JPH07316668A - Gas header and method for preventing deformation caused by temperature difference of roll using the same - Google Patents

Abstract

PURPOSE:To provide a method for preventing the deformation caused by temp. difference of a carrying roll in a metal strip continuous heat-treatment furnace having simple structure, good controllability and excellent maintainability. CONSTITUTION:In this gas header 3 for blowing a temp. regulating gas to the carrying roll 2 for metal strip, the lower surface faced to the carrying roll 2 is formed in reverse U-shape, and a gas blowing hole 6 having long slit- state in the width direction of the roll is provided in the vicinity of the position where the contact between the carrying roll 2 and the matal strip 1 is finished. Also, in this method, the deformation of the roll by the temp. difference is prevented by using this gas header.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preventing thermal deformation of a transporting roll caused by a temperature difference between the metal strip and the transporting roll in a vertical continuous heat treatment furnace for metal strips (steel strips, etc.). Regarding the device.

[0002]

2. Description of the Related Art In a vertical continuous heat treatment furnace in which a steel strip is conveyed while being stretched over a large number of conveyance rolls, in order to prevent the steel strip from meandering out of the center of the conveyance path line, the roll diameter at the center of the conveyance rolls is reduced. The carrier rolls with convex crowns larger than the both ends are used, and each of the carrier rolls has a meandering prevention function by the same principle as the meandering prevention in the belt wheel.

However, if the convex crown of the conveying roll is too large, the meandering correction force acting on the steel strip becomes excessive, compressive stress is generated in the widthwise direction of the steel strip, and the steel strip undergoes out-of-plane deformation. When the steel strip is wound around the transport roll with out-of-plane deformation, the steel strip buckles and wrinkles on the transport roll, detracting from its value as a product and when the buckling is severe. However, this may cause a large trouble such as the breakage of the steel strip and the shutdown of the equipment. Therefore, conventionally, operation has been performed with a minimum amount of the convex crown of the transport roll that does not meander, for example, the difference between the roll diameter at the center of the transport roll and the roll diameter at both ends is 0.2 mm to 2.0 mm. .

In the heating zone of the vertical continuous heat treatment furnace, in order to heat the steel strip to a predetermined temperature, for example, 650 ° C. to 850 ° C., a large number of heating devices such as radiant tubes are arranged and the atmospheric gas temperature is 600 ° C. A method of gradually heating the steel strip is used while the steel strip is hung between the conveying rolls arranged above and below in the furnace heated up to 900 ° C. and conveyed vertically. At this time, the difference between the temperature of the steel strip and the gas temperature in the furnace becomes very large on the inlet side of the heating furnace into which the steel strip at normal temperature is introduced. In the heating furnace, especially in the ceiling where heat easily accumulates, the carrier roll installed on the inlet side of the furnace is heated by the high-temperature atmosphere gas, whereas the steel strip that is not yet sufficiently heated. In the central part of the transfer roll, which is in contact with, is often cooled by the steel strip, and a large temperature difference of several hundreds of degrees Celsius often occurs in the transfer roll.

As described above, the conveying roll is provided with a convex crown for the purpose of preventing meandering, and the size of the convex crown is 0.5 mm to 2.0 mm for the purpose of preventing buckling of the steel strip.
It is made extremely small. Generally, the carrier roll is made of a high temperature resistant metal material and has a linear expansion coefficient of 1.
It is about 5 × 10 ⁻³ 1 / ° C. Moreover, since the diameter is about 1 m, the central portion of the transport roll is cooled by the steel strip.
Thermal expansion difference is 1.5 mm when a temperature difference of 00 ° C occurs
It also becomes a value that offsets the initial convex crown amount. In such a case, the meandering correction mechanism of the transport roll does not work, and it becomes difficult to stably transport along the pass line.

In order to deal with such a phenomenon, conventionally,
For example, a method of designing a convex crown by taking into account the temperature difference deformation of the transport roll has been attempted. But,
In a normal vertical continuous annealing furnace, the width of the steel strip conveyed is approximately 50.
Since it changes in the range of 0 mm to 1800 mm, the occurrence state of temperature difference deformation differs depending on the width of the steel strip, buckling does not occur for all widths of the steel strip, and it is not offset by temperature difference deformation. At present, it was not possible to design the shape.

