Abstract: A 2-roll piercing mill for producing hollow blocks from a rolled material comprising high alloy steels has guide tools for the rolled material. The guide tools are arranged for closing a reforming zone of the piercing mill transversely with respect to the rolling axis as the hollow block is pierced. In this arrangement, each of the guide tools includes a base body made of a carrier material and a working face made of a material that has antiadhesive properties with respect to high alloy steels and high hot strength. Prior to the piercing operation, the temperature of either the working face or the entire guide tool is raised above room temperature to avoid high thermal stresses.