CN101972782A - Device and method for cooling intermediate rolled blank of hot rolled strip - Google Patents

Abstract

The invention provides a cooling device and a cooling method for a hot-rolled strip rolling intermediate billet. The device includes an upper header installed above the roller table and a lower header installed between the roller tables; wherein, the upper header and the lower header are equipped with nozzles and opening and closing control valves, and are connected with the water supply pipeline of the header. The workshop circulating water system is connected; the flow control valve is set on the header water supply pipeline. The on-off control valve and the flow control valve are controlled by a programmable controller. Between every two roller tables, multiple groups of cooling headers with low flow rate that can be individually controlled to open and close are arranged, and the intermediate billet is cooled by spraying water, and the cooling speed is dynamically controlled according to the transfer speed of the intermediate billet. The characteristics of the invention are: relatively simple equipment, convenient maintenance, low requirements on water quality, good water flow stability, not limited by roughing mill speed up and steel throwing deceleration, high production efficiency; using rolling mill cooling water, no separate water supply and drainage system; the grains of the intermediate billet are significantly refined to improve the mechanical properties of the steel plate.

Description

Cooling device and cooling method for hot-rolled strip rolling intermediate billet

technical field

The invention belongs to the cooling technology of steel rolling production, in particular to a cooling device and cooling method for hot-rolled strip steel rolling intermediate blank.

Background technique

In order to improve the strength and toughness of steel, the austenite grains are refined by controlled rolling or the dislocation slip bands inside the deformed austenite grains are increased, that is, the effective grain boundary area is increased, which is the ferrite nucleation during phase transformation. Provide more and more dispersed nucleation sites, and obtain finely dispersed ferrite and pearlite or bainite structures. Refining ferrite grains can not only increase the strength of steel, but also improve the toughness of steel. However, the development of the traditional controlled rolling theory has not surpassed the three-stage controlled rolling technology, namely: rolling in the austenite recrystallization zone, rolling in the austenite non-recrystallization zone, and rolling in the α+γ two-phase zone. . Due to the rolling temperature angle in the α+γ two-phase region, the deformation resistance is large, and considering the adverse effects on the load of the rolling mill, the industry generally adopts the rough rolling stage of rolling in the austenite recrystallization region and the austenite rolling stage. Finishing stage of rolling in the non-recrystallized zone. This means that the controlled rolling process must avoid the partial recrystallization zone between rough rolling and finish rolling, so as to minimize the negative impact of the mixed crystal structure on the mechanical properties.

At present, the method commonly used at home and abroad is to allow the steel plate after rough rolling to be air-cooled on the conveying roller table until the temperature drops to the non-recrystallized area before finishing rolling. The cooling speed of the steel plate in the air is slow and time-consuming, and the production rhythm of the rolling mill is slow, which seriously restricts the economic efficiency of steel production. For the hot-rolled strip steel production line with hot coil boxes between the roughing mill and the finishing mill, due to the short length of the intermediate roller table, the cooling capacity of the intermediate billet is insufficient, resulting in a reduction in production efficiency or restrictions on the specifications of the rolled steel grades.

The invention patent "Laminar Flow Cooling Method of Hot-rolled Strip Intermediate Billet" (application number: 02144825.6) discloses a hot-rolled strip intermediate billet cooling method, which is characterized in that a laminar cooling device is installed at the exit of the roughing mill to form a length is the laminar flow cooling zone of L, by calculating the time for each point of the intermediate billet to pass through the laminar flow cooling zone and the total time for a piece of intermediate billet to pass through the laminar flow cooling zone, according to the steel type and specification of the intermediate billet, it is calculated to make the intermediate billet Cool the cooling water flow to the required temperature, and use the laminar flow cooling device to cool the intermediate billet.

In the field of hot-rolled strip steel production, there are strict requirements on the temperature drop in the cooling process. Generally, the difference between the actual temperature after cooling and the target temperature is required to be within 10°C. However, the existing cooling methods for hot-rolled strip intermediate blanks all use a set of coolers between two roller tables. The cooling intensity is too large, and the temperature control accuracy is generally around 20°C, which is difficult to meet the above requirements. The above laminar flow cooling method for the hot-rolled strip intermediate billet requires relatively complicated equipment, and requires the construction of water tanks outside and inside the workshop, and has high requirements for cooling water quality, and requires the establishment of a separate water circulation system, resulting in a large overall investment. restrictions on its use.

