[0001]The present invention relates to a secondary cooling method and the secondary cooling device in performing the continuous casting of slabs in a continuous casting machine.
Background technique
[0002]In continuous casting of steel industry, as a method of secondary cooling of the slab, the conventional cooling spray method is widely used. The secondary cooling method is to spray nozzles disposed between the support rolls for conveying the cast piece, cooling the cooling water by spraying to the surface of the spray shape to bloom.
[0003]
　The cooling spray method has a problem of supercooling by a so-called sagging water or stagnant water. Dripping water, in divided rolls is support roll of the slab, a cooling water flowing down to the downstream side from the bearing section that is not in contact with the slab. Moreover, accumulated water is cooling water staying in the space enclosed by the roll peripheral surface and the billet surface. When interferes with cooling water dripping water and reservoir water injected from the spray nozzle, the interference portion is supercooled, in the slab width direction cooling becomes uneven.
[0004]
　Therefore, for example, Patent Document 1, depending on the occurrence position thereof dripping water and reservoir water, by appropriately adjusting the amount of water in arrangement and cooling water spray nozzle, to suppress the supercooling by dripping water and reservoir water Te, secondary cooling method of improving the cooling uniformity is disclosed.
[0005]
　Also, if the spray method, water is scattered by injecting water to the hot slab, because the injected water is not efficiently used, there is a limit to the cooling capacity. Therefore, future, in order to improve productivity by increasing the casting speed, or to significantly increase the amount of water supply, it is necessary to extend the captain of the continuous casting machine to increase the secondary cooling zone. That is, in the state of the continuous casting machine can not deal, in order to speed up the continuous casting, a considerable improvement in heat transfer coefficient is desired in the secondary cooling.
[0006]
　Conventionally, in order to uniformly cool by reducing the temperature unevenness in the secondary cooling, for example, Patent Document 2, the secondary cooling method of cooling is disclosed to hold the billet surface temperature in the region of the film boiling, the rolls discloses that by arranging the porous plate for ejecting a cooling water.
[0007]
　As a method of improving the cooling capacity of the secondary cooling, for example, in Patent Document 3, cooling grid equipment is disclosed which uses a wear plate.
[0008]
　Further, for example, Patent Document 4, by using a water film flow slab is cooled, the secondary cooling process of continuous slab increase the cooling capacity is disclosed.
[0009]
　Further, for example, Patent Document 5, the formed by slab continuous bed a water film flow between the guide plate and cast strip is cooled, a secondary cooling method of the continuous slab increase the cooling capacity is disclosed.
CITATION
Patent Document
[0010]
Patent Document 1: Japanese Patent No. 5598614
Patent Document 2: Japanese Patent No. 5146006
Patent Document 3: Japanese Patent No. 4453562 discloses
Patent Document 4: JP 2002-086253 Patent Publication
Patent Document 5: JP-A 9-201661 JP
Summary of the Invention
Problems that the Invention is to Solve
[0011]
　However, the present inventors have made extensive study, also said secondary cooling method, it was found that there are the following problems.
[0012]
　Case of Patent Document 1, although it is possible to some extent the effects of sagging water and reservoir water, or using a large amount of cooling water spray method, it is impossible to prevent the effects of these dripping water and reservoir water completely. Therefore, there is still room for improvement in the cooling uniformity. Further, since the cooling of the spray method, there is a limit to the cooling capacity, as described above.
[0013]
　Also, in the case of Patent Document 2, for injecting cooling water from a plurality of ejection holes arranged in the longitudinal direction of the slab tends to occur stagnation of interference and cooling water accompanying the cooling water with each other, can not be uniform cooling .
[0014]
　Also, in the case of Patent Document 2, since in this way the longitudinal direction into a plurality of ejection holes of the slab is formed, the movement distance of the cooling water injected from one injection holes is short. Furthermore, since the slab is cooled while being transported, after being cooled by the cooling water from one jet holes are also cooled by the cooling water from the other ejection hole. Then, in the longitudinal direction of some portion of the slab, it means that the local cooling are repeated, it may be cooled by the cooling water from all the ejection hole is not constant. In such a case, within the cooling surface of the slab will be stable cooling area and unstable cooling region are mixed, as a result, the cooling in the cooling surface of the slab becomes unstable.
[0015]
　Furthermore, the method disclosed in Patent Document 2, to cool the slab using only refrigerant film boiling region so as not to supercool. However, film boiling region has a lower heat transfer coefficient in comparison with the transition boiling region, unlikely the significant improvement of the cooling capacity. Further, after cooling in the film boiling region, no evaporation of the cooling water.
