KR20240021272A - Quenching equipment for metal plates, continuous annealing equipment, quenching methods for metal plates, manufacturing methods for cold rolled steel sheets, and manufacturing methods for plated steel sheets. - Google Patents

Abstract

Metal sheet quenching equipment, continuous annealing equipment, metal sheet quenching method, cold rolled steel sheet manufacturing method, and plated steel sheet manufacturing that suppress shape defects that occur in metal sheets during quenching, regardless of sheet speed or sheet thickness. Provides a method. A metal plate cooling device having a water tank for cooling the metal plate through which the plate is passed by immersing it in a liquid, a water spray device formed on the water tank, and a plurality of pairs of restraint rolls for restraining the metal plate through the inside of the water tank, wherein the water spray device is It has a plurality of water spray nozzles installed so that cooling water is sprayed in opposition across the front and back surfaces of the metal plate along the sheet-threading direction of the metal plate, and the plurality of constraint roll pairs each independently position themselves relative to the metal plate based on operating conditions. Adjust.

Description

Quenching equipment for metal plates, continuous annealing equipment, quenching methods for metal plates, manufacturing methods for cold rolled steel sheets, and manufacturing methods for plated steel sheets.

The present invention relates to a continuous annealing equipment that performs annealing while continuously sheeting a metal plate, a metal plate annealing device that suppresses shape defects occurring in the metal plate during annealing, a continuous annealing facility, and a metal plate annealing method. , relates to a manufacturing method of cold rolled steel sheet and a manufacturing method of plated steel sheet.

In the production of metal plates, including steel plates, the material is manufactured by heating and then cooling the metal plate in a continuous annealing facility to cause a phase transformation. Recently, in the automobile industry, the demand for thinned high-strength steel sheets (HITEN) has been increasing for the purpose of reducing the weight of the car body and achieving both crash safety. For this reason, the importance of rapid cooling technology, which is advantageous for manufacturing high-strength steel sheets, is increasing. Among various cooling methods, the water cooling method is widely used because it can achieve high cooling rates at low cost. However, due to rapid cooling, differences in temperature distribution are likely to occur within the steel sheet, and shape defects due to out-of-plane deformation such as bending or corrugation may occur in the steel sheet, which is a problem. In order to prevent shape defects in such steel sheets during water quenching, various methods have been proposed in the past.

In Patent Document 1, in order to suppress wavy deformation of a metal plate that occurs during quenching and quenching in a continuous annealing furnace, a bridle roll is used as a tension changing means that can change the tension of the steel sheet applied to the quenching and quenching process. A method of rapid cooling and forming before and after cooling has been proposed.

In Patent Document 2, attention is paid to the fact that at the quenching start point (cooling start point), thermal stress in the compression direction occurs in the width direction of the metal sheet, causing the metal sheet to buckle, thereby causing shape defects, and it is noted that by cooling, heat stress in the compression direction occurs in the width direction of the metal sheet, causing shape defects to occur in the sheet width direction due to cooling. A method has been proposed to suppress out-of-plane deformation by restraining the metal plate from both sides in the area where compressive stress is occurring or the area near it.

Additionally, in Patent Document 3, if the temperature at the Ms point where the martensitic transformation of the metal sheet starts is TMs °C, and the temperature at the Mf point where the martensitic transformation ends is TMf °C, the metal sheet in rapid cooling is called a metal plate. In the temperature range of TMs + 150°C to TMf - 150°C, a method of restraining by a set of restraining rolls formed in the cooling liquid has been proposed.

In addition, in Patent Document 4, a water tank containing a liquid for immersing a metal plate, a spray device provided with a plurality of nozzles for spraying liquid on the front and back surfaces of the metal plate, and one or more pairs of restraint rolls for restraining the metal plate A method or device has been proposed that includes and sprays liquid from all nozzles of the jet device in the direction of the restraint roll.

Japanese Patent Publication No. 2011-184773 Japanese Patent Publication No. 2003-277833 Japanese Patent Publication No. 6094722 Japanese Patent Publication No. 6477852

However, none of the methods disclosed in Patent Documents 1 to 4 take into account the sheet thickness of the metal sheet or the sheet speed in the water tank for restraining the metal sheet in the constraining roll, and the temperature of the metal sheet is TMs + 150 ° C. to TMf. - In the range of 150°C, there is a problem that restraint by restraint rolls cannot be performed. As a result, there is a problem that shape defects occur after quenching the metal plate.

The present invention was made in consideration of these circumstances, and provides a metal sheet quenching device, continuous annealing equipment, and a metal sheet quenching method that suppress shape defects occurring in a metal sheet during anneal, regardless of the sheet speed or sheet thickness. The purpose is to provide a method of manufacturing a cold rolled steel sheet and a method of manufacturing a plated steel sheet.

The main structure of the present invention for solving the above problems is as follows.

[1] A metal plate quenching device having a water tank for cooling a metal plate through which a plate is passed by immersing it in a liquid, a water spray device formed on the water tank, and a plurality of pairs of restraint rolls for restraining the metal plate through the inside of the water tank. As such, the water spray device has a plurality of water spray nozzles installed so that cooling water is sprayed in opposition across the front and back surfaces of the metal plate along the sheet-through direction of the metal plate, and the plurality of constraint roll pairs are based on operating conditions. Thus, a metal plate quenching device that independently adjusts the position of the metal plate.

