JP2974888B2 - Non-contact sealing device for atmosphere furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to various kinds of atmosphere furnaces for controlling atmospheres such as atmosphere gas composition, composition gas concentration, furnace temperature, etc. in the vicinity of a metal strip to be passed through such as a carburizing furnace. A non-contact type of atmosphere furnace that separates these atmospheres and discharges a sealing gas toward at least the metal strip to individually control each of the partitioned atmospheres, thereby sealing between adjacent atmospheres. The present invention relates to a sealing device.

[0002]

2. Description of the Related Art In the metal secondary processing industry such as the automobile industry, for example, it is required that a metal plate to be processed has both higher workability and higher strength. Specifically, in the automobile industry, since it is necessary to reduce the weight of the vehicle body in order to pursue fuel efficiency due to global environmental issues that have recently become a problem, the conventional deep drawability for press-baked coated steel sheets and the like has been improved. A higher strength thin steel sheet is required after maintenance.

[0003] As evaluation indices of such a metal plate, for example, ductility, deep drawability, aging, strength, secondary work brittleness, bake hardenability, spot weldability and the like can be considered. In view of this, the deep drawability is particularly important, and when this deep drawability is evaluated by a Rankford value (hereinafter, r value: metal sheet width distortion / sheet thickness distortion), carbon in steel (hereinafter, referred to as C) is used. It is known that it is most advantageous to reduce the amount. In addition, the reduction of carbon improves the elongation (Elongation: El) and the aging property at normal temperature (Aging Index: AI is generally lower, the better). However, on the other hand, as the C content in the steel decreases, other evaluation indices generally deteriorate. For example, the tensile strength (Tens
ile strength (TS) is reduced, the grain boundary strength is reduced, and the brittleness in secondary processing is deteriorated, and the amount of solid solution C is reduced, so that the bake hardenability is deteriorated. When the C content in steel is 50 ppm or less, the grain growth rate is accelerated by heating by welding, and the spot weldability is degraded due to coarsening of the heat-affected zone (HAZ).

Therefore, as shown in FIG. 1, a metal strip made of ultra-low carbon steel is recrystallized and annealed by continuous annealing to obtain the above-mentioned ductility, deep drawability, and aging property. The presence of solid solution C in the surface layer by the treatment results in the tensile strength, secondary work brittleness, BH property,
In order to improve the spot weldability, the present applicant has developed a continuous annealing carburizing facility described in JP-A-4-88126 as shown in FIG.

According to the continuous annealing carburizing equipment, the heating zone 2
Alternatively, after performing a predetermined recrystallization annealing on the metal zone in the soaking zone 3, in the carburized zone 4, the temperature of the steel sheet, the specifications of the atmosphere, the transport speed (furnace time), and the first and second cooling zones 5, 6 By performing appropriate carburizing treatment with controlled cooling conditions in step (1), it is possible to continuously produce a metal strip having a desired surface carburization depth and concentration distribution while satisfying the material specifications of the metal strip. For this metal strip, a strip in which steel plates of various material specifications are connected in series by welding or the like is often used.

Meanwhile, in order to reduce the required floor area, a carburizing furnace applied to the carburizing zone is often a vertical continuous gas carburizing furnace in which a strip to be passed is moved up and down a plurality of passes. The strip S passed through the vertical continuous gas carburizing furnace so as to be folded up and down is changed in the direction of passing through the hearth roll 10 as shown in FIG. Specifically, if the strip is wound around substantially half of the outer periphery of the hearth roll, the direction can be changed by 180 °.

The hearth roll uses a chromium-chromium alloy in order to improve the mechanical strength of the hearth roll under high-temperature use conditions. It has been clarified that exposure to atmospheric gas causes carburization and shortens the service life. For this purpose, the hearth roll is partitioned into a separate roll chamber from the heat treatment chamber for performing the carburizing treatment, and an appropriate sealing device is interposed between the heat treatment chamber near the passing plate path and the roll chamber. Therefore, it is necessary to control the atmosphere in both rooms individually. Specifically, in contrast to the carburizing atmosphere in the carburizing heat treatment chamber, the inside of the roll chamber is controlled to a weak carburizing atmosphere or a non-carburizing atmosphere that does not promote carburizing of the hearth roll. Therefore, this sealing device must prevent the carburizing atmosphere gas in the heat treatment chamber from entering the roll chamber for the purpose. On the other hand, if the weakly carburizing atmosphere gas or the non-carburizing atmosphere gas enters the heat treatment chamber, the distribution of the concentration composition occurs in the carburization atmosphere gas in the heat treatment chamber, and the carburization amount and the carburization concentration distribution may be uneven. , Leakage in this direction must also be prevented.