[0016]
　In the case of Patent Document 3, it is imparted a cooling function in wear plate that is provided in the cooling grid facilities. However, wear plate since in contact with the slab, scratches generated on the surface of the slab, since the quality problem arises, practical application is difficult.
[0017]
　In addition, in the case of Patent Document 4, continuously moved in the opposite direction of the pull-out direction of the slab, for example the gap between the water film forming plate and slab which is driven with an endless track (Crawler), etc., each water and water from the water supply port provided in the film forming plate, although secondary cooling method of continuous casting for forming a water film flow thickness 0.1 ~ 2.5 mm is disclosed, a plurality of longitudinally aligned for water cooling water from the water supply port, likely to occur stagnation of interference and cooling water accompanying the cooling water with each other, it can not be uniformly cooled. Further, if a thickness of 0.1 ~ 2.5 mm water film flow, which cools the nucleate boiling region billet primarily from the non-boiling region as described below, not cooled in the transition boiling region. Further, the gap of the thickness of 0.1 ~ 2.5 mm is small, low degree of freedom for installing the water film forming plate.
[0018]
　Also, in the case of Patent Document 5, between the guide plate and cast piece, and the water supply from the water supply port provided on the guide plate, water film flow as in the case thickness 0.1 ~ 2.5 mm in Patent Document 4 to form a continuous floor. Even such a case, is intended to primarily cool the nucleate boiling region billet from the non-boiling region, not cooled in the transition boiling region. Since the gap of the guide plate and the slab is small, less freedom to install a guide plate.
[0019]
　Accordingly, the present invention improves the cooling capacity of the secondary cooling in continuous casting machines, or increase the amount of water significantly, without or extend the captain of the continuous casting machine, can respond to faster casting rate, it is an object to provide a continuous casting secondary cooling method and the secondary cooling device.
Means for Solving the Problems
[0020]
　To solve the above problems, the present invention, while ensuring the uniformity of the cooling, it was investigated to improve the cooling efficiency of the slab. Consequently, by cooling the stable refrigerant slab of transition boiling state, without increasing the amount of refrigerant, it can improve the cooling efficiency, and further, it has been found that can be secured also uniformity of cooling. That is, the present invention relates to [10] of the following [1].
[1] A secondary cooling process of the cast strip being cast by a continuous casting machine,
　said continuous casting machine, a secondary cooling zone beneath the mold, supporting the slab from both sides in the thickness direction of the slab to have a plurality of pairs supporting rolls,
　the cooling device between the support rolls adjacent to each other along the casting direction of the continuous casting machine is disposed,
　the cooling device includes
　a refrigerant pipe and supplying a refrigerant
　to the refrigerant on the slab comprising a plate-shaped refrigerant guide plate for spreading,
　the refrigerant guide plate, in a situation that is parallel to spaced in a direction perpendicular to the surface of the slab,
　the refrigerant, provided in said refrigerant guide plate from the supply port of the coolant, is supplied into the gap of the slab surface and the coolant guide plate, and having a step of cooling the main refrigerant slab of transition boiling region, the secondary cooling process of continuous casting slab .
[2] the slab surface and spacing of the refrigerant guide plate is at 5mm or more, and the refrigerant, the time to reach the supply port of the refrigerant on the upstream side end or the downstream end of the casting direction of the refrigerant guide plates characterized by a 0.6 seconds or less, the secondary cooling process of continuous casting slab according to [1].
[3] feed port of said refrigerant, characterized in that it is a slit in the width direction of a plurality of holes or slab that are arranged in a row in the width direction of the slab with the longitudinal direction, the [1] or [2 secondary cooling method of the continuous casting slab according to any one of.
[4] The refrigerant is supplied from the supply port of the refrigerant in the liquid phase, in the flow path of the slab surface and the refrigerant guide plates, until it reaches the upstream end or the downstream end of the casting direction of the refrigerant guide plates all characterized by comprising a gas phase, the secondary cooling method of [1] to [3] the continuous casting slab according to any one of the.
[5] In the slab surface and the coolant guide plate gap, from at least one of the casting direction upstream side end or the downstream end, characterized by discharging the vapor of the refrigerant, the [1] - [4 secondary cooling method of the continuous casting slab according to any one of.
[6] The refrigerant cooling heat removal amount for all the gas phase before reaching the upstream end or the downstream end of the casting direction of the refrigerant guide plate, that satisfies the following formula (A) wherein the secondary cooling method of [1] to [5] continuous casting slab according to any one of.
