Fully air-mist and mist-water mixed cooling device for intensive hot coil continuous heat treatment

Abstract

The present invention discloses a full-gas mist cooling device for intensive continuous heat treatment of hot coils, comprising a plurality of groups of gas mist cooling mechanisms arranged in the cooling zone at the rear position of the soaking furnace, wherein the gas mist cooling mechanisms are distributed on the upper and lower surface sides of the strip and are located between each pair of pressure rollers; each group of the gas mist cooling mechanisms comprises a plurality of gas mist cooling beams, each of which is provided with a nozzle structure; the pressure and flow of the gas mist cooling beams and their nozzles are controlled online by PLC. The present invention also discloses a mist-water hybrid device for intensive continuous heat treatment of hot coils, comprising the full-gas mist cooling device and a pressure water quenching spray box arranged between two adjacent gas mist cooling beams. The present invention provides a full-gas mist and mist-water hybrid cooling device with a high cooling rate to produce intensive continuous heat treatment production of high-strength steel.

Description

Technical Field

[0001] The invention relates to the field of heat treatment technology, and more specifically to a full-gas mist type and mist-water mixed type cooling device for intensive hot coil continuous heat treatment. Background Art

[0002] In order to adapt to the situation of green manufacturing, low-carbon economy and environmental protection policies, construction machinery, dump trucks, heavy trucks, armored trucks, etc. are gradually shifting towards lightweight product structure, upgrading and replacement, and long life. The demand for high-strength products with higher strength, higher wear resistance and longer life has increased significantly, and the field of 2-6mm thick hot-rolled thin-gauge ultra-high-strength steel has shown huge market space.

[0003] Under hot rolling conditions, online quenching to produce giga-level thin-gauge ultra-high-strength steel requires a higher cooling rate and a lower coiling temperature. Currently, the medium and low temperature coiling temperature is not controlled, the strip shape is difficult to control, and the uniformity of organization and performance is poor, which cannot meet the market demand for high-performance and high-plate shape high-strength steel. At the same time, the high hot rolling speed of thin gauges will have an adverse effect on the stability of the plate and the safety of the coiling equipment. Therefore, it is not suitable to produce thin gauge ultra-high-strength steel by hot rolling online quenching.

[0004] At present, thin-gauge ultra-high-strength steel is generally produced by offline heat treatment at home and abroad, that is, after the hot coil is cut and cut, it is heated, quenched, tempered and other heat treatments are carried out in the form of a single steel plate. The quenching machine generally adopts water-cooled quenching, equipped with high-pressure slit injection and pressure injection, and optimizes the quenching plate shape by adjusting the upper and lower water ratio, steel plate speed and frame height. The maximum steel plate speed can reach 75m / min, and there is basically no need to consider the performance problems caused by the return temperature during the quenching process to form tempered martensite. This production method is mature in technology and stable in quality, but it has large investment, large land occupation, long process, and low production efficiency and high production cost in single-sheet form.

[0005] The intensive hot coil continuous heat treatment technology can significantly reduce the unit's land occupation, improve production efficiency, reduce energy consumption, and reduce environmental pollution. It is a green production technology. However, the intensive production line layout makes the hot coil run slowly, generally less than 10m / min, and the speed cannot be adjusted. It is easy to return to temperature during the continuous quenching process to form tempered martensite, causing performance problems. In addition, the water quenching cooling rate of thin-gauge steel coils is too high and the uniformity is poor. It is not only easy to crack, but also difficult to control the plate shape, which brings great difficulties to the selection of quenching equipment and process layout design.

[0006] In the existing patent applications, such as Chinese patent CN102492824A, a cooling method for continuous heat treatment of high-strength steel is disclosed, which adopts a cooling method of jet slow cooling + aerosol cooling + slit nozzle water cooling, mainly for the continuous annealing treatment quenching of cold-rolled steel coils with a thickness of less than 2mm, a fast strip speed, and a long cooling line layout. For the continuous quenching of 2-6mm thick low-speed hot coils, the aerosol cooling rate is insufficient (aerosol cooling rate 10-15℃ / s, water spray cooling 40℃ / s), and it is easy to return to temperature and cause performance problems, while water-cooled quenching is prone to quenching cracks, and the slit nozzle flow adjustment range is small, which cannot meet the needs of flexible quenching and multi-path quenching.

