Rare earth composite deoxidizer applicable to aluminum deoxidation and sedation tapping process as well as preparation method and use method of rare earth composite deoxidizer

Abstract

The invention discloses a rare earth composite deoxidizer suitable for an aluminum deoxidizing and calming tapping process, which is characterized in that the rare earth aluminum carbon composite deoxidizer comprises the following chemical components in percentage by weight: 30-50% of rare earth iron alloy particles with the particle size of 2-5mm, 10-20% of active carbon particles with the particle size of 0.5-2mm, 30-50% of aluminum particles with the particle size of 2-5mm, 10-20% of carbon particles with the particle size of 0.5-2mm, 10-20% of carbon particles with the particle size of 2-5mm, 10-20% of carbon particles with the particle size of 2- and the binder accounts for 2%-3%. The invention also discloses a preparation method and a use method thereof. The invention aims to provide the rare earth composite deoxidizer suitable for the aluminum deoxidation and sedation tapping process and the preparation and use methods thereof, and aims to realize a deoxidation mode which is low in cost, few in deoxidation product and capable of ensuring the safety and stability of the production process.

Description

Technical Field

[0001] The present invention belongs to the technical field of steelmaking, and particularly relates to a rare earth composite deoxidizer applicable to the aluminum deoxidation and calm tapping process, and its preparation and usage methods. Background Art

[0002] Aluminum deoxidation is one of the most commonly used methods for steelmaking deoxidation at present. Its principle is to add aluminum elements to the molten steel during the tapping process of the converter, so that the oxygen in the molten steel reacts chemically with aluminum to form aluminum oxides, thereby achieving the purpose of deoxidation. Aluminum deoxidation has the advantages of easy operation and good deoxidation effect, but the price of aluminum elements is relatively high, resulting in a corresponding increase in the smelting cost, and it is easy to generate hard alumina inclusions, which directly affects the cleanliness of the molten steel and the performance and quality of the products; the principle of rare earth deoxidation is to use the active electron clouds in rare earth elements to absorb oxygen in metal materials, thereby forming unstable oxides and separating from the metal materials. Its advantages are good deoxidation effect, relatively small size of deoxidation products compared with alumina, and similar elastic modulus to steel, but its addition process and control conditions are demanding. The stability of the recovery rate of rare earth added to steel, the continuous casting property during the production process, and the uniformity of its distribution in steel are the main bottleneck problems that prevent its mass industrial production; the principle of carbon deoxidation is to add carbon powder to the high-temperature molten steel to react with the oxygen in the steel to generate carbon dioxide gas and escape, thereby achieving the deoxidation effect. Its advantages are extremely low cost and the deoxidation products will not affect the quality of the steel. However, adding carbon powder from the upper part of the molten steel is easy to float on the surface of the molten steel due to its low density and cannot effectively deoxidize. And directly adding it to the bottom of the ladle during tapping also has the risk of violent carbon-oxygen concentration reaction and gas escape, which is easy to cause the molten steel to churn and overflow the ladle.

[0003] In summary, there is an urgent need for a deoxidation method that is both low-cost, has few deoxidation products, and ensures the safety and stability of the production process to meet the development needs of high-value-added and high-quality steel products. Summary of the Invention

[0004] The purpose of the present invention is to provide a rare earth composite deoxidizer applicable to the aluminum deoxidation and calm tapping process, and its preparation and usage methods, aiming to achieve a deoxidation method with low cost, few deoxidation products, and ensuring the safety and stability of the production process.

[0005] To solve the above technical problems, the present invention adopts the following technical solutions:

[0006] A rare earth composite deoxidizer applicable to the aluminum deoxidation and calm tapping process of the present invention, the weight percentage chemical components of the rare earth-aluminum-carbon composite deoxidizer include: rare earth ferroalloy particles with a particle size of 2-5 mm account for 30%-50%, activated carbon particles with a particle size of 0.5-2 mm account for 10%-20%, aluminum particles with a particle size of 2-5 mm account for 30%-50%, and the binder accounts for 2%-3%.

[0007] Further, the rare earth ferroalloy contains 50% of rare earth cerium.

[0008] Further, the binder includes epoxy resin and water.

[0009] Further, the mass ratio of the epoxy resin to water is 1:4.

[0010] The present invention also provides a preparation method of a rare earth composite deoxidizer applicable to the aluminum deoxidation and calm steel tapping process, which is characterized in that after the materials are mixed evenly, they are processed into balls / blocks with a size of 50-100 mm by a metal powder briquetting / pelletizing machine.

