Degreasing agent for base plate of cold-rolled hot-dipped aluminum-zinc steel plate and degreasing method

Abstract

The invention discloses a degreasing agent for a base plate of a cold-rolled hot-dip aluminum-zinc steel plate and a degreasing method, and mainly solves the technical problems that an existing degreasing agent for the base plate of the cold-rolled hot-dip aluminum-zinc steel plate is low in degreasing efficiency, and oxides on the surface of the steel plate cannot be completely removed. According to the technical scheme, the degreasing agent for the base plate of the cold-rolled hot-dipped aluminum-zinc steel plate comprises the following components in percentage by weight: 10%-25% of sodium hydroxide, 5%-15% of potassium hydroxide, 3%-6% of a surfactant OP-10, 4%-8% of sodium dodecyl benzene sulfonate, 1%-2% of fatty alcohol polyoxyethylene ether sodium sulfate, 2%-10% of sodium oxalate and the balance of water. 2%-5% of sodium gluconate, 1%-5% of potassium chloride, 2%-4% of organic silicon defoaming agent and the balance of deionized water. The degreasing agent is suitable for removing residual oil and iron oxide on the surface of a base plate of a cold-rolled hot-dipped aluminum-zinc steel plate, the degreasing capacity and the iron removal capacity are high, and the using effect is good.

Description

Technical Field

[0001] This invention relates to a steel plate surface cleaning agent, and more particularly to a degreasing agent and degreasing method for a substrate of cold-rolled hot-dip aluminized zinc steel plate, belonging to the field of steel plate surface treatment technology. Background Technology

[0002] Hot-dip aluminized zinc steel sheets are increasingly widely used in construction and home appliances due to their significantly higher corrosion resistance compared to hot-dip galvanized steel sheets. The production process for fingerprint-resistant hot-dip aluminized zinc steel sheets is as follows: uncoiling → welding → cleaning → annealing → hot-dip aluminized zinc coating → finishing → passivation (including fingerprint resistance) → coiling. Cleaning the steel sheet removes residual oil such as anti-rust oil and rolling oil, as well as impurities such as iron oxides, ensuring a smooth metallic surface for the hot-dip galvanizing process. This ensures that an alloy layer can form between the hot-dip galvanized coating and the steel sheet, reducing the likelihood of zinc layer peeling during subsequent use.

[0003] Currently, the cleaning process in hot-dip galvanizing production lines uses strong alkaline degreasing agents, which can remove various residual oils but are largely unable to remove oxides. Theoretically, there should be an acid pickling stage after degreasing to remove oxides from the steel plate surface. However, due to cost control requirements, and because the annealing stage after degreasing will reduce some oxides, domestic hot-dip galvanizing production lines do not actually include acid pickling, resulting in the problem of incomplete removal of oxides from the steel plate surface.

[0004] The oxides on the surface of steel substrates used for hot-dip galvanizing are quite complex, including Fe2O3 formed by natural oxidation during steel storage, FeO and Fe3O4 formed at high rolling temperatures, and carbonyl iron oxides formed by the reaction of iron on the steel surface with the rolling emulsion during rolling. An annealing process is performed after the cleaning process and before the hot-dip galvanizing process. The annealing process uses a reducing atmosphere, employing coal gas or natural gas as a protective gas. In this process, some oxides can be reduced to iron, but thicker oxides and carbonyl iron oxides cannot be removed by annealing. During the hot-dip galvanizing process, the unremovable oxides form zinc flower nuclei upon cooling, resulting in uneven zinc flowers on the appearance of the aluminized zinc sheet. The oxide-containing surface cannot bond with zinc to form a stable alloy layer, macroscopically leading to uneven thickness of the zinc-iron alloy layer in the coating. This easily results in localized zinc layer peeling defects during user operation. For high-end users, uneven zinc flowers and zinc peeling during stamping are both unacceptable.

[0005] There are many patents regarding the cleaning of steel substrates for hot-dip galvanizing. Organic degreasers are generally used for smaller workpieces, but due to the environmental impact of organic matter, they are generally not used in large-scale production. Acidic degreasers, mainly phosphoric acid and phosphate-based, are mostly used for cleaning stainless steel. However, for ordinary carbon steel materials such as hot-dip galvanized substrates, the acidity is too strong, making them unsuitable in terms of cost and performance. Furthermore, phosphates cause significant environmental pollution. The vast majority of degreasers in use are alkaline media.

