CN102756000A - Jet flow cooling method and device in narrow slit water jacket passage of steel plate - Google Patents

Abstract

The invention discloses a jet flow cooling method in a steel plate narrow slit water jacket channel. A flat rectangular hollow tubular water jacket is placed around the hot-rolled steel plate in the cooling zone. A slit channel is formed, and the upper wall and the lower wall of the water jacket are equipped with inclined jet nozzles with openings facing inward. The generated water vapor jointly forms a vapor-liquid two-phase flow, then flows out from the port of the narrow slit channel and flows into a circulating water storage tank arranged at the port of the water jacket; the invention also provides a cooling device for implementing the method. The invention simultaneously achieves two technical effects of fast cooling and uniform cooling, and has the advantages of low water consumption, convenient adjustment of cooling capacity, and easy installation of the device.

Description

Jet cooling method and device in steel plate narrow slit water jacket channel

technical field

The invention relates to a cooling method and device for a hot-rolled steel plate, in particular to a method and a device for jet cooling in a narrow slit water jacket channel for on-line production of a hot-rolled steel plate, and belongs to the technical field of metal processing.

Background technique

Controlled rolling and controlled cooling technology is a new technology of rolling steel production in continuous casting system newly developed at home and abroad for more than 20 years. With the application of modern equipment and detection and control methods in steel rolling production, the controlled rolling and controlled cooling technology is becoming more and more perfect, especially in the production of medium and thick steel plates. Controlled rolling has a great impact on the output of the rolling mill, so each plate manufacturer has made every effort to develop a cross-rolling method suitable for its own factory conditions, and equipped with the necessary post-rolling cooling device, so that the steel product can be strengthened and toughened, and deformation can be reduced And reduce production costs, improve product competitiveness in the market. At present, iron and steel manufacturers at home and abroad almost without exception use jet (jet) impact boiling technology to cool the rolled high-temperature steel plate, but jet cooling also has two shortcomings: one is large water consumption and power consumption; two It is difficult to achieve uniform cooling. In addition, the cooling capacity of jet cooling has basically reached the limit, and it is difficult to further improve it.

The online high-temperature steel plate under the jet cooling formed by the cooling water is divided into two parts: the jet stagnation zone and the non-stagnation zone, both of which are in the film boiling heat transfer mode. The water flow in the stagnation zone directly impacts the high-temperature steel plate, and there is a stable thin steam film between the steel plate and the jet water, and the heat transfer rate is very high; in the non-stagnation zone, there is no pressure of the jet water, and the steam rises in this area, and the liquid is at a certain temperature. In a sputtering state, the average vapor film is very thick and the heat transfer rate is small. Since the non-stagnation zone accounts for the main part of the online steel plate area, the heat transfer rate of the overall steel plate is not high and the cooling is not uniform. In particular, there is a serious temperature difference between the stagnation zone and the non-stagnation zone, which will cause deformation, residual stress and characteristic deviation of the steel plate due to uneven cooling, resulting in a lower product qualification rate. Although jet cooling performance can be improved by increasing jet velocity, flow rate, and number of nozzles, jet cooling has produced technical bottlenecks such as insufficient cooling rate and uneven cooling when developing products with better performance.

After searching the existing technology, it was found that the patent application number: 200580051372.6, and the patent name is: cooling device for thick steel plate; the method described in this patent is a typical traditional jet cooling steel plate method. The ratio of the impact area of the flow to the area of the steel plate, the adjustment of the jet water volume and the type of the nozzle are used to control the cooling range, and strive to make the upper and lower surfaces of the steel plate and all parts of the cooling uniform and ensure a stable cooling capacity. However, its disadvantage is that the cooling water that vertically hits the surface of the steel plate has poor fluidity in a short period of time, and forms a gas film after stagnation, resulting in transitional boiling and heat transfer, making it difficult to ensure uniform cooling.

Patent application number: 02818457.2, the patent name is: steel plate cooling method and its device, the method described in the patent is to set a horizontally placed slit nozzle on the upper side of the steel plate, and the cooling water and the steel plate perform horizontal forced convection heat exchange, while the steel plate A plurality of circular tube laminar flow nozzles with conduits are installed on the lower side to cool the steel plate surface by vertical jet flow. By controlling the laminar water flow of the circular tubes in real time, the overcooling of the front end of the steel plate can be prevented, in order to achieve the purpose of uniform cooling. However, this method also has the disadvantages of large water demand and difficult control of the cooling rate of the upper and lower surfaces.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the prior art, and provide a jet cooling method and device in a steel plate narrow slit water jacket channel, which adopts a mixed cooling method of jet flow and forced convection in the narrow slit channel to improve the average heat transfer cooling capacity and uniform cooling purposes.

