CN117813405A

CN117813405A - Quenching device and quenching method, and method for manufacturing metal plate

Info

Publication number: CN117813405A
Application number: CN202280055945.6A
Authority: CN
Inventors: 吉本宗司; 小林弘和
Original assignee: JFE Steel Corp
Current assignee: JFE Steel Corp
Priority date: 2021-08-24
Filing date: 2022-07-29
Publication date: 2024-04-02
Also published as: JP7464143B2; WO2023026773A1; KR20240035542A; JPWO2023026773A1; EP4372105A1

Abstract

The invention suppresses deviation of the shape of a metal plate generated during quenching. A quenching apparatus (1) for a metal sheet, which cools the metal sheet while conveying the metal sheet, the quenching apparatus (1) for a metal sheet comprising: a cooling device (10) for cooling the conveyed metal sheet (S); a constraining roll (20) that conveys the metal sheet (S) cooled by the cooling device (10) while constraining the metal sheet in the thickness direction; a roller moving device (30) that moves the constraining roller (20) along the conveying direction of the metal sheet (S); and a movement control device (40) that controls the operation of the roller movement device (30) to adjust the position of the constraining roller (20).

Description

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

Technical Field

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

In a continuous annealing apparatus that continuously conveys and anneals a metal plate, the metal plate is cooled after being heated to undergo a phase change, thereby shaping a metal plate structure. In particular, in the automotive industry, there is an increasing demand for a high-tensile steel sheet (high-tensile steel) that is thinned for the purpose of achieving both weight saving and collision safety of a vehicle body. In the production of high-tensile steel sheets, a technique for rapidly cooling the steel sheets is important. As one of the techniques for maximizing the cooling rate of a metal plate, a water quenching method is known. In the water quenching method, the metal sheet is quenched by spraying cooling water onto the metal sheet by a quenching nozzle provided in water, simultaneously with immersing the heated metal sheet in water.

During quenching of the metal plate, shape defects such as warpage and wavy deformation occur in the metal plate. The reasons for the above are thermal shrinkage of the metal plate caused by quenching, and the like. In particular, when the temperature of the metal plate is changed from the temperature Ms at which the martensitic transformation starts to the temperature Mf at which the martensitic transformation ends, rapid thermal contraction and phase change expansion (transformation expansion) occur simultaneously.

Accordingly, various methods have been proposed to prevent the shape failure of the metal plate during quenching (for example, see patent documents 1 and 2). Patent document 1 proposes the following method: when the temperature of the Ms point at which the martensitic transformation of the metal plate starts is TMs (DEG C) and the temperature of the Mf point at which the martensitic transformation ends is TMf (DEG C), the metal plate is restrained by a pair of restraining rolls provided in a cooling liquid in a range of the temperature of the metal plate from (TMs+150) (DEGC) to (TMf-150) (DEGC).

Patent document 2 discloses a method of quenching a metal plate by spraying water from a plurality of water spray nozzles onto the surface of the metal plate, wherein a distance between a cooling start position of the metal plate by a cooling fluid and a constraining roll is controlled by a movable masking section (movable masking) while constraining the metal plate by the constraining roll. In addition, as in patent document 1, the following method is proposed: when TMs (DEG C) is the temperature of the Ms point at which the martensitic transformation of the metal sheet starts and TMf (DEG C) is the temperature of the Mf point at which the martensitic transformation ends, the metal sheet is passed through the constraining rolls at temperatures of (TMs+150) (DEGC) to (TMf-150) (DEGC).

Prior art literature

Patent literature

Patent document 1: japanese patent No. 6094722

Patent document 2: japanese patent application laid-open No. 2019-90106

Disclosure of Invention

Problems to be solved by the invention

However, in the method described in patent document 1, the position where the temperature of the metal plate is in the range of (tms+150) (°c) to (TMf-150) (°c) varies depending on the manufacturing conditions of the metal plate. Therefore, there is a possibility that the restraining roller cannot restrain the metal plate and the shape of the metal plate may deviate at the position where the temperature of the metal plate becomes (tms+150) (°c) to (TMf-150) (°c).

In the method described in patent document 2, water that collides with the movable shielding portion falls by gravity and interferes with water ejected from the water ejection nozzle in the lower portion of the movable shielding portion, and the cooling ability of the metal plate becomes unstable. Further, since each nozzle is shielded, the cooling capacity is changed stepwise (discontinuously), and as a result, the position where the temperature of the metal plate becomes (tms+150) (°c) to (TMf-150) (°c) becomes unstable, and there is a possibility that the shape of the metal plate may be deviated.

The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a quenching apparatus and a quenching method capable of controlling the temperature of a metal plate at a position where the metal plate is restrained with high accuracy and suppressing a deviation in the shape of the metal plate generated during quenching, and a method for manufacturing a metal plate product.

