Effect of MC type carbides on wear resistance of high wear resistant cast iron rolls developed for work rolls of hot strip mills

High-speed steel type cast iron rolls were developed around 1990 and have been widely used in the former stands of hot strip mills. However, in the latter stands of the hot strip mills, the use of high-speed steel type rolls has been limited due to the insufficient crack resistance. Therefore, in order to improve the wear resistance of the latter stands, enhanced type high-nickel grain rolls in which MC type carbides of high hardness are crystallized in a conventional high-nickel grain roll has been developed. However, since the wear resistance of the enhanced type high-nickel grain roll is significantly inferior to that of the high-speed steel type roll. Therefore, The development of a new cast iron roll with superior wear resistance and is applicable to the latter stands of hot strip mills was studied. The present development roll has improved wear resistance by increasing the amount of addition of the high hardness MC type carbide forming elements. In addition, the reduction of the carbon equivalent for less amount of eutectic carbides resulted in the reduction of the residual stress down to the same level as the high-nickel grain roll, which improved the crack resistance. As a result, it was confirmed that the wear resistance was improved about three times compared with the conventional high-nickel grain rolls. In addition, the results suggest that the wear resistance of work rolls for the hot strip mill is largely controlled by the amount of MC carbides among the rolls with the same hardness.