Molten steel deoxidizer and preparation method thereof

Abstract

The invention discloses a molten steel deoxidizing agent and a preparation method thereof, and relates to the technical field of deoxidizing agents. The molten steel deoxidizing agent comprises the following raw materials in parts by weight: 20-30 parts of calcium oxide, 60-80 parts of calcium carbide, 10-15 parts of fluorite and 2-6 parts of a modified epoxy resin binder. Polyamic acid is prepared through a copolymerization reaction of 2, 2 '-(1, 4-phenyl)-bis-(5-aminobenzimidazole) and bisphenol A dianhydride, and then bisphenol A epoxy resin is modified through bis (3-aminopropyl) terminated poly (dimethyl siloxane) to prepare organic silicon modified epoxy resin. Finally, polyamide acid is grafted to the organic silicon modified epoxy resin, and the modified epoxy resin binder is obtained. The molten steel deoxidizer prepared by the invention has the advantages of high mechanical strength, good deoxidizing effect and the like.

Description

Technical Field

[0001] The invention relates to the technical field of deoxidizers, and in particular to a molten steel deoxidizer and a preparation method thereof. Background Art

[0002] Al-CaO composite deoxidizer is easy to produce low melting point deoxidation products during use. This deoxidation product is liquid and mostly spherical at steelmaking temperature, which is easy to accumulate and float. Not only does it have fewer inclusions remaining in the steel, but it also avoids the phenomenon of nodules in the submerged nozzle of the crystallizer during continuous casting. However, it was found during use that the composite deoxidizer was easily crushed when it fell from a 10m high silo and was partially carried away by the gas, and could not enter the molten steel, resulting in increased costs, on-site dust pollution, and reduced deoxidation and desulfurization efficiency. Some researchers added clay and sodium carboxymethyl cellulose to LF refined slag to improve the strength of the refined slag. However, clay itself contains water, and sodium carboxymethyl cellulose must be added with water to play a bonding role, while calcium oxide, an important component of the composite deoxidizer, cannot be mixed with water. In addition, binders such as dextrin and bentonite also have this problem. Organic binder epoxy resin powder can play a bonding role by heating and consolidation, so it is particularly important to develop a high-performance organic binder to solve the existing problems.

[0003] A Chinese invention patent with publication number CN104775003A discloses a calcium-based deoxidizer capable of improving the fluidity of molten steel and a preparation method thereof. The calcium-based deoxidizer is composed of the following raw materials in parts by weight: 34-38 parts of calcium silicide, 12-16 parts of silicon carbide, 2.5-3.5 parts of drainage sand, 2-3 parts of coke powder, 3.5-5 parts of gelatin, and 40-50 parts of 5% hydrochloric acid. The calcium-based deoxidizer can effectively remove impurities in molten steel, improve the purity of molten steel, and prevent nodules at the tundish water outlet, but has poor mechanical properties. Summary of the invention

[0004] In view of the shortcomings of the prior art, the object of the present invention is to provide a molten steel deoxidizer and a preparation method thereof.

[0005] To achieve the above object, the present invention is implemented through the following technical solutions:

[0006] A molten steel deoxidizer, comprising the following raw materials in parts by weight:

[0007] Calcium oxide: 20-30 parts, calcium carbide: 60-80 parts, fluorite: 10-15 parts, modified epoxy resin binder: 2-6 parts;

[0008] The modified epoxy resin binder is prepared by the following method:

[0009] S1: Under nitrogen protection, add DMAc and 2,2'-(1,4-phenyl)-bis-(5-aminobenzimidazole) to the reaction bottle, stir and mix, then slowly add bisphenol A dianhydride, react in an ice water bath for 8-12h, then add deionized water for precipitation, filter, and vacuum dry to obtain polyamic acid powder. The reaction equation is as follows:

[0010]

[0011] S2: DMF, bisphenol A epoxy resin and bis(3-aminopropyl)-terminated poly(dimethylsiloxane) are added to the reactor in sequence, stirred and mixed, heated to 80-120°C, reacted for 4-6h, cooled to 60-80°C, triethylamine was added for neutralization, and the organosilicon-modified epoxy resin was obtained by vacuum distillation. The reaction equation is as follows:

[0012]

[0013] S3: Under nitrogen protection, DMF, polyamic acid powder, and organosilicon-modified epoxy resin are added to the reactor, heated in an oil bath to 100-120°C, and then concentrated sulfuric acid is added. The reaction is refluxed for 4-6 hours, and the modified epoxy resin binder is obtained by reduced pressure distillation and vacuum drying. The reaction equation is as follows:

[0014]

[0015] Among them, a, m, n, o, p, q, and s are all natural numbers.

