JP2829148B2 - Atmosphere flow control device and control method in continuous annealing furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for controlling an atmosphere flow in a continuous annealing furnace.

[0002]

2. Description of the Related Art For example, a continuous annealing furnace for a strip includes a heating zone, a soaking zone, and a cooling zone connected in series, and a heating zone, a decarburization zone, a reduction zone, and a cooling zone connected in series. .
In each zone, a desired atmosphere gas is set, and continuous annealing or continuous decarburizing annealing is performed.

[0003] When continuously annealing strips requiring particularly strict control of the surface properties, strips requiring decarburization, and strips requiring control of an oxide layer on the surface of a steel sheet, for example, a heating zone, Each zone of the decarburization zone and the reduction zone must have a predetermined atmosphere, for example, a dew point is maintained in a specific range, and a specific component in the atmosphere gas composition is always kept at a constant concentration. is there.

[0004] Therefore, it has been proposed to provide an atmosphere partition at the boundary of each zone in the continuous annealing furnace to prevent mixing of the atmosphere gas in the furnace. For example, in Japanese Patent Application Laid-Open No. 63-24038, a seal box provided at a zone boundary is provided with a seal body capable of moving up and down opposite to a transport roll, and the seal body is brought into contact with a strip plate surface to seal between zones. I have. Although the atmosphere partition suppresses the atmosphere mixing between the zones, the fact is that the mixing still occurs due to the deterioration of the seal roll and the like with the passage of time and the complete prevention cannot be performed.

[0005] In the continuous annealing, the dew point of the atmosphere gas in the furnace is controlled. For example, in Japanese Patent Application Laid-Open No. 2-80511, a mixing ratio of a humidifying gas and a dry gas is determined from a total flow rate set value of a mixed gas obtained by mixing a humidified gas and a dry gas, a dew point temperature thereof, and a dew point set value of a furnace atmosphere gas. It has been proposed to control the dew point of the atmosphere gas in the furnace by controlling the flow rate of each gas. According to this, it is said that the control of the dew point is accurately performed, which is effective.

[0006]

The setting of the atmosphere partition and the control of the dew point have a certain effect on the control of the furnace atmosphere. However, when the strip is continuously annealed, the decarburization is less than the strip position. In some cases, the thickness of the oxidized layer formed on the strip may be insufficient, and the thickness of the oxidized layer may be insufficient or the amount of oxidation may be insufficient or excessive. Since such a phenomenon greatly affects the quality or surface properties of a product plate and a subsequently formed surface coating, it is necessary to prevent the occurrence of such a phenomenon.
An object of the present invention is to form, for example, a uniform oxide layer on a strip to be annealed, over the entire plate, and to perform continuous annealing in which defects due to decarburization positions do not occur.

[0007]

Means for Solving the Problems The inventors of the present invention have studied to make the decarburization, the formation of the oxide layer, and the uniformity of the surface properties and the like in the continuous annealing, and found that the flow of the atmosphere gas in the furnace has a great effect. It was found that the flow of the atmosphere gas in the zone should be kept constant. The present invention is based on this finding, and the gist of the present invention is to control the atmosphere flow in a continuous annealing furnace provided with a plurality of zones partitioned by an atmosphere partition, and to inject a galvanic gas into the zone. , A device for detecting the concentration of a galvanic gas mixed with the exhaust gas discharged from the atmosphere partition between the front and rear adjacent zones of the zone, an atmosphere supply gas amount detector for the zone, and injection into the zone. Enter the detection gas volume, the detection value from the detection gas concentration detector in the front part of the zone, and the detection value of the detection gas concentration detector from the atmosphere partition part in the rear adjacent zone, and enter the pre-flow and post-flow in the zone. A device for calculating the atmospheric flow rate,
An atmosphere flow control device in a continuous annealing furnace, comprising: a device for comparing a difference and an allowable value between the atmosphere upstream flow rate and the downstream flow rate from the arithmetic unit and controlling the furnace atmosphere gas flow; and In the control method.

Hereinafter, the present invention will be described in detail based on an embodiment with reference to the drawings. In the drawing, 1 is a continuous annealing furnace, which in this embodiment is a heating zone 2, a soaking zone 3,
A slow cooling zone 4 and a cooling zone 5 are provided. The atmosphere partition 6 is located between the solitary zone 3 and the slow cooling zone 4, and between the slow cooling zone 4 and the cooling zone 5.
And partition the atmosphere gas in the zone.

