Hot-dip galvanized steel plate with high hole expansion rate and preparation process thereof

Abstract

The invention discloses a hot-dip galvanized steel plate with a high hole expansion rate and a preparation process thereof, and belongs to the field of steel plate manufacturing. The hot-dip galvanized steel plate provided by the invention comprises a base plate layer, a substrate bonding layer and a response processing layer which are stacked in sequence, firstly gamma-APS silane, hydrophobic nano SiO2, a pH regulator and a wetting agent are sequentially added into a sodium molybdate solution, and a substrate bonding layer solution is obtained after mixing; then sequentially adding a pore-forming agent, a stress response microcapsule, a dispersing agent, a catalyst and a flatting agent into the waterborne polyurethane dispersion, mixing and sieving to obtain a response treatment layer solution; and finally, carrying out alkaline degreasing on the substrate, drying, sequentially coating the substrate bonding layer solution and the response treatment layer solution, and curing and cooling to obtain the product. The hot-dip galvanized steel plate provided by the invention has excellent hole expansion rate, and the added stress response microcapsules can perform polymerization reaction at cracks during hole expansion to generate polymers to fill the cracks and prevent further expansion of the cracks.

Description

Technical Field

[0001] This invention belongs to the field of steel plate manufacturing, specifically relating to a hot-dip galvanized steel plate with high hole expansion ratio and its preparation process. Background Technology

[0002] With the development of the automotive industry, the performance requirements for automotive parts are becoming increasingly stringent, especially in terms of lightweighting, high strength, and corrosion resistance. Under high strength conditions, the plasticity and formability of traditional high-strength steel decrease sharply, leading to easy cracking during stamping, particularly during flanging and cavitation. Furthermore, high-strength steel has poor cavitation capacity, making it unsuitable for manufacturing parts requiring cavitation and bending forming. Existing technologies improve hardenability by adding elements such as Cr and Mo, but these elements are expensive, increasing production costs.

[0003] In summary, high-strength steel has shortcomings in hole expansion performance, making it difficult to meet the complex forming requirements of automotive parts. Therefore, it is essential to propose a hot-dip galvanized steel sheet with a high hole expansion rate. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a hot-dip galvanized steel sheet with high hole expansion ratio and its preparation process.

[0005] The first aspect of the present invention is to provide a hot-dip galvanized steel sheet with high hole expansion ratio, comprising a substrate layer, a substrate bonding layer and a response treatment layer stacked sequentially; The material forming the responsive treatment layer includes stress-responsive microcapsules, which are prepared by the following steps: (1) Mix the ionic liquid, dicyclopentadiene, and stabilizer to obtain a mixed oil phase; (2) Add emulsifier to the mixed oil phase obtained in step (1) and mix to obtain an emulsion; (3) Add methyl methacrylate and initiator to the emulsion obtained in step (2), carry out free radical polymerization under inert gas protection, and after cooling, filter, wash and dry to obtain stress-responsive microcapsules.

[0006] It should be noted that the present invention uses polymethyl methacrylate (PMMA) as the shell layer to encapsulate ionic liquid, dicyclopentadiene, and stabilizer to form stress-responsive microcapsules. Since PMMA has fewer free-moving segments in its molecular chain, the ionic liquid has low permeability to it, making it suitable as a microcapsule shell material. In addition, MMA monomer has low water solubility and can preferentially accumulate at the oil-water interface and quickly form polymers, which is beneficial for the encapsulation of the core material.

[0007] In some embodiments, the mass ratio of ionic liquid to dicyclopentadiene is 2-4:0.5-1.5; the amount of methyl methacrylate used is the sum of the amounts of ionic liquid and dicyclopentadiene.

