JP2004183026A - Continuous heat treatment furnace and atmospheric-gas-feeding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a continuous heat treatment furnace which can heat-treat products containing Cr and Si in a carbon furnace, can employ carbon dioxide, sulfur hexafluoride and a fluorine compound as a sealing gas, prevents the inflow of air contents, and reduces the introducing amount of expensive Argon even when it is used as an atmospheric gas, and to provide an atmospheric-gas-feeding method therefor. <P>SOLUTION: In the continuous heat treatment furnace provided with a heating chamber 12, a cooling chamber 13 and a sealing chamber 14, this heat treatment furnace comprises an atmospheric-gas-introducing path 16 for introducing the atmospheric gas into the cooling chamber 12, a sealing-gas-introducing path 18 for introducing the sealing gas into the sealing chamber 14, a mixed-gas-recovering path 19 for recovering a mixture gas of the atmospheric gas and the sealing gas from the inside of the furnace, a gas-separating and refining unit 20 for separating and refining the atmospheric gas from the recovered mixture gas, and a refined atmospheric gas introducing path 21 for introducing the separated and refined atmospheric gas into the cooling chamber. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a continuous heat treatment furnace and an atmosphere gas supply method, and more particularly, to a continuous heat treatment in which heat treatment such as firing, sintering, annealing, and brazing of a metal material or a metal product is continuously performed in a specific gas atmosphere. More particularly, the present invention relates to a continuous heat treatment furnace capable of efficiently forming the gas atmosphere and a method for supplying an atmosphere gas in the continuous heat treatment furnace.
[0002]
[Prior art]
In a continuous heat treatment furnace (continuous furnace) for continuously performing various heat treatments on metal materials, hydrogen gas is generally used as an atmosphere gas. Hydrogen gas is a gas that may explode depending on handling, but has the advantage that it is useful for reducing the trace amount of oxygen that enters the furnace with the introduction of metal materials. . In addition, a method has been adopted in which nitrogen gas is supplied as a seal gas to an inlet / outlet portion of a continuous furnace to suppress the inflow of oxidizing components (oxygen, carbon dioxide, moisture, and the like) in the atmosphere that adversely affect heat treatment (for example, See Patent Document 1.).
[0003]
Since the inside of the continuous furnace is heated to a high temperature, the atmosphere gas easily moves to the top of the furnace, and the atmospheric components easily enter the bottom side. By supplying, it is possible to suppress the intrusion of atmospheric components into the furnace. Since the nitrogen gas used as the sealing gas is an inert gas, it does not particularly affect the product. By using the nitrogen gas as the seal gas in this manner, it is possible to suppress the consumption of the atmosphere gas, hydrogen, and to reduce the amount of the atmosphere gas introduced.
[0004]
[Patent Document 1]
JP-A-6-257949 (page 2-3, FIG. 1)
[0005]
[Problems to be solved by the invention]
On the other hand, when the content of chromium (Cr) or silicon (Si) is small or when the treatment temperature is relatively low, there is no problem with the conventional heat treatment using a continuous furnace as described above. BACKGROUND ART For applications such as SiC filters for engines and sintered stainless steel products, heat treatment of metal materials (products) containing a large amount of Cr, Si, or the like at high temperatures has been performed.
[0006]
Since Cr and Si easily react with nitrogen gas at high temperatures, there is a problem that the product is nitrided and the quality is deteriorated. Therefore, when heat-treating a product containing these components, if nitrogen gas is used as the sealing gas for the continuous furnace, a small amount of nitrogen gas may enter the continuous furnace, and the product may be nitrided. Can not do it. For this reason, there is a problem that the introduction amount of the atmosphere gas cannot be reduced by the seal gas.
[0007]
Gases having a high specific gravity that can be used as the seal gas include nitrogen gas, carbon dioxide, sulfur hexafluoride, and fluorine compounds in addition to nitrogen gas. When mixed, there is a problem that the product is oxidized, or the seal gas itself is decomposed into a toxic gas.
