JP4537875B2 - Steel strip cooling device - Google Patents

Description

  The present invention relates to an apparatus for cooling a continuously running steel strip in, for example, a continuous annealing equipment for a steel strip, a continuous hot dip galvanizing equipment, a color coating line, a stainless acid pickling annealing line, and the like.

  As is well known, continuous annealing furnace equipment includes a process of continuously heating, soaking, and cooling a steel strip and, if necessary, overaging. By the way, in order to obtain the desired properties of the steel strip, it is important to uniformly and rapidly cool the steel strip in addition to the heating temperature and the soaking time. Various cooling media are currently used as a method for cooling the steel strip, and the cooling speed of the steel strip varies depending on the selection of the refrigerant.

  Among these, when water is used as a refrigerant, a considerably high cooling rate can be obtained and cooling to a super-quenching region is possible, but the biggest difficulty is that the shape change of the steel strip called a cooling buckle occurs due to quenching strain. It is. In addition, an oxide film is formed on the surface of the steel strip due to contact with water, and a separate facility is required to remove it, which is not economically advantageous.

  In order to solve this problem, there is a roll cooling method in which water or other cooling medium is passed through the inside of the roll, and a steel strip is brought into contact with the cooled roll surface for cooling.

  However, this method has the following problems. That is, not all the steel strips passing through the continuous annealing furnace maintain flatness. Therefore, when contacting the cooling roll, there is a case where it is locally not in contact, and this non-contact causes cooling in the width direction of the steel strip, which causes deformation of the steel strip. Therefore, a means for flattening the steel strip is required before contact with the cooling roll, which increases the equipment cost.

  As another cooling means, a cooling method using a gas as a refrigerant has been put into practical use, and many achievements have been given. This method has a slower cooling rate than the above-described water cooling and roll cooling, but relatively uniform cooling in the width direction of the steel strip is possible. In order to increase the cooling rate, which is the biggest difficulty of this gas cooling, the tip of the nozzle that injects the gas is brought close to the steel strip as much as possible to increase the heat transfer rate, and the concentration of hydrogen gas as the cooling medium. The thing which employ | adopted what raised the heat transfer rate by raising is disclosed.

  As a technique for increasing the heat transfer coefficient by bringing the tip of a nozzle to be sprayed close to a steel strip, there is a technique disclosed in Patent Document 1. This technology enables efficient cooling by reducing the distance between the tip of the nozzle and the steel strip. Specifically, the length of the protruding nozzle protruding from the surface of the cooling gas chamber provided in the cooling gas chamber is set to 100 mm-Z or more, and a portion where the gas injected from the protruding nozzle hits the steel strip and escapes to the back portion is provided. Yes. Thus, it is disclosed that the injected gas is reduced from staying on the surface of the steel strip and the cooling uniformity in the width direction of the steel strip is improved. Z indicates the distance between the tip of the protruding nozzle and the steel strip.

Also, experiments are conducted to derive the optimum point of the heat transfer coefficient by changing the protrusion height of the nozzle from 50 mm-Z to 200 mm-Z. As a cooling device used in the cooling zone of the continuous annealing furnace, a cooling device having an efficient cooling capacity is proposed from this experiment. The cooling device, the heat transfer coefficient was usually 100kcal / ^{m 2} h ℃ has become possible to raise up 400kcal / ^{m 2} h ℃.

However, further improvement in the cooling rate has been desired, and there is a limit to existing cooling devices that circulate atmospheric gas of about N ₂ : 95% + H ₂ : 5% as a normal cooling medium. In order to solve this problem, it has been considered to use hydrogen gas as a cooling medium. Although it has been known for a long time that the cooling capacity is improved by using hydrogen gas, it has not been applied to actual machines due to the danger of hydrogen gas.

  Patent Document 2 discloses a technique for rapidly cooling by increasing the hydrogen gas concentration. In this rapid cooling zone, the hydrogen concentration of the cooling gas is set to 30% to 60% and the spraying speed is set to 100 m / sec to 150 m / sec to spray the steel strip for cooling. In this way, specific techniques for employing hydrogen gas have been developed and are being implemented.

