The main equipment parameters of a four-high cold rolling mill cover the main drive motor, roll system, rolling process, roll arrangement and alignment, and auxiliary equipment. These parameters determine the mill's rolling capacity, operating speed, thickness control accuracy, and range of applications.
During equipment selection, design, manufacturing, and technical acceptance, each parameter must be specified according to the material being rolled, strip width, entry and exit thickness, and production requirements. The actual specifications vary depending on the mill size and configuration.
Main drive motor parameters
The main drive motor supplies the power required for rolling. Its power, torque, and speed control capabilities must match the rolling load and operating speed. The following parameters need to be specified:
Rated power: The motor's rated output power, selected according to the maximum rolling load and production speed requirements.
Rated speed and speed range: Including rated speed, minimum operating speed, and maximum operating speed, which define the mill's speed adjustment range.
Rated torque and peak torque: The rated torque, steady-state torque, and peak torque must be specified, together with the maximum allowable duration of peak torque operation.
Motor type: Whether an AC variable-frequency motor or DC motor is used, along with the corresponding drive control method.
Protection rating and cooling method: Including the motor enclosure protection rating, cooling arrangement, and cooling medium requirements. These parameters must suit the operating environment.
For reversible cold rolling mills that require frequent starting, braking, and direction changes, the motor's overload capacity and dynamic response also need to be checked. This helps prevent a mismatch between motor selection and actual rolling conditions.
Roll system parameters
A four-high cold rolling mill generally consists of two work rolls and two backup rolls. The work rolls make direct contact with the strip, while the backup rolls support the work rolls and carry the rolling load. The dimensions, hardness, and roll profile of each type must be specified separately.
Work roll parameters
Work roll dimensions and surface conditions directly affect strip thickness, surface quality, and rolling stability. The main parameters include:
Roll barrel diameter, including the diameter difference between the upper and lower work rolls.
Roll barrel length and effective working length.
Roll surface roughness grade and surface finishing requirements.
Roll hardness, including HV or HS hardness values and allowable deviations.
Roll neck diameter, roll neck length, and corresponding dimensional tolerance grades.
Geometric accuracy requirements, including barrel cylindricity and radial runout.
Backup roll parameters
Backup rolls support the work rolls and reduce their bending deflection under rolling loads. Their main parameters include:
Roll barrel diameter and barrel length.
Roll crown, referring to the diameter difference between the center and the edges of the roll barrel.
Roll surface hardness and allowable deviation.
Roll neck diameter, length, and machining tolerances.
Roll barrel profile and grinding contour, including the specified crown and special profile parameters.
For mills using CVC (Continuously Variable Crown) or S-shaped roll profiles, the corresponding roll contour, axial movement range, and position control accuracy must also be specified. These parameters need to match the mill's strip flatness control system.
For mills equipped with roll bending devices, the work roll bending force, adjustment range, and related hydraulic actuator parameters should also be defined. Roll bending and specially designed roll profiles help compensate for work roll deflection and control the roll gap distribution and transverse strip thickness.
Rolling process system parameters
Rolling process parameters define the material specifications, rolling loads, and dimensional accuracy that the mill can handle. In addition to rolling force and tension control, the mill's basic processing capacity must also be specified.
Basic rolling capacity
The equipment specifications should define the materials and product dimensions that the mill is designed to process. The main parameters include:
Types of materials to be rolled and applicable material specifications.
Entry strip thickness range and maximum entry width.
Exit strip thickness range and product width range.
Maximum rolling speed and normal operating speed range.
Maximum rolling force and continuous operating load requirements.
Rolling mode, including reversible or unidirectional rolling, and the corresponding pass requirements.
These specifications define the mill's overall production capacity and provide the basis for selecting the main motor, rolls, and drive system. A typical mill specification sheet also includes rolling speed, maximum rolling force, coil weight, coil diameter, and work roll and backup roll diameters.
Rolling force and screwdown control parameters
The rolling force and screwdown systems directly affect strip thickness accuracy. The main parameters include:
Maximum rolling force and normal operating force range.
Measurement range and accuracy grade of the rolling force sensors.
Effective screwdown stroke and maximum adjustment speed.
Positioning accuracy and repeat positioning accuracy of the screwdown mechanism.
Operating pressure and control response requirements of the hydraulic screwdown system.
For mills equipped with hydraulic AGC (Automatic Gauge Control), the hydraulic cylinder specifications, control accuracy, and measuring device configuration must also be defined.
Tension control parameters
The tension control system coordinates the tension at the entry and exit sides of the mill to maintain stable strip movement during rolling. The main parameters include:
Tension ranges of the uncoiler and coiler.
