JPS61113727A - Heating device of metallic strip continuous annealing furnace - Google Patents

Abstract

PURPOSE:To obtain a titled heating device for controlling quickly a heating temperature in accordance with a variation of a heat load quantity by constituting it so that a gas jet device is provided extending from an appropriate area of the rear part of a heating zone to a heating area, and a gas for controlling a plate temperature is jetted to a metallic strip. CONSTITUTION:In a heating zone 14 and a soaking zone 15 of a metallic strip continuous annealing furnace, a gas jet device consisting of many radiant tubes 19, and plenum chambers 21 being adjacent to said tubes is provided as a heating device for heating a metallic strip 11 which runs through the inside of said furnace. As for said gas jet device, its front end part becomes the front end of the rear area of said heating zone 14 corresponding to 20-30% of a heat load variation quantity, and on the other hand, its rear end part is provided extending over the last part of the heating area, or on the whole of the soaking zone 15. When annealing the metallic strip 11, a plate temperature is controlled quickly by jetting a gas which has been set to the necessary temperature and flow rate, to the metallic strip 11, in accordance with a setting change of a heat cycle, a line speed, a plate thickness, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Field> The present invention relates to a heating device in a continuous annealing furnace for metal strip.

<Prior Art 2> Traditionally, metal strips such as cold-rolled steel sheets and tin plates are continuously heat-treated in a continuous annealing furnace to impart desired mechanical properties. FIG. 6 shows a schematic diagram of an example of the overall construction of this continuous annealing furnace. , is supplied to the continuous annealing furnace 12, and is rotated between a large number of helper rolls 130 provided at the upper and lower parts of the continuous annealing furnace 12, meandering in the vertical direction according to the mechanical properties required for the product. The material is then subjected to the necessary heating and cooling, and is finally given the required mechanical properties as a material, such as yield strength, tensile strength, deep drawability, and aging resistance, at room temperature. The continuous annealing furnace 12 includes, in order from the inlet side to the outlet side of the metal strip 110, a heating zone 14, a soaking zone 15, a quenching zone 16, an overaging zone 17,
A final cooling zone 18 is provided. A heating zone consisting of a heating zone 14 and a soaking zone 15 is equipped with a lasoant tube 19.
is provided, and the metal strip 11' passing through it is heated by radiation heating, and the metal strip 11 is heated from room temperature to 650 to 900°C in the heating zone 14.
Then, in the subsequent soaking zone 15, that temperature is maintained or it is further heated slightly. Subsequently, the metal strip 11 that has left the heating zone is rapidly cooled to about 400° C. in a quenching zone 16 following the soaking zone 15 by means such as a gas soet or a cooling roll (not shown).
7, the temperature is maintained, and finally the final cooling zone 18
It is cooled down to near room temperature.

<Problems to be solved by the invention> In recent years, with the demand for high-mix, low-volume production, various metal strips with different thicknesses and widths have been continuously subjected to different heat cycles depending on the required mechanical properties. There is a need for a continuous annealing furnace that can perform continuous annealing. However, in conventional continuous annealing furnaces that use the radiant tube method for heating, the time constant of the radiant tube temperature is as long as 5 to 10 minutes, so the heating temperature cannot be adjusted quickly in response to changes in the heat cycle required for the metal strip. The problem is that it cannot be controlled. That is, for example, when processing thicker metal strips in succession with respect to the preceding pot metal strip, it is necessary to raise the temperature of the radiant tube when the thicker metal strips with larger heat capacities pass through. However, even if you increase the combustion rate of the radiant tube burner, the metal strip will not quickly reach the required temperature. On the other hand, if the threading speed of the line is not changed until the leading thin metal strip leaves the continuous annealing furnace, the tip of the trailing thick metal strip may be
This results in a very long under-annealed part, which can be as long as 0.00 m. Also, if the line speed is reduced as much as necessary to allow the trailing thicker metal strip to reach the required temperature, the leading thinner metal strip will heat up too much and become over-annealed, resulting in a general The required mechanical properties are softened. speed to this intermediate level
If it is changed in this way, the leading plate will become softer, and the trailing plate will have parts that are insufficiently annealed. On the other hand, if the plate thickness becomes thinner in the middle, the opposite development occurs.

In the past, products that generally exceeded the required mechanical properties, for example, were made softer, were rather welcomed by consumers from the viewpoint of ease of processing. However, with the recent automation of the plastic working process of metal plates, this is not necessarily something that should be welcomed, and it is better to make the material of the target hole uniform.
It has become important. Therefore, no matter how the speed is changed, it is no longer possible to deal with the above-mentioned operation method, which causes material abnormalities of considerable length at the joints of the metal strips.

