JP2782103B2 - Molten salt descaling equipment - Google Patents

Description

The present invention relates to a method and an apparatus for removing oxide scale formed on the surface of, for example, a cold-rolled stainless steel strip or a steel strip when annealed. It is.

[Prior art and its problems] In a conventional molten salt descaling apparatus, a stainless steel strip or a steel strip 3 is annealed in, for example, an annealing furnace 1 as shown in FIG. Cool to a temperature suitable for processing.

And the steel strip 3 which has left the cooling device 2 is a deflector roll
After being sent to the molten salt tank 19 through 18 and passing through the sink roll 20 while immersing in the molten salt at an appropriate speed,
After being pulled out of the molten salt tank 19 and squeezing out excess salt adhered to the steel strip 3 with the ringer roll 21, it is washed with the washing device 22, dried with the drying device 23, and passed through the pickling tank 24 again to completely remove the salt. After descaling, it is dried by a dryer 25 and wound up by a winder 26.

In general, a water tank immersion type that also serves as cooling is often used as the cleaning device.

In this conventional molten salt descaling apparatus, the interval L between the sink rolls 20 is determined by the time of immersion in the molten salt. Therefore, as the line speed increases, the interval L must be increased. Then, a long molten salt tank 19 is required.

Further, if the length of the molten salt tank 19 is increased, the volume thereof is also increased, and the amount of the molten salt to be filled in the molten salt tank 19 is inevitably increased. This is heated and maintained at a high temperature (for example, around 450 ° C.). Energy is also needed.

In addition, when the line speed increases, the steel strip 3 is pulled up with the excessive molten salt attached thereto, and the consumption of the molten salt increases. Furthermore, the surface area if lengthening the molten salt bath 19 also increases, the area exposed to the air is also increased, will be the molten salt to generate a large amount of sludge combines with atmospheric CO _2, the molten salt In addition to wasteful consumption, sludge settled in the molten salt tank 19 adheres to the surface of the steel strip 3 and forms a pressing flaw on the surface of the steel strip 3 when passing through the sink roll 20, No. 3 was inevitable for problems such as slippage on the sink roll surface and generation of flaws.

In order to solve the above-mentioned problem, a spray device is provided in place of the molten salt tank as already described in JP-B-53-3167, and a large number of nozzles of the device are applied to the steel strip by atomizing an alkali salt solution. Or JP-A-59-2007
As described in No. 74, after atomizing an alkaline aqueous solution into uniform fine particles, an alkaline aqueous solution is accelerated and sprayed on the surface of stainless steel, etc. In the former case, unevenness in descaling due to non-uniformity of the mist particles is apt to occur, which lowers the quality of the product.

Also, the latter requires a large atomizer,
In addition to the increase in equipment costs, there are many that are blown off when spraying the steel strip in a fine mist and do not adhere to the steel strip, and the consumption of the alkaline aqueous solution has not yet decreased.

[Means for Solving the Problems] According to the present invention, a molten salt coater 5, 5 'for applying a molten salt to a surface of a steel strip 3 with a coating roll 8, 8' is provided at a stage subsequent to the annealing furnace 1, Attaching scraping devices 9, 9 'for scraping a part of the molten salt attached to the coating rolls facing the outer peripheral surfaces of the coating rolls 8, 8', and at the subsequent stage of the molten salt coaters 5, 5 '. Arrange the average tropical 10
The pickling device 15 and the drying device 16 were sequentially installed in the subsequent stage. Further, a gas scraping device is used as the scraping device.

Embodiment The present invention will be described below with reference to an embodiment shown in the drawings.

Referring to FIGS. 1 and 2, reference numeral 1 denotes an annealing furnace, and 2 denotes a cooling device provided at a subsequent stage of the annealing furnace 1. The stainless steel strip or the steel strip 3 processed in the annealing furnace 1 is processed in the next step. Cool to a suitable temperature.

Reference numeral 4 denotes a deflector roll, which is provided downstream of the cooling device 2 and changes the moving direction of the steel strip 3 coming out of the cooling device 2 downward in the vertical direction.

5, 5 'are molten salt coaters disposed on both sides of the steel strip 3 which moves vertically downward.

