Degreasing agent and body-in-white pretreatment process

Abstract

The invention provides a degreasing agent and a body-in-white pretreatment process. The degreasing agent comprises a compound agent, and the compound agent comprises the following components in percentage by weight: 1%-5% of hydroxide, 50%-60% of carbonate, 20%-30% of silicate, 5%-10% of sodium pyrophosphate and 13%-20% of a chelating agent. The body-in-white pretreatment process comprises the following steps: a flood water washing procedure: washing and preheating a plate of a body-in-white; a pre-degreasing step in which a pre-degreasing bath solution is sprayed onto the surface of the plate by means of spraying; a main degreasing procedure, specifically, a main degreasing bath solution containing the degreasing agent is used for conducting degreasing treatment on the plate, the free alkalinity of the main degreasing bath solution is controlled to range from 16 Pt to 19 Pt, and the oil content of the main degreasing bath solution is controlled to be smaller than 3.0 g / L; and an industrial water washing procedure: washing the plate to remove the main degreasing bath solution remaining on the surface of the plate.

Description

Technical Field

[0001] The present application relates to the field of vehicle processing, and in particular to a degreasing agent and a body-in-white pretreatment process. Background Art

[0002] Before the paint treatment is applied to the body-in-white of a car, it is usually necessary to perform pre-treatment on the body-in-white. The main function of the pre-treatment is to remove oil stains on the surface of the body-in-white, form a conversion film, enhance the bonding strength between the body-in-white and the subsequent paint coating, effectively prevent the coating from peeling or blistering, and significantly improve the corrosion resistance of the coating. However, the existing body-in-white pre-treatment process has problems such as poor treatment effect and unreasonable process flow. How to solve the above problems is what technicians in this field need to consider. Summary of the invention

[0003] In order to solve the problems faced in the prior art, the embodiments of the present application provide a degreasing agent and a body-in-white pretreatment process.

[0004] An embodiment of the present application provides a degreasing agent, which includes a compounding agent. In terms of weight percentage, the compounding agent includes: 1% to 5% hydroxide, 50% to 60% carbonate, 20% to 30% silicate, 5% to 10% sodium pyrophosphate and 13% to 20% chelating agent.

[0005] In one embodiment, the hydroxide includes sodium hydroxide and / or potassium hydroxide, the carbonate includes sodium carbonate and / or potassium carbonate, the silicate includes sodium metasilicate, and the chelating agent includes sodium gluconate and / or sodium tripolyphosphate.

[0006] Furthermore, the degreasing agent of the present application reduces the surface tension of the degreasing tank liquid containing the degreasing agent by improving the degreasing agent formula design, and makes the surface tension of the degreasing tank liquid increase by no more than 2mN / m after long-term use. Thereby improving and maintaining the wettability and penetration effect of the degreasing tank liquid, maintaining the degreasing effect and increasing the service life of the degreasing tank liquid, and reducing the frequency of degreasing tank changes. In addition, the emulsification and dispersibility of the degreasing tank liquid are improved, while the alkalinity of the degreasing agent is improved, and the saponification ability of the degreasing tank liquid on oil stains is strengthened, thereby comprehensively improving the degreasing ability of the degreasing agent on the plate.

[0007] The present application also provides a body-in-white pretreatment process, which includes the following steps:

[0008] Flood washing process: washing and preheating the body-in-white panels;

[0009] Pre-degreasing process: spraying the pre-degreasing tank liquid onto the surface of the plate by spraying;

[0010] Main degreasing process: using a main degreasing tank liquid containing a degreasing agent as described in any one of the above embodiments to degrease the plate, controlling the free alkalinity of the main degreasing tank liquid to be in the range of 16Pt to 19Pt, and controlling the oil content of the main degreasing tank liquid to be less than 3.0g / L;

[0011] Industrial water washing process: washing the plate to remove the main degreasing tank liquid remaining on the surface of the plate.

[0012] In one embodiment, the total alkalinity of the main degreasing tank liquid is controlled to be in the range of 26Pt to 32Pt, and the ratio of the total alkalinity of the main degreasing tank liquid to the free alkalinity of the main degreasing tank liquid is controlled to be less than or equal to 2.

[0013] In one embodiment, the main degreasing process includes the following steps:

[0014] Using the main degreasing tank liquid, spraying the plate around by spraying;

[0015] Immersing the sprayed plate in the main degreasing tank liquid;

[0016] Using the main degreasing tank liquid, spraying the immersed plate around by spraying;

[0017] The temperature of the main degreasing tank liquid is controlled in the range of 45°C to 55°C, and the pressure of the spraying is controlled in the range of 0.15Mpa to 0.2Mpa.

[0018] In one embodiment, when the plate is a zinc-magnesium-aluminum coated steel plate, a plate screening process is further included before the above steps, and the plate screening process includes the following steps:

[0019] Taking a plurality of the plates, and cleaning the surfaces of the plates;

[0020] Using a dyne pen to perform multiple measurements on the surfaces of the plurality of cleaned plates to obtain surface energy values ​​of the plurality of plates;

[0021] Taking the average value of the surface energy values ​​of the plurality of plates, if the average value is greater than or equal to 26 mN / m, the corresponding plate is determined to be qualified, and if the average value is less than 26 mN / m, the corresponding plate is determined to be unqualified;

[0022] The qualified plates are put into the subsequent steps.

[0023] In one embodiment, the pre-degreasing tank liquid is supplemented by the main degreasing tank liquid through overflow;

[0024] The free alkalinity of the pre-degreasing tank solution is controlled to be in the range of 16Pt to 19Pt, and the total alkalinity of the pre-degreasing tank solution is controlled to be in the range of 26Pt to 32Pt;

[0025] The temperature range of the pre-degreasing tank liquid is controlled to be 45° C. to 55° C., and the pressure range of the spraying is controlled to be 0.15 MPa to 0.2 MPa.

[0026] In one embodiment, the industrial water washing process comprises the following steps:

[0027] The first industrial water washing process: using the first water washing tank liquid to rinse the plate by spraying, controlling the pH value of the first water washing tank liquid to be in the range of 7 to 11.5, and controlling the spraying pressure range to be in the range of 0.15Mpa to 0.25Mpa;

[0028] Second industrial water washing process: Use the second water washing tank liquid to clean the plate by spraying and soaking, control the pH value of the second water washing tank liquid to be in the range of 7 to 11.5, and control the spraying pressure range to be 0.15Mpa to 0.25Mpa.

[0029] In one embodiment, the body-in-white pre-treatment process further includes the following steps:

[0030] Surface conditioning step: immersing the plate in a surface conditioning bath, wherein the surface conditioning bath comprises zinc phosphate;

[0031] Phosphating process: immerse the plate treated by the surface adjustment process in a phosphating bath for phosphating, control the temperature of the phosphating bath to be in the range of 33°C to 40°C, control the total acidity of the phosphating bath to be in the range of 20Pt to 22Pt, and control the free acidity of the phosphating bath to be in the range of 0.5Pt to 1Pt.

