JPH0196333A - Continuous annealing furnace provided with gas circulating device - Google Patents

Abstract

PURPOSE:To change the atmospheric gas temp. in each zone in a short time by providing the gas supply pipe and gas discharge pipe capable of controlling a flow rate to the heating zone, cooling zone, and soaking zone, and circulating the gas. CONSTITUTION:The gas supply pipes A1-A3 and the gas discharge pipes B1-B3 are respectively provided to the heating zone 1, soaking zone 2, and cooling zone 3 of a continuous annealing furnace 6, and connected to one circulating header 21. A dust collector 22 is provided to the header 21, as required. Flow control valves C1-C3 and D1-D3 are respectively furnished to the gas supply pipes A1-A3 and the gas discharge pipes B1-B3. When the whole annealing furnace 6 is cooled, the low-temp. gas of the cooling zone 3 is introduced into the heating zone 1 and the soaking zone 2 by opening the valves C1-C3 and D1-D3. As a result, the temp. of the atmospheric gas in each zone is raised or lowered with a simple operation, and the time spent for the heating and cooling of the whole annealing furnace 6 can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a continuous annealing furnace equipped with a gas circulation device.

[Prior Art] Continuous annealing furnaces can obtain predetermined properties of steel strips and the like in a short period of time, and are widely used because of their high production efficiency. This type of continuous annealing furnace is composed of a heating zone 1, a soaking zone 2, and a cooling zone 3, as shown in Fig. 2, and these zones are communicated by a gap 5 necessary for the passage of the steel strip 4. . The entrance and exit of the annealing furnace 6 is sealed with a seal roll or the like. The steel strip 4 enters the heating zone 1, is heated by repeatedly rising and falling by the hearth roll 8, enters the soaking zone 2, and is soaked by rising and falling repeatedly by the reverse roll 8. In the heating zone 1, a direct flame burner or a radiant tube is used as a heat source, and in the soaking zone 2, a radiant tube or an electric heater is provided. Steel strip 4 soaked in soaking furnace 2
enters cooling zone 3. The cooling zone 3 is provided with a gas jet for cooling and an electric heater for temperature adjustment. The steel strip 4 is raised and lowered by hearth rolls, during which time it is cooled by a gas jet and drawn out for the next process. The heating zone 1, the soaking zone 2, and the cooling zone 3 are maintained at a pressure slightly more positive than atmospheric pressure in a reducing gas or non-oxidizing gas atmosphere.

Therefore, gas is supplied to each furnace zone by the amount corresponding to the loss of atmospheric gas.

The annealed steel strip is heat-rolled or leveled to produce products that are used as outer panels for various types of equipment, such as outer panels for automobiles and electrical equipment. Many steel types, plate thicknesses, etc. are used for these, and these steel types and plate thicknesses are usually annealed in one annealing furnace. In this case, in order to bring the temperature of the atmosphere gas in the annealing furnace to the appropriate temperature for the steel type and plate thickness, the temperature in the heating zone, soaking zone, and cooling zone is raised or lowered by operating a heat source such as a radiant tube or electric heater. The temperature of the atmospheric gas is kept at .

In this case, a circulation duct is provided that communicates the front and rear parts of the heating furnace as shown in JP-A-51-141705, and during low-temperature heat treatment, a fan in the circulation duct is driven to remove the atmospheric gas in the furnace. There is a method of operating a heat treatment furnace in which forced stirring is performed and communication in the circulation duct is closed during high-temperature heat treatment. That is, as shown in FIG.
A circulation duct 9 is provided that communicates the front and rear parts of the circulation duct, a fan is disposed within the circulation duct, and dampers 10 and 11 are provided near both ends of the circulation duct 9, respectively. During low-temperature heat treatment of strip material 12 of copper, copper alloy, aluminum, aluminum alloy, etc., the damper 10.11 is set to the "open" state and the fan is driven to rotate the atmospheric gas in the furnace from the front into the circulation duct. The atmospheric gas in the furnace is forcibly agitated by absorbing the gas into the gas and ejecting it into the furnace from the rear part. The circulation duct is closed so that the inside of the furnace does not communicate with the inside of the furnace, and the inside of the furnace is heated to a predetermined high temperature, and the material is heated mainly by radiation. Here, a cooling furnace 16 is provided in connection with the heating furnace 13. 14 is an electric heater,
15 is a transport roll.

[Problems to be Solved by the Invention] However, when changing the atmospheric gas temperature in the heating zone, soaking zone, cooling zone, etc. of an annealing furnace in order to change the standard, steel type, plate thickness, etc., the atmosphere gas temperature in each zone must be changed at the same time. When the gas temperature is adjusted, the temperature increase time or temperature decrease time of the entire annealing furnace is determined by a zone with a low temperature increase rate or a zone with a low cooling equipment capacity. Therefore, there was a problem in that it took a long time to change the temperature of the annealing furnace as a whole. In this case, the above-mentioned Japanese Patent Application Publication No. 5
．． Although the heat treatment furnace shown in No. 1-141705, which is equipped with a circulation duct that communicates the front and rear parts of the heating furnace, is expected to be effective in itself, it is composed of a heating zone, a soaking zone, a cooling zone, etc., and each The above-mentioned problems in an annealing furnace having zones of different temperatures and different thermal inertias have not yet been solved.