[0011] The present invention further provides a usage method of a rare earth composite deoxidizer applicable to the aluminum deoxidation and calm steel tapping process, which is characterized in that before use, the rare earth aluminum carbon composite deoxidizer balls / blocks are dried at a temperature of 50-200 °C for more than 2 hours, and are directly added to the molten steel in the ladle through a bunker during the tapping of the converter steel.

[0012] Specific addition method steps: After the converter smelting is completed, measure the oxygen content in the steel to calculate the dosage of the subsequent deoxidation alloy. To ensure the full reaction of the rare earth aluminum carbon composite deoxidizer with the molten steel, when the tapping amount of the converter molten steel reaches 1 / 3, start adding the rare earth aluminum carbon composite deoxidizer.

[0013] Compared with the prior art, the beneficial technical effects of the present invention are:

[0014] For the rare earth aluminum carbon composite deoxidizer of the present invention, rare earth alloy elements with strong affinity for oxygen are added, and it is easy to obtain deoxidation products with small particles, not easy to aggregate and grow, and dispersed in the steel, improving the morphology and properties of inclusions, having a beneficial impact on the product performance, and the deoxidation effect is better than that of the existing deoxidizer. At the same time, the ball / block-shaped rare earth aluminum carbon composite deoxidizer of the present invention has a certain specific gravity, can be dispersed and slowly enter the molten steel interior, and during the melting process of the deoxidizer, the carbon powder gradually reacts with the oxygen in the steel, and the carbon dioxide gas diffuses out evenly, solving the problems that the carbon powder has a light density and is easy to float on the surface of the molten steel and cannot effectively deoxidize, and directly putting it at the bottom of the ladle causes a violent and concentrated reaction, resulting in the risk of the molten steel boiling over the ladle. Description of the Drawings

[0015] The present invention will be further described below in conjunction with the drawings.

[0016] Figure 1 The inclusions in the steel sample of the conventional process are MnS, TiN with a size of about 8-10 μm and oxide inclusions containing Ca, Al, and Mg;

[0017] Figure 2 For the inclusions in the steel plate sample under the process of the present invention;

[0018] Figure 3 It is the metallographic structure of the finished steel plate. Specific implementation method

[0019] A rare earth-aluminum-carbon composite deoxidizer applicable to the killed steelmaking process and its preparation and use method aim to achieve a deoxidation method with low cost, few deoxidation products and ensure the safety and stability of the production process. The specific implementation method is as follows:

[0020] The weight percentage chemical composition formula and preparation method of the rare earth-aluminum-carbon composite deoxidizer include: rare earth ferroalloy particles with a particle size of 2-5 mm (containing 50% rare earth cerium in the alloy) accounting for 30%-50%, activated carbon particles with a particle size of 0.5-2 mm accounting for 10%-20%, aluminum particles with a particle size of 2-5 mm accounting for 30%-50%, and a binder accounting for 2%-3% (the mass ratio of epoxy resin to water is 1:4). After mixing the above materials evenly, they are processed into balls / blocks with a size of 50-100 mm by a metal powder briquetting / pelletizing machine.

[0021] The rare earth-aluminum-carbon composite deoxidizer of the present invention adds rare earth alloy elements with strong oxygen affinity, and it is easy to obtain deoxidation products with small particles, not easy to aggregate and grow, and dispersed in the steel, which improves the morphology and properties of inclusions and has a beneficial effect on the product performance. The deoxidation effect is better than that of the existing deoxidizers. At the same time, the ball / block rare earth-aluminum-carbon composite deoxidizer of the present invention has a certain specific gravity and can be dispersed and slowly enter the molten steel. During the melting process of the deoxidizer, the carbon powder gradually reacts with the oxygen in the steel, and the carbon dioxide gas diffuses out evenly, solving the problems that the carbon powder has a light density and is easy to float on the surface of the molten steel and cannot effectively deoxidize, and directly putting it at the bottom of the ladle causes a violent and concentrated reaction, resulting in the risk of the molten steel churning and overflowing the ladle.

[0022] The specific use method and process are as follows:

[0023] Before use, dry the ball / block of the rare earth-aluminum-carbon composite deoxidizer at a temperature of 50-200 °C for more than 2 hours, and add it directly to the molten steel in the ladle through a bunker during the deoxidation of the converter tapping. The specific addition method steps: After the converter smelting is completed, measure the oxygen content in the steel to calculate the dosage of the subsequent deoxidation alloy. To ensure the full reaction of the rare earth-aluminum-carbon composite deoxidizer with the molten steel, when the tapping amount of the converter molten steel reaches 1 / 3, start adding the rare earth-aluminum-carbon composite deoxidizer of the present invention. The specific calculation method of the addition amount is as follows:

[0024] Through batch tests and process use statistics, every 100 kg of the rare earth-aluminum-carbon composite deoxidizer under the conditions of a typical formula (ferroalloy particles containing 50% rare earth cerium accounting for 50%, activated carbon particles accounting for 10%, and aluminum particles accounting for 40%) can achieve deoxidation of 320 ppm. The calculation process is as follows:

[0025] ① C + 2[O] = CO 2

[0026] Amount of O removed from steel: 100 kg × 20% × 32 / 14 = 45.7 kg;

[0027] Calculated based on 240 tons of molten steel per furnace, deoxidation of 191 ppm can be achieved.

