Cold Rolling Mill Edge Heating and Lubrication for Crack Prevention
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Solution Overview
Problem
In tandem type cold rolling mills, hard-to-roll materials like silicon steel and stainless steel experience edge cracks and breakage due to inadequate heating and lubrication during low-speed rolling, leading to increased energy costs and production complications.
Innovation Solution
A cold rolling mill with a hybrid oil-feeding system where edge portions are heated by an induction heating device and then jetted with a high-concentration coolant, ensuring stable edge temperature and lubrication without excessive heating or increased primary unit costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the steel sheet temperature is increased to improve deformation resistance and rolling property, then the rolling property is improved, but the energy cost increases significantly and the production process becomes complicated
Solution Approach 1:
The patent applies local heating to only the edge portions of the steel sheet using induction heating devices, rather than heating the entire sheet. This localized approach improves the rolling property of the critical edge regions while minimizing overall energy consumption and avoiding the need for complex full-sheet heating processes.
Solution Approach 2:
The heating process is segmented into specific zones - only the edge portions requiring improved rolling properties are heated to above the ductile-brittle transition temperature, while the central portions remain at lower temperatures. This segmentation allows selective improvement of rolling property where needed without unnecessary energy expenditure.
2Reliability
If the steel sheet is heated to improve edge crack resistance, then edge crack is reduced, but edge wave is generated due to thermal expansion
Solution Approach 1:
The induction heating devices are positioned to heat only the immediate edge portions of the steel sheet to just above the ductile-brittle transition temperature. By limiting the heated zone to the critical edge regions and avoiding heating of the broader sheet areas, the patent prevents excessive thermal expansion that would cause edge wave while still achieving crack resistance improvement.
3Power
If the lap length of the inductor and steel sheet edge is increased to improve heating effectiveness, then heating output is improved, but abnormal heating is caused leading to edge wave
Solution Approach 1:
The patent employs adjustable inductor positions and controllable lap lengths that can be dynamically optimized for different sheet widths and heating requirements. By making the heating system adjustable rather than fixed, the patent achieves optimal heating output for each specific condition without causing abnormal heating or edge wave.
Solution Approach 2:
The patent controls the lap length parameter within an optimal range (5-20mm) to balance heating effectiveness with prevention of abnormal heating. By precisely controlling this parameter and adjusting it according to sheet specifications, the patent achieves sufficient heating output while avoiding the thermal expansion that leads to edge wave.
4Power
If the coil current is increased to improve heating output when lap length is decreased, then heating output is improved, but power factor decreases and reactive current increases
Solution Approach 1:
The patent pre-adjusts the inductor position and lap length to optimal values before heating begins, ensuring that maximum heating output is achieved at the lowest possible coil current. By optimizing the magnetic coupling between inductor and sheet edge in advance, the patent avoids the need to increase current to compensate for poor coupling, thereby maintaining good power factor and minimizing reactive current.
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 edge cracks and breakage in hard-to-roll materials during low-speed rolling by maintaining edge temperature above 60°C and improving lubrication, reducing energy consumption and production costs while enhancing product quality and productivity.
Implementation Method 1
a high-frequency current is flowed to an induction heating coil 3 to generate a high-frequency magnetic flux, whereby an induction current is generated in the edge portion of the steel sheet and the edge portion of the steel sheet is heated by Joule heat generated by the induction current
Implementation Method 2
the edge portion of the steel sheet is heated by Joule heat generated by the induction current
Data Source
Figure 1~3
Figure 4~5
Figure 6
AI summary
In a tandem type cold rolling mill of a circulating oil-feeding system for continuously rolling a steel sheet by feeding a coolant serving as a rolling oil and a cooling water to each stand, an edge heater for heating both edge portions of the steel sheet to not lower than 60°C as a steel sheet temperature at an entry side of a roll bite is arranged at an upstream side of the first stand in the cold rolling mill and a device for jetting a coolant having a concentration higher than that of the coolant fed to the firsts stand onto surfaces of both edge portions of the steel sheet is arranged between the edge heater and the first stand. By using such a cold rolling mill can be rolled a hard-to-roll material such as silicon steel sheet or stainless steel sheet without causing an edge crack in an edge of the steel sheet or sheet breakage even in low-speed rolling.