High cleanliness steel and method for producing the same

Abstract

The present application relates to the field of steel production, in particular to a high-cleanliness steel and a preparation method thereof. The present application first adopts a "converter-LF-RH-continuous casting" process to smelt steel; then triphenylmethane triisocyanate and glycidol reaction product are further reacted with tetrafluorobutane diol and 2-methyl-2-acrylic acid-2-isocyanate ethyl ester reaction product to obtain an epoxy-modified fluorine-containing monomer; then the epoxy-modified fluorine-containing monomer is dispersed in epoxy resin, and butyl acrylate and methyl methacrylate are added to polymerize to obtain a fluorine-containing acrylate polymer modified epoxy resin; finally, the fluorine-containing acrylate polymer modified epoxy resin, an epoxy diluent, nano-silicon dioxide and a curing agent are mixed and coated on the surface of the steel to obtain a high-cleanliness steel after curing. The steel prepared by the present application has low contents of C, P, S and N elements, high cleanliness and strong corrosion resistance of the surface coating.

Description

Technical Field

[0001] This invention relates to the field of steel manufacturing technology, specifically to a high-purity steel and its preparation method. Background Technology

[0002] Steel has irreplaceable applications in automobiles, construction, electrical appliances, shipbuilding, and surgical scalpels. With the continuous development of industrial technology, the requirements for steel performance are becoming increasingly stringent, making it crucial to improve steel's performance and extend its service life. On the one hand, to improve steel's performance, the content of elements such as C, P, S, and N in the steel during the smelting process all affect its properties. On the other hand, during long-term use, components in the surrounding environment, such as water vapor, inorganic salts, and acidic substances in the atmosphere, can cause varying degrees of corrosion to the steel. This not only affects its appearance but also, over time, leads to material performance degradation, affecting the normal operation of equipment and causing economic losses.

[0003] Based on the above problems, it is essential to provide a high-purity steel that reduces the content of elements such as C, P, S, and N during the steel smelting process, thereby improving the performance of the steel. At the same time, a corrosion-resistant coating is applied to the surface of the steel to improve its corrosion resistance and extend its service life. Summary of the Invention

[0004] The purpose of this invention is to provide a high-purity steel and its preparation method to solve the problems mentioned in the background art.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a high-purity steel and its preparation method, comprising the following steps:

[0006] Step 1: Desulfurize the molten iron, then remelt it in a converter, supply oxygen to form slag for dephosphorization and decarburization, and control the carbon content in the molten steel at the end of the remelting process to be 0.05-0.20%, resulting in low-phosphorus and low-nitrogen molten steel with a steel slag basicity of 4.5-6.0.

[0007] Step 2: Tap the low-phosphorus and low-nitrogen molten steel. During the tapping process, add silicon-manganese alloy and carbon raiser, and blow argon gas into the bottom of the ladle to obtain argon-blown alloyed molten steel.

[0008] Step 3: The argon-bonded molten steel is electrically heated through an LF furnace, and calcium carbide and activated quicklime are added to the molten steel for refining. Argon gas is blown from the bottom to obtain LF refined molten steel.

[0009] Step 4: The LF refined molten steel is introduced into the RH vacuum cycle and bottom-blown with argon gas to obtain the finished molten steel;

[0010] Step 5: The finished molten steel is poured and rolled under double argon protection to obtain cast steel parts. A fluorinated acrylate polymer modified epoxy resin coating is applied to the surface of the cast steel parts to form a coating with a thickness of 150-300μm. The coating is cured at 120-140℃ to obtain high-cleanliness steel.

[0011] Furthermore, in step 1, after desulfurization of the molten iron, the S mass content is 0.005-0.008%; in the low-phosphorus and low-nitrogen molten steel, the P mass content is 0.003-0.006% and the N mass content is 0.001-0.0015%.

[0012] Furthermore, in step 2, the tapping speed is controlled at 100–300 kg / s; the argon flow rate is 2.0–3.5 NL / (min·t).

[0013] Furthermore, in step 3, the refining time is 10-15 min; the argon flow rate is 0.5-1.5 NL / (min·t), the argon blowing time is 5-15 min; the amount of calcium carbide added is 0.02-0.03% of the total weight of molten steel, and the amount of activated quicklime added is 0.2-0.3% of the total weight of molten steel.

[0014] Furthermore, in step 4, the argon flow rate is 10–12 NL / (min·t), the vacuum circulation time is 15–25 min, and the circulation vacuum degree is 200–300 Pa.

[0015] Furthermore, in step 5, the content of each component in the fluorinated acrylate polymer modified epoxy resin coating, by weight, is: 100 parts fluorinated acrylate polymer modified epoxy resin, 6-8 parts epoxy diluent, 3-4 parts nano silica, and 10-25 parts curing agent.

