WO2019221496A1 - Atmospheric gas sealing means for continuous-thermal treatment furnace and control method therefor - Google Patents

Abstract

The present invention relates to an atmospheric gas sealing device for controlling hydrogen concentration of a rapid cooling zone in a continuous-thermal treatment furnace for continuously heat-treating a steel plate, and a pressure control method for the atmospheric gas sealing device and, more specifically, to an atmospheric gas sealing device for a continuous-thermal treatment furnace, which is installed between a rapid cooling zone and an annealing zone or between the rapid cooling zone and an over-aging zone, forms a pressure barrier between a first nozzle and a second nozzle facing each other, and controls a pressure in a buffer space between pressure barriers to be higher than a pressure of a first furnace band and a pressure of a second furnace band, and to a sealing device which maintains hydrogen concentration in an adjacent furnace band to be in a low level of concentration of 5% while maintaining concentration of a hydrogen gas in a rapid cooling zone up to maximum of 99% on the basis of a volume thereof through a pressure control method.

Description

Atmospheric gas sealing means and control method in continuous heat treatment furnace

The present invention relates to an atmosphere gas sealing apparatus for controlling the hydrogen concentration of the rapid cooling zone of the continuous annealing furnace, and more particularly, is installed at the entry and exit side of the rapid cooling zone to up to 99% of the hydrogen gas concentration in the rapid cooling zone. While maintaining, the concentration of hydrogen in adjacent furnace bands relates to a non-contact gas seal that can maintain a low concentration level of 5%.

In general, in the continuous annealing furnace for continuously heat treatment of the steel sheet, the steel sheet is heat-treated while passing through the heating table, the cracking zone and the cooling zone. Among them, the heating zone and the cracking zone are heat treatment furnaces that raise the temperature of the steel sheet to the recrystallization temperature near about 800 ° C. The cooling stage undergoes the heat treatment process while passing through the quick cooling stage and the slow cooling stage according to the required cooling conditions according to the heat treatment cycle of the steel sheet. Proceed.

In order to prevent oxidation of the steel sheet, the continuous heat treatment furnace generally uses a reducing gas containing hydrogen gas 5% and nitrogen gas 95% as an atmosphere gas, and to prevent external oxygen from penetrating into the furnace. The internal pressure is maintained at a positive pressure of about 200 Pa.

In order to produce ultra-tensile steel with increasing demand in recent years, high-speed cooling of 100 ^o C / s or more is required in certain sections of continuous heat treatment furnaces, that is, rapid cooling zones. In the high-speed cooling, a gas jet cooling method of cooling the steel sheet by injecting the hydrogen-nitrogen mixed gas in the quick cooling zone and spraying the moving steel sheet is mainly used.As the cooling rate increases as the concentration of hydrogen in the mixed gas increases, the cooling rate increases. Hydrogen concentrations of 30 to 60% are maintained in the rapid cooling zone.

Accordingly, a high concentration of hydrogen atmosphere is required in the rapid cooling zone, 5% hydrogen atmosphere is required in the peripheral heat treatment zone, and a sealing device is installed to prevent gas from being mixed between the rapid cooling zone and the surrounding furnace zone.

In the case of a conventional atmospheric gas sealing device using a continuous heat treatment, a method of blocking atmospheric gas by simply contacting a steel plate, a sealing roll, and an elastic material, such as Japanese Patent (JP 03071114), is used. In order to prevent the elastic sealing material to be in frictional contact with the roll, not only maintenance is necessary, but also gas is leaked through the gap between the rolls according to the wear and deformation of the elastic sealing material, there is a limit to effectively block the atmospheric gas.

In addition, in case of using such a sealing roll, domestic patents 10-1717960 and Japanese Patent Laid-Open Publication No. 2006-307244 use an atmosphere gas without using an elastic sealing material by injecting a gas into a gap between the roll and the steel sheet due to the thickness of the steel sheet. It is presented a method of sealing. However, this method has a problem in that the sealing efficiency is deteriorated because the possibility of gas leakage through the bearing part of the sealing roll and the entry and exit of gas through the gap between the sealing roll and the nozzle cannot be controlled stably.

