In-Line Slab Rolling Friction Control to Prevent Protrusion Folding
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Solution Overview
Problem
Existing twin-drum type continuous casting methods result in protrusion folding during rolling, leading to surface defects and decreased productivity due to inadequate pickling times and quality assurance issues, especially when dealing with slabs having dimples or protrusions.
Innovation Solution
A manufacturing method that calculates a friction coefficient using rolling load and forward slip through an Orowan theory and Shida's approximate formula, controlling lubrication conditions to maintain a friction coefficient between 0.15 and 0.25, thereby preventing protrusion folding during in-line rolling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dimples are formed on the cooling drum surface to improve cooling efficiency and casting stability, then protrusions are formed on the slab surface, but folding of these protrusions occurs during rolling leading to surface defects
Solution Approach 1:
The invention changes the physical parameters of the protrusions by controlling their height (50-150 μm) and the friction conditions during rolling. By optimizing these parameters and controlling the friction coefficient through lubrication, the protrusions can exist without folding during subsequent rolling operations.
Solution Approach 2:
The dimples are formed locally on specific portions of the cooling drum surface rather than uniformly across the entire surface. This localized approach allows protrusions to form only where needed for casting stability, while minimizing their impact on subsequent rolling operations.
2Productivity
If protrusions are formed on the slab surface through dimple process, then cooling efficiency is improved, but adequate pickling time is required to remove oxide scales from folded portions, decreasing productivity
Solution Approach 1:
The invention takes preliminary action by controlling the friction coefficient during rolling to prevent protrusion folding in the first place. By applying lubrication before rolling and maintaining the friction coefficient between 0.15-0.25, the oxide scales do not become trapped in folded portions, eliminating the need for extended pickling times.
3Ease of manufacture
If friction coefficient is not controlled during in-line mill rolling, then rolling process is simple, but protrusion folding occurs leading to quality assurance issues
Solution Approach 1:
The invention introduces lubrication as an intermediary substance between the slab and the rolling mill rolls. This lubrication layer mediates the friction interaction, controlling the friction coefficient to a specific range (0.15-0.25) to prevent protrusion folding while maintaining a relatively simple rolling process.
4Manufacturing precision
If overmelting is performed to prevent surface defects, then quality is improved, but manufacturing cost increases and yield decreases
Solution Approach 1:
The invention performs preliminary action by controlling the friction coefficient during the rolling process to prevent protrusion folding before surface defects can occur. This preventive approach eliminates the need for overmelting operations, thereby maintaining surface quality while avoiding the associated increases in manufacturing cost and decreases in yield.
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
Prevents protrusion folding without impairing productivity, ensuring consistent quality and reducing manufacturing costs by optimizing lubrication conditions in the in-line mill process.
Implementation Method 1
calculating a friction coefficient from measured values of a rolling load and a forward slip
Implementation Method 2
a cooling apparatus that is arranged on a downstream side of the twin-drum type continuous casting apparatus and cools the slab
Implementation Method 3
an in-line mill that is arranged on a downstream side of the cooling apparatus and performs one-pass rolling on the slab with a work roll at a rolling reduction of 10% or larger
Data Source
AI summary
This manufacturing method for a slab is a method for manufacturing a slab by a continuous casting equipment including a twin-drum type continuous casting apparatus, a cooling apparatus, an in-line mill, and a coiling apparatus. The method includes calculating a friction coefficient from measured values of a rolling load and a forward slip when the slab is rolled, by use of a rolling analysis model, and controlling a lubrication condition during rolling of the slab so that the friction coefficient falls within a predetermined range, wherein, when the friction coefficient is calculated from the measured values of the rolling load and the forward slip by use of an Orowan theory and a deformation resistance model formula based on a Shida's approximate formula as the rolling analysis model, the predetermined range is 0.15 or more and 0.25 or less.