JP2782465B2 - Bright annealing method for stainless steel strip and elastic rotating roll used in the method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a bright annealing furnace for performing bright annealing of a stainless steel strip, in which air enters the furnace from a steel strip inlet / outlet seal portion of the furnace. The present invention relates to a bright annealing method for producing a stainless steel strip having a good quality BA surface finish in a stable operation while minimizing the occurrence of a rust, and an elastic rotating roll suitable for carrying out this method.

[Conventional technology]

Generally, when performing bright annealing of a cold-rolled stainless steel strip to manufacture a cold-rolled stainless steel sheet or a steel strip BA surface finish product specified in JIS G4305, G4307, the stainless steel strip is placed in a bright annealing furnace. Is heated by a heat source from an electric heating element, and is annealed in an environment filled with a non-oxidizing atmosphere gas in a furnace in order to prevent the surface from being oxidized and having poor surface gloss. Will be As such an atmospheric gas, a gas mainly containing hydrogen gas, for example, a blend gas of H ₂ : 75% and N ₂ : 25% is used. Since the atmosphere gas having such a composition is explosive itself, the intrusion of air into the annealing furnace not only promotes the oxidation of the surface of the stainless steel strip but also leads to the danger of explosion. Therefore, a structure is adopted in which a seal member is pressed against the front and back surfaces of the stainless steel strip to seal the inside of the furnace at the entrance and exit of the stainless steel strip of the bright annealing furnace. The state of passing the stainless steel strip through the bright annealing furnace and the sealing state thereof will be described with reference to the drawings.

FIG. 1 is a schematic explanatory view showing the entire structure of a bright annealing furnace and a state of passing a plate, and FIGS. 2 and 3 are enlarged explanatory views of various sealing structures at the entrance and exit of a steel strip.

As shown in FIG. 1, the stainless steel strip 1 enters the furnace body 2 through the inlet seal part 3, is turned in the traveling direction by the top roll 4, is heated in the heating zone 5, is annealed, and then cooled. It exits through zone 6 through outlet seal 7. Atmosphere gas is always supplied to the gas inlet 19 in the furnace body 2.
The furnace pressure is usually maintained at a gauge pressure of about 10 to 50 mmH ₂ O, and the furnace atmosphere gas gradually leaks to the outside air from the inlet / outlet seal parts 3 and 7 as described below. In this way, air is prevented from entering the furnace body 2.

FIG. 2 shows a conventional steel pad inlet / outlet seal portion using a felt pad system. An elastic felt pad 8 is sandwiched between a metal roll 9 and a seal fitting 10 as a seal member. The felt pad 8 is pulled by friction with the stainless steel strip 1 passing therethrough, but the metal roll 9 is prevented from rotating and does not normally rotate. However, when the dust and dirt adhering to the surface of the steel strip 1 are wiped and accumulated on the surface of the felt pad 8, the roll 9 contacts a clean portion of the felt pad 8 with the surface of the stainless steel strip 1. The rotation stopper is removed when supplying. Such a pair of metal rolls 9 presses the felt pad 8 against the front and back surfaces of the stainless steel strip 1 passing between the rolls 9 and at the same time, also presses against the seal fitting 10 to shut off the inside of the furnace from the outside air and seal. It has a structure to do.

Next, FIG. 3 shows an inlet / outlet seal portion of another structure related to the present invention. This is because, in the felt pad type seal structure shown in FIG. 2, the flaws caused by dust or the like adhering to the felt pad 8 on the front and back surfaces of the stainless steel strip 1 and the thin stainless steel strip 1 passing plate. The purpose of this is to eliminate the drawback that the tension in the furnace is hard to be obtained, etc. The front and back surfaces of the stainless steel strip 1 are sandwiched between elastic rotating rolls 11 lined with an elastic body 11a such as silicon rubber as a sealing member, and the bright annealing The inside of the furnace 2 is sealed off from outside air. In FIG. 3, the stainless steel strip 1 moves in the direction of the arrow, and the elastic rotary roll 11 rotates as the inlet seal part 3 rotates. The structure is the same except that the direction and the rotation direction of the elastic rotating roll 11 are reversed.

