JPS6024182B2 - Automatic control device for metal surface treatment liquid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control device that can automatically control various treatment liquids for treating metal surfaces.

Surface treatment line equipment that cleans the surface of metal products and continuously forms a chemical conversion film, plating, etc. on the surface is generally a means of transporting the metal products, and a surface treatment method such as spraying or dipping. It consists of a device for detecting, measuring, and controlling the components, concentration, and temperature of the treatment liquid necessary for surface treatment, a so-called automatic control device. The present invention relates to a device that automatically detects, measures, and controls the components and concentrations of a metal surface treatment liquid (hereinafter referred to as treatment liquid), a so-called automatic treatment liquid control device, and is used to automatically control the treatment liquid in a surface treatment line. In the method of means for replenishing the chemical in an amount corresponding to the number of metal products to be treated or the area to be treated, and means for measuring the concentration of the treatment liquid using a means for measuring the concentration of the treatment liquid and adjusting the amount of replenishment by the above means. The present invention relates to an automatic control device for processing liquid.

In the present invention, metal products include various cans, automobile bodies, refrigerator bodies, and other metal products of all shapes.
Includes metal strips, metal gong plates, etc. Generally, when surface-treating metal products, the texture of the cleaned surface and the characteristics of the film are determined by the components, concentration, temperature, and treatment time of the treatment solution.To obtain the desired properties and characteristics, the components and concentration of the treatment solution are determined. It must be controlled within a narrow range of optimal values.
As the treatment liquid is processed, chemical components in the solution react with metals, and unnecessary components and interfering ions are mixed in and accumulated during the treatment process. In addition, the processing liquid is physically extracted by metal products,
Or it becomes a mist and scatters. Therefore, the processing liquid is consumed and its components and concentration decrease. Therefore, it is necessary to continuously or periodically replenish the components and concentration of the processing solution using chemicals to maintain the chemical components of the processing solution at the required concentration. This control means may be performed manually, but conventionally automatic control devices have been used, and these devices control the pH of the processing liquid,
Conductivity, redox potential, and metal ions, F', CN'
If the measured concentration of the processing liquid is lower than a predetermined value using a concentration measuring device for a specific component such as, a pump linked to the concentration measuring device is activated and replenishes the chemical to the processing liquid to reach the predetermined measured value. It can be controlled continuously.

Examples of inventions related to these automatic control methods and devices include Tokuko Publication No. 44-7606, No. 44-16203 No. 45-27 Lock Paper, No. 51-37621 No. 51-37621, and Samurai No. 54-35517. can.

Conventionally known automatic control devices all measure the concentration of the components of the treatment liquid by measuring methods such as pH, conductivity, ion electrode, redox electrode, etc., either alone or in combination, and when the concentration of the treatment liquid is at the lower limit of the set concentration range. A method of replenishing the drug until the value reaches the upper limit of the set concentration range when the value drops below the set concentration range;
In other words, a feedback method was used to control the concentration of the processing solution. However, according to the experience and various experiments of the present inventors, there was a drawback that the concentration of the actually controlled treatment liquid fluctuated more than the set concentration range for the following reasons.

That is, in an actual surface treatment line, a chemical added to the treatment liquid at a certain point is uniformly dissolved in the treatment liquid after it is added, and a part of the liquid is transferred to an automatic control device and then 3 to 3 minutes before measurement starts with the concentration measuring device inside the device.
It usually takes 13 minutes, and there is a dead time of 3 to 15 minutes in so-called automatic control. A dead time of 3 to 13 minutes is not a problem if the concentration of the processing solution changes slowly, but if the processing area of metal products per unit time is large compared to the processing tank capacity, that is, the processing load rate is high. In this case, since the concentration of the treatment liquid changes drastically, it is difficult to maintain the concentration accurately and constant due to the dead time of 3 to 18 minutes. It is known from automatic control theory that generally speaking, the larger the dead time, the larger the control error, and therefore the more difficult it is to achieve proper control. If the concentration of the processing liquid fluctuates beyond the set concentration range due to the decrease in accuracy as described above, the chemical will be replenished unnecessarily, and the fluctuations in the concentration of the processing liquid will increase accordingly, resulting in surface treatment with a continuously stable quality. It is difficult to obtain a film.

In order to eliminate these drawbacks, the present inventors conducted various studies, and as a result, improved the control method of the sub-chamber only by measuring the concentration of the processing liquid, and completed the present invention. The control method according to the present invention will be described below.

First, the number of metal products or the component concentration consumed per unit surface area is measured and calculated in advance.