Q / W ≧ 59 × 10 6 [J / m 3 ] · · ·
(A) Q: cooling heat removal amount
W: water density
in [7] the secondary cooling zone beneath the continuous casting machine mold, the thickness of the slab among a plurality of pairs of support rolls for supporting the slab from both sides of the direction, it is disposed between the supporting roll adjacent along the casting direction, a secondary cooling device of the continuous casting slab,
　and supplies the refrigerant refrigerant tube and
　Comprising a plate-shaped refrigerant guide plate for spreading the refrigerant on the slab,
　the refrigerant guide plate is arranged in parallel at an interval in a direction perpendicular to the surface of the slab,
　the slab surface and the refrigerant guide plate interval is at 5mm or more, and the refrigerant, from the supply port of the refrigerant provided in the refrigerant guide plate, the time to reach the upstream end or the downstream end of the casting direction of the refrigerant guide plate 0.6 s is set to less,
　the coolant is supplied from the supply port of the coolant in the gap of the slab surface and the coolant guide plate, and wherein the cooling the cast piece by the refrigerant of the main transition boiling region, continuous casting slab of the secondary cooling device.
[8] the and further comprising a gap control mechanism that controls the spacing of the slab surface and the coolant guide plate, continuous casting slab of the secondary cooling device according to [7].
[9] the supply port of the refrigerant, characterized in that it is a slit in the width direction of a plurality of holes or slab that are arranged in a row in the width direction of the slab with the longitudinal direction, said [7] or [8 continuous casting slab of the secondary cooling device according to any one of.
[10] from one of the slab surface and at least the casting direction upstream side end portion of the gap between the refrigerant guide plate or downstream end, and further comprising an exhaust portion for discharging a refrigerant which has become gas phase, the [7] to the continuous casting slab of the secondary cooling device according to any one of [9].
Effect of the invention
[0021]
　According to the present invention, in the secondary cooling of the slab being cast in a continuous casting machine, a secondary cooling device of the secondary cooling method and a continuous casting slab of the slab being cast in a continuous casting machine of the present invention the by applying, it is possible to cool the cast strip in a stable transition boiling region having a high cooling capacity, the cooling efficiency of the secondary cooling can be greatly improved. Accordingly, without increasing the amount of refrigerant, it is possible also supports faster casting speed, it is possible to suppress the central segregation due to the generation of dripping water or pool water. Further, it is possible to improve cooling uniformity in the width direction of the slab, it is possible to suppress the surface cracks of the cast piece due to the temperature variation.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022]
FIG. 1 is a side view showing an outline of a continuous casting machine according to an embodiment of the present invention.
FIG. 2 is a side view showing a part of a continuous casting machine provided with such a cooling apparatus according to the embodiment of the present invention.
[Figure 3] Figure 2 is a view seen directly opposite the slab surface.
[4] shows the relationship between the slab surface temperature and heat transfer coefficient in the secondary cooling. The heat transfer coefficient of the water film cooling of the present invention with a solid line, a dotted line a heat transfer coefficient of the water film cooling disclosed in Patent Document 2 shows a heat transfer coefficient of the spray cooling by broken lines. Also shows in Fig together range of heat transfer coefficients to be utilized in the present invention and water film cooling in Patent Document 2.
Is a sectional view showing an outline of FIG. 5 spray experimental apparatus for testing the cooling capacity of the cooling.
Is a sectional view showing an outline of FIG. 6 experimental apparatus for testing the cooling capacity of the water film cooling.
[7] water density 1000L / min. m 2 heat transfer coefficient of the water film cooling in the case of shows to the flow path gap spacing. A heat transfer coefficient as measured by the experimental apparatus of FIG. 6 is a graph comparing the heat transfer coefficient of the measured spray cooled by the experimental apparatus of FIG.
In [8] water film cooling is a diagram for explaining a change in the state of the water in contact with the slab.
[9] water density 500L / min. m 2 heat transfer coefficient of the water film cooling in the case of shows to the flow path gap spacing. A heat transfer coefficient of the water film cooling measured by the experimental device of FIG. 6 is a graph comparing the heat transfer coefficient of the measured spray cooled by the experimental apparatus of FIG.
DESCRIPTION OF THE INVENTION
[0023]
　The following describes embodiments of the present invention.
[0024]
　First, referring to FIG. 1, illustrating the overall configuration of the continuous casting machine. Figure 1 is an explanatory diagram showing a schematic configuration of a continuous casting machine 1 according to this embodiment.
