Chromium-free passivation tin plate film thickness automatic control device and control method

Abstract

The invention relates to a chromate-free passivation tin plate film thickness automatic control device which comprises a chromate-free passivation solution stock solution tank, a chromate-free passivation solution preparation tank, a solution supply pump, a working tank, an injection pump, a chromate-free passivation solution flowmeter, a compressed air pressure regulating valve, a nozzle and a wringing roller. A chromate-free passivation solution preparation tank and a solution supply pump are arranged between the chromate-free passivation solution stock solution tank and the working tank, a chromate-free passivation solution in the working tank is conveyed into a nozzle through an injection pump, a pair of wringing rollers is arranged at an outlet of a tin plate sprayed with the chromate-free passivation solution, and the whole scheme is ingenious in design, high in automation degree, convenient to use, safe, efficient and high in efficiency. The production of various specifications of tin-plated plates can be realized according to the requirements of the tin-plated plates with different purposes, and the automatic operation of the chromium-free passivation process and the automatic control of the chromium-free passivation film are ensured, so that the accurate control of the chromium-free passivation film amount of the tin-plated plate is realized.

Description

Technical Field

[0001] The invention relates to the production of a chromium-free passivated tinplate, in particular to an automatic control device and method for the film thickness of a chromium-free passivated tinplate, and belongs to the technical field of tinplate production in the metallurgical industry. Background Art

[0002] Tinplate is an important food packaging material, and corrosion resistance is an important quality indicator. Depending on the packaging object, the requirements for corrosion resistance vary. The corrosion resistance of tinplate depends on the tin layer on the surface of the tinplate and the passivation film on the outer surface of the tin layer. The amount of the passivation film has a huge impact on the corrosion resistance. There are two common passivation methods for tinplate: chromate passivation and chromium-free passivation. Since chromate contains highly toxic hexavalent chromium, the scope of use of chromate passivation products used for food assurance will become narrower and narrower. For example, the EU REACH Directive, RoHS regulations, and national standards GB4806 have all put forward restrictions on hexavalent chromium in tinplate. Chromium-free passivation will inevitably become a future development trend, and the use of chromium-free passivation products will be fully promoted at that time.

[0003] Chromium-free passivation is to use a passivating agent that does not contain hexavalent chromium to form a chromium-free passivation film on the surface of the tin layer, which plays a role in preventing the tin layer from being oxidized and corroded. Chromium-free passivation can be generally divided into two categories: inorganic and organic. Inorganic passivation mainly includes molybdate, tungstate, titanium zirconium system, phosphorus silicon system, etc.; organic passivation includes organic substances such as phytic acid and silane. There are two existing process technologies for chromium-free passivation, one is electrolysis and the other is spraying. The spraying method is to evenly spray the chromium-free passivation liquid onto the surface of the tinplate, and form a chromium-free passivation film after drying. Since the spraying method is easy to control the amount of the film, the formed chromium-free passivation film has excellent corrosion resistance and coating performance, so the preparation of chromium-free passivation film by spraying has gradually become the mainstream technology for chromium-free passivation of tinplate.

[0004] In order to make the chromium-free passivated tinplate have better corrosion resistance, it is crucial to control the amount of chromium-free passivation film and the uniformity of the chromium-free passivation film. Although the spraying method is easy to control the thickness of the chromium-free passivation film, it is still necessary to continuously optimize the spraying mode and method, and realize automatic control of the chromium-free passivation film according to the chromium-free passivation process parameters, so as to meet the requirements of tinplate for different purposes for the amount of chromium-free passivation film.

[0005] The core technology of the spray-on chromium-free passivation method is to spray the chromium-free passivation liquid evenly onto the surface of the plate according to the requirements of different tinplates, and to realize the automatic control of the chromium-free passivation film according to the chromium-free passivation process. CN211057225U discloses a chromium-free passivation device, which uses a rotary spraying technology to spray the diluted chromium-free passivation liquid onto the surface of the plate. This technology is the current mainstream chromium-free passivation equipment. The main problem of using the rotary spraying method to spray the chromium-free passivation liquid is that it is difficult to ensure the uniform distribution of the chromium-free passivation liquid on the surface of the plate, which increases the consumption of the chromium-free passivation liquid and cannot realize the automatic control of the chromium-free passivation film. Therefore, based on the spray-on chromium-free passivation liquid, it is urgent to invent a chromium-free passivation tinplate film thickness automatic control device and method, which is extremely important for improving the green manufacturing technology, product quality and production process automation control of the tinplate. Therefore, a new solution is urgently needed to solve the above technical problems. Summary of the invention