[0008] Among such sealing devices, a typical type of a contact type sealing device is one in which a rotating roll such as a pinch roll directly contacts and rotates a strip.
Such a contact-type sealing device has disadvantages such as flaws on the strip plate surface and thermal deformation. In addition, the sealing property is not sufficient. Therefore, a non-contact type sealing device that discharges a sealing gas to a strip plate surface and seals between both divided atmospheres by a static pressure of the sealing gas generated between the strip surface and the sealing gas has been proposed. And Japanese Patent Application Laid-Open No. 62-270729.

In the non-contact type sealing device described in this publication, on each of the front and back surfaces of the metal strip to be passed, the sealing gas is discharged obliquely inwardly facing each plate surface of the metal strip so as to face each other. A pair of slit-shaped discharge nozzles is provided, a portion other than the discharge nozzles is used as a pressure receiving surface, and the intervals between the discharge nozzles on each plate surface are different from each other. According to this non-contact type sealing device, the seal gas discharged from the discharge nozzle on each plate surface side does not collide with each other, particularly at a position deviating from the plate surface of the metal band, that is, at the side of the metal band width direction. Conventionally, it is possible to suppress the flow of the seal gas leaking from the seal device due to the reversal due to the collision. In addition, by using a gas of the adjacent atmosphere as a seal gas for the discharge nozzles on the side of each atmosphere to be partitioned, it is also performed to suppress a change in atmosphere due to a leak.

[0010]

However, there are cases where sufficient sealing properties cannot be obtained even with the non-contact type sealing device described above, and there is still room for improvement. That is, since the above-mentioned non-contact type sealing device does not have an outlet for the sealing gas injected into the sealing portion, the gas mixed in the sealing portion leaks into any of the partitioned atmospheres. as a result,
The ambient gas in the vicinity of the seal portion cannot be prevented from being diluted by the gas mixed in the seal portion or from increasing the ambient gas concentration.

Further, in the present non-contact type sealing device which simply seals an atmosphere defined only by the flow energy of the sealing gas discharged inward and opposed, in order to prevent leakage between the two atmospheres, The distance between the discharge nozzles facing the plate surface must be set to a certain wide value. (If the distance is too close, the seal gases collide with each other to generate turbulence. In order to generate a static pressure between the seal gas and the plate surface with the seal gas discharged from the discharge nozzles at a wide interval, the discharge amount (supply input amount) of the seal gas is increased. In addition to the waste, the amount of seal gas leaking into the other atmosphere, which increases the flow rate, increases. Further, it is necessary to dispose the discharge nozzle close to the surface of the metal strip in order to improve the sealing property. However, the metal band passed through the metal band sometimes fluctuates due to meandering or the like, and when such fluctuation occurs, the surface of the metal band comes into contact with the discharge nozzle disposed close to the surface of the metal band, and the flaw is generated. There is also a problem that occurs.

The present invention has been developed in view of these problems, and secures high sealing performance while reducing the supply amount of the sealing gas, thereby separating the discharge nozzle from the plate surface of the metal strip. It is an object of the present invention to provide a non-contact type sealing device for an atmosphere furnace which can avoid generation of flaws due to fluctuation.

[0013]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, obtained the following knowledge and developed the present invention. That is, in order to generate a static pressure of the seal gas with a small supply amount between the metal strip plate surface and the discharged seal gas, two discharges relatively close to each other along each plate surface are required. It is well known that the direction of the seal gas from the nozzle may be inwardly opposed to the plate surface. However, if the non-contact type sealing device is constituted only by these two discharge nozzles, there is a possibility that the sealing distance between the divided atmospheres is too short to cause mutual leakage. Therefore, a seal configuration including the two inwardly facing discharge nozzles is provided near two partitioned atmospheres, respectively, and the interval therebetween is appropriately set. If necessary, the vicinity of the plate surface, the side of the metal band, and both seal configurations are provided. By evacuating the seal gas and the gas in the vicinity from between, etc.,
It has been found that the gas flow in the seal portion is optimized, and high sealing performance is exhibited with a small supply amount of the seal gas, whereby each nozzle can be separated from the metal strip surface.

A non-contact type sealing device for an atmosphere furnace according to the present invention is an atmosphere furnace for controlling an atmosphere around a metal band to be passed through. To discharge at least the seal gas in a direction having a component perpendicular to the plate surface of the metal band, or to face the metal band plate surface to discharge the seal gas or a gas in the vicinity thereof. In a non-contact type sealing device of an atmosphere furnace in which a plurality of seal units each having a plurality of nozzles are stacked along a plate surface of a metal strip, the seal unit is disposed along the plate surface in opposition to each plate surface of the metal strip. Of the plurality of nozzles arranged side by side, two nozzles adjacent to each atmosphere are inwardly opposed to the plate surface, and among the seal gas discharged from the two nozzles, the nozzles closer to the atmosphere are arranged. Spitting from nozzle The flow rate of the seal gas, is characterized in that it has a greater than the flow rate of the seal gas discharged from the other nozzles.