Means for solving the problems

[1] A quenching apparatus for a metal plate, which cools a metal plate while conveying the metal plate, the quenching apparatus comprising: a cooling device for cooling the conveyed metal plate; a constraining roll for transporting the metal plate cooled by the cooling device while constraining the metal plate in a thickness direction; a roller moving device that moves the constraining roller in a conveying direction of the metal plate; and a movement control device that controls the operation of the roller movement device to adjust the position of the constraining roller.

[2] The apparatus for quenching a metal sheet according to [1], wherein the cooling device has a plurality of nozzles for spraying a cooling fluid onto the metal sheet to cool the metal sheet.

[3] The quenching apparatus for a metal sheet according to [1] or [2], wherein the cooling apparatus has a cooling tank for immersing and cooling the metal sheet.

[4] The quenching apparatus for a metal sheet according to any one of [1] to [3], wherein the movement control means controls an operation of the roller moving means to position the constraining rollers so that the constraining rollers constrain the metal sheet at a position where the metal sheet has reached a target temperature.

[5] The apparatus for quenching a metal sheet according to [4], wherein when the temperature of the Ms point at which the martensitic transformation of the metal sheet starts is TMs (. Degree. C.) and the temperature of the Mf point at which the martensitic transformation ends is TMf (. Degree. C.) the target temperature is set within a temperature range of (TMs+150) (. Degree. C.) to (TMf-150) (. Degree. C.).

[6] The quenching apparatus for a metal sheet according to [4] or [5], wherein the movement control device sets a distance from a cooling start position by the cooling device to the constraining rolls based on a transport speed of the metal sheet, a cooling start temperature of the metal sheet at a start of cooling by the cooling device, the target temperature, and a cooling speed of the metal sheet, and moves the positions of the constraining rolls so as to be the set distance.

[7] The quenching apparatus for a metal sheet according to [6], wherein in the movement control apparatus, when v (mm/s) is the transport speed of the metal sheet, T1 (DEG C) is the cooling start temperature, T2 (DEG C) is the target temperature, CV (DEG C/s) is the cooling speed of the metal sheet by the cooling apparatus, and d (mm) is the distance from the cooling start position to the constraining rolls is obtained by the formula (1).

d＝(T1-T2)×v/CV (1)

[8] The quenching apparatus for a metal sheet according to [7], wherein in the movement control apparatus, the cooling rate CV is set so that cv=α/t based on a coefficient α indicating a cooling condition of the metal sheet and a plate thickness t of the metal sheet.

[9] A method for quenching a metal sheet, which is a method for quenching a metal sheet that cools the metal sheet while conveying the metal sheet, wherein, when the cooled metal sheet is restrained in the thickness direction by a restraining roller, the restraining roller is moved in the conveying direction so as to restrain the metal sheet at a position where the metal sheet reaches a target temperature.

[10] The method for quenching a metal sheet according to [9], wherein when the temperature of the Ms point at which the martensitic transformation of the metal sheet starts is TMs (. Degree. C.) and the temperature of the Mf point at which the martensitic transformation ends is TMf (. Degree. C.) the target temperature is set within the temperature ranges of (TMs+150) (. Degree. C.) to (TMf-150) (. Degree. C.).

[11] The quenching method of a metal sheet as described in [9] or [10], wherein the movement of the aforementioned constraining rolls is performed by: the distance from the cooling start position to the constraining rolls is set based on the transport speed of the metal plates, the cooling start temperature of the metal plates at the start of cooling, the target temperature, and the cooling speed of the metal plates, and the constraining rolls are moved so as to be the set distance.

[12] The method for quenching a metal sheet according to [11], wherein, regarding the distance from the cooling start position to the constraining rolls, the distance d (mm) from the cooling start position to the constraining rolls is obtained by the formula (1) when v (mm/s) is the conveying speed of the metal sheet, T1 (. Degree.C.) is the cooling start temperature, T2 (. Degree.C.) is the target temperature, and CV (. Degree.C./s) is the cooling speed of the metal sheet.

d＝(T1-T2)×v/CV (1)

[13] The method for quenching a metal sheet according to [12], wherein the cooling rate CV is set so that CV=α/t, based on a coefficient α representing a cooling condition of the metal sheet and a plate thickness t of the metal sheet.

[14] A method for producing a high-strength cold-rolled steel sheet by using the method for quenching a metal sheet 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 of [14] is subjected to any one of a hot dip galvanization treatment, an electrogalvanizing treatment, and an alloying hot dip galvanization treatment.

Effects of the invention

According to the present invention, when the metal plate is quenched, the position of the constraining rolls is adjusted along the conveying direction of the metal plate in accordance with the temperature of the metal plate, so that the distance from the cooling start position to the constraining rolls can be controlled, and the variation in the shape of the metal plate caused during quenching can be suppressed.