Also in these seal structures, there is a small gap at the end of the width of the stainless steel strip 1 which cannot be closed by the seal member made of the elastic body 11a such as the felt pad 8 or silicone rubber. Always inject,
By adjusting the injection amount, the furnace pressure was adjusted to be slightly higher than the outside air as described above, and the intrusion of air into the furnace was suppressed while constantly leaking a small amount of atmospheric gas from the gap.

However, in spite of the various measures described above, despite the implementation of sealing measures, it is lined with the elastic body shown in FIG. 3 which is particularly excellent in that it does not generate scratches and that it is easy to take a stable furnace tension. Even when the elastic rotating roll type seal structure is adopted for the steel strip inlet / outlet, air enters and it is difficult to maintain a stable furnace pressure, which disturbs the furnace atmosphere and increases the oxygen concentration in the furnace. As a result, an oxide film was formed on the front and back surfaces of the stainless steel strip to cause coloring and markedly lower the quality. And in such a case,
A large amount of expensive atmosphere gas must be supplied to replace the invading air with the atmosphere gas, resulting in an economic loss.

[Problems to be solved by the invention]

The present invention solves the drawbacks of the above-mentioned prior art, and suppresses the intrusion of air from the inlet / outlet seal portion almost completely and hardly increases the consumption of atmospheric gas. An object of the present invention is to provide a bright annealing method for producing a stainless steel strip having a good quality BA surface finish and an elastic rotating roll suitable for carrying out the method.

[Means for solving the problem]

As a result of various studies, the present inventors have found that air still enters the furnace while maintaining the furnace pressure higher than the outside air, particularly from the inlet seal, and one of the causes is as follows. The air around the stainless steel strip sent into the bright annealing furnace cannot be completely wiped off by the seal member, and a small amount of air adheres to the front and back surfaces of the stainless steel strip and enters the furnace while adhering to the surface. The main reason in the case of the elastic rotating roll method shown in (1) is that the elastic rotating roll is entrained in the air when it rotates along with the feeding of the stainless steel strip. The present invention was completed by stacking.

That is, the bright annealing method of the stainless steel strip according to the present invention,
A non-oxidizing atmosphere gas is quantitatively adjusted in a vertical bright annealing furnace equipped with a steel strip inlet seal and an outlet seal with a structure in which a pair of elastic rotating rolls are pressed against the front and back surfaces of a stainless steel strip to seal them. A method in which the stainless steel strip is continuously passed through the steel strip inlet / outlet while brightly annealing while controlling the furnace pressure by continuously supplying while suppressing air intrusion into the furnace from the inlet / outlet seal part. Then, by adjusting the pressing force of the pair of elastic rotating rolls on the front and back surfaces of the stainless steel strip in each of the seal portions, the amount of atmospheric gas leakage from the inlet seal portion is made larger than the amount of leakage from the outlet seal portion. It is characterized by.

Further, as a preferred elastic rotating roll used for carrying out this method, the elastic rotating roll pressing against the front and back surfaces of the stainless steel strip has an urging means for rotating the stainless steel strip following the passing plate of the stainless steel strip. It is characterized by.

The bright annealing method for a stainless steel strip according to the present invention will be further described in detail with reference to FIGS.

In a state where air adheres to the surface of the stainless steel strip 1 which is fed into the bright annealing furnace 2,
It has been recognized that increasing the pressing force of the sealing member against the stainless steel strip 1 to prevent the material itself from being caught by the rotation of the steel plate and entering the furnace 2 has a certain effect, but is shown in FIG. Not only in the case of the felt pad system, but also in the case of the elastic rotating roll system shown in FIG. Therefore, in the present invention, conversely, the stainless steel strip 1 of the seal member of the inlet seal portion 3 is used.
In order to increase the amount of leakage of the atmospheric gas by reducing the pressing force on the front and back surfaces of the above, and to minimize the total leakage of the atmospheric gas as much as possible, the amount of leakage from the outlet seal portion 7 is reduced to the minimum necessary. Thus, the amount of atmospheric gas leaking from the inlet seal 3 is made larger than that from the outlet roll 7. Then, the injection amount of the atmosphere gas is increased as necessary. By adjusting the amount of leakage of the atmospheric gas, the air is prevented from entering from the inlet seal portion 3 or the air that has once entered enters and is soon removed from the furnace again together with the flow of the atmospheric gas.

