He also invented silicon steel, initially for mechanical properties (patents in 1886) which have made the alloy a material of choice for springs and some fine blades, though it has also become important in electrical applications for its magnetic behaviour.

He declined to use patented technology from France and developed his own, thus laying the foundations for what was to become one of Britain's leading armament firms.

Amongst other properties: in a tensile test it drew out uniformly whilst in most metals local elongation or ‘necking’ occurs, and magnetism is absent in it.

[1] In Brinell units the surface hardness increased on deformation from 200 to 550 or 580 (approaching that which will scratch glass) according to measurements by Floris Osmond.

[1] In 1891 he adopted both the eight-hour workday at his company, and the thermoelectric pyrometer, which had been developed by the Frenchman Henry Louis Le Chatelier.

[1] In 1899 a paper in the Royal Dublin Society was published by Barrett, Brown and Hadfield of seminal importance to magnetism, in a hundred alloys of iron.

[1] Hadfield collaborated with James Dewar in the study of very low temperatures on the properties of metals, and with Heike Kamerlingh Onnes at the University of Leyden Cryogenic Laboratory after his appointment there in 1905.

[11] Hadfield married in 1894 Miss Frances Belt Wickersham, of Philadelphia, who earned a CBE in 1918 for her services in World War I as the founder of a hospital at Wimereux.