EXPERIENCE IN THE LABORATORY AND COMMERCIAL DEVELOPMENT OF ABRASION CORROSION-RESISTANT STEELS FOR THE MINING-INDUSTRY

The need for the development of new steel types suitable for the particular requirements imposed by harsh mining conditions has been determined along with different routes that could be followed in order to obtain the required properties. The results from a literature review on medium chromium (4%-12%) martensitic steel types are discussed with specific reference to alloying elements such as carbon, chromium, nickel and molybdenum and to austenitic grain size. Results of a laboratory development programme on a large number of melts are presented. It is shown that combined additions of chromium, nickel and molybdenum result in significantly improved corrosion resistance compared with that of plain chromium steels, whilst at the same time a combination of good impact toughness and high hardness can be obtained. A 160 ton production melt of one of the experimental alloys was made. Mechanical properties and corrosion, abrasion and corrosion-abrasion resistance compare favourably with those of other candidate steels. The engineering properties such as weldability, flame and plasma cutability and machinability are discussed and it is shown that the developed steel can be produced with relative ease. The steel is suitable for many applications in the mining industry and will in many instances constitute a considerable improvement on steels currently in use in this sector. © 1990.