Advantages and Disadvantages of Carbide Rolls

Precautions for the Use of Carbide Rolls

1. After the carbide roll is installed, the carbide roll worker should carefully check the roll cooling water pipe and position, and then connect the introduced hose to the special water pipe. After the hose is connected, the interface must be tied tightly with lead wire to prevent the roll from being in a state of no cooling water after falling off, which may cause serious consequences.

2. During the rolling process of the roll, pay close attention to the running state of the bearing seat, and stop and check if any abnormality is found.

3. In order to reduce the occurrence of fatigue cracks, the surface of the roll ring must be cooled with water to reduce the thermal expansion of the surface. When the rolled piece is in contact with the roll ring surface, the temperature of the roll ring surface can reach 500-600℃. Cooling water sprayed on the hot roll ring surface will form a layer of gas film covering the surface of the roll ring, which will seriously affect the cooling effect. It shows that when the cooling air pressure reaches more than 0.5Mpa, the gas film will be broken, so that the cooling effect will be improved.

Low-speed rolling mill roll ring cooling water pressure should not be too high, in order to prevent the cooling water from splashing and fail to cool down, the cooling water pressure should be 3-4Mpa, and the water volume should be 40-50 cubic meters per hour. At the same time, in order to improve the cooling effect, the coverage of the cooling water sprayed by the cooling water nozzle should be correspondingly overlapped, and the outlet of the cooling water column should be aligned with the exit of the roll ring. Carbide roller rings also have special requirements for water acidity: PH≥7.2 is weakly alkaline and kept clean.

4. Water cooling of carbide rolls is an extremely important means during use. The better the cooling condition, the higher the tonnage of carbide rolls, otherwise the rolls will easily burst. Therefore, during the rolling process, each production shift should stop every 4 hours to check whether the position of the dedicated cooling water pipe is moving and whether the water pipe nozzle is blocked, and then drive the rolling.

5. When handing over the shift, the operator should carefully check the wear of the rolling slot and whether there are minor cracks. If the above happens, they should report to the quality supervisor of the dispatching room, and then replace the carbide roll groove after confirmation.

6. During the rolling process, the roll gap adjustment must not be zero-gap, that is, the roll must not be touched during rolling.

7. Once the sampling room is found to be abnormal in rolling products, the person in charge should notify the dispatching room, and the dispatching room should stop for inspection immediately after receiving the notice. If the key block of the roll matrix is protruding, the screws are loose, and the rolling groove has slight cracks, it is necessary to replace the rolling groove and the cemented carbide roll.

8. It is recommended that the single groove-rated rolling tonnage of ф5—ф8 wire is 800—1000 tons. The single groove rolling tonnage cannot be excessively higher than the specified tonnage, otherwise, the surface micro-cracks will cause the roll ring to crack, even if it does not crack, it will increase the amount of roll ring grinding, resulting in uneconomical.

Advantages and Disadvantages of Applying Carbide Rolls on Bar and Wire Rod Rolling Mills

Due to the advantages of high hardness and good wear resistance, the application of cemented carbide roll rings on bar and wire rod rolling mills shows the following advantages:

1. Improve the quality of steel products, so that the surface quality and tolerance dimensions of the steel are completely improved, and the negative deviation control is very accurate;

2. Reduce the number of slot changes, roll changes and downtime, increase the utilization rate and output of the rolling mill, and enable the rolling mill to create greater economic benefits in the same time;

3. Reduce the scrap rate of products and reduce the labor intensity of the production workshop;

4. Reducing production costs is an effective way for enterprises to increase efficiency;

5. Conducive to the application of endless rolling technology.

The disadvantages are: due to the high hardness and brittleness of cemented carbide roll ring and high sensitivity to cracks, it is difficult to maintain, and the requirement for cooling water is high in use, and it can not bear the rapid cooling and heating, otherwise it is easy to cause destructive accidents.

If you are looking for carbide rolls, please contact me.
Email: marketing2@hanrm.com.

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Roller FAQs

What Are the Types of Rolling Mill Roll?