In order to solve the above problems, the following methods have been disclosed. Japanese Unexamined Patent Publication No. 62-253734 discloses a method of spraying a cooling gas toward both ends of a steel strip transport roll to prevent temperature differential deformation of the transport roll.

Japanese Unexamined Patent Publication (Kokai) No. 62-256922 discloses a device in which a gas corresponding to the temperature of a steel strip is blown into a roll chamber that receives a transport roll.

In Japanese Patent Laid-Open No. 63-38532, a roll chamber for receiving a steel strip transport roll having a built-in thermometer is provided.
It is disclosed that a gas injection nozzle for heating and cooling corresponding to the temperature distribution of the transport roll is installed.

In Japanese Unexamined Patent Publication No. 2-277727, the emissivity of the wall surface of the roll chamber that receives the transfer roll is made of a material having an emissivity of 0.3 or less to reduce radiative heat transfer from the wall of the roll chamber to the transfer roll. A method is disclosed.

In Japanese Patent Laid-Open No. 4-293734, a part of a new atmosphere gas is blown into a box-shaped roll chamber that receives a plurality of transport rolls to lower the temperature of the roll chamber and deform the temperature difference of the transport rolls. A method of reducing is disclosed.

On the other hand, the colleagues of the present inventor have already proposed, in Japanese Utility Model Laid-Open No. 58-105464, a method for preventing temperature difference deformation by blowing cooling gas from the upper surface of the transport roll to the end of the transport roll. is doing. Figure 7
As shown in FIG. 2, the portion of the transport roll 2 to be cooled is covered with an inverted U-shaped cooling gas header 18 from above, and a large number of nozzles 19 arranged in the cooling gas header eject gas over almost half the circumference of the upper face of the transport roll. is there. Further, a movable radiant heat transfer suppressing plate 20 is installed for the purpose of reducing the amount of radiant heat transfer from the inside of the furnace to enhance the cooling effect.

[0013]

However, the above-mentioned prior art has the following problems. JP-A-62-25
According to the structure described in Japanese Patent No. 3734, since the roll chamber is not installed according to the structure diagram, the high temperature atmosphere gas in the furnace flows into the vicinity of the transport roll along with the steel strip, so that the temperature distribution of the transport roll is reduced. A large amount of gas needs to be blown to keep it constant, which causes an increase in operating costs. There was also the problem of poor responsiveness.

According to the technique disclosed in Japanese Patent Application Laid-Open No. 62-256922, since the roll chamber has a box shape according to its structure, the roll chamber volume is about twice as large as the roll volume, and an extra volume is required. The space becomes larger. Therefore, the high-temperature atmosphere gas in the furnace flows into the roll chamber as the steel strip is conveyed, and it becomes easier for the gas to stagnate in the corners of the roll chamber.Therefore, a large amount of gas must be blown in order to keep the temperature distribution of the conveyance roll constant. It was necessary, and there was the problem of causing an increase in operating costs. There was also the problem of poor responsiveness.

According to the method of the technique described in Japanese Patent Laid-Open No. 63-38532, the roll chamber has a box shape according to its structure, and since it has a structure for receiving a plurality of transport rolls, an extra space is required. Is large, the high-temperature furnace atmosphere gas flows into the roll chamber as the steel strip is transported, and tends to settle.Therefore, it is necessary to circulate a large amount of gas to control the temperature distribution of the transport rolls. There was a problem that led to higher costs. There was also the problem of poor responsiveness. Further, there is a problem that the equipment cost of the transport roll having the built-in thermometer is high.

Since the amount of radiant heat transfer in the technique described in Japanese Patent Application Laid-Open No. 2-277727 is proportional to the radiant area, the roll chamber shape is box-shaped and the heat transfer area is large.
You can't expect a big effect. Also, the amount of convective heat transfer that accounts for a large proportion of the heat transfer from the high temperature gas in the furnace to the transfer rolls,
Also, a large effect cannot be expected because it is not a technique for reducing the amount of radiant heat transfer from the high temperature gas in the furnace.