In this case, as shown in FIG.
Is pressed against the front and back surfaces of the sealing hardware 10 and the stainless steel strip 1,
This pressing force must be adjusted so that the elastic body 11a of the elastic rotating roll 11 slightly deforms and seals. When the elastic rotary roll 11 is pressed by a strong pressing force to such an extent that a large flat deformation occurs, the elastic rotary roll 11 is difficult to rotate smoothly following the passing speed of the stainless steel strip 1. It is necessary to apply a turning force. The pressing force adjusting means and the auxiliary biasing means provided on the elastic rotating roll 11 will be described with reference to the schematic embodiment of FIG.

Elastic rotating roll for pressing the front and back of stainless steel strip 1
11 and 11 are supported by support plates 12 and 12. By the tension of the coil spring installed between the support plates 12 and 12 arranged on the front and back,
The elastic rotating rolls 11 are pressed against the front and back surfaces of the stainless steel strip 1, respectively. The pressing force is adjusted by relaxing the tension of the coil spring through the link motion by the stroke of the pressing force adjusting cylinder 13. The elastic rotating roll 11 supported by the supporting plates 12 and 12 is provided with auxiliary torque (variable speed motor 14) through a cyclo reducer 15, a distributor 16, a coupling 17 and a universal joint 18. Is applied.

(Operation)

The details of the reason why the above effects are obtained in connection with the seemingly incompatible phenomenon of leakage of atmospheric gas due to intrusion of air are unknown, but the influence of the magnitude of the pressing force of the sealing member is affected by the influence of air on the stainless steel strip 1. This is probably because the amount of atmospheric gas leakage based on the size of the gap generated at the end of the width of the stainless steel strip 1 is greater than the amount of adhesion to the surface or the amount of entrainment. The fact that the leakage amount of the atmospheric gas from the inlet seal portion 3 is larger than that from the outlet seal portion 7 is due to the fact that the gas seal port 19
Gas inlet in the opposite direction to the flow rate of the ambient gas in the flow path leading to
This means that the flow rate is larger than the flow rate of the flow path from 19 to the outlet seal 7. Accordingly, if the magnitude of the flow rate is represented by the magnitude of the thickness of the flow direction line 20 of the atmospheric gas, it becomes as shown in FIG.
The magnitude of the gas flow rate in the two flow paths cannot be necessarily compared only by the pressure gradient, and there are various factors such as the length of the flow path, the size of the cross section, and the shape. Since the gas inlet 19 is provided closer to the outlet seal portion 7 than the center of the entire flow path, as shown in FIG. small influence of the flow channel cross-sectional shape, follow connexion inlet seal portion just inside the road in the pressure P ₁ of the 3 are summer considerably smaller than the outlet sealing portion 7 side of the furnace pressure P _2. As a result of the preliminary test, when the optimum furnace pressures P ₁ and P ₂ for preventing air intrusion are determined for certain operating conditions, the furnace pressures at the above locations are controlled so as to be P ₁ and P ₂ respectively. What is necessary is just to carry out annealing.

〔Example〕

The bright annealing method for a stainless steel strip according to the present invention will be specifically described with reference to Examples and Comparative Examples.

In a vertical annealing furnace similar to FIG. 1 in which the seal portions of the elastic rotating roll type shown in FIG. 3 are attached to the inlet and outlet seal portions 3 and 7, respectively, a mixed gas (H ₂ : 75% + N) is used as an atmosphere gas. _2: using 25%), a number of stainless steel strip 1 (SUS304, width 1250 mm, Okuita target speed 40 m / min bright annealing having a thickness of 0.95 mm), was performed in a heating zone target temperature 1010 ° C..

The above mixed gas is supplied from the gas inlet 19 to the original gauge pressure of about 0.65
Inject at kg / cm ² , average injection amount of this mixed gas (Nm ³ / H)
Bright annealing was performed while changing and adjusting the pressing force (kg / cm ² ) of the elastic rotating rolls on the inlet and outlet sides of the steel strip. Throughout the examples and comparative examples, the average gas leakage (Nm ³ / H) and average O ₂ concentration at the inlet and outlet sides of the steel strip at each adjustment stage [measurement positions: points A and B shown in FIG. 1, surface glossiness The following table summarizes the results of the survey of point C, which has the greatest influence on the steel strip, and the results of the appearance of the steel strip surface condition after bright annealing. O ₂ concentration at each measurement position in the furnace, a gas chromatograph (Hitachi, Model 164) as concentration analyzer was investigated using.