[0006] Chinese patent application CN106544684A discloses a strip steel surface cleaning agent and its preparation and use method. It also discloses a degreasing agent for hard-rolled coils, comprising 20-25% sodium hydroxide, 5-10% sodium carbonate, 3-5% sodium gluconate, 3.5-15% anionic surfactant (sodium alkyl sulfonate), 0.5-10% nonionic surfactant (polyoxyethylene ether), 5-10% chelating agent (EDTA), and 20-63% water. The chelating agent is ethylenediaminetetraacetic acid tetrasodium tetrahydrate. However, its oxide removal efficiency is low.

[0007] Chinese patent application CN115595592A discloses a degreasing agent and degreasing method for continuous strip steel. The degreasing agent is composed of 10-50 g / L strong alkali (sodium hydroxide or potassium hydroxide), 5-40 g / L carbonate, 1-40 g / L phosphate, 1-25 g / L metal chelating agent (sodium gluconate and sodium citrate), 0.1-5.0 g / L emulsifier (sodium alkyl sulfonate), 0.05-2.00 g / L penetrant (fluoride or polyoxyethylene alcohol ether), 0.001-0.200 g / L defoamer (polyol ether), with the balance being pure water; however, its oxide removal efficiency is low.

[0008] Existing degreasing agents for cold-rolled hot-dip aluminized zinc steel sheets have low degreasing efficiency and poor degreasing quality. Summary of the Invention

[0009] The purpose of this invention is to provide a degreasing agent and degreasing method for the substrate of cold-rolled hot-dip aluminized zinc steel sheet, mainly to solve the technical problems of low degreasing efficiency and inability to completely remove oxides from the surface of the steel sheet by existing degreasing agents for the substrate of cold-rolled hot-dip aluminized zinc steel sheet.

[0010] The technical concept of this invention is to use strong alkali and surfactant as the basic degreasing system, sodium oxalate and sodium gluconate to remove oxides, and potassium chloride to enhance the removal effect. The selection of main salt and surfactant takes into account improving rinsing ability and avoiding secondary corrosion after cleaning.

[0011] The technical solution adopted in this invention is a degreasing agent for the substrate of cold-rolled hot-dip aluminized zinc steel sheet, the weight percentage of its components being: sodium hydroxide 10%-25%, potassium hydroxide 5%-15%, surfactant OP-10 3%-6%, sodium dodecylbenzene sulfonate 4%-8%, sodium fatty alcohol polyoxyethylene ether sulfate 1%-2%, sodium oxalate 2%-10%, sodium gluconate 2%-5%, potassium chloride 1%-5%, organosilicon defoamer 2%-4%, and the remainder being deionized water.

[0012] The present invention is able to remove residual oil and iron oxides from the surface of steel plates, and the reasons for limiting the components to the above-mentioned range are as follows:

[0013] During the cold rolling process of cold-rolled hot-dip galvanized steel sheets, an emulsion composed of various greases (such as natural greases and synthetic greases) is typically used to lubricate and cool the rolled copper sheet. Therefore, this grease lubricant remains on the surface of the steel strip after rolling. This oil layer must be removed through chemical degreasing and electrolytic degreasing to prevent it from carbonizing on the steel surface during annealing, causing carburization and forming carbonaceous stains, which would affect the performance and quality of the finished product. Furthermore, the steel sheet is often left to stand for a period of time before rolling, inevitably leading to surface oxidation. Simultaneously, during the rolling process, under rolling pressure and frictional heat, the rolling emulsion reacts with the steel surface to form carbonyl iron oxides. Thin layers of iron oxides can be reduced during annealing, but thicker oxides and carbonyl iron oxides cannot be reduced. The aluminum zinc plating temperature is around 600℃. At this temperature, iron oxides and carbonyl iron compounds react with the zinc liquid in the zinc pot, causing discontinuity in the zinc-iron alloy layer of the aluminum zinc plate, which affects the adhesion. At the same time, the reactants become solidification nuclei during solidification, resulting in macroscopic defects such as uneven zinc flowers.

