High-cleanliness steel and preparation method thereof

Abstract

The invention relates to the field of steel preparation, in particular to high-cleanliness steel and a preparation method thereof. The method comprises the following steps: firstly, carrying out steelmaking by adopting a converter-LF-RH-continuous casting process flow; then, the reaction product of triphenylmethane triisocyanate and glycidyl is further reacted with the reaction product of tetrafluorobutanediol and 2-methyl-2-acrylic acid-2-isocyanate ethyl ester, and an epoxy group modified fluorine-containing monomer is obtained; then dispersing the epoxy group modified fluorine-containing monomer in epoxy resin, adding butyl acrylate and methyl methacrylate, and polymerizing to obtain fluorine-containing acrylate polymer modified epoxy resin; and finally, mixing the fluorine-containing acrylate polymer modified epoxy resin, an epoxy diluent, nano silicon dioxide and a curing agent, coating the surface of the steel with the mixture, and curing to obtain the high-cleanliness steel. The steel prepared through the method is low in C, P, S and N element content and high in cleanliness, and the corrosion resistance of a surface coating is high.

Description

Technical Field

[0001] The invention relates to the technical field of steel manufacturing, in particular to a high-cleanliness steel and a preparation method thereof. Background Art

[0002] Steel has irreplaceable applications in the fields of automobiles, construction, electrical appliances, ships, and surgical scalpels. With the continuous development of industrial technology, the requirements for steel performance are becoming increasingly stringent. It is particularly important to improve the performance of steel and extend its service life. On the one hand, in order to improve the performance of steel, during the smelting process, the content of elements such as C, P, S, and N in steel will affect the performance of steel; on the other hand, during the long-term use of steel, the surrounding environment such as water vapor, inorganic salts, acidic substances and other components in the atmosphere will cause varying degrees of corrosion to the steel, which will not only affect the appearance, but also cause long-term damage to the performance of the material, affect the normal operation of the equipment, and cause economic losses.

[0003] Based on the above problems, it is very necessary to provide a high-cleanliness steel, reduce the content of elements such as C, P, S, and N during the steel smelting process, and improve the performance of the steel; at the same time, use a corrosion-resistant coating to coat the steel surface to improve the corrosion resistance of the steel and extend its service life. Summary of the invention

[0004] The object of the present invention is to provide a high-cleanliness steel material and a preparation method thereof to solve the problems raised in the above-mentioned background technology.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions: a high-cleanliness steel material and a preparation method thereof, comprising the following steps:

[0006] Step 1: desulfurize the molten iron, then perform converter blowing, supply oxygen for slagging, dephosphorize and decarburize, and pull carbon to control the C mass content of the molten steel at the end of blowing to be 0.05-0.20%, and obtain low-phosphorus and low-nitrogen molten steel with slag basicity of 4.5-6.0;

[0007] Step 2: tapping the low-phosphorus and low-nitrogen molten steel, adding silicon-manganese alloy and carburizer during the tapping process, blowing argon gas from the bottom of the ladle to obtain argon-blown alloyed molten steel;

[0008] Step 3: electrically heating the argon-blown alloyed molten steel through an LF furnace, adding calcium carbide and activated lime into the molten steel for refining, and bottom blowing argon to obtain LF refined molten steel;

[0009] Step 4: The LF refined molten steel enters the RH vacuum cycle and argon is blown from the bottom to obtain finished molten steel;

[0010] Step 5: The finished molten steel is cast and rolled under double argon protection to obtain a steel casting, and a fluorinated acrylate polymer modified epoxy resin coating is coated on the surface of the steel casting to form a coating with a thickness of 150 to 300 μm; and the coating is cured at 120 to 140° C. to obtain a 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 steel tapping speed is controlled to be 100-300 kg / s; and the argon gas flow rate is controlled to be 2.0-3.5 NL / (min·t).

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

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

[0015] Furthermore, in step 5, the contents of the components in the fluorinated acrylate polymer modified epoxy resin coating are, by weight, 100 parts of fluorinated acrylate polymer modified epoxy resin, 6 to 8 parts of epoxy diluent, 3 to 4 parts of nano-silicon dioxide, and 10 to 25 parts of curing agent.

[0016] Furthermore, the preparation method of the fluorine-containing acrylate polymer modified epoxy resin coating includes the following steps: firstly mixing the epoxy-modified fluorine-containing monomer and the epoxy resin, heating to 80-90° C., stirring to disperse the epoxy-modified fluorine-containing monomer, adding dropwise a mixture of butyl acrylate, methyl methacrylate and azobisisobutyronitrile while keeping warm, reacting for 7-10 hours, and removing unreacted monomers in vacuo to obtain the fluorine-containing acrylate polymer modified epoxy resin.