[0006] The present invention is aimed at the problems existing in the prior art, and provides a chromium-free passivation tinplate film thickness automatic control device. The technical solution realizes the automatic operation of the chromium-free passivation process and the automatic control of the amount of chromium-free passivation film through PLC control. The whole solution is cleverly designed, highly automated, easy to use, safe and efficient. It can realize the production of tinplates of various specifications according to the requirements of tinplates for different purposes, ensure the automatic operation of the chromium-free passivation process and the automatic control of the chromium-free passivation film, thereby realizing the precise control of the amount of chromium-free passivation film on the tinplate.

[0007] In order to achieve the above-mentioned purpose, the technical scheme of the present invention is as follows: a chromium-free passivation tinplate film thickness automatic control device, the control device comprises a chromium-free passivation liquid stock tank 1, a chromium-free passivation liquid preparation tank 2, a liquid supply pump 3, a working tank 4, a jet pump 5, a chromium-free passivation liquid flowmeter 6, a compressed air pressure regulating valve 7, a nozzle 8 and a squeeze roller 9, a chromium-free passivation liquid preparation tank 2 and a liquid supply pump 3 are arranged between the chromium-free passivation liquid stock tank 1 and the working tank 4, the chromium-free passivation liquid in the working tank 4 is transported to the nozzle 8 through the jet pump 5, and a pair of squeeze rollers 9 are arranged at the outlet of the tinplate sprayed with the chromium-free passivation liquid. The chromium-free passivation liquid stock tank 1 in the automatic control device is used to contain the chromium-free passivation liquid stock, and the chromium-free passivation liquid stock can be added to the chromium-free passivation liquid preparation tank 2 through a liquid supply pump; a liquid supply pump 3 is arranged between the chromium-free passivation liquid preparation tank 2 and the working tank 4, and is used to add the configured chromium-free passivation liquid to the working tank 4; a jet pump 5 and a chromium-free passivation liquid flow meter 6 are arranged between the working tank 4 and the nozzle 8, and the function of the jet pump 5 is to transport the chromium-free passivation liquid to the nozzle 8, and the function of the chromium-free passivation liquid flow meter 6 is to monitor the flow of the chromium-free passivation liquid flowing through the nozzle 8; a compressed air regulating valve 7 is arranged at the front end of the nozzle 8, and is used to atomize the chromium-free passivation liquid into fine liquid particles after passing through compressed air, and spray it onto the surface of the tinplate in the form of aerosol, and then the chromium-free passivation liquid sprayed onto the surface of the tinplate is squeezed out through a squeezing roller 9 to form a uniform liquid film.

[0008] Among them, the working tank 4 is equipped with liquid level control, the jet pump 5 adopts variable frequency speed regulation, the flow rate of the chromium-free passivation liquid is adjusted by the flow regulating valve of the chromium-free passivation liquid flow meter 6, the flow regulating valve is controlled by PLC, and compressed air is introduced into the nozzle 8, and the pressure of the compressed air is 0.3-0.6MPa. The working tank 4 can realize online monitoring, which is convenient for the operator to grasp the liquid level changes in time and automatically dispense the liquid according to the needs; the jet pump 5 can set the required chromium-free passivation liquid flow rate according to the thickness of the chromium-free passivation film, and automatically adjust it through the chromium-free passivation liquid flow meter 6; the compressed air regulating valve 7 at the front end of the nozzle 8 can adjust the compressed air pressure, atomize the chromium-free passivation liquid into the required particle size, and spray it evenly onto the surface of the tinplate, and then squeeze the chromium-free passivation liquid through the squeeze roller 9 to form a uniform liquid film. The automatic control device realizes the automatic control of chromium-free passivation liquid dispensing, chromium-free passivation liquid spraying, and chromium-free passivation liquid film formation, which is convenient for the high-efficiency and stable batch production of chromium-free passivation tinplate.