[0008] In some embodiments, the ionic liquid is selected from at least one of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, dodecylbenzenesulfonate quaternary phosphorus salt, and 1-ethyl-3-methylimidazolium bis(maleic acid boron) salt; the stabilizer is selected from at least one of Span 80 and polyvinyl butyral; the emulsifier is selected from at least one of sodium dodecyl sulfate and sodium dinonylnaphthalenesulfonate; and the initiator is selected from at least one of potassium persulfate and ammonium persulfate.

[0009] In some embodiments, the amount of stabilizer is 5-6% of the amount of ionic liquid; the amount of emulsifier is 1-3% of the mass of the mixed oil phase; and the amount of initiator is 0.3-1% of the amount of methyl methacrylate.

[0010] In some embodiments, in step (3), the free radical polymerization reaction temperature is 70-80°C and the reaction time is 4-6h.

[0011] A second aspect of this invention is to provide a process for preparing a hot-dip galvanized steel sheet with a high hole expansion ratio, comprising the following steps: S1: Add γ-APS silane, hydrophobic nano-SiO2, pH adjuster and wetting agent sequentially to sodium molybdate solution, and mix to obtain substrate bonding layer solution; wherein, the mass ratio of sodium molybdate, γ-APS silane and hydrophobic nano-SiO2 is 0.5-0.8:0.8-1.2:0.3-0.5; S2: A pore-forming agent, stress-responsive microcapsules, a dispersant, a catalyst, and a leveling agent are added sequentially to an aqueous polyurethane dispersion. After mixing and sieving, a response treatment layer solution is obtained. The mass ratio of the aqueous polyurethane dispersion to the stress-responsive microcapsules is 5.5-6:3-3.5. S3: After alkaline degreasing and drying of the substrate, the substrate bonding layer solution and the response treatment layer solution are coated in sequence. After curing and cooling, a hot-dip galvanized steel sheet with high porosity is obtained.

[0012] This solution does not restrict the substrate of the hot-dip galvanized steel sheet, including but not limited to hot-dip galvanized steel sheet, composite galvanized steel sheet, and alloyed galvanized steel sheet.

[0013] In some embodiments, the pH adjuster is selected from at least one of acetic acid, formic acid, citric acid, and nitric acid; the wetting agent is selected from at least one of BYK-3451 and TEGO Wet 270; the pore-forming agent is selected from at least one of isopropanol, ethanol, tert-butanol, and acetone; the dispersant is selected from at least one of polyether siloxane and polycarboxylate; the catalyst is selected from at least one of bis(trifluoroacetylacetone)vanadium oxide, triisopropoxyvanadium oxide, and vanadium acetylacetone salt; and the leveling agent is selected from at least one of BYK-349 and Tego Flow 300.

[0014] It should be noted that in this invention, the vanadium catalyst (bis(trifluoroacetylacetonate)vanadium oxide, triisopropoxyvanadium oxide, vanadium acetylacetonate salt) catalyzes the ring-opening polymerization of dicyclopentadiene DCPD through a coordination activation mechanism, and the vanadium ions (V 3+ It preferentially binds to the intracyclic double bonds of DCPD, weakening its bond energy and triggering a ring-opening reaction to generate an active polymer chain; this chain continuously inserts into the adjacent DCPD monomer, rapidly forming a high-toughness polydicyclopentadiene (PDCPD) network within the crack, thus achieving crack self-healing.

[0015] In some embodiments, the amount of pH adjuster is 8-18% of the amount of sodium molybdate; the amount of wetting agent is 4-8% of the amount of sodium molybdate; the amount of pore-forming agent is 17-27% of the amount of stress-responsive microcapsules; and the mass ratio of pore-forming agent, dispersant, catalyst and leveling agent is 0.6-0.8:0.08-0.12:0.5-0.7:0.02-0.03.

[0016] In some embodiments, in S1, the pH adjuster adjusts the pH value to 5-5.5; in S2, the solid content of the waterborne polyurethane dispersion is 35-45%, and the sieve mesh is 80-120 mesh; in S3, the curing temperature is 80-110℃, and the cooling temperature is 35-45℃.

