WO2023026773A1

WO2023026773A1 - Quenching device, quenching method, and metal sheet manufacturing method

Info

Publication number: WO2023026773A1
Application number: PCT/JP2022/029364
Authority: WO
Inventors: 宗司吉本; 弘和小林
Original assignee: Ｊｆｅスチール株式会社
Priority date: 2021-08-24
Filing date: 2022-07-29
Publication date: 2023-03-02
Also published as: JPWO2023026773A1; KR20240035542A; JP7464143B2; CN117813405A

Abstract

The present invention suppresses shape variation of a metal sheet which occurs at the time of quenching.　This metal sheet quenching device (1) is for cooling a metal sheet while conveying the metal sheet and comprises a cooling device (10) for cooling the metal sheet (S) being conveyed, restraining rolls (20) for conveying the metal sheet (S) cooled by the cooling device (10) while restraining the metal sheet in a thickness direction, roll movement devices (30) for causing the restraining rolls (20) to move along the conveyance direction of the metal sheet (S), and a movement control device (40) for adjusting the positions of the restraining rolls (20) by controlling operation of the roll movement devices (30).

Description

Quenching apparatus, quenching method, and method for manufacturing metal plate

The present invention relates to a quenching apparatus, a quenching method, and a method of manufacturing a metal plate that perform annealing while continuously conveying the metal plate.

In a continuous annealing facility that performs annealing while continuously transporting a metal sheet, the metal sheet is cooled after being heated, causing a phase transformation to build up the metal sheet structure. Especially in the automobile industry, the demand for thin high-strength steel sheets (high-tensile steel) is increasing for the purpose of achieving both weight reduction and collision safety. When manufacturing high-strength steel sheets, a technique for rapidly cooling the steel sheets is important. A water quenching method is known as one of the techniques with the fastest cooling rate for a metal plate. In the water quenching method, a heated metal plate is immersed in water and at the same time cooling water is sprayed onto the metal plate from a quench nozzle provided in the water, thereby quenching the metal plate.

When the metal plate is quenched, shape defects such as warping and wavy deformation occur in the metal plate. This is due to thermal contraction of the metal plate due to rapid cooling. In particular, when the temperature of the metal plate changes from the temperature Ms at which martensitic transformation starts to the temperature Mf at which martensitic transformation ends, rapid thermal contraction and transformation expansion occur at the same time.

Therefore, conventionally, various methods have been proposed to prevent shape defects of metal plates during quenching (see Patent Documents 1 and 2, for example). In Patent Document 1, when the temperature at the Ms point where the martensitic transformation of the metal plate starts is TMs (°C) and the temperature at the Mf point where the martensitic transformation ends is TMf (°C), the temperature of the metal plate is ( A method has been proposed in which a metal plate is constrained by a pair of constraining rolls provided in a cooling liquid in the range of TMs+150) (°C) to (TMf-150) (°C).

In Patent Document 2, when performing a quenching method in which water is jetted from a plurality of water jet nozzles onto the surface of a metal plate to cool it, the metal plate is restrained by restraint rolls, and the metal plate is cooled by a cooling fluid using a movable mask. It is disclosed to control the distance between the cooling start position and the constraining roll. Furthermore, as in Patent Document 1, when the temperature at the Ms point where the martensitic transformation of the metal plate starts is TMs (° C.) and the temperature at the Mf point where the martensitic transformation ends is TMf (° C.), the metal plate is ( A technique has been proposed in which the film is passed through restraint rolls at a temperature of TMs+150) (° C.) to (TMf−150) (° C.).

Japanese Patent No. 6094722 JP 2019-90106 A

However, in the method described in Patent Document 1, the position where the temperature of the metal plate falls within the range of (TMs+150) (°C) to (TMf-150) (°C) changes depending on the manufacturing conditions of the metal plate. For this reason, the constraining rolls cannot constrain the metal plate at a position where the temperature of the metal plate is (TMs+150) (°C) to (TMf-150) (°C), which may cause variations in the shape of the metal plate. There is

In the method described in Patent Document 2, the water that collides with the movable masking falls due to gravity and interferes with the water that is jetted from the water jetting nozzle at the bottom of the movable masking, thereby destabilizing the cooling ability of the metal plate. Become. In addition, since each nozzle is masked, the cooling capacity changes stepwise (discontinuously), and as a result, the temperature of the metal plate becomes (TMs+150) (°C) to (TMf-150) (°C). The position may become unstable and the shape of the metal plate may vary.