[0009] The chromium-free passivation liquid stock solution and deionized water are added to the chromium-free passivation liquid preparation tank 2 in a certain proportion, and the chromium-free passivation liquid is prepared after stirring for 5 to 10 minutes. The prepared chromium-free passivation liquid is added to the working tank 4 through the liquid supply pump 3; the working tank 4 is equipped with a liquid level control, and the chromium-free passivation liquid in the working tank 4 is transported to the nozzle 8 through the jet pump 5. The jet pump 5 adopts variable frequency speed regulation to adjust the injection amount; compressed air is introduced into the nozzle 8 at the same time, and the pressure of the compressed air is 0.3 to 0.6 MPa. The flow rate of the chromium-free passivation liquid is adjusted by the flow regulating valve of the chromium-free passivation liquid flowmeter 6. The flow regulating valve is controlled by PLC, and the nozzle 8 is equipped with an electronic valve to adjust the valve opening. A pair of squeeze rollers 9 are provided at the outlet of the tinplate sprayed with the chromium-free passivation liquid, and the pressure of the squeeze rollers 9 can be automatically adjusted.

[0010] A method for automatically controlling the film thickness of a chromium-free passivated tinplate, the method comprising the following steps:

[0011] 1) The concentration of the chromium-free passivation solution is controlled according to the required amount of chromium-free passivation film. When the amount of chromium-free passivation film is between 0.5 and 2.0 mg / m 2 When the concentration of chromium-free passivation solution is 5% (i.e. 1 part of chromium-free passivation solution is mixed with 20 parts of deionized water), when the amount of chromium-free passivation film is between 2.0 and 5.0 mg / m 2 When the concentration of the chromium-free passivation solution is 10% (i.e. 1 part of the chromium-free passivation solution stock solution is mixed with 10 parts of deionized water);

[0012] 2) The opening K of the electronic valve in the nozzle of the control model is divided into two levels. When the amount of chromium-free passivation film is between 0.5 and 2.0 mg / m 2 When the opening degree K of the electronic valve is 50%, when the amount of chromium-free passivation film is between 2.0 and 5.0 mg / m 2 When , the opening degree K of the electronic valve is 80%;

[0013] 3) The flow rate of chromium-free passivation solution in the control model is calculated as follows:

[0014] Chromium-free passivation liquid flow rate Q = 1495 × t × W × n ÷ C ÷ K (L / min)

[0015] Where: t is the amount of chromium-free passivation film (mg / m 2 )

[0016] W Strip width (m)

[0017] n Strip running speed (m / min)

[0018] C: Chromium-free passivation solution concentration (wt%);

[0019] 4) The pressure of compressed air in the control model is calculated as follows:

[0020] The pressure of compressed air P = 0.213 × Q × C (MPa)

[0021] Where: Q is the flow rate of chromium-free passivation solution (L / min)

[0022] C is the concentration of chromium-free passivation solution (wt%);

[0023] 5) The squeeze roller pressure P in the control model is calculated as follows:

[0024] The pressure of the squeeze roller P = 1.17 × t ÷ C (MPa)

[0025] Where: t is the amount of chromium-free passivation film (mg / m 2 ))

[0026] C is the concentration of chromium-free passivation solution (wt%)

[0027] When the obtained P is less than 2MPa, the squeeze roller does not need to be put into use. When the obtained P is greater than or equal to 2MPa, the squeeze roller is put into use according to the set pressure.

[0028] 6) After the PLC system calculates the flow rate of the chromium-free passivation liquid according to the formula in 3), it controls the injection pump to set the operating parameters according to the previously calibrated parameters and starts the liquid supply;

[0029] 7) After the PLC system calculates the pressure of the compressed air according to the formula in 4), it controls the opening of the pressure regulating valve to supply compressed air to the nozzle;

[0030] 8) After the PLC system calculates the pressure of the squeeze roller according to the formula in 5), it determines whether the squeeze roller needs to be put into use based on the calculated value. If it is determined that the squeeze roller needs to be put into use, the pressure of the squeeze roller is set according to the calculated value;

[0031] 9) The entire injection system is controlled by an independent PLC. The PLC system automatically receives and feeds back instructions, realizing the automatic control of the chromium-free passivation film.

