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 run in a furnace and fuel is burned in the furnace by a combustion device to heat-treat the metal strip. In particular, when fuel is burned in the furnace by a combustion device and a long metal strip is run in the furnace for heat treatment, the metal strip can be stably run without being damaged by a support roller, which is a feature of the present invention.

Background Art

[0002] Conventionally, as shown in Patent Document 1 and the like, there is known a continuous heat treatment furnace in which a metal strip made of a long steel plate or the like is run in a furnace provided vertically, and fuel is burned in the furnace by a combustion device for heat treatment.

[0003] In addition, in a continuous heat treatment furnace, as shown in Patent Document 2, support rollers for guiding the metal strip are provided so as to contact both sides of the running metal strip so that the metal strip can be stably run in the furnace.

[0004] As the support roller, as shown in Patent Document 2, a support roller provided with a carbon sleeve such as graphite on the outer peripheral 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 in the furnace by a combustion device as described above, when a metal support roller is used as the support roller, the surface of the metal support roller is oxidized by oxygen remaining in the combustion exhaust gas after burning the fuel, and oxides are deposited. There was a problem that the surface of the metal strip conveyed by the oxides deposited on the surface of the support roller was damaged.

[0006] Furthermore, in a continuous heat treatment furnace in which fuel is burned inside the furnace by a combustion device as described above, if a support roller with a carbon sleeve on its outer surface is used as the support roller, as shown in Patent Documents 3 and 4, the surface will not oxidize and oxides will not accumulate. However, when the temperature inside the furnace becomes high, the carbon in the carbon sleeve reacts with oxygen contained in the combustion exhaust gas from burning the fuel and sublimes into CO or CO2, causing the diameter of the support roller to decrease, which leads to the problem that the metal strip cannot be guided properly. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2010-202959 [Patent Document 2] Japanese Patent Application Publication No. 8-269579 [Patent Document 3] Japanese Patent Application Publication No. 6-322436 [Patent Document 4] Japanese Patent Application Publication No. 7-113115 [Disclosure of the Invention] [Problems that the invention aims to solve]

[0008] The present invention aims to solve the aforementioned problems in a continuous heat treatment furnace in which a long metal strip is driven through the furnace and fuel is burned in the furnace by a combustion device to heat-treat the metal strip.

[0009] In other words, in the continuous heat treatment furnace of the present invention, when a long metal strip is heat-treated in the furnace, if support rollers are provided to ensure that the metal strip runs stably in the furnace, the surface of the metal support rollers may be oxidized by oxygen contained in the combustion exhaust gas from burning fuel, causing oxides to accumulate and damaging the surface of the metal strip being transported. Furthermore, the carbon in support rollers with carbon sleeves on their outer circumference may react with oxygen contained in the combustion exhaust gas from burning fuel to form CO or CO2, sublimation, and a reduction in the diameter of the support rollers, which would otherwise hinder proper guidance of the metal strip, should be prevented. [Means for solving the problem]

[0010] In the continuous heat treatment furnace according to the present invention, in order to solve the above-mentioned problems, a long metal strip is driven 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 by a combustion device, and the above-mentioned Support rollers that stabilize the movement of metal strips inside the furnace are provided as described above. Rather than a combustion device On the downstream side in the direction of metal strip movement, Located on the upstream side in the direction of gas flow within the furnace only In addition to providing the above Located upstream of the support roller in the direction of gas flow within the furnace An inert gas supply device was installed to supply inert gas.

[0011] Furthermore, as in the continuous heat treatment furnace according to the present invention, the combustion device is more efficient than On the downstream side in the direction of metal strip movement, Located on the upstream side in the direction of gas flow within the furnace only When a support roller is provided to stabilize the movement of the metal strip, the support roller , positioned upstream of the support roller in the direction of gas flow within the furnace. When inert gas is supplied from an inert gas supply device, contact between the support roller and oxygen remaining in the combustion exhaust gas from burning fuel is suppressed.

