Heat treatment furnace

Abstract

To provide a heat treatment furnace in which, when an object to be treated is heat-treated in a furnace by using an inert gas essentially consisting of a nitrogen gas and a heat absorption type modified gas, the index value CP of a carbon potential in the atmosphere gases can be easily adjusted without remarkably changing the amount of the absorption type modified gas.SOLUTION: Regarding a heat treatment furnace in which an object to be treated is heat-treated in a furnace 10 by using an inert gas GU essentially consisting of a nitrogen gas and a heat absorption type modified gas GR as atmosphere gases in the furnace, a hydrocarbon gas GC is added upon adjusting the index value CP [(a CO concentration)2 / (a CO2 concentration)] of a carbon potential in the atmosphere gases.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a heat treatment furnace for heat treating a workpiece, such as a coil made of wires, in an atmosphere gas. In particular, the atmosphere gas in the furnace is an inert gas mainly composed of nitrogen gas and an endothermic Transmute In a heat treatment furnace in which a workpiece is heat-treated using a gas, Transmute Without significantly changing the amount of gas, the carbon potential index value CP [(CO concentration) 2 It is characterized by the fact that the CO2 concentration can be easily adjusted. [Background technology]

[0002] BACKGROUND ART Conventionally, a heat treatment furnace has been used in which an object to be treated, such as a coil made up of wires or other wire materials, is annealed by subjecting it to a non-oxidizing heat treatment in an atmospheric gas within the furnace.

[0003] Furthermore, when heat treating a workpiece having an oxidized surface, a conventional heat treatment furnace is used. In Patent Document 1, the index value of the carbon potential of the atmospheric gas in the furnace, CP [(CO concentration) 2 / (CO2 concentration)], the endothermic type supplied to the furnace Transmute In Patent Document 2, an endothermic type gas containing CO gas is used as a reducing atmosphere gas for annealing metals. Transmute It has been shown that the gas is mixed with nitrogen and used to control the carbon potential index value CP, thereby preventing decarburization and carburization from occurring on the surface of the metal being treated.

[0004] As shown in the above-mentioned Patent Documents 1 and 2, the index value CP of the carbon potential of the atmospheric gas in the furnace is calculated by an endothermic type Transmute When controlling by the amount of gas, Transmute It becomes necessary to change the amount of gas produced and fed into the furnace.

[0005] However, endothermic Transmute The equipment for producing the gas is very expensive and endothermic. Transmute The running costs for changing the amount of gas produced are high, and the index value of the carbon potential of the atmospheric gas in the furnace is an endothermic Transmute Controlling the gas flow rate is extremely disadvantageous in terms of cost and the like.

[0006] Therefore, in the present invention, a low-cost hydrocarbon gas is used as an endothermic Transmute The carbon potential index value of the atmosphere gas in the furnace is controlled by the amount of hydrocarbon gas used in combination with the gas.

[0007] If a large amount of hydrocarbon gas is used, the carbon content in the atmosphere gas in the furnace increases, which may cause souding in the furnace and contaminate the workpiece.

[0008] However, based on the inventor's experience, the amount of hydrocarbon gas is endothermic. Transmute It was found that souding did not occur if the gas was 5 vol% or less, and that souding did not occur if the gas was 1 vol% or less. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-76986 [Patent Document 2] Japanese Patent Application Publication No. 2019-189942 DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0010] The present invention relates to a heat treatment furnace for annealing a workpiece, such as a coil made of wires, by heat treating it in an atmosphere gas in the furnace, and the atmosphere gas in the furnace is a mixture of an inert gas mainly composed of nitrogen gas and an endothermic Transmute The present invention aims to solve the above-mentioned problems that arise when a workpiece is heat-treated in a furnace using a gas.