[0014] This invention is based on a traditional degreasing system, with the addition of sodium oxalate-sodium gluconate to react with oxides on the surface of steel plates, and the addition of potassium chloride to further improve the deoxidizing ability, thus constructing a composite cleaning system that can simultaneously remove grease and oxides from the surface under alkaline conditions.

[0015] 1. Setting of sodium hydroxide and potassium hydroxide

[0016] The residual oil on the steel plate surface is a saponifiable grease (such as animal or vegetable oils), which reacts with alkali to produce soap and glycerin, which then separate from the surface. In this process, sodium hydroxide, as a strong alkali, reacts with the glycerides in the grease to produce the corresponding sodium salts of organic acids (i.e., soap) and glycerin. Simultaneously, at higher temperatures, sodium hydroxide can react with iron oxides to a certain extent: Fe₂O₃ + 2NaOH (conc.) = 2NaFeO₂ + H₂O. Theoretically, this has a certain rust-removing effect, but in practice, the reaction rate is slow and not very significant in continuous production.

[0017] Potassium hydroxide and sodium hydroxide have essentially the same effect, but potassium hydroxide costs about four times as much as sodium hydroxide. Due to the large radius of potassium ions, potassium hydroxide has better rinsing performance and is easier to rinse after degreasing. Experiments show that when the amount of potassium hydroxide is half that of sodium hydroxide, the overall rinsing performance is not much different from that of using potassium hydroxide directly. Therefore, the ratio of sodium hydroxide to potassium hydroxide is considered to be no more than 2:1, in order to achieve better rinsing ability while controlling costs.

[0018] The concentration of alkali solution used in the general degreasing process is between 1% and 2%. This alkali solution is prepared by diluting the degreasing liquid stock solution, with a dilution ratio of about 10 to 20 times.

[0019] The degreasing agent stock solution of this invention contains an alkaline solution with a combined concentration of sodium hydroxide and potassium hydroxide of 15%-40%; the sodium hydroxide content is 10%-25%, and the potassium hydroxide content is 5%-15%.

[0020] 2. Setting of sodium gluconate, sodium oxalate, and potassium chloride

[0021] Sodium gluconate can undergo a coordination reaction with iron to form the sodium gluconate iron complex [NaFe2O3(C6H2O)]. 11 O7)(C 12 H 22 O 11 )5] x (x≈200), thus achieving the cleaning of oxides on the steel plate surface, and having the advantages of easy rinsing of reactants and high surface cleanliness of the steel plate. Therefore, sodium gluconate has certain applications in some types of degreasing agents. However, the reaction rate is relatively slow and insufficient to fully remove iron oxides in continuous production. Sodium oxalate reacts with iron at a faster rate, forming [Fe(C2O4)2(H2O)4] complex ions with divalent iron or [Fe(C2O4)3] complex ions with trivalent iron, thereby achieving rapid oxide removal. However, sodium oxalate is not easy to rinse, and residual oxalate on the steel plate surface can easily cause rapid corrosion of the steel plate. Considering the advantages and disadvantages of the two reagents, a combined use of sodium gluconate and sodium oxalate is adopted. Oxides that are easy to clean are cleaned with sodium gluconate, and oxides that are difficult to clean are removed with sodium oxalate, ensuring cleaning ability and preventing corrosion.

[0022] To further accelerate the cleaning process, potassium chloride is added. The chloride ions in potassium chloride have a small radius, which allows them to quickly penetrate into the oxide layer and form various complexes with iron, thus accelerating the rapid peeling of the oxide layer. At the same time, potassium chloride can increase the conductivity of the solution, thereby speeding up the dissolution of the oxide layer.

[0023] Sodium gluconate, sodium oxalate, and potassium chloride are the main compounds in the degreasing agent of this invention for removing iron oxides.

[0024] The degreasing agent of this invention contains 2%-10% sodium oxalate, and its dosage can be adjusted according to the amount of oxides on the steel plate surface and the difficulty of removal.

[0025] Although sodium gluconate is not very effective at removing oxides, it has good rinsing properties. In this invention, the sodium gluconate content in the degreasing agent is set at 2%-5%.

[0026] Potassium chloride is used as an auxiliary cleaning agent, and the potassium chloride content in the degreasing agent is set at 1%-5%.

