JP2007239092A - Rinsing equipment for pickled steel sheet and rinsing method therefor - Google Patents

Abstract

The present invention provides a rinsing equipment for a pickled steel sheet and a rinsing method for the same that can prevent the occurrence of yellowing by spraying a cleaning liquid without causing a time lag.
A main pipe connected to a water supply tank is extended to an upper portion of a rinsing tank, and a main nozzle unit having a plurality of injection nozzles is attached to the tip of the main pipe. A first mixer 8 connected to a yellowing prevention agent storage tank 9 is provided in the main pipe 4 close to the main nozzle unit 3. When the plate passing speed is greatly reduced, the pump 61 is started and a yellowing inhibitor is added to the water in the main pipe 4. Since the 1st mixer 8 is arrange | positioned in the vicinity of the main nozzle unit 3, the timing of the washing | cleaning liquid injection with which the yellowing prevention agent was mixed does not delay.
[Selection] Figure 1

Description

The present invention relates to a rinsing facility for a pickled steel sheet disposed after a pickling tank for the steel sheet and a rinsing method therefor.

In a conventional hot-rolled steel sheet pickling apparatus, as shown in Patent Document 1, for example, a rinse facility is disposed after the pickling tank. In this rinsing equipment, the hot-rolled steel sheet pickled in the pickling tub is sprayed with rinsing water from the spray nozzle while passing between the spray nozzles arranged facing the rinsing tub. The pickling solution and pickling product (smut) adhering to the surface are removed. However, when the hot-rolled steel sheet is passed through at a low speed of about 0 to several tens mpm, the time of exposure to air becomes long, and thus a surface discoloration called yellowing occurs.

Therefore, in order to prevent the occurrence of such yellowing, there is a rinsing facility in which a cleaning liquid in which a yellowing inhibitor is mixed with water is jetted from a jet nozzle as shown in FIG. In this rinsing equipment, a nozzle unit 30 having a large number of injection nozzles 2 is provided above the rinsing tank 1.
Are arranged in plural. The nozzle unit 30 is connected to the cleaning liquid tank 5 through a pipe 40. The cleaning liquid tank 5 is filled with a cleaning liquid mixed with an anti-yellowing agent, and the cleaning liquid in the cleaning liquid tank 5 is pumped by the pump 6 to the nozzle unit 30 via the pipe 40, and is pickled from the spray nozzle 2 to the pickled steel sheet 7. The cleaning liquid is sprayed on. In addition, although the injection nozzle 2 is arrange | positioned on the front and back both surfaces of the pickled steel plate 7, one illustration is abbreviate | omitted in the figure.

In the rinsing equipment, when the high-speed pickled steel sheet 7 is decelerated to a low speed, a cleaning liquid injection command is issued from the control device, but the cleaning liquid tank 5 is separated from the injection nozzle 2 and is connected to the piping 4.
When 0 is long, there is a time lag of several seconds from the command to the injection of the cleaning liquid, which causes yellowing of the pickled steel sheet.
In addition, when a pickled steel sheet having a thickness of 9 mm or more is mail-ordered by a push-pull method, yellowing occurs due to a time lag even at a plate speed of several tens to 100 mpm.
Furthermore, it is also possible today to change the plate passing speed with a high acceleration / deceleration ratio of several 10 to 70 mpm / sec by improving the control technology. Even when the plate passing speed is changed suddenly in this way, the cleaning liquid injection There is a problem that yellowing occurs due to a delay in the response.
Depending on the length of the time lag at the time of transition from high speed to low speed and the acceleration / deceleration ratio to be set, the yellowing portion of the steel plate to be pickled becomes long, so a large number of cleaning liquid injection nozzles are arranged in the traveling direction of the steel plate. In order to avoid yellowing efficiently, it is necessary to apply a concentration gradient to the yellowing inhibitor concentration in the traveling direction of the steel sheet for the cleaning liquid applied from a large number of spray nozzles arranged in the traveling direction of the steel sheet. there were.

