Repair Method and Operation Process of Rolling Mill Roll

During the operation of the rolling mill, the roll is easy to be damaged. In order to repair the roll body timely and effectively, it is necessary to judge and analyze from the determination of service life, the identification of crack depth, turning crack and other aspects, so that the rolling mill can return to normal.

Because there is no good method to detect the crack depth of the rolling mill roll, the length of service life can only be judged and determined according to the experience, the type of rolling mill, the type of alloy produced and the roughness of the roll surface. According to the theory, the correct service life should be before the crack depth reaches 3 mm, beyond which the roller surface should be grinded, otherwise it is easy to cause the roller sleeve to burst.

In general, if the crack on the rolling mill roll is open, its depth is deeper than tortoise crack or other microcracks, and the crack width is also larger. Therefore, the longest circumferential crack and the widest crack on the roll surface must be found out correspondingly. Through these cracks, the minimum cutting amount can be determined, and the magnetic particle inspection can be used for crack areas.

In order to ensure the safety, the turning depth of the rolling mill roll needs to add 0.5mm to the crack depth in general, and the roughness of the roll surface after turning shall not be less than 6.3; the surface roughness of the roll surface after grinding shall reach 0.8, which can be compared with the standard block or measured with the roughness detector.


When the defects of the rolling mill roll are turned, magnetic particle inspection shall still be carried out to ensure that all micro-cracks have been eliminated. If there are still micro-cracks, turning is still required. It should be noted that every time the repair is made, the record should be made and kept for the daily backup.

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How to Adjust the Roll Gap?

Adjusting roll hole shape and controlling plate shape are mainly based on rolled products. The rolls are supported and held in a fixed position in the rolling mill. Roller bearings have a large workload and vary widely, so a small coefficient of friction is required.

After determining the products rolled by the rolling mill, the line speed of the rolling mill can be basically confirmed. The hardness of the raw material is measurable. The rolling stock of the rolling mill is determined by changing the plastic deformation size.

How to configure the rolls according to the hole process? Generally, the newly installed rolling mill has a running-in process. During the running-in process, the rolls are run at no load, and the running speed is 50%, 65%, 75%, and 85% in stages. Different rolling mills have different materials and specifications for rolls according to different rolling products.

For example, the continuous casting machine and rolling mill has a daily output of 100 tons and a rolling speed of 15-25 m / s. Rough rolling efficiency accounts for 30% -40%, intermediate rolling efficiency accounts for 50% -60%, and rough rolling efficiency reaches 95%. After the rolling mill is installed, the large and small teeth of the reducer and gearbox need to mesh, the rolling speed is too fast, and the torque is enhanced. After the rolling mill runs normally for 30 consecutive days, stop the rolling mill to check the meshing of the large and small gears. When everything is normal, the rolling speed can be increased.

Under normal circumstances, there is no need to adjust the rolling speed. In the rolling mill, the rolls are constantly worn during operation. In order to maintain the stable operation of the rolling mill when the rolls are under controllable rolling requirements, the rolls must be repaired in time. In severe cases, the rolls need to be replaced.

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Solution to High Temperature of Rolling Mill

In summer, we should pay special attention to the safe operation of the rolling mill in the high-temperature natural environment, improve its maintenance and repair, because the temperature rise is more likely to cause small problems of the rolling mill. First of all, the cooling circulating water of rolling mill roll can not be less, the average temperature is high, and the cooling circulating water volatilizes too fast, which should be added frequently. And check the body of water in time, and if the water body smells smelly, it is necessary to dismantle and replace the cooling circulating water, throw away the sewage, replace the saponification liquid again, and add the water that must be accounted for.

If the rolling mill works for a long time, it will also cause the temperature of the motor to rise, so you have to touch the bearing end cover shell of the motor by hand to see if the temperature is too high. If the temperature is high, it needs to be shut down to reduce the temperature of the motor before it works without overload.

The cycloid reducer is used in the rolling mill, and the installation method is inverted. In high temperature, the temperature rise will occur, which makes the viscosity of the lubricating grease lower and lower, and it will flow into the bearing end cover, resulting in the lack of lubricating grease in the cycloid reducer, leading to the temperature rise of the reducer, and the more severe one will burn the reducer. Therefore, it is necessary to often check whether there is a lack of grease in the reducer to ensure the normal operation of the reducer.