[0017] Further, the preparation method of the epoxy-modified fluorinated monomer is:

[0018] S1: under nitrogen environment, add glycidol to triphenylmethane triisocyanate, control the glycidol to be added within 20-30 minutes, use dibutyltin dilaurate as a catalyst, heat to 50-60°C for reaction for 2-3 hours, and obtain diepoxy-modified phenylmethane isocyanate; wherein triphenylmethane triisocyanate and glycidol react in a molar ratio of 1:2;

[0019] S2: Under a nitrogen environment, tetrafluorobutanediol is taken and heated to 85-90°C for melting; 2-methyl-2-acrylic acid-2-isocyanate ethyl is mixed with an inhibitor, and then added to the molten tetrafluorobutanediol, and dibutyltin dilaurate is used as a catalyst to react for 1-2 hours to obtain a fluorine-modified monomer; wherein tetrafluorobutanediol and 2-methyl-2-acrylic acid-2-isocyanate ethyl are mixed in a molar ratio of 1:1, and the amount of the inhibitor is 5‰ of the total weight of 2-methyl-2-acrylic acid-2-isocyanate ethyl;

[0020] S3: In a nitrogen environment, diepoxy-modified phenylmethane isocyanate and fluorine-modified monomer are mixed in a molar ratio of isocyanate group to hydroxyl group of 1:1, dibutyltin dilaurate is used as a catalyst, the temperature is raised to 50-60°C and the reaction is carried out for 2-3 hours to obtain epoxy-modified fluorine-containing 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 fluorine-containing acrylate polymer modified epoxy resin, the contents of the components, by weight percentage, are 17-22% of the fluorine-containing acrylate polymer and 78-83% of the 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 flow for steelmaking, the process is simple, and by controlling the contents of impurity elements C, N, P, and S in the steel, finished steel with low total impurity element content and high cleanliness is produced, thereby improving the quality of the steel.

[0024] In order to further improve the corrosion resistance of steel, the present invention coats a fluorinated acrylate polymer modified epoxy resin on the surface of the steel, and forms a corrosion-resistant coating after curing. The fluorinated acrylate polymer modified epoxy resin uses epoxy resin as a dispersion medium, and polymerizes epoxy-modified fluorinated monomers, butyl acrylate, and methyl methacrylate to achieve modification. The epoxy-modified fluorinated monomer is obtained by further reacting the reaction product of triphenylmethane triisocyanate and glycidol with tetrafluorobutanediol and 2-methyl-2-acrylic acid-2-isocyanatoethyl ester, wherein triphenylmethane triisocyanate reacts with glycidol in a molar ratio of 1:2 to obtain a diepoxy-modified phenylmethane isocyanate, and retains an unreacted isocyanate group in the molecule; tetrafluorobutanediol reacts with 2-methyl-2-acrylic acid-2-isocyanatoethyl ester in a molar ratio of 1:1 to obtain a fluorinated modified monomer, and retains an unreacted hydroxyl group in the molecule. The molecular structure of the epoxy-modified fluorine-containing monomer contains C=C at one end, which can participate in the copolymerization of acrylate soft and hard monomers, and contains an epoxy group at the other end. On the one hand, it can improve the compatibility of the acrylate polymer with the epoxy resin matrix. On the other hand, under the action of the curing agent, it effectively makes up for the defects of the single epoxy resin during the curing process, improves the compactness and adhesion of the coating, thereby preventing the corrosive medium from penetrating into the interior of the coating and strengthening the protective effect of the coating on the steel. In addition, there are a large number of hydroxyl groups on the surface of conventional epoxy resins, which have a certain hydrophilicity, while the fluorine-containing acrylate polymer can reduce the hydrophilicity, keep the surface clean, and effectively isolate water and corrosive components in the water from contacting with steel to cause steel to be corroded. In addition, the amount of fluorine-containing acrylate polymer needs to be controlled at 17-22% of the total weight of the fluorine-containing acrylate polymer modified epoxy resin. If the amount is too low, it will make it difficult to achieve the best modification effect, while if the amount is too high, it will cause it to phase separate from the epoxy resin on a macro scale, affecting the modification effect. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] In the present invention, the materials used and their sources are: the inhibitor is inhibitor 701, which comes from Shanghai Aladdin Biochemical Technology Co., Ltd.; the recarburizer and silicon-manganese alloy are both from Anyang Jinsheng Metallurgical Materials Co., Ltd.; the recarburizer is a graphite particle recarburizer with a particle size of 1 to 5 mm; the silicon-manganese alloy is item number 6014; the calcium carbide comes from Inner Mongolia Baiyanhu Chemical Co., Ltd., a high-quality product; the activated lime comes from Hunan Haocheng Technology Co., Ltd., with a calcium oxide content of 80 to 96%; the epoxy diluent comes from Anhui Xinyuan Technology Co., Ltd., item number XY630; the nano-silicon dioxide comes from Jiangsu Xianfeng Nanomaterial Technology Co., Ltd., numbered XFI03; the epoxy resin is epoxy resin E-51, and the curing agent is T-31, both of which are from Wuxi Pinhua Chemical Co., Ltd.