[0007] For example, Chinese patent CN102424902A discloses a continuous heat treatment method for high-strength steel strips or plates, describing the heat treatment process of hot-rolled steel coils or steel plates from heating, quenching to tempering. The quenching process uses an air-water mixed cooling device, and its nozzle can achieve adjustable control from air-water mixing to complete water spraying. The patent does not further describe the details, parameters and layout design of the nozzle device. From the implementation column, for 3mm strip steel, its gas mist cooling can only reach a cooling rate of 10℃ / s, which cannot reach the process cooling rate required for high-strength steel. In addition, the nozzle must be adjustable from gas mist to water spraying, and it is difficult to ensure cooling uniformity.

[0008] For example, Chinese patent CN101935750A discloses a production process for a high-performance steel plate heat treatment unit, but only mentions the use of an aerosol cooling section, without describing any details such as the layout and parameters of the aerosol cooling section, nor does it explain the cooling rate that can be achieved by the aerosol section. The cooling rate is controlled only by adjusting the "on / off" position of each row of aerosol nozzles. There is no "side, middle, and side" control in the horizontal direction (strip width direction), and there is no refined control over the pressure and flow of air and water.

[0009] For example, Chinese patent CN1413779A discloses an online cooling system for medium and thick plates below the medium temperature zone. However, its cooling rate is only 1-5°C / s and is only used under working conditions below 550°C, which cannot meet the demand for producing high-strength steel.

[0010] For example, Chinese patent CN106350640A discloses a method for continuous quenching of cold-rolled strip steel, which only mentions the use of mist cooling from a process perspective, without describing any details such as the layout and parameters of the mist cooling section.

[0011] For example, Chinese patent CN109022734A discloses an online heat treatment device and heat treatment method for strip steel, which uses "ultra-fast cooling section + layer cooling section" and does not involve mist cooling.

[0012] For example, Chinese patent CN102327831A discloses an air-mist nozzle for cooling plate and strip materials. The invention focuses on combining the air-mist nozzle with the subsequent air and water nozzles to form an integrated non-standard part. However, it is not as practical as using an air-mist nozzle with a standard structure. The installation interface of the nozzle with a standard structure is the same, which can increase interchangeability. More importantly, the standard structure is convenient for flexibly replacing different air-mist nozzles according to different cooling requirements, which can flexibly meet different process requirements.

[0013] For example, Chinese patent CN102424902A discloses an off-line heat treatment mist cooling system for thin-gauge medium and thick plates. The invention describes a non-standard slit nozzle for mist cooling, but does not specify the actual cooling rate. Each group of cooling beams has a slit nozzle on the upper and lower sides, and there is no "edge-in-edge" adjustment function, making it difficult to control the gap accuracy and cooling rate in the width direction of the plate strip; and the gap width is fixed, making it difficult to adjust the cooling rate according to process requirements.

[0014] From the above-mentioned patents and actual field applications, pressure water quenching has the highest cooling rate and is suitable for thick plates or thick tubes, but its cooling rate is too fast for thin strip quenching, which is easy to cause quenching cracks, and it is difficult to ensure uniformity, so it is difficult to control the plate shape. Although the mist cooling technology commonly used in cold rolling continuous annealing has good cooling uniformity, its cooling rate is low and is only suitable for extremely thin specifications below 2mm, and cannot meet the high cooling rate requirements required for quenching hot coils with a thickness of 2 to 10mm.

[0015] At present, there is no mature quenching and cooling device and control method for continuous heat treatment of hot coils, especially for intensive continuous heat treatment of 2-10mm strip at low speed.

[0016] After careful analysis, the characteristics of aerosol cooling are: although its cooling rate is slightly lower than that of water quenching, its cooling uniformity is very good, and the cooling rate can be accurately controlled by adjusting the pressure and flow rate online. If the mechanism of aerosol cooling is carefully analyzed and the aerosol cooling device is deeply optimized, its cooling capacity should be greatly improved, thereby meeting the needs of rapid and uniform cooling required by continuous heat treatment of thin-gauge hot steel coils. Summary of the invention

[0017] In view of the above-mentioned defects existing in the prior art, the purpose of the present invention is to provide a full air mist and mist water mixed cooling device for intensive continuous heat treatment of hot coils, and to provide a full air mist and mist water mixed cooling device with a high cooling rate, so as to realize the intensive continuous heat treatment production of high-strength steel.