Usually, it is necessary to increase the H ₂ concentration from cooling with the atmospheric gas mainly composed of N ₂ gas and to set the discharge flow rate from the nozzle to 100 m / sec to 150 m / sec, so the amount of gas blown to the steel strip Will also be large. In addition, a pressure for ejecting gas from the nozzle at a discharge flow rate of 100 m / second to 150 m / second is also required. Generally, these cooling devices employ a circulation type cooling device in which a cooling medium sprayed on a steel strip is circulated through a duct and sprayed again. In this circulation type cooling device, the cooling medium sprayed on the steel strip is discharged into the furnace and sucked by the circulation blower from the suction duct provided in the furnace body. In front of the circulation blower, a heat exchanger that cools the cooling medium whose temperature has been increased by spraying to the steel strip to the spray temperature is installed, and the steel strip is cooled while circulating by these devices. .

The required pressure in these circulation devices is the highest required for jetting from the nozzle, and it is desired to suppress the pressure loss of this nozzle part as much as possible, further improve the heat transfer coefficient and realize uniform cooling. It was.
Japanese Patent Publication No. 2-16375 JP-A-9-235626

  Therefore, the present invention solves the problems of the prior art as described above, increases the gas ejection speed from the nozzle in order to obtain a high cooling rate, reduces the resistance coefficient of the nozzle, and makes the gas circulation facility compact. It is an object of the present invention to provide a steel strip cooling device capable of increasing the heat transfer coefficient of the refrigerant ejected from the nozzle and performing uniform cooling.

The present invention provides a cooling device for a steel strip in which a projecting nozzle is arranged on the surface of a cooling box, and a steel strip is cooled by jetting a refrigerant from the projecting nozzle to cool the steel strip. A plurality of protruding nozzles held at 100 mm are protruded from the surface of the cooling box, and A / a of the protruding nozzles is 2 ≦ A / a ≦ 9 (A: opening sectional area of nozzle base, a: opening sectional area of nozzle tip) ), The distance L2 from the surface of the cooling box to the nozzle tip of the protruding nozzle is 150 to 200 mm, and the flatness a1 / a2 of the opening cross section of the nozzle tip is 1 <a1 / a2 <9 (a1: nozzle tip) The protruding nozzle for improving the heat transfer coefficient directly under the nozzle, which is defined as a long side of the opening cross section, a2: a short side of the opening cross section of the nozzle tip , is disposed in the cooling box .

  This flat tip protruding nozzle can also match all the long sides of the nozzle tip opening cross section, but with the protruding nozzle row group in the width direction of the steel strip and the protruding nozzle row group adjacent to this, It is desirable that the directivity in the long-side direction of the nozzle tip opening section is different.

  Further, the protruding nozzle can be fixed to the mounting hole provided in the cooling box with the nozzle base portion by pipe expansion joining.

  The protruding nozzle is attached so that the nozzle base does not protrude from the inner surface of the cooling box, and the end of the nozzle base and the inner surface of the mounting hole are joined by welding, It can also be constructed so as not to protrude from the inner surface of the cooling box.

Furthermore, as the refrigerant, H ₂ gas or a mixed gas of H ₂ gas and N ₂ gas or other inert gas can be used.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to raise the heat transfer rate in cooling and to cool a steel strip uniformly. Even if the gas ejection speed from the nozzle is increased in order to obtain a high cooling rate, the resistance coefficient of the nozzle can be reduced, and the gas circulation facility can be made compact.

  Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings. FIG. 1 is a side sectional view of a cooling device for a continuous annealing facility to which the present invention is applied, FIG. 2 is a view taken along the line AA of FIG. 1, FIG. 3 is a detailed view of a conical protruding nozzle, and FIG. FIG. 5 is a graph showing the resistance coefficient of the protruding nozzle, FIG. 6 is a detailed view of the conical protruding nozzle having a flat nozzle tip, and FIG. 7 is a conical protruding nozzle. FIG. 8 is a diagram showing the heat flow rate on the steel strip immediately below the nozzles of various shapes, FIG. 9 is a diagram showing the relationship between the flatness of the nozzle tip and the resistance coefficient, and FIG. 10 is the nozzle tip having a flat shape. FIG. 11 is a diagram showing an arrangement example of a certain conical protruding nozzle, FIG. 11 is a detailed view of a conical + tip cylindrical protruding nozzle, FIG. 12 is a schematic diagram in which the cooling device of the present invention is applied to a continuous coating line, and FIG. FIG. 14 shows a cooling device for cooling a steel strip after plating in a continuous hot dip galvanizing facility. Schematic diagram according to the present invention, FIG 15 is a schematic diagram of applying the cooling system of the present invention to the cooling zone of the stainless continuous annealing pickling facility.

  In FIG. 1, a pair of cooling devices 2 that are installed between an upper roll 9 and a lower roll 11 for conveying a steel strip 12 and jet gas are provided between the upper and lower rolls so as to face the surface of the steel strip 12. A plurality of cooling devices 2 are arranged along the flow of the steel strip 12. And between the upper and lower sides of this cooling device 2, the press roll 10 which prevents the flapping of a steel strip is arrange | positioned so that the steel strip 12 may be clamped.

FIG. 2 is an AA arrow view of FIG. 1, and the gas blown to the steel strip 12 by the cooling device 2 is reused as a cooling gas through the circulation system. In the present invention, the refrigerant containing the cooling gas is a mixed gas composed of H ₂ gas, N ₂ gas and other inert gas, and the H ₂ concentration is 0 to 100%, and the rest is N ₂ or other inert gas. It is preferable that That is, the blown gas is sucked from a gas suction port provided in the furnace body 1, and further cooled in the furnace body 1 through the suction side duct 5, the heat exchanger 6, the circulation blower 7 and the discharge side duct 8. By the circulation system connected to the box 3, it is ejected again from the protruding nozzle 4 provided on the steel strip 12 surface side of the cooling box 3 toward the steel strip 12. Thus, the gas in the furnace body 1 sprayed on the steel strip 12 is circulated and used.

  The cooling device 2 includes a cooling box 3 and a protruding nozzle 4 provided on the surface of the steel strip 12 of the cooling box 3. As this protruding nozzle 4, the ratio (A / a) of the opening cross-sectional area A of the nozzle base (cooling box 3 side) and the opening cross-sectional area a of the nozzle tip (steel strip 12 side) is 2.0 to 9.0. A nozzle is selected and arranged. The distance L1 from the nozzle tip of the protruding nozzle 4 to the surface of the steel strip 12 is set in the range of 30 to 100 mm, and the distance L2 from the surface of the cooling box 3 to the nozzle tip of the protruding nozzle 4 is set in the range of 150 to 200 mm. Further, the protruding nozzles 4 are arranged so that the total opening area of the nozzle tips of the protruding nozzles 4 is 2 to 4% of the surface area of the cooling box 3.

  FIG. 3 shows a conical protruding nozzle 4, where D is the inner diameter of the nozzle base (here, the nozzle base refers to the side attached to the cooling box 3), D 0 is the outer diameter of the nozzle base, and d is The inner diameter of the nozzle tip, L2 is the total nozzle length, DN is the nozzle base, and the nozzle outer diameter is in the range of (nozzle total length L2)-(10 mm ± 3 mm), in other words, the tip side is 10 mm ± 3 mm from the nozzle base. Pointing. Since the protruding nozzle 4 has a conical shape, it was manufactured by winding a SUS (stainless steel) plate. In addition to plate winding, the protruding nozzle can be manufactured by drawing steel pipe, cutting out, or casting. Experiments were conducted with various nozzles with A / a having a total nozzle length L2 of 200 mm.