[0017] In some embodiments, the substrate bonding layer solution coating thickness is 8-12 μm; the response treatment layer solution coating thickness is 15-20 μm.

[0018] Compared with the prior art, the present invention has the following beneficial effects: 1. The hot-dip galvanized steel sheet with high porosity provided by the present invention adopts a substrate-bonding layer-response treatment layer structure. The purpose of the substrate bonding layer is to strengthen the anchoring of the film layer and the steel sheet through a silane-molybdate hybrid network. γ-APS silane hydrolysis forms Si-OH, which easily forms covalent bonds with Fe-OH on the surface of the steel sheet. Molybdate improves the film layer density by filling the network pores. Hydrophobic nano-SiO2 particles are embedded in the hybrid network to improve the film layer modulus. The response treatment layer is embedded in the bonding layer by the weight of microcapsules, and the two layers exchange substances through the pore channels generated by the pore-forming agent to form a stable bond.

[0019] 2. This invention creatively incorporates stress-responsive microcapsules into the response treatment layer of hot-dip galvanized steel sheets. The PMMA shell of the stress-responsive microcapsules can rupture under stress during hole expansion in the steel sheet, releasing the core material (ionic liquid, dicyclopentadiene) in the high-risk deformation area and covering the hole edge region. The ionic liquid in the core material can spread on the metal surface to form a lubricating film, reducing the coefficient of friction. At the same time, the dicyclopentadiene in the core material is released and comes into contact with the catalyst in the response treatment layer to undergo a ring-opening polymerization reaction, generating a polymer product that fills the microcracks, thereby achieving a self-repair function for cracks, preventing further crack propagation, reducing the risk of hole expansion failure, and improving the hole expansion rate of the steel sheet. Detailed Implementation

[0020] The present invention will be further described in detail below with reference to specific embodiments.

[0021] Example 1 A hot-dip galvanized steel sheet with high hole expansion ratio includes a substrate layer, a substrate bonding layer and a response treatment layer stacked sequentially. The material forming the responsive treatment layer includes stress-responsive microcapsules, which are prepared by the following steps: (1) Mix 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt and dicyclopentadiene in a mass ratio of 3:1, and then add Span 80 to obtain a mixed oil phase; (2) Add sodium dodecyl sulfate to the mixed oil phase obtained in step (1) and mix to obtain an emulsion; (3) Add methyl methacrylate and potassium persulfate to the emulsion obtained in step (2), and carry out free radical polymerization reaction at 75°C for 5 h under inert gas protection. After cooling, filter, wash and dry to obtain stress-responsive microcapsules.

[0022] In this embodiment, the amount of methyl methacrylate used is the sum of the amounts of ionic liquid and dicyclopentadiene; the amount of stabilizer used is 5.5% of the amount of ionic liquid used; the amount of emulsifier used is 2% of the mass of the mixed oil phase; and the amount of initiator used is 0.6% of the amount of methyl methacrylate used.

[0023] The above-mentioned hot-dip galvanized steel sheet with high hole expansion ratio is prepared by the following steps: S1: Add γ-APS silane and hydrophobic nano-SiO2 sequentially to the sodium molybdate solution, add acetic acid to adjust the pH to 5-5.5, then add wetting agent BYK-3451, and mix to obtain the substrate bonding layer solution; S2: Isopropanol, stress-responsive microcapsules, polyether siloxane, bis(trifluoroacetylacetone)vanadium oxide and leveling agent BYK-349 are added sequentially to an aqueous polyurethane dispersion with a solid content of 35-45%. After mixing, the mixture is sieved through 100 mesh to obtain the response treatment layer solution. S3: After alkaline degreasing and drying of the GA590 steel plate surface, a 10 μm thick base bonding layer solution and a 17 μm thick response treatment layer solution are sequentially coated. The solution is cured at 100℃ and then cooled at 40℃ to obtain a hot-dip galvanized steel plate with high porosity.