The delay of the cleaning liquid injection timing as described above can be solved by arranging the cleaning liquid tank 5 at a close distance of the rinsing equipment. However, the equipment restrictions such as the presence of an electric motor, the maintenance space, and the introduction of the yellowing prevention agent are possible. From the standpoint of securing space, the cleaning liquid tank 5
It may be difficult to place the rinsing equipment close to the rinsing equipment, and even if the cleaning tank 5 is arranged at a close distance, a certain amount of piping is required to the rinsing equipment and is not in time for a high acceleration / deceleration ratio. A case occurs.
In addition, when a large number of anti-yellowing agent spray nozzles are arranged in the direction of travel of the steel plate or when a concentration gradient is applied to the anti-yellowing agent sprayed from a number of spray nozzles, one type of yellowing prevention can be prevented with one cleaning liquid tank. Only the cleaning agent having the agent concentration can be prepared, and when switching the yellowing inhibitor concentration of the cleaning liquid, a time lag of several tens of seconds to several minutes occurs until the predetermined concentration is reached. In order to avoid this, a plurality of cleaning liquid tanks are required in order to always prepare a plurality of anti-yellowing agent concentrations as in Patent Document 2, and in this case, there is a problem of an increase in capital investment and a necessary space. Ensuring and constraints are important issues.
Japanese Patent Laid-Open No. 5-125573 JP 2006-28574 A

In view of the above-described conventional problems, the present invention can prevent the occurrence of yellowing by injecting a cleaning liquid without causing a time lag, does not require equipment investment such as installation of a large number of tanks, and is limited in space. It is an object of the present invention to provide a rinsing facility and a rinsing method for a pickled steel sheet with a low content.

The rinse equipment of the pickled steel sheet of the present invention made to solve the above problems
In the rinse equipment for spray pickled steel sheets,
In the middle of the main pipe for supplying water to the main nozzle unit of the rinse tank and in the vicinity of the main nozzle unit, a first mixer for mixing the yellowing inhibitor with the water in the main pipe is provided. is there.

In the above-described invention, branching from the upstream main pipe of the first mixer, extending the branch pipe to the rinse tank on the downstream side in the plate passing direction of the main nozzle unit, at the tip of the branch pipe,
After providing a sub-nozzle unit having a plurality of injection nozzles,
A second mixer for mixing the yellowing inhibitor with water in the main pipe can be provided in the main pipe upstream of the branch point where the branch pipe branches.

Further, in the above-described invention, branching from the main pipe on the upstream side of the first mixer, extending the branch pipe to the rinse tank on the downstream side in the plate passing direction of the main nozzle unit, at the tip of the branch pipe, After providing a sub-nozzle unit having a plurality of injection nozzles,
A second mixer for mixing the yellowing inhibitor with water in the branch pipe can be provided in the branch pipe branched from the main pipe.

Furthermore, in the rinsing equipment for pickled steel sheets, the main nozzle unit can be disposed in the rinsing tank on the upstream side in the sheet passing direction, and the sub nozzle unit can be disposed in the rinsing tank on the downstream side in the sheet passing direction.

The method for rinsing a pickled steel sheet according to the present invention uses the rinsing equipment for the pickled steel sheet according to claim 1 to yellow the water in the vicinity of the main nozzle unit while feeding water to the main nozzle unit of the rinsing tank. In the first mixer for mixing the inhibitor with water in the main pipe, water and the yellowing inhibitor are mixed to prepare a cleaning liquid and sprayed from the main nozzle unit spray nozzle.

Moreover, the rinse method of the pickled steel sheet of this invention uses the rinse equipment of the pickled steel sheet of Claim 2,
On the upstream side in the plate passing direction, from the injection nozzle of the main nozzle unit, the second mixer and the first
While spraying a high-concentration cleaning liquid in which a yellowing inhibitor is mixed twice by a mixer,
On the downstream side in the plate passing direction, a low-concentration cleaning liquid in which a yellowing inhibitor is mixed is jetted from the jet nozzle of the sub nozzle unit by the second mixer.

Moreover, the rinse method of the pickled steel sheet of this invention uses the rinse equipment of the pickled steel sheet of Claim 3,
On the upstream side in the plate passing direction, the cleaning liquid in which the yellowing inhibitor is mixed by the first mixer is injected from the injection nozzle of the main nozzle unit,
On the downstream side of the rinsing tank in the plate passing direction, the cleaning liquid in which the yellowing inhibitor is mixed by the second mixer is jetted from the jet nozzle of the sub nozzle unit.