Drawings

Fig. 1 is a schematic view showing a quenching apparatus according to an embodiment of the present invention.

Fig. 2 is a schematic diagram showing an example of definition of the warp amount of the metal plate.

Fig. 3 is a graph showing a relationship between a conveyance speed and a target temperature in the example of the present invention.

Fig. 4 is a graph showing a relationship between a conveying speed and a warp amount of a metal plate in the example of the present invention.

Fig. 5 is a graph showing a relationship between the conveyance speed and the target temperature in comparative example 1.

Fig. 6 is a graph showing a relationship between the conveying speed and the warpage amount of the metal plate in comparative example 1.

Fig. 7 is a graph showing a relationship between the conveyance speed and the target temperature in comparative example 2.

Fig. 8 is a graph showing a relationship between the conveying speed and the warpage amount of the metal plate in comparative example 2.

Fig. 9 is a diagram illustrating movement of a constraining roll and a nozzle in another example of a quenching apparatus according to an embodiment of the present invention.

Detailed Description

Embodiments of the present invention will be described based on the drawings. Fig. 1 is a schematic view showing a quenching apparatus according to an embodiment of the present invention. The quenching apparatus 1 of fig. 1 is an apparatus for quenching steel, for example, as the metal sheet S, and is suitable for use in a cooling device provided on the outlet side of the soaking zone of a continuous annealing furnace. The quenching apparatus 1 for a metal sheet S in fig. 1 includes a cooling apparatus 10 for cooling the metal sheet S, and a constraining roll 20 for constraining the cooled metal sheet S in the thickness direction.

The cooling device 10 is a cooling device for cooling the metal plate S using a cooling fluid CF, and includes a cooling tank 11 for storing the cooling fluid CF, and a plurality of nozzles 12 provided in the cooling tank 11 and spraying the cooling fluid CF onto the surface of the metal plate S. In the cooling tank 11, water is stored as the cooling fluid CF, and for example, the metal sheet S is immersed from the upper surface of the cooling tank 11 toward the conveying direction BD. In the cooling tank 11, a sink roll (sink roll) 2 for changing the conveying direction of the metal sheet S is provided.

The plurality of nozzles 12 are constituted by quenching nozzles or the like, for example, and are provided along the conveying direction of the metal sheet S at each of both sides of the metal sheet S. Therefore, the metal plate S is cooled by the cooling fluid CF in the cooling tank 11 and the cooling fluid CF ejected from the plurality of nozzles 12. In this way, by cooling the metal plate S using both the cooling tank 11 and the plurality of nozzles 12, the boiling state of the surface of the metal plate S is stabilized, and uniform shape control can be performed.

Although water quenching using water as the cooling fluid CF is exemplified, oil cooling using oil as the cooling fluid CF is also possible. In fig. 1, the case where the plurality of nozzles 12 are provided in the cooling tank 11 is illustrated, but the cooling method is not limited to this, as long as the metal plate S can be cooled in a desired temperature range. For example, the metal plate S may be cooled by only the cooling tank 11, or may be cooled by only the plurality of nozzles 12.

In the case where the nozzle 12 is provided in the cooling tank 11, the distance between the metal plate S and the nozzle 12 is important in rapid cooling by liquid quenching. In order to break the vapor film generated by the boiling phenomenon by the liquid jet stream and perform rapid cooling, it is desirable to provide the nozzle 12 so as to be close to the metal plate S. The distance between the tip end of the nozzle 12 and the metal plate S is preferably 10mm or more and 150mm or less. In the case of less than 10mm, there is a possibility that the deformed and shaken metal plate S contacts the nozzle 12. If the thickness exceeds 150mm, the effect of breaking the vapor film becomes weak, and it may be difficult to secure a sufficient cooling capacity.

The constraining rolls 20 are constraining rolls for constraining the metal plate S cooled by the cooling device 10 in the thickness direction, and are provided on both surfaces of the metal plate S in the cooling tank 11. In fig. 1, the pair of constraining rolls 20 are provided so as to face each other, but may be provided at positions offset in the conveying direction as long as they are constrained. In addition, although fig. 1 illustrates the case where the pair of constraining rolls 20 is provided, a plurality of 1 pair of constraining rolls 20 may be provided along the conveying direction.

In addition, from the viewpoint of the relationship between the roll rigidity and the deflection accompanying the restraining stress, the roll diameter of the restraining roll 20 is preferably 50mm or more and 300mm or less. The material of the constraining rolls 20 is not limited. When a normal steel roll is used as the constraining roll 20, the roll rigidity is insufficient when the roll diameter is smaller than 50mm, and it is difficult to apply a uniform constraining force to the metal plate S due to deflection, and there is a possibility of breakage. If the roller diameter is larger than 300mm, the area where the jet from the nozzle 12 does not reach the metal plate S becomes longer, and the vapor film may be insufficiently broken, thereby reducing the cooling capacity.