[0011] That is, in the present invention, the atmospheric gas in the furnace is a mixture of an inert gas mainly composed of nitrogen gas and an endothermic Transmute In a heat treatment furnace in which a workpiece is heat-treated using gas, an endothermic type gas is supplied into the furnace. Transmute Without significantly changing the amount of gas, the carbon potential index value CP [(CO concentration) 2 The objective of this invention is to make it possible to easily adjust the [(CO2 concentration)] to an appropriate value while reducing running costs. [Means for solving the problem]

[0012] In order to solve the above-mentioned problems, the heat treatment furnace according to the present invention uses an inert gas containing nitrogen gas as the main component and an endothermic gas as the atmospheric gas in the furnace. Transmute In a heat treatment furnace in which a workpiece is heat-treated using a gas, Adding hydrocarbon gas to the atmospheric gas The carbon potential index value CP [(CO concentration) 2 / (CO2 concentration)] With the amount of endothermic converted gas in the atmospheric gas kept constant, the amount of hydrocarbon gas added to the atmospheric gas is changed within a range below a specified value at which sooting does not occur in the furnace, and the amount of inert gas containing nitrogen gas as a main component in the atmospheric gas is changed to adjust the carbon potential index value CP of the atmospheric gas. I did so.

[0013] In this way, the atmosphere gas is an inert gas mainly composed of nitrogen gas and an endothermic Transmute In a heat treatment furnace using a gas, when a hydrocarbon gas is added to adjust the carbon potential index value CP of the atmospheric gas, With the amount of endothermic gas in the atmosphere gas kept constant, The index value CP of the carbon potential in the atmospheric gas can be easily adjusted.

[0014] For example, if methane (CH4) is added to the furnace as a hydrocarbon gas when the carbon potential index value (CP) of the atmospheric gas in the furnace drops, this methane (CH4) will react with carbon dioxide (CO2) as shown in the following formula: CH4 + CO2 = 2CO + 2H2

[0015] As a result, the proportion of carbon dioxide CO2 in the atmospheric gas decreases, while the proportion of carbon monoxide CO increases, and the carbon potential index value CP increases. Furthermore, if the carbon potential index value CP increases more than necessary as a result of adding hydrocarbon gas to the atmospheric gas, the amount of hydrocarbon gas added to the atmospheric gas is reduced.

[0016] In the heat treatment furnace according to the present invention, the carbon potential index value CP of the atmospheric gas is adjusted by adding a hydrocarbon gas as described above, thereby making it possible to adjust the change in the carbon concentration on the surface of the workpiece during heat treatment.

[0017] In addition, in the heat treatment furnace according to the present invention, teeth When adding a hydrocarbon gas to the atmospheric gas as described above, hand The amount of hydrocarbon gas added to the atmospheric gas is set to a value below the specified value at which sooting does not occur in the furnace. Tei Generally, the amount of the hydrocarbon gas added to the atmospheric gas is determined by the amount of the endothermic Transmute It is preferable that the amount of the gas is 5 vol% or less, and more preferably, the endothermic type Transmute The concentration should be 1 vol% or less of the gas.

[0018] In the heat treatment furnace according to the present invention, when adjusting the index value CP of the carbon potential in the atmospheric gas, hand The amount of hydrocarbon gas added to the atmospheric gas as described above is not more than the specified value. While changing within the range of The amount of inert gas, mainly composed of nitrogen gas, in the atmosphere gas is changed. do.

[0019] In other words, when the amount of inert gas containing nitrogen gas as the main component used in the atmospheric gas is increased, the CO concentration and CO2 concentration in the atmospheric gas decrease, but the carbon potential index value CP (CO concentration) 2 It is expressed as / (CO2 concentration), (CO concentration) 2 Since the decrease in the amount of inert gas is greater than the decrease in the CO2 concentration, the carbon potential index value CP of the atmospheric gas decreases. On the other hand, if the amount of inert gas is decreased, the carbon potential index value CP of the atmospheric gas increases, in contrast to the above case. Furthermore, in the heat treatment furnace according to the present invention, even if the amount of the hydrocarbon gas added to the atmospheric gas is increased to a specified value while keeping the amount of endothermic converted gas in the atmospheric gas constant, if the carbon potential index value CP in the atmospheric gas is lower than the lower limit of the set range, the amount of endothermic converted gas in the atmospheric gas can be increased to adjust the carbon potential index value CP in the atmospheric gas. Furthermore, in the heat treatment furnace according to the present invention, even if the amount of the hydrocarbon gas added to the atmospheric gas is set to zero while keeping the amount of endothermic converted gas in the atmospheric gas constant, if the carbon potential index value CP in the atmospheric gas becomes higher than the upper limit of the set range, the amount of endothermic converted gas in the atmospheric gas can be reduced to adjust the carbon potential index value CP in the atmospheric gas.