[0008]
Further, in a continuous furnace made of metal, when the processing temperature is increased, the metal constituting the furnace body is softened, and the top and the bottom may be bent by gravity. There is a problem. For this reason, when a product containing a large amount of Cr or Si is subjected to a large amount of heat treatment at a high temperature, a ceramic carbon furnace may be used. However, when hydrogen gas is used as an atmosphere gas in a carbon furnace, there is a problem in that carbon and hydrogen, which are the main components of the furnace, react with each other to generate hydrocarbons, and the hydrocarbons deplete carbon in the furnace material. Therefore, argon gas, which is more expensive than hydrogen gas, is used as the atmosphere gas of the carbon furnace.
[0009]
However, even when argon gas is used as the atmosphere gas of the carbon furnace, the use of nitrogen gas as the seal gas causes the above-described nitriding problem.Since nitrogen gas has a lower specific gravity than argon gas, it is effective as a seal gas. Instead, it is not suitable for use as a sealing gas. In addition, carbon dioxide, sulfur hexafluoride, and fluorine compounds, which have a higher specific gravity than argon gas, are mixed with the atmosphere gas in the furnace and exposed to high temperatures at which heat treatment is performed. Has the problem of decomposing into toxic gas. As described above, in a continuous furnace using an argon gas as an atmosphere gas, there is no effective means for reducing the amount of introduced atmosphere gas.
[0010]
Therefore, the present invention can also be applied to a case where a product containing Cr or Si, which easily reacts with nitrogen at a high temperature, is heat-treated in a carbon furnace made of ceramic, and it is possible to use carbon dioxide, sulfur hexafluoride, or a fluorine compound as a seal gas. It is possible to prevent the inflow of atmospheric components that adversely affect the heat treatment, and the sealing gas itself does not adversely affect the product. Even if expensive argon is used as the atmospheric gas, the introduction amount can be reduced. It is an object of the present invention to provide a continuous heat treatment furnace and a method for supplying an atmosphere gas.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, in the continuous heat treatment furnace of the present invention, in a continuous heat treatment furnace having a heating chamber, a cooling chamber, and a seal chamber in order in a transport direction of an object, an atmosphere gas is introduced into the cooling chamber. An atmosphere gas introduction path for introducing the seal gas into the seal chamber; a mixed gas recovery path for collecting a mixed gas in which the atmosphere gas and the seal gas are mixed from the furnace; Atmosphere gas purifying means for separating and purifying the atmosphere gas from the mixed gas collected in the gas recovery path, and a purified atmosphere gas introduction path for introducing the atmosphere gas separated and purified by the atmosphere gas purifying means into the cooling chamber. It is characterized by having.
[0012]
Further, the continuous heat treatment furnace of the present invention includes a seal gas purifying means for separating and purifying the seal gas from the mixed gas, and introducing the seal gas separated and purified by the seal gas purifying means into the seal chamber. An atmosphere gas purifying means for separating and purifying an atmospheric gas, and a seal gas purifying means for separating and purifying the seal gas are configured as one gas separation / purification apparatus, characterized by having a seal gas introduction path. It is characterized by:
[0013]
Furthermore, the mixed gas recovery path is connected to the sealing chamber on the cooling chamber side of the sealing gas introduction path in the sealing chamber, and is particularly connected to the bottom of the sealing chamber. In addition, at least one of the cooling chamber, the sealing chamber, and the mixed gas recovery path is provided with an atmospheric component sensing means for detecting an atmospheric component, and the amount of the sealing gas introduced from the sealing gas introducing path is adjusted. At least one of a seal gas introduction amount adjusting means and a mixed gas discharging path for discharging the mixed gas collected in the mixed gas collecting path without introducing the mixed gas into the gas purifying means is provided.
[0014]
In addition, seal gas sensing means is provided upstream of the connection portion of the mixed gas recovery path, and atmosphere gas introduction amount adjustment means for adjusting the amount of atmosphere gas introduced from the atmosphere gas introduction path is provided. I have.