According to the method disclosed in Japanese Patent Laid-Open No. 4-293734, the roll chamber has a box shape.
In addition, since it has a structure that accepts multiple transfer rolls, it has a large extra space, and the high temperature atmosphere gas in the furnace flows into the roll chamber as the steel strips are transferred, making it easier to settle, thus controlling the temperature distribution of the transfer rolls. In order to do so, it is necessary to blow in an extra new atmosphere gas, which causes a problem of increasing operating costs. There was also the problem of poor responsiveness.

In the method disclosed in Japanese Utility Model Laid-Open No. 58-105464, since the cooling gas header and the radiation heat transfer suppressing plate are movable, the control range is wide, but the structure is complicated. . Further, when the transportation speed becomes high, there is a problem that the amount of high-temperature furnace gas flowing into the gap between the cooling gas header and the transportation roll increases, and the amount of gas required for cooling increases.

In view of the above-mentioned problems of the prior art, the object of the present invention is to solve the problems of the method for preventing the temperature difference deformation of the transport rolls, to provide a simple structure, good controllability, and maintenance, An object of the present invention is to provide a method for preventing temperature difference deformation of a transfer roll in a continuous annealing furnace heating furnace, which is excellent in maintainability.

[0020]

The above-mentioned problems can be solved by the following means. A gas header for blowing a temperature adjusting gas to a metal roll transport roll, the lower surface facing the transport roll has an inverted U-shape, and a slit shape long in the roll axial direction near the contact end position of the transport roll and the metal strip. A gas header having a gas outlet of. The gas header according to the item (1), characterized in that the surface for the transport roll is made of a material having a small surface emissivity. In a vertical continuous heat treatment furnace for metal strips, a shielding plate is arranged at the lower part of at least one of the transfer rolls installed in the upper part of the furnace to form a roll chamber, and above the transfer rolls, or. The metal strip carrier according to claim 1, wherein the gas header is arranged and the roll temperature adjusting gas is ejected from the gas outlet of the gas header toward the gap between the carrier roll and the lower surface of the inverted U-shaped gas header. Roll deformation prevention method. The temperature of the metal roll on the transport roll and the temperature of the metal strip on the transport roll are measured, so that the temperature difference between the temperature of the transport roll end and the metal strip on the transport roll falls within a predetermined range, the gas The method for preventing temperature difference deformation of a metal strip carrying roll according to (4), wherein the temperature and / or the flow rate of the gas ejected from the header is adjusted.

[0021]

The operation of the present invention will be described with reference to FIG. In FIG. 6, 1 is a metal strip, 2 is a transport roll, 3 is a gas header, 5 is a cooling gas supply pipe, and 6 is a slit-shaped opening. Here, the arrow attached to the metal strip 1 indicates the transport direction of the metal strip 1, and the arrows near the gas header 3 and the transport roll 2 indicate the flow direction of the cooling gas.

In the present invention, the cooling gas is the gas supply pipe 5
Is introduced into the gas header 3. The supplied gas is
The direction in which the gas in the header is replaced while flowing in the direction from the inside of the header to the direction of the arrow toward the end of the contact between the transport roll 2 and the metal strip 1 through the slit-shaped opening 6 and the direction in which the metal strip is transported. To be blown out.

Of the cooling gas blown from the slit-shaped opening 6, the cooling gas blown to the central portion of the transport roll around which the metal strip 1 is wound advances through the gap between the gas header 3 and the transport roll 2 to At the position, it collides with the high-temperature furnace gas flowing into the metal strip 1 together. As a result, the flow direction is changed, and the metal strip 1 flows in the space from both sides in the width direction, and flows into the furnace after the metal strip 1 is conveyed. On the other hand, the in-furnace gas flows from the inside of the furnace to the position inside the cooling gas header along with the metal strip 1 and is changed in direction by the cooling gas flowing opposite to the position of the width of the metal strip 1. It flows in the direction from the space on both sides of the direction, and recirculates into the furnace after the metal strip 1 is conveyed.

On the other hand, with respect to the cooling gas ejected at both ends of the transport roll, which is not wrapped with the metal strip 1, advances through the gap between the gas header 3 and the transport roll 2, and at a position of Collision-mix with the gas in the furnace. After that, the metal strip 1 flows in the direction from the space on both sides in the width direction, and then flows into the furnace.

