JP2019099916A - Quenching device and quenching method, and metal plate product manufacturing method - Google Patents

Abstract

To provide a quenching device and quenching method that can suppress shape defects generated in the quenching without generating any defects in a metal plate and reducing the tension strength in a continuous annealing apparatus where the metal plate (e.g., a steel plate) is continuously passed through, and provide a metal plate product manufacturing method.SOLUTION: A quenching device continuously passes through a metal plate and cools it. The quenching device comprises a cooling fluid injector having a plurality of nozzles injecting cooling fluid from both sides of the metal plate to the metal plate, and a movable masking that blocks the collision of the cooling fluid injected from the nozzle to the metal plate. The quenching device makes the tip of the movable masking locate on the position where the metal plate temperature reaches a martensitic transformation initiation temperature, and makes the rear end of the movable masking locate on the position where ferrite is not precipitated on the metal plate.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a quenching and quenching apparatus and a quenching and quenching method for suppressing shape defects generated in a metal plate during quenching and quenching, and a method of manufacturing a metal plate product in a continuous annealing facility for annealing while continuously passing a metal plate. .

  In the production of metal plates including steel plates (metal plate products), the metal plates are heated and then cooled to cause a phase transformation, etc., in a continuous annealing facility that performs annealing while continuously passing the metal plates. Work to make the

  In recent years, in the automobile industry, the demand for thin-walled high-tensile steel sheets (high ten) has been increasing for the purpose of achieving both weight reduction of the vehicle body and collision safety. At the time of manufacture of high-tensile steel sheet, a technology for rapidly cooling the steel sheet is important. Water quenching is known as one of the techniques with the fastest cooling rate of steel plates. In the water quenching method, rapid quenching of the steel plate is performed by immersing the heated steel plate in water and simultaneously injecting cooling water onto the steel plate by a quench nozzle provided in the water.

  FIG. 4 is an explanatory view showing a conventional rapid quenching apparatus 90. As shown in FIG. This quenching and quenching device 90 can be applied to a cooling facility provided on the outlet side of the soaking zone of the continuous annealing furnace. As shown in FIG. 4, the quenching and quenching apparatus 90 sprays cooling water onto the metal plate (for example, steel plate) 1 in the water tank 7 covered with the water 2 a and the water tank 7 to jet water for cooling to the water temperature. The nozzle 2 and the sink roll 4 for changing the transport direction of the metal plate 1 by immersing the metal plate 1 in the water tank 7 are provided.

  At the time of rapid quenching of such a metal plate, there is a problem that shape defects such as warpage and wave deformation occur in the metal plate. Conventionally, various methods have been proposed in order to prevent such shape defects during rapid quenching of the metal sheet.

For example, in Patent Document 1, when the temperature at the Ms point (martensitic transformation start temperature) of the metal plate is T _Ms (° C.) and the temperature at the Mf point (martensitic transformation end temperature) is T _Mf (° C.) a metal plate in the extent the temperature of the metal sheet _(T Ms +150) _(℃) from _{(T Mf -150) (℃)} , a technique for restraining has been proposed by a pair of constraining rolls.

  Further, Patent Document 2 proposes a method in which quenching of the metal plate is temporarily stopped and isothermally held by providing a heating device after the cooling device and then providing the cooling device again, and then quenching again.

Patent No. 6094722 JP, 2015-38234, A

  However, although the method described in Patent Document 1 can certainly prevent deformation of the metal plate at the time of quenching and quenching, there is a problem that a scratch defect may occur in the metal plate when the restraining roll contacts the metal plate. There is.

  Further, in the method described in Patent Document 2, since the distance between the two cooling devices is long and the isothermal holding time is long, there is a problem that ferrite is precipitated and the tensile strength is lowered.

  The present invention has been made to solve such a problem, and is generated in a metal plate at the time of quenching and quenching in a continuous annealing facility which performs annealing while continuously passing a metal plate (for example, a steel plate). It is an object of the present invention to provide a quenching and quenching apparatus and a method of quenching and quenching, and a method of manufacturing a metal sheet product, which can suppress shape defects without causing defects in a metal sheet and without reducing tensile strength. .

