JP2007031791A - Cleaning method for pickled steel strip in continuous pickling treatment line and cleaning apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cleaning method and apparatus for a pickled steel strip by which a satisfactory cleaning effect can be obtained even during low-speed running and line stop by using water not containing a discoloration preventing agent as cleaning water. <P>SOLUTION: A plurality of stages of rinsing tanks (8<SB>1</SB>, 8<SB>2</SB>, 8<SB>3</SB>, 8<SB>4</SB>) having spray nozzles (4<SB>1</SB>. 4<SB>2</SB>, 4<SB>3</SB>, 4<SB>4</SB>) are provided with cleaning water storage pits (10<SB>1</SB>, 10<SB>2</SB>, 10<SB>3</SB>, 10<SB>4</SB>) partitioned by weirs (9<SB>1</SB>, 9<SB>2</SB>, 9<SB>3</SB>), and circulating spray cleaning circuits (13<SB>1</SB>, 13<SB>2</SB>, 13<SB>3</SB>, 13<SB>4</SB>) are arranged. During steady operation, the cleaning water (circulation cleaning water) of the storage pits is sprayed by the circulating spray cleaning circuits to the steel strip. The contamination of the circulation cleaning water is diluted by replenishing the fresh cleaning water from a feedwater nozzle (12) of the rinsing tank of the final stage (received in the pit 10<SB>4</SB>of the final stage and flowing into the respective pits 10<SB>3</SB>, 10<SB>2</SB>, 10<SB>1</SB>as cascade flow overflowing the weirs 9<SB>1</SB>, 9<SB>2</SB>, 9<SB>3</SB>) and is held at required clarity. During the low-speed or line stop, the spray cleaning is performed by the fresh cleaning water in fresh spray cleaning circuits (15<SB>1</SB>, 15<SB>2</SB>, 15<SB>3</SB>, 15<SB>4</SB>) in place of the circulating spray cleaning. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  In the present invention, in order to prevent discoloration due to the residual acid solution on the surface of the steel strip, the pickling treatment is performed to remove the surface scale of the steel strip with an acid solution while continuously transporting the steel strip. The present invention relates to a method and apparatus for cleaning a pickled steel strip that removes residual acid solution from the steel strip with cleaning water on the outlet side.

  A continuous pickling treatment line that removes the surface scale (oxide) of the steel strip while continuously transporting the steel strip has a pickling device and a cleaning device installed on the outlet side thereof. The steel strip is removed by dissolving the surface scale by passing through the bath of acid solution (concentrated hydrochloric acid, etc.) in the pickling bath, and then passing through the cleaning device to remove the acid remaining on the steel strip surface. The liquid is washed away. There are two types of cleaning processes: spray cleaning in which cleaning liquid is sprayed from the spray nozzle to the steel strip surface, and immersion cleaning (immersion rinse) in which the cleaning liquid stored in the rinsing bath is immersed in a bath. The combined cleaning process is performed.

  FIG. 2 shows a configuration example of the cleaning apparatus. The cleaning device (II) installed on the outlet side of the pickling device (I) includes a spray cleaning unit in which spray nozzles (4) are arranged along a pass line (passing plate line) of the steel strip (S), and a rinse. An immersion rinse section having a bathtub (5). The steel strip (S) immersed and transferred in the acid bath (2) of the pickling tub (1) is washed after the acid solution on the surface of the steel strip is squeezed out by a ringer roll (squeezing roll) (3). Steel which has been subjected to spraying of cleaning liquid (spray cleaning) by spray nozzle (4) of spray cleaning section of apparatus (II) and immersion rinsing passing through cleaning liquid bath (6) of rinse bath (5) and cleaned Then, the surface cleaning liquid is removed by drying and sent to the next process.

The steel strip transfer operation in the continuous pickling / cleaning line involves welding of the steel strip (welding of the preceding steel strip and the subsequent steel strip) performed on the inlet side of the pickling device and the downstream of the cleaning device. Switching of operation modes such as low-speed transfer or transfer stop is performed regularly or irregularly by roll replacement in a process line (for example, a skin pass rolling line). Unlike the steady operation in which the steel strip is transferred at a predetermined line speed, it becomes difficult to sufficiently clean the surface of the pickled steel strip in an unsteady operation state such as low-speed transfer or transfer stop. Discoloration (yellowing) due to the remaining acid solution tends to occur.
As a countermeasure, a cleaning agent called a discoloration preventing agent, a discoloration removing agent or the like, for example, a chelating agent such as an organic carboxylate, is used, and the surface of the steel strip that passes through the ringer roll portion on the inlet side of the cleaning device In addition, a cleaning process (Patent Document 1, Patent Document 2) for applying a solution containing a cleaning drug, a spray cleaning method using a cleaning drug-containing solution (Patent Document 3), and the like have been proposed.
JP 2000-178775 A JP2003-231983 JP 2003-193275 A

The use of cleaning chemicals is effective in increasing the cleaning effect and suppressing or preventing discoloration of the steel strip surface. However, as the COD (chemical oxygen demand) of the cleaning waste liquid increases, the waste liquid treatment cost is greatly increased as a measure against environmental pollution. Will be forced to increase the burden. As another method, it is considered possible to suppress and prevent discoloration without using a cleaning agent by thoroughly using a large amount of clarified water such as industrial water and thoroughly performing spray cleaning. A large increase in the cost of the cleaning process due to the large amount of consumption is unavoidable.
Therefore, the present invention does not use a cleaning agent such as a discoloration prevention agent, and further suppresses the amount of industrial water used and the amount discharged as cleaning water, and at a low speed operation or shutdown of steel strip transfer. The present invention provides a pickling steel strip cleaning method and a cleaning device that ensure a sufficient cleaning effect even in an unsteady operation state such as the above, and can prevent discoloration of the steel strip surface.

