KR20240035542A - Quenching device and method and manufacturing method of metal plate - Google Patents

Abstract

Suppresses deviations in the shape of the metal plate that occur during stamping.
The metal plate cooling device 1 cools the metal plate while conveying it, and includes a cooling device 10 that cools the conveyed metal plate S, and a thickness of the metal plate S cooled by the cooling device 10. A restraining roll 20 that conveys while restraining in a certain direction, a roll moving device 30 that moves the restraining roll 20 along the conveying direction of the metal plate S, and restraint by controlling the operation of the roll moving device 30. A movement control device 40 is provided to adjust the position of the roll 20.

Description

Quenching device and method and manufacturing method of metal plate

The present invention relates to a quenching device and quenching method for performing annealing while continuously transporting a metal plate, and a method for manufacturing a metal plate.

In a continuous annealing facility in which annealing is performed while continuously conveying a metal plate, the metal plate is cooled after heating to cause a phase transformation, thereby creating a metal plate structure. In particular, in the automobile industry, demand for thinner high-strength steel sheets (HI-TEN) is increasing for the purpose of reducing the weight of the car body and achieving both crash safety. When manufacturing high-strength steel sheets, technology for rapidly cooling the steel sheets becomes important. As one of the technologies with the fastest cooling rate of metal plates, the water cooling method is known. In the water quenching method, quenching of the metal plate is performed by immersing the heated metal plate in water and simultaneously spraying cooling water onto the metal plate through a quench nozzle installed in the water.

When forming a metal plate, shape defects such as bending or waviness deformation occur in the metal plate. This is due to thermal shrinkage of the metal plate due to rapid cooling. In particular, when the temperature of the metal plate goes from the temperature Ms at which martensite transformation begins to the temperature Mf at which martensite transformation ends, rapid thermal contraction and transformation expansion occur simultaneously.

Therefore, various methods have conventionally been proposed to prevent shape defects in metal plates during forming (for example, see Patent Documents 1 and 2). In Patent Document 1, when the temperature at the Ms point where the martensite transformation of the metal sheet starts is TMs (°C) and the temperature at the Mf point where the martensite transformation ends is TMf (°C), the temperature of the metal sheet is (TMs+150 ) (°C) to (TMf-150) (°C) range, a method of restraining a metal plate with a pair of restraint rolls formed in a cooling liquid has been proposed.

In Patent Document 2, when performing a cooling method of cooling the surface of a metal plate by spraying water from a plurality of water jet nozzles, the metal plate is restrained by a restraining roll and the metal plate is cooled by a cooling fluid through movable masking. Controlling the starting position and the distance of the constraint roll is disclosed. In addition, as in Patent Document 1, when the temperature at the Ms point where the martensite transformation of the metal sheet starts is TMs (°C), and the temperature at the Mf point where the martensite transformation ends is TMf (°C), the metal plate is A method of passing a restraining roll at a temperature of (TMs+150) (°C) to (TMf-150) (°C) has been proposed.

Japanese Patent Publication No. 6094722 Japanese Patent Publication No. 2019-90106

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) changes depending on the manufacturing conditions of the metal plate. For this reason, the restraining roll cannot restrain the metal plate at a position where the temperature of the metal plate is (TMs+150) (°C) to (TMf-150) (°C), and there is a possibility that deviation in the shape of the metal plate occurs.

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 sprayed from the water jet nozzle below the movable masking, thereby destabilizing the cooling ability of the metal plate. In addition, since each nozzle is masked, the cooling capacity changes step by step (discontinuously), and as a result, the position where the temperature of the metal plate becomes (TMs+150) (°C) to (TMf-150) (°C) becomes unstable, causing the metal plate to become unstable. There is a possibility that deviations may occur in the shape.

The present invention was made to solve such problems, and includes a quenching device capable of controlling the temperature of a metal plate at a position where the metal plate is restrained with high precision and suppressing deviation in the shape of the metal plate that occurs during quenching. The purpose is to provide a quenching method and a manufacturing method of metal plate products.

[1] A metal plate cooling device that cools a metal plate while conveying it, comprising: a cooling device that cools the conveyed metal plate; a restraining roll that conveys the metal plate cooled by the cooling device while restraining it in the thickness direction; A metal plate quenching device comprising a roll moving device that moves a restraining roll along a conveyance direction of the metal plate, and a movement control device that controls the operation of the roll moving device to adjust the position of the restraining roll.