[0015]

According to the non-contact type sealing device of the atmospheric furnace of the present invention,
A plurality of seal units are stacked along the plate surface of the metal band, and a plurality of nozzles formed on these seal units and arranged in parallel along the plate surface facing each plate surface of the metal band. Of these, the two nozzles adjacent to each of the divided atmospheres are inwardly opposed to the plate surface, and the gas accompanying the movement of the plate is discharged by discharging the seal gas from these inwardly facing nozzles. Can be stopped (the direction of the flow can be changed). Therefore, by properly setting the interval between the two inwardly facing nozzle structures, the sealing property between the two atmospheres can be improved. In each of the inward facing nozzle configurations, the flow rate of the seal gas discharged from the nozzle closer to the atmosphere is set to be larger than the flow rate of the seal gas discharged from the other nozzle, whereby both nozzles are discharged. The direction of the flow of the sealing gas, that is, the direction in which the static pressure is formed, is directed slightly toward the center of the entire sealing device, thereby suppressing the leakage of the sealing gas to each atmosphere side. The sealing performance is further improved by discharging the sealing gas or the atmosphere gas flowing into the vicinity thereof from the side exhaust port formed in the width direction side of the metal band in the nozzle or the sealing device. Can be.

[0016]

FIG. 2 shows an example of a continuous annealing and carburizing apparatus for strip made of ultra-low carbon steel using the non-contact type sealing device of the atmospheric furnace of the present invention. Each ultra-low carbon steel sheet including steel sheets having different specification specifications desired in FIG.
A series of strips is formed by a not-shown entrance facility having a coil rewinding machine, a welding machine, a washing machine, and the like. The strip S is supplied from the entrance facility to a pre-tropical zone 1, a heating zone 2, a soaking zone 3, and a carburizing zone 4. , The first cooling zone 5, the second cooling zone 6, a shearing machine, a winder and the like, which are not shown in the drawing, and are passed through in this order.

The heating zone 2 is for heating the strip S continuously fed from the inlet facility and preheated in the pre-tropical zone 1 to a temperature higher than the recrystallization temperature. The temperature of the strip S is 700 to 9
Heat the strip to 50 ° C. In the heating zone 2 and the solitary zone 3, near the passing path of the strip that is passed up and down through the hearth roll while being raised and lowered,
A number of radiant tubes (not shown) are provided, and the fuel gas supplied to the radiant tubes is burned to control the furnace temperature (furnace temperature).

The carburizing zone 4 is provided with a carburizing furnace in the carburizing zone 4 by a host computer (not shown) at 700 to 950.
The temperature in the furnace (furnace temperature) is controlled so that the strip temperature (plate temperature) is not less than 700 ° C., preferably not more than the recrystallization temperature, and the strip passes through the carburizing furnace in 10 to 120 seconds. The passing speed is controlled as described above. Incidentally, the furnace temperature control is performed in order to make the amount of carburizing (carburizing reaction speed) constant in the passing direction of the strip and to suppress the variation in the material.

FIG. 3 shows the details of the continuous gas carburizing furnace used for the carburizing zone 4. As shown in the figure, the strip S sent from the leveling zone 3 once rises in the furnace, further descends, rises again, descends again, and is sent out toward the first cooling zone 5. . Therefore, the continuous gas carburizing furnace of the present embodiment has four passes, which are referred to as a first pass to a fourth pass, respectively, in the passing order. Strip S between each pass
Is changed by the hearth rolls 10, so that two hearth rolls 10 are provided above the carburizing furnace and three hearth rolls 10 are provided below the carburizing furnace so that their axes are orthogonal to the passing direction of the strip S. It is arranged in.

These hearth rolls 10 are made of a chromium-chromium alloy in order to improve the strength and abrasion resistance at a high temperature, and to maintain the rotation and the roll crown in a predetermined state. In addition, for example, the vicinity of the bearing is cooled, which causes a problem that the service life is shortened, which is caused by the following causes. For example, when the carburizing atmosphere gas reaches the vicinity of the hearth roll, cooling is performed so that sooting progresses. Therefore, C adheres to the hearth roll and then diffuses into the hearth roll.
When this occurs, the Cr and C are combined to precipitate Cr carbide, thereby breaking or expanding the crystal grains of the heat-resistant alloy used for the hearth roll, while dissolving the solid solution Cr.
Therefore, the hearth roll is embrittled and oxidized, so that corrosive corrosion progresses. When the hearth roll is exposed to the carburizing atmosphere gas as described above, experiments by the present inventors have revealed that the hearth roll must be replaced within one year.