[0025]
　Note that the method of the continuous casting machine, there are a variety of methods. For example, (a) the mold and the support roll disposed vertically with vertical, the slab solidified while moving (b) vertically, a vertical bending type bending horizontally solidification completion position, and (c) bending molds supporting roll It was arranged on the same radius on the arc, horizontally bent back curved in end solidifying cast slab, (d) a template and upper support rolls arranged vertically, Thereafter a slab containing unsolidified steel gradually bending, vertical gradually bending die back horizontally coagulation end, (e) mold, the horizontally disposed the horizontal supporting rolls, and the like. Figure 1 is an example of a vertical gradually bending type continuous casting machine, the present invention is applicable to systems of any of a continuous casting machine is not limited thereto.
[0026]
　Continuous casting machine 1, as shown in FIG. 1, the tundish 2 for temporarily storing the molten steel, the immersion nozzle 4 for injecting the molten steel into the mold 3 from the bottom of the tundish 2, the cast slab H drawn out from the mold 3 and a pair of rolls 6 and 7 disposed opposite each other across the slab passage 5 pass, and the slab passage 5.
[0027]
　A pair of rolls 6 and 7, the cast slab H casting direction D along the slab path 5 1 so as to guide the respectively provided on both surfaces of the slab passage 5, from both sides in the thickness direction of the slab H supporting the slab H. Rolls 6 on the inner circumferential side has a plurality of support rolls 10 for guiding the inner circumference side of the slab H of the slab passage 5. Each supporting roll 10, the center axis thereof so as to face in the width direction of the slab H, casting direction D 1 are arranged side by side in a row along the. Further, rolls 7 on the outer peripheral side has a plurality of support rolls 11 for guiding the outer peripheral side of the slab H of the slab passage 5. Each supporting roll 11, the center axis thereof so as to face in the width direction of the slab H, casting direction D 1 are arranged side by side in a row along the.
[0028]
　Molten steel in the tundish 2 is injected through the immersion nozzle 4 from the upper side of the mold 3, in a mold 3 is primary cooling to form a solidified shell on the contact surface with the mold 3. Furthermore, the cast piece H is below the template 3, continuously while being cooled by the secondary cooling water in a state of being sandwiched between the supporting rolls 10, 11 having unsolidified molten steel the solidified shell and the outer shell, inside withdrawn into, the slab H coagulation is completed until eventually center is produced.
[0029]
　The secondary cooling device of the continuous casting slab of the present invention (cooling device 31, see FIGS. 2 and 3) does not have the the illustration in FIG. 1, it is provided in the secondary cooling zone below the mold 3 , casting direction D 1 is arranged between the mutually supporting roll 10 adjacent along, cooling the cast strip H. The cooling device 31 is not only the vertical portion of the continuous casting machine 1 may be provided in the curved portion or the horizontal portion. Applicable temperature of the cooling device 31 is about 1100 ° C. to about 600 ° C. from (mold immediately below) (horizontal section). In the continuous casting machine, a secondary cooling method and the secondary cooling device of the continuous casting slab of the present invention, namely a position for applying a water film cooling of the present invention, immediately after the start of casting (mold immediately below) is preferable.
[0030]
　First, the secondary cooling process of continuous casting slab of the present invention (hereinafter sometimes referred to simply as secondary cooling method of the present invention) describes, secondary cooling apparatus of a continuous casting slab of the present invention (hereinafter, simply sometimes referred to secondary cooling device of the present invention) will be described appropriately added as needed for.
[0031]
　Secondary cooling method of the continuous casting slab of the present invention is characterized by having a step of cooling the main refrigerant slab of transition boiling region. More particularly, the present invention provides a secondary cooling method of the slab being cast in a continuous casting machine, a cooling device in the gap of the support rolls are for conveying the cast piece, the cooling device, the a refrigerant guide plate disposed parallel to the said slab with a gap for forming a flow path of the refrigerant between the surface of the slab, includes a refrigerant pipe for supplying said coolant to said gap, said gap It supplied the refrigerant, characterized in that cooling the slab in contact with the cast piece mainly in the transition boiling region, provides a secondary cooling method of the slab being cast in a continuous casting machine .
[0032]
　Transition boiling region is a region between the nucleate boiling region and film boiling region, in the transition boiling region refrigerant in the refrigerant and the gas liquid are mixed. That is, the transition boiling region cast strip (also referred to as billet) is cooled, the solid slab (solid phase), the liquid refrigerant (liquid phase), three-phase interface of the refrigerant gas (vapor) is formed in state refers to the refrigerant to cool the strip cast in contact with the slab surface. Further, in the present invention, the refrigerant is primarily water.
