JP7338783B2 - Quenching apparatus and method for metal plate, and method for manufacturing steel plate - Google Patents

Description

The present invention relates to a metal plate quenching apparatus and method for suppressing shape defects that occur in a metal plate during quenching, and a method for manufacturing a steel plate, in a continuous annealing facility that anneals the metal plate while it is continuously passed.

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 a 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. In this cooling, mist in which gas and water are mixed, or gas such as hydrogen is generally used as a cooling medium for the steel plate. At that time, the steel sheet suffers from shape defects due to out-of-plane deformation such as warpage and wave-like deformation. Conventionally, various methods have been proposed in order to prevent such shape defects during quenching of steel sheets.

For example, Patent Literature 1 discloses a method of mist cooling a metal strip while maintaining film boiling without transition boiling by appropriately controlling the water density of the mist sprayed onto the strip.

Further, Patent Document 2 discloses that in a cooling zone of a vertical continuous annealing furnace in which the strip is continuously annealed while being transported vertically, water contained in the mist sprayed on the strip drips down on the surface of the strip. A technique for suppressing the generation of temperature unevenness in the width direction of the strip caused by the above is disclosed.

Furthermore, in Patent Document 3, if the temperature at the Ms point at which the martensitic transformation of the metal plate starts is T _Ms (°C), and the temperature at the Mf point at which the martensitic transformation ends is T _Mf (°C), then during quenching and quenching is constrained by a pair of constraining rolls provided in the cooling liquid in the range where the temperature of the metal plate is from (T _Ms +150) (° C.) to (T _Mf −150) (° C.). It is

JP-A-2000-178658 Japanese Patent Application Laid-Open No. 2009-127060 Japanese Patent No. 6094722

However, as a result of verifying the methods described in Patent Literature 1 and Patent Literature 2, it was found that the effect of suppressing shape defects was small only by controlling the water volume density and suppressing the temperature unevenness in the width direction.

In addition, as a result of verifying the method described in Patent Document 3, the method of cooling the steel sheet by immersing it in a liquid is too strong, so the cooling rate tends to fluctuate, resulting in fluctuations in the temperature of the steel sheet when it passes through the restraint rolls. Therefore, the amount of warp may vary greatly in the longitudinal direction, and there is room for improvement.

SUMMARY OF THE INVENTION The present invention has been made to solve such problems, and it is an object of the present invention to provide a metal plate quenching apparatus, a quenching method, and a steel plate manufacturing method that can suppress shape defects that occur in a metal plate during quenching. aim.

The present inventors have made intensive studies to solve such problems, and as a result, have obtained the following findings. In the method of manufacturing metal sheets, there are cases where structure control is used to cause martensite transformation in the metal sheet during quenching. may have the shape of A high-strength steel sheet having a martensitic structure experiences the greatest stress in the vicinity of the Ms point to the Mf point where transformation expansion occurs during heat shrinkage during quenching, and loses its shape. Also, at this time, the stronger the cooling, the easier it is for the cooling rate to fluctuate. Therefore, after cooling using a mist that does not result in excessively strong cooling, a constraining roll that constrains the metal plate is arranged in the range where the temperature of the metal plate is from the Ms point to the Mf point, so that the amount of warpage is sufficiently reduced. can be reduced to Here, the Ms point is the temperature at which martensitic transformation starts, and the Mf point is the temperature at which martensitic transformation ends.