Invention patent "An intermediate billet cooling system and cooling control process" (application number/patent number: 200910104025) discloses an intermediate billet cooling system, which is characterized in that an air mist cooling device is installed between the roughing mill and the finishing mill ontology. The air mist cooling device body is composed of an upper cooling header and a lower cooling header, and an air mist nozzle and a compressed air pipe are installed on the cooling water pipes of the upper cooling header and the lower cooling header; the cooling water pipe and the compressed air pipe The on-off control valve and the flow control valve are connected with the control valve station. The cooling headers installed near the roller tables before and after the rolling mill control the intermediate billet gas mist cooling process through the water mist control technology sprayed on the cooling headers. The invention can be used in medium and thick plate production lines.

In the production field of medium and thick plates, especially wide and thick plates, due to the slow temperature drop in the cooling process and the difficulty in controlling the uniformity of the thickness direction and width direction of the steel plate, many difficulties have been brought to the realization of the controlled cooling of the intermediate billet. The intermediate billet cooling system in the form of gas mist cooling mentioned above has relatively complicated equipment, and has high requirements on the cleanliness of the air and water channels and the pressure control range, resulting in a large overall investment and limiting its use to a certain extent.

Contents of the invention

The purpose of the present invention is to provide an equipment with relatively simple manufacturing process, convenient maintenance, low requirements on water quality, good water flow stability, reducing the waiting time of the intermediate billet between rough rolling and finishing rolling, speeding up the rolling rhythm, and improving production. Efficient cooling device and cooling method for hot-rolled strip rolling intermediate billet.

The technical solution of the present invention is: a cooling device for hot-rolled strip rolling intermediate billet, the device includes an upper header installed above the roller tables and a lower header installed between the roller tables; wherein, the upper header Nozzles and opening and closing control valves are provided on the header and the lower header, and are connected to the workshop circulating water system through the header water supply pipeline; a flow control valve is set on the header water supply pipeline. The on-off control valve and the flow control valve are controlled by a programmable controller.

Another object of the present invention is to provide a cooling method of a cooling device for hot-rolled strip rolling intermediate billet, the specific steps are as follows:

Step 1: install 24-48 sets of cooling devices on the conveying roller table at the exit of the roughing mill to form a cooling area, and send the intermediate billet rolled by the roughing mill with a thickness of 20 to 60 mm into the cooling area;

Step 2: The computer calculates the amount of cooling water according to the thickness, width, steel type and temperature of the intermediate billet, and the temperature to which the intermediate billet is required to be cooled;

Step 3: The computer controls the opening and closing quantity of the opening and closing control valve and the flow rate of the flow control valve through the programmable controller, and the upper and lower headers implement impact jets to control the cooling of the intermediate billet, and the cooling rate is controlled at 3 to 30°C/s. After reaching the set temperature, enter the next process.

Further, the steps also include that there will be deceleration or acceleration changes in the transmission process of the intermediate billet during the hot strip rolling process, and according to the speed change, the combination of adjusting the water supply flow of the header and changing the opening and closing of the header is used to control the accuracy and adjust the cooling speed dynamic control.

The cooling pressure of the impinging jet water is controlled to be 0.3-1.0 MPa.

The advantages of the present invention are:

1. Since the scattered cooling headers are not easy to over-cool the surface of the steel plate, the cooling in the thickness direction of the steel plate is relatively uniform. This advantage is very important for hot-rolled strip steel.

2. The equipment manufacturing process is relatively simple, easy to maintain, low in water quality requirements, and good in water flow stability.

3. Due to the arrangement of multiple groups of cooling headers that can be individually controlled to open and close with a small flow rate between every two roller tables, and the cooling speed is dynamically controlled according to the transmission speed of the intermediate billet, the control of the steel plate temperature Accuracy is improved.

4. The adjustment of cooling capacity is relatively flexible. The method of adjusting the water supply flow of the header and changing the opening and closing combination of the header can be used to improve the control accuracy of the cooling temperature of the steel plate and adjust the cooling speed.

5. When the intermediate billet is controlled and cooled, it is not limited by the speed up of the roughing mill and the deceleration of the throwing steel, and the production efficiency is high.

6. After controlled cooling, the grains of the intermediate billet are significantly refined, which improves the mechanical properties of the steel plate.

7. The requirements for cooling water quality are low, the existing rolling mill in the workshop can be directly used to cool the medium-pressure water, and the used cooling water can directly enter the circulating water system of the workshop, without a separate water supply and drainage system, which greatly reduces the investment in the water system.

