Comparison between a high chromium steel and a semi HSS grades used as work rolls in the roughing stands of a hot strip mill

Two alloys grades for work rolls used in the roughing stand of Hot Strip Mill (HSM) were compared. The first grade known as High Chromium Steel (HCS) is actually the alloy widely used for such an application, while the second one known as semi-High Speed Steel (semi-HSS) is the new grade developed to improve overall properties of the work roll in the roughing stands of the HSM.
In the present work, the new semi-HSS grade is studied starting from 3 chemical compositions closed one to another, the variation in the alloying elements being intended to assess, on one hand the effect of a light increase of the carbon content, and on the other hand the influence of the addition of a strong MC carbide forming element.
The comparison of HCS and semi-HSS grades involved many fields.
Regarding the metallurgical aspect, such a comparison led to the enhancement of the solidification range, the crystallization behavior and the microstructure in the as-cast condition for both grades.
Heat treatment behavior of both grades was also investigated and optimal parameters leading to the homogenization of the alloy composition within the deepness of the roll were found.
Furthermore, hot corrosion behavior and performances of the work rolls in service were compared.
Various techniques were used in order to characterize both grades, such as Differential Thermal Analysis (to determine phase transformations temperatures, the crystallization behavior and the interval of solidification), hardness measurements, optical microscopy, scanning electron microscopy associated with energy dispersive X ray spectroscopy (to determine the nature and the composition of phases, especially matrix and carbides).
Finally micro-macro relations between the nature of the microstructure and the properties of HCS and semi-HSS rolls grades in service conditions could be established.