  FIG. 4 shows a situation when the protruding nozzle 4 of the present invention is attached to the cooling box 3, and an attachment hole having a DN diameter is provided on the surface of the cooling box 3 on the steel strip 12 side. The number of mounting holes is provided so that the total opening area (total) at the nozzle tip is 2 to 4% of the surface area of the cooling box 3.

  Specifically, first, a DN-diameter mounting hole is formed in the surface of the cooling box 3. A nozzle base having an outer diameter D0 is inserted into the mounting hole, and driven into the cooling box 3 with a punch (not shown) as shown in FIG. When the protruding nozzle 4 is driven, it is driven so that the nozzle base does not protrude on the inner surface of the cooling box 3 as shown in FIG. In FIG. 4, the nozzle base is driven into the cooling box 3 so as to be charged leaving 10 mm from the inner surface. Then, the base side nozzle inner diameter D is expanded by a tube expander (not shown) charged from the nozzle base side of the driven nozzle 4 that has been driven in, and is crimped to the mounting hole DN diameter provided in the cooling box 3. Furthermore, the end of the nozzle base and the inner surface of the mounting hole are joined by welding. At this time, as shown in FIG. 4, the weld overlay W is constructed so as not to protrude from the inner surface of the cooling box 3. As described above, the mounting accuracy of the protruding nozzle 4 is improved by performing the pipe expansion joining with the pipe expanding machine, as compared with the case where it is conventionally attached by welding.

  The reason why the position of the DN diameter is limited as described above is that if it is equal to or higher than the upper limit (exceeding 10 mm + 3 mm), it is difficult to insert into the cooling box.

  As described above, in FIG. 4, in order to reduce the resistance coefficient of the protruding nozzle 4, the nozzle base portion is embedded leaving 10 mm from the inner surface of the cooling box 3. However, if the resistance coefficient is reduced, the nozzle base is matched with the inner surface of the cooling box 3. It is also possible. Further, in FIG. 4, welding is performed by expanding the pipe, but welding may be performed by attaching by means other than the expanded pipe joining.

  The pressure loss was calculated | required with the experimental apparatus about the protrusion nozzle 4 manufactured in the above way, and each resistance coefficient was computed. The result is shown in FIG. It was found that the resistance coefficient is small when A / a = 1.0, that is, A / a = 2.0 to 9.0 compared with the conventional straight nozzle, and the vicinity of 4.0 is the smallest. Thus, the resistance coefficient of the nozzle is about 30% smaller than that of the conventional straight nozzle.

Moreover, in this invention, a nozzle front-end | tip part is made into a flat shape, and the width direction ejection width | variety of a steel strip is expanded. FIG. 6 shows an example of a protruding nozzle having a flat tip (hereinafter referred to as “flat nozzle”) .

  When the nozzle tip is flattened, the reduction in the heat transfer coefficient directly under the nozzle generated by the conical nozzle is improved. FIG. 8 shows a flat nozzle (A / a = 6, a1 / a2 = 6, see FIG. 6) of the present invention, a conventional cylindrical nozzle (straight nozzle) having the same opening cross-sectional area at the nozzle base and tip, and a cone. The heat flow rate of the steel strip below each nozzle of the nozzle (A / a = 6, see FIG. 7) is shown. In the conical nozzle, it can be confirmed that the heat flow rate on the steel plate immediately below the center of the nozzle is reduced.

  On the other hand, in the flat nozzle of the present invention, the average transmission coefficient was 7% larger than that of the conical nozzle. This is thought to be because the cylindrical shape is conical, and the flow stagnant region immediately below the center of the nozzle is made easier to flow by flattening the nozzle tip. As the flatness ratio a1 / a2 of the nozzle tip portion (a1: long side of the opening cross section of the nozzle tip portion, a2: short side of the opening cross section of the nozzle tip portion) becomes larger than 1, the average heat transfer coefficient is improved.