From this, the computer in the control device calculates the consumption amount of the medicine according to the number or surface area of the metal products actually treated, and replenishes the medicine. While replenishing in this manner, the concentration of the processing liquid is measured with a concentration measuring device to confirm that the concentration is maintained within the set range. If it cannot be maintained within the set range, the computer automatically checks the component concentration of the processing liquid consumed per object to be processed or per unit surface area, and corrects the consumption amount to adjust the amount of chemical replenishment. to maintain the concentration within the set range. The correction method will be described later. When controlled in this way, the amount of chemicals corresponding to the treated area is replenished at the same time as the treatment, so even if the values of a and b are slightly different from the appropriate values, the concentration is kept almost constant. Concentration changes will be very slow.

(Refer to Examples for this situation) If the concentration change is slow, 3
The effect of the ~15 minute dead time is almost eliminated, and the set concentration can be controlled within a very narrow range. The surface treatment line does not always operate in a steady state, and sometimes the operating rate is 1/5 or 1/10 of full operation, and the line sometimes stops, so the conventional method In this case, the concentration of the processing liquid to be controlled fluctuates due to the above-mentioned differences in operating conditions, and sometimes deviates significantly from the set value.

If the concentration of the treatment solution fluctuates greatly, the quality of the formed film will fluctuate and deteriorate, resulting in unnecessary consumption of chemicals. By applying the device of the present invention, the concentration of the treatment liquid can be maintained within an extremely narrow range compared to automatic control using conventional feedback methods, and this allows the quality of the coating that is continuously processed in the surface treatment line to be constant. Since high quality can be maintained, wasteful replenishment is eliminated, and the amount of medicine consumed can be reduced, economically favorable results can be obtained.

In conventional automatic control of chemical solutions using the feedback method, concentration measuring instruments such as pH, conductivity, and ion electrodes are often contaminated and deteriorated by the processing solution, and their designated sensing functions are diminished, resulting in significant differences from the actual processing solution concentration. In some cases, this value may be indicated.

In such cases, since control is performed only based on the value of the concentration measuring device, the concentration is often controlled to a value that is quite different from the set concentration, resulting in line troubles. The automatic control device according to the present invention is capable of detecting a decline in the sensing function due to contamination, deterioration, etc. of the concentration measuring device as described above. This makes it possible to prevent line troubles by issuing an alarm when such an abnormality is detected in the concentration measuring device and prompting the concentration measuring device to be replaced. A method for detecting such an abnormality in the concentration measuring device will be explained at the end of the embodiment. Next, an automatic control device according to the present invention will be explained based on an illustrated embodiment.

As an example, bath management of chromate treatment liquid in chromate treatment of beverage cans is given. First, a case will be described in which a treatment liquid having the following components is prepared, and the following chromate treatment is performed on an aluminum can using this treatment liquid, and the concentration is controlled.

Processing liquid component concentration C 1. Ship/side P043- 9. Hammer/So Free F- 0.17g/So (17 Wind) Aluminum Can Aluminum DI Can (Drawing & Ironing) Dimensions
67 cases x 169 capes In Fig. 1, the chromate treatment liquid is filled in the treatment tank 1, and is sent to the spray nozzle 3 placed at the top of the treatment tank 1 via the spray pump 2 connected to the treatment tank 1, where it becomes a mist. be done.

Aluminum cans 4, which have been thoroughly cleaned through the degreasing and water washing process, are continuously conveyed into the treatment liquid that has been dropped into the treatment liquid and come into contact with the chromate treatment liquid. As a result, a chromate film is formed on the surface of the aluminum can 4, and at this time, some of the components of the treatment liquid are consumed. The atomized treatment liquid is then collected and returned to the treatment tank 1, but a portion of it adheres to the aluminum street 4 and its conveyance equipment and is extracted and consumed in the next water washing process. When the aluminum cans 4 are processed, the number of cans is counted by a can counter 5 and the value is sent to an arithmetic controller 7.

A part of the processing liquid is sent to a concentration measuring device 6 via a spray pump 2.
The concentration of the treatment liquid is measured. As a concentration measuring device, for example, fluorine ion electrode F-1 manufactured by Toa Denpa Kogyo ■
Free fluorine ions were measured using No. 25 and a fluorine amplifier, and electrical conductivity was measured using a conductivity cell and a conductivity amplifier manufactured by the same company. The measured free fluorine value and electrical conductivity value are sent to the arithmetic controller 7. The arithmetic controller 7 is a so-called microcomputer using, for example, a NEC Corporation PD780 microprocessor, and performs the arithmetic control described later. Arithmetic controller 7 connects replenishment pumps 8 and 9
By turning ON and OFF the main replenishment agent 10 and the sub-replenishment agent 11 are supplied to the processing tank 1, thereby controlling the concentration. The components of each agent are shown below. King Replenishment Agent C Guju 60g/Ku P〇43- 410g/Zo Liu Replenishment Agent F-20 Female nokkimic acid ions and phosphate ions are the main components that form the film, but
The electrical conductivity of the treatment liquid is mostly controlled by these factors.

