JP6332957B2 - Atmosphere control method for continuous steel tube annealing furnace - Google Patents

Description

  The present invention relates to an atmosphere control method for a continuous steel pipe annealing furnace. When steel pipes are annealed continuously, using a continuous annealing furnace equipped with a front chamber, heating chamber, cooling chamber, and rear chamber, the steel pipe is continuously charged into and discharged from the furnace. Annealing treatment is performed under a controlled atmosphere. For controlling the atmosphere, exothermic gas (DX gas), purified exothermic gas (NX gas), endothermic gas (RX gas), and the like are used, and the present invention continuously uses endothermic gas among these. The present invention relates to an improvement in the atmosphere control method of a steel pipe annealing furnace.

Conventionally, as an atmosphere control method for an annealing furnace using an endothermic gas, the carbon potential determined from the CO concentration and the CO ₂ concentration of the atmosphere is the carbon potential required according to the material to be treated. While controlling the supply amount of gas into the furnace, raw material gas, air, nitrogen gas and the like are supplied into the furnace as necessary (see, for example, Patent Documents 1 to 3).

  However, these conventional methods have a corresponding advantage when the annealing furnace is of a batch type, but the annealing furnace has a continuous type in which its inlet and outlet are always open during processing. 1) Since the carbon potential of the atmosphere is maintained at the set value by controlling the supply amount of the endothermic gas under a situation where the atmospheric gas continues to leak from the furnace, the endothermic gas generator It is necessary to provide a reasonable margin, and the cost increases accordingly. 2) In addition, depending on the carbon potential of the atmosphere, depending on the case, raw gas (raw gas) such as propane and butane, air, nitrogen gas, etc. Since it is necessary to control the supply amount as well, the control system and control operation become complicated accordingly. 3) In addition, when supplying raw material gas and air, the reaction by them is sufficiently performed. Only when the furnace is higher than about 800 to 850 ° C., there is a problem that.

JP-A-2005-76109 JP 2005-76986 A JP 2010-132997 A

  The problem to be solved by the present invention is to provide an atmosphere control method for a continuous steel pipe annealing furnace that can control the carbon potential of the furnace atmosphere at a low cost with a simple control system.

The present invention for solving the above-mentioned problems is an atmosphere control method for a continuous steel pipe annealing furnace having a front chamber, a heating chamber, a cooling chamber, and a rear chamber, wherein the heating chamber has an upstream heating zone and a downstream soaking. The endothermic gas generator is connected to the heating zone of the heating chamber , and an analyzer for CO concentration and CO ₂ concentration is connected to the soaking zone of the heating chamber. Only the endothermic gas generated by the endothermic gas generator is supplied to the heating zone, and the carbon potential of the endothermic gas is calculated by calculating from the CO concentration and the CO ₂ concentration. The present invention relates to an atmosphere control method for a continuous steel pipe annealing furnace, characterized in that it is adjusted to a value 1.0 to 1.7 times higher than the set value of the carbon potential of the atmosphere in the zone. The present invention is also an atmosphere control method of a continuous steel pipe annealing furnace having a front chamber, a heating chamber, a cooling chamber, and a rear chamber, wherein the heating chamber is formed by an upstream heating zone and a downstream soaking zone. An endothermic gas generator is connected to the heating zone of the heating chamber , an analyzer for CO concentration and CO ₂ concentration is connected to the soaking zone of the heating chamber, and an arithmetic unit is connected to the analyzer. In connection with the atmosphere control, only the endothermic gas generated by the endothermic gas generator is supplied to the heating zone of the heating chamber, and the arithmetic unit calculates the CO concentration and CO ₂ concentration measured by the analyzer. in carbon potential of the atmosphere in the soaking zone of the heating chamber to be calculated, so that a setting value set in advance in the computing device, the signal issued from the arithmetic unit, the endothermic shape gas generator of air及BiHara material gas supply Adjusting the, or a, characterized in that depending on the fluctuation range of the carbon potential of the atmosphere in the soaking zone of the heating chamber, to adjust only the amount of air within the air and the raw material gas to be supplied to the endothermic type gas generator The present invention relates to an atmosphere control method for a continuous steel pipe annealing furnace.

