- Use of tungsten carbide roll rings
Previously used rolls were centrifugal composite cast needle-shaped ductile iron rolling mill rolls, and the small-size finished single-slot rolling was only about 120 tons, which was frequent. In actual use, the first rolling single groove rolling amount is 1200t when the steel surface finish and the groove grinding amount are 0.75mm. After that, the cooling water system is further improved, the number of cooling water nozzles and the arrangement of the slots are improved, and the amount of water and water pressure are increased. The water pressure is increased from 0.25Mpa to 0.4Mpa. The single-groove rolling amount is increased to 1300 to 1400 tons.
- Cooling of the tungsten carbide roll rings
Tungsten carbide roll rings have high requirements for cooling water during rolling, and sufficient attention should be paid to the water volume, water pressure, water temperature and water quality of the cooling water. Due to its good thermal conductivity, cemented carbide will cause excessive heat transfer to the inner layer and the mandrel, resulting in internal expansion force, which is very dangerous for the cemented tungsten carbide roll rings at the outer layer. Tungsten carbide roll rings require enhanced water cooling.
Due to the high hardness and thermal cracking sensitivity of the cemented carbide, sufficient cooling is required immediately after the roller ring is in contact with the red steel. The flow of cooling water and its precise distribution have a decisive influence on the performance of the rolls. In addition to having a sufficient amount of water, the roll surface should be as cold as possible as soon as it leaves the roll gap and is continuously cooled on the largest possible circumference. The ideal cooling system is that the nozzles are distributed in a ring shape, and the main nozzle is placed close to the exit guide to continuously eject a sufficient flow of water into the groove. The water volume is not less than 15-20 m3/h, the water pressure is controlled at 0.4-0.6 Mpa, the water temperature is lower than 34 °C, and the pH is 7-9. When the pH of the cooling water is less than 7, the corrosion of cobalt (Co) is intensified, and the rolling life of the tungsten carbide roll rings with cobalt as the binder phase is greatly reduced.
Good cooling conditions, and ensure the continuous supply of cooling water in the production of finishing mills and the correct direction and mode of spraying. It is advisable to contact the roller ring after the machine is stopped, about 60~70 °C.
- Maintenance in production
Tungsten carbide roll rings are well maintained during use. Make sure that the cooling water pipe is aligned with the centerline of the groove when preparing for production. When using for the first time, it is necessary to stop the inspection after rolling for 1 to 2 hours, check whether the cooling water pipe is displaced, whether the water pipe nozzle is blocked, whether the surface of the groove is abnormal, and the temperature of the ring ring is measured. After many inspections, the number of parking inspections can be reduced without any abnormalities.
- Prevent tungsten carbide roll rings damage
Carbide is hard and brittle, and its toughness is relatively low, so pay special attention to handling, storage, processing and installation. It is necessary to handle it lightly, and it is strictly forbidden to strike and collide with the roller ring by external force, and strongly collide with hard objects such as rolling mills and concrete floors to avoid cracks and unnecessary damage.