JP7180636B2 - Apparatus for quenching metal plate, method for quenching metal plate, and method for manufacturing steel plate - Google Patents

Description

The present invention provides a metal plate quenching apparatus and a metal plate quenching method capable of always uniforming the cooling rate in the width direction of a metal plate in a continuous annealing facility that performs annealing while continuously passing the metal plate. and a method for manufacturing a steel plate.

In the production of metal sheets such as steel sheets, the metal sheets are heated and then cooled in a continuous annealing facility, and the material is refined by, for example, causing phase transformation. In recent years, the automotive industry has seen an increase in demand for thin high-strength steel sheets (high-tensile steel) for the purpose of achieving both weight reduction and collision safety. A technique for rapidly cooling steel sheets is important when manufacturing high-tensile steel. A water quenching method is known as one of the techniques with the fastest cooling rate for steel sheets. In the water quenching method, the steel sheet is quenched by immersing the heated steel sheet in water and spraying cooling water onto the steel sheet through a slit nozzle provided in the water.

If the cooling rate in the width direction of the steel sheet becomes uneven during quenching of the steel sheet, a problem arises in that the tensile strength of the steel sheet becomes uneven in the width direction. Conventionally, various methods have been proposed to prevent uneven cooling during quenching of steel sheets.

For example, in Patent Document 1, slit nozzles are provided in multiple stages in immersion water, and the slit nozzles are spaced apart from each other with respect to the passing direction of the metal plate, so that the jet of cooling water that collides with the surface to be cooled of the metal plate is A technique is disclosed in which the metal plate is uniformly cooled in the width direction by flowing out from the gaps between the nozzles to the rear of the nozzles.

Further, in Patent Document 2, the slit nozzle is not provided in the water, but by using a movable masking device at the end of the slit nozzle, the high-pressure water flow directly collides with the edge of the plate width. There is disclosed a method that can prevent the occurrence of temperature unevenness in the sheet width direction.

JP-A-59-153843 JP-A-2007-319928

When the cooling water jetted from the slit nozzle is circulated and used, foreign matter such as rust may be mixed into the cooling water due to corrosion of the pipes or the like. If the foreign matter is larger than a certain size, the foreign matter cannot pass through the opening of the slit nozzle, possibly clogging the slit nozzle.

In particular, when only part of the opening of the slit nozzle is clogged with foreign matter, the slit nozzle cannot uniformly jet water in the plate width direction. As a result, the cooling rate in the width direction of the metal plate 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 the clogging of the foreign matter.

The present invention has been completed in view of this problem, and is capable of maintaining a uniform cooling rate in the width direction of the metal plate by quickly eliminating the 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 of quenching a metal plate, and a method of manufacturing a steel plate.

Means for solving the above problems are as follows.
[1] A metal plate quenching apparatus for cooling a metal plate by immersing it in a liquid, comprising a tank containing the liquid in which the metal plate is immersed, and a plurality of slit nozzles for injecting the liquid onto both sides of the metal plate. and an ejection device at least part of which is provided in the liquid of the tank; quenching equipment.
[2] A method of hardening a metal plate using the apparatus for hardening a metal plate according to [1].
[3] The method of quenching a metal plate according to [2], wherein the amount of opening is increased when clogging occurs in at least part of the opening of the slit nozzle.
[4] After the steel sheet is continuously annealed, it is quenched using the metal plate quenching method described in [2] or [3], high-strength cold-rolled steel sheet, hot-dip galvanized steel sheet, electrogalvanized steel sheet, and a steel sheet manufacturing method 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. can.

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

An embodiment of the present invention will be specifically described below with reference to the drawings.

FIG. 1 is a diagram showing the basic configuration of a metal plate quenching apparatus (hereinafter sometimes simply referred to as "quenching apparatus") 11 according to one embodiment of the present invention, and FIG. 4 is an enlarged view of the vicinity of the ejection device 4 of the device 11. FIG. The quenching device 11 can be applied to cooling equipment provided on the outlet side of the soaking zone of the continuous annealing furnace. FIG. 1 shows a pair of seal rolls 3 provided at the exit of the soaking zone of the continuous annealing furnace. The quenching apparatus 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. A spray device 4 is provided in the water 2) for spraying the liquid on both sides of the metal plate 5 to cool them. A sink roll 6 is provided on the exit side of the ejection device 4 to change the longitudinal direction (the threading direction) of the metal plate 5 while immersing the metal plate 5 in water.

The ejection device 4 comprises a plurality of slit nozzles 14, 24 for ejecting water, and nozzle units 34, 44 for holding the slit nozzles 14, 24. The pair of nozzle units 34 and 44 are arranged so as to face the front and rear surfaces of the metal plate 5, respectively, while forming a gap therebetween. Water is jetted from the slit nozzles 14 and 24 toward the front and back surfaces of the metal plate 5 when the metal plate 5 is vertically passed through the gap. In the examples of FIGS. 1 and 2, the left side of the metal plate 5 is the front side, and the right side is the back side. On the left side of the drawing, a nozzle unit 34 is arranged with the slit nozzle 14 facing the surface of the metal plate 5, and on the right side of the drawing, a 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 full width of the metal plate 5 . The openings at the tips of the slit nozzles 14 and 24 also extend over the entire width of the metal plate 5, and water is jetted from the openings, thereby cooling the metal plate over the entire length in the width direction.

