Continuous heat treatment furnace

Abstract

To enable a metal strip to be stably run by a support roller in a continuous heat treatment furnace in which a long metal strip is run in a furnace and fuel is burned in the furnace by a combustion device to perform heat treatment of the metal strip.SOLUTION: In a continuous heat treatment furnace in which a long metal strip S is run in the furnace 10 and the metal strip is heat-treated by burning fuel in the furnace by a combustion device 20, a support roller 22 for stabilizing the running of the metal strip is provided at a position upstream of the gas flow in the furnace relative to the combustion device. An inert gas supply device 25 for supplying an inert gas N2 to the support roller is also provided.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a continuous heat treatment furnace in which a long metal strip is made to travel within the furnace and a fuel is burned in the furnace by a combustion device to heat the metal strip. In particular, the present invention is characterized in that, when fuel is burned in the furnace by a combustion device and a long metal strip is made to travel within the furnace and heat treated, the metal strip can be stably traveled without being damaged by support rollers. [Background technology]

[0002] Conventionally, as shown in Patent Document 1 and the like, there has been known a continuous heat treatment furnace in which a metal strip made of a long steel plate or the like is transported in a vertically installed furnace while a combustion device is used to combust fuel in the furnace to perform heat treatment.

[0003] Furthermore, in a continuous heat treatment furnace, as shown in Patent Document 2, there is known a furnace in which support rollers are provided on both sides of the running metal strip to guide the metal strip and to make contact with the metal strip so as to stably run the metal strip within the furnace.

[0004] As the support roller, as shown in Patent Document 2, a support roller having a carbon sleeve made of graphite or the like provided on the outer circumferential surface, or a metal support roller made of stainless steel or the like is used.

[0005] However, in a continuous heat treatment furnace in which fuel is burned inside the furnace by a combustion device as described above, when metal support rollers are used as the support rollers, there is a problem in that the surface of the metal support roller is oxidized by oxygen remaining in the combustion exhaust gas from the fuel combustion, causing oxides to accumulate, and the oxides accumulated on the surface of the support roller can damage the surface of the metal strip being transported.

[0006] Furthermore, in a continuous heat treatment furnace in which fuel is burned by a combustion device as described above, if support rollers having carbon sleeves on their outer circumferential surfaces are used as the support rollers, as shown in Patent Documents 3 and 4, the surface will not be oxidized and oxides will not accumulate; however, when the temperature inside the furnace becomes high, the carbon in the carbon sleeve reacts with the oxygen contained in the combustion exhaust gas from burning the fuel and is sublimated as CO or CO2, causing the diameter of the support roller to become smaller, which causes the metal strip to be unable to be guided properly. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2010-202959 A [Patent Document 2] Japanese Patent Application Publication No. 8-269579 [Patent Document 3] Japanese Patent Application Publication No. 6-322436 [Patent Document 3] Japanese Patent Application Publication No. 7-113115 DISCLOSURE OF THEINVENTION [Problem to be solved by the invention]

[0008] The present invention aims to solve the above-mentioned problems in a continuous heat treatment furnace in which a long metal strip is run inside the furnace and fuel is burned inside the furnace by a combustion device to heat the metal strip.

[0009] That is, in the continuous heat treatment furnace of the present invention, when a long metal strip is heat-treated in the furnace, and support rollers are provided to allow the metal strip to run stably in the furnace, the surface of the metallic support roller is oxidized by oxygen contained in the combustion exhaust gas obtained by burning fuel, causing oxides to accumulate, and the surface of the metal strip being transported is prevented from being damaged by the accumulated oxides, and the carbon on the support roller provided with a carbon sleeve on its outer circumferential surface reacts with oxygen contained in the combustion exhaust gas obtained by burning fuel to become CO or CO2 and be sublimated, causing the diameter of the support roller to become smaller, and causing the metal strip to be unable to be guided properly. [Means for solving the problem]

[0010] In order to solve the above-mentioned problems, in the continuous heat treatment furnace of the present invention, a long metal strip is run inside the furnace and the metal strip is heat-treated in the flow of gas inside the furnace that flows toward an exhaust pipe from which fuel is burned inside the furnace using a combustion device and the gas is discharged.Support rollers for stabilizing the running of the metal strip are provided upstream of the combustion device in the direction of gas flow inside the furnace, and an inert gas supply device is provided for supplying inert gas to the support rollers.

[0011] Furthermore, in the case of the continuous heat treatment furnace of the present invention, when support rollers for stabilizing the running of the metal strip are provided at a position upstream of the combustion device in the gas flow direction inside the furnace, supplying inert gas from an inert gas supply device to the support rollers prevents the support rollers from coming into contact with oxygen remaining in the combustion exhaust gas produced by burning fuel.