[0016] Furthermore, the preparation method of the fluorinated acrylate polymer modified epoxy resin coating includes the following steps: first, the epoxy-modified fluorinated monomer is mixed with epoxy resin, heated to 80-90°C, and stirred to disperse the epoxy-modified fluorinated monomer. Then, a mixture of butyl acrylate, methyl methacrylate, and azobisisobutyronitrile is added dropwise while maintaining the temperature. The mixture is reacted for 7-10 hours, and unreacted monomers are removed under vacuum to obtain the fluorinated acrylate polymer modified epoxy resin.

[0017] Furthermore, the preparation method of epoxy-modified fluorinated monomers is as follows:

[0018] S1: Under nitrogen atmosphere, glycidyl ether is added to triphenylmethane triisocyanate, and the addition of glycidyl ether is controlled to be completed within 20-30 min. Using dibutyltin dilaurate as catalyst, the temperature is raised to 50-60℃ and reacted for 2-3 h to obtain diepoxy modified phenylmethane isocyanate; wherein, triphenylmethane triisocyanate and glycidyl ether react in a molar ratio of 1:2.

[0019] S2: Under nitrogen atmosphere, tetrafluorobutane glycol is heated to 85-90℃ and melted; 2-methyl-2-acrylate-2-isocyanate ethyl ester is mixed with a polymerization inhibitor and added to the molten tetrafluorobutane glycol; using dibutyltin dilaurate as a catalyst, the reaction is carried out for 1-2 hours to obtain a fluorinated monomer; wherein, tetrafluorobutane glycol and 2-methyl-2-acrylate-2-isocyanate ethyl ester are mixed in a molar ratio of 1:1, and the amount of polymerization inhibitor is 5‰ of the total weight of 2-methyl-2-acrylate-2-isocyanate ethyl ester;

[0020] S3: Under nitrogen atmosphere, diepoxy-modified phenylmethane isocyanate and fluorinated monomer are mixed at a molar ratio of isocyanate group to hydroxyl group of 1:1, and dibutyltin dilaurate is used as catalyst. The mixture is heated to 50-60℃ and reacted for 2-3 hours to obtain epoxy-modified fluorinated monomer.

[0021] Furthermore, the mass ratio of the epoxy-modified fluorinated monomer, butyl acrylate, and methyl methacrylate is (10-15):(60-65):(20-30).

[0022] Furthermore, in the fluorinated acrylate polymer-modified epoxy resin, the content of each component, by weight percentage, is 17-22% fluorinated acrylate polymer and 78-83% epoxy resin.

[0023] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: The present invention adopts the "converter-LF-RH-continuous casting" process for steelmaking, which is simple and improves the quality of steel by controlling the content of impurity elements C, N, P and S in the steel, producing steel with low total impurity element content and high cleanliness.

[0024] To further improve the corrosion resistance of steel, this invention coats the steel surface with a fluorinated acrylate polymer-modified epoxy resin, which, after curing, forms a corrosion-resistant coating. The fluorinated acrylate polymer-modified epoxy resin uses epoxy resin as a dispersion medium to polymerize epoxy-modified fluorinated monomers, butyl acrylate, and methyl methacrylate, thereby achieving modification. The epoxy-modified fluorinated monomer is obtained by further reacting triphenylmethane triisocyanate, glycidyl ether, tetrafluorobutanediol, and ethyl 2-methyl-2-acrylate-2-isocyanate. Specifically, triphenylmethane triisocyanate reacts with glycidyl ether at a molar ratio of 1:2 to obtain a diepoxy-modified phenylmethane isocyanate, retaining an unreacted isocyanate group in the molecule; tetrafluorobutanediol reacts with ethyl 2-methyl-2-acrylate-2-isocyanate at a molar ratio of 1:1 to obtain a fluorinated modified monomer, retaining an unreacted hydroxyl group in the molecule. The molecular structure of epoxy-modified fluorinated monomers contains a C=C group at one end, allowing them to participate in the copolymerization of soft and hard acrylate monomers. The other end contains an epoxy group, which on the one hand improves the compatibility between the acrylate polymer and the epoxy resin matrix; on the other hand, under the action of a curing agent, it effectively compensates for the defects generated during the curing process of single epoxy resin, improving the density and adhesion of the coating, thereby preventing corrosive media from penetrating into the coating and strengthening the coating's protective effect on the steel. Furthermore, conventional epoxy resins have a large number of hydroxyl groups on their surface, exhibiting a certain degree of hydrophilicity. Fluorinated acrylate polymers can reduce hydrophilicity, keeping the surface clean and effectively preventing water and corrosive components in the water from contacting the steel and causing corrosion. In addition, the amount of fluorinated acrylate polymer should be controlled to 17-22% of the total weight of the fluorinated acrylate polymer-modified epoxy resin. Too low a dosage will result in suboptimal modification, while too high a dosage will cause macroscopic phase separation between the polymer and the epoxy resin, affecting the modification effect. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] The materials used in this invention and their sources are as follows: the polymerization inhibitor is polymerization inhibitor 701, from Shanghai Aladdin Biochemical Technology Co., Ltd.; the carbon raiser and silicon-manganese alloy are both from Anyang Jinsheng Metallurgical Materials Co., Ltd.; the carbon raiser is graphite particle carbon raiser with a particle size of 1-5mm; the silicon-manganese alloy is grade 6014; the calcium carbide is from Inner Mongolia Baiyanhu Chemical Co., Ltd., a superior grade; the activated quicklime is from Hunan Bicheng Technology Co., Ltd., with a calcium oxide content of 80-96%; the epoxy diluent is from Anhui Xinyuan Technology Co., Ltd., grade XY630; the nano silica is from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd., grade XFI03; the epoxy resin is epoxy resin E-51, and the curing agent is T-31, both from Wuxi Pinhua Chemical Co., Ltd.