[0027] The experimental results show that the iron removal efficiency of the sodium oxalate-sodium gluconate-potassium chloride mixed system is more than 10 times that of the system using only sodium hydroxide, and the effect is good.

[0028] 3. Setting of surfactants

[0029] In the degreasing process, surfactants play various roles, including reducing surface tension, emulsifying, dispersing and solubilizing, wetting, and improving degreasing efficiency. They are indispensable in the degreasing process. The surfactants used in degreasing agents include two categories: anionic surfactants and nonionic surfactants. Anionic surfactants have the advantages of strong detergency, low cost, and good flowability, while nonionic surfactants have the advantages of wide applicability and good wetting properties. To reduce costs and improve wetting and rinsing ability, a mixed surfactant is composed of the widely adaptable anionic surfactant sodium dodecyl sulfate and the nonionic surfactant OP-10. To ensure that there is still a sufficient amount of surfactant after the mixed surfactant is diluted 15 to 25 times, the content of OP-10 in the degreasing agent is limited to 3%-6%, and the content of sodium dodecyl sulfate is limited to 4%-8%.

[0030] Sodium dodecyl sulfonate has low solubility in water and tends to precipitate at low temperatures. Sodium fatty alcohol polyoxyethylene ether sulfate has the characteristics of both anionic and nonionic surfactants. Limiting the content of sodium fatty alcohol polyoxyethylene ether sulfate in degreasing agents to 1%-2% can not only effectively improve the solubility of sodium dodecyl sulfonate in water and ensure the stability of the degreasing agent solution, but also effectively improve the degreasing efficiency.

[0031] 4. Setting of defoamer

[0032] Surfactants, especially sodium dodecyl sulfonate, are low in cost, effective, and have low viscosity, but they produce a lot of foam when used. In industrial production, excessive foam not only increases consumption but also causes foam to spray from the degreasing tank, affecting production operations. Furthermore, excessive foam makes rinsing difficult.

[0033] Defoamers reduce surface tension and promote membrane drainage, thereby eliminating foam during degreasing. The most commonly used defoamers are silicone-based. Experiments show that adding approximately 1‰ defoamer to diluted degreasing agent can effectively eliminate foam. Considering the complexity of actual production and the necessity of ensuring rinsing effectiveness, the content of silicone defoamer in degreasing agents is limited to 2%-4%.

[0034] The preparation method of the above-mentioned degreasing agent includes the following steps:

[0035] 1) Weigh out sodium gluconate, sodium oxalate and potassium chloride according to the ratio, add a certain amount of deionized water, stir until completely dissolved to obtain solution A, and set aside.

[0036] 2) Weigh sodium hydroxide and potassium hydroxide according to the ratio, and slowly add the two reagents to solution A, stirring until completely dissolved to obtain solution B, which is then set aside.

[0037] 3) Weigh out OP-10, sodium dodecylbenzenesulfonate and sodium fatty alcohol polyoxyethylene ether sulfate according to the ratio, add them to solution B, add the remaining deionized water according to the ratio, and stir until completely dissolved to obtain the finished degreasing agent.

[0038] The reagents used in this method can be used after mixing. Sodium gluconate, sodium oxalate, and potassium chloride are common salts and can be dissolved first. Sodium hydroxide and potassium hydroxide dissolve with significant exothermic reactions and require constant stirring to prevent localized boiling. Surfactants OP-10 and AES are liquids and do not have dissolution issues. Sodium dodecyl sulfonate is a solid with good solubility at high temperatures, so it is added later using the exothermic reaction of the solution. After cooling, sodium dodecyl sulfonate does not easily precipitate from the solution with the assistance of sodium fatty alcohol polyoxyethylene ether sulfate.

[0039] The method for degreasing the substrate of cold-rolled hot-dip aluminized zinc steel sheet using the above-mentioned degreasing agent includes the following steps:

[0040] 1) Dilute the degreasing agent with deionized water 15-25 times; heat the diluted degreasing agent to 70-80℃;

[0041] 2) Degreasing treatment is performed on the substrate of cold-rolled hot-dip aluminized zinc steel sheet using a combination of spray degreasing, brushing, and electrolytic degreasing. The degreasing speed is controlled at 50-200 m / min, and the degreasing time is 5-18 s. The current density for electrolytic cleaning of the steel sheet is 8-15 A / dm³. 2 ;

[0042] 3) Clean the steel plate. Clean the degreased steel plate by rinsing it with deionized water at a temperature of 30-60℃, and then drying it with hot air at a temperature of 80-120℃.