[0032] In this scheme, the chromium-free passivation liquid spraying system atomizes the chromium-free passivation liquid sprayed onto the surface of the tinplate through compressed air, and the atomized chromium-free passivation liquid is sprayed onto the surface of the tinplate under the action of compressed air, thereby achieving the requirement that the chromium-free passivation liquid sprayed onto the surface of the tinplate has a small and dense particle size. At the same time, the method adopted by this patent is to require that the chromium-free passivation liquid sprayed onto the surface of the tinplate can be changed according to the requirements of different tinplates for the amount of chromium-free passivation film and the running speed of the strip, which requires the establishment of a control model, and the model calculates the appropriate spraying process parameters according to the requirements, thereby achieving the automatic control of the amount of chromium-free passivation film.

[0033] Compared with the prior art, the present invention has the following advantages: 1) the overall structural design of the technical solution is ingenious, the degree of automation is high, the use is convenient, safe and efficient; 2) the technical solution can achieve uniform coating of chromium-free passivation liquid, and the thickness of the chromium-free passivation film can be 0.5-5.0 mg / m 2 3) The chromium-free passivation film thickness automatic control device of the present invention fully considers the uniformity of the chromium-free passivation liquid sprayed onto the surface of the tinplate, and can realize full automatic operation under the control of PLC, greatly improving the working efficiency. The automatic control device realizes the automatic control of the chromium-free passivation liquid preparation, chromium-free passivation liquid spraying, and chromium-free passivation liquid film formation, which is convenient for the high-efficiency and stable batch production of chromium-free passivation tinplate. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Control model for injection system;

[0035] Figure 2 The schematic diagram of the injection system is shown below;

[0036] In the figure: 1. chromium-free passivation liquid original liquid tank, 2. chromium-free passivation liquid preparation tank, 3. liquid supply pump, 4. working tank, 5. injection pump, 6. chromium-free passivation liquid flow meter, 7. compressed air pressure regulating valve, 8. nozzle, 9. squeeze roller. DETAILED DESCRIPTION

[0037] In order to deepen the understanding of the present invention, the present embodiment is described in detail below with reference to the accompanying drawings.

[0038] Example 1: See Figure 1-Figure 2A chrome-free passivation tinplate film thickness automatic control device, the injection system of the chrome-free passivation tinplate film thickness automatic control device comprises a chrome-free passivation liquid stock tank 1, a chrome-free passivation liquid preparation tank 2, a liquid supply pump 3, a working tank 4, an injection pump 5, a chrome-free passivation liquid flow meter 6, a compressed air pressure regulating valve 7, a nozzle 8 and a squeeze roller 9, the chrome-free passivation liquid stock and deionized water are added to the chrome-free passivation liquid preparation tank 2 in a certain proportion, and the chrome-free passivation liquid is prepared after stirring for 5 to 10 minutes. The passivation liquid is added to the working tank 4 through the liquid supply pump 3; the working tank 4 is equipped with a liquid level control, and the chromium-free passivation liquid in the working tank 4 is transported to the nozzle 8 through the jet pump 5. The jet pump 5 adopts variable frequency speed regulation and can adjust the injection amount; compressed air is simultaneously introduced into the nozzle 8, and the pressure of the compressed air is 0.3-0.6MPa. The flow rate of the chromium-free passivation liquid is adjusted by the flow regulating valve of the chromium-free passivation liquid flow meter 6. The flow regulating valve is controlled by the PLC, and the nozzle 8 is equipped with an electronic valve to adjust the valve opening. A pair of squeeze rollers 9 are provided at the outlet of the tinplate sprayed with the chromium-free passivation liquid, and the pressure of the squeeze rollers 9 can be automatically adjusted. In order to ensure the uniformity of the extremely thin chromium-free passivation film on the surface of the tinplate, first of all, the chromium-free passivation liquid sprayed onto the surface of the tinplate is required to have small and dense particles. To achieve this requirement, the method adopted by this patent is to atomize the chromium-free passivation liquid sprayed onto the surface of the tinplate by compressed air, and the atomized chromium-free passivation liquid is sprayed onto the surface of the tinplate under the action of compressed air; secondly, it is required that the chromium-free passivation liquid sprayed onto the surface of the tinplate can be changed according to the requirements of different tinplates for the amount of chromium-free passivation film and the running speed of the strip, which requires the establishment of a control model, and the model calculates the appropriate spraying process parameters according to the requirements.