[0020] In the heat treatment furnace according to the present invention, it is preferable that the inner wall surface of the furnace is coated with a metal catalyst that promotes the decomposition of the hydrocarbon gas. By coating the inner wall surface of the furnace with a metal catalyst that promotes the decomposition of the hydrocarbon gas in this way, the occurrence of sooting in the furnace can be further suppressed. [Effects of the Invention]

[0021] As described above, the present invention uses an inert gas containing nitrogen gas as the main component and an endothermic gas as the atmospheric gas in the furnace. Transmute In a heat treatment furnace in which a workpiece is heat-treated using a gas, Adding a hydrocarbon gas to the atmospheric gas, The carbon potential index value CP [(CO concentration) 2 / (CO2 concentration)], With the amount of endothermic gas in the atmosphere gas kept constant, the amount of hydrocarbon gas added to the atmosphere gas is changed within a range below a specified value at which sooting does not occur in the furnace, and the amount of inert gas mainly composed of nitrogen gas in the atmosphere gas is changed. Therefore, the endothermic type Transmute It has become possible to easily adjust the carbon potential index value CP of the atmospheric gas without significantly changing the amount of gas.

[0022] As a result, in the heat treatment furnace of the present invention, when adjusting the index value CP of the carbon potential, a low-cost hydrocarbon gas is used, so that the endothermic type gas supplied into the furnace as in the conventional heat treatment furnace is not required. TransmuteThere is no need to significantly change the amount of gas, and the carbon potential index value CP [(CO concentration) 2 / (CO2 concentration)] can be easily adjusted to the appropriate value, and Transmute There is no need to enlarge the gas production equipment, which significantly reduces equipment costs and Transmute The running costs when changing the amount of gas produced have also been reduced. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a schematic explanatory view showing a heat treatment furnace according to an embodiment of the present invention. [Figure 2] FIG. 10 is a diagram showing an example of adjusting the amount of endothermic converted gas and the amount of hydrocarbon gas supplied into the heat treatment furnace according to the embodiment when the carbon potential index value CP[(CO concentration) / (CO concentration)] of the atmospheric gas in the furnace changes. BEST MODE FOR CARRYING OUT THE INVENTION

[0024] Hereinafter, a heat treatment furnace according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. Note that the 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.

[0025] In the heat treatment furnace of this embodiment, as shown in FIG. 1, a first adjusting valve 11a is provided in an inert gas guide pipe 11 that guides an inert gas GU containing nitrogen gas as a main component into a furnace 10, and an endothermic type Transmute Endothermic type that guides gas GR into furnace 10 Transmute The gas guide pipe 12 is provided with a second adjusting valve 12a, and the hydrocarbon gas guide pipe 13 that guides the hydrocarbon gas GC to the furnace 10 is provided with a third adjusting valve 13a.

[0026] The inert gas GU guided through the inert gas guide pipe 11 and the endothermic type TransmuteEndothermic type guided through gas guide tube 12 Transmute The gas GR and the hydrocarbon gas GC guided through the hydrocarbon gas guide pipe 13 are supplied into the furnace 10 from the gas supply pipe 14 .

[0027] In the heat treatment furnace of this embodiment, the atmospheric gas in the furnace 10 is sampled by a sampling pipe 15, and the carbon monoxide CO and carbon dioxide CO2 contained in the atmospheric gas are analyzed by a CO, CO2 analyzer 16.

