Continuous Casting Slab Assessment for Split Risk Prediction
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Solution Overview
Problem
Existing methods for inhibiting splitting of steel sheets into two pieces during rolling are ineffective for all steel grades, leading to increased manufacturing costs and risks due to varying occurrence rates and the use of methods that compromise roll life or introduce new defects.
Innovation Solution
A method to assess the risk of slab splitting by determining the liquid fraction of scale using component concentrations in molten steel, adjusting continuous casting conditions, and identifying and welding cross-sectional defects to prevent splitting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a slab is forcibly reduced at the final stage of solidification to close voids in the last-solidified portion, then cross-sectional defects are eliminated, but the reaction force increases significantly, greatly reducing the service life of rolls and segments
Solution Approach 1:
The patent changes the parameter of roll gap dynamically during the casting process. Instead of applying constant strong reduction force, the roll gap is adjusted based on the solidification state of the slab. When the slab is sufficiently solidified, the roll gap is reduced to close voids; when the slab is still soft, normal roll gap is maintained. This parameter change allows defect elimination while avoiding excessive reaction forces that would damage rolls and segments.
2Reliability
If the secondary cooling flow rate is reduced to inhibit the confinement of a residual liquid phase, then splitting into two pieces is inhibited, but the solidified shell thickness is affected and other defects such as internal cracks may occur
Solution Approach 1:
The patent applies preliminary action by assessing the risk of splitting into two pieces before the slab enters the heating furnace. Using component concentrations in molten steel, the patent calculates an index of liquid fraction of scale and determines risk in advance. This allows selective application of preventive measures only to high-risk slabs, avoiding unnecessary cooling adjustments for low-risk slabs that could cause internal cracks.
Solution Approach 2:
The patent applies local quality by differentiating handling methods based on individual slab characteristics. Instead of uniformly reducing secondary cooling for all slabs, the patent identifies specific slabs with high splitting risk through component analysis and applies targeted cooling adjustments only to those slabs. This localized approach prevents internal cracks in low-risk slabs while effectively preventing splitting in high-risk slabs.
3Reliability
If methods for inhibiting splitting into two pieces are applied to all steel grades, then splitting risk is reduced, but manufacturing costs increase significantly
Solution Approach 1:
The patent applies partial action by using component concentration analysis to identify only those slabs that require preventive measures. By calculating the index of liquid fraction of scale from component concentrations, the patent selectively applies cooling adjustments and other preventive measures only to high-risk slabs rather than all slabs. This partial application significantly reduces manufacturing costs compared to universal application while maintaining adequate reliability for high-risk cases.
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
Effectively determines the risk of slab splitting, reducing manufacturing costs and preventing unnecessary risks by targeted handling and processing of slabs, ensuring stable production of non-splitting hot-rolled steel sheets.
Implementation Method 1
a first step of determining the index of a liquid fraction of scale formed on a slab using component concentrations in molten steel poured into a mold of a continuous casting machine
Implementation Method 2
for the slab determined to have the cross-sectional defect, a void in the cross-sectional defect is welded
Data Source
Figure 1~2
Figure 3
AI summary
There is provided a method for assessing a slab, which method can determine, based on component concentrations in molten steel manufactured by a continuous casting machine, the risk that a slab manufactured from the molten steel will split into two pieces. A method for assessing a slab containing Ti, C, Si, and Mn as components and manufactured using a continuous casting machine includes a first step of determining the index of a liquid fraction of scale formed on the slab using component concentrations in molten steel poured into a mold of a continuous casting machine, and a second step of determining that the slab is at risk of splitting into two pieces when the index of the liquid fraction of the scale is greater than or equal to a predetermined threshold value.