[0043] The degreasing efficiency of the degreased steel plate surface was tested. The degreasing efficiency of the steel plate surface after degreasing according to the method of the present invention is ≥90%, which is significantly higher than the industry cleaning requirement of 80%.

[0044] The reasons for adopting the above application method in this invention are as follows:

[0045] The degreasing agent of this invention is a concentrated liquid, which is easy to store and transport. The content of each component is designed according to the required content after dilution of 15-25 times.

[0046] At higher temperatures, the rate of degreasing and deoxidation increases due to enhanced molecular thermal motion. Generally, the degreasing temperature used in industry is between 70℃ and 80℃, as excessively high temperatures may cause the solution to boil and become uncontrollable.

[0047] During the degreasing process, the steel plate speed is determined by the steel plate thickness. This invention controls the steel plate speed between 50-200 m / min, with a degreasing time of 5-18 seconds. The degreasing process combines spraying, brushing, and electrolytic degreasing. Spraying is a chemical degreasing method. Brushing and spraying degreasing are performed in the same working tank, with brushing significantly enhancing the effect of spraying degreasing. Electrolytic degreasing is located after the chemical degreasing section, with a length and degreasing time approximately half that of spraying degreasing. The electrolytic process conditions are basically the same as those in industry production lines. After degreasing, a rinsing process is used to remove residual degreasing agent from the steel plate surface. The rinsing temperature is reduced from 70℃-80℃ to 30℃-60℃ to reduce steam costs. After rinsing, the steel plate is dried with hot air.

[0048] The degreasing agent of this invention uses a combination of oxalate-gluconate-potassium chloride, wherein oxalate acts as a strong ligand, gluconate acts as a weak ligand, and potassium chloride acts as a penetrating aid, which has a strong ability to remove iron oxides and can enhance the removal of oxides from the surface of steel plates; experiments show that the degreasing agent of this invention removes oxides at a rate 10 times faster than the traditional sodium hydroxide system.

[0049] The degreasing agent of this invention does not contain phosphates, because phosphates are mainly used for softening water, while hot-dip galvanizing degreasing solutions use deionized water, so phosphates are not very useful and can easily cause environmental pollution. The degreasing agent of this invention uses OP-10, sodium dodecylbenzene sulfonate and 1%-2% AES ternary surfactant. The main purpose is to use AES to enhance the stability of sodium dodecylbenzene sulfonate in solution, and to ensure a balance between cost and efficiency by adjusting the ratio of sodium hydroxide to potassium hydroxide.

[0050] Compared with existing technologies, this invention has the following advantages: 1. The degreasing agent of this invention can remove residual oil and iron oxides from the surface of steel plates under alkaline conditions. Compared with traditional alkaline degreasing systems, it has a stronger ability to remove iron oxides. Compared with acidic degreasing systems, it does not use phosphoric acid, making it environmentally friendly and less corrosive to the steel substrate. 2. The degreasing agent of this invention is suitable for removing residual oil and iron oxides from the surface of cold-rolled hot-dip aluminized zinc steel plates. It has strong degreasing and iron removal capabilities and good performance. It can also be used in applications such as electroplated tin substrates where the removal of iron oxides from the steel plate surface is critical. 3. The method of this invention is convenient to operate and safe and reliable. Detailed Implementation

[0051] The present invention will be further described below with reference to Examples 1-3.

[0052] Example 1: A degreasing agent for the substrate of cold-rolled hot-dip aluminized zinc steel sheet, the weight percentage of its components is as follows: sodium hydroxide 12%, potassium hydroxide 6%, surfactant OP-10 3%, sodium dodecylbenzene sulfonate 4%, sodium fatty alcohol polyoxyethylene ether sulfate 1%, sodium oxalate 3%, sodium gluconate 2%, potassium chloride 1%, organosilicon defoamer 2%, and the remainder is deionized water.