[2] The metal plate quenching device according to [1], wherein the plurality of constraint roll pairs have maximum and minimum surface maximum height roughness Rz values of 5 μm or more and 50 μm or less, respectively.

[3] The metal plate quenching device according to [1], wherein the constraint rolls of the plurality of constraint roll pairs have a roll diameter of 50 mm or more and 250 mm or less.

[4] The plurality of pairs of restraint rolls are arranged so that, when the roll diameter is D mm, the distance between the central axes of a pair of restraint rolls facing each other with the metal plate in between is D × 1/4 mm or more and D mm or less. A quenching device for metal plates described in [1].

[5] A continuous annealing facility in which the metal plate quenching device according to any one of [1] to [4] is provided on the exit side of the crack zone.

[6] After the continuously rolled metal plate is immersed in a liquid and cooling is started, the temperature of the metal plate is in the range of the martensite transformation start temperature of the metal plate + 150°C or less and the martensite transformation end temperature - 150°C or more. A method of fastening a metal plate, wherein the metal plate is restrained using a plurality of restraint roll pairs whose positions relative to the metal plate are adjusted.

[7] A method of producing a cold-rolled steel sheet, in which the cold-rolled steel sheet is quenched by the metal sheet quenching method described in [6].

[8] A method for manufacturing a plated steel sheet, wherein the cold rolled steel sheet is subjected to a plating treatment following the method for manufacturing the cold rolled steel sheet described in [7].

[9] The method for producing a plated steel sheet according to [8], wherein the plating treatment is performed by any one of electro-galvanizing treatment, hot-dip galvanizing treatment, and alloyed hot-dip galvanizing treatment.

According to the metal plate quenching device, the metal plate quenching method, and the steel sheet manufacturing method related to the present invention, shape defects occurring in the metal plate during quenching can be suppressed, regardless of the sheet speed or sheet thickness.

1 is a schematic diagram showing the configuration of the quenching device of the present invention.
Fig. 2 is a schematic diagram showing the configuration of a pair of constraining rolls of the quenching device of the present invention.
Fig. 3 is a schematic diagram showing the arrangement configuration of the constraint roll of the present invention.
Figure 4 is a schematic diagram showing the bending of a metal plate.
Figure 5 is a schematic diagram showing the configuration of a conventional quenching device.

Hereinafter, an embodiment of the present invention will be described using the drawings. Hereinafter, the case of using inexpensive and industrially useful water as the cooling medium will be described, but the cooling medium is not particularly limited as long as it is a liquid that can be used for cooling.

1 is a diagram showing a quenching device 1 for a metal plate S according to an embodiment of the present invention. The quenching device 1 is applied to a cooling facility formed on the exit side of the crack zone of a continuous annealing furnace (continuous annealing facility). The cooling device 1 has a water spray device 3 such that a part of the water spray nozzle 3a is exposed upward from the water surface (W in the drawing) to the water tank 2 that accommodates the water provided for cooling. is formed The water spray device 3 has a feed direction of the metal plate S in which the water spray nozzle 3a continuously passes through the inside of the water tank 2 with a predetermined gap with respect to the front and back surfaces of the metal plate S. A plurality of pairs are arranged along (arrow P in the drawing), and a plurality of constraint roll pairs 4 are arranged along the way. In addition, although four constraint roll pairs 4 are shown in FIG. 1, there is no restriction as long as there are two or more, that is, two or more pairs. These plurality of constraint roll pairs 4 may have a control device for adjusting the position with respect to the metal plate S based on operating conditions.

The metal plate (S) may require quenching at the exit side of the continuous annealing furnace in order to obtain the desired quality. However, it is known that rapid cooling during quenching causes heat shrinkage and the shape becomes distorted. In particular, when the metal plate (S) undergoes martensitic transformation, rapid thermal contraction and transformation expansion occur simultaneously in the range from the martensite transformation start temperature (TMs ℃) to the martensite transformation end temperature (TMf ℃), , the stress acting within the metal plate S becomes maximum, and the shape of the metal plate S collapses. In addition, the temperatures of TMs°C and TMf°C can be calculated from the component composition of the metal plate (S).

In particular, if the temperature of the metal plate (S) during rapid cooling by quenching can be physically restrained in a temperature range of TMs + 150 ° C. or lower and TMf - 150 ° C. or higher, the shape can be stabilized. And, the range of TMs + 100°C or less and TMf - 100°C or more is more preferable.

In response to this, a technique has been proposed that uses a pair of restraining rolls 4 formed to sandwich the plate surfaces of the metal plate S during immersion in cooling water in a temperature range that causes martensitic transformation. However, with only one simple configuration, that is, one pair of restraining roll pairs (4), the sheet speed and plate thickness of the metal plate (S) are limited in order to maintain the temperature of the metal plate (S) during restraining in an appropriate range. It was necessary to do it. Therefore, in the present invention, attention is paid to forming a plurality of restraining roll pairs 4 in the cooling water.