The constraining rolls 20 are provided so as to be movable in the conveying direction of the metal plates S. The conveyance direction herein means a direction in which the metal sheet S is conveyed. Specifically, the quenching apparatus 1 for a metal sheet S includes: a roller moving device 30 for moving the constraining roller 20; and a movement control device 40 that controls movement of the constraining roller 20. The roller moving device 30 includes a known driving unit such as a motor, for example, and is configured to move the constraining roller 20 in the conveying direction BD of the metal plate S or in a direction opposite to the conveying direction BD along the conveying direction of the metal plate S. Specifically, the roller moving device 30 can be suitably manufactured by a combination of mechanical components such as a jack (power jack), a screw type lifting device based on a screw mechanism or a gear mechanism, linear Motion Guide (LM rail) with small resistance against rolling, and the like. Fig. 1 shows an example in which the roller moving device 30 is constituted by a screw type lifting device. The constraining roller 20 is rotatably attached to one end of the L-shaped arm 31. The arm 31 is provided with a screw portion 32, another screw portion engaged with the screw portion 32, and a driving unit (each not shown) for driving the other screw portion on the other end side. The driving unit is fixed to a fixing portion (not shown). Therefore, when the other screw portion is rotated by the torque generated by the driving unit, the arm portion 31 moves in a direction parallel to the conveying direction BD.

If the drive unit is immersed in the liquid, maintenance of the drive unit may be difficult. Therefore, the drive unit is preferably disposed above the liquid surface of the cooling tank 11. The drive unit is preferably disposed in a space shielded from the inside of the furnace at a high temperature.

The roller moving device 30 may have a function of moving the constraining roller 20 in the thickness direction of the metal plate S and performing constraining and releasing of the metal plate S. The method is not particularly limited as long as it can be moved, but is more preferably an electric type in view of responsiveness.

The movement control device 40 is constituted by a hardware resource such as a computer, and controls the movement of the constraining roller 20. In particular, the movement control device 40 controls the operation of the roller movement device 30 to position the constraining rolls 20 so that the metal plates S are constrained at the positions RP at which the target temperature is reached. Here, when the temperature of the Ms point at which the martensitic transformation of the metal sheet S starts is TMs (c) and the temperature of the Mf point at which the martensitic transformation ends is TMf (c), the target temperature is preferably set within the temperature ranges of (tms+150) (°c) to (TMf-150) (°c). Accordingly, the deformation of the metal sheet S can be restrained by the restraining roller 20 at the position where the rapid thermal contraction and the phase change expansion occur simultaneously in the metal sheet S, and the deformation of the metal sheet S at the time of quenching can be restrained.

The movement control device 40 calculates a distance d from the cooling start position SP of the metal plate S by the cooling fluid CF to the position RP which is the target temperature constrained by the constraining rolls 20, and moves the constraining rolls 20 based on the calculated distance d. At this time, the movement control device 40 calculates the distance d using the conveyance speed v (mm/S) of the metal sheet S, the cooling start temperature T1 (°c), the target temperature T2 (°c) constrained by the constraining rolls 20, and the cooling speed CV (°c/S) of the metal sheet S based on the cooling device 10. Here, the cooling start temperature T1 is the temperature of the metal plate S immediately before the cooling start position SP at which the cooling of the metal plate S is started by the cooling fluid CF. For example, based on the cooling condition of the metal sheet S immediately before reaching the cooling start position SP and the quenching apparatus 1, the temperature immediately before reaching the cooling start position SP can be calculated. Specifically, the temperature of the metal plate S was measured by a non-contact thermometer on the outlet side of the soaking zone of the continuous annealing furnace. Then, based on the temperature and the temperature decrease amount of the metal plate S caused by natural cooling before reaching the quenching apparatus 1, the temperature of the metal plate S immediately before or at the time of reaching the cooling start position SP can be calculated. The temperature decrease of the metal plate S due to natural cooling can be obtained in advance by an experiment. The parameters may be obtained sequentially from the set value of the process computer or the actual operation value, or may be actually measured by using a speed sensor, a temperature sensor, or the like.

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

CV＝(T1-T2)/(d/v)

d＝(T1-T2)×v/CV · · · (1)

The cooling rate CV (c/S) can be expressed by the following formula (3) using a coefficient α (c·mm/S) indicating the nozzle shape, the type of the cooling fluid CF to be injected, the temperature, the injection amount, and other cooling conditions, and the plate thickness t of the metal plate S.