The washing treatment method for the pickled steel strip in the continuous pickling treatment line of the present invention (Claim 1)
The pickling for preventing discoloration due to the acid solution remaining on the surface of the steel strip after the pickling treatment in which the surface scale of the steel strip is dissolved and removed by the acid solution in the pickling treatment section under the continuous transfer of the steel strip. In the cleaning apparatus installed on the outlet side of the processing unit, a method for cleaning a pickled steel strip that removes residual acid solution with water that does not contain cleaning chemicals,
A wash water storage pit that receives the wash water sprayed from the spray nozzle to the steel strip surface is provided at the bottom of each of the multiple-stage rinse tanks in which spray nozzles are arranged along the steel strip pass line. In the water storage pit, water that does not contain cleaning chemicals is stored as cleaning water, and the cleaning water in each cleaning water storage pit is maintained at a predetermined cleanliness by replenishing the cleaning water in a timely manner.
In the steady operation state in which the steel strip is transferred at a predetermined line speed, the circulating spray cleaning process in which the cleaning water in the cleaning water storage pit is pumped up and sprayed from the spray nozzle onto the surface of the steel strip for each rinsing tank In the unsteady operation state of low-speed transfer or stop of the steel strip, the circulating spray cleaning process is stopped, and unused fresh cleaning water not containing a cleaning chemical is supplied to the spray nozzle. It is characterized by a new water spray cleaning process that sprays on the surface of the belt.

  In the above spray cleaning process, switching from the circulating spray cleaning to the fresh water spray cleaning in the unsteady operation state is not necessarily performed in all of the rinsing tanks in the plurality of stages, and the fresh water spray cleaning is performed only in the rinse tank upstream of the line. The downstream rinse tank can be kept in the circulation spray cleaning (Claim 2). Also, in the unsteady operation state of steel strip transfer stop (line stop), if the line stop state lasts for a relatively long time, the new water spray cleaning is performed when the required cleaning process is performed after a certain period of time. The process can be stopped and returned to the circulating spray cleaning process (claim 3).

The pickling steel strip cleaning device according to the present invention (Claim 4)
The steel strip is washed with water that does not contain cleaning chemicals on the exit side of the pickling section after the pickling treatment where the surface scale of the steel strip is dissolved and removed with an acid solution in a pickling treatment device under continuous transfer of the steel strip. A pickling steel strip cleaning device that prevents discoloration of the steel strip by removing the acid solution on the surface,
i) Cleaning water spray nozzles 4 (4 ₁ , 4 ₂ , 4 ₃ ) along the steel strip pass line in the multiple-stage rinsing tanks 8 (8 ₁ , 8 ₂ , 8 ₃ ...) connected in the direction of steel strip transfer. ...)
ii) The ringer rolls 3 (3 ₂ , 3 ₃ , 3 ₄ ...) that are positioned between the adjacent rinsing tanks and that face each other across the steel strip pass line are arranged and the steel strips are transferred. Weirs 9 (9 ₁ , 9 ₂ ...) Orthogonal to the direction are provided at the tank bottoms, and the tank bottoms are used as washing water storage pits 10 (10 ₁ , 10 ₂ , 10 ₃ ...), And the weirs (9 ₁ , 9 ₂ ..., So that a cascade flow of wash water that sequentially overflows each weir (9 ₁ , 9 ₂ ...) From the wash water storage pit on the line end side to the wash water storage pit on the start end side is formed. The weir height that gradually decreases from the weir on the line end side to the weir on the start end side,

iii) Water that does not contain cleaning chemicals as cleaning water stored in the cleaning water storage pit 10 is supplied from the water supply nozzle 12 that opens to the rinsing tank on the end side of the steel strip pass line, and the cleaning water storage pit on the end side From the cascade flow, the wash water is stored in each of the wash water storage pits to the wash water storage pit on the start end side, and the wash water is replenished from the water supply pipe in a timely manner, so that the surplus water amount in the wash water storage pit 10 is By discharging from the cleaning water storage pit on the side, the cleaning water in the cleaning water storage pit is always kept at a predetermined cleanliness,
iv) Circulating spray cleaning circuit 13 (13 ₁ , 13) that pumps up the cleaning water in each cleaning water storage pit 10 and sprays it on the steel strip surface from the spray nozzles (4 ₁ , 4 ₂ , 4 ₃ ...) of each rinsing tank ₂ , 13 ₃ ... Are provided for each rinsing tank (8 ₁ , 8 ₂ , 8 ₃ ...), And unused new washing water that does not contain cleaning chemicals is added to the spray nozzles 4 (4 ₁ , 4,. 4 _2, 4 _{3 ...)} fresh water spray cleaning circuit 15 sprayed on the steel strip surface (15 _1, 15 _2, 15 ₃ ...) provided from,
During the steady operation in which the steel strip is transferred at a predetermined line speed, the cleaning process is performed by the circulating spray cleaning circuit 13, and when the steel strip is transferred at a low speed or when the transfer is stopped, the cleaning process is performed by the fresh water spray cleaning circuit 15. The cleaning processing circuit is configured to be switched.