[0018] To achieve the above object, the present invention adopts the following technical solution:

[0019] On the one hand, a full gas mist cooling device for intensive hot coil continuous heat treatment includes multiple groups of gas mist cooling mechanisms arranged in the cooling zone at the rear position of the soaking furnace, wherein the gas mist cooling mechanisms are distributed on the upper and lower surface sides of the strip and are located between each pair of pressure rollers;

[0020] Each group of the aerosol cooling mechanism comprises a plurality of aerosol cooling beams, and each of the aerosol cooling beams is provided with a nozzle assembly;

[0021] The pressure and flow rate of the aerosol cooling beam and the nozzle assembly are controlled online by PLC.

[0022] Preferably, the nozzle assembly includes a water inlet pipe, a compressed air inlet pipe, and multiple exhaust mist nozzles respectively connected to the water inlet pipe and the compressed air inlet pipe;

[0023] The fan-shaped jets of the aerosol nozzles are all arranged toward the surface of the steel strip.

[0024] Preferably, the aerosol nozzle is an internal mixing nozzle or an external mixing nozzle.

[0025] Preferably, the aerosol nozzle is a fan-shaped nozzle, and the fan-shaped jet of the aerosol nozzle and / or the deflection angle of the aerosol nozzle in the width direction of the strip is 15° to 60°.

[0026] Preferably, the water inlet pipe is provided with two or more rows of an even number of the aerosol nozzles.

[0027] Preferably, a water mist baffle is further provided between the cooling zone and the soaking furnace, and the water mist baffle is distributed on the upper and lower surface sides of the steel strip.

[0028] Preferably, the fan angle β of the aerosol nozzle is 45° to 90°; the height difference H between the aerosol nozzle and the surface of the strip is 80 to 150 mm; the fan flow width B of the fan flow hitting the steel plate can be calculated from β and H; the exhaust mist nozzles need to be deflected by a certain angle δ to avoid mutual interference of the fan flows; the overlap OV of the fan jets between the exhaust mist nozzles is a key parameter to ensure transverse (plate width direction) cooling uniformity; the transverse spacing D of the aerosol nozzles should ensure that the OV value is 1 / 3 to 1 / 4 of B; the longitudinal spacing L value (along the direction of strip travel) of each exhaust mist nozzle has a great influence on the cooling rate, and the L value should be minimized to avoid the strip from warming up between the gaps between the two groups of aerosol nozzles, affecting the cooling rate.

[0029] On the other hand, a mist-water hybrid cooling device for intensive hot coil continuous heat treatment comprises the full aerosol cooling device and a pressure water quenching spray box arranged between two adjacent aerosol cooling beams;

[0030] The pressure water quenching spray box cools the steel strip from the upper and lower sides;

[0031] The pressure water quenching spray box is provided with multiple drainage nozzles on the surface side facing the strip.

[0032] Preferably, the pressure water quenching spray box is a direct spray box or an oblique spray box.

[0033] Preferably, the direct jet of the water nozzle on the direct spray box or the oblique jet of the water nozzle on the oblique spray box is directed toward the surface of the steel strip;

[0034] The cooling rate of the mist water hybrid cooling device is ≥60℃ / s.

[0035] The present invention provides a full-gas mist and mist-water mixed cooling device for intensive hot coil continuous heat treatment, which can realize the quenching and cooling production of 2 to 12 mm thick in the intensive heat treatment production line, apply flexible quenching and multi-path quenching to expand steel specifications and improve product performance, achieve good quenched plate shape through plate shape control technology, and realize fully automatic quenching cooling and precise control through model control technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of the aerosol fan-shaped nozzle in the full aerosol cooling device of the present invention when the deflection angle is 15°;

[0037] Figure 2 It is a schematic diagram of the aerosol fan-shaped nozzle in the full aerosol cooling device of the present invention when the deflection angle is 40°;