The present invention has been made based on the above findings and ideas, and has the following features.
[1] A cooling fluid injection device provided on the exit side of the soaking zone of the continuous annealing furnace and having a plurality of injection nozzles for injecting mist onto both surfaces of the continuously conveyed metal plate;
A hardening apparatus for a metal plate, comprising at least a pair of restraint rolls for restraining the metal plate from both sides in a region from a cooling start point to a cooling end point by the cooling fluid injection device.
[2] The plurality of jet nozzles are arranged so as to inject the mist onto the metal plate over the entire temperature range from the martensite transformation start temperature to the martensite transformation end temperature of the metal plate, [1] 4. The apparatus for hardening a metal plate according to 1.
[3] The metal plate quenching apparatus according to [1] or [2], which includes a draining spray nozzle downstream of the outlet of the cooling fluid injection device.
[4] A region in which mist is sprayed onto both surfaces of a continuously conveyed metal plate to cool it, and the temperature of the metal plate during cooling is at least between the martensite transformation start temperature and the martensite transformation end temperature. A method of hardening a metal plate, wherein the metal plate is restrained from both sides.
[5] The method of quenching a metal plate according to [4], wherein the mist has a water density of 100 L/m ² ·min or more and 800 L/m ² ·min or less.
[6] The steel sheet is continuously annealed and further quenched by the metal plate quenching method described in [4] or [5] to produce a high-strength cold-rolled steel sheet, a hot-dip galvanized steel sheet, an electrogalvanized steel sheet, or a hot-dip galvannealed steel sheet. A method of manufacturing a steel sheet that produces any of the galvanized steel sheets.

ADVANTAGE OF THE INVENTION According to the metal plate quenching apparatus, the quenching method, and the steel plate manufacturing method according to the present invention, it is possible to effectively suppress shape defects that occur in the metal plate during quenching.

FIG. 1 is a diagram showing an example of a metal plate hardening apparatus and hardening method according to the present invention. FIG. 2 is a diagram showing an example of a system for supplying air and water to a mist ejection nozzle in the metal plate quenching apparatus of the present invention. FIG. 3 is a diagram showing an example of a two-fluid nozzle. FIGS. 4(a) and 4(b) are diagrams showing examples of mist jetting nozzles. FIGS. 5(a) and 5(b) are diagrams showing mist cooling and conventional water quenching by the metal plate quenching apparatus and quenching method of the present invention, respectively. FIG. 6 is a view showing another example of the metal plate hardening apparatus and hardening method of the present invention. FIG. 7 is a graph showing the effects of the metal plate quenching apparatus and quenching method of the present invention in comparison with a comparative example. FIG. 8 is a diagram showing the definition of the amount of warpage of the metal plate in FIG.

EMBODIMENT OF THE INVENTION Hereinafter, with reference to drawings, embodiment of the hardening apparatus of a metal plate, the hardening method of a metal plate, and the manufacturing method of a steel plate of this invention is described concretely.

FIG. 1 is a view showing a metal plate quenching apparatus according to an embodiment of the present invention. This hardening apparatus is applied to a cooling facility provided on the exit side of a soaking zone of a continuous annealing furnace. When the metal sheet to be cooled is a steel sheet, this cooling equipment is installed to transform the austenite phase into martensite during cooling of the steel sheet to obtain the mechanical properties of the final product. Therefore, it has the ability to cool the range including the temperature range from the martensite transformation start temperature to the martensite transformation end temperature.

As shown in FIG. 1, the metal plate quenching apparatus of the present embodiment includes a cooling fluid injection device comprising a plurality of mist injection nozzles (ejection nozzles) 2, and a cooling region for restraining the metal plate 1 by the cooling fluid injection device. At least one pair of constraining rolls 3 and a draining spray nozzle 4 are provided. The mist jetting nozzle 2 jets mist 2a, which is a refrigerant (cooling fluid), from both sides of a metal plate (for example, a steel plate) 1 that is continuously passed through the metal plate 1 to perform rapid cooling. The constraining roll 3 constrains the metal plate 1 in the area from the cooling start point, which is the inlet of the cooling fluid injection device, to the cooling end point, which is the outlet of the cooling fluid injection device, to prevent deformation. The draining spray nozzle 4 is provided downstream of the outlet of the cooling fluid injection device, and ejects a gas 4a such as air or nitrogen onto the metal plate 1 from the outlet side of the metal plate 1 to discharge dripping water from the metal plate 1. .

The term "mist" as used herein refers to water or liquid in the form of a mist, in which minute droplets having droplet diameters of about 0.01 μm to several hundred μm are suspended in gas. In this embodiment, the mist is generated by mixing water and air and injecting the mixture. A sufficient cooling rate can be obtained by blowing air onto the metal plate to be cooled, at the same time as water droplets adhere to the metal plate. In addition, since water and air reach the metal plate in a mixed state, the cooling rate can be slowed down and stabilized as compared with the case where only water is jetted.