[0039] The injection system is an aerosol injection system, which can adjust the pressure of compressed air, the flow rate of chromium-free passivation liquid and the nozzle opening. The entire injection system is controlled by an independent PLC. The PLC system receives parameters such as the strip running speed, strip width, chromium-free passivation film amount, and chromium-free passivation liquid concentration from the unit. After receiving these parameters, the PLC system calculates the chromium-free passivation liquid flow rate, compressed air flow rate, nozzle opening, and squeeze roller pressure through the built-in injection model. The PLC system sends these parameters to each actuator, which realizes automatic control of these parameters, thereby realizing automatic control of the chromium-free passivation film amount.

[0040] Example 2: See Figure 1-Figure 2 , a chrome-free passivation tinplate film thickness automatic control method, using independent PLC control, the PLC system receives the strip running speed, the required chrome-free passivation film amount, and the chrome-free passivation liquid concentration given by the unit, and the control model calculates the flow rate of the chrome-free passivation liquid, the compressed air pressure, the nozzle opening, the pressure of the squeeze roller and other parameters according to the received parameters, and the injection system automatically runs the injection process according to these parameters. The method is as follows;

[0041] 1) The concentration of chromium-free passivation solution is controlled according to the required amount of chromium-free passivation film. When the amount of chromium-free passivation film is between 0.5 and 2.0 mg / m 2 When the concentration of chromium-free passivation solution is 5% (i.e. 1 part of chromium-free passivation solution is mixed with 20 parts of deionized water), when the amount of chromium-free passivation film is between 2.0 and 5.0 mg / m 2 The concentration of the chromium-free passivation solution is 10% (i.e., 1 part of chromium-free passivation solution stock solution is mixed with 10 parts of deionized water).

[0042] 2) The opening K of the electronic valve in the nozzle of the control model is divided into two levels. When the amount of chromium-free passivation film is between 0.5 and 2.0 mg / m 2 When the opening K of the electronic valve is 50%, the amount of chromium-free passivation film is between 2.0 and 5.0 mg / m 2 When , the opening degree K of the electronic valve is 80%.

[0043] 3) The flow rate of chromium-free passivation solution in the model is calculated as follows:

[0044] Chromium-free passivation liquid flow rate Q = 1495 × t × W × n ÷ C ÷ K (L / min)

[0045] Where: t is the amount of chromium-free passivation film (mg / m 2 )

[0046] W Strip width (m)

[0047] n Strip running speed (m / min)

[0048] C Chromium-free passivation solution concentration (wt%)

[0049] 4) The pressure of compressed air in the model is calculated as follows:

[0050] The pressure of compressed air P = 0.213 × Q × C (MPa)

[0051] Where: Q is the flow rate of chromium-free passivation solution (L / min)

[0052] C is the concentration of chromium-free passivation solution (wt%)

[0053] 5) The squeeze roller pressure P in the model is calculated as follows:

[0054] The pressure of the squeeze roller P = 1.17 × t ÷ C (MPa)

[0055] Where: t is the amount of chromium-free passivation film (mg / m 2 ))

[0056] C is the concentration of chromium-free passivation solution (wt%)

[0057] When the obtained P is less than 2MPa, the squeeze roller does not need to be put into use. When the obtained P is greater than or equal to 2MPa, the squeeze roller is put into use at the set pressure.

[0058] 6) After the PLC system calculates the flow rate of the chromium-free passivation liquid according to the formula in 3), it controls the injection pump to set the operating parameters according to the previously calibrated parameters and starts the liquid supply.

[0059] 7) After the PLC system calculates the pressure of the compressed air according to the formula in 4), it controls the opening of the pressure regulating valve to supply compressed air to the nozzle.

[0060] 8) After the PLC system calculates the pressure of the squeeze roller according to the formula in 5), it determines whether the squeeze roller needs to be put into use based on the calculated value. If it is determined that the squeeze roller needs to be put into use, the pressure of the squeeze roller is set according to the calculated value.

[0061] 9) The entire injection system is controlled by an independent PLC. The PLC system automatically receives and feeds back instructions, realizing the automatic control of the chromium-free passivation film.

[0062] It should be noted that the above embodiments are not intended to limit the protection scope of the present invention, and equivalent changes or substitutions made on the basis of the above technical solutions all fall within the protection scope of the claims of the present invention.