[0038] Figure 3 Schematic diagram of the nozzle assembly in the full gas mist cooling device of the present invention, wherein (a) is provided with two gas mist nozzles on the water inlet pipe, and (b) is provided with four gas mist nozzles on the water inlet pipe;

[0039] Figure 4 Schematic diagram of the deflection angle of the aerosol fan-shaped nozzle in the full aerosol cooling device of the present invention, wherein the arrow in the figure indicates the traveling direction of the strip steel;

[0040] Figure 5 It is a schematic diagram of a pressure water quenching spray box in the mist-water hybrid cooling device of the present invention being an inclined spray box;

[0041] Figure 6 It is a schematic diagram of a pressure water quenching spray box in the mist-water hybrid cooling device of the present invention being a direct spray box;

[0042] Figure 7 It is a parameter schematic diagram of the arrangement of the aerosol nozzles in the full aerosol cooling device and the mist-water mixed cooling device of the present invention. DETAILED DESCRIPTION

[0043] In order to better understand the above technical solution of the present invention, the technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0044] Combination Figure 1 and Figure 2 As shown, for steel with a thickness of 2 to 7 mm and good thermal conductivity, a full-gas mist cooling device for intensive hot coil continuous heat treatment provided by the present invention is used, including multiple groups of gas mist cooling mechanisms arranged in the cooling zone 2 at the rear position of the heating furnace 1, and the gas mist cooling mechanisms are distributed on the upper and lower surface sides of the strip 3 and are located between each pair of pressing rollers 4.

[0045] Each group of aerosol cooling mechanisms comprises a plurality of aerosol cooling beams 5 , each aerosol cooling beam 5 is provided with a nozzle assembly, and the pressure and flow of the aerosol cooling beam 5 and the nozzle assembly are controlled online by PLC.

[0046] Place the mist cooling mechanism as close to the soaking furnace 1 as possible to reduce air cooling after the furnace is taken out.

[0047] A water mist baffle 6 is also provided between the soaking furnace 1 and the cooling zone 2, and the water mist baffle 6 is distributed on the upper and lower surface sides of the strip steel 3 to prevent the drifting water mist from cooling the strip steel 3 in advance, causing the cooling temperature to be low and affecting the mechanical properties of the strip steel 3.

[0048] Each mist cooling beam 5 is arranged close to the pressure roller 4 to reduce the air cooling section.

[0049] Multiple mist cooling beams 5 are arranged between every two pairs of pressure rollers 4. Figure 3 The 4 groups × 4 groups × 4 groups shown can also be arranged in other forms, such as 4 groups × 3 groups × 2 groups, according to the temperature drop process requirements of different steel grades.

[0050] Each mist cooling beam 5 is divided into "edge, middle, edge" sections along the width direction (transverse direction) of the steel strip 3. The corresponding end pressure and flow of the water inlet pipe and compressed air pipe can be controlled online by PLC to adjust the "edge-middle-edge" cooling rate of the steel strip 3 online according to process requirements.

[0051] Combination Figure 3 As shown, the nozzle assembly includes a water inlet pipe 7 , a compressed air pipe 9 , and a plurality of exhaust mist nozzles 8 connected to the water inlet pipe 7 and the compressed air pipe 9 .

[0052] The jets 801 of the aerosol nozzles 8 are all directed toward the surface of the steel strip 3 .

[0053] In order to arrange the aerosol nozzles 8 as densely as possible along the traveling direction of the steel strip 3, the present invention utilizes the principle that the area is in a square relationship with the diameter, and appropriately increases the diameter of the water inlet pipe 7 and the diameter of the compressed air pipe 9 to realize the structure of "one beam with multiple rows of nozzles" in a smaller space, and saves space by arranging the water inlet pipe 7 and the compressed air pipe 9 up and down to shorten the distance occupied by each aerosol cooling beam 5 in the traveling direction (longitudinal direction) of the steel strip 3 as much as possible, and increases the number of aerosol nozzles 8 per unit longitudinal length, such as Figure 3 As shown, (a) is a beam 2 exhaust mist nozzle 8, and (b) is a beam 4 exhaust mist nozzle 8.