[0027] Example 1: A high-purity steel and its preparation method, comprising the following steps:

[0028] Step 1: Desulfurize the molten iron to a sulfur content of 0.005% by mass, then remelt it in a converter, supplying oxygen to form slag for dephosphorization and decarburization. Control the carbon content in the molten steel at the end of the remelting process to 0.20% by mass, resulting in low-phosphorus, low-nitrogen molten steel with a slag basicity of 4.5. The low-phosphorus, low-nitrogen molten steel contains 0.003% phosphorus and 0.001% nitrogen by mass.

[0029] Step 2: Tap the low-phosphorus and low-nitrogen molten steel at a tapping speed of 100 kg / s. Add silicon-manganese alloy and carbon raiser during the tapping process. Blow argon gas into the ladle at a flow rate of 2.0 NL / (min·t) to obtain argon-blown alloyed molten steel.

[0030] Step 3: The argon-bonded alloyed steel is electrically heated in an LF furnace, and calcium carbide and activated quicklime are added to the steel for refining for 15 minutes. Argon gas is then blown from the bottom at a flow rate of 0.5 NL / (min·t) for 5 minutes to obtain LF-refined steel. The amount of calcium carbide added is 0.02% of the total weight of the steel, and the amount of activated quicklime added is 0.2% of the total weight of the steel.

[0031] Step 4: The LF refined molten steel is introduced into the RH vacuum circulation, and argon is blown from the bottom to obtain the finished molten steel; the argon flow rate is 10 NL / (min·t), the vacuum circulation time is 15 min, and the circulation vacuum degree is 200 Pa;

[0032] Step 5: The finished molten steel is poured and rolled under double argon protection to obtain a cast steel part. A fluorinated acrylate polymer-modified epoxy resin coating is applied to the surface of the cast steel part to form a coating with a thickness of 300 μm. The coating is then cured at 120℃ to obtain high-purity steel. The fluorinated acrylate polymer-modified epoxy resin coating comprises 100g of fluorinated acrylate polymer-modified epoxy resin, 8g of epoxy diluent, 4g of nano-silica, and 16g of curing agent. The preparation method of the fluorinated acrylate polymer-modified epoxy resin includes the following steps:

[0033] S1: Under nitrogen atmosphere, 2 mol of glycidyl ether was added to 1 mol of triphenylmethane triisocyanate. The glycidyl ether was added within 20 min. Dibutyltin dilaurate was used as catalyst. The temperature was raised to 50℃ and reacted for 2 h to obtain diepoxy modified phenylmethane isocyanate.

[0034] S2: Under nitrogen atmosphere, 1 mol of tetrafluorobutanediol was heated to 85℃ and melted; 1 mol of 2-methyl-2-acrylate-2-isocyanate ethyl ester was mixed with a polymerization inhibitor (the amount of polymerization inhibitor was 5‰ of the total weight of 2-methyl-2-acrylate-2-isocyanate ethyl ester), and added to the molten tetrafluorobutanediol. Using dibutyltin dilaurate as a catalyst, the reaction was carried out for 1 hour to obtain the fluorine-modified monomer.

[0035] S3: Under nitrogen atmosphere, diepoxy-modified phenylmethane isocyanate and fluorinated monomer are mixed at a molar ratio of isocyanate group to hydroxyl group of 1:1, and dibutyltin dilaurate is used as catalyst. The mixture is heated to 50°C and reacted for 2 hours to obtain epoxy-modified fluorinated monomer.

[0036] S4: Mix epoxy-modified fluorinated monomers with epoxy resin, heat to 80℃, stir to disperse the epoxy-modified fluorinated monomers, and then add a mixture of butyl acrylate and methyl methacrylate dropwise while maintaining the temperature. Use azobisisobutyronitrile as an initiator and react for 7 hours. Remove unreacted monomers under vacuum to obtain fluorinated acrylate polymer-modified epoxy resin. The mass ratio of epoxy-modified fluorinated monomers, butyl acrylate, and methyl methacrylate is 10:60:30. The content of each component in the fluorinated acrylate polymer-modified epoxy resin, by weight percentage, is 17% fluorinated acrylate polymer and 83% epoxy resin.