[0033]
　At the time of cooling the steel strip at the transition boiling region, the steel strip can Tsuyohiya, that is, to improve the heat transfer coefficient, for example, "Maximum heat flux propagation velocity during quenching by water jet impingement" International Journal of Heat and It is described in the Mass Transfer 50 (2007) 1559-1568.
[0034]
　Here, the secondary cooling process of continuous casting slab of the present invention will be described with reference to FIG. A secondary cooling method of the present invention, primarily cooled using a water film flow in the transition boiling region, utilizing a stable transition boiling region water film cooling (water film cooling of the present invention, the three-phase interfacial water layer cooling and is also referred to). The horizontal axis of FIG. 4 is the surface temperature of the slab, and the vertical axis represents the heat transfer coefficient. Figure 4 is a water film cooling in the transition boiling region in the present invention, a water film cooling in the film boiling region disclosed in Patent Document 2 described above is shown as a comparative example. Incidentally, in FIG. 4 is shown also to cool the conventional spray method as Reference Examples.
[0035]
　In the disclosed water film cooling in Patent Document 2 is a comparative example, are cooled in a low film boiling region heat transfer coefficient does not cool the transition boiling region. Since slab by the cooling water from a plurality of injection holes (injection holes staggered) formed side by side in the longitudinal direction of the slab is cooled, stable cooling area in the cooling surface of the slab as described above unstable cooling region are mixed with the cooling of the billet becomes unstable. Further, disclosure of water film cooling in Patent Document 2, since the ejection hole is staggered, in the transition boiling zone temperature unevenness occurs due to excessive cooling, cracking occurs accordingly. Therefore, to the transition boiling state it does not occur, and devised the collision pressure is cooled cast strip only in the film boiling region.
[0036]
　In contrast, the water film cooling of the present invention to cool the main refrigerant slab of transition boiling region. By "predominantly transition boiling region", more than 80% of the flow path is in transition boiling state, it means that the remainder being mainly non-boiling region, and / or nucleate boiling region. Is basically without cooling the refrigerant in the film boiling region, may be present in the range of 10% or less in the flow path. Here, the "flow path", the gap between the slab and the refrigerant guide plate, from the supply port of the refrigerant to the upstream side end or the downstream end in the casting direction of the refrigerant guide plates, generally the refrigerant flows in the casting direction it is a region. Incidentally, the refrigerant guide plate, to the slab, are provided in parallel. Here the "parallel" means that it is generally parallel, to the extent practicable the present invention may be offset from a perfect parallel plane with respect to the slab surface.
[0037]
　Transition boiling region in the present invention are the high heat transfer coefficient region, it is possible to improve the cooling efficiency. The water film cooling of the present invention, the refrigerant supplied to the gap of the slab and the refrigerant guide plate is in contact with the cast slab in the transition boiling region, evaporates before the film boiling region. Thus the refrigerant evaporates to cool the slab primarily in the state of transition boiling region only, since there is never a film boiling, cooling does not become unstable. Therefore, in the present invention, it is possible to cool the slab in a stable transition boiling region of the high cooling capacity. As the high heat transfer coefficient in the transition boiling region, 800 W / m, as described below 2 · K or more.
[0038]
　Further, in the present invention since the cooling of such stable transition boiling region cast strip, it is possible to improve cooling uniformity in the width direction of the slab, it is possible to suppress the temperature unevenness of the slab surface. As a result, it is possible to suppress the surface cracks of the cast piece due to the temperature variation.
[0039]
　Further, since the present invention performs a water film cooling in the transition boiling region, the cooling efficiency is increased, it can be suppressed to a small amount of refrigerant quantity. Further, since the amount of refrigerant is the amount that evaporates in the transition boiling region, the occurrence of dripping water and reservoir water in a conventional spray system which has become an issue in Patent Document 1, also is possible to suppress the central segregation associated therewith it can.
[0040]
　The gap (distance of the surface of the refrigerant guide plate and billet) is at 5mm or more, and the passing time of the refrigerant in the flow path is preferably a gap equal to or less than 0.6 seconds. Incidentally, the refrigerant supplied from the supply port is usually half the flow to the upstream side, the other half flows to the downstream side. Therefore, the distance to pass through the piece refrigerant cast is from the supply port to the upstream end of the casting direction or downstream side end portion of the refrigerant guide plate, the length of the conveying direction of the slab. In other words, the transit time of the refrigerant in the flow passage, is the time from the supply port to the upstream end of the casting direction or downstream side end portion of the refrigerant guide plate, the length of the conveying direction of the slab the refrigerant passes .
