In reversing cold mills the tension reels are placed on both ends of a single- or two-mill-stand arrangement. Due to the reversing rolling passes, production efficiency is lower than that of a tandem mill. However, because the rolling parameters can be quickly changed for each coil, reversing cold mills are especially suitable for the small-lot production of various product types. The size of the mill equipment is also smaller, which allows easier access to mill equipment and machinery for maintenance purposes. Due to their simpler design, reversing mills can be more easily stopped and restarted. They are also less expensive to purchase and operate.
Single-stand reversing cold mills
Depending on the product mix, a single-stand cold rolling mill can deliver rolling capacities of 100,000 to 400,000 t/a. Rolling schedules can be carried out with an even or odd number of passes to maximize mill availability and performance. The Universal Crown Control mill (UCM mill) with work roll bending, intermediate roll bending, intermediate roll shifting and all straight roll application ensure enhanced flatness control. Also strip flatness measuring equipment mounted at one or both ends of the mill combined with multi-zone work-roll cooling to meet the highest demands for flatness.
Two-stand reversing cold mills
Primetals Technologies' two stand reversing cold mills combine the flexibility of single-stand reversing mills with the capacity of conventional coil-to-coil tandem mills at substantially reduced investment costs. Steel rolled in two-stand reversing cold mills is suitable for a wide range of applications, offering the best possible performance in terms of quality and productivity. A two-stand reversing cold mill can deliver capacities between 300,000 t/a of thin-gauge products or 1,000,000 t/a and more of thicker-gauge products.
Main benefits of Primetals Technologies' reversing cold mills
- High production capacity and yield
- Flexible, low-cost rolling of a wide range of products, especially for small order lots
- Tight strip thickness and shape tolerances
- Minimum off-gauge length
- High surface quality
- Second stand can serve as a skin pass mill
The HYPER UC-MILL is newly developed to achieve high performance of strip gauge and flatness control for High Strength Steel (HSS) rolling. This technology is also applicable for rolling high grades of non-grain oriented silicon steel and thin products. The technology development is based on the following concepts:
- Optimized roll diameter combination (small work, intermediate and back-up rolls)
- 'Work Roll Driven System' to achieve high flatness controllability
- Development of a high strength small diameter spindle to drive the work roll
Main Feature of HYPER UC-MILL
Optimized Combination of Work, Intermediate and Back-up Rolls
When investigating the selection of roll diameter, there are two major limitations: load limit to maintain good strip flatness and load limit due to the contact stress between the rolls. The graph shows the relationship between these limits. The hatched part is the maximum allowable rolling force. The graph also shows the calculated reduction ratio at the maximum allowable load. The graph shows that the HYPER UC-MILL covers the range of the highest achievable reduction; (Work Roll Diameter)/(Strip Width) = 0.18 - 0.24
Plant productivity and product quality are substantially depending on the quality of plant automation, process control, and available process optimization functions.
To get the best performance out of a plant, Primetals Technologies provides add-on specific optimization solutions for further improvement of production efficiency and strip quality, besides standardized high performance automation system.
Excellent Strip quality with:
- REC - Roll Eccentricity Compensation for uniform and accurate strip thickness
- CECO - Coil Eccentricity Compensation for uniform and accurate strip thickness
- AFC - Model based Automatic Flatness control
- ChatterMon / Mill Chatter Monitoring with automatic process speed adaptation
For Reversing cold mills a highly optimized solution is available matching all kind of mill stand configurations. According to the complexity of production a look-up table or rolling model based mill setup can be chosen.