EP0225841A1

EP0225841A1 - Continuous pickling apparatus

Info

Publication number: EP0225841A1
Application number: EP86730186A
Authority: EP
Inventors: Kenichi Hiroshima Technical Inst. Yanagi; Toshio Hiroshima Technical Inst. Taguchi; Yuuji Hiroshima Technical Inst. Furuzawa
Original assignee: Mitsubishi Heavy Industries Ltd
Current assignee: Mitsubishi Heavy Industries Ltd
Priority date: 1985-12-09
Filing date: 1986-11-06
Publication date: 1987-06-16
Also published as: JPS62136583A; BR8605680A; ZA869037B; AU6550286A; KR870006237A; AU587506B2

Abstract

The present invention is directed to a continuous pickling apparatus for continuously pickling a material to be pickled, the apparatus being characterized by having an acid tank for receiving therein a pickling liquid at a temperature higher than its boiling point at atmospheric pressure, and by being provided with seal rolls at an outlet and an inlet of the acid tank and the material so as to maintain a high pressure in the acid tank.

Description

2. BACKGROUND OF THE INVENTION

(i) Field of the Invention

The present invention relates to a continuous pickling apparatus for metallic materials, especially steel plates. Further, the present invention relates to a continuous pickling apparatus which is applicable to an electroplating apparatus and an electrolytic cleaning apparatus.

(ii)Description of the Prior Art

One embodiment of a conventional continuous pickling apparatus is shown in Fig. 4. In this drawing, reference numeral 1 is a steel strip, numeral 2 is an acid tank, 3 is an acid liquid, and 4a, 4b, 4c, 4d and 4e are guide rolls.
The steel strip 1 having ordinary temperature is unwound from a payoff reel not shown, and is then caused to run through the acid liquid 3 in the acid tank 2, while a scale formed on the surfaces of the steel strip 4 is pickled out with the acid liquid 3. Afterward, the scale-free steel strip 1 is taken out from the acid tank 2 and is then fed to a subsequent process not shown.
In the continuous pickling apparatus, it is necessary that the steel strip surfaces are in contact with the acid liquid for a certain period of time in order to remove the scale therefrom, and for the sake of this requirement, when the running speed of the steel strip therethrough is high, the elongated acid tank is correspondingly needful.
In recent years, however, it is strongly desired to shorten the acid tank from the viewpoints of equipment cost, installation space and the like. As means for shortening this acid tank, there are a manner of causing the steel strip to pass through a mechanical scale breaker prior to immersing it into the acid tank in order to form fine cracks in the scale and to thereby accelerate the removal of the scale, and a manner of jetting the acid liquid against the steel strip in the acid tank so as to shorten a reaction time, and these manners obtain expected results. Nevertheless, with regard to the acid tank, a length of no less than 50 to 100 m is required, and in the case of such a long acid tank, the high equipment cost and the extensive installation space are necessary. For this reason, it is strongly needed to shorten the acid tank.
Further, as means for curtailing the time necessary for the pickling operation, there is a manner of elevating a temperature of the acid liquid to accelerate a reaction rate. However, the acid liquid boils at about 100°C under atmospheric pressure and a temperature level higher than this boiling point cannot be achieved, which fact indicates that a limit is placed on the acceleration of the reaction rate.

3. OBJECT AND SUMMARY OF THE INVENTION

An object of the invention is to provide a continuous pickling apparatus by which a temperature of an acid liquid is maintained at a temperature higher than its boiling point in order to heighten a reaction rate and to thereby curtail a time necessary for pickling.
In the present invention, as means for accomplishing the above mentioned object, seal rolls are disposed at an inlet and an outlet for a steel strip in an acid tank, and the function of the seal rolls permits maintaining, in the acid tank, a pressure higher than atmospheric pressure, so that the acid liquid can be kept at a temperature higher than the boiling point. That is, the present invention is directed to a continuous pickling apparatus for continuously pickling a material to pickled, the apparatus being characterized by having an acid tank for receiving therein a pickling liquid at a temperature higher than its boiling point at atmospheric pressure, and by being provided with seal rolls at an outlet and an inlet of the acid tank and the material so as to maintain a high pressure in the acid tank.

4. BRIEF DESCRIPTION OF THE DRAWINGS

Fig. l is a schematic sectional view of a pickling apparatus which is one embodiment of the present invention;
Fig. 2 is a schematic sectional view of the pickling apparatus which is another embodiment of the present invention;
Fig. 3 is a graph showing a relation between a temperature of an acid liquid and a ratio of a pickling time; and
Fig. 4 is a schematic sectional view of a conventional pickling apparatus.

5. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

An embodiment of the present invention is shown in Fig. l and 2.
In Fig. l, reference numeral ll is a steel strip, numeral l2 is an acid tank, l3 is an acid liquid, l4a, l4b and l4c are guide rolls, and l5a, l5b, l5c and l5d are seal rolls. The acid tank l2 in Fig. l is of a sealing type, and pairs of the seal rolls l5a, l5b and l5c, l5d are provided at an outlet and an inlet, respectively, of the steel strip ll in the acid tank l2, whereby an opening space between the interior of the acid tank l2 and the outside is minimized and the steel strip ll is allowed to run continuously.
In another embodiment of the present invention shown in Fig. 2, its function is the same as in Fig. l, but constitution is made so that the steel strip 2l may run upward and downward in the acid tank 22. Reference numeral 23 is an acid liquid, numerals 24a, 24b, 24c, 24d, 24e, 24f and 24g are guide rolls, and 25a, 25b, 25c and 25d are seal rolls.
According to the pickling apparatus of the present invention, a high pressure can be kept in the acid tank, even while the steel strip is running, so that the acid liquid can be maintained at a temperature higher than its boiling point at atmospheric pressure.
For example, a temperature of the acid liquid is at most about 100°C at atmospheric pressure, but according to the present invention, a temperature of about 150°C can be easily realized at a pressure of 4 kg/cm²G. Results of experiments which the inventors of the present application have conducted indicate that as the temperature of the acid liquid is elevated, the reaction rate is heightened as shown in Fig. 3, whereby a pickling period of time is curtailed. As a result, the length of the acid tank is shortened advantageously. In Fig. 3, the abscissa axis and the ordinate axis represent the temperature of the acid liquid and the ratio of the pickling time, respectively, and when the pickling time at a conventional liquid temperature of 80°C as regarded as 100%, the pickling time at 150°C is about 60% to 70%.
As described above in detail, the continuous pickling apparatus of the present invention has the acid tank for receiving therein the pickling liquid at a temperature higher than the boiling point at atmospheric pressure and is equipped with the seal rolls at the outlet and the inlet of the acid tank and the material to be pickled. Therefore, a pressure in the acid tank can be maintained at a higher level, and thus the acid liquid can have a higher temperature. In consequence, as functional effects of the present invention, the pickling time can be curtailed, and thus the length of the acid tank can be shortened conveniently.

Claims

A continuous pickling apparatus for continuously pickling a material to be pickled, said apparatus being characterized by having an acid tank for receiving therein a pickling liquid at a temperature higher than its boiling point at atmospheric pressure, and by being provided with seal rolls at an outlet and an inlet of said acid tank and said material so as to maintain a high pressure in said acid tank.