In summer, it is also necessary to check the route of household electrical appliances of rolling mills. The rise of average temperature will accelerate the embrittlement of the route, which is easy to cause short-circuit fault. However, the actual operating staff of the rolling mill shall wear rubber gloves during safe operation, and the temperature of spiral gear after cold rolling is too high, which will burn their hands.

In addition, the roll of the rolling mill shall be cleaned. At the end of daily work and after standby, the roll must be removed. Clean the roller surface with a clean towel and wipe off the air oxide skin adhered on the surface, so as to improve the service life of the roller.

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4. Causes of Piling up of Steel

5. What Are the Key Points of Rolling Mill Hoisting?

Rolling Mill Packaging, Transportation and Storage Requirements

We have introduced a lot of knowledge about the use and operation of rolling mills. However, if we want to ensure the normal use of the rolling mill machine, we need to comply with certain requirements for its packaging, transportation, and storage. Now we will introduce this aspect for you, hoping to provide a reference. 

First of all, let's take a look at how to properly pack the rolling mill. In general, since the equipment is shipped in bulk during transportation, it is required to wrap the motor part with a plastic cloth during packaging so as to prevent damage due to moisture. In addition, the shaft head of all exposed parts also needs to be wrapped with plastic cloth to prevent damage and corrosion.

As for other parts of the rolling mill, it is necessary to apply antirust oil in advance to avoid rusting in early summer. Therefore, in the process of transportation, what should we pay attention to? When loading, unloading and hoisting the equipment, it is necessary to operate it carefully and ensure that the rope used has sufficient strength. At the same time, it should be noted that the protruding part of the equipment shall not be damaged during lifting, and it is better to use some soft things for protection.

In the process of transportation, it is necessary to ensure that the rolling mill machine is fixed so as to avoid sloshing, and no strong vibration or impact. During the driving process, the speed should be uniform and the driving should be stable. In addition, we also need to pay attention to some problems when storing the product.

When the rolling mill arrives, we need to remove it from the box and check it carefully. The rolling mill equipment is then placed in a ventilated and dry room to prevent rust damage. If long-term storage is required, it should be cleaned and rust-proofed.

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How to Avoid Accidents in Cold Rolling?

In many steel rolling plants, especially in cold rolling production, accidents are most likely to occur, including operation accidents, equipment accidents, and quality accidents. All those directly affect equipment, quality, and output. So when accidents occur, remedies should be taken immediately.

1. The rolling piece is deviated, which usually occurs when the head is worn or the tail deviates when the belt is worn. It is caused by the uneven thickness of the incoming material, unskillful operation, old-fashioned roll holes, electrical problems, etc. The slight deviation during threading can be eliminated by timely adjusting and screwing down; for serious deviation, it is necessary to cut the strip steel in front of the frame, find out the cause of deviation, and then re-thread the strip; if it is found that the strip tail is deviated during tailing off, it is necessary to stop immediately, and lift the screw-down according to the situation to make the strip steel pass or cut it. When rolling a very thin strip, the roll is easy to be damaged due to deviation, so special attention should be paid.

　　

2. The rolling mill runout. Rolling mill runout usually occurs during high-speed rolling of extremely thin strip. Because of the beating, the thickness of the strip fluctuates, it is easy to break the strip. Therefore, once the rolling mill has obvious beating sound, the rolling speed shall be reduced immediately to eliminate the vibration. There are many reasons for the runout, such as high rolling speed, thin product thickness, low rolling pressure and small deformation of the finished pass, large tension before the strip steel, too good or too bad lubrication, insufficient roughness of the working roll, damage of the supporting roll, sudden change of various rolling parameters, large gap between the roll bearing and the bearing seat, etc. The cause of rolling mill vibration is complex and it is not easy to make a correct judgment. Through careful search and analysis, before the correct conclusion is reached, only the method of limiting rolling speed is used to prevent the occurrence of run out. 

2. The broken strip of rolled piece. There are many reasons for the broken strip of the rolled piece. Generally, it can be concluded as four kinds: defective incoming material, poor weld quality, misoperation, electrical and mechanical failure. In case of strip breaking, stop the mill immediately to reduce the loss. Serious belt breaking not only makes the work roll and even the support roll bond seriously, but also makes the treatment of the waste belt and the extraction of the work roll very difficult after bonding. Moreover, the treatment time is long and the labor intensity is large. After the belt breaking treatment, the equipment shall be inspected. The surface quality of the first coil of steel to be rolled after roll change shall be checked carefully. For the coil with weld, the mark of the weld position shall be accurate and clear. The rolling speed shall be reduced before the weld passes through the rolling mill. The steel coil with defects must be rolled slowly to minimize the occurrence of accidents in cold rolling production.