  The present inventors earnestly studied to solve such a problem, and as a result, they obtained the following findings and ideas.

  That is, since the shape defect at the time of quenching and quenching of the metal sheet is expansion due to martensitic transformation between the Ms point and the Mf point during heat contraction due to the quenching, a large stress acts on the metal sheet and the shape is broken. It is. Therefore, it is possible to reduce the stress acting on the metal plate if the timing of occurrence of thermal contraction and transformation expansion which normally occurs continuously can be shifted, that is, thermal contraction and transformation expansion can be generated discontinuously, As a result, the shape is less likely to collapse. The thermal contraction and the transformation expansion are generated discontinuously by stopping the cooling once at the moment when the temperature reaches the Ms point, as seen from any one point on the passing metal plate. It means to restart cooling after time. At this time, as described in Patent Document 2, if the predetermined time (holding time) is too long, ferrite precipitates and the tensile strength is lowered, so that the ferrite precipitation can be suppressed. In addition, in quenching and quenching of a metal plate, it is not necessary to immerse the metal plate in water, and if a sufficient amount of water is jetted from a nozzle, a cooling capacity equivalent to jetting in water can be obtained.

  The present invention is based on the above findings and ideas, and has the following features.

[1] A quenching and quenching apparatus for cooling while continuously passing a metal plate,
Provided between a cooling fluid injection device having a plurality of nozzles for injecting a cooling fluid from both sides of the metal plate to the metal plate, and a metal plate passing line through which the nozzle and the metal plate pass; A movable mask for interrupting the collision of the cooling fluid jetted from the nozzle with the metal plate;
The front end of the movable masking is positioned such that the temperature of the metal plate reaches the martensitic transformation start temperature, and the rear end of the movable masking is positioned at a position where ferrite does not precipitate on the metal plate. Quenching apparatus characterized in that.

[2] The quenching and quenching apparatus according to [1], wherein τ (s) is expressed by the following equation, where τ (s) is a cooling interruption time due to the movable masking.
0 <τ ≦ 3.0

  [3] The quench and quench apparatus according to the above [1] or [2], wherein the movable masking is provided with an air jet nozzle.

  [4] A quenching and quenching method of cooling by injecting a cooling fluid from a plurality of nozzles onto the surface of a metal plate which is continuously passed through, wherein the cooling fluid injected from the nozzle collides with the metal plate The cooling of the metal plate by the cooling fluid is interrupted at a position where the temperature of the metal plate reaches the martensitic transformation start temperature using movable masking that interrupts the process, and at a position where ferrite does not precipitate on the metal plate A quenching method characterized in that the cooling of the metal plate by the cooling fluid is resumed.

  [5] The distance from the cooling start position of the metal sheet to the cooling interruption position is set based on the sheet passing speed of the metal sheet, the quenching start temperature, the temperature at the Ms point of the metal sheet, and the cooling speed of the metal sheet The quenching and quenching method according to [4], characterized in that:

[6] The passing speed of the metal plate is v (mm / s), the quenching start temperature is T ₁ (° C.), the temperature of the Ms point of the metal plate is T _Ms (° C.), the cooling rate of the metal plate The quenching and quenching method according to [5], wherein the distance d (mm) from the cooling start position to the cooling interruption position is represented by the following equation as CV (° C./s).
d = (T _1- T _Ms ) v / CV

  [7] The distance from the cooling start position of the metal sheet to the cooling interruption position is defined as the sheet passing speed of the metal sheet, the quenching start temperature, the temperature at the Ms point of the metal sheet, the cooling condition, and the thickness of the metal sheet The quenching and hardening method according to the above [4], which is set based on.

