HSS (High-Speed Steel) rolls exhibit excellent wear resistance, with a service life in the finishing stands of hot mills that is 3 to 6 times longer than that of high-chromium iron rolls. However, uneven temperature distribution on the roll surface can lead to non-uniform thermal expansion, resulting in oxide film detachment and negatively impacting product surface quality. To address this, optimizing the cooling water distribution—particularly by increasing water flow to the center of the roll body—helps maintain a uniform temperature profile.
The hot rolling lubrication system forms a protective film on the surface of HSS rolls, reducing rolling force, preserving surface condition, and preventing iron oxide from degrading surface quality. To ensure effective lubrication, the entire lubrication pipeline must be regularly steam-cleaned.
The number of rolling cycles between two grindings is mainly influenced by the condition of the oxide film, the surface roughness of the rolls, and the grade of the rolled material after dismounting. Additionally, proximity to the finishing stand plays a role: when oxide film and surface roughness are well-maintained, rolls in upstream stands can typically be used for more cycles than those in downstream stands.
If an abnormal operating condition occurs during rolling, it can lead to severe localized mesh-like thermal cracks on the roll surface. In such cases, the HSS roll must be replaced immediately. After cooling, crack detection should be performed using either an automatic or portable ultrasonic flaw detector.
2 Comments
Mostafa Ewees
What are the actions should be taken to keep HSS Rolling ring in good condition
In case of cobble or metal coiled the ring for example last stand
In case of normal rolling
In case of water cut or mill sudden stoppgae
Should i close the water immediatly after cobble coiled the ring or i should leave the water for minutes
Tina Zhong
When steel buildup or metal wrapping around the roll rings occurs, the cooling water supply should not be shut off immediately. Even if steel buildup or wrapping occurs, continue to supply cooling water to the rolls for several minutes (usually 3-5 minutes is recommended, depending on the rolling temperature and roll size). This is because after high-temperature rolling, a large amount of heat is still accumulated inside the rolls. Immediately cutting off the water supply will cause a sharp change in the roll surface temperature, generating huge thermal stress, which can easily cause cracks or even breakage on the roll surface. Continuous cooling helps to evenly dissipate heat and protect the rolls.