[0012] Here, the continuous heat treatment furnace according to the present invention may be a vertical type in which the metal strip runs in a furnace arranged in a vertical direction, or a horizontal type in which the metal strip runs in a furnace arranged in a horizontal direction. In the case of a vertical type furnace in which the metal strip runs in a furnace arranged in a vertical direction, the metal strip may run from top to bottom in the vertical furnace, or the metal strip may run from bottom to top.

[0013] In addition, in the continuous heat treatment furnace according to the present invention, the support rollers can be either support rollers provided with a carbon sleeve on their outer circumferential surface or support rollers made of metal, since this prevents the generation of oxides due to oxygen and the sublimation of carbon.

[0014] In addition, in the continuous heat treatment furnace according to the present invention, when the inert gas is supplied from the inert gas supply device to the support rollers as described above, the inert gas can be supplied from the inert gas supply device to a position upstream of the support rollers in the gas flow direction in the furnace. In this way, the support rollers are surrounded by inert gas upstream of the combustion device in the gas flow direction, so that the combustion exhaust gas from burning fuel does not come into contact with the support rollers, and contact with oxygen remaining in the combustion exhaust gas is reliably suppressed.

[0015] In addition, in the continuous heat treatment furnace according to the present invention, an oxygen concentration detector for detecting the oxygen concentration in the furnace is provided at a position downstream of the support roller in the direction of gas flow in the furnace, and the oxygen concentration in the furnace detected by the oxygen concentration detector is output to a control device, and the control device controls the supply of the inert gas supplied into the furnace by the inert gas supply device. In this way, the amount of inert gas supplied into the furnace from the inert gas supply device can be adjusted according to the oxygen concentration detected by the oxygen concentration detector, and the amount of inert gas supplied into the furnace by the inert gas supply device can be reduced to reduce running costs when the detected oxygen concentration is low based on the oxygen concentration at which oxides are generated on the surface of the support roller or the carbon roller is sublimated, and the amount of inert gas supplied into the furnace can be increased when the oxygen concentration is high, thereby reliably preventing the generation of oxides on the support roller or the sublimation of the carbon roller.

[0016] In addition, when the entire furnace is filled with inert gas and then the metal strip is heat-treated using the continuous heat treatment furnace, the supply of inert gas from the inert gas supply device can be stopped until the oxygen concentration detected by the oxygen concentration detection device reaches a concentration that adversely affects the support rollers. Effect of the Invention

[0017] In the continuous heat treatment furnace of the present invention, a metal strip is made to travel within the furnace and is heat-treated in the flow of gas within the furnace that flows toward an exhaust pipe that burns fuel in the furnace using a combustion device and discharges the gas. In this case, if support rollers for stabilizing the travel of the metal strip are provided upstream of the combustion device in the direction of gas flow within the furnace, supplying an inert gas from an inert gas supply device to the support rollers prevents the support rollers from coming into contact with the oxygen contained in the combustion exhaust gas produced by burning fuel.

[0018] As a result, in the continuous heat treatment furnace of the present invention, when support rollers having carbon sleeves on their outer peripheral surfaces are used as support rollers, the carbon in the carbon sleeve does not react with oxygen and sublimate into CO or CO2, which would cause the diameter of the support rollers to become smaller, and the metal strip can be guided stably. Furthermore, when metal support rollers are used as support rollers, the surface of the metal support rollers is not oxidized by oxygen and oxides do not accumulate on the surface of the metal support rollers, preventing the surface of the transported metal strip from being damaged. [Brief description of the drawings]

[0019] [Figure 1] FIG. 2 is a schematic explanatory diagram showing a state in which a metal strip is heat-treated by traveling from top to bottom in a vertically installed furnace in a continuous heat treatment furnace according to an embodiment of the present invention. [Diagram 2] In the continuous heat treatment furnace according to the embodiment described above, fuel is burned in the furnace by a combustion device and metal strips are heat-treated in the gas flow inside the furnace that flows toward an exhaust pipe. An inert gas supply device supplies inert gas to a position upstream of the support rollers in the gas flow direction inside the furnace, and an oxygen concentration detection device detects the oxygen concentration inside the furnace downstream of the support rollers in the gas flow direction inside the furnace. This is an enlarged cross-sectional explanatory diagram showing a state in which the inert gas supplied from the inert gas supply device is controlled by a control device based on the oxygen concentration detected by the oxygen concentration detection device. [Diagram 3] FIG. 2 is a schematic plan view showing an example of a support roller having a carbon sleeve provided on its outer circumferential surface in the continuous heat treatment furnace according to the embodiment. BEST MODE FOR CARRYING OUT THEINVENTION

[0020] The continuous heat treatment furnace according to the embodiment of the present invention will be specifically described below with reference to the accompanying drawings. Note that the continuous heat treatment furnace according to the present invention is not limited to the embodiment shown below, and can be appropriately modified and implemented within the scope of the invention.