Here, if the droplet diameter of the mist is less than 10 μm, the water droplets are likely to evaporate, and a sufficient cooling rate may not be obtained. Further, when the droplet diameter of the mist exceeds 100 μm, the water droplets may adhere and remain on the metal plate, which tends to cause uneven cooling. Therefore, it is preferable that the droplet diameter of the mist is 10 μm or more and 100 μm or less.

For the mist ejection nozzle 2, for example, products such as a slit nozzle PSN manufactured by Ikeuchi Co., Ltd., a knife jet KJIS type (internal mixing type) manufactured by Kyoritsu Gokin Seisakusho Co., Ltd., and the like can be used.

FIG. 2 schematically shows a system for supplying air and water to the mist ejection nozzle 2 in the metal plate quenching apparatus of this embodiment. Further, FIG. 3 schematically shows a two-fluid nozzle used as the mist ejection nozzle 2 in this embodiment. In the present embodiment, the mist is generated by using the two-fluid nozzle shown in FIG. Any material can be used as long as it can be ejected.

When a two-fluid nozzle is used as the mist ejection nozzle 2, as shown in FIG. Also, water pumped from a water tank 62 by a pump 63 is supplied to the mist ejection nozzle 2 through the water pipe 6 . Here, the opening degrees of the supply valve 51 provided in the compressed air pipe 5 and the supply valve 61 provided in the water pipe 6 and the operation of the pump 63 are controlled by the flow controller 7 . In this manner, the compressed air and water may be supplied so that the pressure and amount of the compressed air and water supplied to the mist ejection nozzle 2 are within the allowable range according to the specifications of the mist ejection nozzle 2 . Further, in order to avoid clogging of the mist jetting nozzle 2, a filter may be provided on the side of the mist jetting nozzle 2 rather than the supply valve 61 of the water pipe 6. FIG.

Here, if the air-water volume ratio of the mist jetted from the mist jetting nozzle 2 is less than 50, the adhesion and residue of water on the metal plate 1 become significant, and uneven cooling tends to occur. On the other hand, if the air-water volume ratio exceeds 1000, the droplet diameter of the mist becomes too fine, and the cooling rate necessary for obtaining the properties required for the metal plate 1 may not be obtained. Therefore, it is preferable to set the air-water volume ratio of the mist ejected from the mist ejection nozzle 2 to 50 to 1,000.

In the metal plate quenching apparatus of this embodiment, the mist ejection nozzles 2 are arranged in 80 rows at intervals of 200 mm in the direction of movement of the steel plate (longitudinal direction of the steel plate).

However, the arrangement of the mist ejection nozzles 2 is not limited to this, as long as they are arranged so as not to cause uneven cooling in the width direction of the metal plate 1 . For example, as shown in FIG. 4A, when a slit nozzle 2A wider than the width of the metal plate 1 is used as the mist ejection nozzle 2, the nozzle interval I in the direction of movement of the steel plate is set to 100 to 600 mm. , preferably a slit nozzle. If the nozzle interval I in the steel plate traveling direction is less than 100 mm, the mist injection regions of the nozzles may interfere with each other, making it difficult to predict the cooling rate. This is because a sufficient cooling rate may not be obtained.

Further, as shown in FIG. 4(b), when a nozzle 2B having a spot-shaped or conical ejection shape is used as the mist ejection nozzle 2, a plurality of nozzles 2B are arranged on the metal plate 1 according to the nozzle standard. are preferably arranged side by side in the width direction. At this time, it is preferable that the mist injection areas of the respective nozzles 2B have no gaps or overlap sufficiently so that a uniform cooling rate can be obtained in the width direction of the metal plate 1 . Moreover, as shown in FIG. 4(b), it is preferable to attach a plurality of nozzles 2B arranged side by side in the width direction of the metal plate 1 to the header 21 for use.