[0024] In this embodiment, in S1, the mass ratio of sodium molybdate, γ-APS silane, and hydrophobic nano-SiO2 is 0.6:1:0.4; the amount of pH adjuster is 15% of the amount of sodium molybdate; and the amount of wetting agent is 6% of the amount of sodium molybdate. In S2, the mass ratio of aqueous polyurethane dispersion and stress-responsive microcapsules is 6:3.5; the amount of pore-forming agent is 25% of the amount of stress-responsive microcapsules; and the mass ratio of pore-forming agent, dispersant, catalyst, and leveling agent is 0.7:0.1:0.6:0.025.

[0025] Example 2 A hot-dip galvanized steel sheet with high hole expansion ratio includes a substrate layer, a substrate bonding layer and a response treatment layer stacked sequentially. The material forming the responsive treatment layer includes stress-responsive microcapsules, which are prepared by the following steps: (1) Dodecylbenzenesulfonic acid quaternary phosphate salt and dicyclopentadiene in a mass ratio of 4:1.5 were mixed with polyvinyl butyral to obtain a mixed oil phase; (2) Add sodium dinonylnaphthalenesulfonate to the mixed oil phase obtained in step (1) and mix to obtain an emulsion; (3) Add methyl methacrylate and ammonium persulfate to the emulsion obtained in step (2), and carry out free radical polymerization reaction at 80°C for 4 h under inert gas protection. After cooling, filter, wash and dry to obtain stress-responsive microcapsules.

[0026] In this embodiment, the amount of methyl methacrylate is equal to the sum of the amounts of ionic liquid and dicyclopentadiene; the amount of stabilizer is 6% of the amount of ionic liquid; the amount of emulsifier is 3% of the mass of the mixed oil phase; and the amount of initiator is 1% of the amount of methyl methacrylate.

[0027] The above-mentioned hot-dip galvanized steel sheet with high hole expansion ratio is prepared by the following steps: S1: Add γ-APS silane and hydrophobic nano-SiO2 sequentially to the sodium molybdate solution, add formic acid to adjust the pH to 5.5, then add wetting agent TEGO Wet 270, and mix to obtain the substrate bonding layer solution; S2: Ethanol, stress-responsive microcapsules, polycarboxylate, triisopropoxyvanadium oxide and leveling agent Tego Flow 300 are added sequentially to an aqueous polyurethane dispersion with a solid content of 45%. After mixing, the mixture is sieved through a 120-mesh sieve to obtain the response treatment layer solution. S3: The surface of GA590 steel plate is degreased with alkaline solution and dried. Then, a base bonding layer solution with a thickness of 12 μm and a response treatment layer solution with a thickness of 20 μm are coated in sequence. The solution is cured at 110℃ and then cooled at 45℃ to obtain a hot-dip galvanized steel plate with high porosity.

[0028] In this embodiment, in S1, the mass ratio of sodium molybdate, γ-APS silane, and hydrophobic nano-SiO2 is 0.8:1.2:0.5, the amount of pH adjuster is 18% of the amount of sodium molybdate, and the amount of wetting agent is 8% of the amount of sodium molybdate. In S2, the mass ratio of aqueous polyurethane dispersion and stress-responsive microcapsules is 5:3.5, the amount of pore-forming agent is 27% of the amount of stress-responsive microcapsules, and the mass ratio of pore-forming agent, dispersant, catalyst, and leveling agent is 0.8:0.12:0.7:0.03.

[0029] Example 3 A hot-dip galvanized steel sheet with high hole expansion ratio includes a substrate layer, a substrate bonding layer and a response treatment layer stacked sequentially. The material forming the responsive treatment layer includes stress-responsive microcapsules, which are prepared by the following steps: (1) 1-ethyl-3-methylimidazolium bismaleic acid borate and dicyclopentadiene in a mass ratio of 2:0.5 were mixed with Span 80 to obtain a mixed oil phase; (2) Add sodium dodecyl sulfate to the mixed oil phase obtained in step (1) and mix to obtain an emulsion; (3) Add methyl methacrylate and potassium persulfate to the emulsion obtained in step (2), and carry out free radical polymerization reaction at 70°C for 6 h under inert gas protection. After cooling, filter, wash and dry to obtain stress-responsive microcapsules.

