Steel Sheet Rolling Coolant Drainage for Oil Spot and Shape Control
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Solution Overview
Problem
Existing methods for manufacturing steel sheets fail to prevent defects in appearance and shape due to oil spots from coolant and thermal deformation of work rolls, as they either do not address coolant-induced oil spots or compromise cooling efficiency, leading to shape defects.
Innovation Solution
A method that controls the coolant feeding rate and drainage during rolling by using a liquid drainer and adjusting the coolant feeding rate based on sheet feeding rate and thermal deformation measurements to prevent oil spots and maintain appropriate thermal equilibrium of work rolls, ensuring defect-free steel sheets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the coolant feeding rate is increased to cool the work rolls, then thermal deformation of work rolls is controlled, but oil spots of coolant adhere to the steel sheet surface
Solution Approach 1:
A liquid drainer is introduced as an intermediary device between the coolant nozzle and the steel sheet. The liquid drainer collects excess coolant droplets that fall from the work roll surface, preventing them from adhering to the steel sheet. This allows the coolant feeding rate to be increased for effective thermal control without causing oil spot defects on the product surface.
2Object-affected harmful factors
If the coolant feeding rate is reduced to prevent oil spots, then oil spot adhesion is prevented, but thermal deformation of work rolls increases
Solution Approach 1:
The liquid drainer acts as a mediator that decouples the relationship between coolant feeding rate and oil spot formation. By collecting excess coolant, the liquid drainer enables the system to maintain high coolant feeding rates for effective thermal management while preventing oil spot defects, thus resolving the trade-off between these two parameters.
3Ease of operation
If a liquid drainer is disposed near the nozzles to improve coolant drainage, then coolant drainage is improved, but oil spots still occur under high coolant feeding rates
Solution Approach 1:
The liquid drainer is designed with specific structural parameters including the distance from the nozzle, the width of the drainer, and the position relative to the work roll surface. By optimizing these parameters, the liquid drainer effectively collects coolant droplets even at high feeding rates, preventing oil spot formation while maintaining good coolant drainage.
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
This method effectively prevents defects in steel sheet appearance and shape by optimizing coolant drainage and thermal control, resulting in higher yield and quality of steel sheets with reduced oil spots and thermal deformation issues.
Implementation Method 1
feeds a cooling fluid (hereinafter referred to as 'a coolant') to rolls forming each of the rolling mills to prevent temperature rise of the work rolls due to frictional heat caused during rolling of a steel sheet
Implementation Method 2
the sprayed coolant 3 is desirably drained in an atomized form. Insufficient draining of the coolant 3 may allow a liquid lump of the coolant 3 with a specific size to scatter and adhere to the top and bottom surfaces of the steel sheet 4
Data Source
Figure 1
Figure 2~3(e)
AI summary
Provided is a method for rolling a steel sheet and a method for manufacturing a steel sheet capable of preventing occurrence of defects in appearance of a steel sheet caused by oil spots of a coolant and preventing occurrence of defects in shape of a steel sheet by appropriately controlling thermal deformation of work rolls. The method for rolling a steel sheet according to the present invention is a method for rolling a steel sheet involving feeding of a coolant to rolls that form a rolling mill during the rolling. The method includes keeping a coolant feeding rate at or lower than a predetermined rate lower than an upper constant rate at a start of operation of the rolling mill, and increasing the coolant feeding rate to the upper constant rate in response to an amount of center buckles of the steel sheet reaching or exceeding an upper target value.