8. The control pressure of the pressure water in the impact jet cooling is 0.3-1.0MPa, and the available pressure range is wide.

9. High cooling intensity and high utilization rate of cooling water. Under the condition of the same specific water volume, cooling water with a certain pressure will take away more heat per unit volume, increasing the proportion of nucleate boiling heat transfer, increasing the heat transfer coefficient and cooling speed, especially for thick intermediate billets. Faster cooling capacity is required.

The method of the invention can be widely used in the field of hot-rolled steel strip production, has a wide application range, and can meet the layout requirements of different rolling workshops. This method can be realized on the hot-rolled strip steel production line that adopts the warming roller table or the hot coil box between the roughing and finishing mills.

Description of drawings

Fig. 1 is a schematic diagram of the header layout of the cooling (IC) device of the present invention.

Fig. 2 is a schematic diagram of the arrangement of a cooling (IC) device between the roughing mill and the hot coil box according to the present invention.

Fig. 3 is a schematic diagram of the arrangement of an intermediate billet controlled cooling (IC) device between the roughing mill and the finishing mill in the present invention.

In the picture:

1. Rough rolling mill 2. Cooling device

3. Cutting shears 4. Finishing mill

5. Hot coil box 6. Roller table

7. Upper header 8. Lower header

9. Intermediate billet 10. Water supply pipeline

11. Flow regulating valve 12. Opening and closing control valve

13. Nozzle 14. Programmable controller

Detailed ways

The technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

As shown in Figure 1, it is a cooling device for hot strip rolling intermediate billet. The upper header 7 of the device is installed above the roller table 6 through a bracket, and the lower header 8 is installed between the roller tables 6. Both the upper header 7 and the lower header 8 are provided with nozzles 13 and opening and closing control valves 12. And be connected with workshop circulating water system by header water supply pipeline 10; The flow control valve 11 is arranged on the header water supply pipeline 10; On-off control valve 12 and flow control valve 11 are connected with programmable controller 14 by cable, can The programmable controller 14 is connected with the computer of the automatic control system through a communication cable, and the programmable controller 14 makes the upper header 7 and the lower header 8 evenly spray jet water to cool the intermediate billet.

Figure 2 is a schematic diagram of the layout of the cooling (IC) device installed between the roughing mill and the hot coil box according to the present invention. As shown in FIG. 2 , the transmission roller table between the rough rolling mill 1 and the hot coil box 5 is provided with a cooling device 2 , and the transmission roller table between the hot coil box 5 and the finishing mill 4 is provided with a cropping shear 3 .

Figure 3 is a schematic diagram of the arrangement of cooling (IC) devices between the rough rolling mill and the finishing mill in the present invention. As shown in FIG. 3 , the transfer roller table between the roughing mill 1 and the finishing mill 4 is provided with a cooling device 2 and a cropping shear 3 .

Example one:

To produce 18.5mm thick × 80 pipeline steel by controlled rolling process, the arrangement shown in Figure 3 is used to implement controlled cooling of the intermediate billet. 48 groups of cooling devices are installed on the conveying roller table at the exit of the roughing mill to form a cooling area. The cooling water pressure is 1.0MPa. First, the raw billet is rolled by the roughing mill into an intermediate billet with a thickness of 55mm. The temperature of the intermediate billet is 1030-1050°C. While rolling, it is sent into the cooling area; the computer calculates the amount of cooling water according to the thickness, width, steel type and temperature of the intermediate billet, and the target cooling temperature of the intermediate billet, and controls the opening and closing of the control valve through the programmable controller. The number of opening and closing and the flow rate of the flow control valve, the upper and lower headers implement impact jets to control the cooling of the intermediate billet, and the cooling speed is controlled at 3°C/s; when the head of the intermediate billet enters the cooling area, the speed is stable, and there is no need to reduce the cooling header; The speed decreases when the intermediate billet is thrown, and the computer dynamically adjusts the number of opening and closing groups of headers according to the speed of the intermediate billet. During the deceleration period of intermediate billet throwing, the number of header groups is reduced until the tail of the intermediate billet completely passes through the cooling area. After the intermediate billet reaches the set temperature of 920-950°C after cooling, it enters the next process-cutting and finishing rolling.