As a result of the investigation shown in the attached table, in the examples of the present invention, the average amount of gas leakage on the inlet side was adjusted so as to reduce the pressing force of the elastic rotating roll on the inlet side from the steel strip outlet side in comparison with the comparative example. Increased, and as a result, the average O ₂ concentration at the measurement point A on the inlet side was significantly reduced as compared with the conventional comparative example. Accordingly, the C in the heating zone 5 which has the greatest effect on the surface quality (appearance) of the stainless steel strip after bright annealing
The average O ₂ concentration at the point was significantly reduced as compared with the conventional comparative example.

As a result, in all of Examples 1 to 5, clean stainless steel strips with excellent gloss were obtained, but in Comparative Examples 1 to 4, gloss and resolution were reduced, and the surface coloration was reduced. Something that has been acknowledged has occurred.

〔The invention's effect〕

As described in detail above, the bright annealing method for a stainless steel strip according to the present invention is performed by elastic rotation as a sealing member so that the amount of atmospheric gas leaking from the inlet seal portion of the bright annealing furnace is larger than that from the outlet seal portion. By performing the bright annealing by adjusting the pressing force of the roll, the intrusion of air from the inlet seal to the furnace is almost completely suppressed, and the surface of the stainless steel strip does not generate scratches and the like, and It is an epoch-making method that prevents the oxidation of the surface of the stainless steel strip without significantly increasing the consumption of the atmosphere gas, and enables bright annealing with excellent gloss to be performed with stable operability. The elastic rotating roll used for the bright annealing method of the stainless steel strip follows the passing speed of the stainless steel strip due to the strong pressing force when the bright annealing method of the stainless steel strip according to the present invention having the above-mentioned effect is performed. Elastic rotation roll Te that is not less able to practice the bright annealing of being prevented from occurrence of hardly made phenomena smoothly rotate smoothly stainless steel strip, is very large industrial value of the present invention.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view showing the entire structure of a bright annealing furnace and a state of passing a plate, FIGS. 2 and 3 are enlarged explanatory views of various sealing structures at the entrance and exit of a steel strip, and FIG. It is a schematic example of the Example of adjustment of the pressing force with respect to the steel strip entrance / exit seal part of a roll, and urging means. In the drawings 1... Stainless steel strip 2... Furnace body 3... Inlet seal section 4... Top roll 5... Heating zone 6... Cooling zone 7... Outlet seal section 8 .. felt pad 9. Seal metal 11 Elastic rotating roll 11a Elastic body 12 Support plate 13 Cylinder for adjusting pressing force 14 Variable speed motor 15 Cyclo reducer 16 Distributor 17 Coupling 18 Universal joint 19 Gas inlet 20 Atmospheric gas flow direction line P ₁ Furnace pressure inside inlet seal P ₂ Furnace pressure inside outlet seal

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C21D 1 / 74,9 / 46,9 / 52-9/56 F27D 7/06

Claims (2)

(57) [Claims] A non-oxidizing atmosphere gas is placed in a vertical bright annealing furnace having a steel strip inlet seal portion and an outlet seal portion having a structure in which a pair of elastic rotating rolls are pressed against the front and back surfaces of a stainless steel strip to seal them. The stainless steel strip is continuously passed through the steel strip inlet and outlet while the furnace pressure is adjusted while controlling the furnace pressure to suppress the intrusion of air into the furnace from the inlet and outlet seals. A method of bright annealing, wherein the pressure of the pair of elastic rotating rolls on each of the seal portions on the front and back surfaces of the stainless steel strip is adjusted to reduce the amount of atmospheric gas leakage from the inlet seal portion to the amount of leakage from the outlet seal portion. A bright annealing method for a stainless steel strip, characterized in that the number is larger than that of a stainless steel strip. 2. An urging means for rotating an elastic rotary roll pressing against the front and back surfaces of a stainless steel strip used for carrying out the bright annealing method for stainless steel according to claim 1. An elastic rotating roll used for a bright annealing method for a stainless steel strip, characterized by comprising means.