As shown in FIG. 2, the molten salt coaters 5, 5 'are partially placed in molten salt baths 7, 7' into which molten salts 6 are charged.
The coating rolls 8, 8 'are arranged so as to be immersed in 6'. The coating rolls 8, 8 'are rotated in opposite directions along the moving direction of the steel strip 3 by a driving device (not shown), and the molten salt 6 adhering to the surface thereof is removed by the steel strip 3.
It is designed to be transferred and coated on the surface.

9, 9 'is a molten salt scraping device such as a gas wiper and the nozzle is opened toward the surface of the coating rolls 8, 8', and inert gas from an inert gas source such as argon or helium (not shown). The thickness of the molten salt 6 attached to the surfaces of the coating rolls 8, 8 'is adjusted by adjusting the gas blowing pressure to control the thickness of the molten salt 6 coated on the steel strip 3.

Needless to say, the scraping devices 9, 9 'may be replaced with a mechanical scraping device such as a doctor knife.

Numeral 10 denotes a soaking zone, such as a soaking furnace, a heating or heat-keeping furnace, provided at the subsequent stage of the coater 5, 5 ', and an appropriate furnace is selectively adopted according to the heat-retaining temperature.

The soaking layer 10 is for promoting the reaction between the molten salt 6 coated on the surface of the steel strip 3 and the oxide scale of the steel strip 3, and is maintained at a predetermined temperature for a predetermined time.

And the steel strip 3 that came out of the tropotrope 10 is a deflector roll
Turned vertically upward by 11, 12 and cleaning device 1
After washing with 3, drying in a drier 14, again completely descaling in a known pickling tank 15, drying in a drier 16, and a winder 17
To take up.

Note that the washing device 13 is also a common washing device and also serves as a cooling device, and is not necessarily provided when excessive molten salt does not adhere.In this case, the drying device 14 at the subsequent stage is also omitted, and the washing device 13 is directly omitted. What is necessary is just to guide to the pickling tank 15.

FIG. 3 shows another embodiment of the molten salt coater, in which the molten salt coaters 5, 5 'shown in FIGS. 1 and 2 coat a steel strip 3 which moves downward in the vertical direction. On the other hand, the example shown in FIG. 3 is different in that the steel strip 3 moves substantially horizontally.

Therefore, in this third example, the steel strip 3 can be coated only on one side (lower surface). For example, as shown in FIG. 3, after the lower surface of the steel strip 3 is coated with a molten salt, the steel strip 3 is coated. Turning 180 degrees or twisting steel strip 3
What is necessary is just to coat again by inverting the upper surface and the lower surface.

 Next, the method of the present invention will be described together with its operation.

The steel strip 3 annealed in the annealing furnace 1 is cooled by the cooling device 2 to about 200 ° C. to 900 ° C. in accordance with the subsequent processing temperature. The steel strip 3 cooled to a predetermined temperature is sent to a molten salt coater 5 and coated with a molten salt 6 heated to about 300 ° C. to 500 ° C. in a molten salt tank coater 7, 7 ′.

At this time, the amount of the molten salt 6 attached to the surface of the coating rolls 8, 8 'and sucked up from the molten salt bath 7, 7' is 30 g.
/ m is ² to 100 g / m ² approximately, which is the amount (30g / m ² ~70g / m of molten salt brought out by adhering to the steel strip from a conventional dip-type molten salt bath shown in FIG. 4 This amount is substantially the same as that of ² ), but the thickness of the oxide scale formed on the surface of the steel strip 3 is about 1 μm.
Since this is a degree, the amount of processing is excessive.

However, in the present invention, when the molten salt 6 attached to the coating rolls 8, 8 'is coated on the steel strip 3 as shown in FIG. 3, the molten salt 6 is squeezed at the contact surface A between the coating rolls 8, 8' and the steel strip 3. The surplus is pushed back and accumulates at the entrance B, and the steel strip 3 is coated with a predetermined thickness.

When the amount of the molten salt that is pushed back and accumulates at the inlet portion B becomes unnecessarily large, the amount of the molten salt that passes through the contact surface A increases, and the film thickness coated on the steel strip 3 increases. In this case, the amount of the molten salt attached to the coating rolls 8, 8 'by the scraping devices 9, 9' and sucked up is also limited.