[0015]
Further, the method for supplying an atmosphere gas in the continuous heat treatment furnace of the present invention is a method for supplying an atmosphere gas in a continuous heat treatment furnace having a heating chamber, a cooling chamber, and a seal chamber in order in the transport direction of the object, Atmospheric gas is introduced into the cooling chamber, and sealing gas is introduced into the sealing chamber, and a mixed gas in which the sealing gas in the sealing chamber and the atmospheric gas in the cooling chamber are mixed is recovered from the furnace. After separating and purifying the atmosphere gas and the sealing gas in the mixed gas, the purified atmosphere gas is introduced into the cooling chamber, and the sealing gas after the separation and purification is further supplied to the sealing chamber. It is characterized by being introduced.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a system diagram showing one embodiment of a gas supply system in the continuous heat treatment furnace of the present invention. In the continuous heat treatment furnace, the heating chamber 12 for heat-treating the product and the heat treatment are completed in the direction of conveyance of the conveyor belt 11 for conveying the metal material or the product (object to be processed) to be heat-treated. A cooling chamber 13 for cooling the product and a seal chamber 14 for preventing the air from flowing into the furnace are provided. By passing through the seal 13 and the seal chamber 14 in order, after a predetermined heat treatment is performed, it is cooled to a predetermined temperature.
[0017]
An atmosphere gas introduction path 16 for introducing an atmosphere gas supplied from an atmosphere gas supply source 15 is connected to the cooling chamber 13, and a sealing gas supplied from a sealing gas supply source 17 is connected to the sealing chamber 14. Is connected to a seal gas introduction path 18 for introducing the gas. Further, a mixed gas recovery path 19 for recovering a mixed gas in which the atmospheric gas and the seal gas are mixed from the inside of the seal chamber 14 is connected to the bottom of the seal chamber 14. The mixed gas recovery path 19 is connected to a gas separation / purification apparatus 20. The gas separation / purification apparatus 20 has a purified atmosphere gas introduction path 21 for re-introducing the separated and purified atmosphere gas into the cooling chamber 13. And a purified seal gas introduction path 22 for re-introducing the separated and purified seal gas into the seal chamber 14.
[0018]
The atmosphere gas introduction path 16 is provided so as to introduce the atmosphere gas from the upper portion on the upstream side of the cooling chamber 13, that is, the ceiling portion near the heating chamber 12 where the room temperature is high, and is provided at the furnace entrance and exit. Most of the atmospheric gas flowing into the cooling chamber 13 from the atmospheric gas introduction path 16 flows toward the heating chamber 12 due to the adjustment of the suction duct and the action of the physical curtain, and the inside of the heating chamber 12 is heat-treated. The atmosphere is suitable for
[0019]
Further, the seal gas introduction path 18 is introduced into the seal chamber 14 in a laminar flow state by a downward flow from the ceiling portion of the seal chamber 14 so as to prevent atmospheric components from entering the furnace from the furnace outlet portion. I have. This shuts off the air that enters the furnace from the furnace outlet portion, and allows the air to flow through the bottom of the seal chamber 14 even if the air enters, and is discharged from the mixed gas recovery path 19 and does not flow toward the cooling chamber 13. Like that.
[0020]
The mixed gas recovery path 19 is provided at a position closer to the cooling chamber 13 on the upstream side than the connection position of the seal gas introduction path 18 in the seal chamber 14, and the seal gas introduced into the seal chamber 14 and the cooling chamber The gas mixture with the atmospheric gas introduced into the seal chamber 14 and introduced into the seal chamber 14 is sucked.
[0021]
By sucking the gas in the furnace from such a position, it is possible to reliably prevent the seal gas having a higher specific gravity than the atmospheric gas from flowing in the direction of the cooling chamber 13, and as described above, the furnace outlet portion Even if the air enters the seal chamber 14 from above, the air component is sucked together with the mixed gas in the mixed gas recovery path 19 so that the air component does not enter the cooling chamber 13. Therefore, in order to heat-treat a product containing a large amount of Cr or Si at a high temperature, when argon gas is used as the atmosphere gas, carbon dioxide, sulfur hexafluoride, or a fluorine compound having a higher specific gravity than the argon gas is used as the seal gas. In addition, nitrogen gas and oxygen gas as atmospheric components are prevented from flowing into the cooling chamber 13 and the heating chamber 12 in a high-temperature atmosphere.