The present invention has been made to solve such problems, by controlling the temperature of the metal plate at the position where the metal plate is restrained with high accuracy, and suppressing the variation in the shape of the metal plate that occurs during quenching. It is an object of the present invention to provide a quenching apparatus and a quenching method, and a method for manufacturing a metal plate product.

[1] A metal plate quenching apparatus that cools a metal plate while it is being conveyed, comprising: a cooling device that cools the metal plate that is being conveyed; a restraint roll, a roll moving device for moving the restraint roll along the conveying direction of the metal plate, and a movement control device for controlling the operation of the roll movement device to adjust the position of the restraint roll. Quenching equipment for metal plates.
[2] The metal plate quenching apparatus according to [1], wherein the cooling device has a plurality of nozzles for cooling the metal plate by injecting a cooling fluid.
[3] The metal plate quenching apparatus according to [1] or [2], wherein the cooling device has a cooling tank in which the metal plate is immersed and cooled.
[4] The movement control device controls the operation of the roll movement device, and positions the constraining roll so that the constraining roll constrains the metal plate at a position where the metal plate reaches a target temperature. ] to [3], a metal plate quenching apparatus.
[5] The target temperature is (TMs + 150), where TMs (°C) is the temperature at the Ms point where the martensitic transformation of the metal plate starts, and TMf (°C) is the temperature at the Mf point where the martensitic transformation ends. (° C.) to (TMf-150) (° C.).
[6] The movement control device determines the distance from the cooling start position by the cooling device to the restraint roll, the conveying speed of the metal plate, the cooling start temperature of the metal plate when the cooling is started by the cooling device, The apparatus for hardening a metal plate according to [4] or [5], wherein the position of the constraining roll is set based on the target temperature and the cooling rate of the metal plate, and the position of the constraining roll is moved to the set distance.
[7] The movement control device controls the transport speed of the metal plate to be v (mm/s), the cooling start temperature to T1 (°C), the target temperature to T2 (°C), and the cooling device to cool the metal plate. The metal plate quenching apparatus according to [6], wherein the distance d (mm) from the cooling start position to the constraining roll is determined by the formula (1), where CV (° C./s) is the speed.
d=(T1-T2)×v/CV (1)
[8] The movement control device according to [7], wherein the cooling speed CV is set as CV=α/t by a coefficient α indicating a cooling condition of the metal plate and a plate thickness t of the metal plate. metal plate quenching equipment.
[9] A method of quenching a metal plate in which the metal plate is cooled while being conveyed, wherein when the cooled metal plate is constrained in the thickness direction by constraining rolls, the metal plate is quenched at a position where the metal plate reaches a target temperature. A method of quenching a metal plate, wherein the constraining rolls are moved along the conveying direction so as to constrain the plate.
[10] The target temperature is (TMs + 150) where TMs (°C) is the temperature at the Ms point where the martensitic transformation of the metal plate starts, and TMf (°C) is the temperature at the Mf point where the martensitic transformation ends. (° C.) to (TMf-150) (° C.).
[11] The movement of the constraining roll is performed at the cooling start position based on the conveying speed of the metal plate, the cooling start temperature of the metal plate at the start of cooling, the target temperature, and the cooling speed of the metal plate. to the constraining roll, and moving the constraining roll to the set distance.
[12] The distance from the cooling start position to the constraining roll is v (mm/s) as the conveying speed of the metal plate, T1 (°C) as the cooling start temperature, T2 (°C) as the target temperature, and T2 (°C) as the target temperature. The method of quenching a metal plate according to [11], wherein the distance d (mm) from the cooling start position to the constraining roll is obtained by formula (1), where CV (° C./s) is the cooling rate of the plate.
d=(T1-T2)×v/CV (1)
[13] The method of hardening a metal plate according to [12], wherein the cooling rate CV is set as CV=α/t by a coefficient α indicating the cooling condition of the metal plate and a thickness t of the metal plate.
[14] A method for producing a high-strength cold-rolled steel sheet, using the metal plate quenching method according to any one of [9] to [13].
[15] A method for producing a high-strength steel sheet, wherein the high-strength steel sheet obtained by the method described in [14] is subjected to any one of hot-dip galvanizing treatment, electro-galvanizing treatment, or galvannealing treatment.

According to the present invention, when the metal plate is quenched, the position of the constraining roll is adjusted along the conveying direction of the metal plate according to the temperature of the metal plate, thereby controlling the distance from the cooling start position to the constraining roll. , it is possible to suppress the variation in the shape of the metal plate that occurs during quenching.