[0028] The results of the analysis of carbon monoxide CO and carbon dioxide CO by the CO, CO2 analyzer 16 are output to the control device 17, which then calculates the carbon potential index value CP [(CO concentration) 2 / (CO2 concentration)] is calculated.

[0029] Based on the index value CP of the carbon potential thus calculated, the control device 17 controls the first adjusting valve 11a provided in the inert gas guide pipe 11 and the endothermic type Transmute The second adjusting valve 12a provided in the gas guide pipe 12 and the third adjusting valve 13a provided in the hydrocarbon gas guide pipe 13 are controlled to adjust the inert gas GU supplied from the gas supply pipe 14 into the furnace 10, and the endothermic type Transmute The amounts of gas GR and hydrocarbon gas GC are adjusted.

[0030] In addition, in the heat treatment furnace of this embodiment, a fourth adjustment valve 18a is provided in the exhaust pipe 18 that exhausts the atmospheric gas inside the furnace 10 to the outside, and this fourth adjustment valve 18a can be adjusted to control the amount of atmospheric gas exhausted from inside the furnace 10 to the outside through the exhaust pipe 18.

[0031] Furthermore, in the heat treatment furnace of this embodiment, a metal catalyst t (e.g., nickel) that promotes the decomposition of the hydrocarbon gas GC is applied to the inner surface of the furnace 10, thereby promoting the decomposition of the hydrocarbon gas GC supplied to the furnace 10 and preventing sooting from occurring within the furnace 10.

[0032] Next, in the heat treatment furnace of this embodiment, the index value CP [(CO concentration) 2 An example of controlling the CO2 concentration so that the CO2 concentration falls within a predetermined range will be described with reference to FIG.

[0033] In the example shown in FIG. 2, initially, the first adjusting valve 11a provided in the inert gas guide pipe 11 and the endothermic type Transmute The second adjusting valve 12a provided in the gas guide pipe 12 is adjusted to supply the inert gas GU to the furnace 10 and the endothermic type Transmute While adjusting the amount of gas GR, the third adjustment valve 13a of the hydrocarbon gas guide pipe 13 is closed to prevent the hydrocarbon gas GC from being supplied into the furnace 10, and the carbon potential index value CP [(CO concentration) 2 / (CO2 concentration)] is set to a set value suitable for performing heat treatment such as annealing on a workpiece (not shown) such as steel.

[0034] Then, while the carbon potential index value CP is set to the set value in this manner, and the workpiece is being heat-treated, the concentrations of carbon monoxide CO and carbon dioxide CO2 in the atmospheric gas in the furnace 10 change, and this is detected by the CO, CO2 analyzer 16 and output to the control device 17. When the carbon potential index value CP in the atmospheric gas calculated by this control device 17 falls close to the lower limit of the set value, as at point a in Figure 2, the control device 17 opens the third adjustment valve 13a in the hydrocarbon gas guide pipe 13 to supply hydrocarbon gas GC into the furnace 10, increasing the amount of hydrocarbon gas GC supplied into the furnace 10 and increasing the carbon potential index value CP in the atmospheric gas in the furnace 10. Note that when the hydrocarbon gas GC is supplied from the hydrocarbon gas guide pipe 13 into the furnace 10, the amount of hydrocarbon gas GC is set to the upper limit, Transmute The gas GR is set to 5 vol% or less, and preferably, an endothermic type Transmute It is set to be 1 vol% or less of the gas GR.

[0035] At this time, endothermic Transmute The amount of gas GR is adjusted to a constant reference amount, which is the minimum amount necessary so that the amount of hydrocarbon gas GC does not exceed the upper limit when the amount of gas GR is adjusted.

[0036] When the amount of hydrocarbon gas GC supplied into the furnace 10 is increased in this manner, and the carbon potential index value CP of the atmospheric gas rises close to the upper limit of the set value, as shown at point b in Figure 2, the control device 17 adjusts the third adjustment valve 13a in the hydrocarbon gas guide pipe 13 to reduce the amount of hydrocarbon gas GC supplied into the furnace 10, thereby reducing the carbon potential index value CP of the atmospheric gas in the furnace 10.When the carbon potential index value CP of the atmospheric gas in the furnace 10 reaches the initial set value, as shown at point c in Figure 2, the amount of hydrocarbon gas GC supplied into the furnace 10 is maintained.