[0041]
　It transit time of the refrigerant in the flow passage is less than 0.6 seconds, the ratio (Q / W) of the cooling heat removal amount for water density of the refrigerant (W) (Q), i.e., cast to all refrigerant evaporation can in other words the amount of heat given from the piece. As described later, when the refrigerant is water, the refrigerant evaporates in the transition boiling region, the ratio of the cooling heat removal amount in the water film cooling to the water density of the refrigerant (W) (Q) (Q / W) is × 10 59 6 J / m 3 is the need to more.
[0042]
　Interval of the gap is preferably 9mm or less. Distance is greater than 9 mm, not evaporate completely the refrigerant, since the remains of the liquid phase, will be to cool the slabs in the refrigerant film boiling region, not expected to improve the cooling efficiency. Further, the interval of the gap is less than 5 mm, since the slab surface and the coolant guide plate approaches, scale and generated in the billet surface by cooling, by bending and bulging of the billet caused by the cooling, the cooling guide There is a risk that the plate and the cast piece is in contact, not practical.
　Transit time of the refrigerant in the flow path, preferably at least 0.3 seconds. When transit time is less than 0.3 seconds, before the coolant is a transition boiling region, will pass through the flow path, that is, cooling the slabs with the refrigerant of the non-boiling region or nucleate boiling region becomes therefore, not be expected to improve the cooling efficiency.
[0043]
　The refrigerant is supplied to the gap through a supply port formed in the refrigerant guide plate. The supply port is preferably the width direction of a plurality of holes or the cast piece that are arranged in a row in the width direction of the slab is slit whose longitudinal direction.
[0044]
　On the other hand, the water film cooling disclosed in Patent Document 2 described above, unlike the present invention, a plurality of injection holes in the longitudinal direction of the slab are formed (i.e., ejection holes are arranged in a staggered pattern) since, stable cooling area and unstable cooling region are mixed in the cooling surface of the slab as described above, the cooling of the billet becomes unstable. Therefore, in the method disclosed in Patent Document 2, cracks due to temperature unevenness By using a coolant transition boiling region. To avoid such cracks, water film cooling disclosed in Patent Document 2 has a cooling method utilizing the film boiling region.
[0045]
　In contrast, in the present invention, the supply port because it is one place in the longitudinal direction of the slab, across in the cooling surface of the slab, it is possible to realize cooling in a stable transition boiling region. Further, the supply port in the present invention, since a slit to the width direction of the plurality of holes or slab that are arranged in a row in the width direction of the slab with the longitudinal direction, the coolant from the supply port in the width direction of the slab It is uniformly supplied. Therefore, it is possible to further improve the cooling uniformity in the width direction of the slab.
[0046]
　In the present invention, the refrigerant supplied to the gap between the refrigerant guide plate and the slab, in contact with the cast slab in the transition boiling region cooled, it is preferable that all evaporate prior to entering the film boiling region. Further, one from at least the upstream end of the casting direction or downstream side end portion in the gap, it is preferable to discharge the vapor of the refrigerant.
[0047]
　In the present invention, the refrigerant supplied to the gap evaporates mainly in contact with the cast strip in the transition boiling region, the slab will not be cooled by the low film boiling region heat transfer coefficient. Then, by actively discharged vapor of the refrigerant, it is possible refrigerant more reliably prevented from contacting the piece cast in a film boiling region. Therefore, it is possible to cool the slab at more stable transition boiling region.
[0048]
　Next, FIG. 2, and with reference to FIG. 3, a configuration of the secondary cooling device according to an embodiment of the present invention.
[0049]
　Cooling device 31 is one embodiment of the present invention includes a refrigerant guide plate 32 to the width direction of the slab H as the longitudinal direction, comprising a water supply pipe 33 as a refrigerant pipe for supplying refrigerant, supported by a supporting mechanism (not shown) It is. Refrigerant guide plate 32 is flat, it is possible to expand the refrigerant on the slab.
[0050]
　The cooling device 31, the exhaust pipe 34 upstream of the casting direction is an exhaust portion for both (mold side) end and the downstream end of the water supply port 36, provided so as to penetrate through the refrigerant guide plate 32 it is preferable to have. The exhaust pipe 34, for example, as shown in FIG. 3, may be a round hole about a plurality of φ5mm aligned in a row in the width direction of the slab H. The vapor of the cooling water is discharged from the exhaust pipe 34.