It is a mimetic diagram showing a quenching device concerning an embodiment of the present invention. It is a schematic diagram which shows an example of the definition of the curvature amount of a metal plate. It is a graph which shows the relationship between the conveyance speed and target temperature in the example of this invention. It is a graph which shows the relationship between the conveyance speed and the curvature amount of a metal plate in the example of this invention. 7 is a graph showing the relationship between the conveying speed and the target temperature in Comparative Example 1. FIG. 7 is a graph showing the relationship between the conveying speed and the warp amount of the metal plate in Comparative Example 1. FIG. 9 is a graph showing the relationship between the conveying speed and the target temperature in Comparative Example 2. FIG. 9 is a graph showing the relationship between the conveying speed and the amount of warpage of the metal plate in Comparative Example 2. FIG. It is a figure explaining a constraining roll and movement of a nozzle in other examples of a quenching device concerning an embodiment of the present invention.

An embodiment of the present invention will be described based on the drawings. FIG. 1 is a schematic diagram showing a hardening apparatus according to an embodiment of the present invention. The quenching apparatus 1 shown in FIG. 1 is for quenching a steel material, for example, as a metal sheet S, and is applied to a cooling facility provided on the delivery side of a soaking zone of a continuous annealing furnace. A hardening apparatus 1 for a metal plate S shown in FIG. 1 includes a cooling device 10 that cools the metal plate S, and restraint rolls 20 that restrain the cooled metal plate S in the thickness direction.

The cooling device 10 cools the metal plate S using the cooling fluid CF. and a plurality of nozzles 12 for jetting. Water is stored in the cooling tank 11 as a cooling fluid CF, and for example, the metal plate S is immersed from the upper surface of the cooling tank 11 in the conveying direction BD. A sink roll 2 for changing the conveying direction of the metal plate S is installed in the cooling tank 11 .

The plurality of nozzles 12 are, for example, quench nozzles or the like, and are installed on both sides of the metal plate S along the conveying direction of the metal plate S. Therefore, the metal plate S is cooled by the cooling fluid CF in the cooling tank 11 and the cooling fluid CF jetted from the plurality of nozzles 12 . By cooling the metal plate S using both the cooling bath 11 and the plurality of nozzles 12 in this manner, the boiling state of the surface of the metal plate S can be stabilized, and uniform shape control can be performed.

Although the case of water quenching using water as the cooling fluid CF is exemplified, oil cooling using oil as the cooling fluid CF may be used. In addition, FIG. 1 illustrates a case where a plurality of nozzles 12 are installed in the cooling bath 11, but the cooling method is limited to this as long as it is a method that can cool the metal plate S within a desired temperature range. not. For example, the metal plate S may be cooled only by the cooling bath 11 or may be cooled only by the plurality of nozzles 12 .

When installing the nozzle 12 in the cooling bath 11, the distance between the metal plate S and the nozzle 12 is important in rapid cooling by liquid quenching. It is desirable to install the nozzle 12 close to the metal plate S in order to perform rapid cooling by breaking the vapor film generated by the boiling phenomenon with the liquid jet. The distance between the tip of the nozzle 12 and the metal plate S is preferably 10 mm or more and 150 mm or less. If it is less than 10 mm, the deformed and fluttering metal plate S may come into contact with the nozzle 12 . On the other hand, if it exceeds 150 mm, the effect of destroying the vapor film becomes weak, and it may become difficult to ensure sufficient cooling capacity.

The constraining rolls 20 constrain the metal plate S cooled by the cooling device 10 in the thickness direction, and are installed on both sides of the metal plate S in the cooling tank 11 respectively. In FIG. 1, a pair of restraint rolls 20 are installed so as to face each other, but they may be installed at positions shifted along the conveying direction as long as they restrain. Moreover, although FIG. 1 illustrates a case where a pair of restraint rolls 20 is installed, a plurality of pairs of restraint rolls 20 may be installed along the transport direction.

Also, the roll diameter of the constraining roll 20 is preferably 50 mm or more and 300 mm or less from the correlation between the roll rigidity and the deflection caused by the constraining stress. The material of the constraining roll 20 is not limited. When a general steel roll is used as the restraining roll 20 and the roll diameter is less than 50 mm, the roll rigidity is insufficient, and it is difficult to apply a uniform restraining force to the metal plate S due to deflection. and there is a possibility of damage. In addition, if the roll diameter is larger than 300 mm, the section in which the jet from the nozzle 12 does not reach the metal plate S becomes longer, and the steam film may not be sufficiently destroyed, resulting in a decrease in cooling capacity.