[2] The cooling device for a metal plate according to [1], wherein the cooling device has a plurality of nozzles for cooling the metal plate by spraying a cooling fluid.

[3] The cooling device for a metal plate 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 to position the restraint roll so that the restraint roll restrains the metal plate at a position where the metal plate reaches the target temperature. [1] to [ 3] The metal plate quenching device according to any one of the above.

[5] The above target temperature is (TMs+150 ) The quenching device for the metal plate described in [4], which is set to a temperature range of (℃) to (TMf-150) (℃).

[6] The movement control device determines the distance from the cooling start position by the cooling device to the constraint roll, a conveyance speed of the metal plate, a cooling start temperature of the metal plate at the start of cooling by the cooling device, and The metal sheet quenching device according to [4] or [5], wherein the target temperature is set based on the cooling rate of the metal sheet, and the position of the constraint roll is moved to a set distance.

[7] The movement control device sets the conveyance 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 rate of the metal plate by the cooling device. When CV (°C/s), the distance d (mm) from the cooling start position to the constraint roll is obtained from equation (1). The metal plate quenching device described in [6].

d = (T1-T2)×v/CV (One)

[8] In the movement control device, the cooling rate CV of the metal plate described in [7] is set as CV = α/t by the coefficient α representing the cooling condition of the metal plate and the plate thickness t of the metal plate. Qing device.

[9] A method of cooling a metal plate while transporting the metal plate, wherein, when the cooled metal plate is restrained in the thickness direction by a restraining roll, the metal plate is restrained at a position where the metal plate is at the target temperature. A method of quenching metal plates by moving restraint rolls along the conveying direction.

[10] The above target temperature is (TMs+150 ) The quenching method of a metal plate described in [9], which is set to a temperature range of (℃) to (TMf-150) (℃).

[11] The movement of the restraint roll is based on the conveyance speed of the metal plate, the cooling start temperature of the metal plate at the start of cooling, the target temperature, and the cooling rate of the metal plate, from the cooling start position. The quenching method of a metal plate according to [9] or [10], which is performed by setting a distance to and moving the constraint roll so that it becomes the set distance.

[12] The distance from the cooling start position to the constraint roll is the conveyance speed of the metal plate in v (mm/s), the cooling start temperature in T1 (°C), the target temperature in T2 (°C), and the cooling of the metal plate. The quenching method of a metal plate described in [11], where the distance d (mm) from the cooling start position to the restraining roll is obtained from equation (1) when the speed is set to CV (°C/s).

d = (T1-T2)×v/CV (One)

[13] The cooling method of a metal plate according to [12], wherein the cooling rate CV is set as CV = α/t by a coefficient α representing the cooling condition of the metal plate and the plate thickness t of the metal plate.

[14] A method of manufacturing a high-strength cold-rolled steel sheet using the metal sheet quenching method according to any one of [9] to [13].

[15] A method of producing a high-strength steel sheet, in which the high-strength steel sheet obtained by the method described in [14] is subjected to any of hot-dip galvanizing treatment, electrogalvanizing treatment, or alloyed hot-dip galvanizing treatment.

According to the present invention, when cooling a metal plate, the position of the restraining roll is adjusted along the conveyance direction of the metal plate according to the temperature of the metal plate, thereby controlling the distance from the cooling start position to the restraining roll, thereby reducing the Deviation in the shape of the metal plate can be suppressed.

1 is a schematic diagram showing a quenching device according to an embodiment of the present invention.
Figure 2 is a schematic diagram showing an example of the definition of the amount of bending of a metal plate.
Fig. 3 is a graph showing the relationship between the conveyance speed and target temperature in the example of the present invention.
Fig. 4 is a graph showing the relationship between the conveyance speed and the amount of bending of the metal plate in the example of the present invention.
Fig. 5 is a graph showing the relationship between the conveyance speed and target temperature in Comparative Example 1.
Figure 6 is a graph showing the relationship between the conveyance speed and the amount of bending of the metal plate in Comparative Example 1.
Fig. 7 is a graph showing the relationship between the conveyance speed and target temperature in Comparative Example 2.
Fig. 8 is a graph showing the relationship between the conveyance speed and the amount of bending of the metal plate in Comparative Example 2.
Fig. 9 is a diagram explaining the movement of the constraint roll and nozzle in another example of the quenching device according to the embodiment of the present invention.