Therefore, in order to avoid the above-mentioned problem at the plate thickness change section, expedient methods are used, such as inserting a dummy strip in between and completing the furnace condition change while the dummy strip passes. This would result in a reduction in reactor capacity. Also, from the perspective of furnace operation, it is necessary to continue annealing as many strips of the same size or material as possible, so it is necessary to keep a large amount of inventory in front of the continuous annealing line to facilitate furnace operation planning. This resulted in increased inventory costs and the inconvenience of not being able to manufacture products at a convenient time when needed.

Means for Solving the Problems> The present invention aims to solve the problem that the heating temperature cannot be quickly controlled in the heating device of the metal strip continuous annealing furnace using the radiant tube as the main heating source. For this purpose, in the present invention, a gas soet device that injects a temperature regulating gas set to a required temperature onto the metal strip is installed adjacent to the radiant tube from the rear of the heating zone to the rear end of the heating zone. I decided to do so.

In the continuous annealing furnace according to the present invention, when metal strips with different thicknesses are supplied, the amount of burr combustion of the radiant tube is adjusted accordingly, and the gas solent device is heated to the required temperature. By injecting a set temperature regulating gas into the metal strip for a short period of time, the poor temperature response of the radiant tube is compensated for and rapid heating control is performed. Furthermore, since the gas jet device is installed from the rear of the heating zone to the rear end of the heating zone, it is possible to control the temperature to an appropriate level starting from the tip of the metal strip where the heat cycle has changed.

<Examples> Examples of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a schematic diagram of the main parts of a continuous annealing furnace according to an embodiment of the present invention, and FIG. 2 is a diagram of a gas jet device thereof.

As shown in FIG. 1, in this embodiment, the heating area is the heating zone 14.
and the soaking zone 15, from the rear of the heating zone 14 to the rearmost part of the heating zone, that is, over the rear region of the heating zone 14 and the entire soaking zone 15, the plenum chamber 21, which is a gas jet device, is heated with radiant heat. It is installed adjacent to the tube 19. As shown in FIG. 2, the plenum chamber 21 is provided with a gas duct 22 for supplying a temperature regulating gas therein.
A plurality of gas nozzles 23 are formed facing the metal strip 11 for injecting gas for temperature adjustment.

Further, 24 is a furnace wall made of a material with a small thermal time constant such as ceramic fiber, and 25 is a metal strip 11.
This is an exhaust duct for discharging the gas after the collision.

Further, a pebble heater 28 is provided outside the furnace, which is formed by filling a filling tank 26 with a pebble-like heat storage body (oil) 27 made of a high melting point material such as ceramic. pebble heater 28
The iC is supplied with 1 from its top through a hot gas supply duct 29.
High-temperature gas of 200 to 1300°C is supplied, and the high-temperature gas that has passed through one pebble heater 28 is discharged from the bottom through a high-temperature gas exhaust duct 30.

Furthermore, the bottom of the pebble heater 28 has an OHN for temperature adjustment.
,I! / gas (mixture of hydrogen and nitrogen gas) to pebble heater 2
A gas supply duct (31) for supplying the inside of the pebble heater 28 is connected via the pulp 32, and the HN gas that has passed through the pebble heater 28 is connected to the top of the pebble heater 28 through the gas duct 22.
A supply duct 3 feeding the plenum chamber 21 via
3 is connected. Further, a bypass duct 34 and its pallet 235 are provided between the supply ducts 31 and 33 to send the HN gas directly to the Blenheim channel 21 without passing it through the pebble heater 28.

In such a configuration, metal strips 1 of the same thickness
During steady operation such as heating the metal strip 1, the metal strip 11 is heated only by the radiant tube 19, but the heat cycle of the metal strip 11, the plate thickness, the plate width, the threading speed of the line, etc. change, and the production amount changes. The gas jet device is operated when a change occurs and the amount of heating needs to be changed.

That is, during steady operation, high-temperature gas heated to a high temperature of 1200 to 1300° C. by a heater (not shown) is supplied to the pebble heater 28 via the high-temperature gas supply duct 29. When high-temperature gas is supplied to the pebble heater 28, the temperature of the pebble 27 inside the pebble heater 28 gradually approaches the altitude of the high-temperature gas from the top over time, as shown in FIG. The entire interior of pebble heater 28 is maintained at a high temperature. Now, when the heat cycle of the metal strip 11 changes, the supply of high temperature gas to the pebble heater 28 is stopped, and this time HN gas is supplied into the pebble heater 28 from the bottom. The HNf/s supplied into the pebble heater 28 is heated to a high temperature before reaching its outlet, as shown in FIG. 3(b). In other words, by passing even low-temperature HN gas through the pebble heater 28, which has a large heat capacity and transfer area at high temperature, its temperature can be raised to that of the high-temperature pebble 27 in a few seconds, and this temperature can be increased to 5.
Can be held for ~10 minutes. By appropriately mixing this high-temperature HN gas with unheated low-temperature HN gas that has passed through the bypass duct 34)
, HN gas is brought to a required temperature and supplied to the plenum chamber 21 as a temperature control gas.