[0051]
　The exhaust pipe 34 is provided at both ends of the upstream and downstream in the casting direction of the gap 35 may be provided either at one end. Furthermore although the exhaust pipe 34 may be omitted, in order to ensure a high cooling ability by performing a (three-phase interfacial water film cooling of the present invention) water film cooling of the present invention, the steam exhaust pipe 34 is provided it is preferable to actively discharged.
[0052]
　In such a cooling device 31, cooling water supplied to the gap 35 through the water supply port 36 from the water supply pipe 33 flows its half to the upstream side, the other half flows to the downstream side. The coolant cools the surface of the slab H transition boiling region becomes water film flow at 35 within the gap. That is, Tsuyohiya the slab H by utilizing the three-phase interface. Cooling water flowing through the gap 35 is, via a transition boiling region becomes steam until film boiling region, and is discharged from the exhaust pipe 34 of the upstream end and the downstream end portion in the casting direction of the gap 35.
[0053]
　Refrigerant guide plate 32 is parallel to spaced (gap 35) in a direction perpendicular to the surface of the slab H, it is attached to the cooling device 31 so as to adjust the width of the gap 35. Refrigerant guide plate 32 is intended to extend the refrigerant on the slab, the shape is a flat plate. Here, the gap 35 of the refrigerant guide plate 32 and slab H surface is a channel for a coolant. Incidentally, the "parallel" to the surface of the slab H, means that it is generally parallel.
　At the center of the refrigerant guide plate 32, the supply port of the coolant has been formed (FIG. 2, the water supply port 36 in FIG. 3), the refrigerant from the supply port, the surface and the coolant guide plate 32 of the slab H gap ( is supplied to the gap 35). Water supply port 36, for example, as shown in FIG. 3, it is preferable that the one slit or a plurality of slits of a plurality of φ5mm about the round holes or the width direction of the slab H as the longitudinal direction. However, a plurality of round holes or slits, it is necessary to have in a row in the width direction of the slab H.
　Furthermore, the upstream end of the casting direction of the refrigerant guide plate 32, and at one downstream end, (the exhaust pipe 34, for example in FIG. 3) exhaust portion for discharging a refrigerant which has become gas phase is provided it is preferred that.
[0054]
　The distance between the surface and the refrigerant guide plate 32 of the slab H (gap 35) is at 5mm or more, and the refrigerant supply port from (water inlet 36) in the casting direction of the refrigerant guide plate 32 upstream end or downstream the time to reach the side edge portions is preferably not more than 0.6 seconds.
[0055]
　Therefore, the interval of the gap 35 is preferably controlled by gap control mechanism (not shown). Spacing control mechanism, for example, width of the gap 35, i.e. to measure the distance between the surface and the refrigerant guide plate 32 of the slab H, comprising a distance meter (not shown). Here, bulging of the slab H varies in the casting direction, there may be a case where the thickness of the gap 35 deviates from a predetermined range (5mm or 9mm or less). Therefore, the distance interval of the gap 35 by the meter, i.e. keep constantly measures the height of the flow path of the refrigerant, when the interval of the gap 35 is out of the predetermined range, by adjusting the installation position of the refrigerant guide plate 32 controlling the thickness of the gap 35 Te. In such a case, it is possible to always maintain the thickness of the gap 35 in a predetermined range, it is possible to perform cooling of a stable transition boiling region of the high cooling capacity. In the case where the interval of the gap 35 is out of the predetermined range may be issued a warning.
[0056]
　In this embodiment, it is possible to cool the slab H with high stable transition boiling region heat transfer coefficient. Furthermore, the water supply port 36 because it is one place in the longitudinal direction of the slab H, across in the cooling surface of the slab H, it is possible to realize cooling in a stable transition boiling region.
[0057]
　Further, water inlet 36, a plurality of slits aligned slab H plurality of round holes arranged in the width direction in one row of width direction of the slab H into one slit or width direction and longitudinal direction in a row since it is, the cooling water is uniformly supplied in the width direction from the water supply port 36. Therefore, it is possible to improve cooling uniformity in the width direction of the slab H.
[0058]
　In addition, by actively discharged vapor of the cooling water in the gap 35, can be cooling water is more reliably prevented from contacting the cast piece H in film boiling region. In other words, without being cooled in the region of low heat transfer coefficient, it is possible to cool the slab H in a stable transition boiling region.