Embodiments of the present invention will be described based on the drawings. 1 is a schematic diagram showing a quenching device according to an embodiment of the present invention. In addition, the quenching device 1 in FIG. 1 quenches a steel material, for example, a metal plate S, and is applied to a cooling facility formed on the exit side of the crack zone of a continuous annealing furnace. The quenching device 1 for the metal plate S in FIG. 1 includes a cooling device 10 for cooling the metal plate S, and a restraining roll 20 for restraining the cooled metal plate S in the thickness direction. do.

The cooling device 10 cools the metal plate S using cooling fluid CF, and is installed in the cooling tank 11 to store the cooling fluid CF, and the metal plate ( S) is provided with a plurality of nozzles (12) for spraying cooling fluid (CF) on the surface. Water is stored in the cooling tank 11 as cooling fluid CF, and, for example, the metal plate S is immersed from the upper surface of the cooling tank 11 toward the conveyance direction BD. Additionally, a sink roll 2 is installed in the cooling tank 11 to change the conveyance direction of the metal plate S.

The plurality of nozzles 12 are, for example, made of square nozzles, etc., and are installed on each of both sides of the metal plate S along the conveyance 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 sprayed 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 can be stabilized and uniform shape control can be performed. .

In addition, although the case of water cooling using water as the cooling fluid (CF) is illustrated, oil cooling using oil as the cooling fluid (CF) may also be used. In addition, in FIG. 1, the case where a plurality of nozzles 12 are installed in the cooling tank 11 is illustrated, but as long as it is a method that can cool the metal plate S in the desired temperature range, the cooling method is as follows. It is not limited to For example, the metal plate S may be cooled only with the cooling tank 11 or may be cooled only with the plurality of nozzles 12.

When installing the nozzle 12 in the cooling tank 11, the distance between the metal plate S and the nozzle 12 is important in rapid cooling by liquid quenching. Since rapid cooling is performed by destroying the vapor film generated by the boiling phenomenon by liquid jetting, it is preferable that the nozzle 12 is installed close to the metal plate S. The distance between the tip of the nozzle 12 and the metal plate S is preferably 10 mm or more and less than 150 mm. If it is less than 10 mm, there is a possibility that the deformed and fluttering metal plate S and the nozzle 12 come into contact. Additionally, if it exceeds 150 mm, the effect of destroying the vapor film may be weakened, making it difficult to secure sufficient cooling capacity.

The restraining rolls 20 restrain 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, the pair of restraining rolls 20 are installed to face each other, but they may be installed at positions shifted along the conveyance direction as long as they are restrained. 1 illustrates the case where a pair of restraint rolls 20 is installed, but a plurality of pairs of restraint rolls 20 may be installed along the conveyance direction.

In addition, the roll diameter of the constraining roll 20 is preferably 50 mm or more and within 300 mm from the correlation between roll rigidity and bending accompanying the constraining stress. The material of the constraint roll 20 is not limited. In the case of using a general steel roll as the restraining roll 20, if the roll diameter is less than 50 mm, the roll rigidity is insufficient, and it becomes difficult to apply a uniform restraining force to the metal plate S due to bending. , there is a possibility of damage. In addition, when the roll diameter is larger than 300 mm, the section in which the jet of water from the nozzle 12 does not reach the metal plate S becomes long, resulting in insufficient destruction of the vapor film, and there is a possibility that the cooling ability is reduced.