  In the pickling apparatus, switching of the spray cleaning circuit in the unsteady operation state is divided into a rinse tank on the upstream side of the line and a rinse tank on the downstream side as desired, and in the upstream rinse tank, from the circulating spray cleaning to the fresh water spray. The rinsing tank on the downstream side is switched to cleaning, and the circulation spray cleaning process is continued as it is (Claim 5) and / or in the unsteady operation state of the steel strip transfer stop (line stop) for a certain period of time. A configuration (Claim 6) is adopted as appropriate in which the fresh water spray cleaning process is stopped and returned to the circulating spray cleaning process when the required cleaning process is performed.

In the present invention, the rinsing tank has a multi-stage configuration (8 ₁ , 8 ₂ , 8 ₃ ...) Connected in the steel strip transfer direction (line direction), and all cleaning modes in each stage rinsing tank are spray-cleaned. In addition, the spray cleaning is divided into two forms corresponding to the operation state of the line (a: steady operation state, b: unsteady operation state). In the steady operation in which the steel strip is transferred at a predetermined line speed, it is stored in the wash water storage pits (10 ₁ , 10 ₂ , 10 ₃ ...) Of the rinsing tanks (8 ₁ , 8 ₂ , 8 ₃ ...) Of each stage. The consumption of washing water is reduced by circulating the washing water used.
In addition, cleaning water in the cleaning water storage pit that is circulated during steady operation (contamination due to mixing of the acid solution with the increase in the amount of steel strip through circulation) will be replenished with new cleaning water as appropriate ( Dilution of contamination) keeps the contamination concentration below a predetermined value. As a result, the cleaning effect necessary for preventing discoloration of the steel strip surface during steady operation is stably maintained. On the other hand, in the unsteady operation in which the steel strip is transferred at a low speed or stopped (line stop), the above circulating spray cleaning using the cleaning water in the cleaning water storage pits (10 ₁ , 10 ₂ , 10 ₃ ...) Is circulated. Instead of switching to spray cleaning (new water spray cleaning) using unused cleaning water (new cleaning water), the spray cleaning effect in unsteady operation is ensured.

In this way, the wash water in the wash water storage pits (10 ₁ , 10 ₂ , 10 ₃ ...) Is circulated and used in the steady operation, and the newly supplied wash water is the wash water (circulation used in the wash water storage pit). The amount of water replenished to dilute the contamination of the water and the amount of water used for fresh water spray cleaning during non-steady operation is limited to the total The cleaning process corresponding to the change / switch between the steady operation and the unsteady operation is achieved. By suppressing the total consumption of cleaning water, it is possible to reduce the cleaning cost and to reduce the amount of waste water discharged from the cleaning device and the treatment cost.

Also, switching to fresh water spray cleaning when the above-mentioned unsteady operation (low speed transfer or line stop) is not always necessary in the downstream rinse tank (described later), so only the upstream rinse tank is treated with fresh water. By switching to spray cleaning (the rinsing tank on the downstream side continues circulation spray cleaning as it is), the consumption of new cleaning water can be further reduced. Furthermore, if the unsteady operation state of the transfer stop (line stop) continues for a relatively long time, if the cleaning process of the steel strip surface is achieved by the new water spray cleaning in the meantime, the water spray is changed from the new water spray cleaning to the circulating spray cleaning at that time. It can be restored and the consumption of new washing water can be further reduced.
In addition, the cleaning water used is water that does not contain cleaning chemicals (industrial water, etc.) in both steady operation and non-steady operation regardless of the line operation state. Compared with the cleaning process to be used, the waste cleaning water contamination (COD increase) and the environmental load are reduced accordingly, and the cost burden required for the waste liquid processing is reduced.

The present invention will be described below with reference to the drawings.
In FIG. 1, the cleaning device (II) installed on the outlet side of the pickling device (I) includes a plurality of rinse tanks (8) (8 ₁ , 8 ₂ , 8 ₃ , 8 ₄ ) connected in the steel strip transfer direction. ). In each rinsing tank, spray nozzles (4) (4 ₁ , 4 ₂ , 4 ₃ , 4 ₄ ) are arranged along the steel strip pass line, and weirs (9) (9 ₁ , 9 ₂ are arranged at the bottom of the tank. , 9 ₃ ). Each rinse tank (8 ₁ , 8 ₂ , 8 ₃ , 8 ₄ ) has a wash water storage pit (10) (10 ₁ , 10 ₂ , 10) separated by a weir (9 ₁ , 9 ₂ , 9 ₃ ). ₃ , 10 ₄ ), and between adjacent rinsing tanks, there is a ringer roll (3) (3 ₂ , 3 ₃ , 3 ₄ ) for removing (draining) the adhered liquid on the surface of the steel strip It is arranged. Further, as an auxiliary means for enhancing the spray cleaning effect, a brush roll (7) that is in rotational sliding contact with the surface of the steel strip is disposed at an appropriate place.
In the following description, each of the rinsing tanks (8 ₁ ) (8 ₂ ) (8 ₃ ) (8 ₄ ) is arranged in the first, second, third, Designate a 4-stage (or final-stage) rinse tank, and designate the wash water storage pits (10 ₁ ) (10 ₂ ) (10 ₃ ) (10 ₄ ) with the same stage number code. There is also.