CV＝α/t · · · (2)

When formula (2) is substituted into formula (1), distance d can be represented by formula (3) below.

d＝(T1-T2)×v×t/α · · · (3)

The movement control device 40 stores a cooling rate CV (c/s) or α (c·mm/s) obtained in advance by experiments, numerical analysis, or the like. Then, the movement control device 40 obtains the distance d using the expression (1) or the expression (3), and moves the constraining rolls 20 so as to constrain the metal plate S at the position of the obtained distance d. The cooling rate CV is a value determined by the plate thickness or the like, and is set to be, for example, 1000 to 2000 (c/s) and α=500 to 2000 (c·mm/s) at a plate thickness of 1 to 2mm. Therefore, in the movement control device 40, the cooling rate CV may be set to 1500 (°c/s) in the middle of the above range. In this case, α may be treated as an intermediate value 1250 (. Degree. C. Multidot.mm/s). In this way, the cooling condition α obtained from the cooling rate CV, the plate thickness t, and the formula (2) may be set.

The quenching method and the method for manufacturing a metal sheet S according to the present invention will be described with reference to fig. 1. First, the metal sheet S is cooled by the cooling device 10 while being conveyed, and quenching of the metal sheet S is performed. At this time, the constraining rolls 20 are moved in the conveying direction so as to constrain the thickness direction of the metal plate S at the target temperature T2 at the position RP. At this time, the movement control device 40 calculates the distance d using the above equation (1) or equation (3), and moves the constraining rolls 20 so that the metal plates S are constrained at the calculated distance d. The movement of the constraining rolls 20 may be performed sequentially while quenching the metal sheet S. For example, the movement control device 40 may calculate the distance d and restrict the movement of the roller 20 at the time when the conveyance speed v is changed.

The conveying speed of the metal sheet S also varies among 1 metal sheet S (within 1 coil). Therefore, if the sheet metal S can be moved in the conveying direction or the opposite direction while being restrained by the restraining roller 20, the yield due to the defective shape of the portion where the leading end, trailing end, or the like of the sheet metal S is decelerated can be improved, which is more preferable. Alternatively, the movement control device 40 may calculate the distance d and restrict the movement of the roller 20 for each set period.

In the restraining position RP of the metal plate S based on the distance d, the moving distance of the restraining roller 20 for adjusting the restraining roller 20 can be estimated to be approximately 10mm to 150mm in a real situation. As shown in fig. 1, when the nozzles 12 are provided in the cooling tank 11, the constraining rolls 20 may be lifted and lowered between the nozzles 12 in a state where the intervals between the nozzles 12 are widened to about 10mm to 150mm in advance. For example, the rapid cooling by the liquid jet has a cooling capacity of about 1000 ℃/sec, and when the traveling speed of the metal sheet S is 60m/min (=1000 mm/sec), the temperature is changed by about 100 ℃ within a distance of 100 mm. That is, if the constraining rolls 20 can be lifted and lowered in the range of 10mm to 150mm, the temperature of the constrained metal plate S can be adjusted by about 10 ℃ to 150 ℃, and the moving distance of the constraining rolls 20 is a sufficient control adjustment range in practical cases.

Here, a case will be described in which the constraining roller 20 is moved significantly as compared with the above-described example. When the composition, sheet thickness, conveying speed, and the like of the metal sheet S vary greatly, it is necessary to move the constraining rolls 20 by 150mm or more in order to position the constraining rolls 20 at the constraining positions RP of the metal sheet S. The structure of moving the constraining roll 20 by 150mm or more will be described. Fig. 9 is a view showing another example of the quenching apparatus according to the embodiment of the present invention. The quenching apparatus 50 shown in fig. 9 includes a nozzle moving device 60 for moving the nozzle 12 in addition to the roller moving device 30 for moving the constraining roller 20. The nozzle moving devices 60 are disposed on both sides of the metal plate S as shown in fig. 9 (a). The nozzle moving device 60 is configured to move the nozzle 12 along the metal plate S and to move the nozzle 12 toward and away from the metal plate S. In the example shown in fig. 9, the constraining rolls 20 on both sides of the metal plate S are offset in the vertical direction.

As shown in fig. 9, the nozzle moving apparatus 60 includes: a lifting device 62 for moving the cooling pipes 61 respectively connected to the nozzles 12 in the vertical direction of the cooling device 10; and a slider 63 for moving the lifting device 62 toward and away from the metal plate S. The elevating device 62 is configured to be able to elevate and lower the plurality of cooling pipes 61 independently of each other. The elevating device 62 and the slider 63 may be conventionally known. A control device, not shown, is provided to control driving of the lifting device 62 and the slider 63.