The restraint roll 20 is installed to be movable along the conveyance direction of the metal plate S. Here, the conveyance direction refers to the direction in which the metal plate S is conveyed. Specifically, the quenching device 1 for the metal plate S includes a roll moving device 30 that moves the restraining roll 20, and a movement control device 40 that controls the movement of the restraining roll 20. is provided. The roll moving device 30 is provided with known driving means, such as a motor, and moves the constraint roll 20 along the conveyance direction BD of the metal plate S, Alternatively, it is configured to move in a direction opposite to the conveyance direction (BD). Specifically, the roll moving device 30 can be appropriately manufactured by combining mechanical parts such as a power jack, a screw-type lifting device using a screw mechanism or a gear mechanism, and a Linear Motion Guide (LM Guide) with low resistance using rolling. You can. FIG. 1 shows an example in which the roll moving device 30 is configured by a screw-type lifting device. A restraining roll 20 is rotatably mounted on one end of the L-shaped arm 31. A threaded portion 32, another threaded portion engaged with the threaded portion 32, and driving means (not shown) for driving the other threaded portion are formed on the other end side of the arm 31. The driving means is fixed to a fixed part (not shown). Therefore, when the other screw portion rotates in response to the torque generated by the drive means, the arm 31 moves in a direction parallel to the conveyance direction BD.

If the above-described drive means is immersed in liquid, maintenance of the drive means may become difficult. Therefore, the drive means is preferably installed above the liquid level of the cooling tank 11. Additionally, the driving means is preferably installed in a space shielded from the high temperature inside the furnace.

The roll moving device 30 may have a function of moving the restraining roll 20 in the thickness direction of the metal plate S to restrain and release the restraint from the metal plate S. Additionally, the method is not particularly important as long as it can be moved, but considering responsiveness, an electric type is more preferable.

The movement control device 40 is made up of hardware resources such as a computer, and controls the movement of the restraint roll 20. In particular, the movement control device 40 controls the operation of the roll movement device 30 to position the restraining roll 20 so that the metal plate S is restrained at the position RP at which the target temperature is reached. Here, the target temperature is (TMs+150 ) (℃) to (TMf-150) (℃) is preferably set in the temperature range. As a result, the deformation of the metal plate S can be restrained by the restraining roll 20 at a position where rapid thermal contraction and transformation expansion occur simultaneously in the metal plate S, thereby preventing deformation of the metal plate S during loading. It can be suppressed.

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 the target temperature constrained by the constraint roll 20. Then, the restraint roll 20 is moved based on the calculated distance d. At this time, the movement control device 40 controls the conveyance speed v (mm/s) of the metal plate S, the cooling start temperature T1 (°C), the target temperature T2 (°C) restrained by the restraining roll 20, and the cooling device. The distance d is calculated using the cooling rate CV (°C/s) of the metal plate S according to (10). Here, the cooling start temperature T1 is the temperature of the metal plate S just before the cooling start position SP where cooling of the metal plate S is started by the cooling fluid CF. For example, based on the cooling situation of the metal plate S up to the cooling start position (SP) or the cooling device 1, the temperature just before reaching the cooling start position (SP) can be calculated. . Specifically, at the exit side of the crack zone of the continuous annealing furnace, the temperature of the metal plate S is measured using a non-contact type thermometer. Then, based on that temperature and the temperature drop due to natural cooling of the metal plate S until it reaches the cooling device 1, the metal plate S just before or at the time of reaching the cooling start position SP ) temperature can be calculated. The temperature decrease due to natural cooling of the metal plate S described above can be determined in advance through experiment. In addition, the above parameters may be sequentially acquired from the set values of the process computer or operation performance values, or may be actually measured using a speed sensor or temperature sensor.

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

CV = (T1-T2)/(d/v)

d = (T1-T2)×v/CV… (One)

The cooling rate CV (℃/s) is a coefficient α (℃·mm/s) that represents cooling conditions such as the nozzle shape or the type of cooling fluid (CF) sprayed, temperature, and spray amount, and the plate of the metal plate (S). It can be expressed in equation (3) below using the thickness t.

CV = α/t … (2)

By substituting equation (2) into equation (1), the distance d can be expressed as equation (3) below.

d = (T1-T2)×v×t/α… (3)

The movement control device 40 stores the cooling rate CV (°C/s) or α (°C·mm/s) previously determined through experiment or numerical analysis. Then, the movement control device 40 determines the distance d using equation (1) or equation (3), and moves the restraining roll 20 so as to restrain the metal plate S at the position of the obtained distance d. In addition, the cooling rate CV is a value determined depending on the plate thickness, etc., and 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). am. Therefore, in the movement control device 40, the cooling rate CV may be set to 1500 (°C/s), which is in the middle of the above range. In this case, α may be treated as the intermediate value of 1250 (°C·mm/s). In this way, the above-mentioned cooling rate CV, plate thickness t, and cooling condition α obtained by equation (2) may be set.

