JP3051588B2 - Annealing and descaling of stainless steel sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for annealing and descaling a rolled stainless steel sheet.

[0002]

2. Description of the Related Art A conventional continuous annealing / descaling method for a rolled stainless steel sheet will be described with reference to FIG.

In FIG. 4, S is a stainless steel strip in a rolled and hardened state, and 101 is a state in which it is wound in a coil shape.

[0004] Reference numeral 102 denotes a continuous annealing furnace. The stainless steel strip S is annealed by heating at a high temperature, cooled to about 500 ° C. by a cooling device 103, and then introduced into an alkali molten salt tank 120. Here, the oxide scale generated on the steel strip surface is transformed into a water-soluble alkali compound.

[0005] Thereafter, in order to recover the excess alkali molten salt attached to the surface, the excess alkali molten salt is squeezed out by a gas force using, for example, a gas wiping nozzle 123 and returned to the salt tank 120.

[0006] Next, it enters a cooling device 125 through a deflector roll 124, where it is cooled to almost normal temperature, and after washing away alkali salts remaining on the surface with water, it enters an acid pickling tank 127, where it is washed. After the scale is completely removed by the final pickling, the scale is completely removed, and then enters a washing tank 128 to remove the residual acid solution, and then is dried by the drier 129 and wound as a product coil by the winder 130. .

[0007]

In the conventional method of continuous annealing and descaling of a rolled stainless steel sheet as described above, a steel strip S is placed in an alkali molten salt tank 120.
A part of the scale formed on the surface of the steel strip falls off, accumulates in the tank, and gets caught between the sink roll groups 121 and 122 arranged in the tank and the steel strip S, and the steel strip S is scratched. There is a problem to do.

Further, there is a problem that a great deal of labor and cost are involved in removing the fall-off scale accumulated in the tank outside the tank and processing the same.

Therefore, there is a demand for a process that does not employ an alkali molten salt tank.

[0010] In the present invention, in order to utilize the excellent descaling property possessed by the alkali molten salt, a required amount of the alkali molten salt is applied to both sides of the stainless steel strip to maintain a good pickling property and to remove the above-mentioned falling scale. It is an object of the present invention to provide a new method for annealing and descaling stainless steel sheets, which aims at eliminating the treatment of stainless steel.

[0011]

Annealing & descaling method of the stainless steel sheet of the present invention as a configuration for achieving the above object In order to achieve the above, after the rolled stainless steel plate was continuously annealed in a method of descaling, A step of cooling the annealed steel sheet drawn out by the annealing furnace to 300 to 630 ° C., and a method of rotating a wire brush by rotating either an alkali molten salt or an alkali mixed salt slurry composed of alkali-based salts and water. The cooled annealing using centrifugal force
After applying it to both sides of the finished steel sheet, hold it for 5-60 seconds.
And degree, the steel plate cooling, was subjected to washing treatment, it is characterized by comprising the step of pickling finish.

[0012]

The reaction between the scale generated on the surface of the stainless steel sheet by annealing and the alkali molten salt (hereinafter referred to as alkali salt) is estimated as in the following equation (1).

[0013]

(Equation 1)

That is, 17 mol of alkali salt is required for 2 mol of scale, and when the scale thickness of the surface of the annealed stainless steel sheet is 4 μm, the amount of alkali salt required as a reaction equivalent is about 20 μm. That is, about 20 μm
Only an alkali salt may be applied.

Therefore, if an alkali salt is applied to the surface of a steel sheet by a method utilizing the centrifugal force of a wire brush rotated at a high speed as in the present invention, a reaction equivalent of about 2 is required.
Alkaline salt of 0 μm can be applied almost accurately to the surface of a high-temperature stainless steel plate, and there is no need to squeeze excess salt with a gas jet as in the conventional case.

Further, since there is no need to provide an alkali molten salt tank as in the conventional apparatus, the scale attached to the stainless steel plate does not fall into the tank, so that maintenance work and processing work on this point are unnecessary.

The alkali salt to be further applied is in a molten state at a high temperature, and the hot-rolled steel sheet is also at 300 to 600 ° C.
And the high temperature, the reaction between the scale of the formula (1) and the alkali salt can proceed sufficiently quickly.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to FIGS. 1 and 2 showing one embodiment of the present invention.

FIG. 1 is a view for explaining the process of one embodiment of the present invention, and FIG. 2 is a detail of a wire brush portion for applying only a required amount of an alkali molten salt or an alkali mixed salt slurry to a steel strip surface during the process. FIG.

In FIG. 1, S denotes a stainless steel strip in a rolled and hardened state, and 1 denotes a state in which it is wound in a coil shape. Reference numeral 2 denotes a continuous annealing furnace, in which the steel strip S is annealed by high-temperature heating, and then cooled to 350 to 630 ° C. by the cooling device 3.

The cooling temperature is determined by the reactivity with the alkali molten salt applied in the next step. That is, the lower limit of 350 ° C. is the minimum temperature required for the scale expressed by the above formula (1) and the alkali salt to actively react, and the upper limit of 630 ° C.
Means that the alkali salt applied on the steel strip S is NO
_This is the upper limit temperature at which _X is not generated.

The annealed steel strip S cooled to a predetermined temperature is then vertically raised via a deflector roll 4 on both surfaces of the steel strip 1 so as to be coated with an alkali molten salt or an alkali mixed salt slurry. On the other hand, an alkali molten salt or an alkali mixed salt slurry is applied to a predetermined thickness by the wire brushes 5 and 6 which are opposed to each other and rotate at a high speed.

Both sides of the steel strip are kept at a high temperature (300 to 630 ° C.) at which the alkali salt melts, for a period of time until the reaction between the scale of the formula (1) and the alkali salt is almost completed. .