Therefore, in this embodiment, the hearth roll chamber 12
Is separated from the carburizing atmosphere by the non-contact sealing device 11 to prevent the deterioration of the hearth roll 10, and the inside of the hearth roll chamber 12 is set to a weakly carburized state such that the deterioration of the hearth roll 10 does not progress. As a result, it was possible to prevent so-called decarburization in which C diffuses from the carburized surface layer while the strip S passes through the separated hearth roll chamber 12. In addition, when the time for the strip S to pass through the hearth roll chamber 12 is extremely short, and there is no problem with decarburization from the surface layer of the steel sheet during the time,
The interior of the hearth roll chamber 12 may be a non-carburized atmosphere.

The non-contact type sealing device 11 includes, for example, a seal layer interposed between a hearth roll chamber 12 and a carburizing atmosphere chamber (heat treatment chamber) 13 and three layers of unitized seal units 14a to 14c. The weak carburizing atmosphere gas is discharged as a sealing gas to the sealing unit 14a on the hearth roll chamber 12 side, and the carburizing atmosphere gas is discharged as a sealing gas to the sealing unit 14c on the carburizing atmosphere chamber side. Is discharged from the seal unit 14b, and the discharge direction and discharge flow rate of the seal gas from each nozzle are controlled so that the flow of each seal gas, that is, the direction of forming the static pressure is the intermediate seal unit 1b.
4b, and the circulating flow generated by the laminar flow accompanying the passing of the strip is exhausted from the side discharge port 17 formed at the end face in the width direction of the strip in each seal unit. . Since these specific components are the gist of the present invention, they will be described in detail later.

Also, a number of radiant tubes 15 are arranged near the strip S through which each pass is passed. The radiant tube 15 controls the temperature in the carburizing furnace (mainly heating and soaking control) by radiating heat from the tube surface by burning the fuel gas fed into the tube. The amount is controlled by the supply amount of the combustion gas similarly to the heating zone 2 and the soaking zone 3, and this is also importantly managed by the host computer (not shown) according to the control logic. In addition, in the industrial continuous carburizing operation, in order to stably achieve the desired metal band specifications with a limited effective carburizing length (carburizing time), the carburizing atmosphere gas composition in the carburizing furnace, especially in the heat treatment chamber, It is essential to make the atmosphere such as gas composition concentration and carburizing temperature uniform.

The strip S delivered from the carburized zone 4
Is supplied to the first cooling zone 5. In the first cooling zone 5, since the solid solution C is fixed only in a very thin area of the surface in the surface layer portion of the strip, the strip after carburizing has a steel sheet temperature of 600 ° C or less, preferably about 500 to 400 ° C. Rapid cooling at a cooling rate of 20 ° C./sec. In the first cooling zone 5, a flow rate, a flow rate and a cooling roll of a cooling gas blown from a cooling gas jet to a strip conveyed in the cooling zone by the host computer are set so as to achieve the cooling condition. Temperature, winding angle, etc. are controlled.

The strip S sent from the first cooling zone 5 is then sent to the second cooling zone 6. In the second cooling zone 6, gas cooling is performed to a steel sheet temperature of about 250 to 200 ° C. Thus, finally, a cold-rolled steel sheet for press forming with extremely low carbon in which solid solution C exists only in the surface layer can be obtained. Next, the respective components required for the above-mentioned non-contact type sealing device will be described based on experiments actually performed.

First, the non-contact type sealing device of this embodiment is
It has been developed to achieve the following objects as well as to enhance the sealing performance. As described above, if the carburizing atmosphere gas in the heat treatment chamber leaks into the hearth roll chamber, damage to the hearth roll occurs or accelerates. On the other hand, if a weakly carburizing atmosphere gas or a non-carburizing atmosphere gas in the hearth roll chamber leaks into the heat treatment chamber, a concentration distribution occurs in the carburizing atmosphere, and the carburizing amount varies in the sheet width direction or the sheet passing direction. This phenomenon becomes more remarkable when performing the industrial continuous carburizing operation as described above. Therefore, in this non-contact type sealing device, it is necessary to suppress the leakage of the mutual atmospheric gas between the two divided atmospheres as much as possible. Further, the plate surface of the strip may fluctuate due to meandering or the like, and if the plate surface comes into contact with a discharge nozzle or an exhaust nozzle of the seal gas due to the fluctuation of the plate surface, a flaw may be generated. For this reason, it is necessary that at least each nozzle is separated from the strip plate surface as much as possible. Furthermore, in order to make the effective carburizing furnace length of the carburizing zone as long as possible, it is necessary to consolidate each seal length within a predetermined range. Of course, from the viewpoint of energy saving, the smaller the amount of the sealing gas discharged, that is, the smaller the supply amount of the sealing gas, the better.