  However, as shown in FIG. 9, when the flatness ratio a1 / a2 of the nozzle tip is 9 or more, the pipe resistance increases, and the effect of changing the nozzle shape from the cylindrical shape to the conical shape decreases. For this reason, in the flat nozzle of the present invention, the flatness ratio a1 / a2 of the nozzle tip is 1 <a1 / a2 <9. The cylindrical nozzle has the least decrease in the heat flow rate on the steel plate directly under the nozzle. However, the cylindrical nozzle has a high resistance coefficient as described above.

  As shown in FIG. 10, the flat nozzles are arranged with respect to the surface of the cooling box, as shown in FIG. 10, with the protruding nozzle row group 4 a in the width direction of the steel strip and the adjacent protruding nozzle row group 4 b. It is desirable to have different directivities in the long side direction of the cross section.

FIG. 11 shows the arrangement of the painting and drying / baking furnaces in the continuous painting line. The surface of the steel strip S1 is coated with a coater facility 14, and dried and baked in a drying / baking furnace 15 along a predetermined temperature pattern. Subsequently, it is cooled to near normal temperature by the cooling device 16. Conventionally, this cooling device 16 has achieved air quality cooling at the front stage and water cooling at the rear stage, thereby ensuring the quality of the paint surface at the front stage and rapid cooling at the rear stage. By using the cooling device 16 as a cooling device using the protruding nozzle according to the present invention, it is possible to obtain a facility configuration with good cooling efficiency without using water cooling.

FIG. 12 shows an example in which the cooling device using the protruding nozzle according to the present invention is applied to the cooling device after the plating alloying treatment of the continuous hot dip galvanizing equipment. The steel strip S2 is introduced into the plating pot 19 through a turn-down roll 18 provided in the turn-down section 17. After being pulled up vertically via the sink roll 20 and adjusted to a predetermined plating thickness by the plating machine 21, it is heated to the alloying treatment temperature by the alloying heating device 22, and then kept in the holding furnace 23. The steel strip S2 that has been alloyed is cooled by the cooling device 24, the upper rolls 25 and 26, and the cooling device 27 provided in the down path, and sent to the immersion cooling device 28 that is the final cooling.

  By applying the cooling device using the protruding nozzle according to the present invention to the cooling device 24 and the cooling device 27, it becomes possible to increase the cooling efficiency and to lower the entire alloying furnace, and the steel strip after the alloying treatment It becomes possible to measure the soundness of the alloy layer by rapidly cooling S2.

FIG. 13 shows an example in which the cooling device using the protruding nozzle according to the present invention is applied to the cooling device after plating in the same continuous hot dip galvanizing equipment. The steel strip S2 is adjusted to a predetermined plating thickness by the plating machine 21, then cooled by the cooling device 24 and the cooling device 27 provided in the down path, and sent to the immersion cooling device 28 which is the final cooling. By applying the cooling device using the protruding nozzle according to the present invention to the cooling devices 24 and 27, it becomes possible to increase the cooling efficiency and to lower the entire alloying furnace.

FIG. 14 shows an example of a continuous annealing pickling facility for a stainless steel strip. The stainless steel strip S3 is heated and soaked at a predetermined annealing temperature in the heating zone 29, and then cooled to the end point temperature at a predetermined cooling rate in the cooling zone 30. Subsequently, the scale generated on the surface of the stainless steel strip is removed by the roll group disposed on the upper and lower surfaces of the stainless steel strip S3 in the descaling device 31. Thereafter, it is introduced into the pickling tank 32. By applying the cooling device using the protruding nozzle according to the present invention to the cooling zone 30, the cooling efficiency can be increased and a compact device configuration can be obtained.

  As described above, according to the present invention, in order to obtain a high cooling rate, the steel strip cooling device in which the gas circulation equipment is made compact by increasing the ejection speed from the nozzle and decreasing the resistance coefficient of the nozzle. In addition, if a crimping structure using a pipe expander is used, it is possible to provide a steel strip cooling device that eliminates distortion of the nozzle due to welding and improves manufacturing accuracy. Furthermore, by making the shape of the nozzle base flat, and making the width direction of the steel strip a long side direction, gas jetted from the nozzle is reduced from staying on the surface of the steel strip, and in the width direction of the steel strip. The cooling uniformity can be further improved.

