6-Hi 850mm Cold Rolling Mill

Complete Basic Parameter Table

3. Detailed Full English Description

(1) Overall Functional Positioning & Production Application

1. This single-stand reversible 6-Hi cold rolling mill is professional core equipment for cold reduction of mild steel hot pickling coils. Compared with conventional 4-Hi rolling mills, the extra pair of intermediate rolls effectively restrains work roll deflection under heavy rolling load, delivering outstanding strip flatness control and ultra-thin rolling capacity. It can reversibly roll raw steel coils from initial 3mm thickness repeatedly to obtain finished strips with minimum 0.2mm thickness, which are widely applied for manufacturing cold rolled sheets, galvanizing base strips, home appliance panels, hardware blanks and construction thin steel strips.
2. The mill was officially produced by Wuxi Wuye in 2015 and only stopped operation in May 2026, meaning the whole equipment has a short service life with low wear on frame, rolls and transmission components. All main structural parts, roll assemblies, hydraulic AGC units and full sets of DC drive motors are kept complete without disassembly or part loss. After comprehensive overhaul including frame calibration, roll surface inspection, motor insulation testing, hydraulic pipeline flushing and Siemens & Ouda electrical program debugging, the mill can be directly connected to power, cooling and hydraulic systems to launch mass continuous production, saving long manufacturing and installation cycles of brand-new rolling equipment.
3. Its stable 300 m/min maximum line speed and 1000-ton heavy rolling force support high-volume continuous rolling production. It can be independently matched with uncoiler, entry threading table and exit recoiler to form a complete single-stand cold rolling production line, suitable for medium and large metal processing factories focusing on mild steel cold rolling.

(2) 6-Hi Three-Tier Roll System Structural Advantages

1. The six-roll structure consists of three layers of rolls: small-diameter work rolls, intermediate transition rolls and large-diameter backup rolls, forming a rigid force transmission system.
   • Work rolls Φ175×890 mm: Directly contact the steel strip to complete thickness reduction. Small roll diameter lowers rolling torque demand and allows larger single-pass reduction, reducing total rolling passes and boosting production efficiency.
   • Intermediate rolls Φ260×850 mm: Installed between work rolls and backup rolls, evenly distribute huge rolling pressure, suppress work roll bending and eliminate edge wave, middle wave and other flatness defects of thin strips.
   • Backup rolls Φ680×850 mm: Oversized heavy rolls bear the majority of rolling force, providing rigid support for intermediate rolls and greatly improving the overall mill stand stiffness, ensuring uniform transverse thickness across the full 780mm strip width.
2. All roll bodies adopt wear-resistant hardening treatment during original production, with high surface hardness and long service life. The roll gap is dynamically adjusted by AGC hydraulic cylinders in real time, realizing automatic closed-loop thickness control without manual screw-down adjustment.

(3) Full DC High-Power Drive System Configuration

1. Main rolling drive unit: Equipped with Z710-1B 1000kW large DC motor manufactured by Hangzhou Hengli Motor, featuring wide speed regulation range from 650 rpm to 1100 rpm. It outputs stable high torque at both low and high speeds, perfectly matching the mill’s 300 m/min high-speed rolling demand and maintaining constant strip tension during reversible forward & backward rolling. The motor adopts Class F insulation and independent air cooling design to avoid overheating under long-hour continuous heavy load.
2. Uncoiler and recoiler drive: Two identical sets of 500kW Z4 series DC motors are separately configured for entry uncoiler and exit recoiler, with adjustable speed of 400–1200 rpm. Dual independent tension control effectively eliminates strip tension difference between the coil head and tail during multi-pass reversible rolling, preventing thin strip stretching, necking or thickness deviation. All DC motors on the whole line follow JB6316-92 national manufacturing standard, with complete nameplate parameter information and intact bearing and insulation structures.

(4) AGC Hydraulic Automatic Thickness Control & Electrical System

1. The mill is equipped with full hydraulic AGC automatic gauge control system as standard configuration, replacing outdated manual electric screw-down structure. High-precision thickness sensors installed at the mill entry and exit feed real-time thickness data back to the hydraulic servo cylinder, which instantly adjusts the roll gap to compensate thickness deviation caused by roll thermal expansion, rolling force fluctuation and raw material tolerance, strictly controlling finished strip thickness tolerance within ultra-narrow range.
2. The complete electrical control system combines Ouda local control modules and Siemens core PLC, digital DC speed regulators and auxiliary control hardware, integrating all functions including speed linkage, tension closed-loop regulation, AGC thickness feedback, fault interlock and safety protection. The whole electrical cabinet set is fully intact without missing controllers, contactors or sensors. Operators can view real-time rolling force, line speed, strip thickness and motor running data via the operation panel, and complete parameter setting, mill start-stop and fault reset conveniently.
3. Comprehensive safety interlock programs are embedded in the Siemens control logic, covering strip break protection, tension overload protection, motor overheat protection, hydraulic overpressure protection and emergency stop interlock. Once abnormal rolling status occurs, the system will automatically decelerate or shut down the whole line to prevent strip breakage, steel piling and equipment collision damage.

(5) Core Production Performance Highlights

1. Wide thickness processing range: It can process incoming mild steel coils up to 3mm thick and produce ultra-thin finished strips as thin as 0.2mm, covering diverse product specifications for cold rolling manufacturers. The actual production data from the original user fully matches all design parameters, proving stable and reliable long-term rolling performance.
2. High-speed high-efficiency rolling capacity: 300 m/min maximum running speed is much higher than ordinary 6-Hi mills with 100–200 m/min limit, greatly lifting hourly coil processing tonnage and cutting unit energy consumption and labor cost.
3. 1000-ton heavy rolling force design: Supports large single-pass reduction, decreasing required rolling passes for each coil and shortening overall processing cycle. The six-roll layout guarantees superior strip flatness without secondary leveling procedures after rolling.
4. Complete integrated line configuration: The mill body, DC drive motors, AGC hydraulic station, roll system and full electrical control cabinets are all complete matched sets, without missing core auxiliary equipment. After simple on-site overhaul, it can be directly put into production without additional procurement of supporting uncoiler, recoiler or control devices.

(6) Machine Frame, Auxiliary Spare Parts & After-Sales Service Options

1. Mill stand frame is integrally cast with heavy alloy steel and fully stress-relieved after processing, featuring ultra-high rigidity to resist permanent deformation under long-term 1000-ton rolling force. All hydraulic pipelines, cable trays and lubrication systems are neatly arranged with dust and oil isolation design to extend service life of internal components. The on-site measured frame dimensions and roll installation dimensions fully comply with original factory design standards.
2. Complete spare parts can be delivered together with the mill, including spare bearings, sealing rings, hydraulic valve elements and electrical sensors; the detailed spare list needs further confirmation before shipment. All roll assemblies are reserved with complete disassembly and maintenance tooling for later roll surface grinding and replacement.
3. Disassembly, full machine refurbishment and maintenance services are available upon demand, with specific service costs to be confirmed separately. The modular design of the mill allows independent disassembly of frame, motors, roll system and electrical cabinets for convenient transportation and on-site assembly after delivery. Standardized Siemens electrical spare parts are widely available on the market, reducing later maintenance difficulty and operational cost.