Due to the above problems, a non-contact gas sealing device has been devised. Especially, in the case of Japanese Patent No. 4291839, a sealing device having a duct for extracting a gas for sealing and a retractable member between two chambers, and a sealing device for exhausting gas between the ducts is provided. Although it has been proposed, there is a problem in that the hydrogen consumption for exhausting the mixed gas used in the sealing apparatus to the outside of the furnace and maintaining the hydrogen concentration in the furnace due to the limitation that the openable member cannot be brought into full contact with the steel sheet. In addition, there is a problem that the sealing device and the steel sheet is damaged by the frictional contact between the sealing device and the steel sheet is not proposed means for correcting the widthwise shape imbalance, such as C-shaped bending of the steel sheet appearing in the continuous heat treatment furnace.

<Preceding technical literature>

(Patent Document 1) Japanese Patent No. 03071114

(Patent Document 2) Japanese Unexamined Patent Publication 2006-307244

(Patent Document 3) Domestic Patent 10-1717960

(Patent Document 4) Japanese Patent No. 4291839

This invention is made | formed in view of the said conventional problem, The slow cooling stand of the high concentration nitrogen atmosphere which adjoins the rapid cooling zone of high concentration hydrogen atmosphere in the sealing means of the continuous heat treatment furnace using gas like the said patent document 4, and Installed between overaging zones, it prevents the hydrogen gas leaking out of the sealing device through the gap between the sealing device and the steel plate to reduce the expensive hydrogen consumption, and flatten the shape of the moving steel plate in the sealing device. Stable operation of the sealing means and the sealing means in the continuous heat treatment furnace to prevent damage to the sealing device and the steel sheet by preventing the leakage and flow of the hydrogen-nitrogen mixed gas through the sealing rotary roll as in Patent Document 3 It is an object of the present invention to provide a pressure control method.

In order to achieve the above object, the atmosphere gas sealing means and control method of the continuous heat treatment furnace according to the present invention, the first furnace band (quick cooling zone) of the hydrogen atmosphere and the second furnace zone (slow cooling zone or overaging zone of nitrogen atmosphere) A pair of rotary rolls installed between the plate and rotating while contacting the steel sheet; A pair of first nozzles installed on an upstream side of the rotary roll to inject gas sucked from the first furnace band toward each other with a steel plate therebetween; A pair of second nozzles installed on the downstream side of the rotary roll and for injecting the gas sucked from the second furnace band toward each other with the steel plates interposed therebetween; The distance between the first nozzle and the second nozzle and the steel sheet is maintained within a maximum of 50 mm; The pressure of the first nozzle and the second nozzle is greater than the pressure having the greater of the pressures of the first furnace band and the second furnace band; The sealing device is stably controlled by changing the pressure of the first nozzle and the pressure of the second nozzle in association with the pressure fluctuations of the first furnace band and the second furnace band. Here, the width of the whole roll including the bearing portion is smaller than the width of the sealing chamber, the gap between the rotating roll and the steel sheet is adjusted through a transfer mechanism connected to the bearing portion.

According to the present invention, the widthwise shape of the steel sheet can be flattened by the rotational roll provided in the sealing means, so that the nozzle can be brought into close proximity to the steel sheet. There is an increasing effect. The rotary roll installed in the buffer space between the upstream and downstream nozzles prevents the leakage of gas through the rotary roll bearing part because the bearing portion does not penetrate the sealing chamber and contacts the steel sheet in the buffer space. It is effective.