[0037] Example 2: A high-purity steel and its preparation method, comprising the following steps:

[0038] Step 1: Desulfurize the molten iron to a sulfur content of 0.007% by mass, then remelt it in a converter, supplying oxygen to form slag for dephosphorization and decarburization. Control the carbon content in the molten steel at the end of the remelting process to 0.20% by mass, resulting in low-phosphorus, low-nitrogen steel with a slag basicity of 5. The low-phosphorus, low-nitrogen steel contains 0.005% phosphorus and 0.0012% nitrogen by mass.

[0039] Step 2: Tap the low-phosphorus and low-nitrogen molten steel at a tapping speed of 200 kg / s. Add silicon-manganese alloy and carbon raiser during the tapping process. Blow argon gas into the ladle at a flow rate of 3 NL / (min·t) to obtain argon-alloyed molten steel.

[0040] Step 3: The argon-bonded alloyed steel is electrically heated through an LF furnace, and calcium carbide and activated quicklime are added to the steel for refining for 18 minutes. Argon gas is blown from the bottom at a flow rate of 1 NL / (min·t) for 10 minutes to obtain LF-refined steel. The amount of calcium carbide added is 0.028% of the total weight of the steel, and the amount of activated quicklime added is 0.25% of the total weight of the steel.

[0041] Step 4: The LF refined molten steel is introduced into the RH vacuum circulation, and argon is blown from the bottom to obtain the finished molten steel; the argon flow rate is 11NL / (min·t), the vacuum circulation time is 20min, and the circulation vacuum degree is 240Pa;

[0042] Step 5: The finished molten steel is poured and rolled under double argon protection to obtain a cast steel part. A fluorinated acrylate polymer-modified epoxy resin coating is applied to the surface of the cast steel part to form a coating with a thickness of 300 μm. The coating is then cured at 130℃ to obtain high-purity steel. The fluorinated acrylate polymer-modified epoxy resin coating comprises 100g of fluorinated acrylate polymer-modified epoxy resin, 8g of epoxy diluent, 4g of nano-silica, and 16g of curing agent. The preparation method of the fluorinated acrylate polymer-modified epoxy resin includes the following steps:

[0043] S1: Under nitrogen atmosphere, 2 mol of glycidyl ether was added to 1 mol of triphenylmethane triisocyanate, and the glycidyl ether was added within 25 min. Dibutyltin dilaurate was used as catalyst, and the temperature was raised to 55℃ for 2.5 h to obtain diepoxy modified phenylmethane isocyanate.

[0044] S2: Under nitrogen atmosphere, 1 mol of tetrafluorobutanediol was heated to 88℃ and melted; 1 mol of 2-methyl-2-acrylate-2-isocyanate ethyl ester was mixed with a polymerization inhibitor (the amount of polymerization inhibitor was 5‰ of the total weight of 2-methyl-2-acrylate-2-isocyanate ethyl ester), and added to the molten tetrafluorobutanediol. Using dibutyltin dilaurate as a catalyst, the reaction was carried out for 1.5 h to obtain the fluorine-modified monomer;

[0045] S3: Under nitrogen atmosphere, diepoxy-modified phenylmethane isocyanate and fluorinated monomer are mixed at a molar ratio of isocyanate group to hydroxyl group of 1:1, and dibutyltin dilaurate is used as catalyst. The mixture is heated to 55℃ and reacted for 2.5h to obtain epoxy-modified fluorinated monomer.

[0046] S4: Mix epoxy-modified fluorinated monomers with epoxy resin, heat to 85℃, stir to disperse the epoxy-modified fluorinated monomers, and then add a mixture of butyl acrylate and methyl methacrylate dropwise while maintaining the temperature. Use azobisisobutyronitrile as an initiator and react for 8.5 hours. Remove unreacted monomers under vacuum to obtain fluorinated acrylate polymer-modified epoxy resin. The mass ratio of epoxy-modified fluorinated monomers, butyl acrylate, and methyl methacrylate is 10:60:30. The content of each component in the fluorinated acrylate polymer-modified epoxy resin, by weight percentage, is 20% fluorinated acrylate polymer and 80% epoxy resin.

[0047] Example 3: A high-purity steel and its preparation method, comprising the following steps:

[0048] Step 1: Desulfurize the molten iron to a sulfur content of 0.008% by mass, then remelt it in a converter, supplying oxygen to form slag for dephosphorization and decarburization. Control the carbon content in the molten steel at the end of the remelting process to 0.20% by mass, resulting in low-phosphorus, low-nitrogen molten steel with a slag basicity of 6.0. The low-phosphorus, low-nitrogen molten steel contains 0.006% phosphorus and 0.0015% nitrogen by mass.

[0049] Step 2: Tap the low-phosphorus and low-nitrogen molten steel at a tapping speed of 300 kg / s. Add silicon-manganese alloy and carbon raiser during the tapping process. Blow argon gas into the ladle at a flow rate of 3.5 NL / (min·t) to obtain argon-alloyed molten steel.