[0032] In one embodiment, the flood water washing process includes the following steps:

[0033] The plate is sprayed and rinsed at the process entrance, and the spray flow rate at the entrance is controlled to be 120m 3 / h;

[0034] Use multiple spray rings to spray the plate, and control the spray pressure range to be 0.15Mpa to 0.25Mpa;

[0035] The plate is sprayed and rinsed at the process exit, and the spray flow rate at the exit is controlled to be 120m 3 / h;

[0036] Among them, the water washing temperature range of the flood water washing process is controlled to be normal temperature and higher to not higher than 50°C.

[0037] Furthermore, the body-in-white pretreatment process provided in the embodiment of the present application maintains the degreasing activity of the degreasing agent for a long time and ensures the degreasing effect of the degreasing agent by determining the process requirements such as the degreasing tank liquid addition specification, the construction parameter setting and the tank change cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Schematic diagram of the surface morphology of zinc-magnesium-aluminum coated steel plate before treatment.

[0039] Figure 2 This is a schematic diagram of the surface morphology of a plate with coarse phosphating crystals due to poor degreasing.

[0040] Figure 3 This is a schematic diagram of the appearance of a plate with appearance defects due to poor degreasing.

[0041] Figure 4 A schematic diagram of a body-in-white pre-treatment process provided in one embodiment of the present application.

[0042] Figure 5 A schematic diagram of the process flow of a body-in-white pre-treatment process provided in one embodiment of the present application.

[0043] Figure 6 A schematic flow chart of a plate screening process of a body-in-white pre-treatment process provided in one embodiment of the present application.

[0044] Figure 7 A schematic flow chart of a flood water washing step of a body-in-white pre-treatment process provided in one embodiment of the present application.

[0045] Figure 8 A schematic flow chart of the main degreasing step of the body-in-white pretreatment process provided in one embodiment of the present application.

[0046] Fig. 9 A schematic flow chart of an industrial water washing sequence for a body-in-white pre-treatment process according to an embodiment of the present application.

[0047] Fig.10 This is a schematic diagram of the degreasing tank liquid after use in the comparative example provided in this application.

[0048] Fig.11 A schematic diagram of the degreasing tank liquid after use in the embodiments provided in this application.

[0049] Fig.12 This is a schematic diagram of the phosphating appearance of a plate (zinc-magnesium-aluminum coated steel plate) treated with the degreasing agent and white body pre-treatment process provided in an embodiment of the present application.

[0050] Fig.13This is a schematic diagram of the surface morphology of phosphating crystals of a plate (zinc-magnesium-aluminum coated steel plate) treated with the degreasing agent and white body pretreatment process provided in an embodiment of the present application.

[0051] Fig.14 Schematic diagram to improve the appearance of the car body after the front degreasing treatment.

[0052] Fig.15 This is a schematic diagram of the appearance of a car body after being processed using the degreasing agent and white body pre-treatment process provided in an embodiment of the present application.

[0053] The following specific implementation methods will further illustrate the present application in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0054] The following description will refer to the accompanying drawings to more fully describe the content of the present application. Shown in the accompanying drawings are exemplary embodiments of the present application. However, the present application can be implemented in many different forms and should not be construed as being limited to the exemplary embodiments set forth herein. These exemplary embodiments are provided to make the present application thorough and complete, and to fully convey the scope of the present application to those skilled in the art. Similar reference numerals represent identical or similar components.

[0055] The terms used herein are only used for the purpose of describing specific exemplary embodiments and are not intended to limit the present application. As used herein, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to also include the plural forms. In addition, when used herein, "including" and / or "comprising" and / or "having", integers, steps, operations, components and / or components, but do not exclude the existence or addition of one or more other features, regions, integers, steps, operations, components and / or groups thereof.

[0056] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those of ordinary skill in the art to which this application belongs. In addition, unless explicitly defined herein, terms such as those defined in general dictionaries should be interpreted as having a meaning consistent with their meaning in the relevant technology and the content of this application, and will not be interpreted as an idealized or overly formal meaning.

[0057] Generally, the degreasing agent used for pretreatment of automobile body-in-white is mainly composed of alkali components, chelating agents and surfactants. The degreasing agent mainly removes the oil stains attached to the surface of the plate through saponification, emulsification, dispersion and other effects, and dissolves in the degreasing tank liquid. The emulsified oil in the degreasing tank liquid is separated from the oil and water by high-temperature demulsification, and the oil stains are discharged from the degreasing tank system to maintain a good degreasing effect.

[0058] Generally, the sheet materials used for automobile body-in-white may include metal-free coated steel sheets, hot-dip galvanized steel sheets, electro-galvanized steel sheets, aluminum alloy sheets, aluminum-silicon coated sheets, and zinc-magnesium-aluminum coated steel sheets. Among them, zinc-magnesium-aluminum coated steel sheets have excellent corrosion resistance and fracture self-repairing ability, and their forming performance is better than that of hot-dip galvanized steel sheets and electro-galvanized steel sheets, so they are widely used in automobile body-in-white. Based on the production level of general steel plate galvanizing lines, the aluminum and / or magnesium elements in the coating alloy metal are easily enriched on the coating surface, and the chemical properties of aluminum and / or magnesium elements are very active and easily oxidized. At the same time, the eutectic structure of aluminum and / or magnesium elements is easy to form micron-level grooves on the surface of the sheet (such as Figure 1 As shown in the figure). The greater the surface tension of the degreasing liquid used to clean the plate, the smaller the contact area between the degreasing liquid and the plate surface. Its surface structure has characteristics close to the lotus leaf effect (super hydrophobicity), resulting in the zinc-magnesium-aluminum coated steel plate. The surface energy is usually low, and the degreasing liquid is difficult to wet, spread and penetrate in the gullies, resulting in poor oil treatment effect, affecting the adsorption of effective active ingredients in subsequent surface adjustment, and ultimately resulting in phosphating film failure or coarse phosphating crystals (such as Figure 2 As shown), the phosphate coating produces performance defects such as blooming and / or appearance defects (such as Figure 3 shown).

[0059] Correspondingly, the present application provides a degreasing agent and a body-in-white pretreatment process. The degreasing agent includes a compounding agent, which contains, by weight percentage: 1% to 5% hydroxide, 50% to 60% carbonate, 20% to 30% silicate, 5% to 10% sodium pyrophosphate and 13% to 20% chelating agent. The body-in-white pretreatment process includes the following steps: a torrent water washing process, which rinses and preheats the body-in-white sheet; a pre-degreasing process, which uses a spraying method to spray the pre-degreasing tank liquid on the surface of the sheet; a main degreasing process, which uses a main degreasing tank liquid containing the degreasing agent to degrease the sheet, controls the free alkalinity range of the main degreasing tank liquid to be 16Pt to 19Pt, and controls the oil content of the main degreasing tank liquid to be less than 3.0g / L; an industrial water washing process, which rinses the sheet to remove the main degreasing tank liquid remaining on the surface of the sheet.