For example, if a metal strip 11 with a thicker plate thickness and an increased production volume is supplied to the continuous annealing furnace 12, the burner combustion rate of the laso ant tubes 19 in the heating zone 14 and soaking zone 15 will be increased, and the gas jet device will By injecting HN gas heated to a required high temperature to the metal strip 11 until the temperature of the lano ant tube 7'19 reaches the required high temperature, the required metal strip 1 is
The temperature can be raised to 1 without any time delay. still,
Here, the gas jet device is installed over the rear region of the heating zone 14 and the entire soaking zone 15, so the production volume has changed (see below). I can do it. In other words, gas
If the cutting device is heated only in the middle of the heating region, the temperature change of the laso ant tube 19 will be slow in the rear part with respect to the running direction of the metal strip 11, and the metal strip 11 will heat up before reaching a predetermined temperature. The tip of the will pass through.

The front end of the area where such a gas jet device is installed corresponds to changes in the amount of heat load determined by the product of the heat cycle or line speed of the target metal strip 11, the plate thickness, and the temperature difference for the strip temperature increase. It should be determined according to the amount of change in heat load (usually about 20%), and the gas jet device is designed to reduce the heat load from the rear area of the heating zone 14 corresponding to at least a 20 to 30 inch decrease in the amount of heat load on the metal strip 11. However, if the snoet installation area is short, for example, when the plate thickness becomes thin, the metal strip 11 will be overheated to the annealing temperature or higher before reaching the gas jet installation area, resulting in so-called overannealing. It is from.

FIG. 4(a) shows the stator y' in the furnace according to this embodiment.
:Represents the change in tr temperature・Figure 4 (a)
.

As shown in , for example, as the plate thickness becomes thinner, the heat load ′
As the amount decreases, the temperature rises rapidly compared to the steady state, as shown by the broken line, but the temperature is suppressed to a predetermined temperature when it approaches the area where the Snoet device is installed. Further, FIG. 4(b) is a graph showing the change in strip temperature according to another embodiment of the present invention in which the gas jet installation area is divided. It was also installed in

Roughly speaking, FIGS. 5(a) and 5(b) show FIG. 4(a) when the present invention is implemented in a continuous annealing furnace without a soaking zone 15.

It is a graph corresponding to (b). In a continuous annealing furnace without a soaking zone 15, the heating zone is limited to the heating zone 14.
The gas jet device is therefore installed in the rear region of the heating zone 14.

In addition, in the above explanation, we have explained the case where, for example, the plate thickness becomes smaller and the heat load decreases in one area strip process, but the heat load cover increases as the plate thickness, plate width, and line threading speed increase. If H is mixed at the required high temperature,
By supplying N force to the Blenheim chamber machine 21, the metal strip 11 can be maintained at the required high annealing temperature until the temperature of the radiant tube 19 rises to the required temperature. .

<Effects of the Invention> As described above, according to the present invention, it is possible to quickly control the heating temperature in response to changes in the amount of heat load on the metal strip, thereby improving annealing efficiency and improving product yield. This will improve performance.

[Brief explanation of the drawing]

Figure fs1 is a schematic diagram of the main parts of a continuous annealing furnace according to an embodiment of the present invention, Figure 2 is a diagram of the configuration of its gas jet device, and Figures 3 (a) and (b) are high temperature diagrams in the pebble heater. Temperature distribution diagrams during gas and HN gas supply Figures 4 (a), (b), and Figure 5 (a). (b) is a glass showing the change in strip temperature in a continuous annealing furnace according to the present invention, and FIG. 6 is a schematic diagram of an example of the overall configuration of a conventional continuous annealing furnace. In the drawings, 11 is a metal strip, 12 is a continuous annealing furnace, 14 is a heating zone, 15 is a soaking zone, 19 is a radiant tube, 21 is a plenum chamber, and 28 is a pebble heater.

Claims (1)

[Claims] During continuous annealing of metal strips, the required temperature,
The front end of the gas jet device that injects plate temperature regulating gas set at a flow rate onto the metal strip has a heat load change of 2.
1. A heating device for a continuous annealing furnace for metal strip, characterized in that the front end of a rear region of a heating zone corresponding to 0 to 30% is provided, and the rear end is provided over the rear end of the heating zone or throughout the soaking zone.