JP2021038455A - Metal plate hardening device, metal plate hardening method, and steel plate manufacturing method - Google Patents

Abstract

To provide a metal plate hardening device, a metal plate hardening method and a steel plate manufacturing method capable of maintaining a uniform cooling rate in the plate width direction of a metal plate by early eliminating clogging of foreign matter in the opening of the slit nozzle.SOLUTION: There is provided a metal plate hardening device that cools a metal plate by immersing it in a liquid, comprising a tank containing a liquid for immersing the metal plate, an ejection device having a plurality of slit nozzles 24 for ejecting the liquid on both sides of the metal plate, and at least a part thereof provided in the liquid of the tank, and means for changing the opening amount of the slit nozzle so as to change the opening amount of the metal plate in the longitudinal direction.SELECTED DRAWING: Figure 7

Description

The present invention is a metal plate quenching device and a method for quenching a metal plate, which can always make the cooling rate in the width direction of the metal plate uniform in a continuous annealing facility in which the metal plate is continuously annealed. Also related to the method of manufacturing steel sheets.

In the production of metal plates such as steel sheets, the metal plates are heated and then cooled in a continuous annealing facility to cause phase transformation, etc., to build the materials. In recent years, the demand for thinned high-strength steel sheets (HITEN) has been increasing in the automobile industry for the purpose of achieving both weight reduction of the vehicle body and collision safety. When manufacturing high-tensile steel, technology for rapidly cooling steel sheets is important. The water quenching method is known as one of the technologies having the fastest cooling rate of steel sheets. In the water quenching method, the heated steel sheet is immersed in water, and at the same time, cooling water is sprayed onto the steel sheet by a slit nozzle provided in the water to quench the steel sheet.

If the cooling rate of the steel sheet in the plate width direction becomes non-uniform during quenching of the steel sheet, there arises a problem that the tensile strength of the steel sheet becomes non-uniform in the plate width direction. Various methods have been conventionally proposed in order to prevent non-uniform cooling during quenching of such a steel sheet.

For example, in Patent Document 1, slit nozzles are provided in multiple stages in the immersion water, and the slit nozzles are separated from each other in the direction of passing the metal plate so that the jet of cooling water colliding with the surface to be cooled of the metal plate is generated. A method of uniformly cooling a metal plate in the width direction by flowing out from a gap between each nozzle to the rear of the nozzle is disclosed.

Further, in Patent Document 2, although the slit nozzle is not provided in water, a high-pressure water stream directly collides with the plate width end by using a masking device that can move to the end of the slit nozzle. There is no problem, and a method that can prevent the occurrence of temperature unevenness in the plate width direction is disclosed.

Japanese Unexamined Patent Publication No. 59-153843 JP-A-2007-319928

When the cooling water injected by the slit nozzle is circulated and used, foreign matter such as rust may be mixed in the cooling water due to corrosion of the piping or the like. If the foreign matter has a certain size or more, the foreign matter cannot pass through the opening of the slit nozzle, and the slit nozzle may be clogged.

In particular, when foreign matter is clogged only in a part of the opening of the slit nozzle, the slit nozzle cannot uniformly inject water in the plate width direction. As a result, the cooling rate of the metal plate in the plate width direction becomes non-uniform, and the physical properties of the metal plate become uneven. Patent Document 1 and Patent Document 2 do not describe or suggest problems caused by clogging of the foreign matter.

The present invention has been completed in view of the above problem, and is a metal plate capable of maintaining a uniform cooling rate in the width direction of the metal plate by early eliminating clogging of foreign matter in the opening of the slit nozzle. An object of the present invention is to provide a quenching apparatus, a method for quenching a metal plate, and a method for manufacturing a steel plate.

The means for solving the above problems are as follows.
[1] A metal plate quenching device for immersing a metal plate in a liquid to cool it, a tank containing the liquid for immersing the metal plate and a plurality of slit nozzles for injecting the liquid onto both surfaces of the metal plate. A metal plate comprising, at least a part of which is provided in the liquid of the tank, and an opening amount variable means for changing the opening amount of the metal plate in the longitudinal direction with respect to the opening of the slit nozzle. Quenching device.
[2] A method for quenching a metal plate, which is performed by using the metal plate quenching apparatus according to [1].
[3] The method for quenching a metal plate according to [2], wherein the opening amount is increased when at least a part of the opening of the slit nozzle is clogged.
[4] After the steel sheet is continuously annealed, it is annealed by the method of quenching the metal plate according to [2] or [3] to obtain a high-strength cold-rolled steel sheet, a hot-dip galvanized steel sheet, an electric zinc-plated steel sheet, and the like. And a method for manufacturing a steel sheet for manufacturing any one of alloyed hot-dip galvanized steel sheets.

