1. General Overview & Production Philosophy
This offering features a well-maintained 4-Stand 4-High Cold Rolling Mill, a complete tandem mill train designed for efficient and high-volume production of cold-rolled steel strip. Unlike single-stand reversing mills, this 4-stand configuration allows the material to be reduced in thickness through four consecutive rolling stands in a single pass. This continuous process significantly boosts productivity, ensures better consistency in mechanical properties, and is ideal for manufacturers looking to achieve medium-to-high output of quality cold rolled products. The equipment is supplied by Keepwin Industry, a specialized provider of used metallurgical solutions, ensuring professional support throughout the transaction and beyond.
2. Mill Type, Configuration, and Structural Integrity
The core of this line consists of four individual 4-High rolling mill stands arranged in a tandem configuration.
Mill Stands: The presence of four stands means that the strip undergoes reduction at four separate points sequentially. This distributes the total reduction required, allowing for better control of thickness, shape, and surface finish compared to a single-stand mill.
Mill Housing: Each stand features a robust closed housing design (known as a "牌坊" in Chinese) with substantial cross-sectional dimensions of 400mm x 480mm. The closed housing construction provides exceptional strength and rigidity, minimizing deflection under heavy rolling loads. This structural integrity is fundamental to maintaining consistent strip profile and thickness across the entire width of the material.
4-Hi Roll Configuration: Each stand utilizes the proven 4-High roll configuration. This design pairs two small-diameter work rolls (in direct contact with the strip) with two large-diameter backup rolls. The backup rolls provide the necessary support to prevent the work rolls from bending, which is critical for achieving tight thickness tolerances and a superior strip shape. This configuration is a workhorse of the cold rolling industry, valued for its balance of reduction capability and precision.
3. Product Dimensional Specifications
The mill is engineered to process a specific range of input materials and deliver a versatile array of finished products.
Entry Material: The line can accept hot-rolled pickled coils with a maximum entry thickness of 4.5 mm. This is a standard starting gauge for many cold rolling applications, providing a good foundation for subsequent reduction.
Finished Product: Through the cumulative reduction of its four stands, the mill is capable of producing thin-gauge finished products down to a minimum thickness of 0.3 mm. This capability targets a wide range of applications, from general stamping and forming to more precise cold-rolled strip uses.
Width Capability: With a maximum rolling width of 750 mm, the line is ideally suited for producing medium-width strip. This size range is commonly used in industries such as automotive components, light construction, tubing, and general manufacturing.
4. Speed and Production Efficiency
Designed for continuous operation, this tandem mill achieves a maximum rolling speed of 260 meters per minute. This speed, combined with the multi-stand configuration, allows for a high rate of production. The ability to process a coil from start to finish in a single, continuous pass at this speed translates directly into lower cost per ton and higher annual output, making it a highly productive asset.
5. Core Component Specifications
The mill's key mechanical components are sized for durability and performance:
Work Rolls: Specification: Ф220 x 870 mm. These are the rolls that directly contact and deform the steel. Their smaller diameter concentrates the rolling force for effective reduction.
Backup Rolls: Specification: Ф620 x 850 mm. These large-diameter rolls provide the necessary backing force to the work rolls. Their size and robust construction are essential for minimizing roll bending and ensuring flatness across the strip width.
Reels: The tension reel and uncoiler are of the collapsible drum type, with a diameter of Ф508 x 850 mm. The collapsible design is a standard industry feature that allows for easy gripping of the coil's inner diameter and smooth removal of the finished coil.
6. Drive and Power System
The mill is powered by a robust electrical drive system designed for reliable, high-torque operation in an industrial environment.
Main Drive: The four mill stands are driven by a single main motor rated at 900 kW (Model: Z560-4A). The power is distributed from this main motor to the stands via a gearbox and pinion stand system, a common and effective design for tandem mills of this era.
Tension Reel Drive: Precise tension control is critical in tandem rolling. The coiler and uncoiler are powered by a dedicated 430 kW motor (Model: Z4-400-42). This motor provides the necessary torque to maintain proper strip tension between stands and during coiling, which is vital for stable rolling and good strip shape.
7. Control and Operation
Screw-down System: This mill is equipped with an electric screw-down system. While not as dynamic as modern hydraulic AGC (Automatic Gauge Control), a well-maintained electric screw-down system provides reliable, repeatable, and stable positioning of the rolls. It is a proven technology suitable for a wide range of cold rolling schedules where ultimate gauge precision is not the primary requirement. It is robust, easier to maintain, and perfectly adequate for producing standard commercial quality cold rolled strip.
Electrical Control System: The overall electrical control system is reported to be in good condition. Its functionality ensures the coordinated operation of the main drive, tension reels, and screw-downs, allowing operators to effectively manage the rolling process.
8. Ancillary and Support Information
Spare Parts: A list of spare parts to be delivered with the equipment is available, which is invaluable for ensuring quick and cost-effective maintenance after installation.
Visual Documentation: The accompanying photographs in the original document provide a visual confirmation of the equipment's general condition, showing the mill stands, control desks, and auxiliary equipment.
9. Comprehensive Value-Added Services from the Supplier
Keepwin Industry distinguishes itself as a full-solution provider, not just an equipment seller. To ensure a seamless transition from acquisition to production, they can offer a comprehensive suite of services:
Disassembly: Professional, methodical dismantling of the entire mill train, with careful labeling and preservation of components for transport.
Refurbishment & Maintenance: Options to inspect, refurbish, and service critical components—such as gearboxes, motors, and screw-downs—either before shipment or after arrival at the new site.
Installation & Commissioning: Provision of experienced technicians to supervise on-site installation, align the stands, connect the systems, and assist with the commissioning process. This service is key to minimizing downtime and getting the mill operational quickly and correctly.
In summary, this 4-Stand 4-Hi 750mm Cold Rolling Mill represents a complete, high-productivity solution for medium-width cold rolling. It combines the efficiency of a tandem configuration with robust mechanical design, proven drive systems, and the full backing of an experienced metallurgical industry supplier.