[0022]
The gas separation / purification device 20 separates the atmosphere gas from the mixed gas collected in the mixed gas recovery path 19 and has a purity equal to or higher than the purity of the atmosphere gas supplied from the atmosphere gas supply source 15 or as an atmosphere gas. The atmosphere gas (purified atmosphere gas), which is purified to a usable purity and separated and purified by the gas separation / purification apparatus 20, is re-introduced into the cooling chamber 13 through the purified atmosphere gas introduction path 21. You. When the seal gas can be separated and purified from the mixed gas, the purified seal gas (purified seal gas) can be re-introduced into the seal chamber 14 through the purified seal gas introduction path 22.
[0023]
Further, depending on the type of the atmosphere gas and the seal gas to be used and the configuration of the gas separation / purification apparatus 20, when the collected gas mixture contains an atmospheric component, the atmospheric gas or the seal gas and the nitrogen gas or the atmospheric component are mixed. Many steps are required for separation from oxygen gas, and there is a disadvantage that the apparatus becomes large. Normally, the entry of atmospheric components is prevented by the action of the seal gas. However, in order to prepare for the intrusion of atmospheric components, at least one of the cooling chamber 13, the seal chamber 14, and the mixed gas recovery path 19 is provided. A sensor (atmospheric component sensing means, not shown) for sensing at least one of atmospheric components such as oxygen gas, nitrogen gas, carbon dioxide, and moisture is provided at a location, and the mixed gas recovery path 19 A mixed gas discharge path 23 is provided for discharging the mixed gas mixed with the separated atmospheric components without introducing the mixed gas into the gas separation / purification device 20. When it is detected that the atmospheric components have entered the furnace, the mixed gas By opening the valve 23V of the discharge path 23 and discharging the recovered mixed gas from the mixed gas discharge path 23 to the outside of the system, separation from the atmosphere gas and the seal gas is difficult. Air component flows into the gas separation and purification apparatus 20, it can be prevented by lowering the purity of the purified atmosphere gas or purified seal gas such.
[0024]
Further, a flow control valve (seal gas introduction amount adjusting means) 18V for adjusting the introduction amount of the seal gas is provided in the seal gas introduction path 18 so that the atmospheric component sensing means allows atmospheric components to enter the furnace. When it is detected that the sealing gas has been introduced, the sealing gas introduction amount adjusting means 18V is operated to increase the introduction amount of the sealing gas, so that the intrusion of atmospheric components into the furnace can be reliably prevented, and the atmospheric components can be prevented. Can be prevented with a minimum necessary amount of the sealing gas introduced, so that the cost required for the sealing gas can be reduced.
[0025]
Further, if the amount of the atmosphere gas introduced from the atmosphere gas introduction path 16 becomes insufficient, or if the amount of the mixed gas recovered from the mixed gas recovery path 19 becomes smaller than the amount of the seal gas introduced from the seal gas introduction path 18, the furnace It becomes difficult to sufficiently recover the seal gas and the atmospheric components from the inside into the mixed gas recovery path 19, and the seal gas and the atmospheric components may flow into the cooling chamber 13. For this reason, a sensor (seal gas sensing means, not shown) for sensing a seal gas is provided upstream of the connection portion of the mixed gas recovery path 19, for example, at the most upstream portion of the cooling chamber 13, and the like. When the means detects the seal gas, the atmosphere gas introduction amount adjusting means 16V provided in the atmosphere gas introduction path 16 is operated to increase the introduction amount of the atmosphere gas, or the amount of the seal gas introduced from the seal gas introduction path 18 At least one of the operations of reducing the amount of mixed gas, increasing the amount of mixed gas recovered from the mixed gas recovery path 19, and opening the valve 23V of the mixed gas discharge path 23 to discharge the mixed gas out of the system. By performing the two operations, it is possible to prevent the sealing gas from entering the cooling chamber 13.
