Cooling Bed of Rebar Rolling Mill

The cooling bed is the working table of the metallurgical steel rolling industry to cool rolled products (rebar, round steel, steel pipe, etc.). The cooling bed is composed of the mechanical transmission system, water cooling system, cooling bed table, fixed support, etc. The cooling beds mainly include gear extraction cooling bed, walking beam cooling bed, claw type cooling bed, carrying chain cooling bed, rolling plate cooling bed, etc.

The cooling bed is one of the indispensable auxiliary equipment in small and medium-sized bar mill plants. Its function is to cut double-length bar rolled by rolling mill through flying shear, transport and unload it to the rack of cooling bed for cooling, so as to reduce its temperature from 900 ℃ to 100 ~ 300 ℃. Then it is collected and sent to output roller table by unloading device of cooling bed, and then it is sent to cold shear for cutting into fixed-length finished product by output roller table. The design quality and installation accuracy of the cooling bed directly determine the final quality of products.

Equipment Composition

The cooling bed consists of three parts: cooling bed feeding device, serrated walking beam cooling bed body, cooling bed unloading device and output roller table. The cooling bed charging device is a difficult point in the design of the cooling bed, and it is also a throat device.

Feeding Device

The feeding device is composed of a roll-in roller table, a straightening plate, a brake apron and a pneumatic steel splitting device. The structural feature of the feeding device is that a hydraulic cylinder is arranged every 12m in the length direction of 120m, all hydraulic cylinders operate synchronously, and the skirt board is moved up and down at the same time through the connecting rod and the synchronous shaft.

The performance characteristics of the feeding device are: a proximity switch is set on the synchronization axis to detect and control the lifting position of the lifting skirt to ensure accurate and reliable actions; the control valve of the hydraulic cylinder is configured nearby to minimize pressure errors and ensure synchronization of actions The direct-acting relief valve and anti-cavitation valve are set in the control circuit, and the optimized design of the hydraulic cylinder can effectively solve the problem of damage to the hydraulic system caused by the huge impact and ensure the safety of the hydraulic system.

The side drive of the hydraulic cylinder, the synchronous shaft is arranged outside the high-temperature zone. When each hydraulic cylinder is kept in sync, each shaft bears only the torsional stress required for the lifting of the lifting skirt plate, while the synchronous shaft is rotated. There is almost no inertial force. Because the inertial force of the skirt is distributed to each hydraulic cylinder, the force state of the mechanism is greatly improved. 

There is an adjustment mechanism on the connecting rod, which can easily adjust the up and down position of the skirt board. Due to the optimized design of the mechanical structure, the electrical control adopts computational control technology, and the hydraulic system adopts safety measures, the device is endowed with superior performance. The levelness and straightness of all skirts are reliably guaranteed during work.

Classification

Cooling beds mainly include pull-tooth cooling beds, rack stepping cooling beds, claw cooling beds, carrier chain cooling beds, and rolling plate cooling beds.

Working Principle

The rolled products are transported into the cooling bed through the roller table, and then the workpieces arranged on the cooling bed are gradually moved to the top of the cooling bed by means of rack and gear stepping, so as to achieve the cooling effect of the workpiece.

The Main Purpose

The cooling bed equipment is mainly used for on-line slow natural cooling of rolled steel plates. In the profile production line, the cooling bed also has a pre-bending function for the profile to prevent the profile from being irregularly bent due to unequal quality in the natural cooling process. Cooling beds are mainly used in the steel industry, metallurgical industry, etc.

Operating Procedures

1. During the rolling process, the operators of the cooling bed are strictly forbidden to go on the cooling bed, and are not allowed to walk on the roller table or rack.

2. If there are accidents such as chaotic bed during production, it must be processed and cleared after the rolling stop.

3. The sampling of the cooling bed should use special tools for sampling.

4. Pay attention to the surrounding conditions during operation, and it is strictly forbidden for unrelated persons to enter the dangerous area of ​​the large cooling bed.

5. Hot waste products caused by accidents such as chaotic beds must be removed on duty to ensure that the environment around the cooling bed is tidy.

If you are interested in cooling beds for rolling mill machine, please mail at marketing2@hanrm.com.