Rolling mill roll is a tool for plastic deformation of rolled metal, which is an important consumption part to determine the efficiency of rolling mill and the quality of rolled products. Roll is an important part of rolling mill. The rolling pressure of a pair or group of rollers is used to roll steel. It mainly bears the influence of static and dynamic load, wear and temperature change during rolling.

There are many kinds of rolls, including cast steel rolls, cast iron rolls and forging rolls. There are also a few cemented carbide rolls (tungsten steel rolls) on profile mills.

According to the molding method:

Casting roll and forging roll.
Casting roll refers to the type of roll made by casting molten steel or molten iron directly.
Casting roll can be divided into cast steel roll and cast iron roll according to material, and can be divided into integral casting roll and compound casting roll according to the manufacturing method.
The forging roll is classified as follows according to the material:
(1) Forging alloy steel roll;
(2) Forging semi-steel roll;
(3) Forging semi high-speed steel roll;
(4) Forging white cast iron roll.

According to the process method:

Integral roll, metallurgical composite roll and combined roll.

1. Compared with the composite roll, the outer layer and core of the roll body and the roll neck of the integral roll are cast or forged by single material. The different microstructure and properties of the outer layer and neck of the roll body are controlled and adjusted by casting or forging process and heat treatment process. Both forging roll and static casting roll belong to integral roll. Integral roll can be divided into integral casting roll and integral forging roll;

2. There are mainly three kinds of metallurgical composite casting roll, such as semi washing composite casting, overflow (full washing) composite casting and centrifugal composite casting. In addition, there are some special composite methods such as CPC－Continuous Pouring Process for Cladding, spray deposition, HIP－Hot Isostatically Pressed. The composite roll is mainly inlaid composite roll.

According to manufacturing materials:

Cast steel rolls, cast iron rolls and forging rolls.

The commonly used heat treatment types of roller are stress relief annealing, isothermal spheroidizing annealing, diffusion annealing, normalizing, tempering, quenching and cryogenic treatment.

According to the shape of roller body:

There are different classification methods for rollers. The former is mainly used for plate, strip, profile and wire production, while the latter is mainly used for pipe production.

According to contact with rolled piece or not:

It is divided into work roll and backup roll. The roll that directly contacts the rolled piece is called the work roll; the roll which is placed on the back or side of the work roll and does not directly contact the workpiece is called the backup roll in order to increase the stiffness and strength of the work roll.

According to the rack used:

It is divided into primary roll, roughing roll, intermediate roll and finishing roll according to the use stand. According to the variety of rolled products, it can be divided into strip roll, rail beam roll, wire roller and pipe roll, etc. It can also be divided into hot roll and cold roll according to the state of rolled piece during rolling.


According to hardness value:

(1) The shore hardness of soft roll is about 30 ~ 40, which is used in embryo opening machine and roughing mill of large section steel rolling mill.

(2) The shore hardness of semi-hard roll is about 40 ~ 60. It is used in roughing mill of large, medium and small section mills and plate mills.

(3) The shore hardness of hard surface roll is about 60 ~ 85, which is used for roughing mill of thin plate, medium plate, medium section steel and small section steel mill and the support roll of four high rolling mill.

(4) The shore hardness of super hard roll is about 85 ~ 100, which is used in cold rolling mill.

According to the type of rolling mill:
(1) Flat roll. That is, the roll body of plate and strip mill is cylindrical. Generally, the roll of hot rolling plate rolling mill is made into micro concave shape, which can obtain better shape when heated; the roll of cold rolling plate rolling mill is made of micro convex shape, and the roll will bend during rolling to obtain good shape.

(2) Grooved roll. It is used for rolling large, medium and small section steel, wire rod and blooming. A groove is carved on the roll surface to form the rolled piece.

(3) Special roll. It is used in steel tube rolling mill, wheel rolling mill, steel ball rolling mill and piercing mill. The rolls of this kind of rolling mill have various shapes. For example, the rolls rolled by the principle of cross rolling in steel pipe rolling are conical, waist drum or disc.

 

If you are interested in our rolling mill rolls, please send your inquiry to marketing2@hanrm.com.

Whatsapp / Wechat: +8618392033938

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6. Failure Analysis of Cold Mill Roll

7. The Cause of Rolling Mill Rolls Breakage

8. Material Selection of Rolling Mill Rolls

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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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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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