JPH111787A - Pickling treatment method of steel strip and its device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a pickling treatment time and to improve productivity without remodeling a large-scale of pickling bath by preheating a steel strip plate at the time of pickling removing an oxidized scale on the surface of the steel strip plate after hot rolling. SOLUTION: The temperature of the carried steel strip plate 1 is continuously measured with the measuring device 18 of the temperature of the steel strip plate at the inlet side of the induction heating device 13 arranged in the inlet side of the pickling bath 4, and the output of the induction heating device 13 is regulated with an induction heating controller 19 in accordance with this result. Thus, the steel strip plate 1 is pickled within the pickling bath 4 after preheating up to the prescribed temperature. A hot water tank or a direct fire burner is also used as the preheating device. The length of the pickling bath used for the temperature rising of the steel strip plate 1 is not required compared with the conventional pickling bath, the effective time required for pickling is reduced that much more, and the operation increasing the line speed is allowed. Therefore, when the scale of the equipment is the same, productivity is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pickling treatment of a strip steel sheet which removes oxide scale on the surface of the strip steel sheet by unwinding the strip steel sheet after hot rolling and washing it with a solution such as nitrate or sulfate. The present invention relates to a method and a pickling apparatus.

[0002]

2. Description of the Related Art A typical example of a pickling apparatus for a strip steel sheet is as follows.
As shown in FIG. 4, the steel strip 1 is conveyed from left to right in the figure. The pickling tank 4 is usually divided into two or more tanks by the partition wall 3 in the pickling tank. A strip steel sheet holding roll 2 is installed on the front surface of the pickling tank 4, a pickling tank exit side squeezing roll 5 is installed on the rear surface, and a rinsing tank 6 is further provided on the rear surface. A rinsing tank 6 has a squeezing roll 7 on the rear side of the rinsing tank 6, a dryer 8 is provided on the rear side, and a strip steel sheet holding roll 9 is provided.

[0003] In FIG. 4, the strip steel plate 1 is firstly stripped of oxidized scale adhered to its surface by a pickling treatment liquid 11 in a pickling tank 4, and the pickling treatment liquid adhered to the surface is removed from the pickling tank. It is squeezed by the exit-side squeezing roll 5. Further, the acid solution remaining on the surface is removed from the rinsing sink roll 10 in the rinsing tank 6.
It is washed away by the washing liquid 12 by passing it under, and finally squeezed by the rinsing roll 7 on the rinse outlet side, and then dried by the drier 8.

[0004] The pickling treatment carried out by unwinding the steel strip as described above usually requires a large-scale facility, so that it has been a problem to improve the efficiency of the pickling treatment conventionally. Conventional techniques relating to pickling treatment efficiency include (method A) setting the temperature of the pickling treatment liquid as high as possible, and (method B) pickling treatment liquid as typified by jet pickling. Spraying on the surface of a steel sheet can reduce the processing time.

[0005]

Setting the temperature of the pickling treatment solution in (Method A) as high as possible is very effective because the pickling treatment is a chemical reaction. Therefore, conventionally, a heating device such as a heat exchanger has been installed in a pickling tank or inside a processing liquid circulation pipe to control the temperature of the pickling treatment liquid.

Since the temperature of the pickling solution is an important factor, it is already a general value to control the temperature to 80 ° C. to 95 ° C. If the temperature is to be further raised, the pickling solution will boil locally. Alternatively, a large amount of fumes are generated to deteriorate the environment, or the basic unit of the pickling treatment liquid is deteriorated due to evaporation, or the constituent materials of the pickling tank are deteriorated due to the high-temperature treatment liquid, and the pickling treatment liquid is circulated on the pump suction side. It is very likely to cause various problems such as cavitation. Therefore, it is not realistic to set the processing liquid management temperature higher than this.

[0007] As an example of the technique for shortening the processing time by spraying the pickling treatment liquid of (Method B) onto the steel sheet surface,
There is JP-A-63-192882. This is a combination of a method of spraying a jet of an acid solution onto the material to be pickled without immersing the material to be pickled in an acid solution, and a method of immersing the material in a pickling treatment solution to perform pickling. And carrying out pickling. However, JP-A-63-1
In the method disclosed in Japanese Patent No. 92882, it is necessary to constantly circulate a large amount of the pickling solution at a high pressure, which requires not only a large-capacity acid-resistant pump and a large circulation tank, but also in some cases the internal pressure of the pickling tank itself. Intense strength and structure are required, and complicated and large-scale equipment is required.

Therefore, the pickling treatment equipment is the most dangerous to handle and cannot reduce the scale of the acid solution treatment equipment itself, which is poor in maintenance. It only increases, and is not suitable for remodeling existing facilities. The present invention solves the problems related to these conventional techniques, and does not harm the environment, does not cause instability of operation such as cavitation of a pump, does not impede the constituent materials of the pickling tank, and has a simple structure. It is an object of the present invention to provide an efficient pickling method and an apparatus which can be easily maintained and maintained by a structure and can be easily remodeled.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a pickling method for removing an oxide scale on the surface of a strip by unwinding the strip after hot rolling and washing with a pickling treatment solution.
A pickling treatment method for a strip steel sheet characterized by shortening the pickling treatment time by preheating the strip steel sheet in advance, and a strip for shortening the pickling treatment time by preheating the strip steel sheet in advance. A pickling treatment device for a strip steel plate, comprising a steel plate preheating device.