Furthermore, the rinse method of the pickled steel sheet of the present invention uses the rinse equipment for the pickled steel sheet according to claim 4,
In the rinsing tank on the upstream side in the plate passing direction, a cleaning liquid with a higher concentration of yellowing inhibitor is sprayed from the main nozzle unit,
In the rinsing tank on the downstream side in the sheet passing direction, a cleaning liquid having a reduced concentration of the yellowing inhibitor is jetted from the sub nozzle unit.

In the invention according to claim 1, since the first mixer for mixing the yellowing inhibitor is provided in the main pipe in the vicinity of the injection nozzle, no time lag occurs even if the distance from the water supply tank to the injection nozzle becomes long. The occurrence of yellowing can be prevented by spraying the cleaning liquid, and the yellowing inhibitor concentration of the cleaning liquid can be arbitrarily set and changed without providing a plurality of cleaning tanks for different yellowing inhibitor concentrations.
The invention according to claim 2 injects a cleaning liquid having a high concentration of yellowing prevention agent from the injection nozzle of the main nozzle unit, and injects the cleaning liquid from the injection nozzle of the sub nozzle unit with a low concentration of yellowing prevention agent. The yellowing inhibitor concentration of any of a plurality of cleaning liquids can be set and changed without providing a plurality of cleaning tanks for different anti-change agent concentrations.
According to a third aspect of the present invention, a plurality of different yellowing inhibitor concentrations are ejected by spraying cleaning liquids each independently adjusting the concentration of the yellowing inhibitor from the injection nozzle of the main nozzle unit and the injection nozzle of the sub nozzle unit. Even if the cleaning tank is not provided, it is possible to arbitrarily set and change the yellowing inhibitor concentration of a plurality of cleaning liquids.
The invention according to claim 4 rinses the pickled steel sheet by injecting a plurality of anti-yellowing agent concentration cleaning solutions in a subdivided rinsing tank without having a plurality of anti-yellowing agent concentration cleaning tanks. can do.

In the invention according to claim 5, even when the sheet passing speed is low, the pickling steel sheet is optional even if it does not include a plurality of cleaning tanks for each yellowing inhibitor concentration without delaying the timing of the cleaning liquid injection. The cleaning liquid can be sprayed with a cleaning liquid having a yellowing inhibitor concentration.
The invention according to claim 6 injects the cleaning liquid to which the yellowing inhibitor is added at a high concentration on the upstream side in the plate passing direction without providing a plurality of cleaning tanks for each concentration of the yellowing inhibitor, and on the downstream side in the plate passing direction. In this case, the pickling steel sheet can be rinsed with the yellowing inhibitor concentration of any of a plurality of cleaning liquids by spraying a cleaning liquid in which the yellowing inhibitor is added at a low concentration.
The invention according to claim 7 injects a cleaning liquid that independently adjusts the concentration of the yellowing inhibitor on the upstream side and the downstream side in the plate passing direction without providing a plurality of cleaning tanks for each yellowing inhibitor concentration. Thus, the pickled steel sheet can be rinsed with the concentration of the yellowing inhibitor in any of a plurality of cleaning liquids.
According to the eighth aspect of the present invention, the concentration of the yellowing inhibitor is increased in the rinsing tank on the upstream side in the sheet passing direction without providing a plurality of washing tanks for each yellowing inhibitor concentration, and the yellowing is performed in the downstream rinsing tank. By injecting the cleaning liquid having a reduced concentration of the inhibitor, it is possible to prevent the yellowing of the pickled steel sheet by injecting a plurality of cleaning liquids having any of the yellowing inhibitor concentrations.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a view showing a rinse facility for pickled steel sheets according to the first embodiment of the present invention. In the figure, 51 is a water supply tank for purified water, industrial water, etc. in which no yellowing inhibitor is mixed. A main pipe 4 is connected to the water supply tank 51, and the main pipe 4 extends to the upper part of the rinse tank 1. A main nozzle unit 3 having a plurality of injection nozzles 2 is attached to the tip of the main pipe 4, and water is pumped to the injection nozzles 2 by a pump 6. The main pipe 4 in the vicinity of the main nozzle unit 3, that is, the main pipe 4 in a part as close to the main nozzle unit 3 as possible.
The first mixer 8 is provided, and the yellowing inhibitor is pumped from the yellowing inhibitor storage tank 9 through the pump 61, and the yellowing inhibitor is added to the water in the main pipe 4 by the first mixer 8. Are mixed.