[8] The passing speed of the metal plate is v (mm / s), the quenching start temperature is T ₁ (° C.), and the temperature of the Ms point of the metal plate is T _Ms (° C.) The distance d (mm) from the cooling start position of the metal plate to the cooling interruption position is expressed by the following equation using (° C. mm / s) and the plate thickness t (mm) of the metal plate: The quench hardening method as described in said [7].
d = (T ₁ −T _Ms ) vt / α

[9] The quenching and quenching method according to any one of the above [4] to [8], wherein τ (s) is represented by the following equation, where τ (s) is a cooling interruption time by the movable masking. .
0 <τ ≦ 3.0

[10] The distance e (mm) from the cooling interruption position to the cooling resumption position is expressed by the following equation, where v is the passing speed of the metal plate v (mm / s), The quenching method according to any one of [9].
0 <e ≦ 3.0 v

  [11] A method for producing a metal sheet product, characterized in that, when producing a metal sheet product, quenching is performed using the quenching method according to any one of the above [4] to [10].

  [12] The method for producing a metal sheet product according to the above [11], wherein the metal sheet product is any one of a high strength cold rolled steel sheet, a hot-dip galvanized steel sheet and an alloyed hot-dip galvanized steel sheet.

  In the present invention, in a continuous annealing facility that performs annealing while continuously passing a metal plate (for example, a steel plate), shape defects that occur in the metal plate during quenching and quenching can be generated without causing defects in the metal plate. Moreover, it can suppress, without reducing tensile strength.

It is a figure which shows the rapid-quenching apparatus which concerns on Embodiment 1 of this invention. It is a figure which shows the rapid-quenching apparatus which concerns on Embodiment 2 of this invention. It is a figure which shows the example of the movable masking used by embodiment of this invention. It is a figure which shows the conventional rapid-quenching apparatus. It is a graph which shows the comparison result (warping amount) of this invention example and a comparative example. It is a graph which shows the comparison result (tensile strength) of this invention example and a comparative example. It is a figure which shows the definition of the curvature amount in FIG.

  Embodiments of the present invention will be described based on the drawings.

Embodiment 1
FIG. 1 is a view showing a rapid quenching apparatus 11 according to a first embodiment of the present invention. This quenching and quenching device 11 can be applied to a cooling facility provided on the outlet side of the soaking zone of the continuous annealing furnace.

  As shown in FIG. 1, the quenching and quenching apparatus 11 according to this embodiment 1 is a water 2a which is a refrigerant (cooling fluid) from the both sides of a metal plate (for example, steel plate) 1 passing continuously to the metal plate 1 Are provided between the plurality of water jet nozzles 2 (cooling fluid jet devices) that perform rapid cooling by injecting water and the metal plate passing line through which the water jet nozzles 2 and the metal plate 1 pass. The movable masking 3 is provided to interrupt the jetted water 2 a from colliding with the metal plate 1. Moreover, in order to prevent the water 2a jetted from the water jet nozzle 2 from being scattered around the quenching and quenching device 11, a shielding cover 5 is provided. Further, on the exit side of the shielding cover 5, a sink roll 4 for changing the conveyance direction (passing direction) of the metal plate 1 is provided.

  When the water 2a is jetted from the plurality of water jet nozzles 2 onto the surface of the metal plate 1 to carry out quenching and quenching, the movable masking 3 is provided at a height position where the temperature of the metal plate 1 reaches the martensitic transformation start temperature The rear end of the movable masking 3 (the downstream end in the passing direction, here) at a height position where the front end (the upstream end in the passing direction, here the upper end) is located, and ferrite does not precipitate on the metal plate 1 Make the lower end) be positioned.

  In other words, the movable masking 3 is used to interrupt the cooling of the metal plate 1 by the water 2a at a height position where the temperature of the metal plate 1 reaches the martensitic transformation start temperature, so that ferrite does not precipitate on the metal plate 1 At the height position, the cooling of the metal plate 1 by the water 2a is resumed.

  As a result, the metal plate 1 positioned within the range in which the movable masking 3 exists is held at the martensitic transformation start temperature, and the expansion due to the martensitic transformation is suppressed. And expansion due to martensitic transformation occur discontinuously. As a result, the stress acting on the metal plate 1 is reduced, and the generation of the shape defect can be suppressed. Moreover, while being able to avoid generation | occurrence | production of the abrasion defect by contact with a restraint roll like patent document 1 mentioned above, the fall of the tensile strength by precipitation of a ferrite like patent document 2 mentioned above can be prevented. .