[0050] Step 3: The argon-bonded alloyed steel is electrically heated in an LF furnace, and calcium carbide and activated quicklime are added to the steel for refining for 20 minutes. Argon gas is then blown from the bottom at a flow rate of 1.5 NL / (min·t) for 15 minutes to obtain LF-refined steel. The amount of calcium carbide added is 0.03% of the total weight of the steel, and the amount of activated quicklime added is 0.3% of the total weight of the steel.

[0051] Step 4: The LF refined molten steel is introduced into the RH vacuum circulation, and argon is blown from the bottom to obtain the finished molten steel; the argon flow rate is 12NL / (min·t), the vacuum circulation time is 25min, and the circulation vacuum degree is 300Pa;

[0052] Step 5: The finished molten steel is poured and rolled under double argon protection to obtain a cast steel part. A fluorinated acrylate polymer-modified epoxy resin coating is applied to the surface of the cast steel part to form a coating with a thickness of 300 μm. The coating is then cured at 140℃ to obtain high-purity steel. The fluorinated acrylate polymer-modified epoxy resin coating comprises 100g of fluorinated acrylate polymer-modified epoxy resin, 8g of epoxy diluent, 4g of nano-silica, and 16g of curing agent. The preparation method of the fluorinated acrylate polymer-modified epoxy resin includes the following steps:

[0053] S1: Under nitrogen atmosphere, 2 mol of glycidyl ether was added to 1 mol of triphenylmethane triisocyanate, and the glycidyl ether was added within 30 min. Dibutyltin dilaurate was used as catalyst, and the temperature was raised to 60℃ for 3 h to obtain diepoxy modified phenylmethane isocyanate.

[0054] S2: Under nitrogen atmosphere, 1 mol of tetrafluorobutanediol was heated to 90℃ and melted; 1 mol of 2-methyl-2-acrylate-2-isocyanate ethyl ester was mixed with a polymerization inhibitor (the amount of polymerization inhibitor was 5‰ of the total weight of 2-methyl-2-acrylate-2-isocyanate ethyl ester), and added to the molten tetrafluorobutanediol. Using dibutyltin dilaurate as a catalyst, the reaction was carried out for 2 hours to obtain the fluorine-modified monomer;

[0055] S3: Under nitrogen atmosphere, diepoxy-modified phenylmethane isocyanate and fluorinated monomer are mixed at a molar ratio of isocyanate group to hydroxyl group of 1:1, and dibutyltin dilaurate is used as catalyst. The mixture is heated to 60℃ and reacted for 3h to obtain epoxy-modified fluorinated monomer.

[0056] S4: Mix epoxy-modified fluorinated monomers with epoxy resin, heat to 90℃, stir to disperse the epoxy-modified fluorinated monomers, and then add a mixture of butyl acrylate and methyl methacrylate dropwise while maintaining the temperature. Use azobisisobutyronitrile as an initiator and react for 10 hours. Remove unreacted monomers under vacuum to obtain fluorinated acrylate polymer-modified epoxy resin. The mass ratio of epoxy-modified fluorinated monomers, butyl acrylate, and methyl methacrylate is 10:60:30. The content of each component in the fluorinated acrylate polymer-modified epoxy resin, by weight percentage, is 22% fluorinated acrylate polymer and 78% epoxy resin.

[0057] Comparative Example 1: No fluorinated acrylate polymer was used to modify the epoxy resin, and all other parameters were the same as in Example 1.

[0058] Step 1: Desulfurize the molten iron to a sulfur content of 0.005% by mass, then remelt it in a converter, supplying oxygen to form slag for dephosphorization and decarburization. Control the carbon content in the molten steel at the end of the remelting process to 0.20% by mass, resulting in low-phosphorus, low-nitrogen molten steel with a slag basicity of 4.5. The low-phosphorus, low-nitrogen molten steel contains 0.003% phosphorus and 0.001% nitrogen by mass.

[0059] Step 2: Tap the low-phosphorus and low-nitrogen molten steel at a tapping speed of 100 kg / s. Add silicon-manganese alloy and carbon raiser during the tapping process. Blow argon gas into the ladle at a flow rate of 2.0 NL / (min·t) to obtain argon-blown alloyed molten steel.

[0060] Step 3: The argon-bonded alloyed steel is electrically heated in an LF furnace, and calcium carbide and activated quicklime are added to the steel for refining for 15 minutes. Argon gas is then blown from the bottom at a flow rate of 0.5 NL / (min·t) for 5 minutes to obtain LF-refined steel. The amount of calcium carbide added is 0.02% of the total weight of the steel, and the amount of activated quicklime added is 0.2% of the total weight of the steel.

[0061] Step 4: The LF refined molten steel is introduced into the RH vacuum circulation, and argon is blown from the bottom to obtain the finished molten steel; the argon flow rate is 10 NL / (min·t), the vacuum circulation time is 15 min, and the circulation vacuum degree is 200 Pa;

[0062] Step 5: The finished molten steel is poured and rolled under double argon protection to obtain cast steel parts. An epoxy resin coating with a thickness of 300μm is applied to the surface of the cast steel parts. The coating is then cured at 120℃ to obtain high-purity steel. The epoxy resin coating contains 100g of fluorinated acrylate polymer modified epoxy resin, 8g of epoxy diluent, 4g of nano silica, and 16g of curing agent.

