, where a friend, E Stuart, suggested calling the new material “stainless steel”. A few years later, following a dispute over patent rights, Brearley left Brown-Firth and went to Brown Bayley Steel Works, also in Sheffield. Although there have been several other claimants to the discovery of corrosion-resistant steels, Brearley seems to have been the one who set off the commercial production of these “novel” materials.
Development of stainless steels was interrupted by WWI, but Brearley’s successor at Brown-Firth labs, Dr W H Hatfield, later went on to develop the austenitic type of stainless steel known today as ‘18/8’ from its Cr/Ni composition.
As usage grew way beyond the original cutlery application, an increasing number of distinct grades emerged. From their metallurgical characteristics, these were classified into martensitic, austenitic, ferritic, duplex, and precipitation-hardening categories. Production zoomed with blossoming applications in food and chemical-processing, appliances, architecture and building construction, aerospace, automotive, medical, and other fields. Worldwide consumption of cast and wrought stainless, now approaching 40 million tonnes with China as the chief driver, is believed to have grown ten-fold in the past half-century.
Enter PM
PM stainless came along much later, with commercial production of sintered stainless steel parts beginning in the late 1950s in North America and somewhat earlier in Europe. However, stainless steel powders are still only produced on a miniscule scale compared with the wrought products. Applications include sintered stainless steel parts for aerospace, automotive, chemical processing, medical and recreational goods sectors. There was a burst of growth in the 1990s with the introduction of stainless steel ABS sensor rings and exhaust manifold flanges in the auto sector. More recently, MIM applications, e.g. in the medical and dental fields, have grown rapidly. Large-scale HIPped parts for oil and gas production and electric power industries use significant quantities of gas-atomised stainless steel powders, for which Sweden and the USA are major sources. Bernard Williams has estimated world-wide PM stainless production for 2013 at 15,000 metric tons, while MPIF puts North American stainless steel powder shipments in 2012 at an estimated 7350 short tons.
Back in Sheffield, the British Stainless Steel Association and the Sheffield Metallurgical and Engineering Association hosted the Harry Brearley Stainless Steel Centenary Conference and Exhibition (in June 2013), as part of the City of Sheffield’s celebrations to mark the 100th anniversary of the discovery of stainless steel. The City also commissioned a large mural portrait of Brearley, and students at Sheffield University named a beer after him!