The constraining roll 20 is installed movably along the conveying direction of the metal plate S. Here, the conveying direction refers to the direction in which the metal plate S is conveyed. Specifically, the hardening apparatus 1 for the metal plate S includes a roll moving device 30 that moves the constraining rolls 20 and a movement control device 40 that controls the movement of the constraining rolls 20 . The roll moving device 30 includes a known driving means such as a motor, and moves the restraint roll 20 along the conveying direction of the metal plate S in the conveying direction BD of the metal plate S or in the direction opposite to the conveying direction BD. configured to move. Specifically, the roll moving device 30 is suitable by combining mechanical parts such as a power jack, a screw type lifting device with a screw mechanism or a gear mechanism, and a linear motion guide (LM guide) that uses rolling and has low resistance. can be manufactured to FIG. 1 shows an example in which the roll moving device 30 is configured by a screw-type lifting device. A restraint roll 20 is rotatably attached to one end of the L-shaped arm 31 . A threaded portion 32 , another threaded portion that engages with the threaded portion 32 , and driving means (not shown) for driving the other threaded portion are provided on the other end side of the arm 31 . The driving means are fixed to a fixed part (not shown). Therefore, when the torque generated by the driving means rotates the other threaded portion, the arm 31 moves in a direction parallel to the conveying direction BD.

If the drive means described above is immersed in liquid, maintenance of the drive means may become difficult. Therefore, it is preferable that the drive means be installed above the liquid surface of the cooling bath 11 . Moreover, it is preferable that the drive means be installed in a space shielded from the inside of the furnace, which becomes a high temperature.

The roll moving device 30 may have a function of moving the restraint roll 20 in the thickness direction of the metal plate S to restrain and release the restraint of the metal plate S. Any method can be used as long as it can be moved, but an electric type is more preferable in consideration of responsiveness.

The movement control device 40 consists of hardware resources such as computers, and controls movement of the restraint roll 20 . In particular, the movement control device 40 controls the operation of the roll movement device 30 and positions the restraint roll 20 so that the metal plate S is restrained at the position RP where the target temperature is reached. Here, the target temperature is defined as (TMs+150)( ° C.) to (TMf-150) (° C.). As a result, the deformation of the metal plate S can be restrained by the restraining rolls 20 at the position where the metal plate S undergoes rapid thermal contraction and transformation expansion at the same time, and deformation of the metal plate S during quenching can be restrained. can.

The movement control device 40 calculates the distance d from the cooling start position SP of the metal plate S by the cooling fluid CF to the position RP at which the restraint roll 20 reaches the target temperature, and moves the restraint roll 20 based on the calculated distance d. move. At this time, the movement control device 40 controls the conveying speed v (mm/s) of the metal plate S, the cooling start temperature T1 (°C), the target temperature T2 (°C) to be restrained by the restraining rolls 20, the metal plate S by the cooling device 10 The distance d is calculated using the cooling rate CV (°C/s) of . Here, the cooling start temperature T1 is the temperature of the metal plate S immediately before the cooling start position SP where cooling of the metal plate S is started by the cooling fluid CF. For example, the temperature immediately before reaching the cooling start position SP can be calculated based on the cooling state of the metal sheet S up to the cooling start position SP and the hardening device 1 . Specifically, the temperature of the metal sheet S is measured with a non-contact type thermometer on the delivery side of the soaking zone of the continuous annealing furnace. Then, the temperature of the metal sheet S immediately before or at the time of reaching the cooling start position SP can be calculated based on the temperature and the amount of temperature decrease due to the natural cooling of the metal sheet S until it reaches the quenching device 1. can. The amount of temperature decrease due to the natural cooling of the metal plate S described above can be obtained in advance by experiments. The above parameters may be obtained sequentially from the set values of the process computer or actual operation values, or may be measured using a speed sensor, temperature sensor, or the like.

Specifically, the relationship between the distance d and the cooling rate CV (°C/s) is expressed by the following formula (1).

CV = (T1-T2)/(d/v)
d=(T1−T2)×v/CV (1)

The cooling rate CV (°C/s) is determined by the nozzle shape or the coefficient α (°C mm/s) indicating the cooling conditions such as the type, temperature, and injection amount of the cooling fluid CF to be jetted, and the thickness of the metal plate S. It can be represented by the following formula (3) using t.