[0027] Embodiment 1: A high-cleanliness steel material and a preparation method thereof, comprising the following steps:

[0028] Step 1: desulfurizing the molten iron to an S mass content of 0.005%, then blowing in a converter, supplying oxygen to make slag for dephosphorization and decarburization, and pulling carbon to control the C mass content of the molten steel to be 0.20% at the end of blowing, to obtain a low-phosphorus and low-nitrogen molten steel with a slag basicity of 4.5; the P mass content of the low-phosphorus and low-nitrogen molten steel is 0.003% and the N mass content is 0.001%;

[0029] Step 2: tapping the low-phosphorus and low-nitrogen molten steel, controlling the tapping speed to be 100 kg / s, adding silicon-manganese alloy and carburizer during the tapping process, blowing argon gas from the bottom of the ladle, and the argon gas flow rate to be 2.0 NL / (min·t), to obtain argon-blown alloyed molten steel;

[0030] Step 3: electrically heating the argon-blown alloyed molten steel through an LF furnace, adding calcium carbide and activated lime into the molten steel for refining for 15 minutes, bottom blowing argon, the argon flow rate is 0.5NL / (min·t), the argon blowing time is 5 minutes, and LF refined molten steel is obtained; the amount of calcium carbide added is 0.02% of the total weight of the molten steel, and the amount of activated lime added is 0.2% of the total weight of the molten steel;

[0031] Step 4: The LF refined molten steel enters the RH vacuum cycle and blows argon gas at the bottom to obtain finished molten steel; the argon gas flow rate is 10NL / (min·t), the vacuum cycle time is 15min, and the cycle vacuum degree is 200Pa;

[0032] Step 5: Casting and rolling the finished molten steel under double argon seal protection to obtain a steel casting, coating the surface of the steel casting with a fluorinated acrylate polymer modified epoxy resin coating to form a coating with a thickness of 300 μm; curing at 120° C. to obtain a high-cleanliness steel material; wherein the fluorinated acrylate polymer modified epoxy resin coating contains 100 g of fluorinated acrylate polymer modified epoxy resin, 8 g of epoxy diluent, 4 g of nano-silicon dioxide, and 16 g of curing agent, wherein the preparation method of the fluorinated acrylate polymer modified epoxy resin comprises the following steps:

[0033] S1: Under nitrogen environment, add 2 mol of glycidol to 1 mol of triphenylmethane triisocyanate, control the addition of glycidol within 20 min, use dibutyltin dilaurate as catalyst, heat to 50 °C and react for 2 h to obtain diepoxy-modified phenylmethane isocyanate;

[0034] S2: Under nitrogen environment, take 1 mol of tetrafluorobutanediol, heat it to 85°C to melt; mix 1 mol of 2-methyl-2-acrylic acid-2-isocyanatoethyl ester with an inhibitor (the amount of the inhibitor is 5‰ of the total weight of 2-methyl-2-acrylic acid-2-isocyanatoethyl ester), add it to the molten tetrafluorobutanediol, use dibutyltin dilaurate as a catalyst, react for 1 hour, and obtain a fluorine-modified monomer;

[0035] S3: In a nitrogen environment, diepoxy-modified phenylmethane isocyanate and fluorine-modified monomer are mixed in a molar ratio of isocyanate group to hydroxyl group of 1:1, dibutyltin dilaurate is used as a catalyst, the temperature is raised to 50°C for reaction for 2h, and epoxy-modified fluorine-containing monomer is obtained;

[0036] S4: Mix the epoxy-modified fluorinated monomer and epoxy resin, heat to 80°C, stir to disperse the epoxy-modified fluorinated monomer, add a mixture of butyl acrylate and methyl methacrylate dropwise while keeping warm, use azobisisobutyronitrile as an initiator, react for 7 hours, remove the unreacted monomers in vacuo, and obtain a fluorinated acrylate polymer modified epoxy resin; wherein the mass ratio of the epoxy-modified fluorinated monomer, 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] Embodiment 2: A high-cleanliness steel material and a preparation method thereof, comprising the following steps:

[0038] Step 1: desulfurizing the molten iron to an S mass content of 0.007%, then blowing in a converter, supplying oxygen to make slag for dephosphorization and decarburization, and pulling carbon to control the C mass content of the molten steel at the end of blowing to be 0.20%, thereby obtaining a low-phosphorus and low-nitrogen molten steel with a slag basicity of 5; the P mass content of the low-phosphorus and low-nitrogen molten steel is 0.005% and the N mass content is 0.0012%;

[0039] Step 2: tapping the low-phosphorus and low-nitrogen molten steel, controlling the tapping speed to be 200 kg / s, adding silicon-manganese alloy and carburizer during the tapping process, blowing argon gas from the bottom of the ladle, and the argon gas flow rate to be 3 NL / (min·t), to obtain argon-blown alloyed molten steel;

[0040] Step 3: electrically heating the argon-blown alloyed molten steel through an LF furnace, adding calcium carbide and activated lime into the molten steel for refining for 18 minutes, bottom blowing argon, the argon flow rate is 1NL / (min·t), the argon blowing time is 10 minutes, and LF refined molten steel is obtained; the amount of calcium carbide added is 0.028% of the total weight of the molten steel, and the amount of activated lime added is 0.25% of the total weight of the molten steel;

[0041] Step 4: The LF refined molten steel enters the RH vacuum cycle and blows argon gas at the bottom to obtain finished molten steel; the argon gas flow rate is 11NL / (min·t), the vacuum cycle time is 20min, and the cycle vacuum degree is 240Pa;

[0042] Step 5: Casting and rolling the finished molten steel under double argon seal protection to obtain a steel casting, coating the surface of the steel casting with a fluorinated acrylate polymer modified epoxy resin coating to form a coating with a thickness of 300 μm; curing at 130° C. to obtain a high-cleanliness steel material; wherein the fluorinated acrylate polymer modified epoxy resin coating contains 100 g of fluorinated acrylate polymer modified epoxy resin, 8 g of epoxy diluent, 4 g of nano-silicon dioxide, and 16 g of curing agent, wherein the preparation method of the fluorinated acrylate polymer modified epoxy resin comprises the following steps:

[0043] S1: Under nitrogen environment, add 2 mol of glycidol to 1 mol of triphenylmethane triisocyanate, control the addition of glycidol within 25 min, use dibutyltin dilaurate as catalyst, heat to 55 °C and react for 2.5 h to obtain diepoxy-modified phenylmethane isocyanate;

[0044] S2: Under nitrogen environment, take 1 mol of tetrafluorobutanediol, heat it to 88°C to melt; mix 1 mol of 2-methyl-2-acrylic acid-2-isocyanatoethyl ester with an inhibitor (the amount of the inhibitor is 5‰ of the total weight of 2-methyl-2-acrylic acid-2-isocyanatoethyl ester), add it to the molten tetrafluorobutanediol, use dibutyltin dilaurate as a catalyst, react for 1.5 hours, and obtain a fluorine-modified monomer;

[0045] S3: In a nitrogen environment, diepoxy-modified phenylmethane isocyanate and fluorine-modified monomer are mixed in a molar ratio of isocyanate group to hydroxyl group of 1:1, dibutyltin dilaurate is used as a catalyst, the temperature is raised to 55°C for reaction for 2.5 hours, and epoxy-modified fluorine-containing monomer is obtained;

[0046] S4: Mix the epoxy-modified fluorine-containing monomer and the epoxy resin, heat to 85°C, stir to disperse the epoxy-modified fluorine-containing monomer, add a mixture of butyl acrylate and methyl methacrylate dropwise while keeping warm, use azobisisobutyronitrile as an initiator, react for 8.5 hours, remove the unreacted monomers in vacuo, and obtain a fluorine-containing acrylate polymer modified epoxy resin; wherein the mass ratio of the epoxy-modified fluorine-containing monomer, butyl acrylate, and methyl methacrylate is 10:60:30; the content of each component in the fluorine-containing acrylate polymer modified epoxy resin, by weight percentage, is 20% fluorine-containing acrylate polymer and 80% epoxy resin.