Since the gas header 3 is structured to generate such a flow, the high-temperature in-furnace gas flowing along with the metal strip collides with the cooling gas at the position, so that the inflow amount is suppressed. And, compared to the conventional box-type roll chamber, the space for flowing the cooling gas is extremely small,
With a small cooling gas flow rate, it is possible to effectively control the temperature by the empirically obtained temperature and flow rate of the cooling gas that suppresses the temperature difference deformation of the transfer roll. As described above, the present invention has been made by paying attention to the gas flow and the cooling effect in the vicinity of the roll, which has not been sufficiently studied in the prior art.

Here, the surface of the inverted U-shaped gas blowout header with respect to the transport roll is made of a material having a small surface emissivity, so that the amount of radiant heat transfer between the metal strip transport roll and the cooling gas header is suppressed, The cooling controllability by convective heat transfer in the cooling gas can be enhanced to prevent temperature difference deformation.

Further, in the above invention, the flow rate of the gas ejected from the inverted U-shaped gas header is such that the indicated value of the thermometer of the transfer roll installed in the gap between the inverted U-shaped gas header and the transfer roll is By adjusting the flow rate so as to match the temperature of the metal strip on the transport roll within a predetermined range, it is possible to enhance temperature controllability and prevent temperature difference deformation.
That is, in FIG. 6, the flow rate or temperature setting of the gas ejected from the inverted U-shaped gas header is set to the indicated value of the thermometer of the transport roll installed in the gap between the inverted U-shaped gas header and the transport roll. The temperature of the gas around the transport roll can be brought close to the temperature of the metal strip if it is based on the deviation given separately from the temperature of the metal strip on the transport roll. Further, since the cooling gas is supplied after passing through the inside of the gas header, the surface of the gas header that faces the transfer roll is also close to the temperature of the cooling gas, and both the convective heat transfer and the radiant heat transfer are performed. Also, since the temperature deviation of the transfer roll acts in the direction of approaching the metal strip temperature, if the cooling gas flow rate is adjusted so that the target temperature deviation is within the predetermined range, the temperature of the transfer roll can be controlled with good temperature controllability. The deviation can be suppressed.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The construction of the present invention will be described below in detail based on the specific embodiments shown in the accompanying drawings. FIG. 1 is a view showing an embodiment in which the present invention is experimentally applied to a steel strip conveying roll of a heating furnace of a continuous annealing line for steel strips. In the figure below,
The same parts as those in FIG. 6 are designated by the same reference numerals and the description thereof will be omitted.
In FIG. 1, 4 is a cooling gas flow control valve, 7 is a radiation suppressing plate, 8 is a heat insulating material, 9 is a heating furnace side plate, 10 is a heating furnace top plate, 11 is a thermometer, and 12 is a cooling gas flow rate control device. , 31
Is a side plate of the gas header. In FIG. 1, the transport direction of the metal strip (steel strip) 1 is as shown by the arrow in the figure. The cooling gas supply pipe 5 is inserted into the gas header 3, and is branched at the downstream side of the cooling gas flow rate control valve 4 and installed in two in the furnace width direction. Here, the cooling gas is a non-oxidizing gas that has the same composition as the atmosphere gas in the furnace, and is supplied at a temperature not controlled in the figure below the temperature of the steel strip. The cooling gas flow rate control device 12 controls the opening degree of the cooling flow rate control valve 4 so that the deviation between the steel strip temperature signal (a) and the temperature measured by the thermometer 11, which is separately provided, becomes small. . The slit-shaped opening 6 has a width substantially equal to that of the inverted U-shaped gas header 3.

FIG. 1 (I) is a view showing a cross section perpendicular to the axis of the transport roll. Gas header 3 and carrier roll 2
The gap S between and is made extremely close to 5 cm because the shape of the steel strip follows the shape of the roll by being wound around the conveying roll. Here, the surface of the gas header 3 facing the transport roll 2 is made of a stainless steel plate. Further, the slit-shaped opening 6 for blowing the cooling gas is arranged so that the blowing direction of the gas is the direction opposite to the conveying direction of the steel strip. With such a structure, the gas supplied to the inverted U-shaped gas outlet header is on the opposite side of the gas outlet of the outlet header with respect to the transport roll and at both widthwise end portions of the steel strip. By supplying gas from a pipe deeply inserted in the vicinity, the gas blowout header has a simple structure, while suppressing the stagnation of the flow in the header, the gas velocity blown out from the slit causes a large jet at both ends of the header. It has the effect of generating a flow rate distribution, and effectively prevents the temperature difference deformation of the roll end that requires cooling.