Referring to FIG. 1, the quenching method and the manufacturing method of the metal plate (S) of the present invention will be described. First, the metal plate S is conveyed and cooled by the cooling device 10, and the metal plate S is quenched. At this time, the restraining roll 20 moves along the conveyance direction so as to restrain the thickness direction of the metal plate S 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 equation (1) or equation (3), and the restraining roll 20 is used to restrain the metal plate S at the position of the calculated distance d. ) moves. In addition, the movement of the restraining roll 20 can be carried out sequentially even while the metal plate S is being clamped. For example, the movement control device 40 may calculate the distance d and move the constraint roll 20 at the timing when the conveyance speed v changes.

The conveyance speed of the metal plate S varies even for one sheet of metal plate S (within one coil). For this reason, if the metal plate S can be moved in the conveyance direction or the opposite direction while restrained by the restraining roll 20, the yield due to poor shape of the decelerated portion, such as the tip and tail end of the metal plate S, can be improved. Therefore, it is also preferable. Alternatively, the movement control device 40 may calculate the distance d and move the constraint roll 20 at each set period.

The moving distance of the constraint roll 20 for adjusting the constraint roll 20 to the constraint position RP of the metal plate S based on the distance d can be estimated to be approximately 10 mm to 150 mm in reality. As shown in FIG. 1, when the nozzles 12 are installed in the cooling tank 11, the space between the nozzles 12 is widened in advance to about 10 mm to 150 mm, and the nozzles 12 are restrained. The roll 20 may be raised and lowered. Additionally, for example, rapid cooling by liquid jetting has a cooling capacity of about 1000°C/sec, and when the traveling speed of the metal plate S is 60 m/min (=1000 mm/sec), a distance of 100 mm It varies by about 100℃. That is, if the restraining roll 20 can be raised and lowered in the range of 10 mm to 150 mm, the temperature of the restrained metal plate S can be adjusted to about 10 ° C. to 150 ° C., and the moving distance of the restraining roll 20 described above is , In reality, this is a sufficient control adjustment range.

Here, a case where the restraint roll 20 is moved larger than the example described above will be described. When the composition, plate thickness, conveyance speed, etc. of the metal plate S change significantly, the restraint roll 20 must be moved by 150 mm or more in order to position the restraint roll 20 at the restraint position RP of the metal plate S. There is a need to do it. 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 a quenching device according to an embodiment of the present invention. The quenching device 50 shown in FIG. 9 is provided with a nozzle moving device 60 that moves the nozzle 12 in addition to the roll moving device 30 that moves the constraint roll 20. As shown in FIG. 9(A), the nozzle moving device 60 is disposed on both sides of the metal plate S, respectively. The nozzle moving device 60 is configured to move the nozzle 12 along the metal plate S and to move the nozzle 12 closer to and away from the metal plate S. In addition, in the example shown in FIG. 9, the restraining 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 a lifting device 62 that moves the cooling pipe 61 connected to each nozzle 12 in the vertical direction of the cooling device 10, and a lifting device 62 It is provided with a slider 63 that moves the device 62 closer to and farther away from the metal plate S. The lifting device 62 is configured to enable lifting and lowering of each of the plurality of cooling pipes 61 independently of each other. Additionally, the lifting device 62 and the slider 63 may be conventionally known ones. Additionally, a control device (not shown) that controls the driving of the lifting device 62 and the slider 63 is provided.

Next, the operation of the quenching device 50 shown in FIG. 9 will be explained. When the constraint roll 20 is moved upward from the position shown in FIG. 9(A), the constraint roll 20 and the nozzle 12 located above it interfere with each other. Therefore, first, the nozzle 12 is separated from the metal plate S by the slider 63 in the width direction (left and right direction in FIG. 9) of the cooling device 10. That is, the nozzle 12 is moved to retract with respect to the constraint roll 20. The gap between the metal plate S and the tip of the nozzle 12 after separating the nozzle 12 from the metal plate S is such that the restraint roll 20 and the tip of the nozzle 12 do not contact each other. It is set. In that state, the restraining roll 20 is moved upward or downward. Figure 9 shows the case where it is moved upward. That is, the restraining roll 20 is moved to a position RP suitable for the target temperature T2 of the metal plate S. Figure 9(B) shows that state.