It is side part sectional drawing of the cooling device of the continuous annealing equipment to which this invention is applied. It is an AA arrow line view of FIG. It is detail drawing of the protrusion nozzle of this invention. It is a figure which shows the attachment point of the protrusion nozzle of this invention. It is a graph which shows the resistance coefficient of a protrusion nozzle. It is a detailed view of a conical protruding nozzle having a flat nozzle tip. It is detail drawing of a cone-shaped protrusion nozzle. It is a figure which shows the heat flow rate on the steel strip right under various shape nozzles. It is a figure which shows the relationship between the flatness of a nozzle front-end | tip part, and a resistance coefficient. It is a figure which shows the example of arrangement | positioning of the cone-shaped protrusion nozzle whose nozzle front-end | tip part is flat shape. It is the schematic of the continuous painting line to which this invention is applied. It is the schematic of the continuous hot-dip galvanization equipment to which this invention is applied. It is the schematic of another continuous hot-dip galvanization equipment to which this invention is applied. It is the schematic of the stainless steel continuous annealing pickling equipment to which this invention is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Furnace 2 Cooling device 3 Cooling box 4 Protruding nozzle 5 Suction side duct 6 Heat exchanger 7 Circulating blower 8 Discharge side duct 9 Upper roll 10 Pressing roll 11 Lower roll 12 Steel strip 14 Coater equipment 15 Drying / baking furnace 16 Cooling device 17 Turn-down section 18 Turn-down roll 19 Plating pot 20 Sink roll 21 Plating machine 22 Alloying heating device 23 Holding furnace 24 Cooling device 25, 26 Upper roll 27 Cooling device 28 Immersion cooling device 29 Heating zone 30 Cooling zone 31 Descaling device 32 Pickling tank S1-S3 Steel strip W Weld overlay

Claims (5)

In the cooling device for the steel strip that cools the steel strip that runs by disposing a protruding nozzle on the surface of the cooling box and ejecting refrigerant from the protruding nozzle, the distance from the nozzle tip to the steel strip surface is maintained at 30 to 100 mm. A plurality of projecting nozzles are projected from the surface of the cooling box, and the A / a of the projecting nozzle is set to 2 ≦ A / a ≦ 9 (a: opening sectional area of the nozzle tip, A: opening sectional area of the nozzle base), and cooling The distance from the box surface to the nozzle tip of the protruding nozzle is 150 to 200 mm, and the flatness a1 / a2 of the opening cross section of the nozzle tip is 1 <a1 / a2 <9 (a1: length of the opening cross section of the nozzle tip) A cooling device for a steel strip, characterized in that the projecting nozzle for improving the heat transfer coefficient directly under the nozzle (side, a2: short side of the opening cross section of the nozzle tip) is arranged in a cooling box .   The steel strip cooling device according to claim 1, wherein the projecting nozzle row group in the width direction of the steel strip and the projecting nozzle row group adjacent thereto are different in directivity in the long side direction of the nozzle tip opening section. A steel strip cooling device characterized by that. The steel strip cooling device according to claim 1 or 2 , wherein the protruding nozzle has a nozzle base fixed to a mounting hole provided in a cooling box by pipe expansion joining. The protruding nozzle is attached so that the nozzle base does not protrude from the inner surface of the cooling box to the mounting hole provided in the cooling box, and the end of the nozzle base and the inner surface of the mounting hole are joined by welding. the cooling apparatus of steel strip according to claim 1 or 2, characterized in that the deposition of the weld is construction so as not to protrude from the cooling box inner surface. The steel strip cooling device according to any one of claims 1 to 4 , wherein the refrigerant is H ₂ gas or a mixed gas of H ₂ gas and N ₂ gas or other inert gas.

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