According to the present invention, since the space through which the cooling gas flows is extremely smaller than that of the conventional box-shaped roll chamber, the cooling gas obtained empirically for suppressing the temperature difference deformation of the transfer roll with a small cooling gas flow rate. The temperature can be effectively controlled by the temperature and the flow rate. FIG. 7 is a diagram showing a conventional temperature difference generation preventing method, but when the cooling gas is dispersed and blown in the circumferential direction of the transport roll as in the prior art, as shown in FIG.
The cooling gas ejected from the vicinity of both ends of the header separates from the transport roll without sufficiently cooling the transport roll, and thus there is a drawback that the cooling efficiency is poor.

FIG. 1 (II) is a view showing a cross section in the direction of the arrow in FIG. 1 (I). In FIG. 1 (II), W is a symbol indicating the approximate width of the slit-shaped opening for blowing the cooling gas. The thermometer 11 is installed in the gap between the transport roll 2 and the gas header 3 and outside the widthwise end of the steel strip. Since the installation position of the thermometer is near and outside the steel strip end position at the maximum width of the steel strip to be transported, the measured temperature is mainly measured by the radiation transfer from the surface of the transport roll to be temperature controlled. It depends on heat and convective heat transfer from the cooling gas. Therefore, the temperature measurement error due to the influence of heat radiation from the steel strip is reduced. Further, the temperature sensing section is arranged in parallel with the axial direction of the transport roll to reduce measurement error due to heat conduction through the thermometer. In this way, temperature controllability is enhanced to prevent temperature difference deformation.

In this embodiment, the cooling gas flow rate control device 12 controls the cooling gas flow rate control valve 4 so that the deviation between the steel strip temperature signal (a) and the temperature measured by the thermometer 11 is reduced. The opening of is controlled. That is, the temperature of the gas ejected from the inverted U-shaped gas header 3 is made lower than the temperature of the steel strip 1 on the transport roll by a heat exchanger not shown in the figure. After that, the flow rate of the gas to be jetted is set by the indication value of the thermometer 11 installed in the gap between the inverted U-shaped gas header 3 and the transport roll 2, and the steel strip 1 on the transport roll which is given separately. Based on the deviation from the temperature of
Since the temperature of the steel strip 1 is brought close to and the cooling gas is supplied after passing through the inside of the cooling gas header, the surface of the cooling gas header facing the transfer roll is also close to the temperature of the cooling gas, and the convection conduction occurs. For both heat and radiant heat transfer, the temperature deviation of the transport roll 2 is made to act in the direction of approaching the steel strip temperature, and the target temperature deviation is ± 20 ° C. before and after the connection of the steel strip 1 passes. Within, within ± 1,
The cooling gas flow rate is adjusted to be within 0 ° C.

As described above, the conveying roll is provided with a convex crown for the purpose of preventing meandering, and the size of the convex crown is 0.5 mm to 2.0 mm for the purpose of preventing buckling of the steel strip.
It is made extremely small. Generally, the carrier roll is made of a high temperature resistant metal material and has a coefficient of thermal expansion of 1.
It is about 5 × 10 ⁻³ 1 / ° C. Moreover, since the diameter is about 1 m, the central portion of the transport roll is cooled by the steel strip.
When the temperature difference of 0 ° C. occurs, the difference in thermal expansion is about 0.3 mm, which is smaller than the initial convex crown amount, and the meandering correction mechanism of the transport roll can be maintained.

Further, the widthwise position of the steel strip of the thermometer installed in the gap between the inverted U-shaped gas header and the transport roll is determined by the position of the steel strip end position at the maximum width of the transported steel strip. By being near and outside, it is possible to reduce temperature measurement error due to the influence of heat radiation from the steel strip, improve temperature controllability, and prevent temperature difference deformation. That is, since the measured temperature is mainly determined by the radiant heat transfer from the surface of the transfer roll to be temperature-controlled and the convective heat transfer from the cooling gas, it is possible to reduce the temperature measurement error due to the effect of thermal radiation from the steel strip. Therefore, the temperature controllability can be enhanced and the temperature difference deformation can be prevented.