[0030] In this embodiment, the amount of methyl methacrylate is equal to the sum of the amounts of ionic liquid and dicyclopentadiene; the amount of stabilizer is 5% of the amount of ionic liquid; the amount of emulsifier is 1% of the mass of the mixed oil phase; and the amount of initiator is 0.3% of the amount of methyl methacrylate.

[0031] The above-mentioned hot-dip galvanized steel sheet with high hole expansion ratio is prepared by the following steps: S1: Add γ-APS silane and hydrophobic nano-SiO2 sequentially to the sodium molybdate solution, add citric acid to adjust the pH to 5, then add wetting agent BYK-3451, and mix to obtain the substrate bonding layer solution; S2: Tert-butanol, stress-responsive microcapsules, polyether siloxane, vanadium acetylacetonate and leveling agent BYK-349 are added sequentially to an aqueous polyurethane dispersion with a solid content of 35%. After mixing, the mixture is sieved through 80 mesh to obtain the response treatment layer solution. S3: After alkaline degreasing and drying of the GA590 steel plate surface, a base bonding layer solution with a thickness of 8 μm and a response treatment layer solution with a thickness of 15 μm are applied in sequence. The solution is cured at 80℃ and then cooled at 35℃ to obtain a hot-dip galvanized steel plate with high porosity.

[0032] In this embodiment, in S1, the mass ratio of sodium molybdate, γ-APS silane, and hydrophobic nano-SiO2 is 0.5:0.8:0.3, the amount of pH adjuster is 8% of the amount of sodium molybdate, and the amount of wetting agent is 8% of the amount of sodium molybdate. In S2, the mass ratio of aqueous polyurethane dispersion and stress-responsive microcapsules is 5:3.5, the amount of pore-forming agent is 17% of the amount of stress-responsive microcapsules, and the mass ratio of pore-forming agent, dispersant, catalyst, and leveling agent is 0.6:0.08:0.5:0.02.

[0033] Example 4 A hot-dip galvanized steel sheet with high hole expansion ratio includes a substrate layer, a substrate bonding layer and a response treatment layer stacked sequentially. The material forming the responsive treatment layer includes stress-responsive microcapsules, which are prepared by the following steps: (1) 1-Ethyl-3-methylimidazolium bismaleic acid borate and dicyclopentadiene in a mass ratio of 3:0.8 were then added to Span 80 and mixed to obtain a mixed oil phase; (2) Add sodium dodecyl sulfate to the mixed oil phase obtained in step (1) and mix to obtain an emulsion; (3) Add methyl methacrylate and potassium persulfate to the emulsion obtained in step (2), and carry out free radical polymerization reaction at 75°C for 5 h under inert gas protection. After cooling, filter, wash and dry to obtain stress-responsive microcapsules.

[0034] In this embodiment, the amount of methyl methacrylate is equal to the sum of the amounts of ionic liquid and dicyclopentadiene; the amount of stabilizer is 5% of the amount of ionic liquid; the amount of emulsifier is 2% of the mass of the mixed oil phase; and the amount of initiator is 0.5% of the amount of methyl methacrylate.