In addition, since the buffer space is sealed, a high stagnation pressure is stably formed by the gas injected from the nozzle, so that the sealing device can be stably operated for a long time without a mechanical shielding means, and a pair of nozzles respectively installed on the upstream side and the downstream side Since most of the gas injected from the gas is discharged into the furnace band in which the gas supplied to the nozzle is sucked, the inflow of the atmosphere gas of the opposite side into each furnace band is completely blocked. Accordingly, in the rapid cooling zone that requires a high concentration of hydrogen atmosphere, the conventional rapid cooling zone hydrogen concentration, which remained at the maximum 65% level, is stably increased up to 99% by the sealing means according to the present invention.

As described above, by not leaking hydrogen gas to the outside of the sealing device, the expensive hydrogen consumption in operating the sealing device is reduced, and the risk of fire and explosion due to the leakage of hydrogen gas increases, thereby increasing the safety of the facility. There is an effect of enabling the rapid cooling of the steel sheet by improving the atmosphere gas blocking efficiency of the furnace.

1 is a schematic diagram of an atmosphere gas sealing apparatus of a continuous heat treatment furnace according to the present invention;

2 is a schematic view in cross section perpendicular to the steel plate traveling direction of the atmosphere gas sealing apparatus of the continuous heat treatment furnace according to the present invention;

3 is a pressure distribution of the sealing device and the adjacent furnace band by the pressure control method of the sealing device according to the present invention.

Figure 4 is an embodiment of the atmosphere gas concentration control by the pressure control method of the sealing device according to the present invention

5 is an embodiment for the stable operation of the atmospheric gas concentration by the pressure control method of the sealing device according to the present invention.

In order to achieve the above object, the present invention provides a sealing means provided between the first furnace band (quick cooling zone) of the hydrogen atmosphere and the second furnace zone (slow cooling zone or overaging zone) of the nitrogen atmosphere in the continuous heat treatment furnace of the steel sheet In more detail, the first furnace band 20 and the second furnace zone 22 to seal the dynamic pressures P ₀₂ and P ₀₃ of the impinging jets spraying the steel plates with the steel plates interposed therebetween in detail. It is related with the sealing means which stably prevents the gas of each furnace band flowing to an adjacent furnace zone by making it larger than a low pressure.

Hereinafter, the present invention will be described in detail with reference to the drawings.

1 shows a sealing means of the opposite impact jet method according to the present invention. The sealing means is provided between the first furnace zone 20 and the second furnace zone 22 of the steel plate continuous heat treatment furnace, and the sealing gas is injected from the opposite side toward the steel plate with the moving steel plate 1 therebetween. The gas chamber and the spray nozzles 2a, 2b, 3a, and 3b, the non-driven roller 5 for correcting the shape of the steel plate and preventing vibration, the feed mechanisms 7 and 8 of the roller, and the roller A buffer space 21 surrounded by the use gas chamber and the nozzle, and blowing means 9 for sucking gas in each furnace band and supplying gas to the injection chamber after heat exchange.

The first furnace zone 20 is a rapid cooling zone in which a high concentration of hydrogen gas atmosphere is maintained, and the second furnace zone 22 represents a slow cooling zone or an overageing zone, but each furnace zone is a rapid cooling zone. It is not limited to cold or overaging, and can be extended to any furnace bands required to maintain different atmosphere gases. In the first furnace band 20, rapid cooling is performed by spraying a high concentration of hydrogen gas on the steel sheet at high speed, and thus the pressure in the first furnace band 20 is maintained relatively higher than that of the second furnace band 20. do.

In the continuous heat treatment furnace, the steel sheet is uneven in the width direction while passing through a plurality of rolls, and the cross section of the steel sheet is curved in a C-shape. As such, when the steel sheet having the C-bent shape passes through the spray nozzle of the sealing device, the steel sheet and the nozzle are in frictional contact, causing damage to the steel sheet and the nozzle. The sealing device according to the present invention is provided with a pair of rotary rolls 5 in contact with the steel sheet in the buffer space 21 to correct the C-curve shape so that the distance h between the steel sheet and the nozzle is within a maximum of 50 mm. Close to maximize the impact pressure of the jet flow (4). Here, although the position of the rotary roll 5 is shown in the same position in the advancing direction of the steel plate in FIG. 1, the rotation axis position of the two rotary rolls 5 may be in a different position in the advancing direction of the steel plate. In addition, the two rotary rolls 5 may be located in the adjacent furnace bands 20 and 22 outside the buffer space 21 in the sealing device, but as described above, the C bending of the steel sheet is corrected by the rotary rolls 5. It must be within the limits of what can be done.