[0059]
　Note that in the water film cooling of the present invention, water density is preferably supply capacity maximum value approximately of the cooling water pump in an existing continuous casting machine. Increase of water density, may be new in the cooling water pump is required, becomes excessive capital investment, there may not be realistic.

claims

A secondary cooling process of the cast strip being cast by a continuous casting machine,
　said continuous casting machine, a secondary cooling zone beneath the mold, plurality of pairs of supporting the slab from both sides in the thickness direction of the slab of a support roll,
　a cooling device between the support rolls adjacent to each other along the casting direction of the continuous casting machine is disposed,
　the cooling device includes
　a refrigerant pipe and supplies the refrigerant
　to expand the refrigerant on the slab comprising a plate-shaped refrigerant guide plate,
　the refrigerant guide plate, in a situation that is parallel to spaced in a direction perpendicular to the surface of the slab,
　the supply of refrigerant to the refrigerant, provided in said refrigerant guide plate mouth, and supplies the gap between the slab surface and the coolant guide plate, and having a step of cooling the main refrigerant slab of transition boiling region, the secondary cooling process of continuous casting slabs.
[Requested item 2]
　The distance between the slab surface and the coolant guide plate is at 5mm or more, and the refrigerant, the time to reach the supply port of the refrigerant on the upstream side end or the downstream end of the casting direction of the refrigerant guide plate 0.6 characterized by a second or less, the secondary cooling process of continuous casting slab according to claim 1.
[Requested item 3]
　Supply port of said refrigerant, characterized in that a slit for a plurality of holes or the width direction of the slab that are arranged in a row in the width direction of the slab with the longitudinal direction, any one of claims 1 or 2 secondary cooling method of the continuous casting slab according to.
[Requested item 4]
　The refrigerant is supplied from the supply port of the refrigerant in the liquid phase, in the flow path of the slab surface and the refrigerant guide plates, all air to reach the upstream end or the downstream end of the casting direction of the refrigerant guide plates characterized in that the phase, secondary cooling method of the continuous casting slab according to any one of claims 1 to 3.
[Requested item 5]
　In the slab surface and the coolant guide plate gap, from at least one of the casting direction upstream side end or the downstream end, characterized by discharging the vapor of the refrigerant, any one of claims 1 to 4, secondary cooling method of the continuous casting slab according to.
[Requested item 6]
　The refrigerant is cooled heat removal amount for all the gas phase before reaching the upstream end or the downstream end of the casting direction of the refrigerant guide plate, and satisfies the following formula (A) , secondary cooling method of the continuous casting slab according to any one of claims 1 to 5.
Q / W ≧ 59 × 10 6 [J / m 3 ] · · ·
(A) Q: cooling heat removal amount
W: water density
[Requested item 7]
　In the secondary cooling zone beneath the continuous casting machine mold, they are arranged on both sides in the thickness direction of the slab out of the plurality of pairs of support rolls for supporting the slab, between the support rolls adjacent to each other along the casting direction , a secondary cooling device of the continuous casting slab,
　the refrigerant pipe and supplies the refrigerant
　comprises a flat refrigerant guide plate for spreading the refrigerant on the slab,
　the refrigerant guide plate, to the surface of the slab in parallel spaced vertically,
　the slab surface and spacing of the refrigerant guide plate is at 5mm or more, and the refrigerant, from the supply port of the refrigerant provided in the refrigerant guide plate, the refrigerant guide plates set the upstream end of the casting direction or the time to reach the downstream end so as to more than 0.6 seconds,
　the coolant is supplied from the supply port of the coolant in the gap of the slab surface and the coolant guide plate , cooling the slabs with the refrigerant of the main transition boiling region The symptoms, the continuous casting slab of the secondary cooling device.
[Requested item 8]
　Wherein and further comprising a gap control mechanism that controls the spacing of the slab surface and the coolant guide plate, continuous casting slab of the secondary cooling device according to claim 7.
[Requested item 9]
　Supply port of said refrigerant, characterized in that it is a slit in the width direction of a plurality of holes or slab that are arranged in a row in the width direction of the slab with the longitudinal direction, any one of claims 7 or 8 continuous casting slab of a secondary cooling device according to.
[Requested item 10]
　From one of the slab surface and the refrigerant guide plates at least the casting direction upstream side end or the downstream end of the gap, characterized by further comprising an exhaust portion for discharging a refrigerant which has become gas phase, claim 7 continuous casting slab of the secondary cooling device according to any one of 1-9.