[0035] The above-mentioned hot-dip galvanized steel sheet with high hole expansion ratio is prepared by the following steps: S1: Add γ-APS silane and hydrophobic nano-SiO2 sequentially to sodium molybdate solution, adjust the pH to 5 with nitric acid, then add wetting agent BYK-3451, and mix to obtain substrate bonding layer solution; S2: Acetone, stress-responsive microcapsules, polyether siloxane, bis(trifluoroacetylacetone)vanadium oxide and leveling agent BYK-349 are added sequentially to an aqueous polyurethane dispersion with a solid content of 40%. After mixing, the mixture is sieved through a 90-mesh sieve to obtain the response treatment layer solution. S3: After alkaline degreasing and drying of the GA590 steel plate surface, a base bonding layer solution with a thickness of 9 μm and a response treatment layer solution with a thickness of 16 μm are sequentially coated. The solution is cured at 90℃ and then cooled at 40℃ to obtain a hot-dip galvanized steel plate with high porosity.

[0036] In this embodiment, in S1, the mass ratio of sodium molybdate, γ-APS silane, and hydrophobic nano-SiO2 is 0.7:1.2:0.4; the amount of pH adjuster is 12% of the amount of sodium molybdate; and the amount of wetting agent is 5% of the amount of sodium molybdate. In S2, the mass ratio of aqueous polyurethane dispersion and stress-responsive microcapsules is 5.7:3; the amount of pore-forming agent is 22% of the amount of stress-responsive microcapsules; and the mass ratio of pore-forming agent, dispersant, catalyst, and leveling agent is 0.7:0.09:0.6:0.02.

[0037] Example 5 A hot-dip galvanized steel sheet with high hole expansion ratio includes a substrate layer, a substrate bonding layer and a response treatment layer stacked sequentially. The material forming the responsive treatment layer includes stress-responsive microcapsules, which are prepared by the following steps: (1) 1-Ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt and dicyclopentadiene in a mass ratio of 3:1.2 were then added to Span 80 and mixed to obtain a mixed oil phase; (2) Add sodium dodecyl sulfate to the mixed oil phase obtained in step (1) and mix to obtain an emulsion; (3) Add methyl methacrylate and potassium persulfate to the emulsion obtained in step (2), and carry out free radical polymerization reaction at 75°C for 5 h under inert gas protection. After cooling, filter, wash and dry to obtain stress-responsive microcapsules.

[0038] In this embodiment, the amount of methyl methacrylate is equal to the sum of the amounts of ionic liquid and dicyclopentadiene; the amount of stabilizer is 6% of the amount of ionic liquid; the amount of emulsifier is 2% of the mass of the mixed oil phase; and the amount of initiator is 0.8% of the amount of methyl methacrylate.

[0039] The above-mentioned hot-dip galvanized steel sheet with high hole expansion ratio is prepared by the following steps: S1: Add γ-APS silane and hydrophobic nano-SiO2 sequentially to the sodium molybdate solution, add acetic acid to adjust the pH to 5, then add wetting agent TEGO Wet 270, and mix to obtain the substrate bonding layer solution; S2: Isopropanol, stress-responsive microcapsules, polyether siloxane, bis(trifluoroacetylacetone)vanadium oxide and leveling agent BYK-349 are added sequentially to an aqueous polyurethane dispersion with a solid content of 40%. After mixing, the mixture is sieved through 110 mesh to obtain the response treatment layer solution. S3: After alkaline degreasing and drying of the GA590 steel plate surface, a base bonding layer solution with a thickness of 11 μm and a response treatment layer solution with a thickness of 19 μm are applied in sequence. The solution is cured at 110℃ and then cooled at 45℃ to obtain a hot-dip galvanized steel plate with high porosity.

[0040] In this embodiment, in S1, the mass ratio of sodium molybdate, γ-APS silane, and hydrophobic nano-SiO2 is 0.6:1.1:0.4; the amount of pH adjuster is 16% of the amount of sodium molybdate; and the amount of wetting agent is 7% of the amount of sodium molybdate. In S2, the mass ratio of aqueous polyurethane dispersion and stress-responsive microcapsules is 6:3; the amount of pore-forming agent is 25% of the amount of stress-responsive microcapsules; and the mass ratio of pore-forming agent, dispersant, catalyst, and leveling agent is 0.7:0.11:0.6:0.03.