Therefore, in this embodiment, as shown in FIG. 4, a plurality of nozzles 16a and 16b facing each plate surface are provided, and a side exhaust port 17 is provided on the side of the strip S in the width direction to form the seal units 14a to 14a. 14c, one or more of these seal units 14a to 14c are laminated along the plate surface of the strip S, and the discharge of the seal gas from each of the nozzles 16a and 16b, the seal gas by each of the nozzles 16a and 16b, In order to simultaneously discharge the gas in the vicinity, the following parameters were changed, and the sealing performance between the atmospheres in the room A and the room B shown in the figure was examined.

More specifically, each of the seal units 14a to 14
c, the strip S
Nozzles 16a, 16b extending in the width direction
Are arranged side by side along the plate surface of the strip S. For convenience, A in each of the seal units 14a to 14c
The nozzle on the chamber side is referred to as a nozzle 16a, and the nozzle on the chamber B side is referred to as a nozzle 16b. In addition, these nozzles 16a, 1
6b is capable of individually injecting and discharging an appropriately selected seal gas, and sucking and exhausting the seal gas and a nearby gas. Further, the discharge angle of the seal gas from the discharge nozzle can be changed in the direction in which the adjacent nozzles face each other in the unit. Also,
The side exhaust port 17 of each unit can be switched between exhaust, cutoff, and discharge as needed. Further, the interior of the chamber A was regarded as a hearth roll chamber, the atmosphere of which was equivalent to air, and the interior of the chamber B was regarded as a heat treatment chamber, and a mixed gas of nitrogen N ₂ and helium He was introduced. In addition, the method of evaluating the sealing properties is based on the flow state of each atmosphere gas, the oxygen O ₂ concentration in each chamber, the discharge flow rate of the seal gas (the smaller the better, the better the exhaust flow rate from each chamber). The flow state of each atmosphere gas was evaluated in consideration of the passing of the strip.

Next, among the above parameters, the seal gas discharge / exhaust pattern for each nozzle will be described.
For example, when the seal unit has a three-layered structure as shown in FIGS. 3 and 4, this seal gas discharge / exhaust pattern is discharged from the nozzles 16a and 16b opposed to each other across the strip S in FIG. Alternatively, it is conceivable that ₂排 気₆ = 64 ways, 16 ways in the case of two seal unit layers, and four cases in the case of one seal unit layer (single layer) even when performing either exhaust or exhaust. Further, whether to perform exhaust from the side exhaust port is also added to this. For the discharge / exhaust state of the seal gas from each nozzle and the side exhaust port, see FIG. 4 as a legend.

Next, since the discharge angle of the seal gas can be an important parameter for the air flow generated in the seal device as described above, the discharge angle θ of the seal gas is arranged in parallel for each unit as shown in FIG. The experiment was performed by changing the direction of the nozzles 16a and 16b to face each other. Note that each ejection angle θ is determined by the nozzles 16a and 16b adjacent to each other.
The strips are changed so as to face inward with respect to the plate surface, and the set discharge angles of the respective nozzles 16a and 16b do not have to be the same.

Next, according to the discharge angle of the seal gas, the discharge flow ratio of the seal gas of each nozzle can be an important parameter for the air flow generated in the seal device. This is because, in each seal unit, for example, as shown in FIG.
And the gas flow rate β of the nozzle 16b that may leak. That is, α / β in FIG.
In the experiment, the nozzle discharge flow rate α on the side not to be leaked,
The nozzle discharge flow rate β on the side that may leak may be changed under the condition of α ≧ β.

Next, as shown in FIG. 7, the composition of the seal gas is discharged from the nozzle 16a on the air atmosphere side, ie, the chamber A side, and the nozzle 16a on the N ₂ atmosphere side, ie, the chamber B side.
b when N ₂ is discharged from all nozzles 16a, 1
A comparison is made when N ₂ is discharged from 6b. According to this experiment, by using a sealing gas having the same composition as the atmosphere in the discharge nozzle on the side to be sealed, that is, the nozzle in the immediate vicinity of the atmosphere, it is determined whether or not the maintenance of the atmosphere composition can be expected even if a leak occurs. You.

Next, as described above, a circulating flow of the sealing gas is generated on the lateral side of the strip S as shown in FIG. 8, and this circulating flow may induce leakage of the sealing gas or the atmospheric gas. There is. Therefore, exhaust is performed from the side exhaust port 17 provided in each of the seal units 14a to 14c, and the ratio of the amount of exhaust from the side exhaust port to the amount of exhaust from the exhaust nozzle is changed to change the amount of the seal gas. The effect of leak reduction was tested.