Claims

1. A chromium-free passivation tinplate film thickness automatic control device, characterized in that: The control device comprises a chromium-free passivation liquid original liquid tank, a chromium-free passivation liquid preparation tank, a liquid supply pump, a working tank, a jet pump, a chromium-free passivation liquid flow meter, a compressed air pressure regulating valve, a nozzle and a squeeze roller. A chromium-free passivation liquid preparation tank and a liquid supply pump are arranged between the chromium-free passivation liquid original liquid tank and the working tank. The chromium-free passivation liquid in the working tank is transported to the nozzle through the jet pump. A pair of squeeze rollers are arranged at the outlet of the tinplate sprayed with the chromium-free passivation liquid.

2. The chromium-free passivation tinplate film thickness automatic control device according to claim 1 is characterized in that , the working tank has liquid level control, and the jet pump adopts variable frequency speed regulation.

3. The chromium-free passivation tinplate film thickness automatic control device according to claim 2 is characterized in that ,The flow rate of chromium-free passivation liquid is adjusted by the flow control valve of the chromium-free passivation liquid flow meter, and the flow control valve is controlled by PLC.

4. The chromium-free passivation tinplate film thickness automatic control device according to claim 3 is characterized in that , compressed air is introduced into the nozzle, and the pressure of the compressed air is 0.3~0.6MPa.

5. A method for automatically controlling the film thickness of a chromium-free passivated tinplate, characterized in that: Using the control device according to any one of claims 1 to 4, the method comprises the following steps: 1) The concentration of the chromium-free passivation solution is controlled according to the required amount of chromium-free passivation film. When the amount of chromium-free passivation film is between 0.5 and 2.0 mg / m 2 When the concentration of chromium-free passivation solution is 5% (i.e. 1 part of chromium-free passivation solution is mixed with 20 parts of deionized water), when the amount of chromium-free passivation film is between 2.0 and 5.0 mg / m 2 When the concentration of the chromium-free passivation solution is 10% (i.e. 1 part of the chromium-free passivation solution stock solution is mixed with 10 parts of deionized water); 2) The opening K of the electronic valve in the nozzle of the control model is divided into two levels. When the amount of chromium-free passivation film is between 0.5 and 2.0 mg / m 2 When the opening degree K of the electronic valve is 50%, when the amount of chromium-free passivation film is between 2.0 and 5.0 mg / m 2 When , the opening degree K of the electronic valve is 80%; 3) The flow rate of chromium-free passivation solution in the control model is calculated as follows: Chromium-free passivation liquid flow rate Q = 1495 × t × W × n ÷ C ÷ K (L / min) Where: t is the amount of chromium-free passivation film (mg / m 2 ) W Strip width (m) n Strip running speed (m / min) C: Chromium-free passivation solution concentration (wt%); 4) The pressure of compressed air in the control model is calculated as follows: The pressure of compressed air P = 0.213 × Q × C (MPa) Where: Q is the flow rate of chromium-free passivation solution (L / min) C is the concentration of chromium-free passivation solution (wt%); 5) The squeeze roller pressure P in the control model is calculated as follows: The pressure of the squeeze roller P = 1.17 × t ÷ C (MPa) Where: t is the amount of chromium-free passivation film (mg / m 2 )) C is the concentration of chromium-free passivation solution (wt%) When the obtained P is less than 2MPa, the squeeze roller does not need to be put into use. When the obtained P is greater than or equal to 2MPa, the squeeze roller is put into use according to the set pressure. 6) After the PLC system calculates the flow rate of the chromium-free passivation liquid according to the formula in 3), it controls the injection pump to set the operating parameters according to the previously calibrated parameters and starts the liquid supply; 7) After the PLC system calculates the pressure of the compressed air according to the formula in 4), it controls the opening of the pressure regulating valve to supply compressed air to the nozzle; 8) After the PLC system calculates the pressure of the squeeze roller according to the formula in 5), it determines whether the squeeze roller needs to be put into use based on the calculated value. If it is determined that the squeeze roller needs to be put into use, the pressure of the squeeze roller is set according to the calculated value; 9) The entire injection system is controlled by an independent PLC. The PLC system automatically receives and feeds back instructions, realizing the automatic control of the chromium-free passivation film.

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