Further, the mist ejection nozzles 2 may be arranged in a staggered manner, and the inclination angle of the ejection direction of the mist from the mist ejection nozzles 2 with respect to the metal plate 1 and the spread angle of the spray that spreads in a conical shape are the metal to be cooled. You may adjust according to the width|variety of the board 1, etc.

In this way, even when a plurality of nozzles arranged side by side in the width direction of the metal plate 1 are used as a nozzle set so as to obtain a uniform cooling capacity in the width direction of the metal plate 1, the nozzle set in the direction of movement of the steel plate It is preferable to set the interval I between them to be 100 to 600 mm. If the interval I between the nozzle sets in the direction of movement of the steel plate is less than 100 mm, the mist injection regions of the nozzles may interfere with each other, making it difficult to predict the cooling rate. This is because a sufficient cooling rate may not be obtained.

Here, in the present invention, in a temperature range where the shape of the metal plate 1 is most disturbed due to the cooling capacity of the cooling fluid injection device (mist injection nozzle) 2 and the positional relationship of the constraining roll 3, the constraining roll 3 is used to cool the metal plate. It is important to constrain 1. Therefore, in the metal plate quenching apparatus and the quenching method of the present embodiment, it is preferable to set the amount of mist and the water temperature of the mist for controlling the cooling capacity as follows.

First, when performing a quenching method in which mist 2a is jetted from a plurality of mist jetting nozzles 2 onto the surface of the metal plate 1 for cooling, the water density of the mist 2a is set to 100 L/m ² ·min or more and 800 L/m 2 ·min ^or more. min or less is preferable. If the water density of the mist 2a is less than 100 L/m ² ·min, the mechanical properties of the steel sheet cannot be obtained, and the position of the constraining roll becomes long from the cooling start position, resulting in an increase in the size of the equipment. In addition, when the water density of the mist 2a exceeds 800 L/m ² ·min, the cooling time from the start of cooling to the arrival of the restraint roll becomes short, and the cooling becomes unstable, and the shape is disturbed to the extent that it cannot be corrected by the restraint roll. This is because there are cases.

Further, the water density of the mist 2a is more preferably 200 L/m ² ·min or more and 500 L/m ² ·min or less.

In addition, the temperature of the cooling water that constitutes the particles of the mist 2a is preferably higher than 0 ° C. and 60 ° C. or lower from the viewpoint of equipment maintenance and obtaining a sufficient cooling rate, and 10 ° C. or higher and 50 ° C. or lower. is particularly preferred. If the temperature is below 0°C, the equipment may be damaged due to freezing, and if the temperature is higher than 60°C, the cooling rate will be slowed down, and the position of the restraint rolls will be long from the cooling start position, resulting in an increase in the size of the equipment. be.

In addition, in the vertical type mist cooling device, the water contained in the mist 2a falls downward along the metal plate 1 and adversely affects the cooling of the lower part. It can be controlled by injecting 2a or gas 4a upward about 30 degrees.

At that time, for the reasons described above, it is desirable to set the cooling rate of the metal plate 1 to 50° C./sec or more and 500° C./sec or less in order to arrange practical and effective constraining rolls according to the cooling capacity. If the cooling rate is less than 50°C/sec, the distance from the cooling start point to the restraint roll becomes long, resulting in an increase in the size of the facility. On the other hand, if it exceeds 500° C./sec, the cooling time from the start of cooling to the arrival of the constraining roll becomes short, and the cooling becomes unstable, and the shape may be disturbed to the extent that it cannot be straightened by the constraining roll.

In this way, by using the mist 2a and controlling the cooling rate to be within a suitable range, the effect of shape correction by the constraining rolls 3 can be improved.

In this embodiment, when performing the quenching method in which the surface of the metal plate 1 is cooled by spraying the mist 2a from the plurality of mist spray nozzles 2, the temperature of the metal plate 1 is in the range from the Ms point to the Mf point. A restraining roll 3 for restraining the metal plate 1 is arranged. Here, the Ms point refers to the temperature at which martensitic transformation of the metal plate 1 starts, and the Mf point refers to the temperature at which martensitic transformation ends. The temperature at the Ms point and the Mf point can be calculated from the composition of the metal plate 1 .