In the present invention, as shown in FIG. 1, by forming a plurality of restraining roll pairs 4, the distance at which the metal plate S can be restrained becomes longer, and even if there is an increase or decrease in the sheet speed or a change in the plate thickness, the restraint roll can be secured reliably. It can be restrained in the temperature range of TMs + 150 ℃ or lower and TMf - 150 ℃ or higher. If restrained outside the temperature range, expansion due to transformation cannot be suppressed and the shape of the metal plate S is disturbed. In addition, since the sheet thickness and sheeting speed of the metal sheet (S) vary depending on the product specifications, heating of the continuous annealing furnace, and cracking ability, the number of restraining roll pairs (4) depends on the sheeting speed or sheet thickness of the metal sheet (S). When changes, at least two or more restraining roll pairs (4) may form a number of restraining roll pairs (4) capable of restraining in the temperature range of TMs + 150°C to TMf - 150°C.

In the present invention, cooling is promoted using a water spray device (3) having a plurality of water spray nozzles (3a). As shown in FIG. 1 , the water spray device 3 comprised of a plurality of water spray nozzles 3a is disposed in a range extending from just above the water surface W to underwater. The water jet nozzle 3a is disposed at a position away from the metal plate S relative to the constraint roll pair 4. The distance between the water spray nozzle 3a and the metal plate S is not particularly limited, but if it is close, there is a risk of contact due to the influence of bending or vibration of the steel plate (metal plate S), and conversely, if it is far away, the steel plate (metal plate (S) It is necessary to be careful because the flow rate at the time of reaching S)) may become slow and the cooling capacity may decrease. The position where the refrigerant (3b in the drawing) sprayed from the water jet nozzle 3a located at the uppermost part of the water jet device 3 collides with the metal plate S, that is, the jet collision position is above the water surface W. It is located at a distance (A in the drawing), and the height is preferably 10 mm.

In addition, if the jet collision position is too close to the water surface (W), the influence of the change in the position of the water surface (W) also affects the jet collision position, which destabilizes the vapor film removal position and greatly affects the cooling capacity. It is inappropriate because On the other hand, if it is too far from the water surface W, the water temperature rises during the flow of the water stream after the water jet, the cooling ability of the lower part decreases, and the water becomes boiling, so it is unsuitable. Therefore, the distance between the water surface (W) and the jet collision position, represented by the distance (A), is preferably about 5 to 50 mm (or 10 mm).

Conventionally, in order to suppress a decrease in the cooling rate of the metal plate S, when water is sprayed toward the point where the restraint roll pair 4 and the metal plate S are in contact (hereinafter referred to as "when rolling"), the restraint roll pair 4 Immediately next to (4), it has been recommended to arrange the water spray nozzle 3a at an angle (see Fig. 5).

However, since the equipment (water tank 2) becomes bulky when the nozzles are arranged at an angle as shown in FIG. 5, the necessary conditions were closely investigated by conducting experiments and the like. As a result, it was found that the cooling rate slows down during rolling only when a vapor film remains, and when there is no vapor film, the cooling rate is hardly observed to decrease. In particular, in the quenching of the metal plate (S) of the high-strength steel sheet targeted in the present invention, the martensite transformation start temperature (TMs °C) is about 400 °C, and the martensite transformation end temperature (TMf °C) is about 300 °C. That's about it. Therefore, it is assumed that the temperature range when restraining with the restraining roll pair 4 during binding is approximately 150°C to 550°C. This temperature range corresponds to the transition boiling region from the nucleate boiling region, and the vapor film either does not exist (nucleate boiling) or is in a highly unstable state (transition boiling). Therefore, if a small amount of water is sprayed, the vapor film can be destroyed, and there is no need to set the nozzle at an angle toward the restraining roll pair, so there is no problem even if the water is sprayed perpendicularly to the metal plate S.

And, these conditions are satisfied when the target material is a metal plate (S) having a martensite transformation start temperature (TMs°C) of 450°C or lower, preferably 400°C or lower.

As has been pointed out in the past, in the case of roll restraint at a high temperature, if the vapor film is not removed, the cooling rate during roll will decrease significantly, but it is preferable not to restrain within this temperature range, and it is not a problem.

Therefore, in the present invention, the pair of restraint rolls 4 each independently forms a moving mechanism that moves in the direction of press-fitting the metal plate S or in the direction away from the metal plate S, and uses the water spray nozzle 3a to spray the water. Even if the coolant is arranged to face the front and back of the metal plate (S), a stable cooling state can be obtained. In order for the coolant sprayed from the water spray nozzle 3a to be sprayed so as to face the metal plate S, it is necessary to arrange the water spray nozzle 3a approximately perpendicular to the plate direction of the metal plate S. . This "approximately vertical" is, specifically, if the inclination angle of the water spray nozzle 3a with respect to the metal plate S is θ, θ is 80° or more and 100° or less, and preferably 82° or more and 98° or less. , more preferably 87° or more and 93° or less.

