The offset eight-high cold rolling mill is a special multi-roll cold rolling device. It uses small-diameter work rolls and a unique mechanical structure. It is developed on the basis of backup-roll driven four-high rolling mills. This mill adds independent side support structures for work rolls. The structure optimizes roll system rigidity and rolling stability.
The frame structure of the offset eight-high cold rolling mill is similar to conventional four-high mills. Cependant, it adopts smaller work rolls and professional roll profile adjustment devices. This design stabilizes work roll positioning and improves horizontal stiffness. Its overall structural rigidity exceeds ordinary four-high mills.
It can produce partial products that usually require twenty-high rolling equipment. The mill supports flexible structural conversion into two-high, four-high, eight-high and double eight-high modes. It adapts to diversified production demands. Donc, it is also known as a multi-purpose cold rolling mill.
## 1. Structural Characteristics of Offset Eight-High Cold Rolling Mill
The offset eight-high cold rolling mill adopts backup roll driving mode. Its core feature is the offset installation of work rolls. Work rolls deviate from the center line of backup rolls. This unique layout removes torque and horizontal bending restrictions on work roll diameter reduction.
The work roll diameter is only about half of that in conventional four-high mills. It accounts for 15% à 20% of the backup roll diameter. The overall rolling force decreases to nearly 50% of four-high mills.
This structure enables the offset eight-high cold rolling mill to process ultra-thin strips and hard-to-deform metals. It works like traditional multi-roll mills in these aspects. Entre-temps, it retains the simple structure of four-high equipment. This design helps keep investment and maintenance costs relatively low.
All work rolls, intermediate rolls and side support rolls are installed on support arms. The support arms rotate around the side support roll axis. Side support rolls closely fit large backup rolls. This structure avoids extra friction torque consumption. It also protects the operating conditions of work rolls.
Pendant le roulage, vertical load from backup rolls transfers to the frame through screwdown bolts. Lateral force from side support rolls transmits to the frame via side beams. Spring devices maintain stable contact between side support rolls and backup rolls. Side support rolls use roller bearings and mandrel sleeves. This arrangement ensures flexible and stable operation.
The offset eight-high cold rolling mill has a rigid roll system. It also has reliable roll profile adjustment devices. It produces small mill springback values. It supports real-time roll shape optimization during operation. These features effectively improve strip thickness accuracy and flatness quality.
Independent driving of backup rolls allows a wider range of work roll diameter differences. The simple work roll support structure simplifies roll replacement. It also reduces roll wear. Low friction loss between roll gaps allows emulsion lubrication and cooling. This arrangement further reduces rolling resistance.
## 2. Equipment Composition and Technical Features
The main stand of the offset eight-high cold rolling mill consists of several key parts. It includes a complete roll system, screwdown mechanism, work roll neck holding device, swing gate and roll profile adjustment system. Compared with traditional four-high mills, it has three prominent technical characteristics.
### 2.1 Unique Offset Support Structure
The offset eight-high cold rolling mill is equipped with an independent side support system. Work rolls obtain vertical support from upper and lower backup rolls. They also receive lateral support from side support components.
Side support rolls and intermediate rolls assemble into fixed bow structures. They then mount on side support roll chocks. Lateral force transfers to the side support beam through concentric shaft supports.
This structure guarantees coaxial precision of work rolls, intermediate rolls and side support rolls. It maintains high integral roll system rigidity. The side support structure transmits torque through intermediate rolls during operation. It increases rolling reduction and reduces inter-roll slipping. It also decreases the risk of roll surface scratching.
En outre, the offset installation design and roll neck holding device maintain stable work roll operation. It ensures reliable rolling precision during reversible and high-speed rolling processes.
### 2.2 Independent Roll Profile Adjustment Device
The offset eight-high cold rolling mill is equipped with a dedicated hydraulic roll profile adjustment system. The hydraulic cylinder drives four movable wedges through connecting rods. The wedges use different inclination angles.
The two middle wedges have an inclination of 5°. The two side wedges have an inclination of 3°. Fixed flat blocks assist positioning on both sides. Vertical movement of wedges pushes side support rolls and intermediate rolls. This movement produces controllable bending deformation on work rolls.
This real-time adjustment precisely corrects strip flatness defects during continuous rolling. It also achieves flexible roll profile control.
### 2.3 Roll Dimension Matching Requirements
The length-to-diameter ratio of the offset eight-high cold rolling mill roll body ranges from 3 à 10. The side support system, especially the intermediate rolls, has relatively low local stiffness. Improper parameter matching easily causes slipping between backup rolls and work rolls. It may also cause roll surface scratching.
The coaxial accuracy of work rolls, intermediate rolls and side support rolls directly affects rolling stability. This mill requires stricter manufacturing standards than ordinary four-high mills. It also needs stricter installation and parameter calibration. Professional roll diameter pairing and precision adjustment are essential for stable operation.
## 3. Process Characteristics of Offset Eight-High Cold Rolling Mill
The rolling process of the offset eight-high cold rolling mill is similar to that of four-high mills. It is specially optimized for stainless steel and high-hardness metal rolling. It follows the equal-pressure rolling principle for pass reduction distribution.
The relative reduction decreases pass by pass. This method adapts to the high deformation resistance and work hardening characteristics of stainless steel. Chemical composition and metallographic structure differences also require targeted rolling parameter adjustment.
### 3.1 Flexible and Accurate Roll Profile Control
The offset eight-high cold rolling mill combines multiple flatness control methods. It includes original work roll crown design and segmented emulsion flow control. It also uses unique mechanical wedge adjustment devices.
Four sets of bending forces generated by hydraulic wedges adjust work roll deflection evenly along the roll body. The deflection range adapts to different strip materials and specifications. The work roll grinding crown ranges from 0.05 mm à 0.22 mm.
Pour 1000 mm wide strips, the dynamic crown adjustment range reaches ±0.05 mm with increasing rolling force. The on-site adjustment panel displays parameters in percentage. The maximum 100% adjustment corresponds to a 0.10 mm crown variation. This system provides high-precision and flexible flatness control.
### 3.2 Scientific Roll Assembly and Offset Matching
Work roll offset distance determines rolling stability during forward and reverse operation. Reasonable offset design ensures work rolls closely fit the side support system. This condition must hold even under maximum tension difference.
During assembly, operators select matched work roll diameters and optimal offset values. They refer to the grinding dimensions of backup rolls, side support rolls and intermediate rolls. The offset structure generates lateral component force from rolling load. It presses work rolls firmly against side support rolls and improves lateral stability.
The friction driving force of backup rolls produces outward tangential force during forward rolling. This trend weakens lateral support stability. Donc, the offset distance must guarantee positive supporting force from side support rolls to work rolls during forward rolling. This standard eliminates slipping and instability risks in reversible rolling.
## 4. Conclusion
With the continuous upgrading of modern thickness and flatness control technology, the application scope of the offset eight-high cold rolling mill faces certain restrictions. It still retains unique advantages in thin strip and hard metal rolling.
To adapt to increasingly strict market quality requirements, the offset eight-high cold rolling mill needs further optimization. It should improve flatness control accuracy and roll system stability. After targeted technical improvement, this multi-purpose rolling equipment will maintain high application value. It will also have broad promotion prospects in high-precision cold rolling production.
