Cold Rolling Line Roller Height Control for Coolant Ride
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Solution Overview
Problem
Existing cold rolling methods face issues with work roll deformation and brittle cracking due to temperature fluctuations and coolant liquid ride effects, leading to poor lubrication and shape defects in steel sheets, particularly in high-speed rolling processes.
Innovation Solution
A cold rolling line with controlled roller height differences and adjustable inclination angles to manage coolant liquid ride length, maintaining the steel sheet temperature within optimal ranges by adjusting the position and angle of the steel strip relative to the rolling mills.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If coolant is injected towards the work roll and steel sheet to prevent thermal deformation and lubricate during rolling, then work roll thermal deformation is suppressed and lubrication is improved, but the steel sheet temperature drops due to coolant liquid ride, causing brittle fracture risk
Solution Approach 1:
The steel sheet is preheated to a temperature higher than the ductility brittle transition temperature before entering the rolling mill. This preliminary heating ensures that even when coolant causes temperature drop during rolling, the steel sheet temperature remains above the brittle transition temperature, preventing brittle fracture while still allowing coolant to perform its lubrication and work roll cooling functions.
2Temperature
If the line speed is slow, then the liquid ride length of coolant is longer providing better cooling, but the steel sheet is cooled to about the temperature of the coolant even if preheated, increasing brittle fracture risk
Solution Approach 1:
The steel sheet is preheated to a temperature higher than the ductility brittle transition temperature before entering the rolling mill. This preliminary heating compensates for the excessive cooling effect at slow line speeds, ensuring the steel sheet temperature remains above the brittle transition temperature throughout the rolling process.
3Productivity
If the rolling speed is high, then productivity is improved, but the liquid ride length becomes short reducing cooling effectiveness, and heat input to work rolls increases causing thermal crown formation
Solution Approach 1:
The steel sheet is preheated before rolling to compensate for reduced coolant cooling effectiveness at high line speeds. This ensures the steel sheet maintains appropriate temperature throughout the rolling process even when coolant liquid ride length is short due to high rolling speed.
Solution Approach 2:
The inclination angle of the steel sheet relative to the horizontal direction is controlled to be within ±10 degrees. This parameter control optimizes the liquid ride length of the coolant, ensuring sufficient cooling effectiveness even at high rolling speeds while preventing excessive heat input to the work rolls that would cause thermal crown formation.
4Temperature
If roller height is adjusted to control steel sheet inclination for optimizing liquid ride length, then temperature control is improved, but device complexity increases
Solution Approach 1:
The roller heights are made adjustable to dynamically control the inclination angle of the steel sheet. This dynamic adjustment capability allows the system to optimize the liquid ride length of the coolant under different rolling conditions (speed, coolant flow rate, steel sheet temperature), improving temperature control while maintaining reasonable device complexity through straightforward mechanical adjustment mechanisms.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively suppresses work roll deformation and brittle cracking, ensuring stable rolling conditions and improved sheet quality by controlling temperature variations.
Implementation Method 1
coolant is injected towards the biting area between the work rolls and the steel sheet to lubricate the steel sheet during rolling and to prevent thermal deformation of the work rolls
Implementation Method 2
the temperature of the steel sheet is lowered by the coolant that flows toward the entry side (coolant liquid ride)
Implementation Method 3
the steel sheet temperature rises due to processing heat generated during rolling
Data Source
AI summary
A cold rolling line, a steel sheet production line, a cold rolling method, and a steel sheet production method can suppress work roll deformation and brittle cracking during rolling. The cold rolling line includes one or more cold mills configured to inject coolant towards a work roll and a metal steel strip and to cold roll the metal steel strip, rollers provided upstream from the one or more cold mills in a conveyance direction of the metal steel strip and used to convey the metal steel strip, and a control unit that controls a height difference of the rollers. The control unit controls the rollers so that the metal steel strip is at a lower position towards a downstream side in the conveyance direction at an upstream side of at least a portion of the one or more cold mills including a most upstream mill provided farthest upstream.