[0060] Furthermore, the degreasing agent of the present application reduces the surface tension of the degreasing tank liquid (at least the pre-degreasing tank liquid and the main degreasing tank liquid, respectively) containing the degreasing agent by improving the degreasing agent formula design. At the same time, the surface tension of the degreasing tank liquid does not increase by more than 2mN / m after long-term use, thereby improving and maintaining the wettability and penetration effect of the degreasing tank liquid, maintaining the degreasing effect and improving the service life of the degreasing tank liquid, and reducing the frequency of degreasing tank changes. In addition, the emulsification and dispersion properties of the degreasing tank liquid are improved, while the alkalinity of the degreasing agent is improved, and the saponification ability of the degreasing tank liquid on oil stains is enhanced, thereby comprehensively improving the degreasing ability of the degreasing agent on the sheet material. The white body pretreatment process provided in the embodiment of the present application maintains the degreasing activity of the degreasing agent for a long time and ensures the degreasing effect of the degreasing agent by determining the process requirements such as the degreasing tank liquid feeding specification, construction parameter setting and tank change cycle.

[0061] The specific implementation methods of the present application are further described in detail below with reference to the accompanying drawings.

[0062] like Figure 4 As shown, the embodiment of the present application provides a body-in-white pre-treatment process, which includes the following steps:

[0063] Flood washing process: washing and preheating the body-in-white panels;

[0064] Pre-degreasing process: spray the pre-degreasing tank liquid onto the surface of the plate by spraying;

[0065] Main degreasing process: Use the main degreasing tank liquid containing degreasing agent to degrease the plate, control the free alkalinity range of the main degreasing tank liquid to be 16Pt to 19Pt, and control the oil content of the main degreasing tank liquid to be less than 3.0g / L;

[0066] Industrial water washing process: rinse the board to remove the main degreasing tank liquid remaining on the surface of the board.

[0067] The present application also provides a degreasing agent that can be applied to the above-mentioned body-in-white pretreatment process. The degreasing agent includes a compounding agent, which contains, by weight percentage, 1% to 5% of hydroxide, 50% to 60% of carbonate, 20% to 30% of silicate, 5% to 10% of sodium pyrophosphate, and 13% to 20% of chelating agent.

[0068] In one embodiment, the hydroxide includes sodium hydroxide and / or potassium hydroxide, the carbonate includes sodium carbonate and / or potassium carbonate, the silicate includes sodium metasilicate, and the chelating agent includes sodium gluconate and / or sodium tripolyphosphate.

[0069] In one embodiment, the compounding agent further includes an alkali component and a chelating agent, and the compounding agent contains 1% to 5% of sodium hydroxide, 50% to 60% of sodium carbonate, 20% to 30% of sodium metasilicate, 5% to 10% of sodium pyrophosphate and 13% to 20% of a chelating agent in terms of percentage.

[0070] In this embodiment, the content of hydroxide in the compounding agent may specifically be 2%, 3%, or 4%.

[0071] In this embodiment, the content of carbonate in the compound can specifically be 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, or 59%.

[0072] In this embodiment, the content of silicate in the compounding agent can specifically be 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, or 29%.

[0073] In this embodiment, the content of sodium pyrophosphate in the compound can be 6%, 7%, 8% or 9%.

[0074] In this embodiment, the content of the chelating agent in the compound can be 14%, 15%, 16%, 17%, 18%, 19%. The amount of the chelating agent can be adjusted according to the actual water quality (solvent) to obtain a degreasing agent with better comprehensive performance.

[0075] It can be understood that the degreasing agent of the present application, by improving the degreasing agent formula design, appropriately reducing the ratio of hydroxide and increasing the ratio of carbonate, reduces the surface tension of the degreasing tank containing the degreasing agent, and at the same time, the surface tension of the degreasing tank after long-term use does not increase by more than 2mN / m, improves and maintains the wettability and penetration effect of the degreasing tank, maintains the degreasing effect and increases the service life of the degreasing tank, and reduces the frequency of degreasing tank changes. At the same time, the emulsification and dispersibility of the degreasing tank are improved, the alkalinity of the degreasing agent is improved, the saponification ability of the degreasing tank to oil stains is strengthened, and the degreasing ability of the degreasing agent to the plate is comprehensively improved.

[0076] In one embodiment, the degreasing agent includes a compounding agent and a surfactant, wherein the compounding agent and the surfactant can be prepared in a mass ratio of 2: 1. That is, the mass of the added compounding agent is twice the mass of the surfactant.

[0077] In this embodiment, the reagents required for preparing 1000L tank liquid are 16kg compounding agent and 8Kg surfactant, and the free alkalinity of the degreasing tank liquid is controlled in the range of 16pt to 19pt, and can be 17pt and 18pt. When calculating the amount of degreasing agent added according to the free alkalinity of the degreasing tank liquid, 0.93kg of compounding agent and a corresponding proportion of surfactant (e.g., 0.465Kg of surfactant) are required for each increase of 1pt of free alkalinity.

[0078] In one embodiment, the surfactant may include one or two or more of fatty alcohol polyoxyethylene ether, isomeric tridecanol polyoxyethylene ether, alkyl sodium sulfonate and alkyl benzene sodium sulfonate. It is understandable that the surfactant of the present application may be selected from known and feasible components, and its specific components and proportions are not limited, which does not affect the understanding or reproduction of the degreasing agent and body-in-white pretreatment process of the present application by those skilled in the art.

[0079] It can be understood that, compared with general degreasing agents, the degreasing agent provided in the embodiment of the present application adjusts the ratio and dosage of hydroxide and carbonate, wherein the free alkali control parameter is increased to 16pt to 19pt, thereby improving the saponification and emulsification capacity of the degreasing bath. Specifically, especially for a production line designed with a process time of 1 minute pre-degreasing and / or 3 minutes main degreasing, the degreasing bath provided in the embodiment of the present application has a free alkali control range of 16pt to 19pt, which can ensure about 100% degreasing effect without causing excessive corrosion to the plate, and has a better degreasing effect.