FIG. 5 shows an example of the relationship between the pickling temperature and the required pickling time. The pickling characteristics vary greatly depending on operating conditions such as the composition of the strip steel sheet, the winding temperature, and the passing speed of the strip steel sheet. However, generally, the higher the pickling temperature, the shorter the time required for pickling. Therefore, it is preferable to perform pickling at a temperature as high as possible from the viewpoint of pickling efficiency. On the other hand, when the pickling temperature is high, fumes are generated and the environment is easily hindered. In order to induce problems such as corrosion deterioration of the tank body and piping system,
Generally, the temperature is controlled in the range of 0 to 90 ° C. Also, as can be seen from the graph of FIG. 5, the required pickling temperature is about four times longer at a pickling temperature of 70 ° C. or lower than at 80 ° C. or higher, and the processing speed becomes extremely slow. I understand.

On the other hand, FIG. 6 shows a temperature change of the steel strip when the steel strip at room temperature is immersed in a pickling treatment solution at 90 ° C. In FIG. 6, the horizontal axis represents the elapsed time, and the vertical axis represents the temperature of the steel material (steel strip). The curve 16 in the figure indicates the thick material temperature distribution, 1
7 is a thin material temperature distribution. Although this also varies slightly depending on various conditions, the steel temperature must be equal to or higher than the standard temperature of 70 ° C. (15) and an efficient pickling process can be performed.
It takes ten and several seconds for thin materials and twenty and several seconds for thick materials.

In this case, the pickling time of 20 seconds is a time taken to simply raise the temperature of the strip steel plate by 30 m for a pickling tank in an equipment having a strip steel sheet conveying speed of 100 mpm and an effective pickling tank length of 100 m. Will be done. The present inventor has paid attention to this point, and invented a method for improving the productivity of the entire pickling equipment by effectively utilizing the entire pickling tank used only for raising the temperature of the steel strip. In other words, by preheating the strip steel sheet temperature immediately before entering the pickling tank to 40 to 95 ° C., it is possible to effectively contribute to the pickling treatment from the forefront portion of the pickling tank.

[0013]

1 to 3 show an embodiment of the present invention. This will be described below with reference to FIG. FIG. 1 shows an example in which an induction heating device 13 is provided as a preheating device for a steel strip. The steel strip 1 conveyed from the left side of the drawing is heated to 80 to 90 ° C. by the induction heating device 13 installed on the pickling tank entrance side.
After being preheated, it is pickled in the pickling tank 4. In this case, as compared with the conventional pickling treatment, the length of the pickling tank used for raising the temperature of the strip steel plate 1 is not required, and the effective required pickling time can be shortened accordingly. That is, it is possible to start a business by increasing the line speed by the reduced amount of the pickling time, thereby improving productivity.

FIG. 2 shows an example in which a hot water tank 14 is used as a strip steel plate preheating apparatus. The basic principle is exactly the same as that of the induction heating shown in FIG. The use of heat has made it possible to further save energy. Although not shown, a direct fire burner or a preheating spray header may be used instead of the induction heating device or the hot water tank as the steel strip preheating device.

[0015] The temperature of the steel strip before the pickling treatment greatly varies depending on the elapsed time after the hot rolling. In addition, the position of the steel strip,
That is, it changes greatly depending on the outer circumference, inner circumference, and the like of the coil. In order to obtain a constant pickling efficiency irrespective of such temperature change of the steel strip, the temperature of the steel strip is continuously measured by the steel strip temperature measuring device 18 at the entrance of the preheating device as shown in FIG. ,
Based on this result, the efficiency of the pickling process can be further improved by adjusting the output of the preheating device such as the induction heating device by the induction heating control device 19.

[0016]

As described above, according to the present invention, it is possible to improve the productivity by 20 to 30% as compared with the conventional equipment if the equipment is of the same scale. In addition, it was possible to significantly improve productivity without remodeling a large-scale pickling tank.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first embodiment of a pickling apparatus according to the present invention;

FIG. 2 is a view showing a second embodiment of the pickling apparatus according to the present invention;

FIG. 3 is a view showing a third embodiment of the pickling apparatus according to the present invention;

FIG. 4 is a diagram showing an example of a typical pickling apparatus according to the related art;

FIG. 5 is a diagram showing a relationship between a pickling temperature and a required pickling time;

FIG. 6 is a diagram showing an average temperature distribution of a steel strip in a pickling process.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Strip steel plate 2 Strip steel plate holding roll 3 Partition wall in pickling tank 4 Pickling tank 5 Pickling tank exit side squeezing roll 6 Rinse tank 7 Rinse exit side squeezing roll 8 Dryer 9 Strip steel sheet holding roll 10 Rinse sink roll 11 Acid Cleaning treatment liquid 12 Cleaning liquid 13 Induction heating device 14 Hot water tank 15 Standard temperature 16 Thick material temperature distribution 17 Thin material temperature distribution 18 Strip steel plate temperature measuring device 19 Induction heating control device

Claims (4)

[Claims] In a pickling method for removing an oxidized scale on the surface of a strip steel sheet by unwinding the strip steel sheet after hot rolling and washing the strip steel sheet with a pickling treatment solution, the pre-heating of the strip steel sheet is performed. A pickling treatment method for a strip steel sheet, characterized by shortening a washing treatment time. 2. A pickling apparatus that unwinds a strip of steel after hot rolling and removes oxidized scale on the surface of the strip of steel by washing with a pickling treatment solution, thereby preheating the strip of steel by pickling. A pickling treatment apparatus for a strip steel sheet, comprising a strip steel sheet preheating device for shortening a washing time. 3. The pickling apparatus for a steel strip according to claim 1, further comprising an induction heating device, a hot water tank, or an open flame burner as the steel strip preheating device. 4. An apparatus for pickling a steel strip comprising the steel strip preheating apparatus according to claim 2, wherein the temperature of the steel strip on the inlet side of the steel strip preheating apparatus is measured, and based on the measurement result, the steel strip preheating is performed. A pickling treatment method for a strip steel sheet, wherein a preheating temperature of the apparatus is automatically controlled.