Accordingly, the thickness of the film coated on the steel strip 3 is usually determined by the temperature (viscosity) of the molten salt, the peripheral speed and surface roughness of the coating rolls 8, 8 ', the tension of the steel strip 3, and the thickness of the coating rolls 8, 8' Although it varies depending on the winding angle and the like, the scraping devices 9 and 9 'depend on the amount of the molten salt accumulated at the entrance B.
Optionally, selectively actuates, optimum coating thickness by adjusting the amount of molten salt to be sucked to adhere to the coating rolls 8,8 '(normally about 5g / m ² ~15g / m ² is preferable) Can be controlled.

Thus, the steel strip 3 coated with the molten salt
Is kept at a predetermined temperature for a predetermined time in the soaking zone 10, and the oxide scale reacts with the molten salt to become a compound which is easily dissolved in the subsequent processing solution (acid solution).

Thereafter, the film is washed, dried, pickled, dried and wound on a winder in a conventionally known process.

If the amount of the molten salt coated on the steel strip 3 is excessive in the cleaning step, a large amount of unreacted molten salt will be washed and removed, and the molten salt will be consumed wastefully and a large amount will be consumed. Although a washing water and a neutralizing solution are required, in the present invention, the film thickness of the molten salt coated on the steel strip 3 can be accurately controlled to a necessary and sufficient amount to react with the oxide scale. No waste of molten salt or washing water is consumed.

[Effects of the Invention] As described above, according to the present invention, the molten salt is applied to the surface of the steel strip with a coating roll, and the excessively applied molten salt is controlled by a scraping device so that the film thickness becomes an optimum thickness, Since the amount of the molten salt can be controlled to be necessary and sufficient, the descaling cost can be reduced without wasting the molten salt and washing water. In addition, by using a gas scraping device as the scraping device, even if foreign matter is mixed in the molten salt, the foreign material does not cause a flaw on the steel strip surface when scraping the molten salt.

Further, in the present invention, a soaking zone is disposed at the subsequent stage of the molten salt coater, and the steel strip coated with the molten salt is maintained at a predetermined temperature for a predetermined time to promote the reaction between the molten salt and the oxide scale of the steel strip, thereby promoting acidity at the latter stage. The descaling can be facilitated by making the compound easy to dissolve in the washing solution.

In addition, the molten salt bath can be made much smaller than the conventional dip type, so the molten salt does not react with air in the bath and deteriorates, and the molten salt bath is small. It is possible to reduce the size of the heater for heating and keeping the temperature of the salt, and to reduce the heat radiation from the bath tub, thereby saving energy.

Further, since the molten salt bath is small, a heater for heating and keeping the molten salt charged therein can be downsized, and the heat radiation from the bath is small, so that energy can be saved. .

[Brief description of the drawings]

1 and 2 show an embodiment of the present invention. FIG. 1 is an overall schematic view, FIG. 2 is an enlarged sectional view of a molten salt coater section, and FIG. 3 is another embodiment of the present invention. FIG. 4 is an enlarged sectional view of a molten salt coater portion showing an example, and FIG. 4 is a schematic view showing a conventional example. 1: Annealing furnace, 2: Cooling device 3: Steel strip, 5,5 ': Molten salt coater 6: Molten salt 8,8': Coating roll 9,9 ': Scraping device (wiper) 10: Uniform tropics, 13 ′: Cleaning device 14: Drying device 15: Pickling device, 16: Drying device

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-57-164989 (JP, A) JP-A-6-211394 (JP, A) JP-A-64-242588 (JP, A) JP-A-60-1985 181285 (JP, A) JP-B 53-1733 (JP, B2) (58) Field surveyed (Int. Cl. ⁶ , DB name) C23G 1/00-5/06

Claims (2)

(57) [Claims] A molten salt coater for applying a molten salt to a surface of a steel strip by a coating roll is provided at a stage subsequent to the annealing furnace, and a part of the molten salt adhered to the coating roll facing the outer peripheral surface of the coating roll is provided. A molten salt descaling device, characterized in that a scraping device for scraping is provided, a soaking zone is provided at a stage subsequent to the molten salt coater, and an acid pickling device and a drying device are sequentially installed at a stage after the soaking zone. . 2. The desalting apparatus according to claim 1, wherein the scraping device for scraping off a part of the molten salt attached to the coating roll is a gas scraping device.