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Heating Furnace What You Need to Know

1. Heating furnace's purpose

The heating furnace is to heat the billet to a uniform temperature (austenite structure) suitable for rolling. After the temperature increases, the first thing is to improve the plasticity of the steel and reduce the deformation resistance, so that the steel is easy to deform. For example, the deformation resistance of T12 steel is about 600 MPa at room temperature, and it decreases to about 30 MPa when heated to 1200 ℃, which is only one twentieth of that at room temperature.

For the steel with proper heating temperature, a larger reduction can be used during rolling, which can reduce the equipment accidents caused by wear and impact, improve the productivity and operation rate of the rolling mill, and reduce the rolling energy consumption. Secondly, heating can improve the internal structure and properties of the billet. The inhomogeneous structure and non-metallic inclusions are homogenized by the diffusion of high-temperature heating. The heating temperature and uniformity are the marks of heating quality. The steel with good heating quality is easy to obtain the finished product with the correct section shape and accurate geometric size.

2. Heating furnace's heating process

The heating temperature of the billet includes surface temperature, temperature difference along with section and temperature difference along billet length. The final heating temperature of the billet in the furnace is determined after considering the actual situation of the rolling process, structural characteristics of the rolling mill and heating furnace. The time required for heating to the specified temperature depends on the billet size, steel grade, temperature system adopted and some other conditions.

The billet gets heat by convection and radiation in the heating furnaces. The former is that the furnace gas washes the billet surface, while the latter is that the furnace gas and hot lining radiate heat. Along the length direction, our furnace is divided into three sections: preheating section, heating section and soaking section. When the billet enters the preheating section of the heating furnace, the heat flux increases gradually. When the billet reaches the second heating section, the heat flux basically remains unchanged. When the billet reaches the soaking section, the heat flux decreases gradually.

In the soaking zone, the surface temperature of the billet remains basically unchanged, while the temperature difference of the cross-section decreases gradually, and the heat from the billet surface diffuses to the interior in the way of heat conduction. The smaller the heat flux to the billet surface, the larger the heating area, the smaller the section size of the billet and the greater the thermal conductivity of steel, the smaller the section temperature difference. Generally, the heating time of billets with large section is longer than that of billets with small section, and that of alloy steel is longer than that of carbon steel.

3. Heating furnace pressure system

The size and distribution of the heating furnace pressure are an important means to adjust the temperature field, control the flame and atmosphere in the furnace. It affects the heating speed and quality, and also affects the utilization of fuel. In particular, the furnace pressure at the discharge section of the furnace is particularly important.

The heating furnace pressure should be set at 0 ~ 30Pa higher than atmospheric pressure. If the furnace pressure is too high, the charging port, discharging port, observation hole and other opening parts will be exposed to fire. The results are as follows: (1) the furnace gas loss increases, which increases the heat loss; (2) SO 2 and other harmful gases enter the workshop, which pollutes the working environment; (3) the furnace wall, nearby steel structure or mechanical equipment at the burning part are damaged or deformed. On the contrary, if the furnace pressure is too low, the absorption of cold air in the workshop will make (1) the furnace temperature decrease and the fuel consumption increase; (2) the cooling of billet by low-temperature air will lead to uneven temperature; (3) the increase of oxygen content in the furnace gas will lead to the increase of burning loss.

4. Heating furnace combustion system:

The basic requirement is to ensure that the fuel is completely burned in the heating furnaces and the air coefficient α is small. Excess air leads to a large amount of flue gas and more heat carried away; insufficient air leads to incomplete combustion in the furnace, which also increases heat loss.

Inquiry about heating furnaces, please mail at marketing2@hanrm.com.

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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.

What we can do:

We are specialized in manufacturing high-speed morgan wire rod mill, high-speed rebar rolling mill, TMT rolling mill, high-speed gearbox, hard-faced gearbox.

We also provide complete design for your rolling mill workshop, not only turnkey project but also tailor-made service.

And we provide all the parts for roughing rolling mill, intermediate rolling mill process, including pinch roll, all kinds of shears, laying head, all of these crucial parts work extremely precisely and reliably.

If necessary, please feel free to contact me. Email: marketing2@hanrm.com