[0016] In step S1, the mass ratio of DMAc, 2,2'-(1,4-phenyl)-bis-(5-aminobenzimidazole), and bisphenol A dianhydride is 100:(6-10):(12-16).

[0017] In step S2, the feed mass ratio of DMF, bisphenol A epoxy resin, and bis(3-aminopropyl)-terminated poly(dimethylsiloxane) is 50:(8-12):(10-16).

[0018] In step S3, the mass ratio of the DMF, polyamic acid powder and silicone-modified epoxy resin is 50:(10-15):(4-6).

[0019] A method for preparing a molten steel deoxidizer comprises the following steps:

[0020] (1) Weigh 20-30 parts of calcium oxide, 60-80 parts of calcium carbide, 10-15 parts of fluorite, and 2-6 parts of modified epoxy resin binder by weight;

[0021] (2) Place all materials in a grinding wheel sand mixer and stir them thoroughly. Add the mixed materials into a friction brick press to make them into balls to make semi-finished products. Then, place the semi-finished products in a belt dryer to dry them to obtain a molten steel deoxidizer.

[0022] Due to the adoption of the above technical solution, the beneficial effects of the present invention include:

[0023] (1) The present invention prepares polyamic acid by copolymerization of 2,2'-(1,4-phenyl)-bis-(5-aminobenzimidazole) and bisphenol A dianhydride, then modifies bisphenol A epoxy resin by bis(3-aminopropyl)-terminated poly(dimethylsiloxane) to prepare silicone-modified epoxy resin, and finally grafts the polyamic acid onto the silicone-modified epoxy resin to obtain a modified epoxy resin adhesive.

[0024] (2) Various active functional groups (-COOH, -COH, -OH, etc.) in the molecular structure of the modified epoxy resin binder prepared by the present invention react with metal ions (Ca 2+ ) and metal oxides such as calcium oxide, generate stable chelate, form coordination between calcium oxide fine powder particles and binder molecules, thereby improve the intensity of deoxidizer. Polyamic acid is the prepolymer of polyimide, contains carbonyl and amide bond in its molecular chain, can have ring-opening reaction with the epoxy group in epoxy resin molecular chain, form interpenetrating network-shaped cross-linked structure, and compared with polyimide, polyamic acid has better compatibility with epoxy resin. Simultaneously, organosilicon is added in epoxy resin, compared with carbon-carbon bond, the bond energy of silicon oxygen bond is much higher, and this just makes the rigidity of segment stronger, strengthens the mechanical property of binder, thereby makes the deoxidizer of preparation have higher mechanical strength.

[0025] (3) The deoxidizer prepared by the present invention improves the fluidity of molten steel and reduces the distribution coefficient, making it easier for molten steel to enter small cavities. The gas in these small cavities can easily cause the formation of pores. By using a deoxidizer, the formation of pores can be reduced, thereby improving the solidification process of molten steel. At the same time, by removing oxygen from the molten steel, the deoxidizer can effectively reduce the oxygen content in the molten steel, thereby reducing the inclusion content in the molten steel. Therefore, by using a deoxidizer, the quality of molten steel can be improved, and the performance of the final product can be made better. DETAILED DESCRIPTION

[0026] The invention will be further described below in conjunction with the embodiments, but the invention is not limited to these embodiments.

[0027] Example 1

[0028] Preparation of modified epoxy resin adhesive:

[0029] S1: Under nitrogen protection, add 1 kg DMAc and 60 g 2,2'-(1,4-phenyl)-bis-(5-aminobenzimidazole) (CAS No.: 28689-19-2) to the reaction bottle, stir to mix, then slowly add 120 g bisphenol A dianhydride (CAS No.: 38103-06-9), react in an ice-water bath for 8 h, then add 2 kg deionized water for precipitation, filter, and vacuum dry at 80 ° C for 6 h to obtain polyamic acid powder.

[0030] S2: 500g DMF, 80g bisphenol A epoxy resin and 100g bis(3-aminopropyl)-terminated poly(dimethylsiloxane) were added into the reactor in sequence, stirred and mixed, heated to 80°C, reacted for 6h, cooled to 60°C, 350g triethylamine was added for neutralization, and the organosilicon-modified epoxy resin was obtained by reduced pressure distillation at 80°C for 6h.

[0031] S3: Under nitrogen protection, 500g DMF, 100g polyamic acid powder and 40g organosilicon-modified epoxy resin were added into the reactor, heated in an oil bath to 100°C, and then 20g 83wt% concentrated sulfuric acid was added. The reaction was refluxed for 6h, and the modified epoxy resin adhesive was obtained by reduced pressure distillation at 50°C for 5h and vacuum drying at 70°C for 6h.