In addition, a continuous annealing furnace with a furnace cleaning device with piping for circulation in only one zone is shown in Utility Model Application No. 61-162788, but in this case, a dust removal equipment for the furnace atmosphere gas is also installed. This method attempts to purify the atmosphere within the furnace by circulating it inside the furnace, but it also does not solve the above-mentioned problems.

The present invention has been made to solve the above-mentioned problems, and it shortens the change time for the entire furnace when changing the atmospheric gas temperature in the heating zone, soaking zone, cooling zone, etc. of the annealing furnace at the same time. The purpose of the present invention is to provide a continuous annealing furnace that can perform annealing in hours.

[Means for Solving the Problems] That is, the present invention provides a continuous annealing furnace consisting of a plurality of zones having different thermal inertia, such as a heating zone, a soaking zone, and a cooling zone.
Provide gas supply pipes and gas discharge pipes in each of the soaking zone, cooling zone, etc., connect these gas supply pipes and gas discharge pipes to one circulation main pipe, and connect them to the gas supply pipe and gas discharge pipe. This is a continuous annealing furnace equipped with a gas circulation device equipped with a flow rate adjustment device.

[Function] According to the device of the present invention, a gas supply pipe and a gas discharge pipe are provided in each of the heating zone, soaking zone, cooling zone, etc., and these gas supply pipes and gas discharge pipes are connected to one circulation main pipe. At the same time,
Since the gas supply pipes and gas discharge pipes are equipped with flow rate adjustment devices, when changing the standard, steel type, or plate thickness, the atmospheric gas temperature in the heating zone, soaking zone, cooling zone, etc. can be adjusted accordingly. It can be changed to

1) When increasing the temperature of the cooling zone: Close the gas regulator (hereinafter referred to as the valve) of the gas discharge pipe of the cooling zone, open the valve of the gas supply pipe, and discharge each gas from the heating zone and soaking zone. The valve of the pipe is "open" and the valve of each gas supply pipe is "closed" to allow high temperature gas from the heating zone and soaking zone to flow into the cooling zone to raise the temperature of the cooling zone to a predetermined value.

2) When raising the temperature in the soaking zone: Open the gas discharge pipe and gas supply pipe valves in the soaking zone, open the gas discharge pipe valve in the heating zone, and close the gas supply pipe. The valves of the gas exhaust pipe and gas supply pipe in the cooling zone are closed, and the high-temperature gas in the heating zone is allowed to flow into the soaking zone to raise the temperature of the soaking zone to a specified level.

3) In addition, by combining the opening and closing of the valves of the gas discharge pipes and gas supply pipes in the heating zone, soaking zone, and cooling zone, it is possible to help adjust the temperature in each zone.

[Example] An example of the present invention will be described below based on FIG. The continuous annealing furnace 6 is composed of a heating zone 1, a soaking zone 2, and a cooling zone 3, each of which has gas supply pipes A I and A.
2, A3 and gas exhaust pipes B, , B2. B3 is provided. Those gas supply pipes and gas discharge pipes are connected to one circulation main pipe 21, and these gas supply pipes,
Each gas exhaust pipe has a valve CI.

C2, C3 and D,,D2. D3 is provided.

Although not shown in the heating zone and soaking zone, radiant tubes and electric heaters are provided as heating sources.

The heating zone, soaking zone, and cooling zone are provided with thermometers (not shown) for measuring the atmospheric gas temperature in each zone. In addition, a thermometer is installed in each gas supply pipe and gas discharge pipe.
The temperature of supply gas and exhaust gas can be measured. The circulation main pipe 21 can be provided with a dust removal device 22 if necessary. When a continuous annealing furnace continues to operate for a long time, fine oxidized scales brought in by the steel strip tend to float in each band as dust, so these dusts are removed. An experimental example is shown in which a continuous annealing furnace as shown in FIG. 1 is used, in which the steel plate 4 is annealed by being transferred to a heating zone, a soaking zone, and a cooling zone in this order.

(Experiment Example 1) A steel strip with a thickness of 0.8 mm was heated as shown in Table 1.
We investigated the thermal cycle change time when changing from cycle to B cycle (when cooling zone is the rule).

Table 1 (Unit: °C) In this case, the operation of the device of the present invention in a continuous annealing furnace is to close the valve of the gas discharge pipe in the cooling zone, open the valve of the gas supply pipe, and open the heating zone and soaking zone. The valves of each gas discharge pipe were opened and the valves of each gas supply pipe were closed, and high temperature gas from the heating zone and soaking zone was allowed to flow into the cooling zone to raise the temperature of the cooling zone to a specified level. .

