Due to the particularity of high-speed wire rolling mill operation, two aspects of work were mainly carried out during the manufacturing process. The first is the selection of materials and heat treatment processes, and the second is the control of the roughness of the rolling surface. Due to the thicker inner wall and thinner outer wall, some manufacturers specify in their technical documents that the inner ring is made of carburized steel and the outer ring is made of high carbon chromium steel. Correspondingly, the inner ring adopts carburization process, while the outer ring adopts isothermal quenching and tempering process as much as possible, so that the obtained metallographic structure is lower bainite. This treatment takes into account performance indicators such as strength, wear resistance, impact toughness, and fatigue life of the bearing, so that the bearing meets the aforementioned working requirements. In addition, the hardness of the heat treatment also varies depending on the different conditions of the rough, medium, and precision rolling mills. For the rough rolling mill, the speed is relatively low and the impact load is relatively large, so the hardness of the bearing parts is relatively low; For precision rolling mills, the speed is relatively high and the impact load is relatively small, so the hardness of bearing parts is high; The hardness of the bearings used in the rolling mill is in the middle. Through observation and testing analysis, the surface roughness values of the inner and outer rings of the high-speed rolling mill bearings, such as the raceway surface, retaining edge surface, and the rolling surface reference end face of the rollers, are slightly smaller than those of ordinary rolling mill bearings.
Roller bearings used in wire rod rolling mills have to withstand high loads. Very high forces are applied at rolling speeds of up to 125 m/s and sudden load peaks during the first pass of the rolled material.Rolling bearings in wire rod rolling mills are used for the safe and accurate bearing arrangement of shafts,axles and bevel gearboxes. High speeds and dynamic loads represent a major challenge here. Dependingon the shape and temperature of the rolled material, the initial peak loads are more than twice the rolling force or rolling mill torque. The result is a significant reduction in the service life of the rolling bearings.
In order to ensure the durable and safe operation of the wire rod rolling equipment, high-precision special bearings are used that can absorb the forces that occur, and guarantee low-friction and low-vibration rotation with the components. SMS manufactures precision bearings to DIN 620 with accuracy standards P5–P2 especially for this demanding application. In doing so, long, expensive downtimes are avoided, while a high quality of rolled products is achieved.