According to the present invention, even if the opening of the slit nozzle is clogged with foreign matter, the foreign matter can be quickly removed by widening the size of the opening, thereby maintaining a uniform cooling rate in the width direction of the metal plate. it can.

FIG. 1 is an explanatory diagram showing a basic configuration of a metal plate quenching apparatus according to an embodiment of the present invention. FIG. 2 is an enlarged view showing the vicinity of the ejection device of FIG. FIG. 3 is a cross-sectional view of the slit nozzle of FIG. FIG. 4 is an enlarged view of the opening of the slit nozzle of FIG. FIG. 5 is a cross-sectional view when the opening of the slit nozzle of FIG. 1 is clogged with foreign matter such as rust. FIG. 6 is an enlarged view of the opening of the slit nozzle of FIG. FIG. 7 is a cross-sectional view of the slit nozzle when the opening of the slit nozzle of FIG. 1 is widened. FIG. 8 is an enlarged view of the opening of the slit nozzle of FIG. 7. FIG. 9 is a graph showing the results of Example 1 of the present invention. FIG. 10 is a graph showing the results of Comparative Example 1.

Hereinafter, an embodiment of the present invention will be specifically described with reference to the drawings.

FIG. 1 is a diagram showing a basic configuration of a metal plate quenching device (hereinafter, may be simply referred to as “quenching device”) 11 according to an embodiment of the present invention, and FIG. 2 is a diagram showing a quenching device shown in FIG. It is an enlarged view of the vicinity of the ejection device 4 of the device 11. The quenching apparatus 11 can be applied to a cooling facility provided on the outside of the soaking tropics of a continuous annealing furnace. FIG. 1 shows a pair of seal rolls 3 provided at the solitary tropical outlet of a continuous annealing furnace. The quenching device 11 includes a tank (water tank 1 in the example of FIG. 1) containing water 2 which is a refrigerant (liquid) for cooling the metal plate 5, and at least a part of the liquid in the tank (in the example of FIG. 1). It is provided in water 2) and is provided with a ejection device 4 for spraying a liquid on both surfaces of the metal plate 5 to cool the metal plate 5. Further, on the outlet side of the ejection device 4, a sink roll 6 for changing the longitudinal direction (passing direction) of the metal plate 5 while immersing the metal plate 5 in water is provided.

The ejection device 4 includes a plurality of slit nozzles 14 and 24 for ejecting water, and nozzle units 34 and 44 for holding the slit nozzles 14 and 24. The pair of nozzle units 34 and 44 are arranged so as to face the front and back surfaces of the metal plate 5 while forming a gap between them. When the metal plate 5 is passed through the gap in the vertical direction, water is ejected from the slit nozzles 14 and 24 toward the front and back surfaces of the metal plate 5. In the examples of FIGS. 1 and 2, the left side of the metal plate 5 is the front surface, and the right side is the back surface. On the left side of the drawing, the nozzle unit 34 is arranged with the slit nozzle 14 facing the front surface of the metal plate 5, and on the right side of the drawing, the nozzle unit 44 is arranged with the slit nozzle 24 facing the back surface of the metal plate 5. .. Although not shown, the nozzle units 34 and 44 and the slit nozzles 14 and 24 extend over the entire plate width of the metal plate 5. The openings at the tips of the slit nozzles 14 and 24 also extend over the entire plate width of the metal plate 5, and the metal plate is cooled over the entire plate width direction by ejecting water from the openings.

The nozzle units 34 and 44 are provided so that a part of the nozzle units 34 and 44 is immersed in water and the rest is discharged from the water. The metal plate 5 that has been passed through is charged into the gap inside the portion of the nozzle units 34, 44 exposed to water, then immersed in water, and water is ejected from the slit nozzles 14 and 24. A plurality of slit nozzles 14 and 24 are provided in the nozzle units 34 and 44 along the plate passing direction. Some slit nozzles (eg, the slit nozzle provided at the top in FIG. 1) may be located above the water surface, and more specifically, at least a part of the slit nozzle opening is submerged in water. It does not have to be soaked. The slit nozzle located above the water surface is downward so that the water can be ejected diagonally downward for the purpose of suppressing the water spouting generated when the high temperature metal plate 5 is introduced into the water. It is preferable that it is provided diagonally toward the surface.