At that time, from the cooling start position (the position where water 2a from the water spray nozzle 2 at the top collides with the metal plate 1) to the cooling interruption position (upper end of the movable masking 3, ie, the metal plate 1 starts martensitic transformation) The distance d (mm) to reach the height position) is the sheet passing speed v (mm / s), the thickness t (mm) of the metal plate 1, the quenching start temperature T ₁ (° C), Ms of the metal plate 1 It is preferable to set based on the temperature T _Ms (° C.) of the point and the cooling rate CV (° _C./s ) of the metal plate 1.

Here, since the relationship of the following equation (1) holds between the above values, the distance d (mm) is expressed by the following equation (2).
CV = (T ₁ −T _Ms ) / (d / v) (1)
d = (T _1- T _Ms ) v / CV (2)

The cooling rate CV is a constant α of the metal plate 1 determined according to the cooling conditions (plate thickness t and nozzle shape, type of cooling fluid to be jetted (here, water 2a), temperature, jet amount, etc.) It can be represented using the plate thickness t and can be represented by the following equation (3) because it is approximately inversely proportional to the plate thickness t.
CV = α / t (3)

For example, in the case of a steel plate having a thickness t of 1 to 2 mm, it is represented by the following equation (4), and the intermediate value is represented by the following equation (5) (see paragraph [0022] of Patent Document 1).
CV = 1000 / t to 2000 / t (° C./s) (4)
CV = 1500 / t (° C./s) (5)

That is, in this case, α is the following equation (6) or (7).
α = 1000 to 2000 (° C. mm / s) (6)
α = 1500 (° C. mm / s) (7)

From this, the above equation (2) can be expressed by the following equation (8).
d = (T ₁ −T _Ms ) vt / α (8)

The cooling rates CV (° C./s) and α (° C. mm / s) may be obtained in advance by experiments or numerical analysis, and may be made into a database or a formula. The temperature T _Ms (° C.) at the Ms point can be calculated from the component composition of the metal plate 1.

Further, the cooling interruption time τ (s) due to the movable masking 3 may be determined in advance based on metallurgical considerations, experiments, numerical analysis, and the like. For example, the following equation (9) is used.
0 <τ ≦ 3.0 (9)

  Here, the reason why the upper limit of the cooling interruption time τ (s) is 3.0 s is that when the cooling interruption time τ (s) exceeds 3.0 s, as shown in the examples described later, the metal plate This is because it has been confirmed that ferrite is precipitated in 1 and the tensile strength decreases.

And, the length of the movable masking 3 (in other words, the distance from the cooling interruption position (upper end of the movable masking 3) to the cooling restart position (lower end of the movable masking 3) e (mm) is a relation of the following equation (10) The following equation (11) may be used based on
e = v × τ (10)
0 <e ≦ 3.0 v (11)

  In order to change the length e (mm) of the movable masking 3 in order to change the cooling interruption time τ (s), it is necessary to replace the movable masking 3 with the required length each time as shown in FIG. Movable masking 3A of a structure which can be telescopically expanded and contracted to change the length may be used.

Second Embodiment
FIG. 2 is a view showing a rapid quenching apparatus 12 according to a second embodiment of the present invention.

  As shown in FIG. 2, the quenching and quenching apparatus 12 according to the second embodiment has the same basic configuration as the quenching and quenching apparatus 11 according to the above-described first embodiment, but in addition to that, the movable masking 3 is , And an air jet nozzle 6 for jetting the air 6a.

  Thus, the water 2a on the metal plate 1 is prevented from flowing into the position of the movable masking 3.

  And said Embodiment 1, 2 is applicable to manufacture of a metal plate product (metal plate shipped as a product), and it is especially preferable to apply to manufacture of a high strength steel plate (high ten). More specifically, it is preferable to apply to manufacture of the steel plate which is 580 Mpa or more in tensile strength. The upper limit of the tensile strength is not particularly limited, but may be, for example, 1600 MPa or less.