From the above experimental results, in the seal gas discharge / exhaust pattern, good sealing effect was obtained in the following two patterns. Pattern 1: Seal unit 14 on room A and room B
The seal gas is discharged from all the nozzles 16a and 16b of the a and 14c, the exhaust is performed from all the nozzles 16a and 16b of the central seal unit 14b, and the side of the seal units 14a and 14c on the A chamber side and the B chamber side. One that exhausts only from the exhaust port 17.

Pattern 2: Seal unit 14 on chamber A side
a, the sealing gas is discharged from the nozzle 16b on the side of the chamber B, and the nozzle 16a on the side of the chamber A is exhausted.
And discharges the seal gas from the nozzles 16b on the side of the chamber B, discharges the seal gas from all the nozzles 16a and 16b of the central seal unit 14b, and discharges the side gas outlets 17 of the central seal unit 14b. Exhaust only from

As described above, when the side exhaust was performed from the side exhaust port near the discharge nozzle, remarkable seal goodness was exhibited. FIG. 9 shows the result of investigating the influence of the discharge angle of the seal gas on the sealability. In this experiment, as shown in the figure, exhaust was performed from all the nozzles 16a and 16b of the seal units 14a and 14c on the chamber A side and the chamber B side, and all the nozzles 1 of the central seal unit 14b were exhausted.
The seal gas is discharged from 6a and 16b, and the discharge angle of the seal gas is θ = 90 ° (straight) shown in FIG.
And the case where θ = 45 °, the O ₂ concentration in each room was detected. In addition, N ₂ gas was used as the seal gas, the total input amount of the seal gas was constant at aNl / min, and the flow rate of the seal exhaust gas was changed. As can be seen from the figure, when the seal exhaust flow rate is increased, the discharge angle of the seal gas is θ = 45 ° compared to the case of θ = 90 °, that is, the inner angle with respect to the plate surface of the metal strip to be passed. It can be seen that the sealability is significantly improved by making the direction opposite to the oblique direction.

Next, FIG. 10 shows the results of an investigation on the effects of the amount of sealing gas supplied and the amount of exhaust gas on the sealing performance. In this experiment, as shown in the figure, exhaust was performed from all the nozzles 16a, 16b of the seal units 14a, 14c on the chamber A side and the chamber B side, and the seal gas was discharged from all the nozzles 16a, 16b of the central seal unit 14b. Discharge was performed, and the discharge angle of the seal gas was set so that θ = 45 °. Under these conditions, the total input amount of the sealing gas is bNl / min.
The O ₂ concentration in each room when the seal exhaust flow rate was changed was detected for the case of and the case of cNl / min (where c = 3.5b). Note that N ₂ gas was used as the sealing gas. As can be seen from the figure, when the input amount of the sealing gas is increased, the sealing performance is improved by exhausting the gas in an amount corresponding thereto. Also,
In this seal gas discharge / exhaust pattern, it was found that a function as a seal was achieved by satisfying the condition of exhaust amount ≧ injection amount of seal gas.

Next, FIG. 11 shows the result of investigation on the effect of the nozzle flow rate ratio on the sealing performance. In this experiment, as shown in the figure, as shown in FIG.
The discharge of the seal gas is performed from all the nozzles 16a and 16b of 14c, and the discharge is performed from all the nozzles 16a and 16b of the central seal unit 14b, and the discharge angle of the seal gas is set to be θ = 60 °. . Under these conditions, based on the findings in FIG.
For the case of Nl / min and the total displacement eNl / min (where d <e), the O ₂ concentration in each chamber when the nozzle flow rate ratio was changed was detected. In this case, each room side is as shown in FIG.
In the seal unit 14a on the A-room side, the discharge flow rate of the nozzle 16a on the A-room side is set to α, The discharge flow rate of the nozzle 16b is β, the discharge flow rate of the nozzle 16b of the B chamber side is α, and the discharge flow rate of the nozzle 16a of the A chamber is β in the seal unit 14c on the B chamber side. And As is clear from the figure, the nozzle flow ratio α / β is increased, that is, the seal gas discharge flow α of the nozzle on the partitioned chamber side is
It can be seen that the sealing performance is improved by making the flow rate β of the sealing gas discharged from the adjacent nozzles relatively large.