[0053] The preparation method of the above-mentioned degreasing agent includes the following steps:

[0054] 1) Weigh out sodium gluconate, sodium oxalate and potassium chloride according to the ratio, add a certain amount of deionized water, stir until completely dissolved, and set aside.

[0055] 2) Weigh sodium hydroxide and potassium hydroxide according to the ratio, and slowly add the two reagents to the above solution while stirring continuously until completely dissolved;

[0056] 3) Weigh out OP-10, sodium dodecylbenzenesulfonate and AES according to the ratio, add them to the above solution, add the remaining deionized water according to the ratio, and stir until completely dissolved.

[0057] The method for degreasing the substrate of cold-rolled hot-dip aluminized zinc steel sheet using the above-mentioned degreasing agent includes the following steps:

[0058] 1) Dilute the degreasing agent with water 15 times; heat the diluted degreasing agent to 72℃;

[0059] 2) The substrate of the cold-rolled hot-dip aluminized zinc steel sheet was degreased using a combination of spray degreasing agent and electrolytic degreasing. The degreasing speed was controlled at 130 m / min, and the degreasing time was 6.9 s. The current density for electrolytic degreasing was 12 A / dm³. 2 ;

[0060] 3) Clean the steel plate. Clean the degreased steel plate by rinsing it with pure water at 45°C and then drying it with hot air at 110°C.

[0061] After degreasing, the degreasing efficiency of the steel plate was tested, and the test results are shown in Table 1.

[0062] Example 2: A degreasing agent for the substrate of cold-rolled hot-dip aluminized zinc steel sheet, the weight percentage of its components is as follows: sodium hydroxide 20%, potassium hydroxide 10%, surfactant OP-10 5%, sodium dodecylbenzene sulfonate 7%, sodium fatty alcohol polyoxyethylene ether sulfate 2%, sodium oxalate 9%, sodium gluconate 5%, potassium chloride 3%, organosilicon defoamer 4%, and the remainder is deionized water.

[0063] The preparation method of the above-mentioned degreasing agent includes the following steps:

[0064] 1) Weigh out sodium gluconate, sodium oxalate and potassium chloride according to the ratio, add a certain amount of deionized water, stir until completely dissolved, and set aside.

[0065] 2) Weigh sodium hydroxide and potassium hydroxide according to the ratio, and slowly add the two reagents to the above solution while stirring continuously until completely dissolved;

[0066] 3) Weigh out OP-10, sodium dodecylbenzenesulfonate and AES according to the ratio, add them to the above solution, add the remaining water according to the ratio, and stir until completely dissolved.

[0067] The method for degreasing the substrate of cold-rolled hot-dip aluminized zinc steel sheet using the above-mentioned degreasing agent includes the following steps:

[0068] 1) Dilute the degreasing agent 25 times with deionized water; heat the diluted degreasing agent to 75℃;

[0069] 2) The substrate of the cold-rolled hot-dip aluminized zinc steel sheet was degreased using a combination of spray washing and electrolytic degreasing. The degreasing speed was controlled at 170 m / min, and the degreasing time was 5.3 s. The current density for electrolytic degreasing was 12 A / dm³. 2 ;

[0070] 3) Clean the steel plate. Clean the degreased steel plate by rinsing it with pure water at 50°C and then drying it with hot air at 105°C.

[0071] After degreasing, the degreasing efficiency of the steel plate was tested, and the test results are shown in Table 1.

[0072] Example 3: A degreasing agent for the substrate of cold-rolled hot-dip aluminized zinc steel sheet, the weight percentage of its components is as follows: sodium hydroxide 15%, potassium hydroxide 10%, surfactant OP-10 4%, sodium dodecylbenzene sulfonate 5%, sodium fatty alcohol polyoxyethylene ether sulfate 2%, sodium oxalate 6%, sodium gluconate 4%, potassium chloride 4%, organosilicon defoamer 4%, and the remainder is deionized water.

[0073] The preparation method of the above-mentioned degreasing agent includes the following steps:

[0074] 1) Weigh out sodium gluconate, sodium oxalate and potassium chloride according to the ratio, add a certain amount of deionized water, stir until completely dissolved, and set aside.