Fig. 2 is a schematic view of the sealing device in a cross section perpendicular to the traveling direction of the steel sheet, wherein the pair of rotary rolls 5 are conveyed in the thickness direction of the steel sheet by a conveying mechanism 8 and a motor 7 connected to the bearing part. This is possible, and the position of the rotary roll is changed in response to the thickness change of the steel sheet. The width direction length including the bearing part of the rotary roll 5 is smaller than the width of the chamber 10 of the sealing device, so that the free movement in the thickness direction of the steel sheet is possible, and there is no driving part for the rotation of the roll 5. It rotates by the friction by the contact pressure of a steel plate. The jets 4 sprayed from the spray nozzles 2a and 2b of the sealing device are sprayed uniformly over the entire width of the chamber 10, some of which impinge on the surface of the steel sheet, and some of which are sprayed in opposite directions. It collides with the jet flow to create stagnant pressure.

Figure 3 shows the pressure distribution and the regulation method in the sealing device and the adjacent furnace band according to the present invention. According to the present invention, in the state where the pressure P ₂₀ of the first furnace zone 20 in the hydrogen atmosphere is kept larger than the pressure P ₂₂ of the second furnace zone 22 in the nitrogen atmosphere, the sealing device injection nozzle ( The stagnation pressure P ₂₁ formed by the jet flows of 2a and 3a is adjusted by the blowing means 9 connected to the injection nozzle so as to be made larger than the pressure P ₂₀ of the first furnace zone 20 (P ₂₁ > P ₂₀ > P ₂₂ ). Here, when the distance h between the injection nozzles 2a and 3a and the steel sheet 1 or the opposite injection nozzles 2b and 3b becomes large, the injection nozzles 2a and 3a and the steel sheet 1 or the opposite injection nozzles are increased. (2b, 3b) static pressure in the pressure barrier (P _{0_2,} P _{0_3),} the buffer space 21 is not formed between the (P ₂₁₎ is not formed, as a stagnant pressure by the sealing device (P _21), stably The distance h between the nozzles 2a, 2b, 3a, 3b and the steel sheet can be maintained within 50 mm so as to be maintained. In addition, when the buffer space 21 between the nozzles of the sealing device is narrow, the pressure P _{22 in the} buffer space 21 becomes larger than the pressure barriers P _{0_2} and P _{0_3} , so that stagnant pressure P ₂₁ cannot be stably maintained. Therefore, the distance L2 between the nozzles of the sealing device must be at least larger than the size L1 of the sealing chamber (L2 > L1). Here, the size of the buffer space and the size of the sealing chamber means a space formed by the width of the L1, L2 and the sealing chamber.

As described above, the pressure barriers P _{0_2} and P _{0_3} are formed between the opposite injection nozzles of the sealing device, and the pressure P ₂₁ of the buffer space between the pressure barriers is _equal to the pressure P ₂₀ of the first furnace band and the second. By controlling it to be larger than the pressure P ₂₂ of the furnace band, the mixed gas in the buffer space introduced from the first furnace band 20 and the second furnace band 22 is prevented from flowing into each furnace band.

In addition, the supply pressure P _{0_3} of the first nozzles 3a and 3b and the supply pressure P _{0_2} of the second nozzles 2a and 2b are _{equal to} the pressure P ₂₀ of the first furnace band and the second furnace band. By controlling the pressure P ₂₂ to change, the pressure balance of each furnace zone and the sealing device is kept stable.