In the above rinsing equipment, the pump 6 is operated during high-speed plate feeding, and water is sprayed from the spray nozzle 2 onto the pickled steel sheet. When the plate passing speed is reduced to a low speed of about 10 to several tens of mpm, the control device (not shown) activates the pump 61 to prevent yellowing of the water in the main pipe 4 via the first mixer 8. Agent is added. Since the first mixer 8 is disposed in the vicinity of the main nozzle unit 3, the cleaning liquid mixed with the yellowing inhibitor can be injected from the injection nozzle 2 without causing a time delay. Therefore, yellowing does not occur in the pickled steel sheet.

In FIG. 2, the rinse equipment of the pickled steel plate which is 2nd Embodiment is shown.
In this embodiment, the main pipe 4 extends to the upper part of the rinsing tank 1 on the upstream side in the sheet passing direction. A main nozzle unit 3 having a plurality of injection nozzles 2 at the tip of the main pipe 4
Is attached to the main pipe 4 close to the main nozzle unit 3. The first mixer 8 is connected to the yellowing prevention agent storage tank 9 via a pump 61. A branch pipe 41 is branched from the main pipe 4 on the upstream side of the first mixer, and extends to the upper part on the downstream side in the sheet passing direction of the rinse tank 1. A sub nozzle unit 31 having a plurality of injection nozzles 21 is provided at the tip of the branch pipe 41. Further, the branch pipe 41
A second mixer 81 for mixing the yellowing inhibitor with water in the main pipe 4 is provided in the main pipe 4 on the upstream side of the branch point 42 where the water is branched. The second mixer 81 is connected to a common anti-yellowing agent storage tank 9 via a pump 62.

In the rinsing facility of the second embodiment, the main nozzle unit 3 is pumped with high-concentration cleaning liquid in which the yellowing inhibitor is mixed twice with the water in the main pipe 4 by the second mixer 81 and the first mixer 8. The high-concentration cleaning liquid is ejected from the ejection nozzle 2. A low-concentration cleaning liquid in which a yellowing inhibitor is mixed by only the second mixer 81 is pumped to the sub nozzle unit 31 on the downstream side in the sheet passing direction, and this low-concentration cleaning liquid is sprayed from the spray nozzle 21. In this way, by increasing the concentration of the yellowing inhibitor on the upstream side in the threading direction and lowering the concentration on the downstream side, injection is ensured to minimize the amount of yellowing agent used and ensure that yellowing occurs. Can be prevented.

In FIG. 3, the rinse equipment of the pickled steel plate which is 3rd Embodiment is shown.
In this rinse facility, the rinse tank 1 is divided into a plurality of rinse tanks 11, 12, and 13. The main pipe 4 extends to the upper part of the rinse tank 11 on the upstream side in the sheet passing direction, and a main nozzle unit 3 having a plurality of injection nozzles 2 is attached to the tip of the main pipe 4, and is attached to the main pipe 4 close to the main nozzle unit 3. The 1st mixer 8 connected to the yellowing prevention agent storage tank 9 is arrange | positioned.

A branch pipe 41 branches from the main pipe 4 on the upstream side of the first mixer 8 and extends to the upper part of the rinsing tank 12 on the downstream side in the sheet passing direction. A sub nozzle unit 31 having a nozzle 21 is provided. The branch pipe 41 is provided with a second mixer 81 for mixing the yellowing inhibitor with water in the branch pipe 41. Second mixer 8
1 is connected to a common anti-yellowing agent storage tank 9 via a pump 62.

In the rinsing equipment of the third embodiment, a cleaning liquid in which a yellowing inhibitor is mixed with water in the main pipe 4 by the first mixer 8 is injected into the injection nozzle 2 of the main nozzle unit 3 on the upstream side in the plate passing direction. Pumped. The cleaning liquid mixed with the yellowing prevention agent by the second mixer 81 is pumped to the injection nozzle 21 of the sub nozzle unit 31 on the downstream side in the sheet passing direction. By making the pump 62 smaller than the pump 61 and making the yellowing inhibitor delivery amount of the pump 62 smaller than that of the pump 61, a high concentration cleaning liquid is jetted on the upstream side in the plate passing direction, and the downstream side Can be used to inject a low-concentration cleaning liquid. Thereby, the amount of yellowing inhibitor used can be saved and the occurrence of yellowing can be reliably prevented.