[0026]
Further, a sensor (atmosphere gas sensing means, not shown) for sensing the atmosphere gas is provided downstream of the connection portion of the mixed gas recovery path 19, and when the atmosphere gas sensing means senses the atmosphere gas, the atmosphere gas is sensed. By performing at least one of operations such as reducing the amount of introduced gas, increasing the amount of introduced seal gas, and increasing the amount of mixed gas collected, introduction of an extra atmosphere gas can be avoided. .
[0027]
Further, by providing the seal gas sensing means and the atmosphere gas sensing means side by side and performing the above-described operation in conjunction with the operation thereof, the atmosphere gas, the seal gas, and the recovered gas can be obtained. Can be balanced, and the use efficiency of the atmosphere gas and the seal gas can be improved.
[0028]
The gas separation / purification device 20 may be a suitable separation / purification device according to various conditions such as the type and usage amount of the atmosphere gas and the seal gas, the mixing ratio, and the type and mixing amount of other impurity components. A separation apparatus (PSA), a temperature fluctuation adsorption separation apparatus (TSA), a membrane separation apparatus, a cryogenic liquefaction separation apparatus, and the like can be used, and a plurality of these can also be used.
[0029]
For example, when argon gas is used as the atmosphere gas and carbon dioxide is used as the seal gas, the argon gas in the mixed gas can be continuously separated and purified by PSA or TSA using an adsorbent such as zeolite. . Also, when the atmosphere gas is an argon gas and the seal gas is a fluorine compound-based gas or sulfur hexafluoride, the separation and purification of the argon gas is performed by using a suitable adsorbent, for example, activated carbon or zeolite. be able to. Further, when the atmosphere gas is hydrogen gas and the sealing gas is nitrogen gas, a suitable adsorbent, for example, PSA or TSA using zeolite, or a suitable separation membrane, for example, a membrane separation apparatus using palladium Thereby, hydrogen gas can be continuously separated and purified.
[0030]
In addition, it is preferable to set the temperature of the agent to 30 ° C. or lower from the viewpoint of separation and purification efficiency. Further, when impurities such as moisture are generated due to the heat treatment of the product, it is preferable to remove these impurity components before separating the atmosphere gas. For example, a mixed gas is brought into contact with an alumina-based adsorbent. In this way, the mixed gas is separated and purified after removing water from the mixed gas.
[0031]
By separating and refining and reusing the atmosphere gas in this manner, the consumption of the atmosphere gas can be reduced, so that even if an expensive argon gas is used as the atmosphere gas, an increase in gas cost can be suppressed. it can. Further, since the sealing gas can be prevented from flowing into the cooling chamber 13 and the heating chamber 12 and the intrusion of atmospheric components can be prevented, argon gas is used as the atmosphere gas, and carbon dioxide, sulfur hexafluoride, fluorine By using a compound, it becomes possible to heat-treat a product containing a large amount of Cr or Si at a high temperature and a large amount using a large-sized carbon furnace. Therefore, the cost of heat treatment of a product containing Cr or Si can be significantly reduced. In addition, the heat treatment cost can be further reduced by reusing the sealing gas.
[0032]
In this embodiment, the seal chamber 14 is provided only on the product outlet side of the continuous heat treatment furnace. However, a seal chamber having a similar structure can be provided on the product inlet side. At this time, the path for sucking the mixed gas from the seal chamber provided on the product inlet side may be arranged near the heating chamber 12 on the downstream side of the seal chamber. Further, in the present embodiment, the description has been made such that the gas separation and purification device 20 separates and purifies the atmosphere gas and the seal gas. However, a device for separating and purifying the atmosphere gas from the mixed gas (atmosphere gas purification means), An apparatus for separating and purifying the seal gas from the mixed gas (seal gas purifying means) may be separately provided, for example, in series, and each gas may be purified separately. Further, the present invention is particularly effective in a carbon furnace, but can also be applied to a general metal furnace.