Next, the operation of the quenching apparatus 50 shown in fig. 9 will be described. When the constraining roll 20 is moved upward from the position shown in fig. 9 (a), the constraining roll 20 interferes with the nozzle 12 located above it. Therefore, first, the nozzle 12 is separated from the metal plate S by the slider 63 in the width direction (left-right direction in fig. 9) of the cooling device 10. That is, the nozzle 12 is moved to retreat with respect to the constraining roller 20. The distance between the metal plate S and the tip end portion of the nozzle 12 after the nozzle 12 is separated from the metal plate S is set to be a distance at which the constraining roller 20 and the tip end portion of the nozzle 12 do not contact each other. In this state, the constraining roller 20 is moved upward or downward. Fig. 9 illustrates a case of moving upward. That is, the constraining rolls 20 are moved to the position RP appropriate for the target temperature T2 of the metal plate S. Fig. 9 (B) shows this state.

In the state shown in fig. 9 (B), the constraining rolls 20 and the nozzles 12 are adjacent to each other in the width direction of the cooling tank 11. Therefore, as shown in fig. 9 (B), the nozzle 12 adjacent to the constraining roller 20 in the width direction is moved to the lower side of the constraining roller 20 by the elevating device 62. Thus, the constraining rolls 20 and the nozzles 12 do not interfere with each other in any of the up-down direction and the width direction. Fig. 9 (C) shows this state. Next, the nozzles 12 are brought close to the metal plate S by the slider 63, and the interval between them is set to a predetermined interval and maintained. In this way, the movement of the constraining roller 20 is completed. Fig. 9 (D) shows this state.

After the state shown in fig. 9 (D), the distance between the nozzles 12 may be increased to about 10mm to 150mm in the same manner as in the example shown in fig. 1, and in this state, the constraining rolls 20 may be moved about 10mm to 150mm and adjusted to the position RP. Further, as long as the cooling capacity is allowed, the space between the metal plate S and the nozzle 12 may be maintained to be widened so that the constraining roll 20 can move 150mm or more.

According to the above embodiment, by providing the constraining rolls 20 so as to be movable in the conveying direction, it is possible to control the distance from the cooling start position to the constraining rolls 20 and constrain the metal plates S of the target temperature T2 by the constraining rolls 20 regardless of the manufacturing conditions of the metal plates S. As a result, in the continuous annealing equipment, the shape defect of the metal plate S caused by the manufacturing conditions of the metal plate S generated at the time of quenching can be suppressed.

That is, the temperature of the metal sheet S fed to the quenching apparatus 1 varies depending on, for example, the feeding speed v, the cooling start temperature T1 of the metal sheet S, the thickness T of the metal sheet S, and other conditions for producing the metal sheet S. Therefore, when the distance d is set to be constant regardless of the manufacturing conditions, a deviation occurs in the temperature of the metal sheet S when reaching the constraining rolls 20.

In order to solve this problem, it has been 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. The restraint roller 20 itself moves, so that the metal sheet S can be restrained in a target temperature range even if the manufacturing conditions change without causing instability in the cooling pattern.

In particular, the complex and uneven shape generated when the structure volume expands due to the martensitic transformation during quenching of the metal sheet S can be reduced. Therefore, when the metal plate S is a high-strength steel plate (high-tensile steel), the deformation suppressing effect is particularly large. Specifically, the method is preferably applied to the production of a steel sheet having a tensile strength of 580MPa or more. The upper limit of the tensile strength is not particularly limited, and may be 2000MPa or less, for example. As the high-strength steel sheet (high-tensile steel), there are a high-strength cold-rolled steel sheet, a hot-dip galvanized steel sheet, an electrogalvanized steel sheet, an alloyed hot-dip galvanized steel sheet, and the like, which have been subjected to surface treatment.

Specific examples of the composition of the high-strength steel sheet include the following: in mass%, C is 0.04% or more and 0.35% or less, si is 0.01% or more and 2.50% or less, 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, cr, mo, nb, V, ni, cu is contained as needed, at least 1 or more of Ti is 0.5% or less, B, sb is contained as needed, and the balance is Fe and unavoidable impurities. The metal plate S is not limited to a steel plate, and may be a metal plate other than a steel plate.

Example 1

Embodiments of the present invention are described. As an example of the present invention, the quenching apparatus 1 according to the embodiment of the present invention was used to quench a high-tensile cold-rolled steel sheet having a tensile strength 1470MPa grade, wherein the sheet thickness t is 1.0mm and the sheet width is 1000 mm. The composition of the high-tensile cold-rolled steel sheet having a tensile strength of 1470MPa was, in mass%, 0.20% C, 1.0% Si, 2.3% Mn, 0.005% P and 0.002% S. The temperature TMs at the Ms point of the high-tension cold-rolled steel sheet was 300℃and the temperature TMf at the Mf point was 250 ℃. Therefore, the target temperature T2 at the time of passing through the constraining rolls 20 may be set within a range of 450 to 100 ℃, and the target temperature T2 may be set to 400 ℃. The cooling start temperature T1 was 800 ℃, and the target temperature T2 was 400 ℃. The temperature of the cooling fluid CF was 30℃and the cooling rate CV was set at 1500 (. Degree.C/s).