In the rinsing equipment of FIG. 4, the main nozzle unit 3 and the sub nozzle unit 31 are arranged in the rinsing tanks 11 and 12 respectively. By configuring the rinsing equipment in this way, the optimum in the respective rinsing tanks 11 and 12. Can take measures to prevent yellowing.
The sub nozzle unit 31 can be disposed so as to straddle the rinsing tanks 11, 12 as shown in FIG. 4, or the main nozzle unit 3 can be disposed so as to straddle the rinsing tanks 11, 12. it can.

As described above, even when rinsing equipment is configured, the distance from the first mixer 8 and the second mixer 81 to the main nozzle unit 3 and the sub nozzle unit 31, the pressure loss of the main pipe 4 and the branch pipe 41, and the yellowing prevention agent Depending on the use frequency of itself, the leakage of cleaning liquid from the injection nozzles 2 and 21 when the injection is stopped, the responsiveness of the pumps 61 and 62, the first mixer 8 and the second mixer 81, etc.
The yellowing inhibitor concentration may change at the beginning of the cleaning liquid injection. Therefore, in order to solve such a problem, it is desirable to adjust the concentration of the yellowing inhibitor using a control device such as a computer.

That is, as shown in FIG. 5, the pH value on the surface of the pickled steel sheet is 4 to 6, particularly the b value which is the yellowing index in the vicinity of 5, and yellowing is likely to occur. Need to pass through. Therefore, as shown in FIGS. 6 and 7, it is desirable to connect the control device 10 to the pumps 61 and 62 to increase the supply amount of the yellowing inhibitor at the beginning of the injection and to make the pH value rapidly 7. . Thus, by increasing the supply amount of the yellowing inhibitor, as shown in case 3 of FIG.
It was possible to prevent the yellowing by passing through the yellowing region of the material in a short time. Case 3
Is an embodiment in which the concentration of the cleaning liquid on the upstream side during passage is higher than that on the downstream side, Case 2 is an embodiment in which the concentration of the cleaning liquid on the upstream side and downstream side when passing is the same, and Case 1 is yellowing prevention It is a comparative example when the agent is not used. In case 1, yellowing tends to occur because the time for passing through the pH 4-6 region is long.

In addition, it is desirable that the initial addition amount of the yellowing inhibitor is 2 to 5 times that in the steady state, and the addition time is 5 to 10 seconds. If the addition amount is less than twice, the effect of increasing the yellowing inhibitor does not become obvious. on the other hand,
This is because if it exceeds 5 times, the concentration of the cleaning solution is not stable until it returns to a steady state. Moreover, if the addition time is less than 5 seconds, the effect of adding the yellowing inhibitor is weak, whereas if it exceeds 10 seconds, the concentration of the cleaning solution is not stable.
By managing the concentration of the yellowing inhibitor in the cleaning liquid as described above, it is possible to rinse the pickled steel sheet 7 without generating yellowing by saving the amount of yellowing inhibitor used.
In the meantime, in the vicinity of the rinsing equipment and in the vicinity of the nozzle unit, the standard is 0.5 m or more and 50 m or less from the nozzle injection port. If the width is less than 0.5 m, the pickled steel sheet that is passed through usually has a width of more than 0.5 m to 2 m, so that the total width of the steel sheet is not enough, and if it exceeds 50 m, it takes too much time to reach the injection nozzle. Does not appear. If it is 30 m or less, it is still preferable, and if it is within 5 m, there is no problem.
In the present invention, one water supply tank 51 is sufficient. However, when it is necessary to inject pure water without adding a yellowing inhibitor or the like, and industrial water only to the pickled steel sheet, a plurality of water supply tanks 51 are prepared. Some may be dedicated to water injection. Further, water can be supplied directly from the water supply source to the mixer without using the water supply tank 51 as long as the water supply amount, the water supply pressure, and the like can be secured stably.
In addition, the yellowing inhibitor stored in the anti-yellowing agent storage tank 9 is stored in the state of a stock solution transported from the manufacturer, but is stored in advance at a concentration that can be easily adjusted by diluting with water or the like. It does not matter. In the present invention, one anti-yellowing agent storage tank 9 is sufficient. However, when a plurality of types of anti-yellowing agents are used or when other additives are used, the anti-yellowing agent storage tank 9 is used. A plurality of tanks corresponding to 9 may be provided.