[0080] It can be understood that compared with the general degreasing agent, the degreasing agent provided in the embodiment of the present application adjusts the ratio and dosage of hydroxide and carbonate, especially greatly increases the ratio of sodium carbonate, thereby improving the dispersibility of the degreasing tank liquid on the oil droplets in the tank liquid (for example, the degreasing agent provided in the embodiment of the present application can emulsify and disperse large oil droplets into small oil droplets, and control the particle size of the emulsified oil droplets within 400nm), and improves the wetting, penetration, emulsification and saponification capabilities of the degreasing tank liquid. In addition, for the working condition of long-term use of the degreasing tank liquid (that is, the oil content of the tank liquid is close to 3g / L), the surface tension of the degreasing tank liquid increases by no more than 2mN / m (for example, the surface tension of the degreasing tank liquid newly configured by the degreasing agent is about 26mN / m, and the surface tension of the degreasing tank liquid can be maintained at about 28mN / m after long-term use). Compared with the newly configured degreasing tank liquid, the surface tension of the degreasing tank liquid after use is not much increased, and the wetting effect of the degreasing tank liquid on the plate (especially the zinc-magnesium-aluminum coated steel plate) is basically not deteriorated. The surface tension of the improved degreasing agent tank liquid provided in the embodiment of the present application is minimally affected by the number of workpieces processed, thereby increasing the service life of the degreasing tank liquid and reducing the replacement frequency of the degreasing tank liquid.

[0081] It can be understood that the degreasing agent provided in the embodiment of the present application solves the problem that after long-term use, the degreasing effect of the traditional degreasing agent on the zinc-magnesium-aluminum coated steel plate decreases, the surface tension of the tank liquid increases, resulting in reduced wetting performance, thereby affecting the degreasing effect and the service life of the degreasing tank liquid. The degreasing agent provided in the embodiment of the present application particularly improves the etching ability of aluminum oxide and magnesium oxide on the surface of the zinc-magnesium-aluminum coated steel plate, comprehensively improves the degreasing ability of the zinc-magnesium-aluminum coated steel plate, and has no other negative effects on the degreasing effect of other body-in-white panels.

[0082] Further integration Figure 5 As shown, the body-in-white pre-treatment process provided in the embodiment of the present application may include the following steps:

[0083] Step S1: Plate screening process: Measure the surface energy of the plates and put the plates that meet the requirements into the subsequent steps.

[0084] Step S2: Flood water washing process: washing and preheating the body-in-white panels.

[0085] Step S3: Pre-degreasing process: spray the pre-degreasing tank liquid onto the surface of the plate by spraying.

[0086] Step S4: Main degreasing process: Use the main degreasing tank liquid containing a degreasing agent to degrease the plate, control the free alkalinity of the main degreasing tank liquid to be in the range of 16Pt to 19Pt, and control the oil content of the main degreasing tank liquid to be less than 3.0g / L.

[0087] Step S5: Industrial water washing process: The plate is rinsed to remove the main degreasing tank liquid remaining on the surface of the plate.

[0088] Step S6: Surface conditioning process: immersing the plate in a surface conditioning bath, wherein the surface conditioning bath comprises zinc phosphate.

[0089] Step S7: Phosphating process: immersing the plate after the surface adjustment process in a phosphating bath for phosphating treatment.

[0090] Furthermore, the body-in-white pretreatment process provided in the embodiment of the present application maintains the degreasing activity of the degreasing agent for a long time and ensures the degreasing effect of the degreasing agent by determining the process requirements such as the degreasing tank liquid addition specification, the construction parameter setting and the tank change cycle.

[0091] It should be explained that the "plate material" described in the embodiment of the present application refers to the material to be processed in the BIW pre-treatment process of the embodiment of the present application, which can be a BIW with a certain shape that is already in an assembly posture, or various raw material plates used to assemble the BIW, or other raw materials that need to be processed using the BIW pre-treatment process. In the subsequent embodiments, the "plate material" is taken as an example of a BIW with a certain shape that is already in an assembly posture, and those skilled in the art should be able to fully understand this.

[0092] In one embodiment, the plate can be selected from non-metal-coated steel plate, hot-dip galvanized steel plate, electro-galvanized steel plate, aluminum alloy plate, aluminum-silicon coated plate, and zinc-magnesium-aluminum coated steel plate. Among them, the aluminum element and / or magnesium element in the zinc-magnesium-aluminum coated steel plate is easily enriched on the coating surface, and the chemical properties of the aluminum element and / or magnesium element are very active and easily oxidized, and the eutectic structure of the aluminum element and / or magnesium element is easy to form micron-level grooves on the surface of the plate, resulting in the surface energy of the zinc-magnesium-aluminum coated steel plate having a greater impact on the later stage of the body-in-white pre-treatment process. In order to further improve the overall yield of the body-in-white pre-treatment process, the plate can be screened at the incoming material stage of the zinc-magnesium-aluminum coated steel plate.

[0093] Further integration Figure 6 As shown, in one embodiment, when the plate is a zinc-magnesium-aluminum coated steel plate, a plate screening process step S1 is further included before the aforementioned steps, which includes the following steps:

[0094] Step S11: taking a plurality of plates and cleaning the surfaces of the plates.

[0095] In this embodiment, the surface of the plate may be cleaned by wiping it with a non-woven fabric.

[0096] Step S12: using a dyne pen to perform multiple measurements on the surfaces of the multiple cleaned plates to obtain surface energy values ​​of the multiple plates.

[0097] It needs to be explained that the dyne pen, also known as a surface tension test pen or a corona treatment pen, is a tool used to test the surface tension of a material.

[0098] In this embodiment, the dyne pen can be placed perpendicular to the surface of the plate and appropriate pressure can be applied to draw a line on the surface of the plate. Within 2 to 3 seconds after drawing the line, observe whether the handwriting shrinks and condenses into water droplets. If the handwriting is very smooth and does not shrink, it means that the dyne value of the surface of the object being measured is higher than or equal to the value of the dyne pen; if the handwriting shrinks and forms water droplets, it means that the dyne value of the surface of the object being measured is lower than the value of the dyne pen. The same plate can be measured by using multiple dyne pens of different specifications, or using a dyne pen with a known value (for example, a dyne pen with a corresponding surface energy value of 26mN / m) for measurement, and the test results are statistically analyzed.

[0099] Step S13: Take the average value of the surface energy values ​​of the plate. If the average value is greater than or equal to 26 mN / m, the corresponding plate is judged to be qualified, otherwise it is judged to be unqualified (that is, the average value is less than 26 mN / m).

[0100] In this embodiment, three samples can be selected from each batch of plates, each sample is tested three times, and the average of the three test results is taken as the surface energy of the sample. If the dyne values ​​of the three samples are greater than or equal to 26mN / m, the plate is judged to be qualified, otherwise it is judged to be unqualified.

[0101] It is understandable that due to the different enrichment levels of aluminum and magnesium elements on the surface of zinc-magnesium-aluminum coated steel plates, their surface energies are usually different, and the surface energy range is usually 22mN / m to 37mN / m. Among them, for plates with a surface energy less than 26mN / m, it is difficult for the degreasing bath to spread spontaneously on the surface of the plate, and a longer reaction time is required; while for plates with a surface energy greater than or equal to 26mN / m, the degreasing bath can wet the surface of the plate quickly, penetrate into the oil layer, react more fully, and the degreasing effect on the plate is usually better.