Store in the wash water storage pits (10 ₁ , 10 ₂ , 10 ₃ , 10 ₄ ) of each stage from the inlet side (“line start side”) to the outlet side (“line end side”) of the cleaning device (II) The washing water (w) (w ₁ , w ₂ , w ₃ , w ₄ ) to be obtained is water (typically industrial water) that does not contain a cleaning agent. The cleaning water is supplied from the cleaning water supply source (11) through the water supply pipe (15 ₀ ) by the nozzle (12) opened to the fourth-stage rinse tank (8 ₄ ) on the line end side. / switching stop is performed by opening and closing control of the valve (16 _0). The replenishment of new washing water from the washing water supply nozzle (12) is appropriately performed during the line operation process (described later).
In addition, the weirs (9 ₁ , 9 ₂ , 9 ₃ ) that partition the bottom of the rinse tank (8) gradually decrease from the weir (9 ₃ ) on the line end side to the weir (9 ₁ ) on the start end side. Weir height is given. This is because the washing water supplied from the washing water supply nozzle (12) is moved from the washing water storage pit (10 ₄ ) on the end side toward the start end side (opposite to the direction of transport of the steel strip), This is because 9 ₃ , 9 ₂ , 9 ₁ ) are caused to flow into the wash water storage pits (10 ₃ , 10 ₂ , 10 ₁ ) as cascade flows that sequentially overflow (overflow).

Each stage of the rinse tank (8 ₁ , 8 ₂ , 8 ₃ , 8 ₄ ) is provided with a mutually independent circulation spray cleaning circuit (13) (13 ₁ , 13 ₂ , 13 ₃ , 13 ₄ ). The washing water (w ₁ , w ₂ , w ₃ , w ₄ ) of the washing water storage pit (10 ₁ , 10 ₂ , 10 ₃ , 10 ₄ ) is supplied to each circulation spray washing circuit (13 ₁ , 13 ₂ , 13 ₃ , 13 ₄ ) is sprayed from each spray nozzle (4 ₁ , 4 ₂ , 4 ₃ , 4 ₄ ) to the steel strip (S) passing therethrough. That is, spray cleaning of the steel strip passing through the rinsing tank is carried out by using the washing water (w ₁ , w ₂ , w ₃ , w ₄ ) for each stage of the rinsing tank (8 ₁ , 8 ₂ , 8 ₃ , 8 ₄ ). This is done by recirculating use. This cleaning water may be referred to as “circulating cleaning water” in the following description. This circulating spray cleaning is performed under a steady operation state in which the steel strip is transferred at a predetermined line speed.

The rinsing tank (8 ₁ , 8 ₂ , 8 ₃ , 8 ₄ ) has a fresh water spray cleaning circuit (15) (15 ₁ , 15 ₂ ) together with the circulating spray cleaning circuit (13 ₁ , 13 ₂ , 13 ₃ , 13 ₄ ). , 15 ₃ , 15 ₄ ). This is because unused cleaning water (new cleaning water) different from circulating cleaning water is supplied from the cleaning water supply source (11), and the steel strip is sprayed by the spray nozzle (4 ₁ , 4 ₂ , 4 ₃ , 4 ₄ ). It sprays on the surface. The new cleaning water supplied from the cleaning water supply source (11) is water (industrial water or the like) that does not contain a cleaning chemical as described above. This spray cleaning using the new cleaning water is referred to as “new water spray cleaning” in the following description, in distinction from the circulation spray cleaning. The fresh water spray cleaning is performed in an unsteady operation state.

The switching operation between the circulating spray cleaning and the fresh water spray cleaning is performed by opening / closing the valves (14 ₁ , 14 ₂ , 14 ₃ , 14 ₄ ) of the circulating spray cleaning circuit (13) and the pumps (p ₁ , p ₂ , p ₃ , p ₄ ) and ON / OFF operation of the fresh water supply spray cleaning circuit (16 ₁ , 16 ₂ , 16 ₃ , 16 ₄ ). For this switching operation, if desired, only the upstream rinse tank (for example, rinse tanks 8 ₁ , 8 ₂ ) is switched from circulating spray cleaning to fresh water spray cleaning, and downstream rinse tanks (rinse tanks 8 ₃ , 8). ₄ ) may be configured to continue the circulating spray cleaning as it is.
In addition, with regard to fresh water spray cleaning when the transfer is stopped (line stop), an upper limit is set for the duration of the new water spray cleaning, and when a certain period of time elapses due to the timer setting, the original circulating spray cleaning from the new water spray cleaning is performed. It is also possible to adopt a configuration for returning to (see below).

The new water spray supply circuit (15) is provided with new washing water supply branches (15 ₁₁ , 15 ₂₁ , 15 ₃₁ , 15 ₄₁ ) indicated by chain lines as desired, and ringer rolls (3 ₁ , 3 ₂ , A configuration in which the spray nozzle closest to the outlet side of 3 ₃ , 3 ₄ ) is separated from the circulation spray cleaning circuit is adopted. In this case, new cleaning water supply branch pipes (15 _11, 15 _21, 15 _31, 15 ₄₁₎ spray nozzle connected to each of _{(4 11, 4 21, 4 31, 4 41)} (Ringer roll exit side of the last Since the new washing water is sprayed from the nozzles at all times (steady and unsteady operation), the surface of each ringer roll (3 ₁ , 3 ₂ , 3 ₃ , 3 ₄ ) is kept in a cleaner state. This is effective for keeping the cleaning effect of the pickled steel strip highly stable.