In other words, the chromic acid and phosphate ion concentrations can be kept constant by controlling the electrical conductivity. Furthermore, since free fluorine ions promote the film formation reaction, it is most important to keep the free fluorine ions constant in order to produce a chromate film of constant quality, and this concentration is measured using a fluorine ion electrode. Therefore, by measuring the electrical conductivity, the amount of the main replenisher is controlled, and by measuring the free fluorine ions, the amount of the sub-replenisher is controlled. In the conventional control method, these concentrations are measured, and if they are lower than the set range, the replenishment pump is operated to replenish the concentration to keep the concentration constant, but in the present invention, the arithmetic controller 7 performs the following: The control means according to the present invention that performs the control shown in FIG.

First, the computer calculates the amount of replenishment according to the following formula and performs replenishment.

Formula-1 Replenishment amount of free fluorine = number of cans processed × unit consumption amount
+ Mechanical loss r m a b (g/min)
(can/min) (/can) (Here, the unit consumption amount a is the estimated consumption amount of free fluorine per aluminum can.

The mechanical loss b is the amount of free fluorine lost due to mechanical loss of the processing liquid and is not due to the surface treatment of the can, such as decomposition of components in the processing liquid due to empty spraying and metal surface treatment equipment. Indicates losses due to special removal, leakage, etc. In this way, the amount of free fluorine to be supplied is calculated and free fluorine is replenished. However, if the values of a and b are not appropriate, the free fluorine concentration (hereinafter referred to as concentration) will continuously increase or decrease. In this case, the control device automatically measures the concentration, and uses this value to verify and correct the values of a and b.

Note that all of the calculation control methods described below are realized by being programmed into a computer. The verification correction method for a and b is to take a certain period of time T, (minutes), set the initial concentration as C, (g/〆), and set the final concentration as C2 (g/s).
shall be.

Total supply amount of free fluorine during the period (hereinafter referred to as the total supply amount)
Let R, (g) be R, and the total number of cans processed be N. If the volume of the processing liquid is V, then the error in the total replenishment amount is V x (C2
-C, ), so the appropriate total supply amount is R, -Vx(C2
-C,). Similarly, taking other constant conditions m2 (minutes), the concentration is C3, C4, the total supply amount is R2, and the total number of cans processed is N.
2, the appropriate total supply amount is R2-V x (C4-C3)
It is.

From this, formula-2 R, -Vx (C2-C,) = N, ×a + b × T, R2-
By solving the simultaneous equations of V×(C4-C3)=N2xa+b×T2, appropriate a and b values can be obtained.

A specific example of a method for solving simultaneous equations using a computer is the Gauss-Jordan method, which is generally well known and will therefore be omitted here. The above control process is shown below by substituting actual values.

First, the initial values of a and b are also determined as bo, respectively, as follows. ro = 0.002 female/can, ~ = 0.2 acid/min From this, the computer calculates the replenishment amount using the formula r (g/min) = n (can/min) x 0.0020 g can + 0.25 g min. Processing was performed while calculating and replenishing.

Processing was carried out at a rate of 200 cans/min for the first hour and at a rate of 60 cans/min for the second hour. The result was as follows. The set concentration was 0.17 females/unit (17 melon blood), and the volume V of the treatment liquid was 2000 units. First hour (processed on a 20 minute basis) Initial concentration C, = 0.1
70g pieces (17 flies) Final concentration C2 = 0.172g
Noku (17 Sukka) Total number of cans processed N, = 1240 Bogo total supply amount R, = 1240 Boko x 0.0020g/can + 0.25
g/min x 60 min = 39. The next 1 hour of foundation (processing on a base of 60 rocks/min) Initial concentration C3 = 0.17 / So (]7 blood) Last concentration C4 = 0.18 * / Evening (183 Cape) Total processing can Number N2 = 3540 Danko total supply amount R2 = 3540 Hanko x 0.0020g/can + 0.25g portion x 6 powder 2 = 8
5. The values above the total are stored inside the computer, and the computer automatically corrects the values of a and b by solving the following simultaneous equations using these values.

39. Total -2000 sox (0.17 clothes/evening -0.170
g/so) = 1240 Bogo Xa + bX 60 minutes 35. Foundation - 2000 evenings x (0.18 rounds / so - 0.17 evenings) 23540 bows 5 x a + b x 6 minutes, . Since a and b have been corrected in this way for a = 0.00122g can and b = 0.345g, the subsequent control will be as follows:
This is done using b.