[0037] Furthermore, in this state, if the concentrations of carbon monoxide CO and carbon dioxide CO2 in the atmospheric gas within the furnace 10 change during the heat treatment of the workpiece and the carbon potential index value CP of the atmospheric gas rises close to the upper limit of the set value, as at point d in Figure 2, the third adjustment valve 13a in the hydrocarbon gas guide pipe 13 is adjusted by the control device 17 to reduce the amount of hydrocarbon gas GC supplied into the furnace 10, thereby reducing the carbon potential index value CP of the atmospheric gas within the furnace 10, and when the carbon potential index value CP of the atmospheric gas within the furnace 10 reaches the initial set value, as at point e in Figure 2, the amount of hydrocarbon gas GC supplied into the furnace 10 is maintained.

[0038] Furthermore, if the concentrations of carbon monoxide CO and carbon dioxide CO2 in the atmospheric gas within the furnace 10 change during the heat treatment of the workpiece and the carbon potential index value CP of the atmospheric gas falls close to the lower limit of the set value, as at point f in Figure 2, the control device 17 adjusts the third adjustment valve 13a in the hydrocarbon gas guide pipe 13 to increase the amount of hydrocarbon gas GC supplied into the furnace 10, thereby increasing the carbon potential index value CP of the atmospheric gas within the furnace 10. When the carbon potential index value CP of the atmospheric gas within the furnace 10 reaches the initial set value, as at point g in Figure 2, the amount of hydrocarbon gas GC supplied into the furnace 10 is maintained, thereby maintaining the carbon potential index value CP of the atmospheric gas at the initial set value.

[0039] In this way, the endothermic type Transmute The carbon potential index value CP of the atmospheric gas can be easily adjusted to an appropriate value without changing the amount of gas GR, and the conventional endothermic type Transmute There is no need to enlarge the equipment for producing gas GR, which significantly reduces equipment costs and Transmute The running costs and the like when changing the production amount of gas GR are also reduced.

[0040] In this case, the endothermic Transmute The amount of gas GR is adjusted to a constant reference amount, but if the carbon potential index value CP falls below the lower limit of the specified value even when the hydrocarbon gas GC is increased to the upper limit, the increase in the supply amount of hydrocarbon gas GC is stopped and the amount is kept constant, and the endothermic type Transmute The amount of gas GR may be increased to increase the index value CP of carbon potential.

[0041] In addition, if the carbon potential index value CP rises above the upper limit of the specified value even when the amount of hydrocarbon gas GC is zero, Transmute The amount of gas GR may be reduced to decrease the index value CP of the carbon potential.

[0042] In addition, when the hydrocarbon gas GC is supplied into the furnace 10, the amount of the hydrocarbon gas GC is adjusted to the endothermic type as described above. Transmute Since the concentration is kept below 5 vol% of the gas GR, sooting is prevented from occurring within the furnace 10, and furthermore, the metal catalyst t applied to the inner surface of the furnace 10 promotes the decomposition of the hydrocarbon gas GC, further preventing sooting from occurring.

[0043] In the above embodiment, the carbon potential index value CP [(CO concentration) 2 / (CO2 concentration)] to a set value suitable for heat treatment such as annealing of a workpiece (not shown) such as steel. Transmute The amount of hydrocarbon gas GC supplied into the furnace 10 is adjusted while the amount of gas GR is kept constant, but the method of adjusting the carbon potential index value CP of the atmospheric gas in the furnace 10 to an appropriate set value is not limited to this.