[0102] Step S14: putting the qualified plates into use.

[0103] It can be understood that the body-in-white pretreatment process provided in the embodiment of the present application adds a plate surface energy detection and screening process at the plate incoming stage based on the obvious correlation found between the plate surface energy and the enrichment degree of aluminum and magnesium elements on the plate surface. The plates are selected in advance based on the surface energy, and the microscopic defects that cannot be found visually are intuitively reflected in the form of quantitative values. The enrichment degree of aluminum and magnesium elements on the plate surface in the zinc-magnesium-aluminum coated steel plate is more intuitively evaluated, and plates that do not meet the requirements (low surface energy) or may have problems in the subsequent processing process are selected. Thereby preventing the occurrence of problems after painting in advance, improving the product qualification rate, ensuring stable product performance, improving production efficiency, saving raw materials and reducing production costs.

[0104] Further integration Figure 7As shown, in one embodiment, the flood water washing process corresponding to step S2 may include the following steps:

[0105] Step S21: spray the plate at the process entrance, and control the spray flow rate at the entrance to be 120m 3 / h.

[0106] Step S22: Use multiple spray rings to spray the plate, and control the spray pressure range to be 0.15Mpa to 0.25Mpa.

[0107] Step S23: spray the plate at the process exit, and control the spray flow rate at the exit to be 120m 3 / h.

[0108] In one embodiment, the water washing temperature of the flood water washing process is controlled to range from room temperature and higher to no higher than 50°C.

[0109] In this embodiment, the water washing temperature of the flood water washing process can specifically be 35°C, 40°C, 43°C, 46°C and 49°C.

[0110] In one embodiment, at least 8 spray rings can be set at the workstations corresponding to the flood water washing process, which are used to perform surround spray washing on the bottom, top and sides of the body in white respectively. The spray pressure range is controlled to be 0.15Mpa to 0.25Mpa, and the replacement cycle of the tank liquid at the workstations corresponding to the flood water washing process can be once every 3 to 7 days.

[0111] In this embodiment, the spray pressure of the flood water washing process can specifically be 0.16Mpa, 0.17Mpa, 0.18Mpa, 0.19Mpa, 0.20Mpa, 0.21Mpa, 0.22Mpa, 0.23Mpa and 0.24Mpa.

[0112] It can be understood that a large flow of water is used to flush the plates at the inlet and outlet ends of the flood water washing process, especially from the front and rear windows of the body-in-white to flush out iron filings, welding slag, dust and other debris inside the body-in-white, and to preheat the plates and activate oil stains to facilitate degreasing in subsequent processes.

[0113] It can be understood that spraying has a mechanical flushing effect. The pressure range of the spraying is controlled to be 0.15Mpa to 0.25Mpa, so that the spraying process has a better cleaning effect and can effectively clean the outer surface of the plate and the depressions, gaps, etc. of the plate.

[0114] In one embodiment, in the pre-degreasing process corresponding to step S3, the pre-degreasing tank liquid is sprayed onto the surface of the plate by spraying. During the spraying process, the pre-degreasing tank liquid has a physical impact on the plate, and the pre-degreasing tank liquid also reacts chemically with the surface of the plate. Through the combined effect of chemical reaction and physical impact, the surface of the plate is cleaned.

[0115] In one embodiment, the free alkalinity range of the pre-degreasing tank liquid is controlled to be 16Pt to 19Pt, the total alkalinity range of the pre-degreasing tank liquid is controlled to be 26Pt to 32Pt; the temperature range of the pre-degreasing tank liquid is controlled to be 45°C to 55°C, and the spraying pressure range is controlled to be 0.15Mpa to 0.2Mpa.

[0116] In this embodiment, the free alkalinity of the pre-degreasing bath solution can be 17Pt and 18Pt. The total alkalinity of the pre-degreasing bath solution can be 27Pt, 28Pt, 29Pt, 30Pt and 31Pt.

[0117] In this embodiment, the temperature of the pre-degreasing bath liquid can be 46° C., 47° C., 48° C., 49° C., 50° C., 51° C., 52° C., 53° C. and 54° C. The spraying pressure of the pre-degreasing process can be 0.16 MPa, 0.17 MPa, 0.18 MPa and 0.19 MPa.

[0118] It can be understood that, especially for a production line designed with a pre-degreasing process time of 1 minute, the pre-degreasing tank liquid with a free alkalinity control range of 16pt to 19pt provided in the embodiment of the present application can ensure about 100% oil removal effect without causing excessive corrosion to the plate, and has a better degreasing effect.

[0119] It can be understood that by monitoring the total alkalinity of the pre-degreasing tank liquid, the aging level of the pre-degreasing tank liquid can be monitored; the total alkalinity of the pre-degreasing tank liquid is controlled in the range of 26Pt to 32Pt, so that the aging level of the pre-degreasing tank liquid is at a better stage, thereby making the pre-degreasing tank liquid have a better effect.

[0120] It can be understood that the temperature range of 45°C to 55°C can correspond to the optimal temperature activity range of the surfactant. At the same time, the temperature range of 45°C to 55°C can also meet the demand for faster saponification reaction. Spraying has the effect of mechanical flushing. The pressure range of the spray is controlled to be 0.15Mpa to 0.2Mpa to wash away part of the grease attached to the plate, and enable the pre-degreasing tank liquid to enter the depressions and gaps of the plate to improve the degreasing effect. Moreover, cleaning by spraying and controlling the spray pressure range to be 0.15Mpa to 0.2Mpa can also make the pre-degreasing tank liquid more evenly distributed, avoid incomplete degreasing, and improve degreasing efficiency.

[0121] In one embodiment, the pre-degreasing tank liquid is supplemented by the main degreasing tank liquid through overflow.

[0122] It can be understood that the liquid storage tank (not shown) corresponding to the pre-degreasing process and the liquid storage tank (not shown) corresponding to the main degreasing process can be set to be connected. At the same time, the degreasing agent provided in the embodiment of the present application optimizes its components, and the surface tension of the main degreasing tank liquid after use does not change much, and the free alkalinity of the main degreasing tank liquid is controlled, which can meet the parameter requirements when it is further used as a supplement to the pre-degreasing tank liquid and pre-degreasing treatment. Based on this, in the circulation of the main degreasing tank liquid, part of the used main degreasing tank liquid can be circulated to the workstation corresponding to the pre-degreasing process, and the pre-degreasing tank liquid can be supplemented, which not only ensures the cleaning effect of the pre-degreasing tank liquid, but also improves the process cycle efficiency, taking into account production efficiency and product yield.

[0123] Further integration Figure 8 As shown, in one embodiment, the main degreasing process corresponding to step S4 may include the following steps:

[0124] S41: Use the main degreasing tank liquid to spray the plate around by spraying.