[0075] 2) Weigh sodium hydroxide and potassium hydroxide according to the ratio, and slowly add the two reagents to the above solution while stirring continuously until completely dissolved;

[0076] 3) Weigh out OP-10, sodium dodecylbenzenesulfonate and AES according to the ratio, add them to the above solution, add the remaining water according to the ratio, and stir until completely dissolved.

[0077] The method for degreasing the substrate of cold-rolled hot-dip aluminized zinc steel sheet using the above-mentioned degreasing agent includes the following steps:

[0078] 1) Dilute the degreasing agent 20 times with deionized water; heat the diluted degreasing agent to 78°C;

[0079] 2) The substrate of the cold-rolled hot-dip aluminized zinc steel sheet was degreased using a combination of spray washing and electrolytic degreasing. The degreasing speed was controlled at 70 m / min, and the degreasing time was 12.9 s. The current density for electrolytic degreasing was 10 A / dm³. 2 ;

[0080] 3) Clean the steel plate. Clean the degreased steel plate by rinsing it with pure water at 55°C and then drying it with hot air at 105°C.

[0081] After degreasing, the degreasing efficiency of the steel plate surface was tested, and the test results are shown in Table 1.

[0082] Table 1 Degreasing parameters of steel plates in embodiments of the present invention

[0083]

[0084] When there is residual oil on the surface of the steel plate, a water film cannot be formed. The degreasing efficiency is taken as the ratio of the area of ​​the water film on the surface of the steel plate after rinsing to the total area of ​​the steel plate.

[0085] As shown in Table 1, the degreasing efficiency of the steel plates in Examples 1-3 is all above 90%, which meets the usage requirements.

[0086] In addition to the embodiments described above, the present invention may have other implementations. All technical solutions formed by equivalent substitution or equivalent transformation fall within the protection scope claimed by the present invention.

Claims

1. A degreasing agent for the substrate of cold-rolled hot-dip aluminized zinc steel sheet, characterized in that, The degreasing agent consists of the following components by weight percentage: sodium hydroxide 10%-25%, potassium hydroxide 5%-15%, surfactant OP-10 3%-6%, sodium dodecylbenzenesulfonate 4%-8%, sodium fatty alcohol polyoxyethylene ether sulfate 1%-2%, sodium oxalate 2%-10%, sodium gluconate 2%-5%, potassium chloride 1%-5%, silicone defoamer 2%-4%, and the remainder being deionized water.

2. The method for preparing the degreasing agent for the substrate of cold-rolled hot-dip aluminized zinc steel sheet as described in claim 1, characterized in that, Includes the following steps: 1) Weigh out sodium gluconate, sodium oxalate and potassium chloride according to the ratio, add a certain amount of deionized water, stir until completely dissolved to obtain solution A, and set aside. 2) Weigh sodium hydroxide and potassium hydroxide according to the ratio, and slowly add the two reagents to solution A, stirring until completely dissolved to obtain solution B, which is then set aside. 3) Weigh out OP-10, sodium dodecylbenzenesulfonate and sodium fatty alcohol polyoxyethylene ether sulfate according to the ratio, add them to solution B, add the remaining deionized water according to the ratio, and stir until completely dissolved to obtain the finished degreasing agent.

3. A method for degreasing a substrate of cold-rolled hot-dip aluminized zinc steel sheet, using the degreasing agent described in claim 1, comprising the following steps: 1) Dilute the degreasing agent with deionized water 15-25 times; heat the diluted degreasing agent to 70-80℃; 2) Degreasing treatment is performed on the substrate of cold-rolled hot-dip aluminized zinc steel sheet using a combination of spray degreasing, brushing, and electrolytic degreasing. The degreasing speed is controlled at 50-200 m / min, and the degreasing time is 5-18 s. The current density for electrolytic cleaning of the steel sheet is 8-15 A / dm³. 2 ; 3) Clean the steel plate. Clean the degreased steel plate by rinsing it with deionized water at a temperature of 30-60℃, and then drying it with hot air at a temperature of 80-120℃.

4. The method for degreasing the substrate of cold-rolled hot-dip aluminized zinc steel sheet as described in claim 3, characterized in that, The degreasing efficiency of the degreased steel plate surface was tested, and the degreasing efficiency of the steel plate surface was ≥90%.

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