The restraint rolls 3 sandwich the metal plate 1 from the front and back surfaces in order to prevent deformation that may occur during quenching of the metal plate 1 . The pair of restraint rolls 3 are preferably arranged with their central axes shifted in the conveying direction of the metal plate 1 . By displacing the central axis, the binding force of the metal plate 1 can be increased, and the shape correcting force can be enhanced. As an example, it is preferable to arrange the restraint rolls 3 with their respective central axes shifted in the conveying direction by 40 mm or more and 150 mm or less, and more preferably 80 mm or more and 100 mm or less.

Moreover, it is desirable to push the metal plate 1 by the restraining rolls 3 and pass the metal plate 1 so as to wind the metal plate 1 around the restraining rolls 3 . By pressing the metal plate 1, it is possible to increase the straightening force of the steel plate and to prevent idle rotation of the restraint rolls 3. - 特許庁The pushing amount by one restraining roll 3 is preferably 0 mm or more and 2.5 mm or less when the case where the metal plate 1 is linearly threaded as shown in FIG. It is more preferable to be 0.5 mm or more and 1.0 mm or less.

FIGS. 5(a) and 5(b) show mist cooling by the metal plate quenching apparatus and quenching method of the present embodiment in comparison with conventional water quenching. As shown in FIG. 5(a), cooling from the Ms point to the Mf point is performed gently by mist cooling, so that the cooling from the Ms point to the Mf point is faster than the conventional water quenching shown in FIG. 5(b). becomes longer. Therefore, it has been conventionally practiced to flexibly respond to changes in the threading speed and plate thickness of the metal plate 1 by using the constraining rolls 3 in an appropriate temperature range or by increasing or decreasing the number of constraining rolls 3 used for constraining. It is easier than water quenching.

For example, considering the case where the plate thickness x plate threading speed is 1.5 (m/sec) mm and the temperature difference between the Ms point and the Mf point is 100°C, the water quenching shown in Fig. 5(b) If the cooling rate is 1500° C./(sec·mm), the distance L from point Ms to point Mf is 100 mm. On the other hand, in the mist cooling shown in FIG. 5A, the cooling rate is approximately 300° C./(sec·mm), and the distance L from point Ms to point Mf can be increased to 500 mm. Then, by providing a plurality of restraint rolls 3 in the section of the distance L (500 mm) from the Ms point to the Mf point, the metal plate 1 is reliably restrained in the temperature range from the Ms point to the Mf point, and the shape is corrected. can be reliably implemented. In addition, it is easy to respond flexibly to unsteady changes in the restraining position, such as changes in the strip threading speed and strip thickness.

Here, in the metal plate quenching apparatus and quenching method of this embodiment shown in FIG. Similarly, it becomes difficult to flexibly respond to changes in the threading speed and plate thickness of the metal plate 1 . Therefore, in some cases, the shape correction effect of the constraining rolls 3 cannot be sufficiently obtained. Further, when the distance L from the Ms point to the Mf point exceeds 1000 mm, the martensite transformation becomes insufficient, and desired material properties may not be obtained. Therefore, in order to effectively obtain the effect of shape correction by the constraining rolls 3 in the region from the Ms point to the Mf point, it is preferable to secure a distance L from the Ms point to the Mf point of approximately 200 to 1000 mm.

Furthermore, the mist 2a may be used over the entire length of the region of the metal plate 1 that requires cooling, including the side of the temperature higher than the Ms point and the side of the temperature lower than the Mf point.

In order to prevent the occurrence of roll flaws on the metal plate 1, it is preferable to rotate the restraint roll 3 in the circumferential direction by electric power. Furthermore, in order to adjust the straightening force of the metal plate 1, it is preferable that the restraint rolls 3 can be opened and closed as necessary (the amount of pressing into the metal plate 1 can be controlled).