[0012] Here, the continuous heat treatment furnace according to the present invention may be a vertical type in which the metal strip is moved in a furnace provided in the vertical direction, or a horizontal type in which the metal strip is moved in a furnace provided in the horizontal direction. Furthermore, in the case of a vertical type furnace in which the metal strip is moved in a furnace provided in the vertical direction, the metal strip may be moved from top to bottom or from bottom to top within the vertical furnace.

[0013] Furthermore, in the continuous heat treatment furnace according to the present invention, the support roller can be either a support roller with a carbon sleeve on its outer surface or a support roller made of metal, as this eliminates the generation of oxides by oxygen and the sublimation of carbon.

[0014] Furthermore, in the continuous heat treatment furnace according to the present invention, when supplying inert gas to the support roller from the inert gas supply device as described above, the inert gas supply device supplies the inert gas to a position upstream of the support roller in the gas flow direction within the furnace. I am trying to do so. In this way, the support roller is surrounded by an inert gas upstream of the combustion device in the direction of gas flow, so that the combustion exhaust gas from the burning fuel does not come into contact with the support roller, and contact with residual oxygen in the combustion exhaust gas is reliably suppressed.

[0015] Furthermore, in the continuous heat treatment furnace according to the present invention, an oxygen concentration detection device is provided at a position downstream of the support roller in the direction of gas flow within the furnace to detect the oxygen concentration inside the furnace. The oxygen concentration inside the furnace detected by the oxygen concentration detection device is output to a control device, and the control device controls the supply of inert gas to be supplied into the furnace by the inert gas supply device. controlThis allows for the adjustment of the amount of inert gas supplied into the furnace from the inert gas supply device in accordance with the oxygen concentration detected by the oxygen concentration detection device. Using the oxygen concentration at which oxides are generated on the surface of the support rollers or carbon rollers sublimate as a reference, if the detected oxygen concentration is low, the amount of inert gas supplied into the furnace by the inert gas supply device can be reduced to lower running costs, and if the oxygen concentration is high, the amount of inert gas supplied into the furnace can be increased to reliably prevent the generation of oxides on the support rollers or the sublimation of carbon rollers.

[0016] Furthermore, when the metal strip is heat-treated using the continuous heat treatment furnace described above after the entire furnace has been filled with inert gas, the supply of inert gas by the inert gas supply device can be stopped until the oxygen concentration detected by the oxygen concentration detection device reaches a concentration that would adversely affect the support rollers. [Effects of the Invention]

[0017] In a continuous heat treatment furnace according to the present invention, where a metal strip is driven through the furnace and heated in a gas flow within the furnace that flows toward an exhaust pipe from which fuel is burned by a combustion device, if a support roller is provided upstream of the combustion device in the direction of the gas flow within the furnace to stabilize the movement of the metal strip, and an inert gas is supplied to the support roller from an inert gas supply device, contact between the support roller and oxygen contained in the combustion exhaust gas from the burning fuel is suppressed.

[0018] As a result, in the continuous heat treatment furnace of the present invention, when a support roller having a carbon sleeve on its outer peripheral surface is used as the support roller, carbon in the carbon sleeve reacts with oxygen, sublimates into CO or CO2, and the diameter of the roller of the support roller does not decrease, enabling stable guiding of the metal strip. Also, when a metal support roller is used as the support roller, the surface of the metal support roller is not oxidized by oxygen and no oxide deposits on the surface of the metal support roller, preventing damage to the surface of the conveyed metal strip.

Brief Description of the Drawings

[0019] [Figure 1] It is a schematic explanatory diagram showing a state in which a metal strip is heat-treated by running downward from above in a furnace provided vertically in the continuous heat treatment furnace according to an embodiment of the present invention. [Figure 2] In the continuous heat treatment furnace according to the above embodiment, when heat-treating a metal strip in the gas flow in the furnace flowing toward the exhaust pipe by burning fuel in the furnace by a combustion device, an inert gas supply device for supplying an inert gas at a position upstream of the gas flow direction in the furnace from the support roller, and an oxygen concentration detection device for detecting the oxygen concentration in the furnace are provided at a position downstream of the gas flow direction in the furnace from the support roller. It 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. [Figure 3] It is a schematic plan view showing an example of a support roller having a carbon sleeve on its outer peripheral surface in the continuous heat treatment furnace according to the above embodiment.