[0041] Comparative Example 1 It is basically the same as Example 1, except that: In this embodiment, the response processing layer is not coated; instead, the coating thickness of the response processing layer is superimposed onto the substrate bonding layer.

[0042] Comparative Example 2 It is basically the same as Example 1, except that: In this embodiment, the substrate bonding layer is not coated; instead, the coating thickness of the substrate bonding layer is superimposed onto the response processing layer.

[0043] Comparative Example 3 It is basically the same as Example 1, except that: In this embodiment, no stress-responsive microcapsules are added to the response processing layer.

[0044] To demonstrate that the hot-dip galvanized steel sheet provided by the present invention has excellent hole expansion rate, performance tests were conducted on Examples 1-5 and Comparative Examples 1-3, and the test results are shown in Table 1.

[0045] The relevant performance testing methods are as follows: Tensile property testing: using The standard is to conduct tensile tests to test the yield strength, tensile strength and elongation of the steel plates in each embodiment and comparative example.

[0046] Hole enlargement test: The hole enlargement rate is determined by the hole enlargement test. A punch is used to press the specimen with a central hole into a die to enlarge the central hole of the specimen until necking or through cracks appear at the edge of the hole. The original central hole of the specimen is prepared by punching and reaming respectively. Subsequent tests and testing methods are performed according to the hole enlargement rate test method specified in ISO / DIS 16630 standard.

[0047] Peeling resistance test: The hot-dip galvanized steel sheets prepared in each example and comparative example were subjected to 18 cycles of hot and cold cycling, and the peeling and blistering of the film layer were recorded.

[0048] Table 1 As can be seen from Table 1, the hot-dip galvanized steel sheet provided by the embodiments of the present invention has excellent hole expansion rate whether it is punched or reamed, and the film layer can be well bonded to the substrate and is not easy to fall off. In addition, the hot-dip galvanized steel sheet provided by the present invention also has good mechanical properties.

[0049] As can be seen from the comparative examples, Comparative Example 1, without a response treatment layer, cannot generate polymers in the microcracks to achieve self-repair, and cannot form a lubricating film on the substrate surface, resulting in a high coefficient of friction. Long cracks are more likely to occur during the hole-opening process, leading to hole-opening failure. Comparative Example 2, without a substrate bonding layer, makes the film layer easy to detach from the substrate surface. In Comparative Example 3, the response treatment layer did not contain stress-responsive microcapsules, so it also could not perform self-repair, and therefore the hole expansion rate also decreased significantly.

[0050] The above descriptions are merely some embodiments of the present invention. Those skilled in the art can make various modifications and improvements without departing from the inventive concept of the present invention, and these all fall within the scope of protection of the present invention.

Claims

1. A hot-dip galvanized steel sheet with high hole expansion ratio, characterized in that, It includes a substrate layer, a substrate bonding layer, and a response processing layer stacked sequentially; The material forming the response treatment layer comprises stress-responsive microcapsules, which are prepared by the following steps: (1) Mix the ionic liquid, dicyclopentadiene, and stabilizer to obtain a mixed oil phase; (2) Add emulsifier to the mixed oil phase obtained in step (1) and mix to obtain an emulsion; (3) Add methyl methacrylate and an initiator to the emulsion obtained in step (2), carry out free radical polymerization under inert gas protection, and after cooling, filter, wash and dry to obtain the stress-responsive microcapsules.

2. The hot-dip galvanized steel sheet with high hole expansion ratio according to claim 1, characterized in that, The mass ratio of the ionic liquid to the dicyclopentadiene is 2-4:0.5-1.5; the amount of methyl methacrylate used is the sum of the amounts of the ionic liquid and the dicyclopentadiene.