Further, a pipe in which the gas supplied to the inverted U-shaped gas header is deeply inserted on the side opposite to the gas ejection port with respect to the conveying roll and in the vicinity of both widthwise ends of the steel strip. Although it is a gas header with a simple structure, it suppresses the stagnation of the flow in the header, and the gas velocity blowing out from the slit causes a large jet flow distribution at both ends of the header to cool the header. Therefore, it is possible to effectively prevent the temperature difference deformation of the end portion of the roll, which is required.

The surface of the inverted U-shaped gas header with respect to the transport roll is made of a material having a small surface emissivity, so that the amount of radiant heat transfer between the steel strip transport roll and the cooling gas header is suppressed to cool the steel strip. Cooling controllability by convective heat transfer with gas can be improved to prevent temperature difference deformation.

Further, in the portion where the temperature of the steel strip is several hundred degrees Celsius, the temperature of the transport roll and the cooling gas header itself are also several hundred degrees Celsius, and the amount of heat radiation from the upper surface of the cooling gas header is increased. By covering the upper surface of the V-shaped gas header with a heat insulating material and suppressing the heat loss to the outside of the furnace, it is possible to prevent temperature difference deformation and contribute to energy saving.

Further, the inverted U-shaped gas header can be lifted to have a structure that can be detached from the furnace, so that maintenance and maintainability can be improved and application to an existing furnace can be facilitated. Conventionally, in a continuous annealing furnace, a removable lid is generally attached to the ceiling of the furnace in order to maintain and inspect the conveyor rolls in the furnace. The present invention is, so to speak, a structure in which a cooling gas header is simply attached to such a lid, and can be easily attached to an existing furnace. FIG. 2 is a diagram of an embodiment showing a method of detaching the temperature control device for a transport roll according to the present invention from a heating furnace. In FIG. 2, 13 is a crane hook. In this embodiment, the inverted U-shaped gas header 3, the cooling gas flow rate control valve 4, the cooling gas supply pipe 5, the heat insulating material 8 and the thermometer 11 are integrally lifted by a crane to be detached from the heating furnace. .

Further, a plurality of the inverted U-shaped gas headers are connected to each other, and they are lifted as a unit so that they can be attached to and detached from the furnace, and each gas header is provided with a gas supply pipe and a thermometer. If the temperature difference deformation prevention device for steel strip conveyor rolls is characterized by independent flow rate control, maintenance and maintainability will be improved, and application to existing furnaces will be easier and equipment costs will be reduced. . 3 and 4 show an embodiment in which a plurality of temperature control devices for the transport rolls according to the present invention are installed. In the following figures, the same parts as those in FIG. In the case of FIG. 3 and FIG. 4, the flow rate control valve 4 and the thermometer 11 are installed in each cooling gas header to enable temperature control for each header. Since a plurality of cooling headers can be attached to and detached from the furnace at the same time, the facility cost can be saved, maintenance and maintainability can be improved, and application to an existing furnace can be facilitated. Conventionally, in a continuous annealing furnace, a removable lid is generally attached to the ceiling of the furnace in order to maintain and inspect the conveyor rolls in the furnace. The present invention is, so to speak, a structure in which a cooling gas header is simply attached to such a lid.