CV = α/t (2)

By substituting the formula (2) into the formula (1), the distance d can be expressed by the following formula (3).

　　　d=(T1-T2)×v×t/α (3)

The movement control device 40 stores the cooling rate CV (°C/s) or α (°C·mm/s) obtained in advance through experiments, numerical analysis, or the like. Then, the movement control device 40 obtains the distance d using the formula (1) or the formula (3), and moves the restraint roll 20 so as to restrain the metal plate S at the position of the obtained distance d. The cooling rate CV is a value determined according to the plate thickness, etc. For a plate thickness of 1 to 2 mm, the cooling rate CV = 1000 to 2000 (°C/s), and α = 500 to 2000 (°C mm/s). is. Therefore, in the movement control device 40, the cooling rate CV may be set to 1500 (°C/s), which is the middle of the above range. In this case, α may be treated as an intermediate value of 1250 (°C·mm/s). In this way, the cooling condition α obtained by the above-described cooling rate CV, plate thickness t, and equation (2) may be set.

A quenching method and a method for manufacturing a metal plate S according to the present invention will be described with reference to FIG. First, the metal plate S is cooled by the cooling device 10 while being conveyed, and the metal plate S is quenched. At this time, the restraint roll 20 moves along the transport direction so as to restrain the thickness direction of the metal plate S, which is at the target temperature T2 at the position RP. At this time, in the movement control device 40, the distance d is calculated using the above formula (1) or formula (3), and the restraint roll 20 is moved so as to restrain the metal plate S at the position of the calculated distance d. do. It should be noted that the movement of the restraining rolls 20 can be performed sequentially even while the metal plate S is being quenched. For example, the movement control device 40 may calculate the distance d and move the restraint roll 20 at the timing when the conveying speed v is changed.

The transport speed of the metal plate S fluctuates even for one metal plate S (within one coil). Therefore, if the metal plate S can be moved in the conveying direction or in the opposite direction while being restrained by the restraining rolls 20, the yield due to the defective shape of the decelerating portions such as the front end and the tail end of the metal plate S can be improved. preferable. Alternatively, the movement control device 40 may calculate the distance d and move the restraint roll 20 every set period.

The moving distance of the constraining roll 20 for adjusting the constraining roll 20 to the constraining position RP of the metal plate S based on the distance d can be realistically estimated to be approximately 10 mm to 150 mm. As shown in FIG. 1, when the nozzles 12 are installed in the cooling tank 11, the restraint roll 20 is moved up and down between the nozzles 12 while the distance between the nozzles 12 is widened in advance to about 10 mm to 150 mm. good. Further, for example, rapid cooling by a liquid jet has a cooling capacity of about 1000° C./sec, and when the running speed of the metal plate S is 60 m/min (=1000 mm/sec), the temperature changes by about 100° C. at a distance of 100 mm. . In other words, if the constraining roll 20 can be raised and lowered in the range of 10 mm to 150 mm, the temperature of the constrained metal plate S can be adjusted by about 10° C. to 150° C., and the movement distance of the constraining roll 20 is practically This is a sufficient control adjustment range.

Here, a case where the restraint roll 20 is moved more than the above example will be described. When the composition, thickness, transport speed, etc. of the metal plate S change significantly, it is necessary to move the restraint roll 20 by 150 mm or more in order to position the restraint roll 20 at the restraint position RP of the metal plate S. . A configuration for moving the restraint roll 20 by 150 mm or more will be described. FIG. 9 is a diagram showing another example of the hardening device according to the embodiment of the present invention. A hardening device 50 shown in FIG. 9 includes a nozzle moving device 60 for moving the nozzle 12 in addition to the roll moving device 30 for moving the constraining roll 20 . The nozzle moving devices 60 are arranged on both sides of the metal plate S, respectively, as shown in FIG. 9(A). The nozzle moving device 60 is configured to move the nozzle 12 along the metal plate S and move the nozzle 12 toward and away from the metal plate S. As shown in FIG. In addition, in the example shown in FIG. 9, the restraint rolls 20 on both sides of the metal plate S are offset in the vertical direction.

As shown in FIG. 9 , the nozzle moving device 60 includes an elevating device 62 that moves the cooling pipes 61 communicating with the respective nozzles 12 in the vertical direction of the cooling device 10 , and the elevating device 62 with respect to the metal plate S. and a slider 63 for approaching and separating. The lifting device 62 is configured to be able to lift and lower each of the plurality of cooling pipes 61 independently of each other. Incidentally, the lifting device 62 and the slider 63 may be conventionally known ones. again. A control device (not shown) for controlling the driving of the lifting device 62 and the slider 63 is provided.