3. The hot-dip galvanized steel sheet with high hole expansion ratio according to claim 1, characterized in that, The ionic liquid is selected from at least one of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, dodecylbenzenesulfonate quaternary phosphorus salt, and 1-ethyl-3-methylimidazolium bis(maleic acid) boron salt; the stabilizer is selected from at least one of Span 80 and polyvinyl butyral; the emulsifier is selected from at least one of sodium dodecyl sulfate and sodium dinonylnaphthalenesulfonate; and the initiator is selected from at least one of potassium persulfate and ammonium persulfate.

4. The hot-dip galvanized steel sheet with high hole expansion ratio according to claim 3, characterized in that, The amount of stabilizer is 5-6% of the amount of ionic liquid; the amount of emulsifier is 1-3% of the mass of the mixed oil phase; and the amount of initiator is 0.3-1% of the amount of methyl methacrylate.

5. The hot-dip galvanized steel sheet with high hole expansion ratio according to claim 1, characterized in that, In step (3), the free radical polymerization reaction temperature is 70-80℃ and the reaction time is 4-6 h.

6. A process for preparing a hot-dip galvanized steel sheet with high hole expansion ratio according to any one of claims 1-5, characterized in that, Includes the following steps: S1: Add γ-APS silane, hydrophobic nano-SiO2, pH adjuster and wetting agent sequentially to sodium molybdate solution, and mix to obtain substrate bonding layer solution; wherein, the mass ratio of sodium molybdate, γ-APS silane and hydrophobic nano-SiO2 is 0.5-0.8:0.8-1.2:0.3-0.5; S2: A pore-forming agent, the stress-responsive microcapsules, a dispersant, a catalyst, and a leveling agent are added sequentially to the aqueous polyurethane dispersion. After mixing and sieving, a response treatment layer solution is obtained; wherein, the mass ratio of the aqueous polyurethane dispersion to the stress-responsive microcapsules is 5.5-6:3-3.

5. S3: After alkaline degreasing and drying of the substrate, the substrate bonding layer solution and the response treatment layer solution are coated in sequence. After curing and cooling, a hot-dip galvanized steel sheet with high porosity is obtained.

7. The preparation process of hot-dip galvanized steel sheet with high hole expansion ratio according to claim 6, characterized in that, The pH adjuster is selected from at least one of acetic acid, formic acid, citric acid, and nitric acid; the wetting agent is selected from at least one of BYK-3451 and TEGO Wet 270; the pore-forming agent is selected from at least one of isopropanol, ethanol, tert-butanol, and acetone; the dispersant is selected from at least one of polyether siloxane and polycarboxylate; the catalyst is selected from at least one of bis(trifluoroacetylacetone)vanadium oxide, triisopropoxyvanadium oxide, and vanadium acetylacetone salt; and the leveling agent is selected from at least one of BYK-349 and Tego Flow 300.

8. The preparation process of hot-dip galvanized steel sheet with high hole expansion ratio according to claim 7, characterized in that, The amount of pH adjuster is 8-18% of the amount of sodium molybdate; the amount of wetting agent is 4-8% of the amount of sodium molybdate; the amount of pore-forming agent is 17-27% of the amount of stress-responsive microcapsules; and the mass ratio of the pore-forming agent, the dispersant, the catalyst, and the leveling agent is 0.6-0.8:0.08-0.12:0.5-0.7:0.02-0.

03.

9. The preparation process of hot-dip galvanized steel sheet with high hole expansion ratio according to claim 6, characterized in that, In step S1, the pH adjuster adjusts the pH value to 5-5.5; in step S2, the solid content of the waterborne polyurethane dispersion is 35-45%, and the sieve mesh is 80-120 mesh; in step S3, the curing temperature is 80-110℃, and the cooling temperature is 35-45℃.

10. The preparation process of hot-dip galvanized steel sheet with high hole expansion ratio according to claim 6, characterized in that, The substrate bonding layer solution coating thickness is 8-12 μm; the response treatment layer solution coating thickness is 15-20 μm.

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