Entry and exit strip tension control accuracy.
Measurement range and accuracy of the tension detection devices.
Tension roll diameter, surface roughness, and surface treatment requirements.
Adjustment range and dynamic response requirements of the tension control system.
A tension roll is a detection or guiding component used in certain equipment configurations. Whether a separate tension roll is required depends on the mill's tension control arrangement.
Strip flatness and roll bending control parameters
For four-high cold rolling mills equipped with strip flatness control functions, the following parameters also need to be specified:
Work roll bending force and adjustment range.
Operating pressure and stroke of the roll bending hydraulic cylinders.
Axial roll movement range, where axial adjustment is available.
Measurement range and accuracy of the strip flatness gauge.
Parameters related to roll profile adjustment and strip flatness control.
These parameters are closely related to work roll and backup roll design and must be determined according to the actual mill configuration.
Roll arrangement and alignment parameters
Roll arrangement and installation accuracy affect roll gap distribution, rolling stability, and strip thickness consistency. The following parameters need to be checked during installation and commissioning:
Rolling line elevation: The height of the roll centerline and rolling line relative to the equipment reference surface.
Initial roll gap: The initial clearance between the rolls under no-load or specified measurement conditions, together with the roll gap zero-setting requirements.
Axial roll movement: For mills equipped with axial shifting or lateral movement, the travel range and position accuracy must be specified.
Roll levelness: The levelness deviation of the upper and lower rolls after installation.
Roll parallelism: The parallelism deviation between the upper and lower roll axes, together with roll gap consistency along the barrel length.
Rolling centerline alignment: The alignment deviation between the mill stand centerline, roll centerline, and production line reference centerline.
These parameters should be checked against the installation reference points, measurement methods, and equipment specifications. Roll installation errors and housing deformation under load can both affect the actual roll gap. Checking individual roll dimensions alone is therefore insufficient.
Auxiliary equipment parameters
In addition to the main mill and roll system, a four-high cold rolling mill requires auxiliary equipment for roll changing, lubrication and cooling, hydraulic operation, and strip coiling. The technical specifications of these systems should also be included in the equipment data sheet.
Roll changing equipment parameters
Roll changing equipment is used to remove, replace, and install rolls. The main parameters include:
Roll changing system type and drive method.
Time required for one roll change and the corresponding operating conditions.
Load capacity and travel range of the roll changing trolley, where a trolley-type system is used.
Roll positioning accuracy and repeat positioning accuracy after installation.
Position detection and safety protection functions during roll changing.
The roll changing cycle depends on the mill structure, roll dimensions, replacement procedure, and lifting arrangements. A single standard time value should not be applied to all mills.
Process lubrication and cooling system parameters
The lubrication and cooling system reduces friction and temperature rise during rolling while maintaining strip surface quality. The main parameters include:
Type of lubrication and cooling medium and its compatibility with the material being rolled.
Lubricant or cooling fluid flow range.
Oil or fluid supply pressure.
Medium temperature and related control requirements.
Filtration accuracy and filtration system configuration.
Emulsion concentration or relevant rolling oil properties, depending on the medium used.
Coiler and uncoiler parameters
The coiler and uncoiler handle strip winding and unwinding. Their specifications must match the strip dimensions and tension control requirements. The main parameters include:
Maximum coil weight.
Maximum and minimum coil diameters.
Mandrel inner diameter and applicable coil specifications.
Rated motor power and maximum output torque.
Operating speed range and speed control accuracy.
Coiling and uncoiling tension ranges.
Operating parameters of coil clamping, mandrel expansion and contraction, and related mechanisms.
Hydraulic and automation system parameters
For mills equipped with hydraulic screwdown, roll bending, and automatic thickness control systems, the specifications should include hydraulic power unit operating pressure, oil flow rate, actuator parameters, and control requirements.
The electrical and automation system specifications should cover the PLC and drive control configuration. The measurement range, accuracy, and signal interfaces of thickness gauges, tension sensors, rolling force sensors, and other online inspection devices must also be defined.
Custom precision machining for industrial equipment
A four-high cold rolling mill contains various non-standard mechanical components used in the main drive, roll installation, and auxiliary equipment. Different machines have their own dimensional, structural, and fitting requirements.
Our precision machining services also cover components used in industries beyond rolling mills. Hansheng Automation provides drawing-based custom machining for non-standard parts used in filling machinery and tobacco and packaging equipment, as well as precision structural components for yacht equipment and remote-controlled racing cars. Customers can submit their design drawings for custom manufacturing according to the specified requirements.