Next, the action of the hardening device 50 shown in FIG. 9 will be described. When the constraining roll 20 is moved upward from the position shown in FIG. 9A, the constraining roll 20 and the nozzles 12 positioned above interfere with each other. Therefore, first, the nozzle 12 is separated from the metal plate S by the slider 63 in the width direction of the cooling device 10 (horizontal direction in FIG. 9). That is, the nozzle 12 is retracted from the restraint roll 20 . The distance between the metal plate S and the tip of the nozzle 12 after separating the nozzle 12 from the metal plate S is set so that the restraint roll 20 and the tip of the nozzle 12 do not contact each other. In that state, the restraint roll 20 is moved upward or downward. FIG. 9 illustrates the case of moving upward. That is, the restraint roll 20 is moved to the position RP suitable for the target temperature T2 of the metal plate S. FIG. 9B shows that state.

In addition, in the state shown in FIG. 9(B), the restraint roll 20 and the nozzle 12 are adjacent to each other in the width direction of the cooling bath 11 . Therefore, the nozzles 12 that are adjacent to the restraining roll 20 in the width direction are retracted and moved to the lower side of the restraining roll 20 by the lifting device 62 as shown in FIG. 9(B). As a result, the constraining rolls 20 and the nozzles 12 do not interfere with each other in both the vertical direction and the width direction. FIG. 9C shows that state. Next, each nozzle 12 is brought close to the metal plate S by the slider 63, and the distance between them is set to the preset distance and maintained. Thus, the movement of the restraint roll 20 is completed. FIG. 9(D) shows that state.

After reaching the state shown in FIG. 9(D), the distance between the nozzles 12 is widened to about 10 mm to 150 mm in substantially the same manner as the example shown in FIG. , the restraint roll 20 may be moved to adjust to the above position RP. Further, if the cooling capacity permits, the space between the metal plate S and the nozzle 12 may be widened so that the restraint roll 20 can move 150 mm or more.

According to the above-described embodiment, the restraint roll 20 is installed movably along the conveying direction, thereby controlling the distance from the cooling start position to the restraint roll 20, and regardless of the manufacturing conditions of the metal plate S, the target The metal plate S at temperature T2 can be constrained by the constraining rolls 20 . As a result, in the continuous annealing equipment, it is possible to suppress shape defects of the metal sheet S due to manufacturing conditions of the metal sheet S that occur during quenching.

That is, the temperature of the metal plate S conveyed to the hardening apparatus 1 varies depending on the manufacturing conditions of the metal plate, such as the conveying speed v, the cooling start temperature T1 of the metal plate S, and the thickness t of the metal plate S, for example. Therefore, if the distance d is set constant regardless of the manufacturing conditions, the temperature of the metal sheet S when it reaches the restraining rolls 20 also varies.

In order to solve this problem, it was found that it is effective to change the position of the constraining rolls 20 in order to accurately control the shape at the optimum temperature position that varies depending on the manufacturing conditions. By moving the restraining rolls 20 themselves, the metal plate S can be restrained within the target temperature range even if the manufacturing conditions change, without incurring instability in the cooling mode.

In particular, it is possible 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 metal plate S. Therefore, when the metal plate S is a high-strength steel plate (high-tensile steel), the effect of suppressing deformation is particularly large. 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 2000 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.

In addition, as a specific example of the composition of the high-strength steel sheet, in mass%, C is 0.04% or more and 0.35% 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. In addition, the metal plate S is not limited to a steel plate, and may be a metal plate other than a steel plate.

An example of the present invention will be described. As an example of the present invention, a high-strength cold-rolled steel sheet having a thickness t of 1.0 mm and a width of 1000 mm and a tensile strength of 1470 MPa was quenched using the quenching apparatus 1 according to the embodiment of the present invention. . The composition of the high-strength cold-rolled steel sheet with a tensile strength of 1470 MPa is 0.20% C, 1.0% Si, 2.3% Mn, 0.005% P, and 0 S in mass%. .002%. The temperature TMs at the Ms point of the high-strength cold-rolled steel sheet is 300°C, and the temperature TMf at the Mf point is 250°C. Therefore, the target temperature T2 when passing through the restraining rolls 20 may be set in the range of 450.degree. C. to 100.degree. Also, the cooling start temperature T1 was set at 800°C, and the target temperature T2 was set at 400°C. The temperature of the cooling fluid CF was set at 30° C., and the cooling rate CV was set at 1500 (° C./s).