Moreover, in the state shown in FIG. 9(B), the constraint roll 20 and the nozzle 12 are adjacent to each other in the width direction of the cooling tank 11. Therefore, the nozzle 12 adjacent to the restraint roll 20 in the width direction is moved to the lower side of the restraint roll 20 by the lifting device 62, as shown in FIG. 9(B). I order it. As a result, the constraint roll 20 and the nozzle 12 do not interfere with each other in either the vertical direction or the width direction. Figure 9(C) shows that state. Next, each nozzle 12 is brought closer to the metal plate S by the slider 63, and the gap between them becomes a preset gap and is maintained. In this way, the movement of the restraint roll 20 is completed. Figure 9(D) shows that state.

Additionally, after the state shown in FIG. 9(D) is reached, almost the same as the example shown in FIG. 1, the gap between the nozzles 12 is widened to about 10 mm to 150 mm, and in that state, the gap between the nozzles 12 is widened to about 10 mm to 150 mm. The restraining roll 20 may be moved by approximately 150 mm and adjusted to the above position (RP). Additionally, if the cooling capacity allows, the gap between the metal plate S and the nozzle 12 may be kept widened so that the restraining roll 20 can move by 150 mm or more.

According to the above embodiment, by installing the constraint roll 20 to be movable along the conveyance direction, the distance from the cooling start position to the constraint roll 20 is controlled, and regardless of the manufacturing conditions of the metal plate S, the target The metal plate S at temperature T2 can be restrained by the restraint roll 20. As a result, in continuous annealing equipment, it is possible to suppress shape defects of the metal plate S that occur during annealing due to the manufacturing conditions of the metal plate S.

That is, the temperature of the metal plate S conveyed by the quenching device 1 is, for example, the conveyance speed v, the cooling start temperature T1 of the metal plate S, and the plate thickness t of the metal plate S. There are variations depending on manufacturing conditions. Therefore, when the distance d is set to be constant regardless of manufacturing conditions, variations also occur in the temperature of the metal plate S when it reaches the restraining roll 20.

In order to solve this problem, it was found that it is effective to change the position of the constraint roll 20 in order to accurately control the shape at different optimal temperature positions depending on manufacturing conditions. By moving the restraining roll 20 itself, the metal plate S can be restrained in the target temperature range even if manufacturing conditions change, without causing instability in the cooling form.

In particular, the complex and uneven uneven shape that occurs when martensitic transformation occurs during rapid cooling of the metal plate S and the tissue expands in volume can be reduced. Therefore, when the metal plate S is a high-strength steel plate (High Ten), the deformation suppression effect becomes particularly large. Specifically, it is desirable to apply it to the production of steel sheets with a tensile strength of 580 MPa or more. The upper limit of the tensile strength is not particularly limited, but may be 2000 MPa or less as an example. The above-mentioned high-strength steel sheets (high-strength steel sheets) include high-strength cold-rolled steel sheets, hot-dip galvanized steel sheets that have been subjected to surface treatment, electro-galvanized steel sheets, and alloyed hot-dip galvanized steel sheets.

In addition, as a specific example of the composition of the high-strength steel sheet, in mass%, C is 0.04% to 0.35%, Si is 0.01% to 2.50%, Mn is 0.80% to 3.70%, and P is 0.001% to 0.090%. , S is 0.0001% or more and 0.0050% or less, sol.Al is 0.005% or more and 0.065% or less, and, if necessary, at least one of Cr, Mo, Nb, V, Ni, Cu, and Ti is each 0.5% or less, Additionally, if necessary, there may be an example where B and Sb are each 0.01% or less, and the balance is Fe and inevitable 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.