The present invention is achieved through the following technical solutions:

A jet cooling method in a steel plate narrow slit water jacket channel, in which a flat rectangular hollow tubular water jacket is placed around the hot-rolled steel plate in the cooling zone, and a narrow slit channel is formed between the upper and lower walls of the water jacket and the hot-rolled steel plate The upper wall and the lower wall of the water jacket are equipped with inclined jet nozzles with openings facing inward. The gas-liquid two-phase flow is formed together, and then flows out from the port of the narrow slit channel and flows into the circulating water storage tank arranged at the port of the water jacket.

The injection direction of the cooling water is opposite to the rolling direction of the hot-rolled steel plate, and the included angle formed with the surface of the hot-rolled steel plate is 30-60°.

The cooling water is a columnar flow with a spray velocity of 6-10m/s.

The pressure of the cooling water is 0.2-0.8MPa, and the temperature is 20-80°C.

Another technical scheme of the present invention is:

A steel plate slit water jacket channel jet cooling device for implementing the above method, which includes a high-pressure water tank, a regulating valve, a plurality of jet nozzles, a water jacket and a water storage tank. Around the rolled steel plate, a narrow channel is formed between the upper and lower walls of the water jacket and the hot-rolled steel plate, and the openings of the multiple jet nozzles are installed on the upper and lower walls of the water jacket inclined inwardly. Cooling water is stored and connected to the plurality of jet nozzles through the regulating valve, and the water storage tank is arranged at the port of the water jacket.

The water jacket is made of anti-corrosion material, and the anti-corrosion material is stainless steel or carbon steel plate with anti-corrosion layer.

The height of the space between the upper wall and the lower wall of the water jacket is no more than 2.5 times the thickness of the hot-rolled steel plate.

The plurality of jet nozzles are arranged in sections on the upper wall and the lower wall of the water jacket and arranged symmetrically up and down, 8-32 sets of jet nozzles are arranged in the width direction of the water jacket, and more than 6 rows of jet nozzles are arranged in the length direction .

The inclination angle of the jet nozzle is 30-60°, and the inner diameter of the nozzle is 6-20mm.

The present invention proposes a new technology of rapid cooling and controlled cooling of high-temperature steel plates—jet flow cooling technology in narrow slit channels, which is characterized in that hot-rolled steel plates pass through the water jacket, and the upper and lower cooling water jets and narrow slit channels The internal forced convection forms a high-speed gas-liquid two-phase flow, and cools the hot-rolled steel plate, achieving two technical effects of rapid cooling and uniform cooling.

The heat transfer mechanism of the jet cooling technology in the narrow slot channel is still forced convective film boiling: there is a thin steam film on the surface of the high-temperature steel plate, and the outside of the steam film is high-speed flowing cooling water, forming a high-speed vapor-liquid two-phase flow . Different from the general forced convective film boiling, since the cooling water is constantly sprayed through the nozzles at various positions in the channel, the water flow in the entire channel is in a supercooled state, and the cooling water continuously annihilates the water vapor, and the water along the channel The thickness of the steam film will not change, keeping the heat transfer rate stable along the channel; in addition, the jet water continuously breaks through the steam film and impacts the surface of the steel plate, reducing the average steam film thickness, thereby increasing the heat transfer rate. At the same time, the jet water causes the steam film Strong disturbance also increases the heat transfer rate. Since there is no longer a strict distinction between the stagnation zone and the non-stagnation zone, the cooling rate of the entire heat transfer surface is relatively close. Jet cooling in a narrow channel can be regarded as a cooling technology in which the entire heat transfer surface is approximately in the stagnation zone. This cooling technology can achieve the purpose of efficient and uniform cooling.

Compared with the prior art, the cooling capacity of the present invention greatly exceeds the average cooling capacity of the simple jet cooling mode or the simple forced convection cooling mode. The difference in cooling rate is very small, achieving a good uniform cooling effect, and the invention has the advantages of low water consumption and convenient adjustment of cooling capacity.

Description of drawings

Fig. 1 is a structural schematic diagram of the present invention.

FIG. 2 is a top view of FIG. 1 .

Fig. 3 is a sectional view along line A-A of Fig. 1 .

Fig. 4 is a B-B sectional view of Fig. 1 .

Detailed ways

The preferred modes of the invention will be described in detail below in conjunction with the accompanying drawings, but the protection scope of the present invention is not limited to the following embodiments.