[0032] Example 2

[0033] Preparation of modified epoxy resin adhesive:

[0034] S1: Under nitrogen protection, add 1 kg DMAc and 80 g 2,2'-(1,4-phenyl)-bis-(5-aminobenzimidazole) into the reaction bottle, stir to mix, then slowly add 140 g bisphenol A dianhydride, react in an ice-water bath for 10 h, then add 2 kg deionized water for precipitation, filter, and vacuum dry at 90 ° C for 5 h to obtain polyamic acid powder.

[0035] S2: 500g DMF, 100g bisphenol A epoxy resin and 130g bis(3-aminopropyl)-terminated poly(dimethylsiloxane) were added into the reactor in sequence, stirred and mixed, heated to 100°C, reacted for 5h, cooled to 70°C, 400g triethylamine was added for neutralization, and the organosilicon-modified epoxy resin was obtained by reduced pressure distillation at 90°C for 5h.

[0036] S3: Under nitrogen protection, 500g DMF, 125g polyamic acid powder and 50g organosilicon-modified epoxy resin were added into the reactor, heated in an oil bath to 110°C, and then 22g 83wt% concentrated sulfuric acid was added. The mixture was refluxed for 5h, and then vacuum-distilled at 60°C for 4h and dried at 80°C for 5h to obtain the modified epoxy resin adhesive.

[0037] Example 3

[0038] Preparation of modified epoxy resin adhesive:

[0039] S1: Under nitrogen protection, add 1 kg DMAc and 100 g 2,2'-(1,4-phenyl)-bis-(5-aminobenzimidazole) to the reaction bottle, stir and mix until it is evenly dispersed in DMAc, then slowly add 160 g bisphenol A dianhydride, react in an ice-water bath for 12 h, then add 2 kg deionized water for precipitation, filter, and vacuum dry at 100 ° C for 4 h to obtain polyamic acid powder.

[0040] S2: Add 500gDMF, 120g bisphenol A epoxy resin and 160g bis(3-aminopropyl)-terminated poly(dimethylsiloxane) into the reactor in sequence, stir to mix, heat to 120°C, react for 4h, cool to 80°C, add 450g triethylamine for neutralization, and distill at 100°C under reduced pressure for 4h to obtain silicone-modified epoxy resin.

[0041] S3: Under nitrogen protection, 500g DMF, 150g polyamic acid powder and 60g organosilicon-modified epoxy resin were added into the reactor, heated in an oil bath to 120°C, and then 25g 83wt% concentrated sulfuric acid was added. The mixture was refluxed for 4h, and then vacuum-distilled at 70°C for 3h and dried at 90°C for 4h to obtain the modified epoxy resin adhesive.

[0042] Example 4

[0043] Preparation of molten steel deoxidizer:

[0044] (1) Weigh 200 g of calcium oxide, 600 g of calcium carbide, 100 g of fluorite, and 20 g of modified epoxy resin binder (prepared in Example 1);

[0045] (2) Place all materials in a grinding wheel sand mixer and stir them at a speed of 500 r / min for 30 min. Mix them thoroughly and evenly. Add the mixed materials into a friction brick press to make them into spheres with a particle size of 200 mesh to make semi-finished products. Then put the semi-finished products into a belt dryer and dry them at a drying temperature of 160°C for 10 h to obtain a molten steel deoxidizer.

[0046] Example 5

[0047] Preparation of molten steel deoxidizer:

[0048] (1) Weigh 250 g of calcium oxide, 700 g of calcium carbide, 125 g of fluorite, and 40 g of modified epoxy resin binder (prepared in Example 2);

[0049] (2) Place all materials in a grinding wheel sand mixer and stir them at a speed of 600 r / min for 25 min. Mix them thoroughly and evenly. Add the mixed materials into a friction brick press to make them into spheres with a particle size of 200 mesh to make semi-finished products. Then put the semi-finished products into a belt dryer for drying at a drying temperature of 210°C for 9 h to obtain a molten steel deoxidizer.

[0050] Example 6

[0051] Preparation of molten steel deoxidizer:

[0052] (1) Weigh 300 g of calcium oxide, 800 g of calcium carbide, 150 g of fluorite, and 60 g of modified epoxy resin binder (prepared in Example 3);

[0053] (2) Place all materials in a grinding wheel sand mixer and stir them at a speed of 700 r / min for 20 min. Mix them thoroughly and evenly. Add the mixed materials into a friction brick press to make them into spheres with a particle size of 200 mesh to make semi-finished products. Then put the semi-finished products into a belt dryer for drying at a drying temperature of 260°C for 8 h to obtain a molten steel deoxidizer.