[0021] In the continuous heat treatment furnace of this embodiment, as shown in Figures 1 and 2, a long metal strip S such as a stainless steel band is transported by being wound up by a winding device (not shown) provided downstream of the furnace, turned downward by an introduction roller 1, and introduced into a vertical furnace 10 installed vertically while preventing the atmosphere in the furnace 10 from escaping and the outside air from entering by a seal roller 14. Fuel is burned in the furnace 10 by each combustion device 20 provided in a heating section 11 at the top of the furnace 10, thereby heating the metal strip S introduced into the furnace 10. Here, the combustion exhaust gas generated in each combustion device 20 is exhausted from an exhaust pipe 13 at the top, and a gas flow is generated in the furnace 10 toward the exhaust pipe 13.

[0022] Then, while the running of the heated metal strip S is stabilized by support rollers 22 provided downstream of the combustion device 20 in the running direction of the metal strip S, the heated metal strip S is guided from the heating section 11 to the cooling section 12 at the bottom of the furnace 10 to be cooled, and the direction of the metal strip S is changed upward by the delivery rollers 2 and sent out from the furnace 10. At this time, the metal strip S is guided into a water sealing device 3 to prevent the atmosphere in the furnace 10 from leaking out and the outside air from entering.

[0023] In the continuous heat treatment furnace of this embodiment, the support rollers 22 are provided with carbon sleeves 22a on their outer circumferential surfaces, as shown in FIG.

[0024] In the continuous heat treatment furnace of this embodiment, when fuel is burned in the furnace 10 by each combustion device 20 as described above, when the carbon in the carbon sleeve 22a provided on the outer circumferential surface of the support roller 22 comes into contact with oxygen contained in the combustion exhaust gas obtained by burning the fuel at a high temperature, the carbon reacts with the oxygen to become CO or CO2, which is sublimated, causing a problem that the diameter of the support roller 22 becomes smaller.

[0025] Here, in the continuous heat treatment furnace of this embodiment, the oxygen concentration in the furnace 10 at a position downstream of the support roller 22 in the gas flow direction in the furnace 10 (above the support roller 22 in the figure) is detected by the oxygen concentration detector 23, and the oxygen concentration in the furnace 10 detected by the oxygen concentration detector 23 is output to the control device 24, and the control device 24 controls the amount of inert gas N2 supplied from the inert gas supply device 25 to the furnace 10 at a position upstream of the support roller 22 in the gas flow direction in the furnace 10 (below the support roller 22 in the figure) based on the oxygen concentration detected by the oxygen concentration detector 23. Note that the inert gas may be other gases such as Ar (argon) other than N2 (nitrogen).

[0026] In the continuous heat treatment furnace of this embodiment, when the oxygen concentration detected by the oxygen concentration detector 23 is low, the control device 24 reduces the amount of inert gas N2 supplied from the inert gas supply device 25 to a position upstream of the support rollers 22 in the gas flow direction in the furnace 10 (below the support rollers 22 in the figure) to reduce running costs, while when the oxygen concentration detected by the oxygen concentration detector 23 is high, the control device 24 increases the amount of inert gas N2 supplied from the inert gas supply device 25 to a position upstream of the support rollers 22 in the gas flow direction in the furnace 10 (below the support rollers 22 in the figure) to prevent the carbon in the carbon sleeve 22a provided on the outer surface of the support roller 22 from reacting with the oxygen contained in the combustion exhaust gas produced by burning fuel and becoming CO or CO2 and being sublimated. For example, when supplying inert gas N2 from the inert gas supply device 25 into the furnace 10 as described above, the inert gas N2 is supplied from the inert gas supply device 25 into the furnace 10 so that the oxygen concentration in the furnace 10 in the vicinity of the support roller 22 is less than the concentration at which carbon does not sublimate (approximately 500 ppm).

[0027] In this manner, in the continuous heat treatment furnace of this embodiment, the amount of inert gas N2 supplied from the inert gas supply device 25 to a position upstream of the support rollers 22 in the gas flow direction inside the furnace 10 (below the support rollers 22 in the figure) is controlled by the control device 24. Therefore, the carbon in the carbon sleeve 22a provided on the outer peripheral surface of the support roller 22 reacts with the oxygen contained in the combustion exhaust gas produced by burning fuel at high temperatures, and is sublimated into CO or CO2, which prevents the diameter of the support roller 22 from becoming smaller, and the metal strip S can be run stably inside the furnace 10.

[0028] As described above, the inert gas N2 supplied from the inert gas supply device 25 into the furnace 10 at a position upstream of the support rollers 22 in the gas flow direction inside the furnace 10 (below the support rollers 22 in the figure) is guided to the top of the furnace 10 together with the combustion exhaust gas remaining after the fuel is combusted by each combustion device 20 inside the furnace 10 as a gas flow inside the furnace 10, and is exhausted from the exhaust pipe 13.