As a change in the manufacturing conditions, the conveying speed v was changed between 1000 and 3000 mm/s, and the distance d (mm) was controlled at d = 267 to 800 m according to the change in the conveying speed v based on the formula (1). . Ten sheets of the cooled steel sheet were sampled every 100 m in the longitudinal direction (that is, the same direction as the conveying direction of the steel sheet), and the amount of warpage of each steel sheet was investigated. FIG. 2 is a schematic diagram showing an example of the definition of the amount of warpage. As shown in FIG. 2, the amount of warpage was defined as the height from the contact surface to the highest point when the steel plate was placed on a horizontal surface.

FIG. 3 is a graph showing the relationship between the conveying speed v and the target temperature in the example of the present invention, and FIG. be. As shown in FIG. 3, even if the conveying speed v changes, the temperature (° C.) when the constraining rolls 20 pass can be kept to the target value by moving the constraining rolls 20 according to the conveying speed v and changing the distance d. Everything could be controlled at a temperature of 400±25°C. As a result, as shown in FIG. 4, the amount of warpage of all the steel sheets was reduced to 10 mm or less. As a result, the variation in the amount of warpage, that is, the difference between the maximum value and the minimum value was suppressed to 4.2 mm.

5 is a graph showing the relationship between the conveying speed v and the target temperature in Comparative Example 1, and FIG. 6 is a graph showing the relationship between the conveying speed v and the warp amount of the steel plate as the metal plate S in Comparative Example 1. be. As Comparative Example 1, a quenching apparatus in which a constraining roll 20 was fixed as in Patent Document 1 was used, and other conditions were the same as those of the above-described example of the present invention. In Comparative Example 1, the distance d (mm) from the cooling start position to the constraining roll 20 was constant at d=400 mm.

In Comparative Example 1, as shown in FIG. 5, the temperature (°C) at the time of passage through the restraint rolls greatly changed depending on the transport speed v (mm/s), and could not be controlled. Therefore, under conditions other than v=1000 mm/s and v=1500 mm/s, the temperature (° C.) at the time of passage through the restraint roll 20 was out of the range of 450° C. to 100° C. As a result, as shown in FIG. 6, under conditions other than v=1000 mm/s and v=1500 mm/s, the amount of warpage of the steel sheets was all 10 mm or more, and the effect of suppressing deformation was insufficient. As a result, the variation, which is the difference between the maximum value and the minimum value of the amount of warpage, increased to 10.3 mm.

7 is a graph showing the relationship between the conveying speed v and the target temperature in Comparative Example 2, and FIG. 8 is a graph showing the relationship between the conveying speed v and the warp amount of the steel plate as the metal plate S in Comparative Example 2. be. As Comparative Example 2, as shown in Patent Document 2, the movable masking was moved while the restraint roll 20 was fixed, and the distance d was controlled by the cooling start position. Other conditions were the same as in the present invention example to produce the above high-strength cold-rolled steel sheets.

As shown in FIG. 7, in Comparative Example 2, the temperature (° C.) when passing through the restraining rolls 20 changes greatly regardless of the steel sheet manufacturing conditions such as the conveying speed v (mm/s), and cannot be controlled. I didn't. Therefore, under all conditions, the temperature (°C) at the time of passage through the constraining rolls was out of the range of 450°C to 100°C. Then, as shown in FIG. 8, the amount of warpage of the steel plate was 10 mm or more, and the effect of suppressing deformation was insufficient. As a result, the variation in the amount of warpage (the difference between the maximum value and the minimum value) increased to 9.2 mm.

It should be noted that the embodiments of the present invention are not limited to the above embodiments, and various modifications can be made. For example, in the above embodiment, the target temperature T2 is (TMs+150) (° C.) to (TMf−150) (° C.), but is not limited to this. From the point of view of post-process processing and ensuring flexibility of operation, for example, if there is no variation in the shape of the metal plate S such as the amount of warpage, the target temperature T2 is set to (TMs + 150) (°C) ~ ( It may not be limited to TMf-150) (°C).

In this case, the target temperature T2 is determined in advance in consideration of the expected shape (for example, the amount of warpage) while keeping in mind the degree of freedom of processing and operation in the post-process. The position adjustment controls the distance d from the cooling start position to the restraint rolls 20 . Then, the temperature of the metal plate S when passing through the restraining rolls 20 is set to a predetermined temperature T2, and the shape (for example, the amount of warp) of the metal plate S is approximately the same, for example, the amount of warp defined in FIG. The variation should be within 4 mm.

Furthermore, the number of the restraint rolls 20 is not limited to one pair, and may be provided in a plurality of pairs or a plurality of rolls. In that case, the position of the entire constraining roll pair may be controlled collectively, or a mechanism for controlling the position and opening/closing of each of a plurality of constraining rolls may be employed.