  In the atmosphere control method according to the present invention, it is a continuous steel pipe annealing furnace that is controlled by the atmosphere. The continuous steel pipe annealing furnace includes a front chamber, a heating chamber, a cooling chamber, and a rear chamber, and the heating chamber is formed by an upstream heating zone and a downstream soaking zone, and continuously treats the workpiece. Annealing is performed in a controlled atmosphere while transporting in the furnace.

  In the atmosphere control method according to the present invention, an endothermic gas generator is connected to an appropriate zone of the heating chamber, usually the heating chamber, and only the endothermic gas generated by the endothermic gas generator is used for the atmosphere control. To the appropriate zone. The raw material gas, air, nitrogen gas or the like is not supplied into the furnace as in the conventional method.

  In the atmosphere control method according to the present invention, the carbon potential of the endothermic gas supplied to the heating chamber, usually to an appropriate zone of the heating chamber, is set to be 1. below the set value of the carbon potential of the atmosphere in the soaking zone of the heating chamber. Adjust to 0-1.7 times higher value. The carbon potential of the atmosphere in the heating zone of the heating chamber is affected by the amount of oxygen in the material to be treated brought into the heating chamber, and specifically, it is affected by the degree of oxidation, degreasing, inner and outer diameters, etc. of the material to be treated. The carbon potential of the endothermic gas to be supplied to the heating chamber, usually the heating zone of the heating chamber, is determined based on the measured experience value according to the actual state of the material to be processed so that the carbon potential becomes a set value. The value is adjusted to 1.0 to 1.7 times higher than the set value. The endothermic gas generator is connected to a source gas supply system and an air supply system, and the carbon potential of the generated endothermic gas increases as the amount of source gas supplied is relatively increased. If the supply amount of air is increased, the flow rate becomes lower. Therefore, the adjustment can be made by controlling both supply amounts.

In the atmosphere control method according to the present invention, an endothermic gas generator is connected to an appropriate zone of a heating chamber, usually a heating chamber, and an ambient gas is sampled in a soaking zone of the heating chamber to obtain a CO concentration and a CO ₂ concentration. The analyzer is connected to the analyzer, and an arithmetic unit is connected to the analyzer. For the atmosphere control, only the endothermic gas generated by the endothermic gas generator is heated in the heating chamber, usually the appropriate zone of the heating chamber. Can be supplied to.

In such an atmosphere control method, the carbon potential of the atmosphere in the soaking zone of the heating chamber calculated by the arithmetic device from the CO concentration and CO ₂ concentration measured by the analyzer becomes a preset value set in the arithmetic device. As described above, the amount of air and / or source gas supplied to the endothermic gas generator is adjusted by a signal generated from the arithmetic unit.

In the atmosphere control method, the carbon potential of the atmosphere in the soaking zone of the heating chamber calculated by the arithmetic device from the CO concentration and CO ₂ concentration measured by the analyzer is the preset value set in the arithmetic device. Thus, it is preferable to adjust only the amount of air among the air and the raw material gas supplied to the endothermic gas generator by a signal generated from the arithmetic unit. This is because the amount of air supplied to the endothermic gas generator is several times larger than the amount of the raw material gas, and therefore it is easier to control by adjusting the amount of air.

  In the atmosphere control method for adjusting only the amount of air supplied to the endothermic gas generator, only the amount of air corresponding to 1 to 30% by volume is adjusted out of the total amount of air supplied to the endothermic gas generator. It is preferable. In a continuous steel tube annealing furnace, when the carbon potential of the atmosphere in the soaking zone of the heating chamber is controlled to be a set value, the amount of fluctuation of air supplied to the endothermic gas generator is about 1 to 30% by volume of the whole. This is because it is sufficient to adjust only the amount of air corresponding to 1 to 30% by volume of the air supplied to the endothermic gas generator, and this is because the control accuracy is better.

In the atmosphere control method according to the present invention described above, the carbon potential of the atmosphere in the soaking zone of the heating chamber calculated by the arithmetic device from the CO concentration and CO ₂ concentration measured by the analyzer is preset in the arithmetic device. When adjusting the amount of air to be supplied to the endothermic gas generator by a signal generated from the arithmetic unit so that the set value is set, the endotherm is adjusted according to the fluctuation range of the carbon potential of the atmosphere in the soaking zone of the heating chamber. It is preferable to set a certain time difference between the operation of adjusting the amount of air supplied to the gas generator and the operation of measuring the CO concentration and CO ₂ concentration of the atmosphere in the soaking zone of the heating chamber. The heating chamber has a large capacity, and the influence of the operation for adjusting the amount of air supplied to the endothermic gas generator is reflected in the CO concentration and CO ₂ concentration of the atmosphere in the soaking zone of the heating chamber by a certain time difference. That is, because a certain time delay occurs, the time delay required between both operations is expected to improve the control accuracy.

