Cold-Rolling Mill Work Roll Diameter and Nested Support
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Solution Overview
Problem
Conventional rolling systems face challenges in producing harder steel strips with higher reduction ratios while maintaining productivity, as reducing work roll diameter in cluster type rolling mills leads to decreased productivity and increasing the number of stands results in significant costs.
Innovation Solution
A cold-rolling mill design with work rolls of 300-400 mm diameter and intermediate rolls of 560-690 mm diameter, along with a work roll drive unit and overload preventive devices, allows for higher reduction ratios without decreasing productivity and avoiding the need for additional stands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If work roll diameter is reduced to increase reduction ratio and produce harder steel strips, then manufacturing capability is improved, but productivity decreases
Solution Approach 1:
The patent implements a nested roll configuration where work rolls are positioned inside intermediate rolls, which are in turn positioned inside backup rolls. This nested structure allows the work rolls to have a smaller diameter (enabling higher reduction ratios) while the larger intermediate and backup rolls provide structural support and maintain productivity by distributing mechanical loads effectively.
Solution Approach 2:
The patent transitions from a conventional two-high rolling mill to a four-high rolling mill configuration, adding an intermediate dimension layer. By introducing intermediate rolls between the work rolls and backup rolls, the system achieves higher reduction ratios through the smaller work rolls while maintaining productivity through the additional structural dimension provided by the intermediate rolls.
2Adaptability or versatility
If number of stands is increased to improve total rolling reduction capability, then reduction capability is improved, but investment cost increases significantly
Solution Approach 1:
The patent changes the dimensional parameters of the rolling mill components, specifically reducing the work roll diameter while increasing the number of roll layers from two to four. This parameter change enables a single stand to achieve the same total rolling reduction capability that would traditionally require multiple stands, thereby improving reduction capability without increasing device complexity or investment cost.
3Adaptability or versatility
If work roll diameter is reduced below 300 mm to achieve higher reduction ratios, then reduction ratio increases, but roll strength becomes insufficient
Solution Approach 1:
The nested configuration allows the work rolls to be smaller in diameter (enhancing reduction ratio capability) while being supported by progressively larger intermediate rolls and backup rolls. This hierarchical support structure ensures that the smaller work rolls can operate at higher reduction ratios without compromising overall system strength, as the larger outer rolls bear the mechanical loads.
Solution Approach 2:
The intermediate rolls and backup rolls are positioned in advance to provide preliminary structural support and load distribution. This preliminary action ensures that when the work rolls operate at high reduction ratios, the mechanical stresses are distributed across the entire nested structure, preventing strength failure in the smaller work rolls.
Data Source
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AI summary
By reducing the work roll in diameter, rolling of a harder steel strip than ever and rolling of a steel strip of the same hardness as before at a higher reduction ratio can be performed, while preventing decrease in productivity due to use of such a small-diameter work roll mill as in the cluster type rolling mill. A cold-rolling mill 51 for rolling a metal strip 1 of minimum width not less than 600 mm and maximum width not less than 1,500 mm but not greater than 1,900 mm comprises a pair of upper and lower work rolls 2 for rolling the steel strip 1 to be rolled; a pair of upper and lower intermediate rolls 3 supporting the work rolls 2, respectively; a pair of upper and lower buck-up rolls 4 supporting the intermediate rolls 3, respectively; an axial direction roll shifting device 23 for each of the intermediate rolls 3; and bending devices 10, 11 for each of the work rolls 2 and the intermediate rolls 3. The work rolls 2 each have a diameter not less than 300 mm but not greater than 400 mm, and the intermediate roll 3 each have a diameter not less than 560 mm but not greater than 690 mm.