The embodiment shown in Fig. 1 and Fig. 2 shows that the jet cooling device in the channel of the steel plate slit water jacket includes a high-pressure water tank, a regulating valve, a plurality of jet nozzles 5, a water jacket 4 and a water storage tank 1.

The water jacket 4 is a flat rectangular hollow tubular member (like a matchbox jacket), and is placed around the hot-rolled steel plate 3. The upper and lower walls of the water jacket 4 form a narrow gap between the upper and lower walls of the hot-rolled steel plate 3. slot channel 2, the height of the space between the upper wall and the lower wall of the water jacket 4 is not more than 2.5 times the thickness of the hot-rolled steel plate 3; the water jacket 4 is made of various anti-corrosion materials, due to cooling on the production line Water often contains corrosive substances such as chlorine, so the anti-corrosion material can be stainless steel or carbon steel plate with anti-corrosion layer, such as carbon steel plate plated with zinc, chromium or similar materials or steel plate with anti-corrosion coating. The water jacket 4 is welded in an appropriate size according to the size of the hot-rolled steel plate to be cooled, and requires high welding quality, safety and reliability. In this embodiment, the water jacket 4 is welded with zinc-nickel steel plate material, and has a total length of 1.8m.

The plurality of jet nozzles 5 open inwardly and are installed obliquely on the upper wall and the lower wall of the water jacket 4. The inclination angle of the jet nozzles 5 is 30-60°. The upper wall and the lower wall of 4 are arranged in sections and symmetrically arranged up and down (see Figure 2). The arrangement is carried out according to the length and cooling requirements of the hot-rolled steel plate 3. Generally, 8-32 groups of jets are arranged in the width direction of the water jacket 4. The nozzles 5 are arranged in more than 6 rows of jet nozzles 5 in the length direction. The jet nozzle 5 can be a circular tube jet nozzle, and its inner diameter can be adjusted according to needs, generally 6-20mm; the jet nozzle 5 can also be an oval tube, a long strip tube or a special-shaped tube jet nozzle. In this embodiment, 9 jet nozzles 5 are arranged in the width direction of the hot-rolled steel plate 3, and in order to ensure the flow velocity and water quantity, the pipe diameter is selected to be 12mm; the direction of the jet nozzle 5 is opposite to the rolling direction of the hot-rolled steel plate 3, and the inclination angle is 45°, the jet nozzles 5 are symmetrically distributed up and down.

The high-pressure water tank (not shown in the figure) stores cooling water, and is respectively connected to the plurality of jet nozzles 5 through the regulating valve (not shown in the figure). The water storage tank 1 is arranged at the port of the water jacket 4 (see FIG. 1 ), and is used to receive the cooling water flowing out of the water jacket 4 for recycling.

3 and 4 respectively show a cross-sectional view of FIG. 1 . Fig. 2 is a cross-sectional view of the area where the jet nozzle 5 is not installed, showing the narrow slot channel 2 formed between the water jacket 4 and the hot-rolled steel plate 3, and this position can be regarded as a non-stagnation area. Fig. 3 is a cross-sectional view of the location area where the jet nozzle 5 is installed, the injection area between the water jacket 4 and the hot-rolled steel plate 3, this position can be regarded as the injection stagnation area.

The present invention adopts the jet cooling method in the steel plate narrow slit water jacket channel of the above-mentioned device as follows: a flat rectangular hollow tubular water jacket 4 is set around the hot-rolled steel plate 3 in the cooling zone, and the upper and lower walls of the water jacket 4 are in contact with the hot-rolled steel plate 3. A slit channel 2 is formed between the steel plates 3, and the upper wall and the lower wall of the water jacket 4 are equipped with inclined jet nozzles 5 with openings facing inward, and cooling water is obliquely injected into the slits from the jet nozzles 5 Channel 2, the cooling water is a columnar flow, the injection velocity is 6-10m/s, the pressure is 0.2-0.8MPa, the temperature is 20-80°C, and its injection direction is opposite to the rolling direction of the hot-rolled steel plate 3 and opposite to the hot-rolled steel plate 3. The included angle formed by the surface of the rolled steel plate 3 is 30-60°. The cooling water and the water vapor generated on the surface of the hot rolled steel plate 3 together form a vapor-liquid two-phase flow, and then flow out from the port 2 of the narrow slot channel and flow into the Water storage tank 1 for circulation at the port of water jacket 4 .

The following is an embodiment of the jet cooling method in the steel plate narrow slit water jacket channel of the present invention.