4 shows an embodiment of controlling the hydrogen concentration in the first furnace zone 20 by the pressure control method of the sealing device according to the present invention. Hydrogen and nitrogen are mixed in a certain ratio in the first furnace zone 20, only nitrogen is maintained in the second furnace zone 22, and the pressure P ₂₀ of the first furnace zone ₂₀ is the first furnace zone 22. In a state greater than the pressure P ₂₂ ), the hydrogen concentration in the first furnace zone 20 and the hydrogen concentration in the second furnace zone 22 are increased as the hydrogen supply amount is increased in the first furnace zone 20, and pressure of the first nozzle in the sealing apparatus (P _{0_3)} to the pressure of the second nozzle (P _{0_2),} the pressure of the first furnace zone ₍₂₀₎ (P 20) can change is shown. As hydrogen is supplied to the first furnace band 20, the hydrogen concentration of the first furnace band 20 may be increased without hydrogen leaking into the second furnace band 22, and finally, the second furnace band. It can be seen that the hydrogen concentration in the first furnace zone 20 increases stably to 99% while maintaining the hydrogen concentration of (22) at zero. At this time, when the hydrogen concentration of the first furnace band 20 increases rapidly, the pressure fluctuation of the first furnace band increases, and the pressure P of the first nozzle P _{0_3} and the pressure P of the second nozzle with respect to the pressure fluctuation. _{0_2} ) is linked to change the sealing device is stable operation.

Figure 5 shows an embodiment for the stable operation of the atmospheric gas concentration by the pressure control method of the sealing device according to the present invention. It can be seen that the hydrogen concentration of the first furnace zone 20 is maintained for a long time at the level of 98 to 99% under the conditions as shown in FIG. 4.

<Description of the code>

1: steel sheet

2a, 2b: injection nozzle downstream of the sealing device

3a, 3b: upstream injection nozzle of the sealing device

4: jet flow injected from the nozzle

5: rolling roll

6: sealing device between rotary roll feed mechanism and sealing chamber

7: motor for rotating roll

8: rotary roll feed mechanism

9: blower

10: sealing chamber

20: the first furnace band

21: buffer space of the sealing device

22: second furnace band

Claims (5)

1. In the sealing device for blocking the atmosphere gas of the two furnace bands provided in the continuous furnace for performing a heat treatment process of the steel sheet between the first furnace band of the hydrogen atmosphere and the second furnace band of the nitrogen atmosphere,

   A pair of first nozzles for injecting the gas sucked from the first furnace band toward the steel sheets with the steel plates interposed therebetween;

   A pair of second nozzles for injecting the gas sucked from the second furnace band toward the steel sheets with the steel plates interposed therebetween;

    And a pair of rotary rolls disposed between the first nozzle and the second nozzle and rotating while being in contact with the steel sheet.
2. The method of claim 1,

   The distance between the first nozzle and the second nozzle and the steel sheet is maintained within a maximum of 50 mm, and the distance between the first nozzle and the second nozzle is at least smaller than the length along the direction of steel sheet advancement of the first nozzle and the second nozzle chamber. Atmospheric gas sealing apparatus of a continuous heat treatment furnace, characterized in that formed equal to or greater.
3. The method of claim 1,

   The rotation roll is the atmosphere gas sealing apparatus of the continuous heat treatment furnace, characterized in that the overall width including the bearing portion is smaller than the width of the sealing chamber, the distance between the rotating roll and the steel sheet is adjusted through a transfer mechanism connected to the bearing portion.
4. The method of claim 1,

   A pressure barrier is formed between the opposing first nozzle and the second nozzle, and the pressure in the buffer space between the pressure barriers is controlled to be greater than the pressure in the first furnace band and the pressure in the second furnace band. Pressure control method of the atmosphere gas sealing device in the heat treatment furnace.
5. The method of claim 1,

   The first furnace zone and the pressure of the first nozzle to the second pressure variation in the furnace zone (P _{0_3)} and a continuous, characterized in that the sealing device is operated stably by changing the pressure (P _{0_2)} interlocked in a second nozzle Pressure control method of the atmosphere gas sealing device in the heat treatment furnace.

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