[0029] Here, in the continuous heat treatment furnace of this embodiment, the gas flow inside the vertical furnace 10 is considered to be upward, and the arrangement of the equipment is illustrated as being in the order of exhaust pipe 13, combustion device 20, oxygen concentration detection device 23, support roller 22, and inert gas supply device 25 from top to bottom. However, this can also be adopted in cases where the gas flow inside the vertical furnace 10 is downward, such as when the exhaust pipe 13 is located at the bottom of the furnace 10.

[0030] In that case, although not shown, the arrangement of the equipment may be, from the top, in the order of the inert gas supply device 25, the support rollers 22, the oxygen concentration detector 23, the combustion device 20, and the exhaust pipe 13.

[0031] Also, in the case of a horizontal furnace 10 in which the metal strip S is transported horizontally, although not shown, the arrangement of the equipment may be along the direction of gas flow within the furnace 10 in the following order: inert gas supply device 25, support rollers 22, oxygen concentration detection device 23, combustion device 20, and exhaust pipe 13.

[0032] In addition, in the continuous heat treatment furnace of this embodiment, when operations start, inert gas N2 is supplied into the furnace 10 from the inert gas supply device 25, etc., to fill the entire furnace 10 with inert gas N2, and then the metal strip S is introduced into the vertical furnace 10 as described above, and fuel is burned in the furnace 10 by each combustion device 20 provided in the heating section 11 at the top of the furnace 10, so that the metal strip S introduced into the furnace 10 can be heat-treated as described above.

[0033] In this case, the entire support roller 22 is completely surrounded by the inert gas N2, so there is no risk of sublimation. The concentration of the inert gas N2 decreases as the combustion exhaust gas is discharged from the exhaust pipe 13, but when the oxygen concentration detected by the oxygen concentration detector 23 reaches a concentration that adversely affects the carbon in the carbon sleeve 22a provided on the outer circumferential surface of the support roller 22, the inert gas supply device 25 may start supplying the inert gas N2 into the furnace 10.

[0034] In addition, in the continuous heat treatment furnace of this embodiment, the support rollers 22 are provided with carbon sleeves 22a on their outer circumferential surfaces, but the support rollers 22 are not limited to this, and metal rollers can also be used as the support rollers 22.

[0035] Furthermore, even when a metallic roller is used as the support roller 22, by controlling the amount of inert gas N2 supplied from the inert gas supply device 25 to a position upstream of the metallic support roller 22 in the gas flow direction within the furnace 10 as described above, the surface of the metallic support roller 22 is not oxidized by oxygen and oxides are not deposited on the surface of the metallic support roller 22, thereby preventing the surface of the transported metal strip S from being damaged by the deposited oxides.

[0036] In addition, in the continuous heat treatment furnace in this embodiment, the metal strip S is run from top to bottom within the vertical furnace 10 installed vertically, but although not shown, the metal strip S can also be run from bottom to top within the vertical furnace 10 to be heat treated. [Explanation of symbols]

[0037] 1: Introduction roller 2: Roller for extraction 3: Water sealing device 10: Furnace 11: Heating section 12: Cooling section 13: Exhaust pipe 14: Seal roller 20: Combustion equipment 22: Support roller 22a: Carbon sleeve 23: Oxygen concentration detector 24: Control device 25: Inert gas supply device N2: Inert gas S: Metal strip

Claims

1. A continuous heat treatment furnace in which a long metal strip is made to run within the furnace and the metal strip is heat-treated in the flow of gas within the furnace that flows toward an exhaust pipe that burns fuel within the furnace using a combustion device and discharges the gas, characterized in that the continuous heat treatment furnace is provided with support rollers that stabilize the running of the metal strip, and an inert gas supply device that supplies inert gas to the support rollers, located upstream of the combustion device in the direction of gas flow within the furnace.

2. 2. The continuous heat treatment furnace according to claim 1, which is a vertical type furnace in which the metal strip is transported in a vertical direction within the furnace.

3. 2. The continuous heat treatment furnace according to claim 1, wherein the support rollers are provided with carbon sleeves on their outer circumferential surfaces.

4. 2. The continuous heat treatment furnace according to claim 1, wherein the inert gas supply device supplies an inert gas to a position upstream of the support rollers in the gas flow direction within the furnace.

5. 5. The continuous heat treatment furnace according to claim 1, further comprising an oxygen concentration detector for detecting the oxygen concentration in the furnace at a position downstream of the support rollers in the gas flow direction in the furnace, the oxygen concentration in the furnace detected by the oxygen concentration detector being output to a control device, and the control device controlling the supply of inert gas supplied into the furnace by the inert gas supply device.

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