As the density changes become slower as a and b approach appropriate values, a certain period of time (60 minutes in the above example) used for correction.
By making the time longer, more precise correction becomes possible, and the density can be stably maintained at a constant value. FIG. 2 is a graph showing the results of ON-OFF control using conventional concentration measurement under the same processing conditions as in the previous example. In this method, there is an overshoot because replenishment is stopped after the concentration exceeds the set value of 0.17 g/night, and the opposite occurs during the concentration reduction process, resulting in a considerable control error. Come out. Also, this process differs depending on the number of cans to be processed. FIG. 3 is a graph showing the results obtained by carrying out the process using the apparatus of the present invention under the same processing conditions as in the previous example, and performing control under the same conditions after sufficient verification correction was performed.

In this control, replenishment is performed in advance according to the number of cans to be processed, so there is no large change in concentration unlike in the conventional system, and the concentration is stabilized to be approximately constant. Next, we will discuss failure detection of the concentration measuring device.

Concentration measuring instruments, especially the fluorine ion meter shown in this example,
Due to deterioration of the ion electrode portion or the adhesion of dirt, the ion electrode may exhibit a value considerably different from the actual concentration. In such cases, the secondary feedback method performs control based on the value indicated by the concentration measuring device, so although it appears to be controlling the concentration to a normal level on the control device, the actual concentration may be a considerably different value. There were times when line troubles occurred. The means of the present invention performs replenishment using the formula: replenishment amount = number of cans processed × unit consumption amount + mechanical loss r na b (g/min) (cans/min) (g/cans) (g/min) conduct.

The values of a and b are constants determined by the processing line and processing can, and vary somewhat depending on the set concentration, temperature, conveyance speed, etc.
However, since the set concentration, temperature, conveyance speed, etc. are not of a nature that changes significantly, the values of a and b fall within a certain range. However, if the concentration measuring device becomes abnormal, the values of a and b will significantly deviate from the above-mentioned fixed range due to its continued use. This is because the values of a and b are corrected by the above-mentioned formula-2, but the values of C, , C2, C3, and C4 in formula-2 are the concentration values measured by the concentration measuring device. Therefore, if the concentration measuring device becomes abnormal, the values of C, ~ C4 will become abnormal values,
As a result, the values of a and b also become abnormal values. In the present invention, the computer always has a, b
The computer is programmed to monitor the values of a and b, and if one or both of them reach the limits of the set range, the computer is programmed to immediately and automatically issue an alarm. Since the system is designed to notify the cause of the abnormal value, that is, the abnormality of the concentration measuring device, the on-site workers are informed by the alarm and can quickly replace the concentration measuring device with a normal concentration measuring device.

Therefore, it has become possible to quickly suppress abnormalities in the values of a and b. In this way, abnormalities in the mulberry agent replenishment amount r are suppressed, and as a result, the concentration of the processing liquid is suppressed from falling outside the set range. It is played.

[Brief Description of the Drawings] Fig. 1 is a block diagram schematically showing an automatic control device for metal surface treatment liquid according to the present invention, and Fig. 2 shows a case where metal surface treatment liquid is controlled by the conventional method. The graph in FIG. 3 is a graph when control is performed using the apparatus of the present invention. 1... Processing membrane, 2... Spray pump, 3... Spray nozzle, 4... Aluminum can, 5... Can counter, 6 ...Concentration measuring device, 7...Arithmetic controller, 8,9...Replenishment pump, 10...Main replenishment agent, 11...Substitute replenisher. Figure 2 Figure 3 Figure Ship

Claims (1)

[Scope of Claims] 1. In a metal surface treatment line that has a means for measuring the concentration of a metal surface treatment solution, a means for measuring the number of processed metal products or a processing speed, and a means for supplying chemicals to the treatment solution, When surface-treating a product, a computer measures the number of metal products to be treated per unit time or calculates the area to be treated, and combines that value with a pre-memorized number of metal products to be treated or the amount of chemical consumption per unit area. From the mechanical loss amount of the chemical per unit time, calculate the amount of chemical to be replenished to the metal surface treatment liquid per unit time according to the formula below, and control the concentration of the surface treatment liquid within the set range by replenishing it. An automatic control device for metal surface treatment liquids featuring: r=n×a+b Amount of drug replenishment Number of processed items (units/minute) Amount of drug consumption (g/unit)
*Mechanical (g/min) or treatment area (m^2/min) or (g/m^2) loss (g/min) (Note) *Loss not due to surface treatment of metal products, e.g. empty spray Amount of chemical lost due to decomposition of components in the metal surface treatment solution and loss due to metal surface treatment equipment 2 Amount of chemical consumed per number of treated items or treated area by computer and chemical consumption per unit time The automatic control device for a metal surface treatment liquid according to claim 1, wherein the automatic control device for a metal surface treatment liquid automatically corrects the amount of loss.