HI-CR High Chrome Iron Rolls
Hi-Cr High Chrome iron rolls have a surface layer of cast iron with a high chromium content and free from graphite. It is essentially a white iron with a chromium content ranging from 12% to 22%. This chromium addition together with controlled amounts of nickel and molybdenum results in a very high level of hardenability. The properties of the surface layer are influenced both by the large content of chromium carbides and by the properties of the matrix.
Hi-Cr High Chrome Iron rolls are multi-stage, high temperature heat treated to produce discontinuous, extremely wear resistant iron/chromium carbides (Cr7C3&Cr3C2) in a matrix which can be varied from a soft spheroidized pearlite through to high hardness tempered martensite according to the requirements of the application. Chromium carbides at hardnesses measuring between 1650-2200 HV result in unparalleled abrasive wear and higher hardness grades are among Hisar’s most wear resistant.
Because of the very high hardenability of Hi-Cr High Chrome Iron, the hardness can be made virtually constant across any given roll section so that the rolls are very suitable for applications where deep grooves are required. The higher hardness grades are Hisar’s most wear resistant materials.
Applications range from dogbone and slitting stands in Rod &Bar mills, where ‘tearing’ demands extreme wear resistance, to hot rolling and straightening of sections. Hi-Cr High Chrome Iron can be used in the form of conventional mono-block rolls and have been particularly successful as mandrel mounted rolls such as straightening rollers, and rolls for seamless tube mills.
Care must be taken to optimize roll cooling in order to extract maximum performance and ensure campaign lengths are maximized and the material used to its fullest potential.