JPH0453933B2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The technical content described in this specification regarding a continuous annealing furnace that continuously anneales a metal strip is to catenary support the metal strip in a non-contact manner by ejecting gas. This invention relates to a continuous annealing furnace for heat treatment.

Continuous annealing furnaces for metal strips are often of the type in which the metal strips are supported and conveyed by support rolls within the furnace. However, surface defects such as pick-up scratches are likely to occur on the metal strip due to the support roll in contact with the metal strip (the occurrence of pick-up scratches tends to be more severe in higher temperature areas); Since the inside of the metal strip is water-cooled, heat loss is large and the quality of the metal strip is adversely affected.

Therefore, a continuous annealing furnace has been developed in which a metal strip running through the annealing furnace is supported by a catenary in a non-contact manner using gas jets, and studies are underway to improve the surface properties of the metal strip.

(Prior art) JP-A-58-120730, JP-A-120731, and JP-A No. 1983-120730;
Each publication of No. 120740 discloses a continuous annealing furnace equipped with a flotation device that communicates with a reducing atmosphere gas circulation system.

First, in JP-A-58-120730 and JP-A-120731, flotation devices are closely arranged below the running path of the metal strip, and heating is performed only from above the running path, so that it can cover a wide area in a short time. When heating to a predetermined temperature, a long heating source is required, which may increase equipment costs. Furthermore, as the furnace section becomes longer, the amount of heat dissipated from the furnace body increases, and it is also conceivable that energy consumption increases. It is possible to provide a heating function in addition to supporting the metal strip using a Yoshiba flotation device, but in this case it is difficult to maintain an even amount of heat input from the top and bottom of the metal strip, and uniform heating is difficult. If this is not possible, deformation of the strip is expected.

Furthermore, in JP-A-58-120740, heating from both sides of the metal strip has the advantage of shortening the furnace length, but since the gas is ejected from above and below the metal strip, the ejection force of the gas from the upper nozzle is reduced. Therefore, a balance must be maintained between the sum of the force pressing the metal strip and the metal strip's own weight, and the pushing up force due to the jet force of the gas from the lower nozzle. Therefore, in order to stabilize the running of the strip, it is necessary to increase the capacity of the blower that conveys the gas to the nozzle.

(Problems to be Solved by the Invention) It is an object of the present invention to stabilize non-contact support of the strip by gas jets in a continuous annealing furnace and to reduce energy consumption during annealing.

(Means for Solving the Problems) This invention provides a metal strip that runs horizontally to pass through a heating zone and a cooling zone, and a nozzle opening that extends below the running path of the metal strip in a direction that intersects with the running path. A continuous annealing furnace which heat-treats a running metal strip while catennally supporting it in a non-contact manner by ejecting gas from a number of wind boxes arranged at predetermined intervals along a running route, A buff-full plate is installed on the top surface of the wind box that protrudes along the running path of the metal strip and limits the escape flow toward the side edges of the ejected impulse against the bottom surface of the metal strip. This is a continuous annealing furnace characterized in that the static pressure is applied to the catenary support of the metal strip.

Now, FIG. 1 shows the essential parts of a continuous annealing furnace 1 for cold-rolled steel strips, and as shown in FIG. 3 is disposed, and a final cooling zone 4 is further disposed downstream of the continuous annealing furnace 1.

The continuous annealing furnace 1 includes a heating zone 5 and a cooling zone 6 as essential parts of the present invention, and the heating zone 5 contains metal heated to 750 to 800°C in the pre-heating zone 2 and the vertical heating zone 3. Place the strip S at 850-900℃.
After being heated to 750 to 800°C in cooling zone 6, it is sent to final cooling zone 4.

As shown in FIG. 3, in the heating zone 5, a plurality of radiant tubes 8 equipped with burners 7 as heaters are arranged above and below the running path of the metal strip S, and the metal strip S is uniformly heated. 850
Bring to ~950℃. The cooling zone 6, which is provided in a state where it is thermally isolated from the heating zone 5 through a seal portion 9, is equipped with a pair of metal strips S sandwiched from above and below as a cooler, as shown in FIG. A bifurcated plenum chamber 10 is provided, and a gas cooler 12 and a gas circulation fan 13 are connected to this plenum chamber 10 via piping 11. Plenum chamber 1
0 has a large number of nozzles 1 directed toward the metal strip S.
4 are provided, and the metal strip S is cooled to 750 to 800°C by the cooling gas injected from these nozzles 14. This cooling gas is recovered from a recovery port 16 provided in the furnace wall 15, cooled by a gas cooler 12, and then supplied to the plenum chamber 10 again from a gas circulation fan 18.

Further, over the heating zone 5, sealing section 9, and cooling zone 6, a plurality of wind boxes 17 shown in FIGS. 5 and 6, for example, are arranged at predetermined intervals below the travel path of the metal strip S. The radiant tube 8 and the plenum chamber 10 are arranged between the wind boxes 17, respectively. From each wind box 17, a metal strip S
A gas such as hydrogen nitride gas is ejected toward the lower surface of the metal strip S, and the ejected gas catennally supports the metal strip S horizontally in a non-contact manner (see FIG. 6).