Reference numeral 7 denotes an atmosphere gas supply device, which is provided in each zone partitioned by the atmosphere partition 6.
Reference numeral 8 denotes an atmosphere outlet provided at the front of the heating zone 2,
In this embodiment, since the heating zone 2 is the foremost part of the continuous annealing furnace 1, there is no atmosphere partition at the front part, and an atmosphere discharge port 8 is provided instead. Reference numeral 9 denotes a partition atmosphere discharge port provided in the atmosphere partition 6. These are provided with opening / closing regulators 10, respectively, for controlling the degree of opening / closing of the exhaust port and controlling the discharge flow rate.

Reference numeral 11 denotes a galvanic gas supply device for supplying a galvanic gas, for example, He or the like which does not react with a strip or other gas, in order to detect a flow of the atmosphere gas in the furnace. The galvanic gas supply device 11 is an example in which the present embodiment is provided in the soaking zone 3 and the slow cooling zone 4, and the installation can be performed in any zone.

Reference numeral 12 denotes a device for detecting the concentration of a galvanic gas mixed with the atmosphere discharged from the atmosphere discharge port 8 at the front of the heating zone 2, and employs, for example, a mass spectrometer. Reference numeral 12a denotes a galvanic gas concentration detecting device which mixes with the atmosphere flowing out from the partition atmosphere discharge port 9.

Numeral 13 denotes an arithmetic unit for calculating the flow rate of the upstream and downstream flows of the atmospheric gas in the furnace and controlling the atmospheric flow. In this embodiment, the arithmetic unit 13 is located within the heating zone 2 and the soaking zone 3 from the galvanic gas supply device 11. From the total gas amount V _T injected or the flow rate of the detected gas V _HE and the detected gas concentration C ₁ of the exhaust gas from the front of the heating zone from the detected gas concentration detector 12, the atmosphere in the upstream of the zone is determined. Flow rate V ₁ and after-flow atmosphere flow rate V
₂ is calculated by the following equation (1), and the total gas amount V _T or the galvanic gas flow rate V _HE and the atmosphere of the partition between the isotropy zone 3 and the slow cooling zone 4 from the galvanic gas concentration detecting device 12a. From the detected gas concentration C _{2 at the} discharge port 9, the after-flow atmosphere flow rate V ₂ and the before-flow atmosphere flow rate V ₁ are calculated by the following equation (2). _{V 1 = (V HE / C} 1) -V HE, V 2 = V T -V 1 ······ (1) V 2 = (V HE / C 2) -V HE, V 1 = V T −V ₂ (2) Next, the flow rate of the upstream flow rate V ₁ is compared with the flow rate of the downstream flow rate V _2, and the difference is compared with an allowable value obtained by setting or learning. An opening / closing control signal for the outlet 8 and the partition atmosphere outlet 9 is output. The opening / closing degree of the opening / closing regulator 10 is controlled by the opening / closing control signal, and in the present embodiment, all the atmosphere flows in the heating / uniform tropics 2 and 3 are directed to the front side of the heating zone.

Next, the control method will be described. The strip is passed through the continuous annealing furnace 1 from the heating zone 2 side, travels in the direction of the arrow, and is annealed. In this embodiment, the heating zone 2 and the soaking zone 3 are supplied with a humid gas such as H ₂ , N ₂ and the strip is decarburized, and the strip has an oxide layer on the plate surface. In the slow cooling zone 4, cooling is performed by the dry gas and a reducing action to the oxide layer is performed.

By the way, the atmosphere gas flow in the furnace, in this embodiment, is made as follows so as to be unidirectional. The galvanic gas He is injected into the continuous heating zone 2 and the soaking zone 3, and the galvanic gas He is not injected into the slow cooling zone 4. At this time, the heating zone 2 and the soaking zone 3 are supplied with wet gas, and the slow cooling zone 4 is supplied with dry gas, and the atmosphere partition 6 is closed. The atmosphere gas in the furnace flowing from the soaking zone 3 to the front side of the heating zone flows out of the furnace from the atmosphere discharge port 8, and the galvanic gas concentration C ₁ in the gas is detected by the galvanic gas concentration detection device 12.