[0063] Comparative Example 2: No epoxy-modified fluorinated monomer was added, and the other parameters were the same as in Example 2.

[0064] Step 1: Desulfurize the molten iron to a sulfur content of 0.007% by mass, then remelt it in a converter, supplying oxygen to form slag for dephosphorization and decarburization. Control the carbon content in the molten steel at the end of the remelting process to 0.20% by mass, resulting in low-phosphorus, low-nitrogen steel with a slag basicity of 5. The low-phosphorus, low-nitrogen steel contains 0.005% phosphorus and 0.0012% nitrogen by mass.

[0065] Step 2: Tap the low-phosphorus and low-nitrogen molten steel at a tapping speed of 200 kg / s. Add silicon-manganese alloy and carbon raiser during the tapping process. Blow argon gas into the ladle at a flow rate of 3 NL / (min·t) to obtain argon-alloyed molten steel.

[0066] Step 3: The argon-bonded alloyed steel is electrically heated through an LF furnace, and calcium carbide and activated quicklime are added to the steel for refining for 18 minutes. Argon gas is blown from the bottom at a flow rate of 1 NL / (min·t) for 10 minutes to obtain LF-refined steel. The amount of calcium carbide added is 0.028% of the total weight of the steel, and the amount of activated quicklime added is 0.25% of the total weight of the steel.

[0067] Step 4: The LF refined molten steel is introduced into the RH vacuum circulation, and argon is blown from the bottom to obtain the finished molten steel; the argon flow rate is 11NL / (min·t), the vacuum circulation time is 20min, and the circulation vacuum degree is 240Pa;

[0068] Step 5: The finished molten steel is poured and rolled under double argon protection to obtain a cast steel part. A fluorinated acrylate polymer-modified epoxy resin coating is applied to the surface of the cast steel part to form a coating with a thickness of 300 μm. The coating is then cured at 130℃ to obtain high-purity steel. The fluorinated acrylate polymer-modified epoxy resin coating comprises 100g of fluorinated acrylate polymer-modified epoxy resin, 8g of epoxy diluent, 4g of nano-silica, and 16g of curing agent. The preparation method of the fluorinated acrylate polymer-modified epoxy resin includes the following steps:

[0069] The epoxy resin was heated to 85°C, and a mixture of butyl acrylate and methyl methacrylate was added dropwise while maintaining the temperature. Azobisisobutyronitrile (AIBN) was used as an initiator, and the reaction was carried out for 8.5 hours. Unreacted monomers were removed under vacuum to obtain acrylate polymer-modified epoxy resin. The mass ratio of butyl acrylate to methyl methacrylate was 60:30. The content of each component in the acrylate polymer-modified epoxy resin, by weight percentage, was 20% acrylate polymer and 80% epoxy resin.

[0070] Comparative Example 3: The content of fluorinated acrylate polymer was increased, and the other parameters were the same as in Example 3.

[0071] Step 1: Desulfurize the molten iron to a sulfur content of 0.008% by mass, then remelt it in a converter, supplying oxygen to form slag for dephosphorization and decarburization. Control the carbon content in the molten steel at the end of the remelting process to 0.20% by mass, resulting in low-phosphorus, low-nitrogen molten steel with a slag basicity of 6.0. The low-phosphorus, low-nitrogen molten steel contains 0.006% phosphorus and 0.0015% nitrogen by mass.

[0072] Step 2: Tap the low-phosphorus and low-nitrogen molten steel at a tapping speed of 300 kg / s. Add silicon-manganese alloy and carbon raiser during the tapping process. Blow argon gas into the ladle at a flow rate of 3.5 NL / (min·t) to obtain argon-alloyed molten steel.

[0073] Step 3: The argon-bonded alloyed steel is electrically heated in an LF furnace, and calcium carbide and activated quicklime are added to the steel for refining for 20 minutes. Argon gas is then blown from the bottom at a flow rate of 1.5 NL / (min·t) for 15 minutes to obtain LF-refined steel. The amount of calcium carbide added is 0.03% of the total weight of the steel, and the amount of activated quicklime added is 0.3% of the total weight of the steel.