Further, the gas supplied to the inverted U-shaped gas header is extracted from the inside of the furnace and a mixed gas of a gas whose temperature is adjusted by a heat exchanger and a non-oxidizing gas newly supplied from outside the furnace. By this, not only the temperature controllability is enhanced, but also the increment of the non-oxidizing gas consumption amount required by the present invention can be eliminated. Further, the inverted U-shaped gas header has a difference between the furnace gas temperature and the steel strip temperature of 50.
By installing only at a position where the temperature difference deformation of the steel strip transport roll is likely to occur at a temperature of ℃ or more, it is possible to suppress an increase in equipment cost. FIG. 5 is a view showing a case where such a roll temperature difference generation preventing device according to the present invention is installed in the preceding stage of the heating zone of a continuous annealing furnace, and is a view shown together with a cooling gas supply system. In FIG. 5, 14a to 14c are extraction control valves, 15 is a heat exchanger, 16 is a blower, and 17 is a supply control valve. Four inverted U-shaped gas headers 3 were installed at positions where the difference between the steel strip and the furnace temperature in the front stage of the heating furnace of the continuous annealing furnace was large, and the gas supplied to the gas header 3 was extracted from the inside of the furnace by the extraction control valve 14a to.
14c is extracted and the temperature is adjusted by the heat exchanger 15,
The non-oxidizing gas supplied through the cooling gas flow rate control valves 4a to 4e by forming a mixed gas of the gas pressurized by the blower 16 and the non-oxidizing gas newly supplied from the outside of the furnace through the air supply regulating valve 17 The flow rate of the non-oxidizing gas required by the present invention is eliminated while ensuring the flow rate of the non-oxidizing gas. In addition, the conveying direction of the steel strip is from the direction.

FIG. 8 is a diagram showing a change in the number of times of monthly throttling in the furnace before and after mounting the apparatus according to the present invention.
It can be seen from FIG. 8 that the number of times of occurrence of throttling after mounting the device according to the present invention is drastically reduced.

The present invention can be applied to various metal strips other than steel strip. It is also applicable when the inside of the transfer roll is cooled or heated. Further, it can be applied to the case where a roll material having a small linear expansion coefficient is selected for the transport roll.

[0043]

According to the present invention, the temperature difference deformation of the roll is reduced, the proper convex crown of the transport roll can be maintained, the trouble such as the breakage of the metal strip in the furnace is reduced, and the product quality is improved. It also contributes to improved productivity.

[Brief description of drawings]

FIG. 1 is a side sectional view showing an outline of an embodiment of the invention.

FIG. 2 is a diagram showing a method for attaching and detaching a roll temperature difference occurrence preventing device according to the present invention.

FIG. 3 is a diagram showing a case where two roll temperature difference prevention devices according to the present invention are connected.

FIG. 4 is a view showing a case where three roll temperature difference occurrence preventing devices according to the present invention are connected.

FIG. 5 is a view showing a case where a roll temperature difference generation preventing device according to the present invention is installed in a preceding stage of a heating zone of a continuous annealing furnace, and is a view shown together with a cooling gas supply system.

FIG. 6 is a diagram showing an operation of the roll temperature difference occurrence preventing method according to the present invention.

FIG. 7 is a view showing a conventional temperature difference prevention device.

FIG. 8 is a diagram showing an effect of the present invention.

[Explanation of symbols]

 1 Metal Band 2 Conveyor Roll 3 Inverted U-shaped Gas Header 6 Slit-shaped Opening for Cooling Gas Blowing 11 Thermometer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kuniaki Okada 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Steel Pipe Co., Ltd.

Claims (4)

[Claims] 1. A gas header for blowing a temperature adjusting gas to a metal roll carrying roll, wherein a lower surface facing the carrying roll has an inverted U shape, and a roll shaft is provided near a contact end position of the carrying roll and the metal band. A gas header having a slit-shaped gas outlet that is long in the direction. 2. The surface for the transport roll is made of a material having a low surface emissivity.
Gas header described in. 3. In a vertical continuous heat treatment furnace for metal strips, a shielding plate is arranged at the bottom of at least one of the transfer rolls installed in the upper part of the furnace to form a roll chamber, and
The gas header according to claim 1 or 2 is arranged on the upper side of the transport roll, and is directed toward the gap between the transport roll and the lower surface of the inverted U-shaped gas header from the gas outlet of the gas header. A method for preventing deformation of a metal band transport roll, which comprises ejecting a roll temperature adjusting gas. 4. The temperature of the end of the transport roll and the temperature of the metal strip on the transport roll are measured, and the difference between the temperature of the end of the transport roll and the temperature of the metal strip on the transport roll is within a predetermined range. The temperature difference deformation prevention method for a metal strip carrying roll according to claim 3, wherein the temperature and / or the flow rate of the gas ejected from the gas header are adjusted so as to enter.