Best Mode for Carrying Out the Invention

[0020] Hereinafter, a continuous heat treatment furnace according to an embodiment of the present invention will be specifically described with reference to the attached drawings. It should be noted that the continuous heat treatment furnace according to this invention is not limited to those shown in the embodiments below, and can be modified as appropriate without altering the essence of the invention.

[0021] In this embodiment of the continuous heat treatment furnace, as shown in Figures 1 and 2, a long metal strip S, such as a stainless steel strip, is transported by being wound up by a winding device (not shown) located in the lower process of the apparatus. Its orientation is changed downward by an introduction roller 1, and while preventing the outflow of the atmosphere inside the furnace 10 and the intrusion of outside air by a seal roller 14, it is introduced into a vertically oriented furnace 10. Fuel is burned inside the furnace 10 by each combustion device 20 located in the 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 the upper exhaust pipe 13, and a gas flow is created inside the furnace 10 toward the exhaust pipe 13.

[0022] Then, the heated metal strip S is stabilized by a support roller 22 located downstream of the combustion device 20 in the direction of travel of the metal strip S, and guided from the heating section 11 to the cooling section 12 at the bottom of the furnace 10 to cool. The metal strip S is then turned upward by the discharge roller 2 and sent out of the furnace 10. At this time, the metal strip S is guided into the water seal device 3 to prevent the outflow of the atmosphere inside the furnace 10 and the intrusion of outside air.

[0023] Furthermore, in the continuous heat treatment furnace of this embodiment, the support roller 22 used is one that has a carbon sleeve 22a on its outer surface, as shown in Figure 3.

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

[0025] In this embodiment of the continuous heat treatment furnace, the oxygen concentration in the furnace 10 at a position downstream of the support roller 22 in the gas flow direction (above the support roller 22 in the figure) is detected by the oxygen concentration detection device 23. The oxygen concentration detected by the oxygen concentration detection device 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 (below the support roller 22 in the figure) based on the oxygen concentration detected by the oxygen concentration detection device 23. Note that the inert gas may be other gases such as Ar (argon) in addition to N2 (nitrogen).

[0026] In this embodiment of the continuous heat treatment furnace, when the oxygen concentration detected by the oxygen concentration detection device 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 roller 22 in the gas flow direction within the furnace 10 (below the support roller 22 in the figure) to reduce running costs. On the other hand, when the oxygen concentration detected by the oxygen concentration detection device 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 roller 22 in the gas flow direction within the furnace 10 (below the support roller 22 in the figure) to prevent the carbon in the carbon sleeve 22a provided on the outer circumferential surface of the support roller 22 from reacting with oxygen contained in the combustion exhaust gas from burning fuel and sublimating into CO or CO2. For example, when supplying inert gas N2 into the furnace 10 from the inert gas supply device 25 as described above, the supply of inert gas N2 from the inert gas supply device 25 to the furnace 10 is such that the oxygen concentration in the furnace 10 near the support roller 22 is less than the concentration at which carbon does not sublimate (approximately 500 ppm).

[0027] Thus, in this embodiment of the continuous heat treatment furnace, the amount of inert gas N2 supplied from the inert gas supply device 25 to a position upstream of the support roller 22 in the gas flow direction within the furnace 10 (below the support roller 22 in the figure) is controlled by the control device 24. As a result, the carbon in the carbon sleeve 22a provided on the outer circumference of the support roller 22 does not react with oxygen contained in the combustion exhaust gas from burning fuel at high temperatures, sublimating into CO or CO2 and reducing the diameter of the support roller 22. This prevents the metal strip S from running stably within the furnace 10.

[0028] As described above, the 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 within the furnace 10 (below the support roller 22 in the diagram) is guided to the top of the furnace 10 as part of the gas flow within the furnace 10, together with the combustion exhaust gas after the fuel has been burned by each combustion device 20 within the furnace 10, and is exhausted from the exhaust pipe 13.

[0029] In this embodiment, the continuous heat treatment furnace is shown as a vertical furnace 10 with upward gas flow inside, and the equipment is arranged from top to bottom in the following order: exhaust pipe 13, combustion device 20, oxygen concentration detection device 23, support roller 22, and inert gas supply device 25. However, this can also be used in cases where the gas flow inside the vertical furnace 10 is downward, such as when the exhaust pipe 13 is at the bottom of the furnace 10.

