Continuous Slab Casting with Adaptive Two-Stage Reduction
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Solution Overview
Problem
Conventional continuous casting methods struggle to maintain slab internal quality when casting speed changes, as existing techniques fail to effectively adjust reduction positions and equipment arrangements, leading to inefficiencies and internal defects in the slab.
Innovation Solution
A method using a continuous casting machine with two stages of reduction rolls, where the diameter of each roll is 1.2 to 2.0 times the slab thickness, with support rolls in between, allowing for adaptive reduction strategies based on solid-phase ratios and casting speed adjustments to ensure consistent internal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If reduction is carried out outside the continuous casting machine using conventional arts, then the slab internal quality can be improved, but the efficiency decreases as surface temperature falls and heavy plant investment is required
Solution Approach 1:
The reduction process is divided into two distinct stages: first reduction within the continuous casting machine while the slab is still hot, and second reduction outside the machine after cooling. This segmentation allows each stage to be optimized independently - the first stage utilizes high temperature for efficient deformation with minimal equipment, while the second stage handles quality refinement
Solution Approach 2:
The first reduction is performed preliminarily within the continuous casting machine before the slab exits and cools down. By conducting reduction while the slab surface temperature is still high (above Ar3 transformation point), the process takes advantage of improved ductility and reduced flow stress, thereby increasing reduction efficiency and reducing equipment requirements
2Force
If the diameter of reduction rolls is increased to improve reduction capability, then the reduction force increases, but the equipment cost and machine complexity increase
Solution Approach 1:
The invention changes the operating temperature parameter of the slab during reduction. By performing the first reduction at elevated temperatures (above Ar3 transformation point) within the continuous casting machine, the material exhibits improved ductility and reduced flow stress. This allows adequate reduction force to be achieved with smaller, less expensive rolls rather than requiring large diameter rolls that would be needed at lower temperatures
3Productivity
If casting speed is increased to improve productivity, then the production rate increases, but the internal quality of the slab deteriorates due to insufficient solidification and increased defects
Solution Approach 1:
The reduction process is made continuous by performing it in two sequential stages without interrupting the casting flow. The first reduction occurs continuously within the machine during hot rolling, and the second reduction occurs continuously outside the machine after cooling, ensuring uninterrupted production while maintaining quality
Solution Approach 2:
Critical quality-related actions are performed preliminarily at high temperature within the continuous casting machine before the slab cools and becomes more difficult to deform. The first reduction stage eliminates centerline segregation and reduces porosity formation when the material is most ductile, preventing quality issues before they can develop during subsequent cooling and processing
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 approach enables the continuous casting of slabs with excellent internal quality even when casting speed changes, while reducing equipment costs and minimizing bulging issues, thus improving productivity and quality stability.
Implementation Method 1
reduction is carried out on the slab inside and outside a continuous casting machine
Implementation Method 2
when the solid-phase ratio at the center of the cast slab in the thickness direction is 0.80 or more
Data Source
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AI summary
A primary object of this invention is to provide a continuous casting method for carrying out reduction on a slab in a continuous casting machine, and by which the slab of excellent internal quality can be continuous-cast even if the casting speed is changed. This invention provides a method for continuous-casting a slab wherein upon continuous-casting a slab while reduction is carried out on the slab using a continuous casting machine with two stages of reduction rolls, each of the two stages consisting of a pair of the reduction rolls, and being arranged along a casting direction, a diameter of each of the reduction rolls being 1.2 to 2.0 times as much as thickness of the slab just before reduction with corresponding reduction rolls, the continuous casting machine including the reduction rolls and support rolls arranged between the reduction rolls, when a casting speed is reduced compared to a state where the slab is cast at a constant speed under combination of reduction with reduction rolls at a first stage on an unsolidified portion of the slab and reduction with reduction rolls at a second stage on a solidified portion of the slab; accompanying movement of a place of the slab where the solidification is ended upstream in the casting direction due to the reduction of the casting speed, the combination is switched to combination of reduction with the reduction rolls at the first stage on a portion of the slab at an end of solidification and the reduction with the reduction rolls at the second stage on the solidified portion of the slab.