[0054] The aerosol nozzle 8 can be an internal mixing nozzle or an external mixing nozzle. Both types of nozzles have their own advantages. The atomized particles of the internal mixing nozzle are finer; when adjusting the external mixing nozzle, the water pressure and the air pressure are independent of each other and are not affected by the changes of each other, which is more convenient for PLC control.

[0055] Combination Figure 4 As shown, the deflection angle δ between the jet 801 of the aerosol nozzle 8 and the width direction of the strip is 15° to 60° (the arrow in the figure is the direction of the strip travel), and the aerosol nozzles 8 in the same row are deflected by a certain deflection angle δ to avoid mutual interference of the fan flows. Figure 1 When the deflection angle δ of the jet 801 of the gas mist nozzle 8 and the width direction of the strip is 15°, if necessary, increasing the deflection angle δ can make the jets 801 of the front and rear exhaust mist nozzles 8 arranged nearly continuously. Figure 1 When the deflection angle δ between the jet 801 of the aerosol nozzle 8 and the water inlet pipe 7 is 45°, the proportion of the "no jet impact section" can be reduced, the temperature reversal phenomenon of the steel strip 3 can be effectively avoided, and the aerosol cooling capacity can be increased.

[0056] Using a full aerosol cooling device, the aerosol cooling rate of 6mm thick wear-resistant steel from 800 to 200℃ is ≥60℃ / s.

[0057] Combination Figure 5 and Figure 6 As shown, for steel materials such as wear-resistant steel with a thickness of 4 to 12 mm and low thermal conductivity, a mist-water hybrid cooling device for intensive hot coil continuous heat treatment provided by the present invention is used, including the full aerosol cooling device of the present invention and a pressure water quenching spray box 10 arranged between two adjacent aerosol cooling beams 5.

[0058] The pressure water quenching spray box 10 is provided with a plurality of water discharge nozzles 11 on the surface side facing the steel strip 3 .

[0059] Combining the advantages of uniformity of the aerosol of the full aerosol cooling device and strong water quenching cooling capacity of the pressure water quenching spray box 10, the cooling methods such as "pure aerosol" or "aerosol + water quenching" can be flexibly selected: when the thickness of the strip steel 3 is thinner, the full aerosol cooling method is used; when the thickness of the strip steel 3 is thicker, the aerosol + water quenching cooling method is used.

[0060] The pressure water quenching spray box 10 can adopt a direct spray box (on which multiple rows of columnar water nozzles 11 are densely arranged) or an inclined spray box (on which multiple rows of columnar water nozzles 11 are densely arranged). The direct spray box and the inclined spray box are also internally segmented, which can realize independent control of the water pressure and flow rate of the "edge, middle, and edge" in the width direction of the strip 3.

[0061] Combination Figure 7 As shown, the fan angle β of the aerosol nozzle in the full aerosol cooling device and the mist-water mixed cooling device of the present invention is 45°~90°; the height difference H between the aerosol nozzle and the surface of the strip is 80~150mm; the fan flow width B of the fan flow hitting the steel plate can be calculated from β and H; the exhaust aerosol nozzles need to be deflected by a certain angle δ to avoid mutual interference of the fan flows; the overlap amount OV of the fan jets between the exhaust aerosol nozzles is a key parameter to ensure the uniformity of cooling in the horizontal direction (plate width direction); the lateral spacing D of the aerosol nozzles should ensure that the OV value is 1 / 3~1 / 4 of B; the longitudinal spacing L value (along the traveling direction of the strip) of each exhaust aerosol nozzle has a great influence on the cooling rate, and the L value should be reduced as much as possible to avoid the strip from returning to temperature between the gaps between the two groups of aerosol nozzles, thereby affecting the cooling rate.

[0062] The advantage of the oblique spray box is that the oblique direction of the water flow is consistent with the traveling direction of the strip 3, the water flow on the upper surface of the strip 3 will not splash back to the front of the press roller, and will not flow back to the position of the soaking furnace at all, and the manufacturing accuracy and pressure control requirements of the press roller 4 are not high. The advantage of the direct spray box is that the spray box body can be arranged between the gaps of each group of aerosol cooling beams 5. It is only necessary to embed the water nozzles 11 between the aerosol cooling beams 5, and the distance between each group of aerosol cooling beams 5 can be shortened as much as possible, which makes it possible to densely arrange the aerosol beams and greatly improve the cooling capacity in the full aerosol mode.