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The Operating Rules of Rolling Mills

Eight Precautions for Rolling Mills

1. Every time the rolling mill appears to be jogging, it must not exceed one second. The worm gear should be adjusted in place, and the adjustment amount should be completely equal on both sides to avoid side bends.

2. When operating the cold rolling mill, there should be a special person to guard, and there should be no phenomenon of no one to guard, so as not to find the equipment failure and not find it in time.

3. Under normal circumstances, a single cold rolling mill should not exceed 40% of the aluminum plate in a single thickness.

4. There must be no debris in the production line.

5. Adjust the amount of reduction and the number of passes according to the material of the incoming material and the capacity of the rolling mill.

6. When using a cold rolling mill, the relevant technical parameters must be in full compliance with the requirements, and it should not be operated under load.

7. Rolls should not be subjected to more serious wear and should be replaced if they are found to be worn out.

8. During the whole rolling process, if the roll affects the surface quality of the rolled piece due to wear, or the size and precision, the roll should be replaced immediately, and after the roll is replaced, the driving operation must be guaranteed 2 to 3 minutes.

Precautions of Cold Rolling Mill

1. Preparation for Startup

Let the rolling mill equipment idle for about 10 minutes. During this period, observe whether the device is running normally, and add lubricating oil and rolling oil to lubricate the equipment properly according to the regulations.

2. Precautions before Unloading

(1) The press should be raised to the specified position, the reel should be retracted into position, and the hydraulic truck should be prepared in advance for auxiliary discharge.

(2) The aluminum plate plug should be inserted into the jaws successfully, otherwise, it will be difficult to insert.

3. Some Considerations

(1) The time for each jog of the machine should not exceed one second. The turbine should be adjusted to reduce the turbine. The adjustment amount on both sides should be equal to avoid the side bend of the rolled piece.

(2) When the cold rolling mill is running, someone should be responsible for guarding to prevent problems.

(3) Generally speaking, the thickness of one rolling of a single cold rolling mill should not exceed 40% of the aluminum plate.

(4) There should be no debris in the production line.

(5) Appropriate adjustments should be made to the pass and reduction depending on the material of the incoming material and the capacity of the rolling mill.

(6) The use of cold rolling mills should meet the requirements of the main technical parameters and should not be overloaded.

(7) The mill roll should not have serious wear and should be replaced if necessary.

(8) In the rolling process, if the wear of the mill roll has affected the surface quality and dimensional accuracy of the rolled piece, the roll should be changed immediately. After changing the roller, it should idle for 2 to 3 minutes.

(9) If there is any phenomenon such as tearing or skewing of the rolled piece, the hand can not be used. It should be stopped first and then taken out.

(10) Rolled finished products or semi-finished products should be filled out with relevant records and stacked in batches.

How to Improve the Operation Efficiency of High-speed Rolling Mill?

High-speed rolling mill is similar to the conventional rolling mill. The ultimate goal is to obtain the required size of the rolled piece by rolling mill calendering. In rolling operation, in order to improve the operation efficiency of the high-speed rolling mill, it is necessary to take corresponding improvement measures.

       

The operation efficiency of high-speed rolling mill is mostly affected by unplanned parking, other equipment delays, roll and bearing replacement, and other process maintenance. Therefore, we need to improve the operation efficiency of the high-speed rolling mill in a planned way. The specific operations are as follows:

1. The material of rolls should be screened according to the requirements of the rolled parts to improve the fatigue strength and service life of the rolls. 

2. Inspect the wear of roll and guide from time to time.

3. Inverse injection process of bearing lubricant from inside to outside to inside, so as to reduce the pollution of dust to bearing.

4. Using ultrasonic technology to inspect and analyze rolls.

5. The dry lubricating oil point has been modified. At present, the dry oil is added from the high-pressure zone. The amount of added oil increases from six cycles of raw materials to eleven cycles, and the thin oil lubrication is a 15-minute cycle. The cumulative effect of these changes can reduce the bearing temperature by several degrees Celsius.