[0074] Step 4: The LF refined molten steel is introduced into the RH vacuum circulation, and argon is blown from the bottom to obtain the finished molten steel; the argon flow rate is 12NL / (min·t), the vacuum circulation time is 25min, and the circulation vacuum degree is 300Pa;

[0075] Step 5: The finished molten steel is poured and rolled under double argon protection to obtain a cast steel part. A fluorinated acrylate polymer-modified epoxy resin coating is applied to the surface of the cast steel part to form a coating with a thickness of 300 μm. The coating is then cured at 140℃ to obtain high-purity steel. The fluorinated acrylate polymer-modified epoxy resin coating comprises 100g of fluorinated acrylate polymer-modified epoxy resin, 8g of epoxy diluent, 4g of nano-silica, and 16g of curing agent. The preparation method of the fluorinated acrylate polymer-modified epoxy resin includes the following steps:

[0076] S1: Under nitrogen atmosphere, 2 mol of glycidyl ether was added to 1 mol of triphenylmethane triisocyanate, and the glycidyl ether was added within 30 min. Dibutyltin dilaurate was used as catalyst, and the temperature was raised to 60℃ for 3 h to obtain diepoxy modified phenylmethane isocyanate.

[0077] S2: Under nitrogen atmosphere, 1 mol of tetrafluorobutanediol was heated to 90℃ and melted; 1 mol of 2-methyl-2-acrylate-2-isocyanate ethyl ester was mixed with a polymerization inhibitor (the amount of polymerization inhibitor was 5‰ of the total weight of 2-methyl-2-acrylate-2-isocyanate ethyl ester), and added to the molten tetrafluorobutanediol. Using dibutyltin dilaurate as a catalyst, the reaction was carried out for 2 hours to obtain the fluorine-modified monomer;

[0078] S3: Under nitrogen atmosphere, diepoxy-modified phenylmethane isocyanate and fluorinated monomer are mixed at a molar ratio of isocyanate group to hydroxyl group of 1:1, and dibutyltin dilaurate is used as catalyst. The mixture is heated to 60℃ and reacted for 3h to obtain epoxy-modified fluorinated monomer.

[0079] S4: Mix epoxy-modified fluorinated monomers with epoxy resin, heat to 90℃, stir to disperse the epoxy-modified fluorinated monomers, and then add a mixture of butyl acrylate and methyl methacrylate dropwise while maintaining the temperature. Use azobisisobutyronitrile as an initiator and react for 10 hours. Remove unreacted monomers under vacuum to obtain fluorinated acrylate polymer-modified epoxy resin. The mass ratio of epoxy-modified fluorinated monomers, butyl acrylate, and methyl methacrylate is 10:60:30. The content of each component in the fluorinated acrylate polymer-modified epoxy resin, by weight percentage, is 35% fluorinated acrylate polymer and 65% epoxy resin.

[0080] experiment:

[0081] The contents of C, P, S and N elements in the finished steel products of Examples 1 to 3 were determined, and the experimental results are shown in Table 1.

[0082] Table 1:

[0083] project C P S N Example 1 0.73％ 0.0068％ 0.0038％ 0.0027％ Example 2 0.72％ 0.0067％ 0.0036％ 0.0025％ Example 3 0.70％ 0.0064％ 0.0035％ 0.0022％

[0084] The high-cleanliness steels prepared in Examples 1-3 and Comparative Examples 1-3 were tested. Neutral salt spray tests were conducted according to GB / T 10125-2021 "Artificial Atmosphere Corrosion Test - Salt Spray Test" and GB / T 1771-2007 "Determination of Neutral Salt Spray Resistance of Paints and Varnishes". The chamber temperature was (35±1)℃, and the corrosive medium was a 5% NaCl aqueous solution. The adhesion and appearance morphology of the coatings were tested before and after the 3000h salt spray test. The adhesion test method was based on GB / T5210-2006 "Paints and Varnishes - Pull-Off Adhesion Test". The adhesion between the coating and the metal substrate was tested using a fully automatic digital display pull-off adhesion tester, and the results are shown in Table 2.

[0085] Table 2

[0086]

[0087] Conclusion: The data in Table 1 show that the main impurity elements C, S, P, and N in the molten steel of Examples 1-3 are low, and the prepared steel has high cleanliness. Table 2 shows that the high-cleanliness steel prepared by this invention has good corrosion resistance, and the apparent properties of the coating show little change compared to Comparative Examples 1-3. Data from Example 1 and Comparative Example 1 show that, compared with a single epoxy resin coating, the fluorinated acrylate polymer-modified epoxy resin coating has stronger corrosion resistance. Data from Example 2 and Comparative Example 2 show that the epoxy groups in the epoxy-modified fluorinated monomer can effectively improve the compatibility between epoxy resin and acrylate polymer, and fluorine can improve the corrosion resistance of the coating, enhance the protective effect of the coating on steel, and thus slow down the corrosion of steel. Data from Example 3 and Comparative Example 3 show that, increasing the amount of fluorinated acrylate polymer has two effects: firstly, because fluorine has a low surface energy, more fluorine will migrate to the interface, which will reduce the adhesion of the coating; secondly, the compatibility between the fluorinated acrylate polymer and epoxy resin deteriorates with higher content, resulting in observable bubbling after long-term salt spray testing, because the two undergo macroscopic phase separation.