Specifically, the pair of restraint rolls 4 at the point where the temperature of the metal plate S reaches a temperature range at which there is a risk of transient boiling is withdrawn, and the remaining pair of restraint rolls 4 is used to restrain the metal plate. Additionally, the pair of constraint rolls 4 may have a mechanism that moves individually, or may be a mechanism that moves for each roll (constraint roll 4a) rather than a pair.

Here, which constraint roll pair is to be retracted or used can be determined depending on the operating conditions. Operating conditions refer to heat treatment conditions and cooling conditions, and in particular, the sheet speed, sheet thickness, quenching start temperature, and “bend” of the metal sheet are items that have a large influence. At least among the same steel types, when the heat treatment conditions before quenching and the distance from the end of heat treatment to the start of cooling are the same, it is preferable to make decisions based on the sheet speed and sheet thickness. The method of determining the pair of constraining rolls to be used is not only the method described above (the position within the suitable temperature range described in paragraph 0018 is derived based on the sheet speed and sheet thickness to determine the pair of constraining rolls), but also the operating conditions and the method used. By accumulating data on whether the shape is stable when the constraint roll pair is changed, a preferable constraint roll pair may be selected and used.

In short, regarding the quenching treatment of the metal plate S, by adjusting the positions of the plurality of restraining roll pairs 4 with respect to the metal plate S based on the sheet speed or plate thickness as the operating conditions, TMs + 150 are guaranteed. It becomes possible to restrain the metal plate (S) in a suitable temperature range of ℃ or lower and TMf - 150 ℃ or higher. The operating conditions may be the sheet speed or the sheet thickness, but the product of the sheet speed and the sheet thickness (hereinafter referred to as “LSD”) may be used. In this case, either the sheet speed or the sheet thickness fluctuates (increases or decreases). ), LSD also changes. Adjustment of the positions of the plurality of constraint roll pairs 4 includes, as conditions for adjustment of the constraint roll pairs 4, “the constraint roll pair to be used,” “the distance between the constraint roll pairs,” the “intermesh amount” and “offset amount” described later. Includes adjustments, etc.

In the case of a method of improving the shape by roll restraint, scratches resulting from roll slip may occur. This is because the water stream collides with the metal plate S in a turbulent state, which may cause the metal plate S to vibrate violently, and the water film is likely to squeeze in between the restraining roll 4a and the metal plate S, so to speak. It is thought that slip may be caused by the hydroplaning phenomenon. As a countermeasure to the former, it is preferable to restrain the metal plate S by a plurality of restraining roll pairs 4, and thereby the vibration level can be significantly improved. Additionally, as a countermeasure to the latter, if the maximum height roughness (Rz) of the surface of the restraining roll 4a is roughened to 5 μm or more, the drainage performance is improved and slip can be prevented.

However, if Rz is above a certain level, the anti-slip effect reaches its limit and scratches due to roughness are likely to occur, so the upper limit is set to 50 μm or less. In addition, the maximum height roughness (Rz) is specified in the Japanese Industrial Standard "JIS B 0601 Surface roughness (2001)", is calculated by measurement based on "JIS B 0633", and is measured in the width direction of the metal plate (S). It is a value measured with a two-dimensional illuminometer in the corresponding direction, that is, in the longitudinal direction of the constraint roll 4a. Additionally, the method may be non-contact or contact, as long as it is a measuring device that can obtain measurement results that satisfy “JIS B 0601 Surface Roughness”.

There is also a preferable range for the diameter of the constraint roll 4a (diameter D mm) for the following reasons. When the roll diameter of the restraining roll 4a is large, the water flow becomes unstable because interference with the water flow becomes large, the situation of vapor film removal becomes unstable, and as a result, the shape of the metal plate S becomes unstable. Additionally, as the roll diameter increases, the distance over which the refrigerant flow is blocked by the roll becomes longer, making it difficult to secure the cooling length, which is not preferable. Therefore, the roll diameter is preferably 250 mm or less. On the other hand, if it is too small, roll bending occurs when the metal plate S is restrained, and the force restraining the metal plate S is weakened, so that the shape improvement effect cannot be exhibited. Therefore, the roll diameter is preferably 50 mm or more.

Here, Fig. 2 and Fig. 3 show an example of the arrangement configuration of the restraining roll pair 4. The pair of restraint rolls 4, which are set to face each other from the front and back sides of the metal plate S, are preferably arranged (offset) so that the central axis of each restraint roll 4a is shifted in the sheet-feeding direction P of the metal plate S. do. At this time, it is not necessary to shift all the restraint rolls 4a in the same direction, and which restraint roll 4a is shifted vertically may be changed for each restraint roll pair. If the central axes are the same, the metal plate S cannot be press-fitted, but if the central axes are arranged misaligned, the press-fitting amount becomes variable and the restraining force increases. However, if the distance between the central axes of each pair of restraining rolls 4a, that is, the offset value (B in the drawing), becomes too large, the corresponding points on the metal plate S cannot be restrained on the front and back simultaneously, and the restraining effect cannot be achieved. There will be no more. For this reason, the distance (offset value) between the central axes of a pair of front and back constraining rolls 4a is preferably D x 1/4 mm or more and D mm or less. Additionally, D is the diameter (mm) of the restraining roll 4a as described above. If it exceeds D mm, it is possible to increase the press amount of the roll, but the roll restraint effect is not obtained. In other words, the correction effect cannot be obtained by applying bending and bending restoration forces to the plate almost simultaneously. On the other hand, if it is less than D Do something like that.