With the upgrading of the steel rolling industry, new problems will arise, and we need to optimize and adjust the rolling process according to the actual situation at any time. This process requires us to explore step by step for a long time.

If you are interested in our rolling mill machine, please feel free to mail at marketing2@hanrm.com, we will make the customized solution for you.

How to Carry out Daily Maintenance of Rolling Mill?

Rolling mills are widely used in the steel industry. In order to ensure the smooth running of daily work, daily maintenance is particularly important. It should be noted that the daily maintenance of the rolling mills will affect the service life. So how to carry out the daily maintenance of the rolling mill, how to operate?

Every day, the rolling mill is inspected for oil, water and gas leakage and overheating of the machine parts; reducing the loss caused by the illegal operation of the equipment or maintenance, and when lifting the rubber rolls, take necessary maintenance measures at the chain, rope and end of the roll surface.

The automatic thickness control system on the rolling mill is operated strictly in accordance with the rolling mill operating process and operating methods. The gearbox should be cleaned at least once a quarter. When the roll is fed to the extreme position, special attention must be paid to the safe operation of the rolling mill. Care should be taken when performing the rolling mill operation to prevent the hand from being pressed by the steel plate and being fed together with the steel. When using the aircraft hoisting mill for inspection, be careful not to collide with the machine.

In the rolling operation, the personnel of each department should coordinate with each other and listen to the command of the person in charge of the rolling mill production line. In the rolling process, the roller and the raceway are in line contact or repaired line contact, and the radial bearing capacity is large and is suitable for bearing heavy load and impact load. If irregular noise is found, such as the abnormal phenomenon that the roller cannot be touched by the sudden release of the load after the steel bar is interrupted, it should be stopped immediately and checked, and the steel rolling production line can be completely stopped before being repaired. After the main drive of the motor is stopped, the upper and lower rolls can be lifted and lowered. When cleaning, firstly, in the hot state, stop the oil drain screw on the side of the gearbox, and turn the rollover of the roll and the lifting of the upper roll.

After the end of rolling, the finished material should be cleared, and the equipment maintenance and repair work should be done. In order to strengthen the effective management of the equipment, the equipment utilization rate should be improved, and the power supply should be turned off in time.

The Adjustment of Steel Rolling Mill

Before the steel rolling mill is used, the roll pass, controlling plate shape and backup roll should be adjusted according to the requirement; and the fixed position of the rolls in the rolling mill should be maintained. The workload of the roll bearing is heavy and varies greatly, so the friction coefficient of the bearing is required to be small.

After determining the product rolled by the rolling mill, the line speed of the rolling mill can be basically determined. The hardness of the raw materials is measurable. The rolling stock of the rolling mill is determined by changing the plastic deformation size.
Usually, the newly installed steel rolling mill has a running-in process. During the running-in process, the rolls are operated in a second operation, and the operation speed is 50%, 65%, 75%, and 85%. Different steel rolling mill models use the rolls with different materials and specifications for different rolling products.

After the steel rolling mill is installed, the gears of the reducer and the gearbox need to have meshed, the rolling speed is too fast, and the torque is enhanced. After the normal operation of the rolling mill for 30 days, stop the rolling mill and check the meshing of the large and small gears, and waits for everything to be normal, the rolling speed can be increased.

Under normal circumstances, it is not necessary to adjust the rolling speed. The rolls in the steel rolling mill is constantly worn during the running process. In order to keep the rolling mill stable in the controlled rolling requirements, the roll must be repaired in time, and the rolls need to be replaced in serious cases.

The steel rolling mill needs labor, even the automated equipment needs to be monitored manually in the console. The conveyor roller and shearing machine located in the automatic rolling mill must be strictly controlled during operation to avoid the failure of stacking steel or jamming. If the wear of roll and guide exceeds the specified range, it needs to be replaced. 

The rolling of the billet causes the roll to be squeezed instantaneously, and the bearing is subjected to correspondingly high pressure, thereby affecting the product size of the rolled steel. We may also need to make in-depth improvements, but the ultimate goal is to get better steel rolling mill equipment.

We can supply rebar rolling mill and wire rod mill equipment designing, manufacturing, installation, and commission of the equipment with “turn-key” service.

We can also design, manufacture and revamp other non-standard equipment according to the requirements of users.

If interested, please mail at marketing2@hanrm.com or kerrirollingmill@gmail.com.

