Reasons and Solutions for the Piling of Wire Rod Rolling

1. Piling of Steel Head

The Reason:

1) The friction of the rolling groove after changing the roll and groove is too small, causing the head of the rolled product to slip;

2) The head of the rolled product is tilted out of the rack, causing it to fail to bite into the downstream rack or the head guide position smoothly;

3) There are foreign objects in the rolling groove or guide groove;

4) The billet is severely out-of-square, unable to enter the rolling mill or take out the outlet pipe;

5) The blank is split out of the guide or wrapped around the roller.

Solution:

1) Increase the groove friction when changing rolls and grooves. Grind the grooves with the grinder or use spot welding, and turn off the cooling water of the rolls until they are completely bitten.

2) Check whether the guide base is loose and whether the rolling line is centered, and replace the old guide in time.

3) In the rolling process, timely clean up the oxide scale;

4) In the rolling process, unqualified billets are removed in time, and splitting occurs. Emergency stops should be taken as soon as possible to reduce the waste steel processing time.


2. Piling of the Middle and End of the Rolled Piece

The Reason:

1) Due to improper roll gap setting caused by improper size of rolled products, stacking steel;

2) Defects of the billet, such as inclusions, bubbles, etc., are broken during the rolling process and cause stacking of steel;

3) The speed of the rolling mill is improperly designed, and it is in the state of stacking and rolling. When the first half of the rolled product is maintained by the front rolling mill to maintain micro-tension rolling, when the tail of the rolled product leaves the front rolling mill, the tension is suddenly lost there, causing the stack at the stand tail;

4) Sudden increase or decrease in speed of the rack motor caused the stacking of steel;

5) The roll was suddenly broken or the guides were severely damaged in the first few passes, which caused the stacking of steel.


Solution:

1) After changing rollers and grooves, accurately set the groove bottom, correctly measure the diameter and speed of the rollers, and reduce speed errors

2) Strengthen the inspection of unqualified blanks;

3) Correctly adjust the tension between each frame;

4) Inspect electrical equipment and replace damaged electrical components;

5) Check the amount of roll cooling water, adjust the steel temperature, and prohibit rolling of low temperature steel and blackhead steel.


3. Piling steel between Finishing Mill Stands

The Main Reason:

1) The guide wheel does not rotate or the bearing burns;

2) splits of rolled products;

3) The guide or roller ring is incorrectly installed;

4) Improper roll gap setting or improper incoming size;

5) the roller ring is broken;

6) The broken line causes the rolling line to break automatically.


Solution:

1) Replace the guide, and strengthen the correctness of the guide installation;

2) Strengthen the blank inspection and lengthen the cutting head;

3) Recheck and adjust the roll gap;

4) Replace the roller ring and check the cooling water pipe at the same time;

5) Check the switch at the fishing line pendant, check whether there is scrap steel in the guide of the finishing mill. If there is any, it means that the previous one has piled steel in the finishing mill, and reset the roll gap in the finishing mill.

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Classification and Development of Direct Rolling and Hot Feeding

The real direct rolling is to roll the continuous casting slab sent from the continuous casting machine directly into the final product without any other heating or heating process. However, for many years, most of the production process research and tests for producing high-quality products have reheated or reheated the continuous casting slab before rolling.

Continuous casting slab hot feeding and hot charging and direct rolling technology are new technologies under development, and the specific characteristics are as follows:

Continuous casting slabs are directly rolled without heating or supplemental heating, referred to as CC-FDR, and are classified into 1 type. Under the condition that the surface temperature is above 820 ° C (the core is above 960 ° C), the continuous casting slab is directly sent to the rolling mill without any form of heating and supplemental heating, and without building a heating furnace. The slab has not undergone the γ-α-γ phase transformation recrystallization process before rolling, and the as-cast coarse austenite grains are still retained. The trace elements Nb and V do not have the precipitation and re-dissolution processes in conventional cold-loading furnaces, so they must be developed. A new rolling process to obtain a grain-refined structure.

Continuous cast slab rolling, referred to as CC-DR, is classified into 2 types. The continuous casting slab is directly sent to the rolling mill through the corner heating device during the conveying process without passing through the heating furnace under the conditions above A3 temperature.

Continuous casting slab hot direct rolling, referred to as CC-HDR, is classified into 3 categories. The continuous slab temperature is above A3. The slab does not pass through the heating furnace. During the conveying process, the rollable temperature is reached by supplementary heating and soaking, and it is directly sent to the rolling mill for rolling.

Continuous hot-rolling of continuous casting slabs, referred to as CC-DHCR, is classified into 4 categories. The continuous casting slab temperature is below A3 and above A1, and the casting slab is directly sent to a heating furnace for heating and rolling. Due to the high temperature of hot charging, it is also called red delivery, and the heating furnace acts as a buffer between the continuous caster and the rolling mill.

Continuous hot-rolling of continuous casting slabs, referred to as CC-DHCR, is classified into 4 categories. The continuous casting slab temperature is below A3 and above A1, and the casting slab is directly sent to a heating furnace for heating and rolling. Due to the high temperature of hot charging, it is also called red delivery, and the heating furnace acts as a buffer between the continuous caster and the rolling mill.

The continuous casting slab cold rolling furnace is heated and rolled, referred to as CC-CCR, and is classified into 6 categories. This is the conventional rolling method when there is no hot-feed and hot-fill process.

Solution to Slow Start of Rolling Mill Machine

The speed at which the rolling mill machine is started during operation has a very important effect on the efficient work of the rolling mill. If the starting speed of the rolling mill machine is slow when it is ready for operation, it means that there is a significant deficiency in the performance of the rolling mill equipment, which will affect the working efficiency of the rolling mill. The force between the billet or rolled product and the roll cannot reach good condition.

The rolled piece cannot be fully rolled in the rolling mill. Under this condition, the power consumption of the rolling mill machine is several times higher than usual. If it happens often, the speed of the rolling mill cannot be effectively started, the efficiency of the billet or rolled product will become lower and lower. For steel rolling mill equipment, if it cannot be started quickly and overloaded, the billet rolling speed will be too slow. Here, let me analyze the reasons and solutions for the slow startup speed.

Before starting the rolling mill machine, it is necessary to verify the power of the equipment motor, rolling speed, product specifications, hole technology, etc., ensuring that the amount of billet retransmission does not exceed the bearing capacity of the rolling mill equipment, otherwise the startup speed of the equipment will slow down. We also need to check the rolling mill bearings to see if the bearings are adequately lubricated. If the lubrication is not sufficient, the rolling mill machine's start-up will also slow down or even malfunction.

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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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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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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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