JPS61238923A - Continuous annealing furnace - Google Patents

Abstract

PURPOSE:To run a metallic strip in a non-contact state and to execute an excellent annealing treatment in the stage of annealing the strip in a continuous annealing furnace by using a horizontal continuous annealing device having pneumatic floating devices for the strip. CONSTITUTION:A heating part C and a cooling part D via a rail part E are horizontally provided in a horizontal continuous annealing device and the metallic strip S is continuously annealed by heating the strip which is heated to 750-800 deg.C to 850-950 deg.C in the heating part C, cooling the strip down to 750-800 deg.C in the cooling part D, then supplying the strip to ordinary cooling zones. The strip is heated by radiant tubes 26 connected to burners 25 in the cooling part C. The strip is cooled by ejecting a gaseous refrigerant cooled by a gas cooler 29 from nozzles 31 of a plenum chamber 27 in the cooling part D. The strip S is run while the strip is floated by the gas ejected from plural floaters 35 provided in the lower part at specified intervals in the heating part C and the cooling part D, by which the strip is annealed in the stable state without contact with rollers, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a continuous annealing furnace in which a metal strip is supported in a floating state and passed through it.

BACKGROUND OF THE INVENTION Generally, metal strips such as cold-rolled steel sheets are continuously heat treated in continuous annealing furnaces to impart the required mechanical properties.

FIG. 4 shows a schematic configuration of a conventional continuous annealing furnace. The metal strip S that has been fed out from the payoff reel and passed through the cleaning tank and louvers is supplied to the continuous annealing furnace 1, as shown in FIG. The hook is rotated between the helper rolls 2 and meandered vertically, receiving the necessary heating and cooling depending on the mechanical properties required for the product, and finally reaches the required yield strength and tensile strength at room temperature. , mechanical properties such as deep drawing properties are imparted. Incidentally, the continuous annealing furnace 1 is filled with cyclic KN gas to prevent surface oxidation of the metal strip S.

In the continuous annealing furnace 1, a heating zone 3, a soaking zone 4, a rapid cooling zone 5, an overaging zone 6, and a final cooling zone 7 are arranged in order from the inlet side to the outlet side of the metal strip S. A heating zone consisting of a heating zone 3 and a soaking zone 4 is provided with a lasoant tube 8, which heats the metal strip S passing through it by radiation heating 9. The material is heated to 650 to 900° C. in the heating zone 3, and then transferred to the soaking zone 4 where it is maintained at that temperature or further heated slightly for several tens of seconds. continue,
The metal strip S that has left the soaking zone 4 is rapidly cooled down to about 400°C at a cooling rate of 3 to 200°C/S in a rapid cooling zone 5 by means such as a gas soet or a cooling roll (not shown), and then cooled in the subsequent overaging zone 6. It undergoes an over-aging treatment in which it is maintained at a temperature of approximately 2 minutes, and is finally cooled down to near normal temperature in the final cooling zone 7.

<Problems to be solved by the invention> In the conventional continuous annealing furnace 1, overaging treatment is performed over a long period of time in the overaging zone 6, so in a large continuous annealing furnace, the overaging zone is long. The length of the continuous annealing furnace was approximately 100 m, and the continuous annealing furnace as a whole was extremely long, exceeding 150 m. Therefore, by shortening the overaging zone 6, the continuous annealing furnace 1 can be shortened and the construction cost can be kept low. As a specific method for shortening the overaging zone 6 in this way, it is conceivable that the material composition of the metal strip S may be changed to make the heating temperature of the metal strip S higher than that of the conventional method. However, if a high-temperature metal strip S is contacted unevenly with a cold helper roll 2, or with a helper roll 2 whose surface is uneven due to adhesion of carbon, etc. in rolling oil, the high-temperature metal strip S will Since the strength of the metal strip S is reduced, the metal strip S)
Uneven cooling of the IJ tube S in six directions causes deformation of the metal strip S, which poses a problem in threading. In addition, with the high temperature metal strip S, when the metal strip S is run in the vertical direction as in the past, a shift leap phenomenon occurs due to the own weight of the metal strip S, and the width of the metal strip S becomes narrow, resulting in a problem that it cannot be used as a product. There is. Therefore, in order to increase the heating temperature of the metal strip S as described above, it is necessary to run the metal strip S stably horizontally without contacting the helper roll 2.

Here, in color coating lines and the like, a floater (gas flotation bag at') is known as a means for horizontally running the metal strip without using rolls, but this floater can only levitate the metal strip. First, since it also has the function of heating and cooling the metal strip, it could not be used as is in a continuous annealing furnace where heating is performed using a laso-ant tube and cooling is performed using a gas-soet.

In addition, as shown in FIG. 6, the above-mentioned floater is designed to levitate the υ metal strip S by ejecting gas from a narrow slit 10 in directions that collide with each other and blowing this jet onto the metal strip S. As shown in FIG. 5, a pair of floaters 11 are arranged above and below in the running direction of the metal strip S, and the metal strip S is supported in a floating manner between the upper and lower floaters 11.

The present invention has been made in view of the above-mentioned conventional circumstances, and an object of the present invention is to provide a continuous annealing furnace that allows a metal strip to run horizontally and stably. A continuous annealing furnace is a continuous annealing furnace in which a metal strip is moved horizontally to continuously anneal the strip, in which a gas flotation device that ejects a gas that levitates the strip is arranged only on the lower surface side of the strip,
It is characterized by supporting the strip in a non-contact manner.

