Tandem Cold Rolling with Tapered Work Rolls for Edge Crack Suppression
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Solution Overview
Problem
Existing cold rolling methods fail to sufficiently suppress edge cracks and subsequent sheet breakage in cold-rolled steel sheets due to inadequate control of edge drop and tension distribution during the rolling process.
Innovation Solution
A cold rolling method using a tandem rolling mill with specific configurations of tapered and flat work rolls, where the second stand employs a tapered work roll with a linear load of 0.8 t/mm or more and a tapered rolling portion width of ±0 mm to +50 mm, and the third stand uses a flat work roll, to manage edge drop and tension effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a method for controlling sheet thickness in the width direction using tapered work rolls and shifting mechanisms in multiple stands is employed, then the sheet thickness distribution in the sheet width direction is improved, but the occurrence of edge cracks and sheet breakage during cold rolling is not sufficiently suppressed
Solution Approach 1:
The invention changes the operating parameters by controlling the linear load to be 0.8 t/mm or more and precisely setting the tapered rolling portion width WRδ within -50 mm to -5 mm. These parameter adjustments optimize both the sheet thickness distribution and suppress edge cracks by controlling the deformation state during rolling.
Solution Approach 2:
The invention applies local quality by using tapered work rolls with specifically controlled taper portions rather than uniform rolls throughout. The taper is localized to specific regions of the work roll, allowing different sections to provide different functions: the tapered portion controls edge thickness while the uniform portion maintains overall sheet quality.
2Reliability
If the tapered rolling portion width WRδ is set within -50 mm to -5 mm and linear load is maintained at 0.8 t/mm or more, then edge cracks are suppressed and sheet breakage is prevented, but the sheet thickness distribution control becomes more complex
Solution Approach 1:
The invention establishes specific parameter ranges (linear load ≥0.8 t/mm and WRδ between -50 mm to -5 mm) that simplify control by providing clear operational boundaries. Within these boundaries, the system achieves reliable edge crack suppression without requiring continuous complex adjustments.
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 configuration effectively suppresses edge cracks and breakage by maintaining suitable edge drop ratios across stands, reducing tension on edge portions, and preventing sheet breakage during cold rolling.
Implementation Method 1
cold-rolling a material to be rolled by a rolling mill including a plurality of stands
Implementation Method 2
rolls the material to be rolled with a linear load of 0.8 t/mm or more
Data Source
AI summary
A cold rolling method, cold rolling equipment, and a cold-rolled steel sheet manufacturing method capable of preventing sheet breakage by sufficiently suppressing occurrence of an edge crack of a material to be rolled during cold rolling. In the cold rolling method, a rolling mill including a plurality of stands to cold-rolls a material to be rolled. An N-th stand (N is a natural number equal to or greater than 2) arranged in an N-th position from an upstream side of the material to be rolled in a transfer direction among the plurality of stands, includes a tapered work roll having a taper formed on an end portion of a roll having a uniform diameter. The N-th stand rolls the material to be rolled with a linear load of 0.8 t/mm or more.