[0125] S42: Immerse the sprayed plate in the main degreasing tank liquid.

[0126] S43: Use the main degreasing tank liquid to spray the soaked plate around by spraying.

[0127] In this embodiment, the free alkalinity of the main degreasing tank liquid is controlled to be in the range of 16Pt to 19Pt, and the oil content of the main degreasing tank liquid is controlled to be less than 3.0g / L.

[0128] Furthermore, the free alkalinity of the main degreasing tank liquid can be specifically 17Pt or 18Pt. The oil content of the main degreasing tank liquid can also be less than 2.98g / L, or less than 2.99g / L, or less than 3.01g / L, or less than 3.02g / L to cope with performance fluctuations of materials or test instruments.

[0129] It can be understood that, especially for a production line designed with a main degreasing process time of 3 minutes, the main degreasing tank liquid with a free alkalinity control range of 16pt to 19pt provided in the embodiment of the present application can ensure about 100% oil removal effect without causing excessive corrosion to the plate, and has a better degreasing effect.

[0130] It is understandable that if the oil content of the main degreasing tank liquid is too high, the emulsification effect of the main degreasing tank liquid will be poor, which will have a negative impact on the degreasing effect of the main degreasing tank liquid. Therefore, controlling the oil content of the main degreasing tank liquid to less than 3.0g / L can make the main degreasing tank liquid have a better degreasing effect.

[0131] In one embodiment, the total alkalinity of the main degreasing tank liquid is controlled to be in the range of 26Pt to 32Pt, and the ratio of the total alkalinity of the main degreasing tank liquid to the free alkalinity of the main degreasing tank liquid is controlled to be less than or equal to 2. That is, when the ratio of the total alkalinity of the main degreasing tank liquid to the free alkalinity of the main degreasing tank liquid is greater than 2, the main degreasing tank liquid needs to be replaced.

[0132] In this embodiment, the total alkalinity of the main degreasing tank liquid can specifically be 27Pt, 28Pt, 29Pt, 30Pt and 31Pt.

[0133] It can be understood that by monitoring the total alkalinity of the main degreasing tank liquid, the aging level of the main degreasing tank liquid can be monitored; the total alkalinity of the main degreasing tank liquid is controlled in the range of 26Pt to 32Pt, so that the aging level of the main degreasing tank liquid is at a better stage, thereby making the main degreasing tank liquid have a better effect.

[0134] It is understandable that the ratio of the total alkalinity of the main degreasing tank liquid to the free alkalinity of the main degreasing tank liquid is controlled to be less than or equal to 2, so that the main degreasing tank liquid can effectively neutralize acidic substances (such as carbon dioxide in the air), maintain the alkaline environment of the main degreasing tank liquid, and ensure the normal progress of the degreasing reaction. On the other hand, when the ratio of the total alkalinity of the main degreasing tank liquid to the free alkalinity of the main degreasing tank liquid is too high (for example, greater than 2), the acidic substances cannot be fully neutralized, the pH value of the main degreasing tank liquid decreases, the performance of the main degreasing tank liquid (for example, the emulsification ability is reduced, the saponification reaction is inhibited, etc.) changes, and / or the aging of the main degreasing tank liquid is accelerated.

[0135] In one embodiment, the temperature of the main degreasing tank liquid is controlled to be in the range of 45° C. to 55° C., and the pressure of the spraying is controlled to be in the range of 0.15 MPa to 0.2 MPa.

[0136] In this embodiment, the temperature of the main degreasing tank liquid can be 46° C., 47° C., 48° C., 49° C., 50° C., 51° C., 52° C., 53° C. and 54° C. The spraying pressure of the main degreasing process can be 0.16 MPa, 0.17 MPa, 0.18 MPa and 0.19 MPa.

[0137] It can be understood that the temperature range of 45°C to 55°C can correspond to the optimal temperature activity range of the surfactant. At the same time, the temperature range of 45°C to 55°C can also meet the demand for faster saponification reaction.

[0138] It can be understood that spraying has a mechanical flushing effect, and the spraying pressure range is controlled to be 0.15Mpa to 0.2Mpa to flush away some of the grease attached to the plate, and to allow the main degreasing tank liquid to enter the depressions and gaps of the plate to improve the degreasing effect. Moreover, cleaning by spraying and controlling the spraying pressure range to be 0.15Mpa to 0.2Mpa can also make the main degreasing tank liquid more evenly distributed, avoid incomplete degreasing, and improve degreasing efficiency.

[0139] In this embodiment, the circulation frequency of the main degreasing tank liquid can be controlled to be 3 to 4 times per hour.

[0140] In this embodiment, step S41 corresponds to the spraying performed before immersing the plate in the main degreasing tank in the main degreasing process. The spraying process can be 2 rounds of surrounding spraying on the plate or multiple (for example, 2) spray rings are used to surround the plate for multiple times. Step S42 corresponds to immersing the plate in the main degreasing tank. The immersion time can be 3 minutes, and the immersion time can be appropriately shortened or increased according to the actual process requirements to achieve a better degreasing effect. Step S43 corresponds to the spraying performed after the plate immersed in the main degreasing tank is taken out in the main degreasing process. The spraying process can be 2 rounds of surrounding spraying on the plate or multiple (for example, 2) spray rings are used to surround the plate for multiple times.

[0141] It can be understood that in the main degreasing process, the plate is immersed in the main degreasing tank liquid, so that the main degreasing tank liquid can further infiltrate or penetrate into the inner panels, inner cavities and plate seams of the white body and other areas that are not easy to clean during the spraying process, and further degrease the inner panels, inner cavities and seams of the white body, thereby greatly improving the degreasing efficiency.

[0142] Further integration Fig. 9 As shown, in one embodiment, the industrial water washing process corresponding to step S5 may include a first industrial water washing process and a second industrial water washing process, which respectively correspond to the following steps:

[0143] S51: using the first washing bath liquid to rinse the plate by spraying, controlling the pH value of the first washing bath liquid to be in the range of 7 to 11.5, and controlling the spraying pressure to be in the range of 0.15 MPa to 0.25 MPa.

[0144] In this embodiment, the degreasing tank liquid (mainly the main degreasing tank liquid) remaining on the surface of the plate is rinsed by spraying to remove the degreasing tank liquid. The spraying treatment time can be 1 minute, and the replacement cycle of the first washing tank liquid can be replaced once every 3 to 7 days.

[0145] It is understandable that the first washing tank liquid can be clean water or water containing impurities after washing, or other cleaning liquids with added neutralizing agents, which will not be described in detail here.

[0146] S52: using the second washing tank liquid to clean the plate by spraying and soaking, controlling the pH value of the second washing tank liquid to be in the range of 7 to 11.5, and controlling the spraying pressure range to be in the range of 0.15 MPa to 0.25 MPa.