[0044] For example, although not shown, the control device 17 controls the endothermic type Transmute Endothermic type that guides gas GR into furnace 10 Transmute The second adjusting valve 12a provided in the gas guide pipe 12 and the third adjusting valve 13a provided in the hydrocarbon gas guide pipe 13 that guides the hydrocarbon gas GC to the furnace 10 are adjusted to adjust the amount of the hydrocarbon gas GC to the endothermic type. Transmute A constant amount of gas GR is supplied into the furnace 10 so that the amount is low enough to prevent sooting, that is, 5 vol% or less of gas GR. The first adjusting valve 11a provided in the inert gas guide pipe 11 that guides the inert gas GU into the furnace 10 can be controlled by the control device 17 to change the amount of inert gas GU supplied into the furnace 10, thereby adjusting the carbon potential index value CP of the atmospheric gas in the furnace 10 to an appropriate set value.

[0045] In this case, if the amount of inert gas GU supplied into the furnace 10 is increased, the CO concentration and CO2 concentration in the atmospheric gas decrease, but the index value CP of the carbon potential is (CO concentration) 2 It is expressed as / (CO2 concentration), (CO concentration) 2 Since the decrease in the amount of inert gas GU is greater than the decrease in the CO2 concentration, the index value CP of the carbon potential in the atmospheric gas decreases. On the other hand, if the amount of inert gas GU is decreased, the index value CP of the carbon potential in the atmospheric gas increases, in contrast to the above case.

[0046] As mentioned above, the amount of hydrocarbon gas GC is Transmute Even when the amount of inert gas GU supplied into the furnace 10 is changed by the control device 17 as described above while a constant amount of gas GR is supplied into the furnace 10 so that the amount is a low value of 5 vol % or less where sooting does not occur, the amount of endothermic inert gas GU supplied into the furnace 10 is the same as in the case of the above embodiment. Transmute The carbon potential index value CP of the atmospheric gas can be easily adjusted to an appropriate value without changing the amount of gas GR, and the conventional endothermic type Transmute There is no need to enlarge the equipment for producing gas GR, which significantly reduces equipment costs and Transmute The running costs and the like when changing the production amount of gas GR are also reduced. [Explanation of symbols]

[0047] 10: Furnace 11: Inert gas guide tube 11a: First adjusting valve 12: Endothermic type Transmute Gas guide pipe 12a: Second adjusting valve 13: Hydrocarbon gas guide tube 13a: Third adjusting valve 14: Gas supply pipe 1 5: Collection tube 16:CO,CO2 analyzer 17: Control device 18: Exhaust pipe 18a: 4th adjusting valve CP: Carbon potential index value (CO concentration) 2 / (CO2 concentration) GC: Hydrocarbon gas GR: Endothermic type Transmute gas GU: Inert gas t: Metal catalyst

Claims

1. In a heat treatment furnace in which an object to be treated is heat-treated in the furnace using an inert gas containing nitrogen gas as a main component and an endothermic modified gas as the atmospheric gas, the carbon potential index value CP [(CO concentration)] of the atmospheric gas is ２ / (CO ２ A heat treatment furnace characterized in that a hydrocarbon gas is added to adjust the temperature (temperature) of the heat treatment furnace.

2. 2. The heat treatment furnace according to claim 1, wherein a hydrocarbon gas is added to adjust the carbon potential index value CP in the atmospheric gas, thereby suppressing changes in the carbon concentration on the surface of the workpiece during heat treatment.

3. 2. The heat treatment furnace according to claim 1, wherein the amount of said hydrocarbon gas added to the atmospheric gas is set to a specified value or less so that sooting does not occur in the furnace.

4. 4. The heat treatment furnace according to claim 3, wherein the amount of said hydrocarbon gas added to said atmospheric gas is 5 vol % or less of said endothermic converted gas.

5. 4. The heat treatment furnace according to claim 3, wherein the amount of inert gas containing nitrogen gas as a main component in the atmospheric gas is changed while the amount of hydrocarbon gas added to the atmospheric gas is set to be equal to or less than the specified value, thereby adjusting the index value CP of the carbon potential in the atmospheric gas.

6. 6. A heat treatment furnace according to claim 1, 2, 3 or 5, wherein the inner surface of said furnace is coated with a metal catalyst that promotes decomposition of said hydrocarbon gas.

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