Rolls made of powder metallurgy using tungsten carbide and cobalt as raw materials were born with the development of the metal processing industry after the advent of powder metallurgy technology in 1909. Due to the high speed and high stress of the finishing rolling mill, cast iron rolls and tool steel rolls (poor wear resistance, short groove life, frequent repairs, and loading and unloading, affecting performance, and not suitable for finishing rolling production requirements) have been replaced by combined tungsten carbide Rolls are replaced.
Different compositions of tungsten carbide rolls correspond to different working conditions, and even the same finishing unit has different roll compositions in different stands. The rolls used in high-speed wire rod mills are mainly tungsten carbide rolls with cobalt as the binder. A small number of continuous casting and rolling mills also use tungsten carbide rolls with Co-Ni-Cr as the binder due to poor water quality, and the cost is also low. The metallographic structure is composed of the matrix phase WC and the binder phase Co. The hardness of the carbide roll increases with the increase of the WC content; while the toughness increases with the increase of the binder phase content.
Tungsten carbide rolls have high hardness and are less affected by temperature. The hardness value at 700°C is 4 times that of high-speed steel; and the elastic modulus, compressive strength, flexural strength, and thermal conductivity are also more than 1 time higher than tool steel. Tungsten carbide rolls have much better wear resistance and deformation resistance than tool steel rolls in the working process, thus ensuring the smoothness and dimensional stability of the rolling groove, which is crucial to ensuring the surface quality and dimensional accuracy of the wire rod important. Due to the high thermal conductivity of the tungsten carbide roll, the heat dissipation effect is good, and the time for the roll surface to be at high temperature is short, so the high-temperature reaction time between the roll and harmful impurities in the cooling water is short. Therefore, tungsten carbide rolls are more resistant to corrosion and thermal fatigue than tool steel rolls.