As a change in the production conditions, the transport speed v was changed between 1000 and 3000mm/s, and the distance d (mm) was controlled to d=267 to 800m in accordance with the change in the transport speed v based on the formula (1). 10 cooled steel sheets were collected every 100m in the longitudinal direction (i.e., the same direction as the conveying direction of the steel sheets), and the warpage amounts of the respective steel sheets were examined. Fig. 2 is a schematic diagram showing an example of the definition of the warpage amount. As shown in fig. 2, regarding the warpage amount, when the steel sheet is placed on a horizontal plane, the height from the ground plane to the highest position is set as the warpage amount.

Fig. 3 is not a graph showing the relationship between the conveyance speed v and the target temperature in the example of the present invention, and fig. 4 is a graph showing the relationship between the conveyance speed v and the amount of warpage of the steel sheet as the metal sheet S in the example of the present invention. As shown in fig. 3, even if the conveying speed v is changed, the distance d is changed by moving the constraining roller 20 in accordance with the conveying speed v, and the temperature (c) at the time of passing through the constraining roller 20 can be controlled to be the target temperature 400±25 ℃. As a result, as shown in fig. 4, the warpage of the steel sheet was reduced to 10mm or less. Thus, the deviation of the warpage amount, i.e., the difference between the maximum value and the minimum value, is suppressed to 4.2mm.

Fig. 5 is a graph showing a relationship between the conveyance speed v and the target temperature in comparative example 1, and fig. 6 is a graph showing a relationship between the conveyance speed v and the amount of warpage of the steel sheet as the metal sheet S in comparative example 1. As comparative example 1, a quenching apparatus in which the constraining rolls 20 were fixed as in patent document 1 was used, and other conditions were the same as those in the above-described invention example. In comparative example 1, the distance d (mm) from the cooling start position to the constraining roll 20 was fixed to d=400 mm.

In comparative example 1, as shown in FIG. 5, the temperature (. Degree. C.) at the time of passing through the constraining rolls was greatly changed depending on the transport speed v (mm/s), and control was not possible. Therefore, the temperature (. Degree. C.) at the time of passing through the constraining rolls 20 is outside the range of 450℃to 100℃under the conditions other than v=1000 mm/s and v=1500 mm/s. As a result, as shown in fig. 6, the steel sheet was not less than 10mm in all of the warpage amounts under the conditions other than v=1000 mm/s and v=1500 mm/s, and the deformation inhibiting effect was insufficient. As a result, the difference between the maximum value and the minimum value of the warpage amount, that is, the deviation, was increased to 10.3mm.

Fig. 7 is a graph showing a relationship between the conveyance speed v and the target temperature in comparative example 2, and fig. 8 is a graph showing a relationship between the conveyance speed v and the amount of warpage of the steel sheet as the metal sheet S in comparative example 2. As comparative example 2, as shown in patent document 2, the distance d is controlled according to the cooling start position by moving the movable shielding portion while the constraining rolls 20 remain fixed. The other conditions were the same as in the present invention example, and the high-tensile cold-rolled steel sheet was produced.

As shown in fig. 7, in comparative example 2, the temperature (c) at the time of passing through the constraining rolls 20 was greatly changed regardless of the manufacturing conditions of the steel sheet such as the conveying speed v (mm/s), and control was not possible. Therefore, the temperature (. Degree. C.) at the time of passing through the constraining rolls is outside the range of 450℃to 100℃under all conditions. As shown in fig. 8, the steel sheet has a warp of 10mm or more, and the effect of suppressing deformation is insufficient. As a result, the deviation of the warpage amount (difference between maximum value and minimum value) was increased to 9.2mm.

The embodiments of the present invention are not limited to the above embodiments, and various modifications can be applied. For example, in the above embodiment, the cases (tms+150) (°c) to (TMf-150) (°c) are exemplified for the target temperature T2, but the present invention is not limited thereto. In terms of ensuring the degree of freedom in the processing and handling in the subsequent steps, for example, the target temperature T2 may not be limited to (tms+150) (°c) to (TMf-150) (°c) as long as there is no deviation in the shape of the metal plate S such as the amount of warpage.

In this case, the target temperature T2 is determined in advance in consideration of the predicted shape (for example, the amount of warpage) while securing the degree of freedom of processing and operation in the subsequent steps, and the distance d from the cooling start position to the constraining rolls 20 is controlled by the positional adjustment of the constraining rolls 20. Then, the shape (for example, the amount of warpage) of the metal plate S may be set to the same level, for example, a deviation of the amount of warpage defined in fig. 2 may be set to within 4mm so that the temperature of the metal plate S becomes a predetermined temperature T2 when passing through the constraining rolls 20.

The constraining rolls 20 are not limited to one pair, and may be provided in a plurality of pairs or a plurality of pairs. In this case, the position control may be performed intensively on the entire pair of constraining rolls, or a mechanism for controlling the position and opening/closing of each of the plurality of constraining rolls may be employed.