How to Package Steel?

Steel should be packaged according to national standards and contracting requirements. In general, the contents of the package are (except for special requirements in the contract):

(1) Profiled steel with a diameter or thickness of less than 30 mm and a thin plate with a thickness of less than 4 mm shall be delivered in bundles. Each bundle shall be of the same batch number, and each bundle shall be affixed with at least two signs. The nameplate shall indicate the manufacturer's name, steel number, furnace (can) number, specifications, etc.

(2) Steels with a diameter or thickness equal to or greater than 30 mm may be delivered in bundles or may not be delivered in bundles. For bundles of steel, each bundle shall be affixed with at least two signs, steel may not be stamped. Bundles of steel that do not carry signs should be stamped or marked on the top steel or plate of each bundle. Steel that is not bundled must be stamped on each steel or steel plate.

(3) After the steel is packaged (or not supplied in bundles), it shall be painted according to the relevant standards.

(4) Steel delivered in bundles, each bundle shall be bundled with wire at not less than two places.

(5) The weight of each bundle shall not exceed 80kg when manually loaded and unloaded, and shall not exceed 5t when mechanically loaded and unloaded. After the consent of the purchaser, the manual loading and unloading may not exceed 130kg per bundle, and the mechanical loading and unloading may not exceed 10t per bundle.

In order to facilitate the distinction and use, all kinds of steel should have the mark, that is, the stamp.

The stamp shall be applied to the end face of the steel or to the surface of the steel 100 mm from the end of the steel. The contents include steel grade, furnace number, tank number, spindle number, section number, etc. For steel stamps with a diameter or side length greater than 40 mm, it can be punched on the end face. For steel stamps with a diameter or side length of less than 40 mm, it can be hit on the end face, or on an iron plate, and the iron plate is hung on the steel.

We can supply rebar rolling mill and wire rod mill equipment designing, manufacturing, installation, and commission of the equipment with “turn-key” service.

We can also design, manufacture and revamp other non-standard equipment according to the requirements of users.

If interested, please mail at marketing2@hanrm.com.

Hot Rolling Principle of Rolling Mill

Hot rolling is based on slabs (mainly continuous casting billets), which are heated to form strips by roughing rolling mills and finishing rolling mills. The hot steel strip from the last rolling mill of the finishing mill is cooled to a set temperature by laminar flow, rolled into a steel coil by a coiler, and the cooled steel coil is subjected to different finishing operations according to different needs of users. Lines (flat, straight, cross-cut or slit, inspection, weighing, packaging and marking) are processed into steel, flat and slit steel strips.

Since hot-rolled steel sheet products have high strength, good toughness, easy processing and good weldability, they are widely used in shipbuilding, automobiles, bridges, construction, machinery, pressure vessels and other manufacturing industries.

With the increasing maturity of new technologies such as hot-rolling dimensional accuracy, plate shape and surface quality, and the advent of new products, hot-rolled steel sheets and strip products have become more and more widely used and are becoming more and more competitive in the market. Hot rolling steel products can be divided into ordinary carbon structural steel, low alloy steel, alloy steel according to its material and performance.
     

According to the use, hot-rolled products can be divided into cold forming steel, structural steel, automobile structural steel, corrosion-resistant structural steel, mechanical structural steel, a welded gas cylinder and pressure vessel steel, and pipeline steel.

The advantage of hot rolling is that it can eliminate certain defects in the cast metal, such as welding the pores, refining coarse grains and changing the distribution of inclusions. The compactness and mechanical properties of the metal are improved. Secondly, the raw material (steel ingot or billet) is increased in thermoplasticity, and the deformation resistance is lowered. Therefore, the amount of deformation can be increased during rolling, which is advantageous for improving productivity. In addition, due to the reduced metal deformation resistance, the requirements for the rolling equipment can be correspondingly lower, so that the cost of the equipment can be reduced and the energy consumption of the motor can be greatly reduced.　　

The disadvantage of hot rolling is that high-temperature rolling produces iron oxide scale so that the surface of the metal is not smooth and clean; the size of the product is not accurate enough, and the mechanical properties are not as good as cold working.

We can supply high-speed wire rod mill equipment designing, manufacturing, installation, and commission of the equipment with “turn-key” service.

We can also design, manufacture and revamp other non-standard equipment according to the requirements of users.

If interested, please mail at marketing2@hanrm.com.