[0063] Example 1

[0064] Produce 2-7mm thick steel with good thermal conductivity

[0065] Use Figure 1 or Figure 2 The full mist cooling device shown, or the Figure 5 or Figure 6 In the mist-water hybrid cooling device shown, the pressure water quenching spray box 10 remains closed and cooling is performed by full mist method, which not only ensures a cooling rate of ≥ 60°C / s, but also obtains the optimal plate shape.

[0066] Example 2

[0067] Produce 4-12mm thick steel with good thermal conductivity

[0068] use Figure 5 or Figure 6 In the mist-water mixed cooling device shown, the pressure water quenching spray box 10 is partially or fully opened according to the process requirements, and cooling is performed by mist-water mixed method, which not only ensures that the cooling rate is ≥ 60°C / s, but also obtains the optimal plate shape.

[0069] From the above, the full gas mist and mist water mixed cooling device for intensive hot coil continuous heat treatment of the present invention is to arrange a set of gas mist or mist water mixed quenching cooling device optimized for the above parameters between the heating device and the drying device for intensive thin-gauge hot coil continuous heat treatment. The heated hot-rolled strip enters the quenching cooling device area through the conveyor roller, and is subjected to gas mist cooling or gas mist & water mixed cooling quenching treatment. The steel plate reaches a specific final cooling temperature according to a predetermined cooling rate curve while ensuring the plate shape and uniform cooling, and is then sent to the subsequent process by the roller after drying.

[0070] Those skilled in the art should recognize that the above embodiments are only used to illustrate the present invention, and are not intended to limit the present invention. As long as they are within the spirit of the present invention, any changes or modifications to the above embodiments will fall within the scope of the claims of the present invention.

Claims

1. A mist-water mixed cooling device for intensive hot coil continuous heat treatment, characterized in that: It includes a full aerosol cooling device and a pressure water quenching spray box located between two adjacent aerosol cooling beams. The full gas mist cooling device comprises a plurality of gas mist cooling mechanisms arranged in the cooling zone at the rear position of the soaking furnace, wherein the gas mist cooling mechanisms are distributed on the upper and lower surface sides of the strip and are located between each pair of pressure rollers; Each group of the aerosol cooling mechanism comprises a plurality of aerosol cooling beams, and each of the aerosol cooling beams is provided with a nozzle assembly; The pressure and flow rate of the aerosol cooling beam and the nozzle assembly are controlled online by PLC. The nozzle assembly comprises a water inlet pipe, a compressed air inlet pipe, and a plurality of exhaust mist nozzles respectively connected to the water inlet pipe and the compressed air inlet pipe; The fan-shaped jets of the aerosol nozzles are all set toward the surface of the strip steel. The aerosol nozzle is a fan-shaped nozzle, and the fan-shaped jet of the aerosol nozzle and / or the deflection angle of the aerosol nozzle in the width direction of the strip steel is 15° to 60°; The fan angle β of the aerosol nozzle is 45° to 90°; The height difference H between the aerosol nozzle and the surface of the steel strip is 80 to 150 mm; There is a deflection angle δ between the aerosol nozzles in the same row, and the deflection angle δ is 15° to 60°. The pressure water quenching spray box is provided with multiple drainage nozzles on the side facing the surface of the strip steel. The pressure water quenching spray box is a direct spray box or an inclined spray box. The straight jet of the water nozzle on the straight spray box or the oblique jet of the water nozzle on the oblique spray box is directed toward the surface of the steel strip; The cooling rate of the mist water hybrid cooling device is ≥60℃ / s.

2. The mist-water hybrid cooling device for intensive hot coil continuous heat treatment according to claim 1 is characterized in that: The aerosol nozzle is an internal mixing nozzle or an external mixing nozzle.

3. The mist-water hybrid cooling device for intensive hot coil continuous heat treatment according to claim 1 is characterized in that: A water mist baffle is also provided between the cooling zone and the soaking furnace, and the water mist baffle is distributed on the upper and lower surface sides of the steel strip.

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