Next, FIG. 12 shows the result of investigation on the effect of the sealing gas composition on the sealing performance. In this experiment, as shown in FIG.
Air is discharged from the chamber-side nozzle 16a, and the adjacent nozzle 1 is discharged.
N ₂ gas is discharged from 6b, and the sealing unit 1 on the B chamber side is discharged.
4c, N ₂ gas is discharged from all the nozzles 16a, 16b, and all the nozzles 16a of the central seal unit 14b are discharged.
The gas was exhausted from a and 16b, and the discharge angle of the seal gas was set so that θ = 60 °. Under these conditions, the total input amount of the seal gas was fNl / min as in FIG.
, The total exhaust amount gNl / min (where f <g), the O ₂ concentration in each chamber when the nozzle flow rate ratio was changed was detected. In this case as well, it is assumed that each chamber side corresponds to the direction in which leakage is not desired in FIG. 6 and the center seal unit side corresponds to the direction in which leakage is possible. Let the discharge flow rate of the nozzle 16b on the chamber B side be β,
In the chamber side seal unit 14c, the nozzle 16b on the chamber B side
Is the discharge flow rate of α, and the discharge flow rate of the nozzle 16a on the chamber A side is β.
Α / β is defined as the nozzle flow rate ratio. As is clear from the figure, a gas having the same composition as the atmosphere in the chamber is discharged from the seal nozzle on the side of the partitioned chamber, and the nozzle flow ratio α / β is further increased, that is, the nozzle of the partitioned chamber is sealed. It can be seen that the sealing performance is dramatically improved by increasing the gas discharge flow rate α relative to the discharge flow rate β of the adjacent nozzles.

As described above, a seal device is formed by laminating two or more seal units each having a combination of a discharge nozzle and an exhaust nozzle and provided with a side exhaust port. By performing the exhaust, high sealing performance can be ensured. Also, when discharging from adjacent nozzles in each seal unit,
The discharge angle of the seal gas is inclined so as to face inward with respect to the strip plate surface, and the discharge flow rate on the atmosphere side to be partitioned is relatively increased to generate a gas flow of the seal gas. By stopping the flow of the gas along the surface (changing the direction of the flow) and disposing an exhaust nozzle in front of this gas flow, the sealing performance is improved. Also, if the total displacement of the sealing device is not more than the total input of the sealing gas,
This type of non-contact sealing device does not work well. Further, by discharging the atmosphere gas as a seal gas from a nozzle closest to the atmosphere, a change in the atmosphere can be suppressed.

FIG. 13 shows one ideal structure of the non-contact type sealing device from the results of these experiments. This non-contact type sealing device has three layers of sealing units 14a, 14b, 14c.
Of the seal unit 14a on the atmosphere A side, discharges the seal gas from all the nozzles 16a and 16b, and discharges or shuts off from the side exhaust port 17 as necessary. Seal unit 14
c, the seal gas is discharged from all the nozzles 16a and 16b, and the side exhaust port 17 is evacuated or shut off as necessary.
The air is exhausted from a and 16b, and the side exhaust port 17 is shut off or exhausted as necessary. Then, as described in the present invention, the seal unit 14a on the atmosphere A side
The discharge angles of the nozzles 16a and 16b on each plate surface side are inwardly opposed to each other, the flow rate ratio α / β between them is set to 2 to 4, and the seal unit 14 on the atmosphere B side is set.
The discharge angles of the nozzles 16a and 16b on each plate surface side of c are set to face inward and the flow ratio α / β of both nozzles is set to 2 to 4. Then, the atmosphere A gas is supplied as a seal gas to the nozzle 16a on the atmosphere A side of the seal unit 14a on the atmosphere A side, and the atmosphere A or B or a C gas different from them is used as the seal gas for the nozzle 16b on the atmosphere B side. Supply. On the other hand, the atmosphere B gas is supplied as a seal gas to the nozzle 16b on the atmosphere B side of the seal unit 14c on the atmosphere B side, and the atmosphere B or A or a C gas different therefrom is supplied to the nozzle 16a on the atmosphere A side. Supply. In this non-contact type sealing device, the gas flow in the sealing member is optimized with a small supply amount of the sealing gas, and at the same time, the exhaust efficiency is increased to suppress the leakage between the atmospheres and the disturbance of each atmosphere due to the sealing gas leakage is suppressed. be able to.

In the present embodiment, only the case of continuous annealing and carburizing of a strip made of ultra-low carbon steel is described in detail. However, the non-contact type sealing device of the atmospheric furnace of the present invention is not limited to the carburizing furnace, but may be any type. It goes without saying that the present invention can be applied to a seal between partitioned atmospheres. Further, the seal device of the present invention has been described by taking a vertical furnace as an example, but the seal device can also be applied to a horizontal furnace.

Further, the nozzles facing inward need not necessarily be close to the atmosphere in which they are defined.
What is necessary is just one near each atmosphere. In that case,
It is necessary to take measures to avoid leakage of the seal gas as much as possible by exhausting air from a nozzle closer to the atmosphere.

