Mastery of the Production of Bimetallic Cover Plates

Cover plates are used to protect the friction surfaces of the work stands and the chocks of rolling mills from wear. The plates were originally made of metal that had been heat-treated and had a hardness of 40-50 HRC or more after quenching. This reduced the wear of the plates but also revealed a serious problem with their use: wear was detected on the surface of the housing under the plates on mills in which dynamic loads are formed as the ingot is gripped by the rolls. In each impact - the kinetic energy of which is greater, the greater the mass and speed of the ingots being rolled - local bearing stresses developed and the metal crumbled on certain contact sections of the hard (HRC > 40) plate adjacent to the relatively soft (140-160 HB) surface of the housing. To eliminate wear of the above-indicated surfaces, metallurgists abroad commonly insert plates with friction surfaces and adjoining base surfaces of different hardnesses into housing windows. The hardness of the base surfaces, which also adjoin the housing, corresponds to the hardness of the housing (HB < 180), while the hardness of the friction surfaces varies within a broad range of values - from 37 to 60 HRC. (Materials noted: carbon steels, manganese steels.)