ABSTRACT: The causes of residual oil on the surface of rolled copper strip are analyzed, and the methods of oil removal are discussed from the aspects of technology and equipment. It is suggested that the base oil with low viscosity should be selected to reduce the content of alcohol, acid, fat and other additives in the rolling oil. On the equipment, anti-splash baffle, strong suction smoke exhaust device, roll gap purging device, oil extruding roller and purging beam are used.

1.Introduction

The problem of oil removal from the surface of copper strip is a difficult problem in the production of copper strip. Due to the high-speed rolling of copper strip, a large amount of deformation heat is produced, and the cooling effect of finished rolled copper strip is not as good as that of emulsion due to the use of full oil lubrication. If the amount of residual oil is not up to the standard, it will not only increase the difficulty of degreasing, but also cause the waste of rolling oil and pollute the environment.

To improve the oil removal effect, two aspects should be considered: on the one hand, to reduce the difficulty of oil removal from the process; on the other hand, to configure effective oil removal equipment.

Generally, the boundary lubrication is improved by adding extreme pressure agent or antiwear agent. During Rolling, the extreme pressure agent forms a very thin and high strength boundary film on the metal surface of the rolling area, which not only prevents the adhesion between the roll and the Strip surface, but also makes the Strip be fully compacted, and finally the surface of the finished product is close to the Surface roughness. It is difficult to remove all the residual oil from the Strip surface, so the volatility and distillation range should be considered when determining the composition of base oil and additives to reduce the residual spot after annealing.

It is suggested that low viscosity base oil should be selected from the aspect of oil removal. At the same time, the content of alcohol, acid and fat in rolling oil should be reduced to reduce its kinematic viscosity. The reduction of the viscosity of the rolling oil can not only improve the cooling effect on the roll and Strip, but also reduce the flow of process lubrication. Properly increasing the temperature of the rolling oil can also reduce its viscosity. At present, the kinematic viscosity is 4.5% at 40 °C. 3 MM 2/s rolling oil with FLASH POINT OF 130 °C. In addition, antioxidants are added to the rolling oil to reduce the oxidation of the rolling oil during purging and hot rolling deformation.

The flow rate of process lubrication is determined by the mill power. On the premise of not affecting the coiling effect, the rolling speed of the first few passes is increased appropriately, the residual oil can be reduced to some extent by adjusting the reduction of the last pass, the rolling speed and the rolling Torque to reduce the last pass lubrication flow.

2.Deoiling device

Based on the observation and analysis of the rolling oil trend in several production sites, several main sources of residual oil on the surface of the Strip for export are obtained: Firstly, the passage formed between the two sides of the Strip, the roll surface of the upper and lower working rolls, and the roll neck, the high-speed rotating roller throws the oil out of the channel and splashes it onto the Strip, as shown in Fig. 1. Second, the upper supporting roller throws the oil sprayed onto the roll surface from the inlet side to the outlet side and then onto the strip, the oil droplets from the inlet side of the reversing mill that splash onto the stand, and the oil droplets from the scavenging of the residual oil and the condensation of the vapor from the oil itself, are dripping onto the Strip during the next pass of the Strip, the thickness of the rolling oil is the smallest at the gap, and the surface tension is larger after the rolling oil is collected behind the gap, so the residual oil can not be removed.

Therefore, this paper adopts the following measures to reduce residual oil.

2.1 The splash guard is shown in

 Fig. 2. The Splash Guard is arranged in the frame and consists of a lead screw, a guide block and a door curtain fixed on the guide block at one end and on the frame at the other end. The door curtain is connected by a plurality of door plates through hinges. When the guide block moves along the Strip width, the door curtain can expand and contract with the guide block, and the position of the guide block is determined by the Strip width. In this way, the spilled rolling oil beyond the width of the Strip can be sealed in the frame, thereby reducing the residual oil on the surface of the Strip.

2.2 roll cleaner

The roller cleaner is mounted on a bearing housing or frame and consists of a cross member and a scraper, as shown in Fig. 3. Scraper shape and back-up roll body and roll neck shape, can be along back-up roll radial expansion, after adjusting the back-up uniform pressure on the roll surface, can block most of the back-up roll surface to the exit side of the rolling oil.

2.3 smoke extraction and cleaning

Smoke exhaust device suction force is very strong, when the oil mist is not attached to the rack, the oil mist will be discharged, at the same time regular cleaning equipment residual oil, mainly cleaning the outer part of the craft lubrication rack.

2.4 roll gap purge

During the rolling process, the thickness of oil film decreases rapidly after entering the plastic deformation zone and reaches the minimum at the center of the roller. By setting a gap blowing device at the exit side as shown in Fig. 4, when the Compressed air is ejected from the gap to the surface of the work roll, due to the high speed rotation of the work roll and the wall attachment of the airflow, the airflow will form a "protective cover" on the roll surface, which can prevent the spilled oil from falling on the Strip surface in a certain area, and the high-speed airflow will form a negative pressure area, and part of the residual oil from the strip outlet will be removed.

2.5 extruding roller and blowing beam

After rolling, there will be a part of residual oil not removed. A pair of extruding rollers and four blowing beams with a row of nozzles are arranged at the entrance and exit respectively to remove oil as shown in Fig. 5. Most of the residual oil can be removed by the extruding roller when the effect of oil removal is not ideal. The disadvantage is that the oil film is difficult to be removed after the roller.

The oil extruding roller adopts large diameter steel roller and is driven by motor to prevent the Strip from slipping when it is accelerated or decelerated. The surface of the roller forms a triangle with the strip, a shape cavity, and the blowing beam adjusts an appropriate angle to eject compressed air into the cavity, a gas curtain is formed in the triangle area, and part of the residual oil is blocked in front of the gas curtain; the Oil extruding roller is driven up and down by the oil cylinder, and the residual oil is blocked after forming certain pressure on the Strip. In addition, the entrance, the side squeezes the oil roller also to be able to block the rolling oil to a certain extent outward, the splash function.

3.Conclusion

On the basis of reducing the difficulty of oil removal in rolling process, the oil removal device is needed to remove the residual oil. The anti-splash guide plate, roller cleaner and smoke exhaust are easy to install, the cost is low, and the base oil on the surface of the Strip can be reduced to the maximum, and the difficulty of the subsequent oil removal can be reduced. The roller gap purging device has good oil removal effect, but it can be selected under the allowable condition because of the limited space in the frame of General Copper Rolling Mill. The extruding roller can only extrude most of the residual oil in use, and can meet the lower oil removal index. If we want to achieve better oil removal effect, we need to add a purging device. In use, purging will accelerate the oxidation of the rolled oil, so it is better to use low, high pressure flow purging. The deoiling effect is reflected by many factors. In the deoiling design of copper rolling mill, the deoiling effect can be achieved by the combination adjustment of the deoiling device according to the specific conditions of the process and rolling mill. 

Source: Yunza Steel