Next, the steel strip spray cleaning operation by the cleaning apparatus will be described.
The steel strip (S) led out from the pickling tank (1) on the exit side of the pickling device (I) is squeezed on the surface with the ringer roll (3 ₁ ) on the inlet side of the cleaning device (II). It is taken and introduced into the rinsing tank (8), and the circulation spray cleaning process is sequentially performed in each rinsing tank from the first rinsing tank (8 ₁ ) on the start end side to the fourth rinsing tank (8 ₄ ) on the end side. receive. When the steel strip (S) passes through the boundary between adjacent rinsing tanks, the washing water adhering to the surface is squeezed out by the ringer roll (3 ₂ , 3 ₃ , 3 ₄ ) installed there. The wash water storage pits (10 ₁ , 10 ₂ , 10 ₃ , 10 ₄ ) of each stage are separated from each other by weirs (9 ₁ , 9 ₂ , 9 ₃ ). For this reason, the amount of cleaning water (circulated cleaning water) in the upstream rinsing tank brought into the downstream rinsing tank (the amount of movement of the circulating cleaning water accompanying the transfer of the steel strip) is very small. Since the acid solution residue on the surface of the steel strip gradually decreases as it passes through the rinsing tanks of each stage, the circulating cleaning in each of the cleaning water storage pits (10 ₁ , 10 ₂ , 10 ₃ , 10 ₄ ) The contamination concentration of water shows a concentration gradient that gradually decreases from the upstream side toward the downstream side.

Contamination concentration of circulating wash water stored in the wash water storage pits (10 ₁ , 10 ₂ , 10 ₃ , 10 ₄ ) at each stage is due to the progress of the steel strip cleaning operation (increase in the amount of steel strip passage over time) Ascending gradually. To ensure the required cleaning effect (acid solution removal effect that can prevent discoloration of the steel strip surface) stably, each stage of the circulating cleaning water must be maintained at a constant cleanliness (acid The contamination concentration by the liquid must not exceed the allowable upper limit). For this purpose, the contamination concentration is diluted by supplying new cleaning water from the cleaning water supply nozzle (12). When new cleaning water is replenished from the cleaning water supply nozzle (12), the bottom of the tank moves from the cleaning water storage pit (10 ₄ ) of the final stage rinsing tank toward the cleaning water storage pit (10 ₁ ) of the rinsing tank on the start side. A cascade flow of washing water is formed which sequentially overflows (overflows) the weirs (9 ₃ ), (9 ₂ ) and (9 ₁ ). The increased amount of the circulating cleaning water accompanying the replenishment of the new cleaning water (the amount of water exceeding the amount stored in the cleaning water storage pit 10) is the drainage port (17) provided in the cleaning water storage pit (10 ₁ ) on the start side. Discharged as waste liquid. The waste liquid is sent to a waste liquid processing apparatus (not shown) and subjected to a predetermined process.

Therefore, the contamination status of the circulating cleaning water in each cleaning water storage pit (10 ₁ , 10 ₂ , 10 ₃ , 10 ₄ ) is detected in a timely manner, and a new one is supplied from the cleaning water supply nozzle (12) according to the progress of the contamination. By appropriately supplying cleaning water, the circulating cleaning water in the cleaning water storage pit (10 ₁ , 10 ₂ , 10 ₃ , 10 ₄ ) is always maintained at the required cleanliness (within the allowable contamination concentration range). , Ensure the cleaning effect in steady operation. The cleanliness (contamination concentration) of each wash water storage pit (10 ₁ , 10 ₂ , 10 ₃ , 10 ₄ ) is managed by, for example, pH measurement. As specific examples, the pH of the first stage pit (10 ₁ ): 1.8 or more, the pH of the second stage pit (10 ₂ ): 3.0 or more, the pH of the third stage pit (10 ₃ ): 5.0 or more, the fourth stage pit The pH of (10 ₄ ) is adjusted to 6.3 or more. If an abnormality is detected that causes the pH measurement value to deviate from the control limit value, check or circulate the ringer roll (3) malfunction (defective liquid removal from the surface of the steel strip) as a measure to eliminate the abnormal condition. Measures such as cleaning water renewal will be implemented as appropriate.
The steel strip (S), which has passed through the rinsing tanks (8 ₁ , 8 ₂ , 8 ₃ , 8 ₄ ) and washed away the acid solution on the surface, is installed at the end of the final stage rinsing tank (8 ₄ ). The attached cleaning liquid on the surface is squeezed out by the ringer roll (3 ₅ ) and sent out from the cleaning device.

On the other hand, unlike the steady operation, the cleaning process in the non-steady operation in which the steel strip is transferred at a low speed or stopped (line stop) is switched from the circulating spray cleaning to the fresh water spray cleaning. The new water spray cleaning is performed by a new water spray source (11) from a new cleaning water supply source (11) through a new water spray cleaning circuit (15 ₁ , 15 ₂ , 15 ₃ , 15 ₄ ) arranged for each rinsing tank. This is a cleaning process in which water is sprayed onto the surface of the steel strip with a spray nozzle (4 ₁ , 4 ₂ , 4 ₃ , 4 ₄ ). New cleaning water supplied from the new cleaning water supply source (11) is unused clear water (industrial water, etc.), and has a higher cleaning action than circulating cleaning water used in circulating spray cleaning, Provides the cleaning effect necessary to prevent discoloration of the steel strip for unsteady operation. The new cleaning water used for the new water spray cleaning is accepted in the cleaning water storage pit (10 ₁ , 10 ₂ , 10 ₃ , 10 ₄ ) and contributes to the dilution (reduction of contamination concentration) of the circulating cleaning water. Excess amount exceeding the storage capacity of the storage pit (10) is discharged from the drain port (17) of the washing water storage pit (10 ₁ ) on the start end side.