[0147] In this embodiment, the plate is immersed in the second water washing tank liquid to rinse and remove the degreasing tank liquid remaining in the inner plate, inner cavity and gap of the body in white.

[0148] Specifically, the plate can be subjected to two-round spraying or multiple (for example, two) spraying rings to perform multiple-round spraying on the plate, and then the plate can be immersed in the second water washing tank, taken out immediately after immersion, and then subjected to two-round spraying again or multiple (for example, two) spraying rings to perform multiple-round spraying on the plate. Alternatively, after the above-mentioned cleaning is completed, two more high-pressure spraying rings can be added to perform high-pressure spraying cleaning on the plate, and high-pressure spraying refers to a relatively high-pressure cleaning method with a water pressure of about 20Mpa.

[0149] It is understandable that the second washing tank liquid can be circulated twice per hour, and the replacement cycle of the second washing tank liquid can be changed every 3 to 7 days. The second washing tank liquid can be clean water or water containing impurities after washing, or other cleaning liquids with added neutralizers, which will not be described in detail here.

[0150] It can be understood that spraying has a mechanical flushing effect, and the spraying pressure range is controlled to be 0.15Mpa to 0.25Mpa, so that the spraying process has a better cleaning effect, and can effectively clean the outer surface of the plate and the depressions and gaps of the plate. In one embodiment, in the surface adjustment process corresponding to step S6, the plate is immersed in the surface adjustment tank liquid, and the zinc phosphate particles, which are the effective ingredients in the surface adjustment tank liquid, can be adsorbed on the surface of the plate, providing crystal nuclei for the phosphating film formation in the phosphating process, accelerating the phosphating reaction speed, and refining the phosphating crystal grain size.

[0151] In this embodiment, the surface conditioning process may specifically include immersing the plate in the surface conditioning bath for about 1 minute, and then performing two rounds of surrounding spraying on the plate after taking it out, or using multiple (e.g., 2) spray rings to perform multiple surrounding spraying on the plate. The surface conditioning bath needs to be prepared with RO1 water, and those skilled in the art will understand that RO1 water refers to water treated by reverse osmosis (RO) technology, which will not be described in detail here.

[0152] In one embodiment, in the phosphating process corresponding to step S7, the plate treated in the surface adjustment process is immersed in a phosphating bath for phosphating, the temperature range of the phosphating bath is controlled to be 33°C to 40°C, the total acidity range of the phosphating bath is controlled to be 20Pt to 22Pt, the free acidity range of the phosphating bath is controlled to be 0.5Pt to 1Pt, and the concentration of the accelerator is controlled to be 3.0Pt to 5.0Pt.

[0153] In one embodiment, the phosphating process may specifically include immersing the plate in the phosphating bath for about 3 minutes, and then performing 2 rounds of surrounding spraying on the plate after taking it out, or using multiple (e.g., 2) spray rings to perform multiple surrounding spraying on the plate. The phosphating bath needs to be prepared with RO1 water, and the phosphating bath can be circulated 4 to 5 times per hour.

[0154] It can be understood that when the plate is immersed in the phosphating tank, the reaction generates a zinc phosphate conversion film, which can be used as the bottom layer of the paint composite coating in the subsequent coating process to improve the corrosion resistance and bonding strength of the paint composite coating.

[0155] It can be understood that the phosphating bath used in the present application may contain components such as zinc dihydrogen phosphate, manganese dihydrogen phosphate and some metal nitrates, and known and feasible components can be selected and will not be described in detail here.

[0156] Based on Figures 4 to 9 The implementation method described in the aforementioned embodiment simulates the degreasing of the white body through the line (embodiment), and the degreasing agent is replaced with a degreasing agent not provided by the present application to simultaneously simulate the degreasing of the white body through the line (comparative example). The experimental simulation verification obtains the simulation results shown in Tables 1 to 5 below, wherein "NG" means failure and "OK" means pass.

[0157] Table 1 Round 1: Simulation of 1500 white body degreasing lines

[0158] FAL(pt) Surface tension (mN / m) Degreasing effect Comparative Example 11.0 26.8 OK Example 16.3 26.3 OK

[0159] Table 2 Second round: simulation of 3,000 white body degreasing lines

[0160] FAL(pt) Surface tension (mN / m) Degreasing effect Comparative Example 10.8 30.3 NG Example 16.9 26.7 OK

[0161] Table 3 Round 3: Simulation of 4500 white body degreasing lines

[0162] FAL(pt) Surface tension (mN / m) Degreasing effect Comparative Example 11.0 32.3 NG Example 16.3 27.2 OK

[0163] Table 4 Round 4: Simulation of 6,000 white body degreasing lines

[0164] FAL(pt) Surface tension (mN / m) Degreasing effect Comparative Example 11.0 35.7 NG Example 16.9 27.9 OK

[0165] Table 5 Round 5: Simulation of 7500 white cars passing the degreasing line

[0166] FAL(pt) Surface tension (mN / m) Degreasing effect Comparative Example 11.0 36.6 NG Example 16.6 27.5 OK

[0167] Combining Tables 1 to 5, it can be seen that the comparative example showed poor degreasing when simulating the degreasing of 3,000 white cars passing the line, and the surface tension of the degreasing tank liquid (main degreasing tank liquid) increased significantly when simulating 4,500, 6,000 and 7,500 white cars, and the corresponding degreasing effect was poor. However, when the embodiments of the present application simulated the degreasing of 3,000, 4,500, 6,000 and 7,500 white cars passing the line, the surface tension of the degreasing tank liquid (main degreasing tank liquid) increased slightly, and the corresponding degreasing effect was better.

[0168] like Fig.10 and Fig.11 As shown in the figure, after simulating 7500 vehicles passing the line, Fig.10 The degreasing bath liquid corresponding to the comparative example shown is relatively turbid, but Fig.11 The degreasing tank liquid corresponding to the embodiment shown is obviously clearer, which proves that the degreasing agent provided in the embodiment of the present application has a greatly improved liquid emulsification and dispersion ability.

[0169] Further integration Fig.12 As shown, the plate treated by the white body pretreatment process provided in the embodiment of the present application has the characteristics of uniform phosphating film appearance and no flower problem, indicating that the white body pretreatment process provided in the embodiment of the present application has a better degreasing effect, and thus the subsequent phosphating treatment effect is excellent.

[0170] Further integration Fig.13 As shown, the plate treated by the body-in-white pretreatment process provided in the embodiment of the present application has a phosphating crystal size of about 3μm to 5μm and a crystal coverage of about 100%, indicating that the body-in-white pretreatment process provided in the embodiment of the present application has a better degreasing effect, and thus the subsequent phosphating treatment effect is excellent.