Example 1

An embodiment of the present invention is described. As an example of the present invention, using the quenching device (1) related to the embodiment of the present invention, quenching of a high-strength cold-rolled steel sheet with a tensile strength of 1470 MPa class with a sheet thickness t of 1.0 mm and a sheet width of 1000 mm is performed. It was carried out. The composition of the high-strength cold-rolled steel sheet with a tensile strength of 1470 MPa class was set as 0.20% by mass, 1.0% Si, 2.3% Mn, 0.005% P, and 0.002% S. The temperature TMs of the Ms point of the high-strength cold rolled steel sheet is 300°C, and the temperature TMf of the Mf point is 250°C. Therefore, the target temperature T2 when passing the constraint roll 20 can be set in the range of 450°C to 100°C, and the target temperature T2 is set to 400°C. Additionally, the cooling start temperature T1 was set to 800°C, and the target temperature T2 was set to 400°C. The temperature of the cooling fluid (CF) was 30°C, and the cooling rate CV was set to 1500 (°C/s).

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

FIG. 3 is 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 plate as the metal plate S in the example of the present invention. . As shown in FIG. 3, even if the conveyance speed v changes, by moving the restraint roll 20 according to the conveyance speed v and changing the distance d, the temperature (°C) at the time of passage of the restraint roll 20 is the target temperature of 400. All could be controlled at ±25°C. As a result, as shown in FIG. 4, the amount of warpage of the steel plate was reduced to 10 mm or less. As a result, the deviation in the amount of bending, that is, the difference between the maximum and minimum values, was suppressed to 4.2 mm.

FIG. 5 is a graph showing the relationship between the conveyance speed v and the target temperature in Comparative Example 1, and FIG. 6 is a graph showing the relationship between the conveyance speed v and the amount of bending of the steel plate as the metal plate S in Comparative Example 1. . As Comparative Example 1, a quenching device with a fixed constraint roll 20 similar to that in Patent Document 1 was used, and other conditions were the same as those of the above-mentioned invention example. In Comparative Example 1, the distance d (mm) from the cooling start position to the constraint roll 20 was kept constant at d = 400 mm.

In Comparative Example 1, as shown in FIG. 5, the temperature (°C) at the time of passage of the constraint roll varied greatly depending on the conveyance speed v (mm/s) and was not controllable. Therefore, under conditions other than v = 1000 mm/s and v = 1500 mm/s, the temperature (°C) when passing the constraint roll 20 was outside 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 deflection of the steel sheet was all 10 mm or more, and the deformation suppression effect was insufficient. As a result, the deviation, which is the difference between the maximum and minimum values of the amount of bending, increased to 10.3 mm.

FIG. 7 is a graph showing the relationship between the conveyance speed v and the target temperature in Comparative Example 2, and FIG. 8 is a graph showing the relationship between the conveyance speed v and the amount of warpage of the steel plate as the metal plate S in Comparative Example 2. . As Comparative Example 2, as shown in Patent Document 2, the movable masking was moved while the constraint 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, and the above high-tensile strength cold-rolled steel sheet was manufactured.

As shown in FIG. 7, in Comparative Example 2, regardless of the steel sheet manufacturing conditions such as conveyance speed v (mm/s), the temperature (°C) at the time of passage of the restraining roll 20 changes significantly and cannot be controlled. There wasn't. Therefore, in all conditions, the temperature (°C) at the time of passing the restraint roll was outside the range of 450°C to 100°C. And, as shown in FIG. 8, the amount of warpage of the steel plate was 10 mm or more, and the deformation suppression effect was insufficient. As a result, the deviation in the amount of bending (difference between the maximum and minimum values) increased to 9.2 mm.

Additionally, the embodiment of the present invention is not limited to the above embodiment, and various changes can be added. For example, in the above embodiment, the case where the target temperature T2 is (TMs+150) (°C) to (TMf-150) (°C) is exemplified, but it is not limited to this. In the case where there is no variation in the shape of the metal plate S, such as the amount of warpage, for example, in terms of processing in the post-process or ensuring freedom of operation, the target temperature T2 is set to (TMs+150) (°C) to (TMf). There is no need to limit it to -150) (℃).

In this case, the target temperature T2 is set in advance in consideration of the predicted shape (e.g., amount of deflection), and the position of the restraining roll 20 is adjusted, keeping in mind the processing in the post-process and securing the freedom of operation, etc. The distance d from the cooling start position to the constraint roll 20 is controlled by . Then, the temperature of the metal plate S when passing the constraint roll 20 is set to a predetermined temperature T2, and the shape (e.g., amount of deflection) of the metal plate S is set to the same level, for example, as defined in FIG. 2. It is sufficient to ensure that the deviation in the amount of deflection is within 4 mm.