[0044]

As described above, according to the non-contact type sealing device of the atmospheric furnace of the present invention, a relatively small amount of the sealing gas supplied from the adjacent inward facing nozzles near each of the divided atmospheres is supplied. The optimum flow of gas for sealing can be formed between the metal strip and the surface of the metal strip by the input amount. By appropriately setting the interval between the two nozzles facing inward, the sealing performance between the two atmospheres is improved. I do. In each of the inward facing nozzle configurations, the flow rate of the seal gas discharged from the nozzle closer to the atmosphere is made larger than the flow rate of the seal gas discharged from the other nozzle, so that the static pressure forming direction The sealing gas to the center of the entire sealing device to suppress leakage of the sealing gas to each atmosphere side, and simultaneously discharge the sealing gas or the atmosphere gas flowing into the vicinity thereof, thereby further improving the sealing performance. Can be. Accordingly, in the non-contact type sealing device of the atmospheric furnace according to the present invention which can secure such high sealing performance, for example, the interval between the plate surface of the metal strip to be passed and the nozzle opposed thereto is widened, The generation of flaws due to surface fluctuations can be prevented.

[Brief description of the drawings]

FIG. 1 is a conceptual explanatory view of a heat treatment step performed in a continuous annealing carburizing facility.

FIG. 2 is a schematic configuration diagram showing an example of a continuous annealing carburizing facility using a non-contact sealing device of an atmosphere furnace of the present invention.

3 shows a continuous gas carburizing furnace used in the continuous annealing carburizing equipment of FIG. 2, (a) is a longitudinal sectional front view,
(B) is a longitudinal sectional side view.

FIG. 4 is a schematic configuration diagram showing an example of a non-contact type sealing device used in the carburizing furnace of FIG.

FIG. 5 is an explanatory diagram of a discharge angle of a seal gas in the non-contact type sealing device of FIG. 4;

FIG. 6 is an explanatory diagram of a seal gas flow ratio from each nozzle in the non-contact type sealing device of FIG. 4;

FIG. 7 is an explanatory diagram of a change in the composition of the seal gas from each nozzle in the non-contact type sealing device of FIG. 4;

FIG. 8 is an explanatory view of a circulating flow and a side exhaust generated laterally in the strip width direction in the non-contact type sealing device of FIG. 4;

FIG. 9 is an explanatory view of the result of an experiment of sealing performance performed by changing the discharge angle of the sealing gas in the non-contact type sealing device of FIG. 4;

FIG. 10 is an explanatory diagram showing the results of an experiment on sealing performance in the non-contact type sealing device of FIG. 4 by changing the discharge flow rate (total input amount) of the seal gas and the exhaust flow rate.

FIG. 11 is an explanatory diagram showing the results of an experiment on sealing performance in the non-contact type sealing device of FIG. 4 with the flow rate ratio of the sealing gas discharge nozzle changed.

FIG. 12 is an explanatory view showing the results of an experiment on sealing performance in the non-contact type sealing device of FIG. 4 with the composition of the sealing gas and the discharge nozzle flow ratio changed.

FIG. 13 is a detailed explanatory view of a seal gas discharge / exhaust structure of the non-contact seal device employed in this embodiment.

[Explanation of symbols]

 1 is a pre-tropical zone 2 is a heating zone 3 is a level zone 4 is a carburizing zone 5 is a first cooling zone 6 is a second cooling zone 10 is a hearth roll 11 is a sealing device 12 is a hearth roll room 13 is a heat treatment room 14a to 14c is a seal zone Unit 15 is a radiant tube 16a, 16b is a nozzle 17 is a side exhaust port S is a strip

Continuation of the front page (72) Inventor Noriaki Hanazono 1-chome, Mizushima-Kawasaki-dori, Kurashiki-shi, Okayama Pref. Mizushima Works, Kawasaki Steel Corporation JP-A-55-33550 (JP, A) JP-A-60-238426 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C21D 9/56 101 C21D 1/00 112 C21D 1/74 F27D 7/06

Claims (1)

(57) [Claims] 1. An atmosphere furnace for controlling an atmosphere around a metal strip to be passed, wherein at least a sealing gas is supplied to the metal strip to separate the atmosphere and individually control each of the partitioned atmospheres. A seal unit having a plurality of nozzles opposed to the metal strip plate surface for discharging in a direction having a component perpendicular to the plate surface or for discharging the seal gas or a gas in the vicinity thereof is provided with a metal strip. In a non-contact type sealing device for an atmosphere furnace formed by laminating a plurality of nozzles along a plate surface, a plurality of nozzles arranged in parallel with each other along the plate surface facing each plate surface of the metal strip, each of the nozzles being closer to the atmosphere. The two nozzles adjacent to each other are inwardly opposed to the plate surface, and of the seal gas discharged from the two nozzles, the flow rate of the seal gas discharged from the nozzle closer to the atmosphere is set to the other nozzle. Spitting A non-contact type sealing device for an atmosphere furnace, wherein the flow rate is larger than a flow rate of a sealing gas to be discharged.