It is a schematic block diagram of the rinse installation of 1st Embodiment. It is a schematic block diagram of the rinse installation of 2nd Embodiment. It is a schematic block diagram of the rinse installation of 3rd Embodiment. It is a schematic block diagram of the rinse installation of 4th Embodiment. It is a graph which shows the relationship between pH value and b value. It is a schematic block diagram of the rinse equipment connected to the control apparatus. It is explanatory drawing which shows the change of pH value at the time of managing the density | concentration of a yellowing prevention agent. It is a schematic block diagram of the conventional rinse equipment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rinse tank, 2 injection nozzle, 3 main nozzle unit, 4 main pipe, 8 1st mixer, 9 yellowing prevention agent storage tank, 51 water supply tank, 61 pump

Claims (8)

In the rinse equipment for spray pickled steel sheets,
Pickling characterized in that a first mixer is provided in the middle of the main pipe for supplying water to the main nozzle unit of the rinsing tank and in the vicinity of the main nozzle unit for mixing the yellowing inhibitor with the water in the main pipe. Steel sheet rinsing equipment. A sub-nozzle that branches off from the main pipe on the upstream side of the first mixer, extends the branch pipe to the rinse tank on the downstream side in the plate passing direction of the main nozzle unit, and has a plurality of injection nozzles at the tip of the branch pipe In addition to providing a unit,
The rinse of the pickled steel sheet according to claim 1, wherein a second mixer for mixing a yellowing inhibitor with water in the main pipe is provided on the main pipe upstream from the branch point where the branch pipe branches. Facility. A sub-nozzle that branches off from the main pipe on the upstream side of the first mixer, extends the branch pipe to the rinse tank on the downstream side in the plate passing direction of the main nozzle unit, and has a plurality of injection nozzles at the tip of the branch pipe In addition to providing a unit,
The rinsing equipment for pickled steel sheets according to claim 1, wherein a second mixer for mixing the yellowing inhibitor with water in the branch pipe is provided in the branch pipe branched from the main pipe.   4. The rinsing equipment for pickled steel sheet, wherein the main nozzle unit is disposed in the rinsing tank upstream of the sheet passing direction, and the sub nozzle unit is disposed in the rinsing tank downstream of the sheet passing direction. Rinse equipment for pickled steel sheets as described in 1. In order to mix the yellowing inhibitor with the water in the main pipe in the middle of the water supply to the main nozzle unit of the rinsing tank and in the vicinity of the main nozzle unit using the rinse equipment for the pickled steel sheet according to claim 1 A method for rinsing a pickled steel sheet, wherein water and an anti-yellowing agent are mixed in the first mixer to prepare a cleaning liquid and spray it from a main nozzle unit spray nozzle. Using the rinse equipment for pickled steel sheet according to claim 2,
On the upstream side in the plate passing direction, from the injection nozzle of the main nozzle unit, the second mixer and the first
While spraying a high-concentration cleaning liquid in which a yellowing inhibitor is mixed twice by a mixer,
A method for rinsing a pickled steel sheet, characterized in that, on the downstream side in the sheet passing direction, a low-concentration cleaning liquid in which a yellowing inhibitor is mixed by a second mixer is sprayed from the spray nozzle of the sub nozzle unit. Using the rinse equipment for pickled steel sheet according to claim 3,
On the upstream side in the plate passing direction, the cleaning liquid in which the yellowing inhibitor is mixed by the first mixer is injected from the injection nozzle of the main nozzle unit,
A method for rinsing a pickled steel sheet, characterized in that, on the downstream side of the rinsing tank in the sheet passing direction, a cleaning liquid in which a yellowing inhibitor is mixed by a second mixer is sprayed from a spray nozzle of a sub nozzle unit. Using the rinse equipment for the pickled steel sheet according to claim 4,
In the rinsing tank on the upstream side in the plate passing direction, a cleaning liquid with a higher concentration of yellowing inhibitor is sprayed from the main nozzle unit,
In the rinsing tank on the downstream side in the sheet passing direction, a cleaning method for rinsing a pickled steel sheet, wherein a cleaning liquid having a reduced yellowing inhibitor concentration is sprayed from the sub nozzle unit.

Images