To raise wear resistance, to reduce the number of repair by build-up and to reduce the cost of build-up material by executing the repair by build-up welding of the mounting hole of a work roll with a ferro alloy containing a specified composition of carbon and chromium and having a specified hardness.

The wear of the hole of a spindle coupling for mounting the work rolls is mainly caused by fatigue peeling of an oval-shaped hole. As its countermeasure, the improvement of wear resistance by raising the hardness of the build-up welding or the like is effective and, for the sake of that, the repairing material for a buildup welding is to be improved. The build-up welding is executed with the ferro alloy containing 0.1-0.2 wt.% C and 11-15 wt.% Cr. The hardness of the build-up welding is defined as Shore hadness of 65-75. Preferable hardness is about 68-73. It is preferable that the repairing material for build-up welding is the ferro alloy further containing 2-3 wt.% Ni. When the wear is severe, after once removing the inside of the hole including the repairing material and, after executing the build-up welding and heat treatment, it is better to again finish the hole into a desired shape.