Niobium in stainless steels

It is only a century ago that alloy steels began to be introduced to replace the theretofore ubiquitous carbon steels with materials of improved properties. Such alloying elements were first introduced in 1868 (1) with the tungsten air hardening steels and in 1886 (2) with the austenitic manganese steels, but it was not until 1900 that nickel, chromium and silicon were introduced into engineering, tool and magnet steels (3, 4). It is only some seventy years ago that the stainless steels were discovered, more or less accidently by Brearley i n England, and Strauss and Maurer i n Germany (5), Brearley being responsible for the 13 percent Cr martensitic cutlery steels whilst Strauss and Maurer discovered the austenitic 20 percent C r , 7 percent N i alloys. Both discoveries were made in a search for quite different types of material, but it is significant that both alloys contained more than 12 percent Cr which is the critical level for corrosion and oxidation resistance. Thus both alloys displayed what was to become universally accepted as the property of "stainless". ..(AU)