In addition, the movement amount I (IM; intermeshing) of the restraining roll pair 4 in the direction of press-fitting the metal plate S is not particularly limited, and the strength and arrangement of the restraining metal plate S, and the restraining roll pair 4 ) You can set the optimal range for each pair of constraint rolls according to the number of. However, if the amount of movement in the press-fitting direction is small, slip is likely to occur and the risk of scratching increases. On the contrary, if it is large, it may encourage shape defects, so there is an appropriate value. When a steel plate is used as the metal plate S, when the plate thickness is set to t mm, the movement amount of the pair of restraining rolls 4 in the direction of press-fitting the metal plate S is in the range of -t to +10 × t mm. desirable. Here, if explained specifically using FIG. 3, as the movement amount I of the constraint roll 4a with respect to the metal plate S, as shown in the state of -t mm (see FIG. 3(a)), -t mm. If it is less than this, the restraining effect of the metal plate S will not be obtained. In addition, as shown in the state of +10 There is a risk that the bite may become too strong and that mail-ordering will not be possible.

The position of the pair of restraint rolls 4 may be adjusted using information on the bending of the metal plate S. The warpage information of the metal plate S may be a predicted value or a measured value, and is not particularly limited. When measuring the bending of the metal plate S, there are three patterns as the bending measurement positions: in front of the water tank 2, behind the water tank 2, and off-line, and any combination may be used. To measure the bending in the metal plate S, a laser rangefinder or the like may be used. Measurement before cooling of the metal plate S has the advantage of being able to determine the conditions of the constraint roll pair 4 (constraint roll pair to be used, distance between constraint roll pairs, amount of intermesh, amount of offset, etc.) of the constraint roll pair 4 without delay. If the measurement is made after the metal plate S has cooled, a delay in setting due to a time difference is inevitable, but since the adjustment is based on the actual bending information of the metal plate S, accurate adjustment of the restraining roll pair 4 becomes possible. . Off-line measurement of the deflection of the metal plate S has the advantage of increasing the delay in setting the pair of restraint rolls 4 and also allowing measurement by hand.

In short, regarding the quenching treatment of the metal plate S, a plurality of restraining roll pairs (4 ) You can adjust the position of . Also, in this case, the adjustment of the positions of the plurality of constraint roll pairs 4 is based on the conditions for adjustment of the constraint roll pairs 4, such as “constraint roll pair to be used,” “distance between constraint roll pairs,” and “intermesh amount.” and “offset amount,” etc. may be adjusted.

In addition, the distance between the restraint roll pairs 4 (C in FIG. 2) is the center of the restraint roll 4a provided below the upper restraint roll pair 4 among the adjacent restraint roll pairs 4 and the lower It means the distance between the centers of the restraint rolls (4a) installed on the upper side of the restraint roll pair (4).

Since it is assumed that the restraining rolls 4a in the restraining roll pair 4 have a mechanism to move toward or apart from each other with respect to the plate direction P of the metal base S, the roll pair is When retreating, strictly speaking, the distance between the constraint roll pairs 4 is doubled, and the number of constraint roll pairs 4 is halved. However, if the initial distance C between the pair of restraint rolls 4 is not appropriately set in advance, the shape correction effect cannot be obtained.

The appropriate range for the distance (C) is D mm or more and 10 × D mm or less. If the distance C between the pair of restraint rolls 4 is less than D mm, the water ejected from the water spray nozzle 3a will be blocked by the pair of restraint rolls 4 before it reaches the metal plate S, thereby ensuring sufficient Cooling ability cannot be obtained, the distance required for shape correction becomes long, and the device becomes large, which is not desirable. Additionally, since the contact point between the metal plate S and the restraining roll pair 4 increases, the risk of surface scratches such as press scratches and slip scratches also increases. On the other hand, when it is larger than 10 The effect that formed is not obtained.

The material of the restraining roll 4a may be formed of a material that has excellent thermal conductivity and has a strength that can withstand the load when pinching the metal plate. Examples include heat-resistant steel (e.g. KHR12C), stainless steel (SUS304, SUS310), ceramic, etc. However, CFRP material, which has a small roll deflection even with a small diameter, is easy to obtain a roll restraint effect, and is especially used to secure cooling ability. It is advantageous in this case.

As described above, the purpose of the present invention is to reduce the complex and uneven uneven shape that occurs when martensitic transformation occurs and the structure expands in volume during rapid cooling of the metal plate (S), and is used in the manufacture of cold rolled steel sheets. It is desirable to apply the method. In addition, plating treatment may be continuously applied to the cold rolled steel sheet. The plating treatment may be performed by any of electrogalvanizing treatment, hot-dip galvanizing treatment, or alloyed hot-dip galvanizing treatment.