  Unsteady operation (low-speed transfer or line stop) can be performed by steel strip welding on the entry side (not shown) of the pickling device (I), or on the downstream side (not shown) of the washing device (II) (for example, It occurs regularly or irregularly due to various reasons such as roll change in the steel band skin pass line). The duration of the unsteady operation state and the specific transfer speed in the low-speed operation differ depending on the respective occurrence reasons. Switching between circulating spray cleaning (steady operation) and fresh water spray cleaning (unsteady operation) is performed based on the line speed. The line speed varies depending on the specific configuration and specifications of the cleaning device, the steel strip material type, etc., but generally 30m / min is used as a reference, and the higher spraying speed is regarded as a steady operation, and circulating spray cleaning is applied. When the speed is reduced to a lower transfer speed, it is possible to perform the cleaning process efficiently by switching to the new water spray cleaning as a low speed operation.

Each stage rinsing tank spray nozzle _{(8 1, 8 2, 8 3, 8 4) (4 1, 4 2, 4 3, 4 4)} is Shinmizu spray cleaning (unsteady and circulating spray cleaning (steady operation) However, since the cleaning water for new water spray cleaning (new cleaning water) has a higher cleaning action than the circulating cleaning water, the spray flow rate of The amount can be reduced compared to the attached flow rate. For example, in a line where the spraying flow rate for circulating spray cleaning is set to about 60 m ³ / min, it is possible to obtain the desired cleaning effect by setting the flow rate to about 10 m ³ / min or less for fresh water spray cleaning. it can. The flow rate of cleaning water sprayed onto the steel sheet is adjusted by attaching a valve (not shown) to each spray nozzle, and selectively using the spray nozzle by opening / closing control (spraying of the spray nozzle) or adjusting the injection pressure. It can be performed arbitrarily.

The fresh water spray cleaning in the non-steady operation is not necessarily performed for the rinsing tanks in all stages (8 ₁ , 8 ₂ , 8 ₃ , 8 ₄ ), and the upstream rinsing tank (for example, the rinsing tank 8 ₁ , Only the 8 ₂ ) can be switched to the fresh water spray cleaning, and the downstream rinsing tank (rinsing tanks 8 ₃ and 8 ₄ ) can continue the circulating spray cleaning during the steady operation as it is. The steel strip on the downstream side has already undergone circulation spray cleaning when passing through the upstream rinsing tank (in this case, the rinsing tanks 8 ₁ , 8 ₂ ), and the acid solution residue on the steel strip surface is reduced accordingly. Because. The distinction between the upstream side and the downstream side here is relative. For example, in a configuration in which the rinsing tank (8) is connected in five stages, the first and second stages are upstream, and the third to fifth stages are downstream. Alternatively, the spray cleaning may be switched with the first or third stage being the upstream side and the fourth and fifth stages being the downstream side. If it is not necessary to switch to the fresh water spray cleaning in the downstream rinsing tank (for example, the rinsing tanks 8 ₃ and 8 ₄ ) as described above, the new water spray cleaning circuit (in this example, the new water spray is used). Installation of the cleaning circuits 15 ₃ and 15 ₄ ) may be omitted.

Moreover, when the unsteady operation state of the line stop is for a relatively long time, it is not necessary to continue the fresh water spray cleaning over the entire time of the line stop. This is because if the cleaning effect necessary for preventing discoloration is achieved by performing the new water spray cleaning, it is not necessary to continue the new water spray cleaning. Therefore, at the time of starting the fresh water spray cleaning, the cleaning time may be set as a timer, and when the predetermined time has elapsed, it may be returned to the circulating spray cleaning. For example, when a line stop state continues after several minutes (for example, 6 minutes) have passed since the start of new water spray cleaning, it is possible to return from the new water spray cleaning to the original circulating spray cleaning, Thereby, consumption of new washing water can be further reduced.
In addition, when the dummy coil steel strip is passed through instead of the product steel strip as in periodic repairs of the line, spray cleaning during that time is unnecessary, so the product steel strip passing operation is resumed. During this period, both the circulating spray cleaning and the fresh water spray cleaning are suspended.

  In the continuous pickling line equipped with the cleaning device of FIG. 1, the steel strip derived from the acid bath (1) of the pickling device (I) (acid bath: about 10 vol% HCl solution) is cleaned with the cleaning device (II). Introduce into the rinsing tank (4 stages, total length 24 m) and perform spray cleaning treatment. The cleaning water supplied from the cleaning water supply source (11) for circulating spray cleaning (steady operation) and fresh water spray cleaning (unsteady operation) is clear industrial water that does not contain cleaning chemicals.

[Spray cleaning operation]
To manage the clarification (contamination concentration) of circulating wash water stored in the wash water storage pits (10 ₁ , 10 ₂ , 10 ₃ , 10 ₄ ) of each stage rinse tank Is arranged to detect the pH value of each of the circulating cleaning water and to appropriately replenish the new cleaning water from the new cleaning water supply nozzle (12) in response to the change in the detected pH value. Spray cleaning treatment was performed while maintaining the pH value of the circulating cleaning water in the tank within the following range.