[0047] Embodiment 3: A high-cleanliness steel material and a preparation method thereof, comprising the following steps:

[0048] Step 1: desulfurizing the molten iron to an S mass content of 0.008%, then blowing in a converter, supplying oxygen to make slag for dephosphorization and decarburization, and pulling carbon to control the C mass content of the molten steel to be 0.20% at the end of blowing, to obtain a low-phosphorus and low-nitrogen molten steel with a slag basicity of 6.0; the P mass content of the low-phosphorus and low-nitrogen molten steel is 0.006% and the N mass content is 0.0015%;

[0049] Step 2: tapping the low-phosphorus and low-nitrogen molten steel, controlling the tapping speed to be 300 kg / s, adding silicon-manganese alloy and carburizer during the tapping process, blowing argon gas from the bottom of the ladle, and the argon gas flow rate to be 3.5 NL / (min·t), to obtain argon-blown alloyed molten steel;

[0050] Step 3: electrically heating the argon-blown alloyed molten steel through an LF furnace, adding calcium carbide and activated lime into the molten steel for refining for 20 minutes, bottom blowing argon, the argon flow rate is 1.5NL / (min·t), the argon blowing time is 15 minutes, and LF refined molten steel is obtained; the amount of calcium carbide added is 0.03% of the total weight of the molten steel, and the amount of activated lime added is 0.3% of the total weight of the molten steel;

[0051] Step 4: The LF refined molten steel enters the RH vacuum cycle and blows argon gas at the bottom to obtain finished molten steel; the argon gas flow rate is 12NL / (min·t), the vacuum cycle time is 25min, and the cycle vacuum degree is 300Pa;

[0052] Step 5: Casting and rolling the finished molten steel under double argon seal protection to obtain a steel casting, coating the surface of the steel casting with a fluorinated acrylate polymer modified epoxy resin coating to form a coating with a thickness of 300 μm; curing at 140° C. to obtain a high-cleanliness steel material; wherein the fluorinated acrylate polymer modified epoxy resin coating contains 100 g of fluorinated acrylate polymer modified epoxy resin, 8 g of epoxy diluent, 4 g of nano-silicon dioxide, and 16 g of curing agent, wherein the preparation method of the fluorinated acrylate polymer modified epoxy resin comprises the following steps:

[0053] S1: Under nitrogen environment, add 2 mol of glycidol to 1 mol of triphenylmethane triisocyanate, control the addition of glycidol within 30 min, use dibutyltin dilaurate as catalyst, heat to 60 °C and react for 3 h to obtain diepoxy-modified phenylmethane isocyanate;

[0054] S2: Under nitrogen environment, take 1 mol of tetrafluorobutanediol, heat it to 90°C to melt; mix 1 mol of 2-methyl-2-acrylic acid-2-isocyanatoethyl ester with an inhibitor (the amount of the inhibitor is 5‰ of the total weight of 2-methyl-2-acrylic acid-2-isocyanatoethyl ester), add it to the molten tetrafluorobutanediol, use dibutyltin dilaurate as a catalyst, react for 2 hours, and obtain a fluorine-modified monomer;

[0055] S3: In a nitrogen environment, diepoxy-modified phenylmethane isocyanate and fluorine-modified monomer are mixed in a molar ratio of isocyanate group to hydroxyl group of 1:1, dibutyltin dilaurate is used as a catalyst, the temperature is raised to 60°C for reaction for 3 hours, and epoxy-modified fluorine-containing monomer is obtained;

[0056] S4: Mix the epoxy-modified fluorinated monomer and epoxy resin, heat to 90°C, stir to disperse the epoxy-modified fluorinated monomer, add a mixture of butyl acrylate and methyl methacrylate dropwise while keeping warm, use azobisisobutyronitrile as an initiator, react for 10 hours, remove the unreacted monomers in vacuo, and obtain a fluorinated acrylate polymer modified epoxy resin; wherein the mass ratio of the epoxy-modified fluorinated monomer, 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: The epoxy resin is not modified by using the fluorinated acrylate polymer, and the other parameters are the same as those in Example 1.

[0058] Step 1: desulfurizing the molten iron to an S mass content of 0.005%, then blowing in a converter, supplying oxygen to make slag for dephosphorization and decarburization, and pulling carbon to control the C mass content of the molten steel to be 0.20% at the end of blowing, to obtain a low-phosphorus and low-nitrogen molten steel with a slag basicity of 4.5; the P mass content of the low-phosphorus and low-nitrogen molten steel is 0.003% and the N mass content is 0.001%;

[0059] Step 2: tapping the low-phosphorus and low-nitrogen molten steel, controlling the tapping speed to be 100 kg / s, adding silicon-manganese alloy and carburizer during the tapping process, blowing argon gas from the bottom of the ladle, and the argon gas flow rate to be 2.0 NL / (min·t), to obtain argon-blown alloyed molten steel;

[0060] Step 3: electrically heating the argon-blown alloyed molten steel through an LF furnace, adding calcium carbide and activated lime into the molten steel for refining for 15 minutes, bottom blowing argon, the argon flow rate is 0.5NL / (min·t), the argon blowing time is 5 minutes, and LF refined molten steel is obtained; the amount of calcium carbide added is 0.02% of the total weight of the molten steel, and the amount of activated lime added is 0.2% of the total weight of the molten steel;