[0030] In that case, although not shown in the diagram, the equipment should be arranged from top to bottom in the following order: inert gas supply device 25, support roller 22, oxygen concentration detector 23, combustion device 20, and exhaust pipe 13.

[0031] In the case of a horizontal furnace 10 that transports metal strips S horizontally, although not shown in the diagram, the equipment can be arranged in the following order along the direction of gas flow within the furnace 10: inert gas supply device 25, support roller 22, oxygen concentration detector 23, combustion device 20, and exhaust pipe 13.

[0032] Furthermore, in the continuous heat treatment furnace of this embodiment, at the start of operation, inert gas N2 is supplied into the furnace 10 from the inert gas supply device 25 or the like to fill the entire furnace 10 with inert gas N2. Then, as described above, the metal strip S is introduced into the vertical furnace 10, and the 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, thereby allowing the metal strip S introduced into the furnace 10 to be heat-treated as described above.

[0033] In this configuration, the entire support roller 22 is reliably enveloped in inert gas N2, eliminating any concern about sublimation. As combustion exhaust gas is discharged from the exhaust pipe 13, the concentration of inert gas N2 decreases. When the oxygen concentration detected by the oxygen concentration detection device 23 reaches a level that would adversely affect the carbon in the carbon sleeve 22a provided on the outer surface of the support roller 22, the supply of inert gas N2 into the furnace 10 by the inert gas supply device 25 can be initiated.

[0034] Furthermore, in this embodiment of the continuous heat treatment furnace, a support roller 22 equipped with a carbon sleeve 22a on its outer surface is used, but the support roller 22 is not limited to this type, and a metal roller can also be used as the support roller 22.

[0035] Furthermore, even when a metal roller is used as the support roller 22, if the amount of inert gas N2 supplied from the inert gas supply device 25 to a position upstream of the metal support roller 22 in the gas flow direction within the furnace 10 is controlled as described above, the surface of the metal support roller 22 will not be oxidized by oxygen and oxides will not accumulate on the surface of the metal support roller 22, thereby preventing damage to the surface of the conveyed metal strip S by the accumulated oxides.

[0036] Furthermore, in this embodiment of the continuous heat treatment furnace, the metal strip S is driven from top to bottom within a vertically oriented furnace 10. However, although not shown in the figures, the metal strip S can also be driven from bottom to top within the vertically oriented furnace 10 for heat treatment. [Explanation of symbols]

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

Claims

1. A continuous heat treatment furnace is characterized in that a long metal strip is driven inside the furnace and the metal strip is heat-treated in a flow of gas inside the furnace that flows toward an exhaust pipe from which fuel is burned inside the furnace by a combustion device, and a support roller for stabilizing the movement of the metal strip inside the furnace is provided only at a position downstream of the combustion device in the direction of metal strip movement and upstream of the gas flow inside the furnace, and an inert gas supply device is provided at a position upstream of the support roller in the direction of gas flow inside the furnace for supplying inert gas.

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

3. A continuous heat treatment furnace according to claim 1, characterized in that a support roller having a carbon sleeve on its outer surface is used as the support roller.

4. A continuous heat treatment furnace in which a long metal strip is driven in the furnace and a combustion device burns fuel in the furnace and heats the metal strip in a flow of gas in the furnace that flows toward an exhaust pipe from which the gas is discharged, wherein a support roller for stabilizing the movement of the metal strip in the furnace is provided only at a position downstream of the combustion device in the direction of metal strip movement and upstream of the gas flow in the furnace, an inert gas supply device is provided at a position upstream of the support roller in the direction of gas flow in the furnace for supplying inert gas, an oxygen concentration detection device is provided at a position downstream of the support roller in the direction of gas flow in the furnace for detecting the oxygen concentration in the furnace, the oxygen concentration in the furnace detected by the oxygen concentration detection device is output to a control device, and the control device controls the supply of inert gas to be supplied to the furnace by the inert gas supply device.

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