Hot Strip Mill Force-Guided Induction Heating for Skid Marks
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Solution Overview
Problem
Hot Strip Mills face issues with temperature non-uniformity due to 'skid marks' on the slabs, leading to thickness control problems and quality issues in finished products, as existing pyrometric temperature measurement methods are inaccurate and influenced by surface conditions, failing to represent the average temperature of the bar effectively.
Innovation Solution
A new generation rolling plant with a rapid heating device and mechanical deformation detection means to apply localized heating based on rolling force variations, ensuring uniform temperature across the bar length by selectively activating thermal induction modules to compensate for cold zones caused by skid marks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pyrometric temperature detectors are used to measure surface temperature, then temperature measurement is possible, but the measurement does not accurately represent the average temperature of the bar section
Solution Approach 1:
The patent replaces pyrometric (optical/radiation-based) temperature measurement with mechanical deformation detection. Load cells mounted on the rolling stand measure the rolling force required to deform the bar, which directly reflects the average temperature of the bar section. This mechanical measurement method provides accurate representation of the actual thermal state affecting the rolling process.
2Strength
If water-cooled longitudinal members are used in the heating furnace, then the mechanical characteristics of the members are maintained, but cold impressions (skid marks) are formed on the slab
Solution Approach 1:
The patent implements a feedback control system where load cells continuously monitor rolling force variations that indicate the presence and severity of skid marks. This information is fed back to the operator or control system, which then adjusts the heating parameters in the finishing train to compensate for the cold impressions, ensuring uniform temperature distribution despite the harmful cooling effect of the water-cooled members.
3Temperature
If additional heating is applied to compensate for skid marks, then temperature uniformity is improved, but the complexity of the heating system increases
Solution Approach 1:
The patent employs a self-regulating heating approach where the existing finishing rolling train serves dual purposes: it both rolls the bar to final dimensions and provides friction heating to compensate for skid marks. The controlled reduction in rolling speed during finishing passes generates sufficient friction heat to raise the temperature of cold zones, eliminating the need for separate heating devices while maintaining temperature uniformity.
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 achieves uniform average temperature of the bar entering the finishing train, improving the dimensional and microstructural quality of the finished product while maintaining high productivity, up to 6 million tons/year, without negatively affecting mechanical and geometric properties.
Implementation Method 1
a rapid heating device (28) consisting of selectively activatable thermal induction modules (41, 42)
Implementation Method 2
thermal induction modules (41, 42) interposed between the last pre-finishing stand (26) and the finishing stands (31)
Data Source
AI summary
A rolling plant and method for producing a strip starting from a slab having a certain starting thickness, comprising at least one walking beam heating furnace configured to heat at least the slab to a starting temperature, and a rolling train operatively disposed in line with at least one roughing stand and configured to reduce the thickness of an intermediate rolled product at exit from the roughing stand, until the final strip is obtained; the rolling train comprising at least one pre-finishing stand for obtaining a pre-finished rolled product, and a plurality of finishing stands for obtaining the final strip; the plant comprising load cells directly associated with the pre-finishing stand for detecting the rolling force applied on the pre-finished rolled product, a rapid heating device, interposed between the pre-finishing stand and the finishing stands, for heating the pre-finished rolled product, and a command and control unit connected both to the load cells and also to the rapid heating device and configured at least to selectively activate the latter, at least as a function of the rolling force detected by the load cells.