[0033]
【The invention's effect】
As described above, according to the present invention, it is possible to reliably prevent the sealing gas and the atmospheric components from flowing into the heating chamber or the cooling chamber in a high-temperature atmosphere, and to reduce the atmosphere from the mixed gas recovered from the furnace. Since the gas and the seal gas are separated and purified and reused, the consumption of the atmosphere gas and the seal gas can be reduced. As a result, even if expensive argon gas is used as the atmosphere gas, an increase in gas cost can be suppressed. Therefore, argon gas is used as the atmosphere gas, and carbon dioxide or hexafluoride having a higher specific gravity than the argon gas is used as the seal gas. By using a sulfur compound or a fluorine compound, it becomes possible to heat-treat a product containing a large amount of Cr or Si at a high temperature and a large amount using a large-sized carbon furnace.
[Brief description of the drawings]
FIG. 1 is a system diagram showing one embodiment of a gas supply system in a continuous heat treatment furnace of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... Conveyer belt, 12 ... Heating room, 13 ... Cooling room, 14 ... Seal room, 15 ... Atmosphere gas supply source, 16 ... Atmosphere gas introduction route, 17 ... Seal gas supply source, 18 ... Seal gas introduction route, 19 ... Mixed gas recovery path, 20: gas separation / purification device, 21: purified atmosphere gas introduction path, 22: purified seal gas introduction path, 23: mixed gas discharge path

Claims (9)

In a continuous heat treatment furnace having a heating chamber, a cooling chamber, and a sealing chamber in order in the transport direction of the workpiece, an atmosphere gas introduction path for introducing an atmosphere gas into the cooling chamber, and a sealing gas into the sealing chamber. A seal gas introduction path, a mixed gas recovery path for recovering a mixed gas in which the atmosphere gas and the seal gas are mixed from the furnace, and an atmosphere gas is separated and purified from the mixed gas recovered in the mixed gas recovery path. A continuous heat treatment furnace comprising: atmosphere gas purification means; and a purification atmosphere gas introduction path for introducing the atmosphere gas separated and purified by the atmosphere gas purification means into the cooling chamber. A seal gas purifying means for separating and refining the seal gas from the mixed gas, and a purification seal gas introduction path for introducing the seal gas separated and purified by the seal gas purifying means into the seal chamber. The continuous heat treatment furnace according to claim 1. 3. The continuous heat treatment according to claim 2, wherein the atmosphere gas purifying means for separating and purifying the atmosphere gas and the seal gas purifying means for separating and purifying the seal gas are constituted as one gas separation / purification apparatus. Furnace. 2. The continuous heat treatment furnace according to claim 1, wherein the mixed gas recovery path is connected to the sealing chamber on the cooling chamber side of the sealing gas introduction path in the sealing chamber. 3. The continuous heat treatment furnace according to claim 4, wherein the mixed gas recovery path is connected to a bottom of the seal chamber. At least one of the cooling chamber, the seal chamber, and the mixed gas recovery path is provided with an atmospheric component sensing means for detecting an atmospheric component, and a seal gas introduction that adjusts a seal gas introduction amount from the seal gas introduction path. 2. The apparatus according to claim 1, wherein at least one of an amount adjusting means and a mixed gas discharging path for discharging the mixed gas collected in the mixed gas collecting path without introducing the mixed gas into the gas purifying means is provided. Continuous heat treatment furnace. A seal gas sensing means is provided upstream of a connection portion of the mixed gas recovery path, and an atmosphere gas introduction amount adjusting means for adjusting an atmosphere gas introduction amount from the atmosphere gas introduction path is provided. 2. The continuous heat treatment furnace according to 1. A method for supplying an atmosphere gas in a continuous heat treatment furnace having a heating chamber, a cooling chamber, and a sealing chamber in the order of transporting the workpiece, wherein the atmosphere gas is supplied to the cooling chamber, and the sealing gas is supplied to the sealing chamber. After the introduction, the mixed gas in which the sealing gas in the sealing chamber and the atmosphere gas in the cooling chamber are mixed is recovered from the furnace, and the atmosphere gas and the sealing gas in the recovered mixed gas are separated and purified. And supplying a purified atmosphere gas to the cooling chamber. The method according to claim 7, wherein the sealing gas after separation and purification is introduced into the sealing chamber.

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