The restraining rolls 3 may be made of a material that has excellent thermal conductivity and is strong enough to withstand the load when the metal plate 1 is pressed. Examples of the material of the restraint roll 3 include SUS304 or SUS310 defined in Japanese Industrial Standard JIS G4304 "Hot-rolled stainless steel plate and steel strip", or ceramics.

Next, an example using three or more restraint rolls 3 will be described with reference to FIG. In the following, description of the same points as in the case of using a pair of restraint rolls 3 may be omitted.

In the example of FIG. 6 , the front and back surfaces of the metal plate 1 are restrained by four (two pairs) of restraint rolls 3 . Even in the example where a plurality of pairs of restraint rolls are provided, it is preferable to push the metal plate 1 by the restraint rolls for the same reason as in the case where only two (one pair) of restraint rolls are provided. The pressing amount of each constraining roll is preferably 0 mm or more and 2.5 mm or less, and particularly preferably 0.5 mm or more and 1.0 mm or less. The number of constraining rolls 3 arranged on the front surface and the back surface of the metal plate 1 does not necessarily have to be the same. However, in order to apply a restraining force equally from both sides of the metal plate 1, the same number of restraining rolls 3 are arranged on the front surface and the back surface of the metal plate 1 so as to form a pair, or are arranged on the front surface and the back surface of the metal plate 1. It is preferable that the difference between the number of restraining rolls 3 to be applied is one.

In an example in which three or more constraining rolls are provided, the force for correcting the shape of the steel sheet during cooling can be further enhanced compared to an example in which only two (one pair) of constraining rolls are provided. In particular, even when cooling a high-strength steel sheet that is prone to deformation, deformation such as warping of the steel sheet during cooling can be further suppressed by providing three or more restraint rolls. On the other hand, if the number of constraining rolls is increased too much, there are problems such as equipment restrictions and a decrease in the cooling performance of the jetting device.

In addition, when the cooling by the mist 2a and the constraining roll 3 are used together as in the present embodiment, the mist 2a adheres and stays on the constraining roll 3, and the amount of droplets adhering and staying depends on the width direction of the metal plate 1. (that is, in the axial direction of the constraining roll 3). As a result, uneven cooling may occur, and the shape correction effect of the constraining rolls 3 may be reduced. Therefore, in order to solve such a problem, a draining mechanism (not shown) may be provided in the vicinity of the constraining roll 3 to remove droplets adhering to and staying on the constraining roll 3 . Specifically, an obstacle on the blade, a wiper, an air nozzle, or the like can be used as the draining mechanism.

As described above, the object of the present invention is to reduce the complex and non-uniform uneven shape that occurs when the structure expands in volume due to martensitic transformation during rapid cooling of the steel sheet. , is preferably applied to a method for manufacturing high-strength steel sheets (high-tensile steel).

More specifically, it is preferably applied to the production of steel sheets 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.

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

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 embodiment of the present invention is not limited to the example of quenching a steel plate, and can be applied to quenching of metal plates in general other than steel plates.

By applying the metal plate quenching apparatus, the quenching method, and the steel plate manufacturing method of the present invention, steel plate manufacturing tests were conducted and the effects thereof were verified.
(Invention Example 1)
Using the metal plate quenching apparatus shown in FIG. °C, a mist water density of 400 L/m ² ·min, and a temperature of 350 °C when passing through the constraining rolls.

Here, the composition of the high-strength cold-rolled steel sheet with a tensile strength of 1470 MPa class is, in mass%, C 0.20%, Si 1.0%, Mn 2.3%, P 0.005%, S was set to 0.002%.

The temperature at the Ms point of the high-strength cold-rolled steel sheet is 400°C, and the temperature at the Mf point is 300°C. Therefore, as described above, the temperature when passing through the constraining rolls may be set in the range of 400° C. to 300° C., so here it is set to 350° C. as described above.