In addition, the restraining roll 20 is not limited to one pair, and may be formed in multiple pairs or in multiple pieces. In that case, the position of the entire pair of restraint rolls may be controlled at once, or a mechanism may be used to control the position and opening and closing for each of the plurality of restraint rolls.

1: Metal plate quenching device
10: Cooling device
11: cooling tank
12: nozzle
20: Restraint Roll
30: roll moving device
40: movement control device
BD: Transport direction
CF: Cooling fluid
S: metal plate

Claims (15)

A metal plate cooling device that cools the metal plate while transporting it,
a cooling device that cools the metal plate being transported;
a restraining roll that conveys the metal plate cooled by the cooling device while restraining it in the thickness direction;
a roll moving device that moves the constraint roll along a conveyance direction of the metal plate;
A quenching device for a metal plate, comprising a movement control device that controls the operation of the roll movement device to adjust the position of the constraint roll. According to claim 1,
The cooling device is a quenching device for a metal plate, including a plurality of nozzles that spray cooling fluid on the metal plate to cool it. The method of claim 1 or 2,
The cooling device is a metal plate quenching device that has a cooling tank for cooling the metal plate by immersing it. The method according to any one of claims 1 to 3,
The movement control device controls the operation of the roll moving device to position the restraint roll so that the restraint roll restrains the metal plate at a position where the metal plate reaches the target temperature. According to claim 4,
The target temperature is (TMs+150) (°C) when the temperature at the Ms point where the martensite transformation of the metal plate starts is TMs (°C), and the temperature at the Mf point where the martensite transformation ends is TMf (°C). ) A quenching device for metal plates set to a temperature range of (TMf-150) (°C). The method of claim 4 or 5,
The movement control device determines the distance from the cooling start position by the cooling device to the constraint roll, the conveyance speed of the metal plate, the cooling start temperature of the metal plate at the start of cooling by the cooling device, and the target temperature. and a metal plate quenching device that sets the cooling rate of the metal plate and moves the position of the constraint roll to a set distance. According to claim 6,
The movement control device sets the conveyance 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 rate of the metal plate by the cooling device to CV ( A quenching device for a metal plate in which the distance d (mm) from the cooling start position to the constraint roll is determined from equation (1) when expressed in °C/s).
d = (T1-T2)×v/CV (1) According to claim 7,
In the movement control device, the cooling rate CV is set as CV = α/t by a coefficient α representing the cooling condition of the metal plate and the plate thickness t of the metal plate. As a method of cooling a metal plate while transporting the metal plate,
When restraining the cooled metal plate in the thickness direction with a restraining roll, the restraining roll is moved along the conveyance direction of the metal plate so as to restrain the metal plate at the position where the metal plate is at the target temperature. Ching method. According to clause 9,
The target temperature is (TMs+150) (°C) when the temperature at the Ms point where the martensite transformation of the metal plate starts is TMs (°C), and the temperature at the Mf point where the martensite transformation ends is TMf (°C). ) A method of quenching a metal plate, set in a temperature range of (TMf-150) (°C). According to claim 9 or 10,
The movement of the restraint roll is based on the conveyance speed of the metal plate, the cooling start temperature of the metal plate at the start of cooling, the target temperature, and the cooling rate of the metal plate, and the distance from the cooling start position to the restraint roll. Set ,
A method of quenching a metal plate, which is carried out by moving the constraint roll to reach a set distance. According to claim 11,
The distance from the cooling start position to the constraint roll is v (mm/s) as the conveyance speed of the metal plate, T1 (°C) as the cooling start temperature, T2 (°C) as the target temperature, and CV as the cooling rate of the metal plate. A method of quenching a metal plate in which the distance d (mm) from the cooling start position to the constraint roll is determined from equation (1) when expressed in (°C/s).
d = (T1-T2)×v/CV (1) According to claim 12,
The cooling rate CV is set as CV = α/t by the coefficient α representing 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 metal plate quenching method 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 any of hot-dip galvanizing treatment, electrogalvanizing treatment, or alloyed hot-dip galvanizing treatment.

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