  According to the atmosphere control method of the present invention, the carbon potential in the furnace atmosphere of a continuous steel pipe annealing furnace can be controlled at a low cost with a simple control system.

The block diagram which illustrates one embodiment of the atmosphere control method concerning the present invention. The block diagram which illustrates other one embodiment of the atmosphere control method concerning the present invention. The block diagram which illustrates other one embodiment of the atmosphere control method concerning the present invention. The block diagram which illustrates other one embodiment of the atmosphere control method concerning the present invention.

  FIG. 1 is a block diagram showing an embodiment of an atmosphere control method according to the present invention. In FIG. 1, the continuous steel pipe annealing furnace 11 is the target of the atmosphere control. The continuous steel pipe annealing furnace 11 includes a front chamber 21, a heating chamber 31, a cooling chamber 41, and a rear chamber 51. The heating chamber 31 is formed of an upstream heating zone 31a and a downstream soaking zone 31b. The steel pipe as the material to be treated is annealed in a controlled atmosphere while being continuously conveyed in the furnace. In FIG. 1, an endothermic gas generator 61 is connected to the heating zone 31 a of the heating chamber 31, an analyzer 71 is connected to the soaking zone 31 b of the heating chamber 31, and an electric valve is connected to the endothermic gas generator 61. The source gas supply system interposing 91a and the air supply system interposing the motor operated valve 91b are connected, and only the endothermic gas generated by the endothermic gas generator 61 is heated in the heating chamber 31 for atmosphere control. Supplying to the zone 31a. In FIG. 1, the carbon potential of the endothermic gas supplied to the heating zone 31 a of the heating chamber 31 is adjusted by adjusting the opening degree of the motorized valves 91 a and 91 b, and the carbon potential of the atmosphere in the soaking zone 31 b of the heating chamber 31. The value is adjusted to 1.0 to 1.7 times higher than the set value.

According to the implementation state described above with reference to FIG. 1, the steel pipes shown in Table 1 were continuously annealed under the conditions shown in Table 1. The result of the carbon potential (set value) obtained by calculation from the CO concentration and the CO ₂ concentration measured by the analyzer 71, and the result of the carbon potential of the endothermic gas supplied from the endothermic gas generator 61 at that time, Table 1 summarizes the results.

FIG. 2 is a block diagram showing another implementation state of the atmosphere control method according to the present invention. Since the continuous steel pipe heat treatment furnace 12 itself is the same as that shown in FIG. In FIG. 2, an endothermic gas generator 62 is connected to the heating zone 32 a of the heating chamber 32, and the analyzer 72 measures the CO concentration and the CO ₂ concentration by sampling the atmospheric gas in the soaking zone 32 b of the heating chamber 32. Is connected to the analyzer 72, and only the endothermic gas generated by the endothermic gas generator 62 is supplied to the heating zone 32a of the heating chamber 32 for atmosphere control. In FIG. 2, the carbon potential of the atmosphere in the soaking zone 32b of the heating chamber 32 calculated by the arithmetic device 82 from the CO concentration and CO ₂ concentration measured by the analyzer 72 is set in the arithmetic device 82 in advance. The amounts of air and raw material gas supplied to the endothermic gas generator 62 are adjusted by adjusting the opening degree of the motor-operated valves 92b and 92a by a signal generated from the arithmetic unit 82 so as to be a value.

FIG. 3 is a block diagram showing another implementation state of the atmosphere control method according to the present invention. Since the continuous steel pipe heat treatment furnace 13 itself is the same as that shown in FIG. In FIG. 3, the carbon potential of the atmosphere in the soaking zone 33 _{b of the} heating chamber 33 calculated by the calculation device 83 from the CO concentration and the CO ₂ concentration measured by the analyzer 73 is set in advance in the calculation device 83. The opening degree of the motor-operated valve 93b is adjusted by a signal generated from the arithmetic unit 83 so as to be a value, and only the amount of air among the air and the raw material gas supplied to the endothermic gas generator 63 is adjusted.