FIG. 3 is a diagram for explaining the experimental results based on the present invention. The above-mentioned holding time is suitably 5 to 60 seconds based on the experimental results shown in FIG.

That is, as shown in FIG.
Alkali Molten Salt Descalable for Hot Rolled Steel
The correlation between the steel sheet temperature and the coating holding time at the time of coating (or the alkali mixed salt slurry) was obtained by experiment, and the result was obtained as a curve a in the figure. That is, the higher temperature side than the curve a is the range in which descaling is possible.

However, at 630 ° C. or higher (straight line b in the figure), the salt is practically unusable due to decomposition of the salt, and the straight line c indicates the upper limit of the processing time. It is a value that is decided because it becomes large and it is not economical.

Thus, the lower limit of the processing temperature is 300 ° C.

As a result, it was found that the range of the hatched portion (d) in FIG. 3 was the optimum processing range. That is, the optimal processing range is a temperature of 300 to 630 ° C. and a processing time of 5 to 60 seconds.

After that, it enters a cooling device 8 using a gas as a medium via a deflector roll 7 and
Cool to 00 ° C.

Thereafter, the water enters the water cooling device 10 through the deflector roll 9 and is cooled to near normal temperature. The water enters the water tank 11 to remove the removable surface deposits and a part of the water-soluble scale. It is washed away.

Next, the steel strip S whose excess water has been squeezed by the ringer roll 12 is fed to the deflector rolls 13 and 14.
, And then enters the pickling tank 15 where it is finished and pickled. As the acid solution, sulfuric acid or nitric acid is used.

Further, the excess acid solution is removed by a washing tank 16, dried by a drier 17, and wound up in a coil shape by a winder 18.

Next, in FIG. 2, reference numeral 5 denotes one of the wire brushes which are arranged on both sides of the steel strip S at a distance from each other.
The other wire brush 6 is arranged at the position shown in FIG. (Not shown in FIG. 2)

The alkali molten salt or alkali mixed salt slurry adhered to the wire brush 5 is applied to the surface of the steel sheet by utilizing the centrifugal force of the wire brush rotating at high speed. Reference numeral 19 denotes a tank having a scattering prevention cover, and reference numeral 20 denotes a stored liquid such as an alkali molten salt in the tank.

The material of the wire brush is preferably made of titanium, glass fiber, or the like in consideration of corrosion resistance to alkali molten salt.

After applying a molten alkali salt or a mixed alkali salt slurry to a steel sheet by a wire brush method,
Spraying a weak gas jets on both sides of the steel sheet, adhering A
The lukari molten salt or alkali mixed salt slurry can also be smoothed.

Although the method of one embodiment of the present invention has been described in detail, the present invention is not limited to the above embodiment.
Various changes can be made within the scope of the technical idea of the present invention, and all of them belong to the technical scope of the present invention.

[0038]

According to the method for annealing and descaling a stainless steel sheet of the present invention, an alkali molten salt or an alkali mixed salt for transforming the scale into a water-soluble alkali compound is provided.
The mixed salt slurry can be uniformly applied in the width direction on the surface of the stainless steel strip of the material to be treated by a high-speed rotating wire brush in an amount required for the reaction. Compared to the method of pulling and extracting excess molten salt by gas jet, alkali molten salt or
Is economical because the yield of alkali mixed salt slurry is also improved.

Further, unlike the prior art, there is no danger that a part of the scale will fall into the molten salt tank and accumulate in the tank, so that maintenance work and processing work become unnecessary, and productivity is remarkably improved.

Furthermore, since the applied alkali salt is in a molten state at a high temperature and the hot-rolled steel sheet is also in a high temperature state, the reaction between the scale and the alkali salt can proceed sufficiently quickly, which is efficient. .

[Brief description of the drawings]

FIG. 1 is a process explanatory diagram showing a method according to an embodiment of the present invention.

FIG. 2 is a detailed view of a wire brush unit in FIG.

FIG. 3 is an explanatory diagram of an experimental result on which the present invention is based.

FIG. 4 is a process explanatory view showing a conventional continuous annealing / descaling method for a stainless steel sheet.

[Explanation of symbols]

 S Stainless steel strip 1 Coil rewinding machine 2 Continuous annealing furnace 3 Cooling device 4,7,9,13,14 Deflector roll 5,6 Wire brush 8 Gas type cooling device 10 Water cooling device 11 Water tank 12 Ringer roll 15 Pickling tank 16 Rinse tank 17 Dryer 18 Coil winder 20 Storage liquid such as molten salt

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yukio Kanda 4-2-2 Kannonshinmachi, Nishi-ku, Hiroshima Sanritsu Heavy Industries, Ltd. Hiroshima Works (72) Inventor Takehiko Ito 4-4-2 Kannonshinmachi, Nishi-ku, Hiroshima-shi No. Ryomei Giken Co., Ltd. (58) Field surveyed (Int. Cl. ⁷ , DB name) C23G 1/19

Claims (1)

(57) [Claims] 1. A rolled stainless steel sheet is continuously annealed .
Then , in a method of descaling, the annealed steel sheet drawn by the annealing furnace is 300 to 63
A step of cooling to 0 ° C., alkali molten salt baked to or any of the alkali mixed salt slurry consisting of salts and water mainly alkali, which is the cooling by utilizing the centrifugal force of the rotated wire brush,
After applying to both sides of the dulled steel sheet, hold for 5-60 seconds
A step, the steel plate cooling, was subjected to washing treatment, Engineering for pickling finish
Continuous annealing, descaling method of the stainless steel sheet characterized by comprising a degree.