(Table 1)
-Control of contamination concentration of circulating cleaning water in cleaning water storage pit-
1st pit (10 ₁ ) 2nd pit (10 ₁ ) 3rd pit (10 ₁ ) 4th pit (10 ₁ )
pH 1.8 or more 3.0 or more 5.0 or more 6.3 or more

Steel strip transfer in this continuous pickling line is switched to deceleration operation when the roll of the downstream skin pass line is replaced. Spray cleaning was carried out with steel strip transfer at a line speed of 30 m / min or more as steady operation (circulating spray cleaning), and transfer operation at a lower speed as unsteady operation. Switching between circulating spray cleaning (a) and fresh water spray cleaning (b) is performed by opening / closing the valve of the circulating spray cleaning circuit (13 ₁ , 13 ₂ , 13 ₃ , 13 ₄ ) and starting / stopping the pump. It was performed by opening / closing the valves of the new water spray cleaning circuit (15 ₁ , 15 ₂ , 15 ₃ , 15 ₄ ) corresponding to.
The spray cleaning operation conditions are shown in Tables 2 and 3 (Table 2: Circulating spray cleaning, Table 3: Fresh water spray cleaning).

(Table 2)

[a: Circulating spray cleaning in steady operation (line speed ≧ 30m / min)]
Number of headers Number of nozzles Spray pressure (MPa) ^* Spray fluid volume (m ³ / min)
First rinsing tank 12 90 0.15 60
Second rinse tank 12 90 0.15 60
Third rinsing tank 8 60 0.15 60
4th rinse tank 8 60 0.15 60
* Spray pressure shows maximum value

(Table 3)
[b: New water spray cleaning in non-steady operation (line speed <30m / min)]
Number of headers Number of nozzles Spray pressure (MPa) ^* Spray fluid volume (m ³ / min)
First rinse tank 12 16 0.15 6
Second rinse tank 12 14 0.10 6
Third rinse tank 8 16 0.10 6
4th rinse tank 8 14 0.10 6
* Spray pressure shows maximum value

By switching the spray cleaning operation mode (circulating spray cleaning and fresh water spray cleaning) in response to fluctuations in line operation under conditions where unsteady operation is repeated regularly or irregularly, It was confirmed that a good cleaning effect can be ensured through the line operation of the steady operation, and the anti-discoloration effect of the steel strip can be improved in each stage as compared with the conventional cleaning treatment.
Also, in case of steel strip transfer stop (line stop), the upper limit time of fresh water spray cleaning is set to 6 minutes, and when it exceeds that time, the operation mode is switched from fresh water spray cleaning to circulating spray cleaning. It was confirmed that the same good cleaning effect as described above was obtained even when the above was performed. Incidentally, the new new washing water consumption increase in accordance with the practice of the water spray washing, a 5 m ³ or less (fresh water spray cleaning per), the increase in the cost burden, improve the cleaning effect (cleaning poor This can be fully compensated for by a significant reduction in the resulting loss).

  According to the present invention, regardless of fluctuations in steady operation and non-steady operation, the remaining acid solution of the pickled steel strip is effectively washed away by spray cleaning using cleaning water that does not contain cleaning chemicals. An improved steel strip surface quality that does not cause discoloration can be obtained. The spray cleaning is divided into cyclic spray cleaning and fresh water spray cleaning corresponding to steady operation and non-steady operation, and the operation mode is switched. The cleaning effect can be obtained, and the cost burden of new cleaning water is small. Since the waste liquid discharged from the cleaning equipment does not contain cleaning chemicals, the environmental impact is small, the cost burden required for waste liquid treatment is reduced, and it has industrially very useful value as a cleaning treatment method for pickling steel strips. Is.

It is a figure which shows the Example of the washing | cleaning apparatus which implements the washing process of the pickled steel strip of this invention. It is a figure which shows the conventional general washing | cleaning apparatus.

Explanation of symbols

1: Acid bath 2: Acid bath
3 (3 ₁ , 3 ₂ , 3 ₃ , 3 ₄ , 3 ₅ ): Ringer roll 4 (4 ₁ , 4 ₂ , 4 ₃ , 4 ₄ ): Spray nozzle 5: Rinse tub 6: Rinse liquid bath 7: Brush roll 8 (8 ₁ , 8 ₂ , 8 ₃ , 8 ₄ ): Rinse tank 9 (9 ₁ , 9 ₂ , 9 ₃ ): Weir

10 (10 ₁ , 10 ₂ 10 ₃ , 10 ₄ ): Wash water storage pit 11: New wash water supply source 12: New wash water supply nozzle 13 (13 ₁ , 13 ₂ , 13 ₃ , 13 ₄ ): Circulating spray washing Circuit 14 (14 ₁ , 14 ₂ , 14 ₃ , 14 ₄ ): Open / close valve 15 (15 ₁ , 15 ₂ , 15 ₃ , 15 ₄ ): New water spray cleaning circuit
15 ₁₁ , 15 ₂₁ , 15 ₃₁ , 15 ₄₁ : New water supply branch 16 (16 ₁ , 16 ₂ , 16 ₃ , 16 ₄ ): Valve 17: Drain port p ₁ , p ₂ , p ₃ , p ₄ : Pump I : Pickling equipment
II: Cleaning device S: Steel strip

Claims (6)