FIG. 4 is a block diagram showing another implementation state of the atmosphere control method according to the present invention. The continuous steel pipe heat treatment furnace 14 itself is the same as that shown in FIG. In FIG. 4, the carbon potential of the atmosphere in the soaking zone 34 b of the heating chamber 34 calculated by the calculation device 84 from the CO concentration and the CO ₂ concentration measured by the analyzer 74 is set in advance in the calculation device 84. The opening degree of the motor-operated valve 93c interposed in the bypass of the air supply system to the endothermic gas generator 63 is adjusted by a signal generated from the arithmetic unit 84 so that the endothermic gas generator 64 has a value. Of the supplied air and source gas, only the amount of air corresponding to 1 to 30% by volume of the total amount of air is adjusted.

11-14 Continuous steel pipe annealing furnace 21-24 Front chamber 31-34 Heating chamber 31a-34a Heating zone 31b-34b Soaking zone 41-42 Cooling chamber 51-54 Rear chamber 61-64 Endothermic gas generator 71-74 Analyzer 82 to 84 Arithmetic unit 91a to 94a, 91b to 94b, 94c Motorized valve

Claims (5)

An atmosphere control method for a continuous steel pipe annealing furnace including a front chamber, a heating chamber, a cooling chamber, and a rear chamber, wherein the heating chamber is formed by an upstream heating zone and a downstream soaking zone, An endothermic gas generator was connected to the heating zone, and an analyzer of CO concentration and CO ₂ concentration was connected to the soaking zone of the heating chamber , and the endothermic gas generator was used to control the atmosphere. While supplying only the endothermic gas to the heating zone, the carbon potential of the endothermic gas is calculated from the set value of the carbon potential of the atmosphere in the soaking zone of the heating chamber calculated from the CO concentration and the CO ₂ concentration. Is also adjusted to a value 1.0 to 1.7 times higher, and an atmosphere control method for a continuous steel pipe annealing furnace. An atmosphere control method for a continuous steel pipe annealing furnace including a front chamber, a heating chamber, a cooling chamber, and a rear chamber, wherein the heating chamber is formed by an upstream heating zone and a downstream soaking zone, An endothermic gas generator is connected to the heating zone, a CO concentration analyzer and a CO ₂ analyzer are connected to the soaking zone of the heating chamber, and an arithmetic unit is connected to the analyzer to connect the atmosphere. For control, only the endothermic gas generated by the endothermic gas generator is supplied to the heating zone of the heating chamber, and the calculation unit calculates the CO concentration and CO ₂ concentration measured by the analyzer. carbon potential of the atmosphere in the soaking zone of the heating chamber, so that a setting value set in advance in the arithmetic unit, air及BiHara supplied by a signal emanating from the computing device to the endothermic shape gas generator Adjusting the amount of gas Atmosphere control method for continuous steel annealing furnace, characterized. An atmosphere control method for a continuous steel pipe annealing furnace including a front chamber, a heating chamber, a cooling chamber, and a rear chamber, wherein the heating chamber is formed by an upstream heating zone and a downstream soaking zone, An endothermic gas generator is connected to the heating zone, a CO concentration analyzer and a CO ₂ analyzer are connected to the soaking zone of the heating chamber, and an arithmetic unit is connected to the analyzer to connect the atmosphere. For the control, only the endothermic gas generated by the endothermic gas generator is supplied to the heating zone of the heating chamber, and the heating chamber is calculated by the arithmetic unit from the CO concentration and CO ₂ concentration measured by the analyzer. The fluctuation range of the carbon potential of the atmosphere in the soaking zone of the heating chamber is determined by a signal generated from the computing device so that the carbon potential of the atmosphere in the soaking zone becomes the set value preset in the computing device. According to Te, the atmosphere control method for continuous expression steel annealing furnace you adjust only the amount of air within the air and the raw material gas to be supplied to the endothermic type gas generator.   The atmosphere control method for a continuous steel pipe annealing furnace according to claim 3, wherein only the amount of air corresponding to 1 to 30% by volume of the air supplied to the endothermic gas generator is adjusted. Claim for setting operations and to adjust the amount of air supplied to the intake heat form the gas generator, between the operation of measuring the CO concentration and the CO ₂ concentration in the atmosphere in the soaking zone of the heating chamber, a constant time difference 3. An atmosphere control method for a continuous steel pipe annealing furnace according to 3 or 4.

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