Function> In the continuous annealing furnace according to the present invention, the floater (gas flotation device) arranged on the lower surface side of the metal strip
Only the floating support of the J-tube is carried out, heating is carried out by a lasoant tube, and cooling is carried out by a known means such as a gas soet.

Embodiment Hereinafter, an embodiment of the present invention will be described based on the drawings. FIG. 1 is a schematic configuration diagram of a portion of the continuous annealing furnace according to this embodiment, and FIGS. 2 and 3 are sectional views taken along the line Dn in FIG. 1, and I-! It is an arrow sectional view.

The part shown in Fig. 1 is a metal strip S that has been heated to 750-800°C by the conventional method of running it using a helper roll and heating it with a radiant chew 1, and then further heating it to 850-950°C. , followed by 750
This is a high-temperature heating and cooling zone A that cools the metal strip S to ~soo''C and supplies it to the normal cooling zone.
It consists of a heating section 01, a sealing section E, and a cooling section D, which are sequentially provided toward the right side in the figure where the water is delivered. Deflector rolls 21 are provided before and after the high-temperature heating and cooling zone A, and the multi-metal strip S is guided by these. In the heating section C, as shown in FIG. Heat to ℃. As shown in Fig. 3, the cooling section, which is thermally isolated from the heating section C by the seal section E, is provided with a metal tube S) with the IJ knob S narrowed from above and below. A forked plenum chamber 7"27 is provided in the plenum chamber 2.
7 is connected via piping 28 to a gas cooler 29 and a gas circulation 7 ann 30. The plenum chamber 27 is provided with a large number of nozzles 31 facing the metal strip S, and the cooling gas injected from these nozzles 31 cools the metal strip S to 750-800°C.

This cooling gas is recovered from a recovery port 33 provided in the furnace wall 32, cooled by the gas cooler 29, and supplied to the plenum chamber 27 again by the circulation fan 30.

As shown in Fig. 1, a 70-tar (gas flotation device) 35 similar to that shown in Fig. sg6 is provided in the heating section C, sealing section E1 and cooling section. A large number of them are arranged at intervals of several meters only on the lower surface side. Floating gas is injected from each floater 35 toward the bottom surface of the metal strip S.)
The metal strip S is horizontally supported by the gas pressure of the levitation gas. Therefore, −− ÷4 The traveling metal strip S is υ by the floater 35.
Supported in a non-contact state and heated by the radiant tube 26
Accordingly, cooling is performed by a gas jet from the nozzle 31, respectively.

Here, in the high-temperature state in each high-temperature heating and cooling zone A, the metal strip S has extremely low rigidity and is repeatedly bent by the upper and lower rolls in the normal heating zone in the previous process. The shape of the metal strip S is substantially flat both in the width direction and in the length direction. Therefore, as is well known, the metal strip S can be reliably levitated by a gas pressure of 70 degrees. In addition, since the 70-taters 35 are arranged at intervals that are not too long, the unit tension of the metal strip S is, for example, 0.3 to 0.5.
Kg/-, depending on the weight of the metal strip S) 70 ta 3
The amount of catenary generated between 5 and 5 is 10 to 50 m and floater 3
5, and the pass line of the metal strip S is almost horizontal. Therefore, even if the radiant tubes 26 are set at equal intervals above and below the pass line of the metal strip S, there will be no difference in radiant heat flux between the upper and lower surfaces of the metal strip S, and no temperature difference will occur. Even if 31 is set at equal intervals above and below from the pass line of the metal strip S, if the structure of the upper and lower nozzles is the same and the jet flow velocity is the same, the gas jet pressure that the metal strip S receives from above and below is equal, so the metal strip The strip S runs stably, and no temperature difference occurs between the upper and lower surfaces of the metal strip S due to cooling.

Therefore, the metal strip S is floated and supported by the floater 35.
'& Radiant Tube 2 has no problem even when running.
The metal strip S can be heated by the nozzle 31 collar (7) and cooled by the gas jet.

<Effects of the Invention> According to the continuous annealing furnace of the present invention, the gas flotation device that ejects gas that levitates the metal strip is arranged only on the lower surface side of the metal strip, so that the metal strip can be stabilized horizontally in a non-contact state. While running the metal strip, the metal strip is heated by a lasoant tube and cooled by a gas jet to achieve good annealing.

[Brief explanation of drawings]

Figure Wc1 is a schematic diagram showing a part related to an embodiment of the present invention in a continuous annealing furnace, and Figures Wc2 and 3 are cross-sectional views taken in the direction of the row arrow II and arrow I-1 in Figure 1, respectively. 4 is a schematic diagram of a conventional continuous annealing furnace, FIG. 5 is an arrangement diagram of a conventional floater, and FIG. 6 is a conceptual diagram illustrating the function of the floater. In the drawings, 26 is a lasoant tube, 27 is a plenum chamber, 31 is a nozzle, 35 is a floater (gas flotation device), and S is a metal strip.

Claims (1)

[Claims] In a continuous annealing furnace that continuously anneales a metal strip by running it in a horizontal direction, a gas flotation device that ejects gas that levitates the strip is arranged only on the bottom side of the strip, and the strip is moved in a non-contact manner. A continuous annealing furnace characterized by being supported in a state.