  Incidentally, as the high strength steel plate (high strength) described above, there are high strength cold rolled steel plates, hot-dip galvanized steel sheets obtained by surface-treating them, alloyed hot-dip galvanized steel sheets and the like.

  As a specific example of the composition of the high strength cold rolled steel sheet, C is 0.04% or more and 0.30% or less, Si is 0.01% or more and 2.50% or less, Mn is 0.80% or more by mass% .00% or less, P is 0.001% or more and 0.090% or less, S is 0.0001% or more and 0.0050% or less, sol. Al is 0.005% or more and 0.065% or less, and at least one or more of Cr, Mo, Nb, V, Ni, Cu, and Ti is 0.5% or less as needed , B and Sb are each 0.01% or less, and the balance is Fe and unavoidable impurities.

  Moreover, it is equally preferable to apply not only to the high strength cold rolled steel sheet but also to the production of a hot-dip galvanized steel sheet or an alloyed hot-dip galvanized steel sheet.

  Thus, in the first and second embodiments, it is possible to suppress the shape defect generated in the metal plate 1 at the time of quenching and quenching without generating any defect in the metal plate 1 and without reducing the tensile strength. Can.

  In the first and second embodiments described above, the case where the steel plate is quenched and quenched with water is described in mind, but the present invention can be applied to cooling of all metal plates other than steel plates, and it is also possible to use other than water. The present invention can also be applied to quenching and quenching using a refrigerant.

  An embodiment of the present invention will be described.

As an example of the present invention, a tensile strength of 1470 MPa at a plate thickness t of 1.0 mm, a plate width of 1000 mm, and a temperature T _{Ms at} a Ms point of 400 ° C. using the rapid quenching apparatus 11 according to Embodiment 1 of the present invention A high-grade cold-rolled steel sheet of a grade was manufactured at a sheet passing speed v of 1500 mm / s and a hardening initiation temperature T ₁ of 800 ° C. The water temperature was 30.degree. C., and the cooling rate .alpha. / T was set to 1500 / t (.degree. C./s) based on the prior measurement and the equation (5). The distance d (mm) from the cooling start position to the cooling interruption position was set at d = 400 mm based on the equation (8). Moreover, cooling interruption time (tau) (s) was 0.25-3.0 s based on said (9) Formula.

  On the other hand, the above-described high-tensile cold rolled steel sheet was manufactured as Comparative Example 1 using the conventional rapid-quenching apparatus 90 shown in FIG. 4 under the same other conditions as the inventive example. However, since the rapid cooling device 90 can not interrupt the cooling once started, the cooling interruption time τ (s) is naturally 0 s.

  In addition, as a comparative example 2, the above-described high-tensile cold rolled steel sheet was manufactured using the quenching and quenching apparatus shown in the above-mentioned Patent Document 2 and making the other conditions the same as the example of the present invention. However, in this quenching and quenching apparatus, since the distance between the two cooling apparatuses is long, the cooling interruption time (holding time) τ (s) between them is 4.0 to 5.0 s.

  Then, in each case (invention example, comparative example 1, comparative example 2), the relationship between the cooling interruption time and the amount of warpage of the steel plate after the cooling end, and the cooling interruption time and the tensile strength of the steel plate after the cooling end We investigated the relationship with The definition of the amount of warpage is shown in FIG. Specifically, the height of the highest position when the steel plate was placed on the horizontal surface was taken as the amount of warpage. Moreover, tensile strength was calculated | required based on JIS Z 2241 metal material tension test method.

  First, FIG. 5 shows the relationship between the cooling interruption time and the amount of warpage of the steel plate after the cooling is completed. In the inventive example and the comparative example 2, the amount of warpage of the steel plate was all reduced to 10 mm or less regardless of the cooling interruption time, but in the comparative example 1, the amount of warpage of the steel plate was 10 mm or more.

  On the other hand, FIG. 6 shows the relationship between the cooling interruption time and the tensile strength of the steel plate after the cooling is completed. In the inventive example and the comparative example 1, the tensile strengths were all 1470 MPa or more regardless of the cooling interruption time, but in the comparative example 2, the tensile strength was significantly reduced to 1470 MPa or less.