Although not shown, each slit nozzle in the ejection device 4 is connected to a pipe provided with a pump in the middle. The water 2 in the water tank 1 is pumped up in the pipe by the pump and pumped to the slit nozzles 14 and 24, so that high-pressure water is ejected from the openings of the slit nozzles 14 and 24. As shown by the arrow in FIG. 3, the water pumped by the pump is divided into upper and lower parts in the vicinity of the rear inner wall opposite to the opening 24a of the slit nozzle 24, and then pumped forward to both sides. After the flows merge, they are ejected from the opening 24a.

Further, the water 2 in the water tank 1 is maintained at a water temperature suitable for quenching. For example, a part of the water 2 in the water tank 1 is sent to an external cooling facility such as a cooling tower to be cooled, and then returned to the water tank 1, so that the water temperature in the water tank 1 can be prevented from rising. For example, the water temperature in the water tank 1 particularly suitable for quenching is preferably more than 0 ° C. and 50 ° C. or lower, and particularly preferably 10 ° C. or higher and 40 ° C. or lower.

Then, in the quenching apparatus according to the present invention, unlike the conventional slit nozzle, it is possible to widen the slit gap of the opening. Hereinafter, a specific description will be given with reference to FIGS. 3 to 8.

First, FIG. 3 is a cross-sectional view of the slit nozzle 24 of FIG. 1 perpendicular to the front and back surfaces of the steel plate and including the plate passing direction, and FIG. 4 is a cross-sectional view of the slit nozzle 24 of FIG. It is an enlarged view seen from the side opposite to the injection direction. FIG. 5 is a cross-sectional view when the opening of the slit nozzle of FIG. 1 is clogged with foreign matter such as rust, and FIG. 6 is an enlarged view of the opening of the slit nozzle of FIG. Further, FIG. 7 is a cross-sectional view of the slit nozzle 24 when the opening of the slit nozzle of FIG. 1 is widened, and FIG. 8 shows the opening 24a of the slit nozzle of FIG. 7 on the side opposite to the liquid injection direction. It is an enlarged view seen from.

The opening 24a preferably has a longitudinal shape in the width direction of the metal plate in a plan view viewed from the opposite side of the liquid injection direction. In the example of FIG. 4, the opening 24a is long in the plate width direction of the metal plate 5 (vertical direction on the paper surface in FIGS. 3 and 5 and left-right direction in FIGS. 4 and 6), and the plate passing direction is short. Form a substantially rectangular shape. The shape of the opening 24a may be as long as the length in the plate width direction is longer than the length in the plate-through direction, and may be, for example, an elliptical shape in a plan view. The slit gap of the opening 24a described above means the opening amount of the metal plate 5 in the plate passing direction (vertical direction in each figure), and is indicated by reference numeral A in FIG.

As shown in FIGS. 5 and 6, when the quenching apparatus is continuously operated, foreign matter P such as rust is formed in the opening 24a due to reasons such as corrosion of the inner surface of the nozzle connected to the upstream of the slit nozzle 24. It may get clogged. More specifically, when a relatively large foreign matter P is generated, the foreign matter P cannot pass through the vertical width, and a part of the opening 24a in the plate width direction is blocked by the foreign matter P. As shown in FIG. 6, when the clogging due to the foreign matter P occurs only in a part in the plate width direction, the flow of water ejected from the opening 24a is not uniform in the plate width direction, and the plate width of the metal plate 5 It causes uneven cooling in the direction.

Whether or not a part of the opening 24a is clogged with the foreign matter P can be visually confirmed from the outside by installing a viewing window or the like in the water tank 1. When it is confirmed that the foreign matter P such as rust is clogged, the slit gap A is temporarily widened as shown in FIGS. 7 and 8. More specifically, the slit gap A is widened so as to be larger than the length of the foreign matter P in the plate-passing direction. As a result, foreign substances such as rust are quickly removed by the flow of cooling water (refrigerant). After the removal of the foreign matter is confirmed, the size of the slit gap A may be restored as shown in FIGS. 3 and 4.

As a structure for widening the slit gap A, specifically, an opening amount variable means including an air cylinder or the like can be used. For example, in FIG. 7, the opening amount variable means includes an upper air cylinder 7, an upper air tube 71 that moves air in and out of the upper air cylinder 7, a lower air cylinder 8, and a lower air that moves air in and out of the lower air cylinder 8. It has a tube 81. In the upper air cylinder 7 (and lower air cylinder 8), the upper piston 72 (and the lower piston 82) is pushed out when compressed air is supplied into the cylinder, and then the upper piston 72 (and the lower piston 82) is exhausted when the air in the cylinder is exhausted. The structure is such that 72 (and the lower piston 82) returns to its original position. The upper piston 72 (and the lower piston 82) is provided in contact with the upper end portion (and the lower end portion) of the slit nozzle 24 forming the opening 24a. The vertical movement of the upper piston 72 (and the lower piston 82) deforms the tip of the slit nozzle 24, and the size of the slit gap A is changed.