Description of the reference numerals

1. Quenching device for metal plate

10. Cooling device

11. Cooling tank

12. Nozzle

20. Restraining roller

30. Roller moving device

40. Mobile control device

BD conveying direction

CF cooling fluid

S-shaped metal plate

Claims

1. A quenching apparatus for a metal plate, which is a quenching apparatus for a metal plate that cools the metal plate while conveying the metal plate,

the quenching apparatus includes:

a cooling device that cools the conveyed metal plate;

a constraining roll that conveys the metal plate cooled by the cooling device while constraining the metal plate in a thickness direction;

a roller moving device that moves the constraining roller in a conveying direction of the metal plate; and

and a movement control device that controls the operation of the roller movement device to adjust the position of the constraining roller.

2. The quenching apparatus for a metal sheet according to claim 1, wherein the cooling apparatus has a plurality of nozzles for spraying a cooling fluid to the metal sheet to cool the metal sheet.

3. The quenching apparatus for metal sheets according to claim 1 or 2, wherein the cooling apparatus has a cooling tank for immersing the metal sheets for cooling.

4. A quenching apparatus for a metal sheet according to any one of claims 1 to 3, wherein the movement control means controls the operation of the roller moving means to position the constraining rollers so that the constraining rollers constrain the metal sheet at a position where the metal sheet has reached a target temperature.

5. The quenching apparatus for a metal sheet according to claim 4, wherein the target temperature is set within a temperature range of (TMs+150) (DEGC) to (TMf-150) (DEGC) when the temperature of the Ms point at which the martensitic transformation of the metal sheet starts is TMs (DEG C) and the temperature of the Mf point at which the martensitic transformation ends is TMf (DEG C).

6. The quenching apparatus for a metal sheet according to claim 4 or 5, wherein the movement control means sets a distance from a cooling start position based on the cooling means to the constraining rolls based on a conveying speed of the metal sheet, a cooling start temperature of the metal sheet at a start of cooling by the cooling means, the target temperature, and a cooling speed of the metal sheet, and moves a position of the constraining rolls so as to be the set distance.

7. The quenching apparatus for a metal sheet according to claim 6, wherein in the movement control apparatus, when a conveyance speed of the metal sheet is v (mm/s), a cooling start temperature is T1 (DEG C), the target temperature is T2 (DEG C), and a cooling speed of the metal sheet by the cooling apparatus is CV (DEG C/s), a distance d (mm) from the cooling start position to the constraining rolls is obtained from formula (1),

d＝(T1-T2)×v/CV (1)。

8. the quenching apparatus of metal sheets as set forth in claim 7, wherein in the movement control apparatus, the cooling speed CV is set in a form of cv=α/t according to a coefficient α representing a cooling condition of the metal sheets and a plate thickness t of the metal sheets.

9. A method for quenching a metal plate, which is a method for quenching a metal plate by cooling the metal plate while conveying the metal plate, wherein,

when the cooled metal plate is restrained in the thickness direction by a restraining roller, the restraining roller is moved in the conveying direction of the metal plate so as to restrain the metal plate at a position where the metal plate becomes a target temperature.

10. The quenching method as claimed in claim 9, wherein the target temperature is set within a temperature range of (tms+150) (°c) to (TMf-150) (°c) when the temperature of the Ms point at which the martensitic transformation of the metal sheet starts is TMs (°c) and the temperature of the Mf point at which the martensitic transformation ends is TMf (°c).

11. A quenching method as claimed in claim 9 or 10, wherein the movement of the constraining rolls is performed by:

setting a distance from a cooling start position to the constraining rolls based on a conveyance speed of the metal plate, a cooling start temperature of the metal plate at the start of cooling, the target temperature, and a cooling speed of the metal plate,

the constraining rolls are moved so as to be set at a predetermined distance.

12. The method for quenching a metal sheet according to claim 11, wherein, regarding the distance from the cooling start position to the constraining rolls, the distance d (mm) from the cooling start position to the constraining rolls is obtained from formula (1) with respect to the distance v (mm/s) from the cooling start position, the cooling start temperature T1 (DEG C), the target temperature T2 (DEG C), and the cooling speed CV (DEG C/s) of the metal sheet,

d＝(T1-T2)×v/CV (1)。

13. the quenching method as claimed in claim 12, wherein the cooling rate CV is set in a form of CV = α/t according to a coefficient α representing a cooling condition of the metal plate and a plate thickness t of the metal plate.

14. A method for producing a high-strength cold-rolled steel sheet, which comprises using the method for quenching a metal sheet according to any one of claims 9 to 13.

15. 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 any one of a hot dip galvanization treatment, an electrogalvanization treatment, and an alloyed hot dip galvanization treatment.