As an experimental result, it took 25 minutes to raise the temperature of the entire annealing furnace to a predetermined temperature, which was 5 minutes shorter than the 30 minutes required in the case of a conventional annealing furnace.

(Experiment Example 2) A steel strip with a thickness of 0.8 mm was heated as shown in Table 2.
We would like to consider the heat cycle change time when changing from cycle to B cycle (assuming the soaking zone is the rule).

Table 2 (Unit: °C) When raising the temperature of the soaking zone as an operation of the device of the present invention: Open the valves of the gas exhaust pipe and gas supply pipe in the soaking zone, and open the valves of the gas exhaust pipe of the heating zone. "Open" and "Close" the gas supply pipe.
and each valve of the cooling zone gas discharge pipe and gas supply pipe is
As a result of the experiment, the temperature of the soaking zone is increased by the specified temperature by flowing high-temperature gas from the heating zone into the soaking zone as "closed". It took 10 minutes for what I did.

In these experimental examples, the number of dummy coils used for changing the thermal cycle was reduced, and the operating rate of the line was improved.

According to the apparatus of the present invention, in addition to the above experimental examples, when a plate breakage occurs during operation and the temperature of the entire annealing furnace must be lowered, low-temperature gas in the cooling zone can be added by operating the valve. By flowing into the tropical and soaking zones, the time it takes for the temperature to cool down can be shortened. In addition, if necessary, the heating zone, soaking zone, and cooling zone can be operated simultaneously or separately by operating the valves of the gas supply pipes and gas exhaust pipes of the heating zone, soaking zone, and cooling zone using a dust removal device installed in the circulation main pipe. According to the device of the present invention, which can remove dust from the cooling zone and remove dust from the cooling zone, the dust concentration in the atmosphere gas of the annealing furnace has been reduced from 0.06 mg/Nrrf to 0.02 mg/Nrrf. It has gained. In addition to the embodiments described above, the apparatus of the present invention can be similarly applied to a case where the cooling zone is composed of a plurality of zones such as a roll cooling zone and a gas cooling zone. It is also applicable to a tempering furnace equipped with a roll cooling zone followed by an electric heater for reheating and a gas cooling function for controlled cooling, or an overaging zone followed by a cooling zone. It is. Furthermore, when the heating zone is a direct-fired furnace using non-oxidizing burners for rapid heating or a direct-fired furnace using reducing burners, the atmosphere is different, so a method may be adopted in which the atmospheric gas is exchanged after the soaking zone. The present invention can be similarly applied to a case where a preheating zone that performs preheating using the exhaust gas from the heating zone or soaking zone is disposed in front of the heating zone. In this case, when the preheating zone utilizes the atmosphere of the open heating zone, it should be applied separately into the preheating zone ~ heating zone system, and the soaking zone (including if it has an adjustment heating zone) ~ cooling zone. When the length of the gas supply pipe and the gas discharge pipe are long, as in the embodiment of the present invention, heating zone, soaking zone, cooling zone and secondary cooling zone, tempering furnace or overaging zone, cooling zone, etc. This device may be applied by dividing the zone. If part of the cooling zone uses liquid (e.g. water, hot water, etc.) and the atmosphere is different, this device can be applied by dividing the zone. Should.

[Effects of the Invention] According to the apparatus of the present invention, gas supply pipes and gas discharge pipes are provided in the heating zone, soaking zone, cooling zone, etc. of the existing annealing furnace, respectively.
By connecting them to the circulation main pipe and installing a gas amount adjustment device in each gas supply pipe and gas discharge pipe, the temperature of the atmospheric gas in multiple zones can be assisted by simple operation, and the whole annealing furnace can be heated. This is an industrially valuable invention because it can shorten the time required to raise and lower the temperature.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of the present invention, FIG. 2 is a schematic diagram of a conventional continuous annealing furnace, and FIG. 3 is a conventional heat treatment furnace having a circulation duct. 21... Circulation main pipe 22... Dust removal device A I
, A2, A I...-Gas supply pipe for heating zone, soaking zone, and cooling zone, B,, B2. B3...Gas exhaust pipes in the heating zone, soaking zone, and cooling zone, c,, c 2. c3... Flow rate adjustment device for gas supply pipes in the heating zone, soaking zone, and cooling zone, D,, D2. D3: Flow rate adjustment device for gas discharge pipes in the heating zone, soaking zone, and cooling zone.

Claims (1)

[Claims] In a continuous annealing furnace consisting of a plurality of zones with different thermal inertia, such as a heating zone, a soaking zone, and a cooling zone, a gas supply pipe and a gas discharge pipe are provided in each of the heating zone, soaking zone, cooling zone, etc. A continuous annealing furnace equipped with a gas circulation device, characterized in that a supply pipe and a gas discharge pipe are connected to one circulation main pipe, and a flow rate adjustment device is provided in the gas supply pipe and gas discharge pipe.