Since the upper air cylinder 7 and the lower air cylinder 8 are used in water, it is preferable to use waterproof products. Further, in order to make the size of the slit gap A uniform in the longitudinal direction of the opening (the width direction of the metal plate), a plurality of upper air cylinders 7 and lower air cylinders 8 are installed in the longitudinal direction of the opening. Is preferable. The mode of changing the size of the slit gap A shown in FIG. 7 is naturally applicable to the slit nozzle 14.

From the viewpoint of improving the production efficiency, the operation for removing the foreign matter P described above is preferably performed without stopping the operation of the continuous annealing equipment. The slit nozzles 14 and 24 may be opened and closed by remote control in order to remove the foreign matter P without stopping the operation of the continuous annealing equipment. When the clogging of foreign matter is visually confirmed during the operation, the foreign matter can be removed by remote control, so that the adverse effect of the clogging of the foreign matter can be minimized immediately without stopping the operation. As a result, it is possible to prevent the occurrence of cooling unevenness of the metal plate for a long time and suppress the occurrence of quality unevenness in the product. As an example, the upper air tube 71 and the lower air tube 81 may be wired to the outside of the water tank 1 and connected to a controller or the like. By operating the controller outside the system, the operator can control the operation of the upper piston 72 and the lower piston 82 and remove foreign matter by remote control.

The size of the slit gap A when the foreign matter P is not clogged as shown in FIGS. 3 and 4 is preferably 2 to 5 mm. Further, as shown in FIGS. 7 and 8, the size of the slit gap A when clearing the clogging of the foreign matter P is preferably larger than the maximum value of the length of the foreign matter P in the plate-passing direction, specifically. It is preferably 10 to 50 mm. The specific value of the lengths of the slit nozzles 14 and 24 in the plate width direction is preferably 1000 to 2500 mm, and the lengths of the openings 14a and 24a of the slit nozzles 14 and 24 in the plate width direction are also within the range. Is preferable.

The quenching apparatus and the quenching method using the quenching apparatus according to the present embodiment as described above can be applied to the production of a metal plate product (metal plate shipped as a product), and is a method for producing a high-strength steel plate (HITEN). It is particularly preferable to apply to. More specifically, it is preferably applied to a method for producing a steel sheet having a tensile strength of 580 MPa or more. The upper limit of the tensile strength is not particularly limited, but as an example, it may be 1600 MPa or less.

The cooling start temperature of the steel sheet (the temperature immediately before entering the ejection device 4) is not particularly limited as long as the above-mentioned high-strength steel sheet (high-tensile steel) can be produced, but is preferably more than 400 ° C. and 900 ° C. or lower, preferably 600 ° C. More than 800 ° C. or lower is particularly preferable.

Incidentally, examples of the above-mentioned high-strength steel sheets (HITEN) include high-strength cold-rolled steel sheets, hot-dip galvanized steel sheets on which surface treatment is applied, electric zinc-plated steel sheets, alloyed hot-dip galvanized steel sheets, and the like.

During the production of high-tensile steel, it is important to perform precise structure control by rapidly cooling the steel sheet, and the uniformity of cooling on the front and back surfaces of the steel sheet is strictly required. By manufacturing high-tensile steel by applying the quenching apparatus according to the present invention, clogging due to foreign matter such as rust can be quickly eliminated, cooling unevenness due to the clogging can be prevented, and high-tensile steel having uniform physical properties can be produced accurately. ..

As a specific example of the composition of the high-strength steel sheet, in terms of mass%, C is 0.04% or more and 0.25% or less, Si is 0.01% or more and 2.50% or less, and Mn is 0.80% or more and 3.70. % Or less, P 0.001% or more and 0.090% or less, S 0.0001% or more and 0.0050% or less, sol. Al is 0.005% or more and 0.065% or less, if necessary, at least one or more of Cr, Mo, Nb, V, Ni, Cu, and Ti is 0.5% or less, and further, if necessary. , B and Sb are 0.01% or less, respectively, and the balance is Fe and unavoidable impurities.

The embodiment of the present invention is not limited to the example of quenching a steel sheet, and can be applied to quenching of all metal plates other than steel sheets, and also to quenching using a liquid other than water. it can.

Hereinafter, the present invention will be described in more detail with reference to Examples.