As shown in Figure 1, a section of space is reserved in the cooling area, and a water jacket 4 is placed to surround the hot-rolled steel plate 3. The water jacket 4 is equipped with a plurality of inclined jet nozzles 5 arranged in sections, and the high-pressure water tank 0.4MPa The cooling water is introduced into the jet nozzle 5 through the pipeline, and the jet velocity is 8m/s. The cooling water is obliquely injected into the narrow slot channel 2 from these jet jet nozzles 5, and the regulating valve can adjust the jet water volume, so that the water gradually fills the narrow slot channel 2; The hot-rolled steel plate 3 with a temperature of 850°C conveyed from the constraining roller 6 enters the water jacket 4 at a speed of 1.0-2.0 m/s, and is cooled by cooling water spray and forced convection, forming a high-speed vapor-liquid two-phase flow on the surface. The water vapor in the narrow slit channel 2 keeps annihilating the water vapor produced by boiling, the thickness of the steam film on the surface is not much different, and the cooling is uniform everywhere; at the same time, the jet water continuously breaks through the steam film and impacts the surface of the hot-rolled steel plate 3, so that the average steam The film thickness is reduced, and the heat transfer rate is improved; the cooling water flowing opposite to the rolling direction of the hot-rolled steel plate 3 finally flows out of the water jacket 4, and is discharged into the water storage tank 1, and the hot-rolled steel plate 3 can enter the next cooling unit, and the cooling water is recycled .

The protection scope of the present invention is not limited thereto, and equivalent changes or modifications made according to the embodiments of the present invention and the contents of the description shall all fall within the protection scope of the present invention.

Claims (10)

1. A jet cooling method in a steel plate narrow slit water jacket channel, characterized in that: a flat rectangular hollow tubular water jacket is set around the hot-rolled steel plate in the cooling zone, the upper and lower walls of the water jacket and the hot-rolled steel plate A narrow slit channel is formed between them, and the upper and lower walls of the water jacket are equipped with inclined jet nozzles with openings facing inward. The water vapor generated on the surface jointly forms a vapor-liquid two-phase flow, and then flows out from the port of the narrow slit channel and flows into the circulating water storage tank arranged at the port of the water jacket. 2. The jet cooling method in the steel plate narrow slit water jacket channel according to claim 1, characterized in that: the injection direction of the cooling water is opposite to the rolling direction of the hot-rolled steel plate and formed by the surface of the hot-rolled steel plate The included angle is 30-60°. 3. The jet cooling method in the channel of the steel plate narrow slit water jacket according to claim 1, characterized in that: the cooling water is a columnar flow, and its jet velocity is 6-10m/s. 4. The jet cooling method in the channel of the steel plate narrow slit water jacket according to claim 1, characterized in that: the pressure of the cooling water is 0.2-0.8 MPa, and the temperature is 20-80°C. 5. A jet cooling device in a steel plate narrow slit water jacket passage for implementing the method according to claim 1, characterized in that: said device comprises a high-pressure water tank, a regulating valve, a plurality of jet nozzles, a water jacket and a water storage tank, and said The water jacket is in the shape of a flat rectangular hollow tube and is placed around the hot-rolled steel plate. A narrow channel is formed between the upper and lower walls of the water jacket and the hot-rolled steel plate. The openings of the multiple jet nozzles are installed on the water jacket inclined inward On the upper and lower walls, the high-pressure water tank stores cooling water and connects the multiple jet nozzles through the regulating valve, and the water storage tank is arranged at the port of the water jacket. 6. The jet cooling device in the channel of the steel plate narrow slit water jacket according to claim 5, characterized in that: the water jacket is made of anti-corrosion material. 7. The jet cooling device in the steel plate narrow slit water jacket channel according to claim 6, characterized in that: the anti-corrosion material is stainless steel or a carbon steel plate with an anti-corrosion layer. 8. The jet cooling device in the steel plate narrow slit water jacket channel according to claim 5, characterized in that: the height of the space between the upper wall and the lower wall of the water jacket is not more than 2.5 times the thickness of the hot-rolled steel plate . 9. The jet cooling device in the narrow-slot water jacket channel of the steel plate as claimed in claim 5, characterized in that: the plurality of jet nozzles are arranged in sections on the upper wall and the lower wall of the water jacket and arranged symmetrically up and down, 8-32 groups of jet nozzles are arranged in the width direction of the water jacket, and more than 6 rows of jet nozzles are arranged in the length direction. 10. The jet cooling device in the steel plate narrow slit water jacket channel according to claim 5, characterized in that: the inclination angle of the jet nozzle is 30-60°, and the inner diameter of the nozzle is 6-20mm.

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