The wind box 17 includes a header 19 into which gas is fed via piping 18, a slit-shaped nozzle 20 provided across the width direction of the strip S running before and after the header 19, and a gas from the nozzle 20. The metal strip S is provided with a buffle plate 21 that restricts the metal strip S from escaping from its side edge after colliding with the lower surface of the metal strip S. The baffle plate 21 is designed to restrict the escape flow of gas from the side edges of the metal strip S while the metal strip S is running.
Static pressure is generated between the metal strip S and the upper surface of the metal strip S, and this together with the gas jetting against the lower surface of the metal strip S allows the metal strip S to be supported without contact. Note that the upper surface of the wind box 17, which serves as the pressure receiving surface 22 for the static pressure of the gas, is a flat surface to ensure uniform pressure distribution.

(Function) For example, the length of the heating zone and cooling zone where the Γ flotation device is installed...
60m Installation interval of Γ wind box...5m Length of pressure receiving surface by Γ wind box/Total furnace length...approximately 12% A continuous annealing furnace with a plate thickness of 0.2 to 2.0
When a metal strip with a width of 600 to 1800 mm is threaded at a line speed of 40 to 400 m/min, the unit tension applied to the metal strip is 0.3 to 0.5.
Kg/ ^mm2 , the amount of catenary generated between the wind boxes due to the weight of the metal strip is 10 to 15 mm. This is negligibly small compared to the installation interval of the wind boxes (5 m), and the metal strip bus line can be regarded as almost horizontal. Therefore, even if heating devices such as radiant tubes are set at equal intervals above and below the running path of the metal strip, there will be no difference in radiant heat flux between the upper and lower surfaces of the metal strip. No temperature difference occurs.

Similarly, even if the cooling devices are placed at equal intervals above and below the bus line of the metal strip in the cooling zone, if the upper and lower cooling devices have the same function, the gas jet pressure received from the top and bottom of the metal strip will be the same, and the metal strip will receive the same gas jet pressure. It is possible to run the metal strip stably, and there is no difference in temperature between the upper and lower surfaces of the metal strip after cooling.

Furthermore, the function of the wind box will be described in comparison with a general wind box of this type.

First, a wind box generally used in a continuous annealing furnace has a structure shown in FIG. That is, the main body 30
The interior thereof is a chamber for a fluid such as a reducing gas, and the surface facing the metal strip S is a pressure receiving surface 31. Then, pressurized gas from a gas supply source is ejected obliquely from the slit 33 to the strip S through the pipe 32, thereby supporting the metal strip S in a non-contact state.

In the above type of wind box, metal strip S
Since there is a large amount of pressurized gas leaking from the side edges, support cannot be expected to be supported by the static pressure of the pressurized gas.

Furthermore, if the shape of the metal strip S is bad, the static pressure balance in the width direction will be disrupted, and the leakage amount of pressurized gas will be different at both ends, causing the metal strip to flap as shown in FIG.

On the other hand, in the wind box shown in FIG. 5, the leakage of gas from the side edges of the metal strip can be restricted by the action of the baffle plate. Furthermore, since the metal strip in a continuous annealing furnace is heated to a high temperature and has very low rigidity, the metal strip is substantially flat in the width direction or length direction. Therefore, the metal strip can be reliably supported by gas pressure.

In addition, even if the static pressure balance collapses in the width direction of the metal strip due to the poor shape of the metal strip, the leakage of the flotation gas is restricted by the buff-full plate.
Static pressure balance quickly and automatically returns to its original state.
The metal strips don't flap.

(Effects of the Invention) According to the present invention, a metal strip can be annealed under stable running without contact.

In addition, if heating or cooling devices are placed above and below the metal strip, energy consumption can be reduced.

Incidentally, compared to the case where annealing is performed by heating the metal strip from above, the furnace length is approximately twice as long, and fuel consumption increases by approximately 5%. Similarly,
If a pair of upper and lower flotation devices is installed, the power cost and blower power specifications will increase approximately 8 to 4 times.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram showing a continuous annealing furnace, Figure 2 is an explanatory diagram showing continuous annealing equipment, and Figure 3 is an explanatory diagram showing the continuous annealing equipment.
Line sectional view, Figure 4 is line sectional view of Figure 2 - line sectional view, Figure 5.
6 is a perspective view showing the wind box, FIG. 6 is a sectional view taken along the line of FIG. 5, FIG. 7 is a perspective view showing the wind box, and FIG. 8 is an explanatory diagram showing the movement of the strip. 3... Continuous annealing furnace, 4... Heating zone, 5... Cooling zone, 15... Wind box, 21... Batsuful plate,
S...Metal strip.

Claims (1)

[Scope of Claims] 1. A metal strip is passed horizontally through a heating zone and a cooling zone, and has a nozzle opening extending in a direction intersecting the traveling path below the traveling path of the metal strip. Gas is ejected from a number of wind boxes placed at predetermined intervals along the
This is a continuous annealing furnace that heat-treats a running metal strip while catenary-supporting it without contact, with a metal strip protruding from the top surface of the wind box along the running path of the metal strip to the side edge of the ejected impulse against the bottom surface of the metal strip. A continuous annealing furnace characterized in that a buff-full plate is provided to limit the escape flow of the metal strip, and the static pressure generated by the restriction of the escape flow is assisted by the catenary support of the metal strip. 2. A continuous annealing furnace as claimed in claim 1, characterized in that the heating zone comprises a pair of heaters arranged to sandwich the metal strip in and against the wind box. 3. Continuous annealing furnace according to claim 1, characterized in that the cooling zone comprises a pair of coolers arranged to sandwich the metal strip in and against the wind box.