(Example 1 of the present invention)
When producing a high-strength cold-rolled steel sheet having a plate thickness of 1.0 mm and a plate width of 1000 mm and a tensile strength of 1470 MPa, the quenching apparatus shown in FIGS. Quenching was performed at a plate passing speed of 1.0 m / s. Further, the opening of the slit nozzle has an initial slit gap A of 3 mm and an overall length in the plate width direction of 2000 mm. Further, as shown in FIGS. 5 and 6, the central portion of some slit nozzles in the plate width direction is pre-filled with foreign matter P (length 200 mm in the plate width direction) such as rust. By widening the opening of the slit nozzle until the slit gap A became 20 mm, it was confirmed that foreign substances such as rust were quickly removed by the force of the flow of cooling water, and the slit gap A was returned to 3 mm. ..

In addition, the temperature of the steel plate being passed through the quenching device was measured. Specifically, the temperature of the area to be measured of the steel sheet was measured over time using a thermocouple type thermometer. The cooling start temperature (temperature immediately before entering the ejection device 4) of the steel sheet was 730 ° C, and the cooling end temperature (temperature immediately after exiting the water tank 1) was 30 ° C. From the relationship between the elapsed time after the start of cooling and the temperature of the steel sheet, the cooling rate distribution in the width direction of the steel sheet at the moment when the steel sheet passed through the slit nozzle was calculated. The results are shown in FIG.

(Comparative Example 1)
An experiment was conducted in the same manner as in Example 1 of the present invention using the quenching apparatus described in Patent Document 1. In this example, the slit gap A could not be widened, and foreign matter such as rust that had been clogged in advance could not be removed. The calculation result of the cooling rate distribution is shown in FIG.

<Evaluation of cooling rate>
In FIG. 9 (Example 1 of the present invention), the cooling rate distribution of the steel sheet in the plate width direction is substantially constant regardless of the plate width position, and the steel sheet is uniformly cooled. The cooling rate was 1500 ° C./s.

On the other hand, in FIG. 10 (Comparative Example 1), the cooling rate of the other portion was higher than that of the central portion corresponding to the location where the clogging occurred, and non-uniform cooling occurred. The cooling rate is about 900 ° C / s in the central part and about 1500 ° C / s in the other parts, and the cooling rate in the central part is about 40% (about 1500 ° C / s → about 900 ° C) with respect to the other parts. / S) It was decreasing.

As a result, it was shown that by applying the present invention, it is possible to suppress a decrease in the cooling rate of the metal plate corresponding to the position where foreign matter such as rust is clogged, and to make the cooling rate in the plate width direction uniform.

<Evaluation of tensile strength>
The tensile strength of the steel sheet produced according to Example 1 of the present invention was about 1470 MPa over the entire plate width direction.

On the other hand, the tensile strength of the steel sheet manufactured according to Comparative Example 1 is about 1350 MPa in the central portion of the plate width and about 1470 MPa in other parts, and the tensile strength in the central portion is lowered and the tensile strength in the plate width direction is poor. Uniformity was seen.

As a result, it was shown that by applying the present invention, it is possible to prevent a decrease in steel sheet characteristics and non-uniformity due to a decrease in the cooling rate of the steel sheet corresponding to the position where foreign matter such as rust is clogged.

1 Water tank 2 Water 3 Seal roll 4 Ejector 5 Metal plate 6 Sink roll 11 Quenching device 14, 24 Slit nozzles 14a, 24a Openings 34, 44 Nozzle unit 7 Upper air cylinder 71 Upper air tube 72 Upper piston 8 Lower air cylinder 81 Lower air tube 82 Lower piston A Slit gap P Foreign matter

Claims (4)

A metal plate quenching device that cools a metal plate by immersing it in a liquid.
A tank containing a liquid for immersing the metal plate and
A ejector having a plurality of slit nozzles for injecting the liquid on both sides of the metal plate, and at least a part thereof provided in the liquid of the tank.
A metal plate quenching device comprising: an opening amount variable means for changing the opening amount of the metal plate in the longitudinal direction with respect to the opening of the slit nozzle. A method for quenching a metal plate, which is performed by using the metal plate quenching apparatus according to claim 1. The method for quenching a metal plate according to claim 2, wherein the opening amount is increased when at least a part of the opening of the slit nozzle is clogged. After the steel sheet is continuously annealed, it is annealed using the method for quenching a metal plate according to claim 2 or 3, and a high-strength cold-rolled steel sheet, a hot-dip galvanized steel sheet, an electric zinc-plated steel sheet, and an alloyed hot-dip zinc A method for manufacturing a steel sheet that manufactures any one of plated steel sheets.

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