The nozzle units 34, 44 are provided so that part of them are submerged in the water and the rest are above the water. The threaded metal plate 5 is inserted into the gaps inside the portions of the nozzle units 34 and 44 exposed to the water, then immersed in water, and water is jetted out from the slit nozzles 14 and 24 . A plurality of slit nozzles 14, 24 are provided in the nozzle units 34, 44 along the plate threading direction. Some of the slit nozzles (for example, the uppermost slit nozzle in FIG. 1) may be positioned above the water surface. It does not have to be immersed. The slit nozzle located above the surface of the water is arranged downward so that the water can be jetted obliquely downward for the purpose of suppressing the jetting of water that occurs when the high-temperature metal plate 5 is introduced into the water. It is preferably provided obliquely toward the .

Although not shown, each slit nozzle in the ejection device 4 is connected to a pipe having a pump in the middle. The water 2 in the water tank 1 is pumped up through the pipes by the pump and pressure-fed to the slit nozzles 14, 24, whereby high-pressure water is ejected from the openings of the slit nozzles 14, 24. FIG. As shown by the arrows in FIG. 3, the water pumped by the pump is divided into upper and lower parts near the inner wall of the slit nozzle 24 on the side opposite to the opening 24a, and then pumped forward. After the flows merge, it is jetted from the opening 24a.

Also, the water 2 in the water tank 1 is maintained at a water temperature suitable for quenching. For example, part of the water 2 in the water tank 1 is returned to the water tank 1 after being sent to cooling equipment such as an external cooling tower and cooled, thereby preventing the water temperature in the water tank 1 from rising. For example, the water temperature in the water tank 1 particularly suitable for quenching is preferably above 0°C and 50°C or less, and particularly preferably 10°C or more and 40°C or less.

Further, 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. A specific description will be given below with reference to FIGS. 3 to 8. FIG.

First, FIG. 3 is a cross-sectional view of the slit nozzle 24 of FIG. 1 taken along a plane perpendicular to the front and back surfaces of the steel sheet and including the sheet threading direction. It is the enlarged view seen from the injection direction and the opposite side. 5 is a cross-sectional view of the opening of the slit nozzle of FIG. 1 clogged with foreign matter such as rust, and FIG. 6 is an enlarged view of the opening of the slit nozzle of 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 is a view of the slit nozzle of FIG. It is an enlarged view seen from.

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

As shown in FIGS. 5 and 6, when the quenching apparatus continues to operate, 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 upstream of the slit nozzle 24. It can 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 portion of the opening 24a in the plate width direction is blocked by the foreign matter P. As shown in FIG. 6, when clogging due to foreign matter P occurs only partially in the plate width direction, the flow of water ejected from the opening 24a is not uniform in the plate width direction, and the width of the metal plate 5 is not uniform. This causes uneven cooling in the direction.

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

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

In addition, since the upper air cylinder 7 and the lower air cylinder 8 are used underwater, it is preferable to adopt waterproof products. In order to make the size of the slit gap A uniform in the longitudinal direction of the opening (the plate 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 preferred. Incidentally, the aspect of changing the size of the slit gap A shown in FIG. 7 is naturally applicable to the slit nozzle 14 as well.

From the viewpoint of improving the production efficiency, it is preferable to perform the operation for removing the foreign matter P described above without stopping the operation of the continuous annealing equipment. In order to remove the foreign matter P without stopping the operation of the continuous annealing equipment, the slit nozzles 14 and 24 may be opened and closed by remote control. When clogging with foreign matter is visually confirmed during operation, the adverse effects of clogging with foreign matter can be immediately minimized by removing the foreign matter by remote control without stopping the operation. As a result, it is possible to prevent the occurrence of uneven cooling of the metal plate from continuing for a long time, and to 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 operations of the upper piston 72 and the lower piston 82 and remove the foreign matter by remote control.

It is preferable that the size of the slit gap A is 2 to 5 mm when the foreign matter P is not clogged as shown in FIGS. 7 and 8, it is preferable that the slit gap A be larger than the maximum length of the foreign matter P in the sheet-passing direction. It is preferably 10-50 mm. A specific value of the length in the plate width direction of the slit nozzles 14, 24 is preferably 1000 to 2500 mm, and the length in the plate width direction of the openings 14a, 24a of the slit nozzles 14, 24 is also within this range. is preferred.