[0054] Comparative Example 1

[0055] The preparation method of the molten steel deoxidizer is basically the same as that of Example 5, except that no modified epoxy resin binder is added to the composition.

[0056] Comparative Example 2

[0057] The preparation method of the molten steel deoxidizer is basically the same as that of Example 5, except that the modified epoxy resin binder is replaced by an equal weight of bentonite.

[0058] Comparative Example 3

[0059] The preparation method of the molten steel deoxidizer is basically the same as that of Example 5, except that the modified epoxy resin binder is replaced by an equal weight of modified starch.

[0060] Comparative Example 4

[0061] The preparation method of the molten steel deoxidizer is basically the same as that of Example 5, except that the modified epoxy resin binder is replaced by the organosilicon-modified epoxy resin prepared in step S2 of Example 2.

[0062] Comparative Example 5

[0063] The preparation method of molten steel deoxidizer is basically the same as that of Example 5, except that the modified epoxy resin binder is replaced by 28g of polyamic acid powder (prepared in step S1 of Example 2) and 12g of silicone-modified epoxy resin (prepared in step S2 of Example 2).

[0064] Comparative Example 6

[0065] The molten steel deoxidizer prepared in Example 5 was replaced with an equal weight of a commercially available silicon-aluminum composite deoxidizer.

[0066] Comparative Example 7

[0067] The raw materials of Example 3 of the Chinese invention patent with publication number CN104775003A are used to prepare a molten steel deoxidizer using the manufacturing process of the present application.

[0068] The modified starch used in the comparative examples of the present application is sodium carboxymethyl starch, purchased from Guangdong Hongxin Biotechnology Co., Ltd.; the bentonite model used in the comparative examples of the present application is Bentone 38, purchased from Dachanghua Jiahui Zhengxing Chemical (Shanghai) Co., Ltd.; the silicon-aluminum composite deoxidizer used in the comparative examples of the present application is purchased from Anyang Pengxing Metallurgical Refractory Co., Ltd.; the M of the bis(3-aminopropyl)-terminated poly(dimethylsiloxane) used in the examples and comparative examples of the present application n is 2500.

[0069] Crushing rate experiment: Take 100g of molten steel deoxidizer microspheres and drop them onto a steel plate from a height of 10 meters for a drop test. Then sieve them through a sieve. Particles with a size less than 150 mesh are considered crushed. Then the crushing rate is calculated. The test results are shown in Table 1.

[0070] Application example: The molten steel deoxidizer prepared in the examples and comparative examples of the present application is applied to the steelmaking process to prepare threaded steel with a radius of 22 mm. The specific process is as follows:

[0071] (1) Hot metal pretreatment: L08 pig iron is heated to 1400°C for melting, and a deoxidizer is used for deoxidation and alloying during the steelmaking process;

[0072] (2) Converter smelting: single slag method is adopted, and the slag basicity is controlled at 3.0;

[0073] (3) LF refining: Ce and Bi compounds are added in the later stage of refining, and the percentage of Ce and Bi elements is adjusted to make S ≤ 0.01wt%, the heating time is 20min, and the refining time is 20min;

[0074] (4) Continuous casting of special-shaped billets: full protection of pouring;

[0075] (5) Slab heating: The spacing between slabs is controlled to be 100 mm, the pressure in the furnace is 20 Pa, the heating time is 90 min, and the heating temperature is 1250°C; after the slabs are heated, high-pressure water is used for dephosphorization;

[0076] (6) Rolling: The rough rolling temperature is 1250°C and the final rolling temperature is 900°C;

[0077] (7) Cooling: first cool down to 700°C at a cooling rate of 20°C / s, then air cool to 110°C before straightening;

[0078] (8) Cut to length to obtain rebar.

[0079] According to GB / T 228-2002, the mechanical properties of rebar were tested. The test results are shown in Table 1.

[0080] According to GB / T 11261-2006 "Determination of oxygen content of steel - Pulse heating inert gas melting - infrared absorption method", the oxygen content in molten steel before and after the addition of deoxidizer was determined, and the total oxygen removal rate was calculated.

[0081] Table 1

[0082]

[0083]

[0084] It can be seen from Table 1 that the tensile strength and yield strength of the rebar produced using the molten steel deoxidizer prepared in Examples 4-6 of the present application are improved to a certain extent, and the deoxidation efficiency is above 95%.