[0061] Step 4: The LF refined molten steel enters the RH vacuum cycle and blows argon gas at the bottom to obtain finished molten steel; the argon gas flow rate is 10NL / (min·t), the vacuum cycle time is 15min, and the cycle vacuum degree is 200Pa;

[0062] Step 5: The finished molten steel is cast and rolled under double argon protection to obtain a steel casting, and an epoxy resin coating is applied on the surface of the steel casting to form a coating with a thickness of 300 μm; and the coating is cured at 120° C. to obtain a high-cleanliness steel material; wherein the epoxy resin coating contains 100 g of fluorinated acrylate polymer modified epoxy resin, 8 g of epoxy diluent, 4 g of nano-silica, and 16 g of curing agent.

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

[0064] Step 1: desulfurizing the molten iron to an S mass content of 0.007%, then blowing in a converter, supplying oxygen to make slag for dephosphorization and decarburization, and pulling carbon to control the C mass content of the molten steel at the end of blowing to be 0.20%, thereby obtaining a low-phosphorus and low-nitrogen molten steel with a slag basicity of 5; the P mass content of the low-phosphorus and low-nitrogen molten steel is 0.005% and the N mass content is 0.0012%;

[0065] Step 2: tapping the low-phosphorus and low-nitrogen molten steel, controlling the tapping speed to be 200 kg / s, adding silicon-manganese alloy and carburizer during the tapping process, blowing argon gas from the bottom of the ladle, and the argon gas flow rate to be 3 NL / (min·t), to obtain argon-blown alloyed molten steel;

[0066] Step 3: electrically heating the argon-blown alloyed molten steel through an LF furnace, adding calcium carbide and activated lime into the molten steel for refining for 18 minutes, bottom blowing argon, the argon flow rate is 1NL / (min·t), the argon blowing time is 10 minutes, and LF refined molten steel is obtained; the amount of calcium carbide added is 0.028% of the total weight of the molten steel, and the amount of activated lime added is 0.25% of the total weight of the molten steel;

[0067] Step 4: The LF refined molten steel enters the RH vacuum cycle and blows argon gas at the bottom to obtain finished molten steel; the argon gas flow rate is 11NL / (min·t), the vacuum cycle time is 20min, and the cycle vacuum degree is 240Pa;

[0068] Step 5: Casting and rolling the finished molten steel under double argon seal protection to obtain a steel casting, coating the surface of the steel casting with a fluorinated acrylate polymer modified epoxy resin coating to form a coating with a thickness of 300 μm; curing at 130° C. to obtain a high-cleanliness steel material; wherein the fluorinated acrylate polymer modified epoxy resin coating contains 100 g of fluorinated acrylate polymer modified epoxy resin, 8 g of epoxy diluent, 4 g of nano-silicon dioxide, and 16 g of curing agent, wherein the preparation method of the fluorinated acrylate polymer modified epoxy resin comprises the following steps:

[0069] The epoxy resin is heated to 85°C, and a mixture of butyl acrylate and methyl methacrylate is added dropwise while maintaining the temperature, and azobisisobutyronitrile is used as an initiator. The reaction is carried out for 8.5 hours, and the unreacted monomers are removed in vacuo to obtain an acrylate polymer modified epoxy resin; wherein the mass ratio of butyl acrylate to methyl methacrylate is 60:30; and the content of each component in the acrylate polymer modified epoxy resin is, by weight percentage, 20% acrylate polymer and 80% epoxy resin.

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

[0071] Step 1: desulfurizing the molten iron to an S mass content of 0.008%, then blowing in a converter, supplying oxygen to make slag for dephosphorization and decarburization, and pulling carbon to control the C mass content of the molten steel to be 0.20% at the end of blowing, to obtain a low-phosphorus and low-nitrogen molten steel with a slag basicity of 6.0; the P mass content of the low-phosphorus and low-nitrogen molten steel is 0.006% and the N mass content is 0.0015%;

[0072] Step 2: tapping the low-phosphorus and low-nitrogen molten steel, controlling the tapping speed to be 300 kg / s, adding silicon-manganese alloy and carburizer during the tapping process, blowing argon gas from the bottom of the ladle, and the argon gas flow rate to be 3.5 NL / (min·t), to obtain argon-blown alloyed molten steel;

[0073] Step 3: electrically heating the argon-blown alloyed molten steel through an LF furnace, adding calcium carbide and activated lime into the molten steel for refining for 20 minutes, bottom blowing argon, the argon flow rate is 1.5NL / (min·t), the argon blowing time is 15 minutes, and LF refined molten steel is obtained; the amount of calcium carbide added is 0.03% of the total weight of the molten steel, and the amount of activated lime added is 0.3% of the total weight of the molten steel;