[0088] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing high-purity steel, characterized in that: Includes the following steps: Step 1: Desulfurize the molten iron, then remelt it in a converter, supply oxygen to form slag for dephosphorization and decarburization, and remove carbon to control the carbon content in the molten steel at the end of the remelting process to be 0.05~0.20%, resulting in low-phosphorus and low-nitrogen molten steel with a steel slag basicity of 4.5~6.0; Step 2: Tap the low-phosphorus and low-nitrogen molten steel. During the tapping process, add silicon-manganese alloy and carbon raiser, and blow argon gas into the bottom of the ladle to obtain argon-blown alloyed molten steel. Step 3: The argon-bonded molten steel is electrically heated through an LF furnace, and calcium carbide and activated quicklime are added to the molten steel for refining. Argon gas is blown from the bottom to obtain LF refined molten steel. Step 4: The LF refined molten steel is introduced into the RH vacuum cycle and bottom-blown with argon gas to obtain the finished molten steel; Step 5: The finished molten steel is poured and rolled under double argon protection to obtain cast steel parts. A fluorinated acrylate polymer modified epoxy resin coating is applied to the surface of the cast steel parts to form a coating with a thickness of 150~300μm. High-purity steel is obtained by curing at 120~140℃; In step 5, the content of each component in the fluorinated acrylate polymer modified epoxy resin coating, by weight, is 100 parts of fluorinated acrylate polymer modified epoxy resin, 6-8 parts of epoxy diluent, 3-4 parts of nano silica, and 10-25 parts of curing agent. The preparation method of the fluorinated acrylate polymer modified epoxy resin coating includes the following steps: mixing epoxy-modified fluorinated monomers with epoxy resin, heating to 80~90℃, stirring to disperse the epoxy-modified fluorinated monomers, then adding a mixture of butyl acrylate, methyl methacrylate and azobisisobutyronitrile dropwise while keeping warm, reacting for 7~10h, and removing unreacted monomers under vacuum to obtain fluorinated acrylate polymer modified epoxy resin; The preparation method of the epoxy-modified fluorinated monomer is as follows: S1: Under nitrogen atmosphere, glycidyl ether is added to triphenylmethane triisocyanate, and the addition of glycidyl ether is controlled to be completed within 20-30 min. Using dibutyltin dilaurate as catalyst, the temperature is raised to 50-60℃ and reacted for 2-3 h to obtain diepoxy modified phenylmethane isocyanate; wherein, triphenylmethane triisocyanate and glycidyl ether react in a molar ratio of 1:

2. S2: Under nitrogen atmosphere, tetrafluorobutane glycol is heated to 85-90℃ and melted; 2-methyl-2-acrylate-2-isocyanate ethyl ester is mixed with a polymerization inhibitor and added to the molten tetrafluorobutane glycol; using dibutyltin dilaurate as a catalyst, the reaction is carried out for 1-2 hours to obtain a fluorinated monomer; wherein, tetrafluorobutane glycol and 2-methyl-2-acrylate-2-isocyanate ethyl ester are mixed in a molar ratio of 1:1, and the amount of polymerization inhibitor is 5‰ of the total weight of 2-methyl-2-acrylate-2-isocyanate ethyl ester; S3: Under nitrogen atmosphere, diepoxy-modified phenylmethane isocyanate and fluorinated monomer are mixed at a molar ratio of isocyanate group to hydroxyl group of 1:1, and dibutyltin dilaurate is used as catalyst. The mixture is heated to 50~60℃ and reacted for 2~3h to obtain epoxy-modified fluorinated monomer.

2. The method for preparing high-purity steel according to claim 1, characterized in that: In step 1, after desulfurization of the molten iron, the S mass content is 0.005~0.008%; in the low-phosphorus and low-nitrogen molten steel, the P mass content is 0.003~0.006% and the N mass content is 0.001~0.0015%.

3. The method for preparing high-purity steel according to claim 1, characterized in that: In step 2, the tapping speed is controlled at 100~300 kg / s; the argon flow rate is 2.0~3.5 NL / (min·t).

4. The method for preparing high-purity steel according to claim 1, characterized in that: In step 3, the refining time is 10-15 min; the argon flow rate is 0.5-1.5 NL / (min·t), the argon blowing time is 5-15 min; the amount of calcium carbide added is 0.02-0.03% of the total weight of molten steel, and the amount of active quicklime added is 0.2-0.3% of the total weight of molten steel.

5. The method for preparing high-purity steel according to claim 1, characterized in that: In step 4, the argon flow rate is 10~12 NL / (min·t), the vacuum circulation time is 15~25 min, and the circulation vacuum degree is 200~300 Pa.

6. The method for preparing high-purity steel according to claim 1, characterized in that: The mass ratio of epoxy-modified fluorinated monomer, butyl acrylate, and methyl methacrylate is (10~15):(60~65):(20~30); in the epoxy resin modified with fluorinated acrylate polymer, the content of each component, by weight percentage, is 17~22% fluorinated acrylate polymer and 78~83% epoxy resin.

7. The high-purity steel prepared by the method for preparing high-purity steel according to any one of claims 1 to 6.

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