[0171] Further integration Fig.14 and Fig.15 As shown, Fig.14 Schematic diagram of the body appearance after the front degreasing treatment is improved, that is, the body in white after the corresponding process treatment in the comparative example can be clearly observed to have flowery surface and obvious defects; Fig.15 This is a schematic diagram of the appearance of a vehicle body after being treated with the degreasing agent and the body-in-white pre-treatment process provided by the embodiments of the present application. That is, after the body-in-white is treated with the corresponding process of the embodiments, it can be clearly observed that the surface effect of the body-in-white is better.

[0172] It can be understood that the degreasing agent and white body pretreatment process provided in the embodiments of the present application have a corresponding degreasing tank liquid surface tension of about 26mN / m. After long-term use, the corresponding degreasing tank liquid surface tension can be maintained at about 28mN / m. The wettability and permeability of the degreasing tank liquid remain in good condition, and the degreasing ability of zinc-magnesium-aluminum coated steel plates is basically not reduced, and it does not produce other negative effects on other types of plates.

[0173] It can be understood that the degreasing agent and body-in-white pretreatment process provided in the embodiments of the present application, by optimizing the content of various substances of the degreasing agent in the degreasing tank, improves the surface tension and emulsification and dispersion properties of the tank during the production process, thereby enhancing the degreasing effect of the degreasing tank on zinc-magnesium-aluminum coated steel plates, reducing the probability of "flowering" streaks after phosphating of the plates, greatly improving the one-time pass rate of the body-in-white pretreatment process, and achieving energy conservation, emission reduction and scientific management and control.

[0174] In the above, the specific embodiments of the present application are described with reference to the accompanying drawings. However, those skilled in the art will appreciate that various changes and substitutions may be made to the specific embodiments of the present application without departing from the scope of the present application. These changes and substitutions are all within the scope defined by the present application.

Claims

1. A degreasing agent, characterized in that The invention comprises a compounding agent, which comprises, by weight percentage, 1% to 5% of hydroxide, 50% to 60% of carbonate, 20% to 30% of silicate, 5% to 10% of sodium pyrophosphate and 13% to 20% of chelating agent.

2. The degreasing agent according to claim 1, characterized in that The hydroxide includes sodium hydroxide and / or potassium hydroxide, the carbonate includes sodium carbonate and / or potassium carbonate, the silicate includes sodium metasilicate, and the chelating agent includes sodium gluconate and / or sodium tripolyphosphate.

3. A body-in-white pre-treatment process, characterized in that: The steps include: Flood washing process: washing and preheating the body-in-white panels; Pre-degreasing process: spraying the pre-degreasing tank liquid onto the surface of the plate by spraying; Main degreasing process: using a main degreasing tank liquid containing the degreasing agent according to any one of claims 1 to 2 to degrease the plate, controlling the free alkalinity of the main degreasing tank liquid to be in the range of 16Pt to 19Pt, and controlling the oil content of the main degreasing tank liquid to be less than 3.0g / L; Industrial water washing process: washing the plate to remove the main degreasing tank liquid remaining on the surface of the plate.

4. The body-in-white pretreatment process according to claim 3, characterized in that: The total alkalinity of the main degreasing tank liquid is controlled to be in the range of 26Pt to 32Pt, and the ratio of the total alkalinity of the main degreasing tank liquid to the free alkalinity of the main degreasing tank liquid is controlled to be less than or equal to 2.

5. The body-in-white pretreatment process according to claim 3, characterized in that: The main degreasing process comprises: Using the main degreasing tank liquid, spraying the plate around by spraying; Immersing the sprayed plate in the main degreasing tank liquid; Using the main degreasing tank liquid, spraying the immersed plate around by spraying; The temperature of the main degreasing tank liquid is controlled in the range of 45°C to 55°C, and the pressure of the spraying is controlled in the range of 0.15Mpa to 0.2Mpa.

6. The body-in-white pretreatment process according to claim 3, characterized in that: When the plate is a zinc-magnesium-aluminum coated steel plate, a plate screening process is further included before the multiple steps as claimed in claim 3, and the plate screening process includes the following steps: Taking a plurality of the plates, and cleaning the surfaces of the plates; Using a dyne pen to perform multiple measurements on the surfaces of the plurality of cleaned plates to obtain surface energy values ​​of the plurality of plates; Taking the average value of the surface energy values ​​of the plurality of plates, if the average value is greater than or equal to 26 mN / m, the corresponding plate is determined to be qualified, and if the average value is less than 26 mN / m, the corresponding plate is determined to be unqualified; The qualified plates are put into the subsequent steps.

7. The body-in-white pretreatment process according to claim 3, characterized in that: The pre-degreasing tank liquid is supplemented by the main degreasing tank liquid through overflow; The free alkalinity of the pre-degreasing tank solution is controlled to be in the range of 16Pt to 19Pt, and the total alkalinity of the pre-degreasing tank solution is controlled to be in the range of 26Pt to 32Pt; The temperature range of the pre-degreasing tank liquid is controlled to be 45° C. to 55° C., and the pressure range of the spraying is controlled to be 0.15 MPa to 0.2 MPa.

8. The body-in-white pretreatment process according to claim 3, characterized in that: The industrial water washing process comprises: The first industrial water washing process: using the first water washing tank liquid to rinse the plate by spraying, controlling the pH value of the first water washing tank liquid to be in the range of 7 to 11.5, and controlling the spraying pressure range to be in the range of 0.15Mpa to 0.25Mpa; Second industrial water washing process: Use the second water washing tank liquid to clean the plate by immersion and spraying, control the pH value of the second water washing tank liquid to be in the range of 7 to 11.5, and control the spraying pressure range to be 0.15Mpa to 0.25Mpa.

9. The body-in-white pretreatment process according to claim 3, characterized in that: The body-in-white pre-treatment process also includes: Surface conditioning step: immersing the plate in a surface conditioning bath, wherein the surface conditioning bath comprises zinc phosphate; Phosphating process: immerse the plate treated by the surface adjustment process in a phosphating bath for phosphating treatment, control the temperature range of the phosphating bath to be 33°C to 40°C, control the total acidity range of the phosphating bath to be 20Pt to 22Pt, and control the free acidity range of the phosphating bath to be 0.5Pt to 1Pt.

10. The body-in-white pretreatment process according to claim 3, characterized in that: The flood water washing process comprises the following steps: The plate is sprayed and rinsed at the entrance corresponding to the flood water washing process, and the spray flow rate at the entrance is controlled to be 120m 3 / h; Use multiple spray rings to spray the plate, and control the spray pressure range to be 0.15Mpa to 0.25Mpa; The plate is sprayed and rinsed at the outlet corresponding to the flood water washing process, and the spray flow rate at the outlet is controlled to be 120m 3 / h; Among them, the water washing temperature range of the flood water washing process is controlled to be normal temperature and higher to not higher than 50°C.

Images