[0074] Step 4: The LF refined molten steel enters the RH vacuum cycle and blows argon gas at the bottom to obtain finished molten steel; the argon gas flow rate is 12NL / (min·t), the vacuum cycle time is 25min, and the cycle vacuum degree is 300Pa;

[0075] Step 5: Casting and rolling the finished molten steel under double argon seal protection to obtain a steel casting, coating the surface of the steel casting with a fluorinated acrylate polymer modified epoxy resin coating to form a coating with a thickness of 300 μm; curing at 140° C. to obtain a high-cleanliness steel material; wherein the fluorinated acrylate polymer modified epoxy resin coating contains 100 g of fluorinated acrylate polymer modified epoxy resin, 8 g of epoxy diluent, 4 g of nano-silicon dioxide, and 16 g of curing agent, wherein the preparation method of the fluorinated acrylate polymer modified epoxy resin comprises the following steps:

[0076] S1: Under nitrogen environment, add 2 mol of glycidol to 1 mol of triphenylmethane triisocyanate, control the addition of glycidol within 30 min, use dibutyltin dilaurate as catalyst, heat to 60 °C and react for 3 h to obtain diepoxy-modified phenylmethane isocyanate;

[0077] S2: Under nitrogen environment, take 1 mol of tetrafluorobutanediol, heat it to 90°C to melt; mix 1 mol of 2-methyl-2-acrylic acid-2-isocyanatoethyl ester with an inhibitor (the amount of the inhibitor is 5‰ of the total weight of 2-methyl-2-acrylic acid-2-isocyanatoethyl ester), add it to the molten tetrafluorobutanediol, use dibutyltin dilaurate as a catalyst, react for 2 hours, and obtain a fluorine-modified monomer;

[0078] S3: In a nitrogen environment, diepoxy-modified phenylmethane isocyanate and fluorine-modified monomer are mixed in a molar ratio of isocyanate group to hydroxyl group of 1:1, dibutyltin dilaurate is used as a catalyst, the temperature is raised to 60°C for reaction for 3 hours, and epoxy-modified fluorine-containing monomer is obtained;

[0079] S4: Mix the epoxy-modified fluorine-containing monomer and the epoxy resin, heat to 90°C, stir to disperse the epoxy-modified fluorine-containing monomer, add a mixture of butyl acrylate and methyl methacrylate dropwise while keeping warm, use azobisisobutyronitrile as an initiator, react for 10 hours, remove the unreacted monomers in vacuo, and obtain a fluorine-containing acrylate polymer modified epoxy resin; wherein the mass ratio of the epoxy-modified fluorine-containing monomer, butyl acrylate, and methyl methacrylate is 10:60:30; in the fluorine-containing acrylate polymer modified epoxy resin, the content of each component, by weight percentage, is 35% fluorine-containing acrylate polymer and 65% epoxy resin.

[0080] experiment:

[0081] The contents of C, P, S and N elements in the finished molten steel in Examples 1 to 3 were measured, 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 steel prepared in Examples 1 to 3 and Comparative Examples 1 to 3 was tested, and a neutral salt spray test was performed 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 temperature in the box was (35±1)°C, and the corrosive medium was a 5% NaCl aqueous solution; the adhesion and surface morphology of the coating were tested before and after the salt spray test for 3000h; wherein, the adhesion test method was as follows: according to GB / T5210-2006 "Paint and varnish pull-off method adhesion test", the adhesion between the coating and the metal substrate was tested by a pull-off method 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 contents of the main impurity elements C, S, P, and N in the molten steel in Examples 1 to 3 are low, and the prepared steel has high cleanliness. In Table 2, the data of Examples 1 to 3 show that the surface of the high-cleanliness steel prepared by the present invention has good corrosion resistance, and the apparent performance change of the coating is lower than that of Comparative Examples 1 to 3. The data of Example 1 and Comparative Example 1 show that, compared with a single epoxy resin coating, the epoxy resin coating modified by a fluorinated acrylate polymer has stronger corrosion resistance; the data of Example 2 and Comparative Example 2 show that the epoxy group in the epoxy-modified fluorinated monomer can effectively improve the compatibility between the epoxy resin and the acrylate polymer, and the fluorine element can improve the corrosion resistance of the coating, enhance the protective effect of the coating on steel, and thus slow down the corrosion of the steel; the data of Example 3 and Comparative Example 3 show that, by increasing the amount of the fluorinated acrylate polymer, on the one hand, due to the low surface energy of the fluorine element, more fluorine elements migrate to the interface and reduce the adhesion of the coating; on the other hand, the compatibility of the fluorinated acrylate polymer with a higher content becomes poorer with the epoxy resin, and after a long period of salt spray test, observable bubbling occurs, which is because the two are phase separated on a macro scale.