[0085] Comparative Example 1 is a comparative example of a molten steel deoxidizer prepared without adding a modified epoxy resin binder. From the data in Table 1, it can be seen that its crushing rate is high in the 10-meter high altitude drop test, the mechanical strength is low, the deoxidation rate is 74.4%, and the deoxidation efficiency is low.

[0086] The binder added in Comparative Example 2 is bentonite. It can be seen from the data in Table 1 that its mechanical strength is low, the deoxidation rate is 76.5%, and the deoxidation efficiency is low.

[0087] The binder added in Comparative Example 3 is modified starch. It can be seen from the data in Table 1 that its mechanical strength is low, the deoxidation rate is 78.3%, and the deoxidation efficiency is low.

[0088] The binder added in Comparative Example 4 is the silicone-modified epoxy resin prepared in step S2 of Example 2. From the data in Table 1, it can be seen that its mechanical strength is average, the deoxidation rate is 82.6%, and the deoxidation efficiency is low.

[0089] The binder added in Comparative Example 5 is 28g of polyamic acid powder and 12g of silicone-modified epoxy resin. From the data in Table 1, it can be seen that the mechanical strength is average, the deoxidation rate is 86.6%, and the deoxidation efficiency is good.

[0090] The molten steel deoxidizer used in Comparative Example 6 is a commercially available silicon-aluminum composite deoxidizer. From the data in Table 1, it can be seen that its mechanical strength is average, the deoxidation rate is 81.5%, and the deoxidation efficiency is low.

[0091] Comparative Example 7 is a molten steel deoxidizer produced by using the production process of the present application using Example 3 of the Chinese invention patent with publication number CN104775003A. It can be seen from the data in Table 1 that its mechanical strength is poor, the deoxidation rate is 82.9%, and the deoxidation efficiency is average.

[0092] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. However, any equivalent changes, modifications and evolutions made by ordinary technicians in the field without departing from the scope of the technical solution of the present invention by using the technical content disclosed above are all equivalent embodiments of the present invention. At the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the technical solution of the present invention.

Claims

1. A molten steel deoxidizer, characterized in that: The invention comprises the following raw materials in parts by weight: Calcium oxide: 20-30 parts, calcium carbide: 60-80 parts, fluorite: 10-15 parts, modified epoxy resin binder: 2-6 parts; The modified epoxy resin binder is prepared by the following method: S1: Under nitrogen protection, add DMAc and 2,2'-(1,4-phenyl)-bis-(5-aminobenzimidazole) to a reaction bottle, stir and mix, then slowly add bisphenol A dianhydride, react in an ice water bath for 8-12 hours, then add deionized water for precipitation, filter, and vacuum dry to obtain polyamic acid powder; S2: DMF, bisphenol A epoxy resin and bis(3-aminopropyl)-terminated poly(dimethylsiloxane) are sequentially added into the reactor, stirred and mixed, heated to 80-120° C., reacted for 4-6 hours, cooled to 60-80° C., triethylamine was added for neutralization, and the organosilicon-modified epoxy resin was obtained by distillation under reduced pressure; S3: Under nitrogen protection, DMF, polyamic acid powder and organosilicon modified epoxy resin are added into the reactor, heated in an oil bath to 100-120°C, and then concentrated sulfuric acid is added, refluxed for 4-6 hours, and the modified epoxy resin binder is obtained by reduced pressure distillation and vacuum drying.

2. The molten steel deoxidizer according to claim 1, characterized in that: In step S1, the mass ratio of DMAc, 2,2'-(1,4-phenyl)-bis-(5-aminobenzimidazole), and bisphenol A dianhydride is 100:(6-10):(12-16).

3. The molten steel deoxidizer according to claim 1, characterized in that: In step S2, the feed mass ratio of DMF, bisphenol A epoxy resin, and bis(3-aminopropyl)-terminated poly(dimethylsiloxane) is 50:(8-12):(10-16).

4. The molten steel deoxidizer according to claim 1, characterized in that: In step S3, the mass ratio of the DMF, polyamic acid powder and silicone-modified epoxy resin is 50:(10-15):(4-6).

5. A method for preparing a molten steel deoxidizer according to any one of claims 1 to 4, characterized in that: The following steps are involved: (1) Weigh 20-30 parts of calcium oxide, 60-80 parts of calcium carbide, 10-15 parts of fluorite, and 2-6 parts of modified epoxy resin binder by weight; (2) Place all materials in a grinding wheel sand mixer and stir them thoroughly. Add the mixed materials into a friction brick press to make them into balls to make semi-finished products. Then, place the semi-finished products in a belt dryer to dry them to obtain a molten steel deoxidizer.

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