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

In addition, the cooling start temperature of the steel plate (the temperature immediately before entering the ejection device 4) is not particularly limited as long as the above high-strength steel plate (high tensile strength) can be manufactured, but for example, it is preferably more than 400 ° C. and 900 ° C. or less, and 600 ° C. More than 800° C. or less is particularly preferable.

Incidentally, the high-strength steel sheets (high-tensile steel) include high-strength cold-rolled steel sheets, and surface-treated hot-dip galvanized steel sheets, electro-galvanized steel sheets, alloyed hot-dip galvanized steel sheets, and the like.

When manufacturing high-tensile steel, it is important to rapidly cool the steel sheet to precisely control the structure, and the uniformity of cooling on the front and back surfaces of the steel sheet is strictly required. By applying the quenching apparatus according to the present invention to manufacture high tensile strength steel, clogging due to foreign matter such as rust can be quickly eliminated, uneven cooling due to the clogging can be prevented, and high strength steel with uniform physical properties can be produced with high accuracy. .

As a specific example of the composition of the high-strength steel sheet, in 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 is 0.001% or more and 0.090% or less, S is 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 of Cr, Mo, Nb, V, Ni, Cu, and Ti is 0.5% or less, and if necessary , B, and Sb are each 0.01% or less, and the balance is Fe and unavoidable impurities.

The embodiments of the present invention are not limited to the example of quenching a steel plate, but can be applied to quenching of metal plates in general other than steel plates, and can also be applied to quenching using liquids other than water. can.

EXAMPLES The present invention will be described in more detail below using examples.

(Invention Example 1)
When manufacturing a high-strength cold-rolled steel sheet with a thickness of 1.0 mm, a width of 1000 mm and a tensile strength of 1470 MPa class, the quenching apparatus shown in FIGS. 1 and 2 and the slit nozzle shown in FIGS. Quenching was performed at a threading speed of 1.0 m/s. The opening of the slit nozzle had an initial slit gap A of 3 mm and a total length of 2000 mm in the plate width direction. In addition, as shown in FIGS. 5 and 6, foreign matter P (having a length of 200 mm in the plate width direction) such as rust was clogged in advance in the central portion of some of the slit nozzles in the plate width direction. By widening the opening of the slit nozzle until the slit gap A reached 20 mm, it was confirmed that foreign matter such as rust was quickly removed by the force of the cooling water flow, and the slit gap A was returned to 3 mm. .

Also, the temperature of the steel sheet being passed through the quenching device was measured. Specifically, using a thermocouple type thermometer, the temperature of the region to be measured of the steel plate was measured over time. The cooling start temperature of the steel plate (the temperature immediately before entering the ejection device 4) was 730°C, and the cooling end temperature (the temperature immediately after leaving 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 was calculated at the moment when the steel sheet was passing through the slit nozzle. The results are shown in FIG.

(Comparative example 1)
Using the quenching apparatus described in Patent Document 1, an experiment was conducted in the same manner as in Example 1 of the present invention. In this example, the slit gap A could not be widened, and foreign matter such as rust clogged in advance could not be removed. FIG. 10 shows the calculation results of the cooling rate distribution.

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

On the other hand, in FIG. 10 (Comparative Example 1), the cooling rate was higher in the other portions than in the central portion corresponding to the clogged portion, resulting in non-uniform cooling. The cooling rate is about 900°C/s in the central portion and about 1500°C/s in the other portions. /s) was declining.

Accordingly, 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 clogged with foreign matter such as rust, and to make the cooling rate uniform in the plate width direction.

<Evaluation of tensile strength>
The tensile strength of the steel sheet manufactured according to Inventive Example 1 was about 1470 MPa in the entire width direction.

On the other hand, the tensile strength of the steel sheet manufactured in Comparative Example 1 is about 1350 MPa at the center of the width of the sheet and about 1470 MPa at the rest of the width. Uniformity was observed.

This indicates that the application of the present invention can prevent deterioration and non-uniformity of steel sheet properties due to a decrease in the cooling rate of the steel sheet corresponding to a position clogged with foreign matter such as rust.

1 Water tank 2 Water 3 Seal roll 4 Ejection device 5 Metal plate 6 Sink roll 11 Hardening 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 apparatus for cooling a metal plate by immersing it in a liquid,
a tank containing a liquid in which the metal plate is immersed;
an ejection device having a plurality of slit nozzles for ejecting the liquid on both sides of the metal plate, at least a part of which is provided in the liquid in the tank;
A hardening apparatus for a metal plate, comprising: an opening amount variable unit for uniformly changing an opening amount of the opening of the slit nozzle in the longitudinal direction of the metal plate in the longitudinal direction of the opening . A method of hardening a metal plate using the apparatus for hardening a metal plate according to claim 1 . 3. The method of 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 quenched using the method for quenching a metal sheet according to claim 2 or 3, and high-strength cold-rolled steel sheet, hot-dip galvanized steel sheet, electro-galvanized steel sheet, and alloyed hot-dip zinc. A method of manufacturing a steel sheet that manufactures any one of galvanized steel sheets.

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