The pickling for preventing discoloration due to the acid solution remaining on the surface of the steel strip after the pickling treatment in which the surface scale of the steel strip is dissolved and removed by the acid solution in the pickling treatment section under the continuous transfer of the steel strip. In the cleaning apparatus installed on the outlet side of the processing unit, a method for cleaning a pickled steel strip that removes residual acid solution with water that does not contain cleaning chemicals,
A wash water storage pit that receives the wash water sprayed from the spray nozzle to the steel strip surface is provided at the bottom of each of the multiple-stage rinse tanks in which spray nozzles are arranged along the steel strip pass line. In the water storage pit, water that does not contain cleaning chemicals is stored as cleaning water, and the cleaning water in each cleaning water storage pit is maintained at a predetermined cleanliness by replenishing the cleaning water in a timely manner.
In the steady operation state in which the steel strip is transferred at a predetermined line speed, the circulating spray cleaning process in which the cleaning water in the cleaning water storage pit is pumped up and sprayed from the spray nozzle onto the surface of the steel strip for each rinsing tank In the unsteady operation state of low-speed transfer or stop of the steel strip, the circulating spray cleaning process is stopped, and unused fresh cleaning water not containing a cleaning chemical is supplied to the spray nozzle. A method for cleaning a pickled steel strip in a continuous pickling treatment line, characterized by performing a fresh water spray cleaning treatment to spray the surface of the strip.   2. The fresh water spray cleaning process in an unsteady operation state is performed in a rinse tank on the upstream side of the steel strip pass line, and the downstream rinse tank continues the circulating spray cleaning process as it is. Washing method for pickled steel strip in continuous pickling line.   In the unsteady operation state in which the transfer of the steel strip is stopped, when the residual acid solution on the steel strip surface is removed by the new water spray cleaning process, the supply of new cleaning water is stopped and switched to the circulating spray cleaning process. The cleaning method of the pickling steel strip in the continuous pickling processing line of Claim 1 or Claim 2 characterized by the above-mentioned. The steel strip is washed with water that does not contain cleaning chemicals on the exit side of the pickling section after the pickling treatment where the surface scale of the steel strip is dissolved and removed with an acid solution in a pickling treatment device under continuous transfer of the steel strip. A pickling steel strip cleaning device that prevents discoloration of the steel strip by removing the acid solution on the surface,
i) Cleaning water spray nozzles 4 (4 ₁ , 4 ₂ , 4 ₃ ) along the steel strip pass line in the multiple-stage rinsing tanks 8 (8 ₁ , 8 ₂ , 8 ₃ ...) connected in the direction of steel strip transfer. ...)
ii) A ringer roll 3 (3 ₁ , 3 ₂ , 3 ₃ ...) that is positioned between the adjacent rinsing tanks and is opposed to the upper and lower sides across the steel strip pass line is disposed and the steel strip is transferred. Weirs 9 (9 ₁ , 9 ₂ ...) Orthogonal to the direction are provided at the tank bottoms, and the tank bottoms are used as washing water storage pits 10 (10 ₁ , 10 ₂ , 10 ₃ ...), And the weirs (9 ₁ , 9 ₂ ..., So that a cascade flow of wash water that sequentially overflows each weir (9 ₁ , 9 ₂ ...) From the wash water storage pit on the line end side to the wash water storage pit on the start end side is formed. The weir height that gradually decreases from the weir on the line end side to the weir on the start end side,
iii) Water that does not contain cleaning chemicals as cleaning water stored in the cleaning water storage pit 10 is supplied from the water supply nozzle 12 that opens to the rinsing tank on the end side of the steel strip pass line, and the cleaning water storage pit on the end side From the above-mentioned cascade flow, the wash water is stored in each of the wash water storage pits that reach the wash water storage pit on the start end side, and the wash water is replenished from the water supply pipe in a timely manner, so that the surplus water amount in the wash water storage pit 10 is By discharging from the cleaning water storage pit on the side, the cleaning water in the cleaning water storage pit is always kept at a predetermined cleanliness,
iv) Circulating spray cleaning circuit 13 (13 ₁ , 13) that pumps up the cleaning water in each cleaning water storage pit 10 and sprays it on the steel strip surface from the spray nozzles (4 ₁ , 4 ₂ , 4 ₃ ...) of each rinsing tank ₂ , 13 ₃ ... Are provided for each rinsing tank (8 ₁ , 8 ₂ , 8 ₃ ...), And unused new washing water that does not contain cleaning chemicals is added to the spray nozzles 4 (4 ₁ , 4,. 4 _2, 4 _{3 ...)} fresh water spray cleaning circuit 15 sprayed on the steel strip surface (15 _1, 15 _2, 15 ₃ ...) provided from,
During the steady operation in which the steel strip is transferred at a predetermined line speed, the cleaning process is performed by the circulating spray cleaning circuit 13, and when the steel strip is transferred at a low speed or when the transfer is stopped, the cleaning process is performed by the fresh water spray cleaning circuit 15. An apparatus for cleaning a pickled steel strip in a continuous pickling line in which the cleaning circuit is switched.   In the unsteady operation state, only the rinse tank on the upstream side of the line is switched from the circulating spray cleaning process to the fresh water spray cleaning process, and the downstream rinse tank is configured to continue the circulating spray cleaning process. An apparatus for cleaning a pickled steel strip in a continuous pickling treatment line according to claim 4.   In the unsteady operation state in which the transfer of the steel strip is stopped, when the residual acid solution on the surface of the steel strip is removed by the new water spray cleaning process, the fresh water spray cleaning process is switched to the circulating spray cleaning process. The washing apparatus of the pickling steel strip in the continuous pickling processing line of Claim 4 or Claim 5 comprised by these.

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