More specifically, it is preferable to apply it to the production of high-strength steel sheets (high tensile strength) with a tensile strength of 580 MPa or more. The upper limit of the tensile strength is not particularly limited as long as the roll material, etc. can be adapted to high strength, but if it is stainless steel (SUS304, SUS310), ceramic, etc., the effect can be expected even if the tensile strength is around 3000 MPa.

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 short, continuous annealing using a quenching device and a quenching method is performed on the metal sheet (S) according to the present invention to produce high-strength cold-rolled steel sheets, hot-dip galvanized steel sheets, electro-galvanized steel sheets, and alloyed hot-dip galvanized steel sheets. It is desirable to do

As a specific example of the composition of the high-strength steel sheet, in mass%, C is 0.04% or more and 0.25% or less, Si is 0.01% or more and 2.50% or less, Mn is 0.80% or more and 3.70% or less, P is 0.001% or more and 0.090% or less, and 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 type of Cr, Mo, Nb, V, Ni, Cu, and Ti is 0.5% or less each, also necessary Accordingly, examples include B and Sb each being 0.01% or less, and the remainder being Fe and inevitable impurities.

Additionally, the embodiment of the present invention can be applied to rapid cooling of the entire metal plate. In addition, the present invention is not limited to water immersion cooling as an example, but is applicable to all applications regardless of heating or cooling as a means of physically restraining and preventing steel sheet deformation caused by transformation.

Example

Hereinafter, an example in which a metal plate is manufactured using the metal plate quenching device, the metal plate quenching method, and the steel plate manufacturing method according to the present embodiment will be described.

Using the quenching device 1 shown in Figure 1 as a base, a high-strength cold-rolled steel sheet (metal sheet (S)) with a sheet thickness of 1.0 to 2.3 mm and a sheet width of 1000 mm and a tensile strength of 1470 MPa class is manufactured at a sheet speed (“in Table 1”). LS”), 60 to 108 mpm, quenching start temperature of 800°C, cooling water injection amount of 1000 T/hr, and water temperature of 30°C. In addition, four pairs of restraining rolls 4 represented by the quenching device 1 shown in FIG. 1 are arranged in the vertical direction, but in this example, 1 to 3 pairs are arranged in the vertical direction.

Here, the representative components of the high-strength cold-rolled steel sheet with a tensile strength of 1470 MPa class are 0.20% by mass, 1.0% Si, 2.3% Mn, 0.005% P, and 0.002% S. In addition, the temperature (TMs °C) of the Ms point of the high-strength cold-rolled steel sheet is 400 °C, and the temperature (TMf °C) of the Mf point is 300 °C. In this case, the plate temperature range in which restraint by the restraint roll pair 4 is effective is 150°C to 550°C.

And the roll diameter D of the constraint roll 4a was set to 150 mm. The central axes of each restraint roll (4a) in the restraint roll pair (4) were arranged to be offset by 75 mm (B = 75 mm in Fig. 2) in the sheet-through direction (see “Offset Value” in Table 1), but the offset occurred under some conditions. The values were changed (invention examples 7 to 10). The position of the restraint roll pair 4 is set at 0 m in the water surface W, and for invention examples 1 to 14, the position is 0.3 m (first restraint roll pair) and 0.75 m (second restraint roll pair) in the sheet-through direction P, respectively. ) were installed at each location. That is, C in FIG. 2 is 0.45 m. Invention examples 15 and 16 are examples in which a constraint roll pair was further added at the position of 1.05 m (third constraint roll pair). Each pair of restraint rolls (4) is capable of retraction (corresponds to I.M -50 mm in Table 1. - means the retraction direction (direction away from the metal plate (S))), depending on the conditions. It is possible to change use or disuse (roll movement). In short, I.M "-50.0 mm" in Table 1 indicates that the corresponding constraint roll pair 4 is completely separated from the metal plate S and has no constraint effect on the metal plate S. In addition, I.M in Table 1 corresponds to I in FIG. 3.

In addition, when using the constraint roll pair 4 by press-fitting it into the metal plate S without retracting the constraint roll pair 4, the press-fitting amount into the metal plate S was set to 0 mm as a basis. In short, when I.M is “0.0 mm” in Table 1, the pair of restraining rolls 4 is press-fitted into the metal plate S. More specifically, the state in which I.M becomes “0.0 mm” is a state in which the position of the surface of the pair of constraint rolls 4 (constraint rolls 4a) is adjusted until it reaches the center position of the metal plate S. means. In other words, the state in which I.M is “0.0 mm” is a state in which the surface of the pair of constraint rolls 4 (constraint rolls 4a) is press-fitted at a distance of 1/2 the thickness of the metal plate S. it means. On the other hand, in the conditions of Invention Example 7 and Invention Example 9, the press amount was changed. In this condition, since the height of the restraining rolls 4a on the front and back of the metal plate S is the same (offset value is 0), physical press fit is not possible, and theoretically, half of the plate thickness is in the - direction from the pass line. You can set it deviated from , but since there is a possibility of overload, a margin value was taken and set.