1 Metal plate quenching device 10 Cooling device 11 Cooling tank 12 Nozzle 20 Restraining roll 30 Roll moving device 40 Movement control device BD Conveying direction CF Cooling fluid S Metal plate

Claims

A metal plate quenching apparatus that cools a metal plate while conveying it,
a cooling device for cooling the metal plate to be conveyed;
a constraining roll that conveys the metal plate cooled by the cooling device while constraining it in the thickness direction;
a roll moving device for moving the restraint roll along the conveying direction of the metal plate;
a movement control device that controls the operation of the roll movement device to adjust the position of the restraint roll;
A metal plate quenching device.
The apparatus for hardening a metal plate according to claim 1, wherein the cooling device has a plurality of nozzles for cooling the metal plate by injecting a cooling fluid.
The apparatus for quenching a metal plate according to claim 1 or 2, wherein the cooling device has a cooling tank in which the metal plate is immersed and cooled.
4. The movement control device controls the operation of the roll movement device, and positions the constraining roll so that the constraining roll constrains the metal plate at a position where the metal plate reaches the target temperature. The apparatus for quenching a metal plate according to any one of Claims 1 to 3.
The target temperature is (TMs + 150) (°C), where TMs (°C) is the temperature at the Ms point where the martensitic transformation of the metal plate starts, and TMf (°C) is the temperature at the Mf point where the martensitic transformation ends. 5. The apparatus for quenching a metal plate according to claim 4, wherein the temperature is set within a temperature range of ~(TMf-150)(°C).
The movement control device controls the distance from the cooling start position of the cooling device to the constraining roll, the conveying speed of the metal plate, the cooling start temperature of the metal plate when cooling is started by the cooling device, and the target temperature. 6. The apparatus for hardening a metal plate according to claim 4 or 5, wherein the position of the restraint roll is set based on the cooling rate of the metal plate, and the position of the restraint roll is moved so as to reach the set distance.
The movement control device sets the conveying speed of the metal plate to v (mm/s), the cooling start temperature to T1 (°C), the target temperature to T2 (°C), and the cooling speed of the metal plate by the cooling device to CV. 7. The apparatus for quenching a metal plate according to claim 6, wherein the distance d (mm) from the cooling start position to the restraint roll is obtained by formula (1), where (° C./s).
d=(T1-T2)×v/CV (1)
8. The metal plate according to claim 7, wherein the cooling rate CV is set to CV=α/t by the thickness t of the metal plate and the coefficient α indicating the cooling condition of the metal plate in the movement control device. quenching equipment.
A metal plate quenching method for cooling while conveying the metal plate,
When the cooled metal plate is constrained in the thickness direction by the constraining rolls, the constraining rolls are moved along the conveying direction of the metal plate so as to constrain the metal plate at a position where the metal plate is at the target temperature. A method of quenching a moving metal plate.
The target temperature is (TMs + 150) (°C), where TMs (°C) is the temperature at the Ms point where the martensitic transformation of the metal plate starts, and TMf (°C) is the temperature at the Mf point where the martensitic transformation ends. 10. The method of quenching a metal plate according to claim 9, wherein the temperature is set within a range of ~(TMf-150)(°C).
The movement of the restraint roll is performed from the cooling start position to the restraint roll based on the conveying speed of the metal plate, the cooling start temperature of the metal plate at the start of cooling, the target temperature, and the cooling speed of the metal plate. Set the distance to the roll,
11. The method of quenching a metal plate according to claim 9 or 10, wherein the quenching is performed by moving the constraining rolls so as to achieve a set distance.
The distance from the cooling start position to the restraint roll is v (mm/s) for the conveying speed of the metal plate, T1 (° C.) for the cooling start temperature, T2 (° C.) for the target temperature, and cooling of the metal plate. 12. The method of quenching a metal plate according to claim 11, wherein the distance d (mm) from the cooling start position to the restraint roll is obtained by formula (1), where CV (° C./s) is the speed.
d=(T1-T2)×v/CV (1)
The method of quenching a metal plate according to claim 12, wherein the cooling rate CV is set as CV = α/t by a coefficient α indicating the cooling condition of the metal plate and the plate thickness t of the metal plate.
A method for producing a high-strength cold-rolled steel sheet using the method for quenching a metal plate according to any one of claims 9 to 13.
A method for producing a high-strength steel sheet, wherein the high-strength steel sheet obtained by the method according to claim 14 is subjected to hot-dip galvanizing treatment, electro-galvanizing treatment, or hot-dip alloying galvanizing treatment.