Example two:

The ferritic rolling process produces IF steel with a thickness of 2.0 mm, and the layout shown in Figure 2 is used to implement controlled cooling of the intermediate billet. 32 groups of cooling devices are installed on the conveying roller table at the exit of the roughing mill to form a cooling area, the cooling water pressure is 0.40MPa, the raw billet is first rolled by the roughing mill into an intermediate billet with a thickness of 22mm, and the temperature of the intermediate billet is 1020-1050°C. While rolling, it is sent into the cooling area; the computer calculates the amount of cooling water according to the thickness, width, steel type and temperature of the intermediate billet, and the target cooling temperature of the intermediate billet, and the opening and closing control valve is operated by the programmable controller. The closing quantity and the flow rate of the flow control valve, the upper and lower headers implement impact jets to control the cooling rate of the intermediate billet at 20°C/s; when the head of the intermediate billet enters the cooling area, the speed still increases, and the computer adjusts the temperature according to the speed of the intermediate billet. The number of header opening and closing groups is dynamically adjusted, and the number of header groups is increased during the rising speed rolling period of the intermediate billet; the speed is reduced when the intermediate billet is thrown, and the computer dynamically adjusts the number of header opening and closing groups according to the speed of the intermediate billet During the deceleration period of steel throwing, reduce the number of header groups until the tail of the intermediate billet completely passes through the cooling area. After the intermediate billet reaches the set temperature of 840-860°C after cooling, it enters the next process - coiling, uncoiling, head cutting and finishing rolling.

Example three:

The production of 3.0mm welded bottle steel HP295 adopts the arrangement shown in Figure 2 to implement controlled cooling of the intermediate billet. 36 groups of cooling devices are installed on the conveying roller table at the exit of the roughing mill to form a cooling area. The cooling water pressure is 0.60MPa. First, the roughing mill rolls the raw billet into an intermediate billet with a thickness of 32mm. The temperature of the intermediate billet is 1010-1040°C. While rolling, it is sent into the cooling area; the computer calculates the amount of cooling water according to the thickness, width, steel type and temperature of the intermediate billet, and the target cooling temperature of the intermediate billet, and the opening and closing control valve is operated by the programmable controller. The closing quantity and the flow rate of the flow control valve, the upper and lower headers implement impact jets to control the cooling of the intermediate billet, and the cooling speed is controlled at 30°C/s; when the head of the intermediate billet enters the cooling area, the speed still increases. The number of header opening and closing groups is dynamically adjusted, and the number of header groups is increased during the rising speed rolling period of the intermediate billet; the speed is reduced when the intermediate billet is thrown, and the computer dynamically adjusts the number of header opening and closing groups according to the speed of the intermediate billet. During the deceleration period of billet throwing, reduce the number of header groups until the tail of the intermediate billet completely passes through the cooling area. After the intermediate billet reaches the set temperature of 930-950°C after cooling, it enters the next process-cutting and finishing rolling.

Claims (4)

1. A cooling device for hot-rolled steel strip rolling intermediate billet: the device includes an upper header (7) installed above the roller table and a lower header (8) installed between the roller table; it is characterized in that the Nozzles (13) and on-off control valves (12) are provided on the upper header (7) and the lower header (8), and are connected to the workshop circulating water system through the header water supply pipeline (10); A flow control valve (11) is arranged on the pipe water supply line (10), and the opening and closing control valve (12) and the flow control valve (11) are controlled by a programmable controller (14). 2. the cooling method of the cooling device of the hot-rolled steel strip rolling intermediate billet according to claim 1: the concrete steps are as follows: Step 1: install 24-48 sets of cooling devices on the conveying roller table at the exit of the roughing mill to form a cooling area, and send the intermediate billet rolled by the roughing mill with a thickness of 20 to 60 mm into the cooling area; Step 2: The computer calculates the amount of cooling water according to the thickness, width, steel type and temperature of the intermediate billet, and the temperature to which the intermediate billet is required to be cooled; Step 3: The computer controls the opening and closing quantity of the opening and closing control valve and the flow rate of the flow control valve through the programmable controller, implements impact jet control cooling on the intermediate billet, and controls the cooling rate at 3-30°C/s to reach the set After the temperature is reached, enter the next process. 3. cooling method according to claim 2, is characterized in that, described step also comprises, the transmission of intermediate slab in the process of hot-rolling steel strip has deceleration or acceleration, and described step also comprises, in the process of hot-rolling steel strip The transmission of the intermediate billet will change in deceleration or acceleration, and the dynamic control of changing the opening and closing combination of the header combined with the control accuracy and adjusting the cooling speed can be adopted. 4. The cooling method according to claim 2, characterized in that the cooling pressure of the impinging jet water is controlled to be 0.3-1.0 MPa.

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