The evaluation in the examples was evaluated from two viewpoints: the amount of warpage (mm) and surface quality of the metal plate S after cooling. The amount of deflection of the metal plate S was measured as the amount of deflection (K in the figure) of the metal plate S in the width direction of the metal plate S, as shown in FIG. 4 . In addition, the surface quality of the metal plate S was examined by taking a total of three samples of the plate width x 1 m in length from the conveyance front end, center part, and rear end of the metal plate S, and observing the external appearance of each. By observing the surface and back of three plates, if a total of 2 or less defects such as surface scratches are found, it is considered good (“○” in Table 1). If a total of 3 or more defects are found, it is considered good (Table 1). It was classified as “×” in 1.

Next, examples related to Comparative Examples 1 to 5 and Invention Examples 1 to 16 shown in Table 1 will be described.

In Comparative Example 1, the metal plate S was cooled without forming the constraint roll pair 4 and setting the spray direction of the water spray nozzle 3a in a direction perpendicular to the sheet direction P of the metal plate S. will be. The amount of bending of the metal plate S was 34.5 mm, and shape defects occurred.

In Comparative Examples 2 to 5, there was one pair of restraint rolls (4), and in Comparative Example 5, the water spray direction was set at 60° with respect to the steel plate. In Comparative Examples 3 and 4, the amount of warpage was improved because the pair of constraining rolls 4 was located within the suitable confinement temperature range derived from the transformation temperature of the metal plate, but in Comparative Examples 2 and 5, the warpage could not be improved. From these results, it can be seen that the single restraining roll pair 4 cannot cope with the change in the product (LSD) of the sheet speed and sheet thickness of the metal sheet S, and the shape deteriorates when the water spray direction is oblique. . The reason is that the actual cooling ability was reduced and the temperature of the metal plate S passing through the pair of restraint rolls 4 increased.

On the other hand, Invention Examples 1 to 6 show the results under the conditions in which two pairs of restraining rolls 4 are arranged. In addition, it was confirmed that Invention Examples 1 to 3 can support a wide range of LSDs by selecting the constraint roll pair 4 used in accordance with the LSD (selecting the state of movement of the constraint roll pair 4). In addition, the metal plate targeted by the present invention is mainly a sheet steel plate, and the cooling situation of the plate can be regulated by LSD. Therefore, as the LSD increases, cooling becomes difficult, and the martensite transformation start and end positions become farther away from the cooling start position, so it is preferable to select the constraint roll pair 4 located below in FIG. 1. Conversely, since cooling becomes easier as the LSD becomes smaller, the martensite transformation start and end positions become closer to the cooling start positions, making it desirable to select the constraint roll pair 4 located at the upper part of FIG. 1.

On the other hand, Invention Examples 4 to 6 used both pairs of restraining rolls 4, and there was a condition in which the warping of the metal plate S worsened. Therefore, in order to cope with changes in the sheet speed and sheet thickness, the retraction function of the constraint roll 4a (the movement function of the constraint roll pair 4) is necessary.

Invention Examples 7 to 14 are based on the conditions of Invention Example 2, and the offset value of the pair of restraint rolls 4 (interval between restraint rolls 4a in the sheet-feeding direction P of the metal band S) , the maximum height illuminance (Rz) of the constraint roll (4a) is changed. When the offset value was set to 0 (Invention Example 7, Invention Example 9), the amount of warpage worsened compared to the result of Invention Example 2 due to restrictions in setting the press amount of the constraint roll 4a as described above. On the other hand, also for Invention Example 8 and Invention Example 10 in which the offset value was 200 mm, the amount of warpage of the metal plate S worsened under the condition that the plate thickness was 1 mm. From this point of view, it was confirmed that the offset value needed to be set appropriately.

Additionally, it was confirmed from Invention Examples 11 to 14 that the appearance of the metal plate S may deteriorate depending on the maximum height roughness Rz of the constraint roll 4a. In order to maintain the appearance of the surface of the metal plate S, it was confirmed that it is preferable to set both the maximum and minimum values of the maximum height roughness Rz to be within the range of 5 μm to 50 μm.

Invention Example 15 is an example in which quenching was performed with reference to Invention Examples 4 to 6. By using a plurality of restraining roll pairs 4, it was possible to obtain a certain degree of correction effect for the metal plate S. Inventive Example 16 changes the rolls used for the plurality of constraint roll pairs 4 based on the measurement results of the product (LSD) of the sheet speed and the sheet thickness of the metal sheet S and the deflection of the metal sheet S. By making adjustments to change the restraining position of the metal plate S and the distance between the restraining roll pairs, the amount of deflection of the metal plate S was able to be suppressed to 3.1 mm. In addition, in this example (invention example 16), the pair of constraint rolls to be used was selected and the distance between the pair of constraint rolls was adjusted accordingly, but the item to be adjusted may be the intermesh amount or the offset amount. To measure the warpage of the metal plate S, a laser displacement meter is installed at a certain position in the sheet-through direction P of the metal plate S, and based on the warpage measurement results from the laser displacement meter, a plurality of restraint roll pairs ( 4) Various conditions may be adjusted.

Regarding the metal plate quenching device, the metal plate quenching method, and the steel plate manufacturing method related to the present invention, the inventors have made extensive studies in order to solve the problems described above. As a result, the following knowledge was obtained.