  From the above, it was only the example of the present invention that could be manufactured without reducing the tensile strength while reducing the amount of warpage of the steel plate.

  This confirms the effectiveness of the present invention.

1 metal plate 2 water jet nozzle 2a water 3 movable masking 3A movable masking 4 sink roll 5 shield cover 6 air jet nozzle 6a air 7 water tank 11 quenching and quenching device 12 quenching and quenching device 90 quenching and quenching device

Claims (12)

A quenching and quenching apparatus for cooling while continuously passing a metal plate,
Provided between a cooling fluid injection device having a plurality of nozzles for injecting a cooling fluid from both sides of the metal plate to the metal plate, and a metal plate passing line through which the nozzle and the metal plate pass; A movable mask for interrupting the collision of the cooling fluid jetted from the nozzle with the metal plate;
The front end of the movable masking is positioned such that the temperature of the metal plate reaches the martensitic transformation start temperature, and the rear end of the movable masking is positioned at a position where ferrite does not precipitate on the metal plate. Quenching apparatus characterized in that. The quenching and quenching apparatus according to claim 1, wherein τ (s) is expressed by the following equation, where τ (s) is a cooling interruption time due to the movable masking.
0 <τ ≦ 3.0   The said movable masking is provided with an air injection | spray nozzle, The quench hardening apparatus of Claim 1 or 2 characterized by the above-mentioned.   A quenching method for cooling by injecting a cooling fluid from a plurality of nozzles onto a surface of a metal plate which is continuously passed through, and interrupting the collision of the cooling fluid injected from the nozzle with the metal plate The movable masking is used to interrupt the cooling of the metal plate by the cooling fluid at a position where the temperature of the metal plate reaches the martensitic transformation start temperature, and the cooling is performed at a position where ferrite does not precipitate on the metal plate. A quenching method characterized in that the cooling of the metal plate by a fluid is resumed.   The distance from the cooling start position of the metal plate to the cooling interruption position is set based on the passing speed of the metal plate, the quenching start temperature, the temperature at the Ms point of the metal plate, and the cooling rate of the metal plate. The rapid quenching method according to claim 4, characterized in that: The passing speed of the metal plate is v (mm / s), the quenching start temperature is T ₁ (° C.), the temperature at the Ms point of the metal plate is T _Ms (° C.), and the cooling rate of the metal plate is CV (° C.) The quenching and quenching method according to claim 5, wherein the distance d (mm) from the cooling start position to the cooling interruption position is expressed by
d = (T _1- T _Ms ) v / CV   The distance from the cooling start position of the metal sheet to the cooling interruption position is set based on the sheet passing speed of the metal sheet, the quenching start temperature, the temperature at the Ms point of the metal sheet, the cooling condition, and the thickness of the metal sheet. The quenching and quenching method according to claim 4, characterized in that: The passing speed of the metal plate is v (mm / s), the quenching start temperature is T ₁ (° C.), and the temperature of the Ms point of the metal plate is T _Ms (° C.). The distance d (mm) from the cooling start position of the metal plate to the cooling interruption position is expressed by the following equation using mm / s) and the plate thickness t (mm) of the metal plate. The quenching method according to 7.
d = (T ₁ −T _Ms ) vt / α The quenching method according to any one of claims 4 to 8, wherein τ (s) is expressed by the following equation, where τ (s) is a cooling interruption time by the movable masking.
0 <τ ≦ 3.0 The distance e (mm) from the cooling interruption position to the cooling resumption position is set according to the following formula, where v (mm / s) is the sheet passing speed of the metal plate. The quenching method as described in.
0 <e ≦ 3.0 v   The manufacturing method of a metal plate product characterized by performing quenching and quenching using a rapid-quenching method in any one of Claims 4-10 in manufacturing a metal plate product.   The method for manufacturing a metal sheet product according to claim 11, wherein the metal sheet product is any one of a high strength cold rolled steel sheet, a hot-dip galvanized steel sheet, and an alloyed hot-dip galvanized steel sheet.

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