[0088] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing high-cleanliness steel, characterized in that: The following steps are involved: Step 1: desulfurize the molten iron, then perform converter blowing, supply oxygen for slagging, dephosphorize and decarburize, and pull carbon to control the C mass content of the molten steel at the end of blowing to be 0.05-0.20%, and obtain low-phosphorus and low-nitrogen molten steel with slag basicity of 4.5-6.0; Step 2: tapping the low-phosphorus and low-nitrogen molten steel, adding silicon-manganese alloy and carburizer during the tapping process, blowing argon gas from the bottom of the ladle to obtain argon-blown alloyed molten steel; Step 3: electrically heating the argon-blown alloyed molten steel through an LF furnace, adding calcium carbide and activated lime into the molten steel for refining, and bottom blowing argon to obtain LF refined molten steel; Step 4: The LF refined molten steel enters the RH vacuum cycle and argon is blown from the bottom to obtain finished molten steel; Step 5: The finished molten steel is cast and rolled under double argon protection to obtain a steel casting, and a fluorinated acrylate polymer modified epoxy resin coating is coated on the surface of the steel casting to form a coating with a thickness of 150 to 300 μm; and the coating is cured at 120 to 140° C. to obtain a high-cleanliness steel.

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

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

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

6. The method for preparing a high-cleanliness steel material according to claim 1, characterized in that: In step 5, the contents of the components in the fluorinated acrylate polymer modified epoxy resin coating are, by weight, 100 parts of fluorinated acrylate polymer modified epoxy resin, 6 to 8 parts of epoxy diluent, 3 to 4 parts of nano-silicon dioxide, and 10 to 25 parts of curing agent.

7. The method for preparing a high-cleanliness steel material according to claim 6, characterized in that: The preparation method of fluorine-containing acrylate polymer modified epoxy resin coating comprises the following steps: mixing epoxy group modified fluorine-containing monomer and epoxy resin, heating to 80-90° C., stirring to disperse the epoxy group modified fluorine-containing monomer, adding dropwise a mixture of butyl acrylate, methyl methacrylate and azobisisobutyronitrile under heat preservation, reacting for 7-10 hours, and removing unreacted monomers under vacuum to obtain fluorine-containing acrylate polymer modified epoxy resin.

8. The method for preparing a high-cleanliness steel material according to claim 7, characterized in that: The preparation method of epoxy-modified fluorinated monomer is as follows: S1: under nitrogen environment, add glycidol to triphenylmethane triisocyanate, control the glycidol to be added within 20-30 minutes, use dibutyltin dilaurate as a catalyst, heat to 50-60°C for reaction for 2-3 hours, and obtain diepoxy-modified phenylmethane isocyanate; wherein triphenylmethane triisocyanate and glycidol react in a molar ratio of 1:2; S2: Under a nitrogen environment, tetrafluorobutanediol is taken and heated to 85-90°C for melting; 2-methyl-2-acrylic acid-2-isocyanate ethyl is mixed with an inhibitor, and then added to the molten tetrafluorobutanediol, and dibutyltin dilaurate is used as a catalyst to react for 1-2 hours to obtain a fluorine-modified monomer; wherein tetrafluorobutanediol and 2-methyl-2-acrylic acid-2-isocyanate ethyl are mixed in a molar ratio of 1:1, and the amount of the inhibitor is 5‰ of the total weight of 2-methyl-2-acrylic acid-2-isocyanate ethyl; S3: Under a nitrogen environment, diepoxy-modified phenylmethane isocyanate and fluorine-modified monomer are mixed in a molar ratio of isocyanate group to hydroxyl group of 1:1, dibutyltin dilaurate is used as a catalyst, the temperature is raised to 50-60°C and the reaction is carried out for 2-3 hours to obtain an epoxy-modified fluorine-containing monomer.

9. The method for preparing a high-cleanliness steel material according to claim 7, characterized in that: The mass ratio of epoxy-modified fluorinated monomer, butyl acrylate and methyl methacrylate is (10-15):(60-65):(20-30); the content of each component in the fluorinated acrylate polymer modified epoxy resin is, by weight percentage, 17-22% fluorinated acrylate polymer and 78-83% epoxy resin.

10. The high-cleanliness steel material prepared by the method for preparing a high-cleanliness steel material according to any one of claims 1 to 9.

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