Here, the central axes of the constraining rolls were shifted by 80 mm in the sheet threading direction, and the pressing amount of the constraining rolls 3 into the metal plate 1 was 0.5 mm.
(Invention Example 2)
Using the quenching apparatus shown in FIG. 6, operation was performed under the same conditions as in Example 1 of the present invention. The central axes of the opposing constraining rolls were all shifted by 80 mm in the sheet threading direction, and the pressing amount of the constraining rolls 3 into the metal plate 1 was 0.5 mm.
(Comparative example 1)
As a comparative example, the above-described high-strength cold-rolled steel sheet was produced using the cooling device shown in Patent Document 1 and the other conditions being the same as in the example of the present invention.
(Comparative example 2)
As a comparative example, the above-described high-strength cold-rolled steel sheet was manufactured using the cooling device shown in Patent Document 2, with the other conditions being the same as in the example of the present invention.
(Comparative Example 3)
As a comparative example, the above-described high-strength cold-rolled steel sheet was produced using the cooling device shown in Patent Document 3, with the other conditions being the same as in the example of the present invention.

Then, in each case (Invention Examples 1 and 2, Comparative Examples 1 and 3), 10 steel sheets after cooling were sampled at intervals of 100 m in the longitudinal direction, and the amount of warpage of each steel sheet was investigated. FIG. 8 shows the definition of the amount of warpage. Specifically, the height of the highest position when the steel plate was placed on a horizontal plane was taken as the amount of warpage.

The results of Examples 1 and 2 of the present invention and the results of Comparative Examples 1 and 3 are shown in FIG.

In Examples 1 and 2 of the present invention, the amount of warpage of the steel sheet was reduced to the range of 2.0 to 8.0 mm, and was suppressed to 10 mm or less over the entire longitudinal direction. On the other hand, in Comparative Examples 1 and 2, the amount of warpage of the steel plate was distributed in the range of 10.0 to 14.0 mm, and the effect of suppressing deformation was insufficient throughout the longitudinal direction. In addition, in Comparative Example 3, the amount of warpage of the steel plate varied in the range of 4.0 to 14.0 mm, and was not suppressed within the range of 10 mm or less over the entire longitudinal direction.

From this, the effectiveness of the metal plate quenching apparatus and quenching method, and the steel plate manufacturing method of the present invention was confirmed.

1 metal plate 2 (2A, 2B) mist jet nozzle (jet nozzle)
2a mist 21 header 3 restraint roll 4 draining spray nozzle 4a gas 5 compressed air pipe 51 supply valve 52 compressor 6 water pipe 61 supply valve 62 water tank 63 pump 7 flow controller

Claims (6)

Installed on the exit side of the soaking zone of the continuous annealing furnace,
a cooling fluid injection device having a plurality of injection nozzles for injecting mist onto both surfaces of a continuously conveyed metal plate;
At least a pair of restraint rolls restraining the metal plate from both sides in a region from a cooling start point to a cooling end point by the cooling fluid injection device ,
The apparatus for hardening a metal plate, wherein the pair of restraint rolls are arranged with their central axes shifted by 40 mm or more and 150 mm or less in the conveying direction of the metal plate . The plurality of jet nozzles according to claim 1, arranged to inject the mist onto the metal plate over the entire temperature range from the martensite transformation start temperature to the martensite transformation end temperature of the metal plate. Quenching equipment for metal plates. 3. The apparatus for hardening a metal plate according to claim 1, further comprising a draining spray nozzle downstream of an outlet of said cooling fluid injection device. In a region where the temperature of the metal plate during cooling is at least between the martensite transformation start temperature and the martensite transformation end temperature, the above constraining the metal plate from both sides by at least a pair of constraining rolls ;
The method of quenching a metal plate , wherein the pair of restraint rolls are arranged with their central axes shifted in the conveying direction of the metal plate by 40 mm or more and 150 mm or less . The method of hardening a metal plate according to claim 4, wherein the mist has a water density of 100 L/m ² ·min or more and 800 L/m ² ·min or less. A steel sheet is continuously annealed and further quenched by the method for quenching a metal sheet according to claim 4 or 5 to produce a high-strength cold-rolled steel sheet, a hot-dip galvanized steel sheet, an electro-galvanized steel sheet, or an alloyed hot-dip galvanized steel sheet. A method of manufacturing a steel plate that manufactures

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