On the other hand, the atmosphere partition 6 at the boundary with the slow cooling zone 4
Galvanometric gas concentration C ₂ of the atmospheric gas flowing in the side is detected by galvanometric gas concentration detecting device 12a. Further, the amount V _HE of the galvanic gas He injected into the heating zone 2 and the soaking zone 3 is known from the galvanic gas supply device 11.

[0016] The galvanometer gas concentration detection value C _1, C ₂ and galvanometric gas V _HE is input to the arithmetic unit 13, the arithmetic of the equation is made, the pre-flow atmosphere flow rate V ₁ of the in the band 2,3 Compare the after-flow atmosphere flow rate V ₂ and compare the difference value with a predetermined allowable value or an allowable value to be learned. If the difference value is large, the after-flow of the atmosphere is large, which is not preferable for the strip to be annealed. Then, the degree of closure of the atmosphere partition 6 is increased to reduce the after-flow and make it as forward as possible.

By doing so, the atmosphere gas flow in the heating zone 2 and the soaking zone 3 becomes a pre-flow, and the strip to be annealed is uniformly decarburized and an oxide layer is formed. When controlling the atmosphere gas flow in the slow cooling zone 4, a galvanic gas is injected into the slow cooling zone 4, while a galvanic gas is not injected into the adjacent solitary zone 3 and the cooling zone 5. Is performed in the same manner as described above.

[0018]

As described above, according to the present invention, the flow of the atmosphere gas in the furnace in the continuous annealing furnace can be controlled, and particularly the flow direction can be made constant.
Oxide layer formation, reduction, etc. are performed stably.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of the present invention. DESCRIPTION OF SYMBOLS 1 Continuous annealing furnace 2 Heating zone 3 Uniform tropical zone 4 Slow cooling zone 5 Cooling zone 6 Atmosphere partition 7 Atmospheric gas supply device 8 Atmospheric discharge port 9 Partition section atmosphere discharge port 10 Opening / closing regulator 11 Detector gas supply device 12 Detector gas concentration Detector 12a Galvanic gas concentration detector 13 Arithmetic unit

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yoichi Zaimae 1-1, Hibata-cho, Tobata-ku, Kitakyushu-shi, Fukuoka Nippon Steel Corporation Yawata Works (56) References JP-A-2-236229 (JP, A) JP-A-62-250129 (JP, A) JP-A-57-63641 (JP, A) JP-A-53-22131 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) ) C21D 1 / 74,1 / 76,9 / 52,9 / 56

Claims (2)

(57) [Claims] 1. A device for providing a plurality of zones partitioned by an atmosphere partition and controlling an atmosphere flow in a furnace in a continuous annealing furnace to which an atmosphere gas is supplied, wherein: a device for injecting a galvanic gas into the zone; A device for detecting the concentration of the galvanic gas mixed with the exhaust gas discharged from the atmosphere partitioning portion between the front and rear adjacent zones, an atmosphere supply gas amount detector for the zone, and an amount of the gas to be injected into the zone. The detection value from the galvanic gas concentration detector in the front part of the zone and the detection value from the galvanic gas concentration detector from the atmosphere partition part in the rear adjacent zone are input to calculate the upstream and downstream atmosphere flow rates in the zone. Equipment and
An atmosphere flow control device for a continuous annealing furnace, comprising: a device for comparing a difference between an upstream flow rate and a downstream flow rate of the atmosphere from the arithmetic unit and an allowable value to control the atmosphere gas flow in the furnace. 2. In controlling a furnace atmosphere flow in a continuous annealing furnace provided with a plurality of zones partitioned by an atmosphere partition, a test gas is injected into the zone in a separate system or together with an atmosphere gas supply, The concentration of the galvanic gas flowing out of the front and the concentration of the galvanic gas flowing out of the atmosphere partition between the rear adjacent zone are detected, respectively, and the detected values of the galvanic gas concentrations at the front and rear and the amount of the galvanic gas supplied to the band are detected. Calculates the upstream flow rate and the downstream flow rate of the atmosphere in the zone, compares the difference value with the set or learned allowable value, and controls the degree of opening and closing of the atmosphere outlet at the front or rear of the zone according to the magnitude. Atmosphere flow control method in a continuous annealing furnace characterized by the above-mentioned.