In order to improve the shape of the metal plate S, the restraining roll 4a is used to prevent out-of-plane deformation of the metal plate S in a temperature range of (T _Ms + 150) (°C) to (T _Mf - 150) (°C). Although restraining is effective, in order to realize the above conditions with only one pair of restraining rolls 4, it was necessary to significantly restrict the sheet speed and plate thickness of the metal plate S. In contrast, when a plurality of constraint roll pairs 4 are employed, it has been thought that the range of conditions for passing the constraint roll pairs 4 within a favorable temperature range can be greatly relaxed.

In this way, in response to changes in the LS, plate thickness, etc. of the metal plate S, a plurality of restraining roll pairs 4 may be provided. However, if the restraining roll pairs 4 are not installed under appropriate conditions, the shape of the metal plate S will not stabilize. There were cases where it did not work, or where scratches, etc. occurred due to the restraining roll pair (4).

It was presumed that the destabilization of the shape of the metal plate S was caused by the instability of the cooling ability, and that this was due to the destabilization of the vapor film removal performance by the water flow. Generally, in water cooling, depending on the temperature range of the metal plate (S), film boiling, transition boiling, and core boiling from the high temperature side, and the contact state (boiling form) of the metal plate (S) and water during cooling change. It was known that the cooling rate and cooling uniformity change accordingly. In addition, in order to realize rapid cooling with high temperature uniformity, it was important to carry out cooling only in the nucleate boiling region, and to achieve this, it was thought that uniform removal of the vapor film was important. In order to realize this, a method of installing slit nozzles on the front and back of the metal plate S and spraying a water stream has been put into practical use.

In addition, as a result of examination by the present inventors, it was found that the multi-stage parallel jet formed by placing a plurality of water spray nozzles 3a that spray the cooling medium in parallel varies greatly due to the influence of the surrounding flow. If the classification changes, the collision position with the metal plate S also changes, so removal of the vapor film becomes unstable. Therefore, it was found that in the simple addition of the constraint roll 4a, the vapor film removal state becomes unstable and the shape of the metal plate S may deteriorate. On the other hand, scratches that occur on the surface of the metal plate (S) are defects caused by slipping of the restraint roll (4a), and hydroplay occurs when a water film is formed between the restraint roll (4a) and the metal plate (S). It was thought to be caused by the ning phenomenon.

1: Quenching device
2: Water tank
3: Water spray device
3a: water spray nozzle
3b: Refrigerant sprayed from water spray nozzle
4: Restraint Roll Pair
4a: Restraint Roll
D: roll diameter
P: Mail order direction
Rz: maximum height illuminance
S: metal plate
K: Deflection amount
W: sleep
A: Distance from the water surface to the cooling start point
B: Distance between the central axes of a pair of facing constraint rolls (offset value)
C: Distance between pair of restraint rolls
I: Movement amount of restraint roll in the direction of press-fitting the metal plate (I.M)

Claims (9)

A metal plate cooling device having a water tank for cooling a metal plate through which the plate is passed by immersing it in a liquid, a water spray device formed on the water tank, and a plurality of pairs of restraint rolls for restraining the metal plate through the inside of the water tank,
The water spray device has a plurality of water spray nozzles installed so that cooling water is sprayed oppositely across the front and back surfaces of the metal plate along the plate direction of the metal plate,
A quenching device for a metal plate, wherein the plurality of constraint roll pairs are each independently adjusted in position with respect to the metal plate based on operating conditions. According to claim 1,
A quenching device for a metal plate, wherein the plurality of restraining roll pairs have maximum and minimum surface height roughnesses (Rz) of both 5 μm and 50 μm or less. According to claim 1,
A quenching device for metal plates in which the restraint rolls of the plurality of restraint roll pairs have a roll diameter of 50 mm or more and 250 mm or less. According to claim 1,
The plurality of pairs of restraint rolls are of metal plates arranged so that, when the roll diameter is D mm, the distance between the central axes of a pair of restraint rolls facing each other with the metal plate in between is D × 1/4 mm or more and D mm or less. ??Ching device. A continuous annealing facility in which the metal plate quenching device according to any one of claims 1 to 4 is provided on the exit side of the crack zone. After cooling is initiated by immersing the continuously rolled metal plate in the liquid,
While the temperature of the metal plate is in the range of the martensite transformation start temperature of the metal plate + 150 ° C. or lower and the martensite transformation end temperature - 150 ° C. or higher, a plurality of pairs of restraining rolls whose positions relative to the metal plate are adjusted are used to A method of binding a metal plate to restrain it. A method of producing a cold rolled steel sheet, comprising quenching the cold rolled steel sheet by the quenching method of a metal plate according to claim 6. A method for manufacturing a plated steel sheet, wherein the cold rolled steel sheet is subjected to a plating treatment following the method for manufacturing the cold rolled steel sheet according to claim 7. According to claim 8,
A method of producing a plated steel sheet, wherein the plating treatment is performed by any of electrogalvanizing treatment, hot-dip galvanizing treatment, and alloyed hot-dip galvanizing treatment.

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