[0028] ② 2Al + 3[O] = Al 2 O 3

[0029] Amount of O removed from steel: 100 kg × 30% × 48 / 54 = 26.7 kg;

[0030] Calculated based on 240 tons of molten steel per furnace, deoxidation of 111 ppm can be achieved.

[0031] ③ 2Ce + 3[O] = Ce 2 O 3

[0032] Amount of O removed from steel: 100 kg × 50% × 50% × 48 / 280 = 4.29 kg;

[0033] Calculated based on 240 tons of molten steel per furnace, deoxidation of 18 ppm can be achieved.

[0034] According to the requirements of aluminum content in the steel grade (0.030%) and without aluminum content requirements, and taking the typical converter volumes of 150 tons and 240 tons in the industry as the test objects and the on-site research results, the specific deoxidation scheme is determined as follows:

[0035] Table 1 Deoxidation scheme for steel with aluminum content requirement of 0.030%

[0036]

[0037] Table 2 Deoxidation scheme for steel without aluminum content requirement

[0038]

[0039] Table 3 Deoxidation scheme for steel with aluminum content requirement of 0.030%

[0040]

[0041]

[0042] Table 4 Deoxidation scheme for steel without aluminum content requirement

[0043]

[0044] After taking the above measures, the advantage of carbon deoxidation of the steel grade is exerted, achieving the replacement of traditional high-cost aluminum consumption and lower Al in the steel 2O 3 The effect of hard oxide inclusions realizes low-cost and high-efficiency deoxidation, and ensures the safe and stable production process. At the same time, the enhanced reducing rare earth is advanced to the converter process to remove harmful elements such as O and S in the steel, so that the rare earth modification products float to the slag as early as possible, reducing the bottleneck problem of nozzle clogging during the continuous casting process caused by adding rare earth at the end of traditional refining, and the bottleneck problem that the batch industrialization achievement transformation cannot be realized. The rare earth-aluminum-carbon composite deoxidizer of the formula of the present invention can largely form modification products in the form of rare earth aluminate that is closest to the elastic modulus of the steel, can effectively purify the molten steel, and play the effect of modifying inclusions. The rare earth-aluminum-carbon composite deoxidizer described in the present invention meets the development needs of high-value-added and high-quality steel products, and provides a new way for the further realization of the stable industrial trial production and large-scale production of rare earth steel.

[0045] Implementation Case 1:

[0046] A hot strip mill production line is matched with a converter with a volume of 240 tons. The chemical composition of the hot-rolled steel strip BT490CL steel grade for automotive structures manufactured is shown in Table 5 (the required aluminum content in the steel is 0.030%). The tapping temperature at the end of the converter is 1640 °C, and the oxygen content in the molten steel tapped from the converter is 600 ppm. Production trial comparisons of deoxidation effects are carried out by adding 230 kg of the rare earth-aluminum-carbon composite deoxidizer described in the present invention and a conventional aluminum iron alloy containing 70% aluminum.

[0047] Table 5 Chemical Composition Unit: %

[0048] Chemical element C Si Mn P S Nb Alt Target 0.080 0.03 0.90 0.015 0.003 0.040 0.030

[0049] The trial results show that: for the furnace using the rare earth-aluminum-carbon composite deoxidizer described in the present invention, the aluminum consumption per ton of steel is 2.4 kg / t, and the oxygen content detected in the produced steel plate is 29 ppm. For the furnace using a conventional aluminum iron alloy containing 70% aluminum, the aluminum consumption per ton of steel is 5.1 kg / t, and the oxygen content detected in the produced steel plate is 18 ppm. The implementation of the present invention significantly reduces the total amount of alumina inclusions in the steel, improves the cleanliness of the molten steel, and the casting process during continuous casting is stable, and there is no phenomenon of steel flocculation and pouring stoppage. The on-site use of the rare earth-aluminum-carbon composite deoxidizer described in the present invention further gives play to the stable diffusion deoxidation of carbon after the converter to replace the consumption of traditional high-cost aluminum materials, and the enhanced reducing rare earth intervenes in advance to remove harmful elements such as O and S in the steel. At the same time, it effectively solves the bottleneck problem that the rare earth modification products float to the slag as early as possible to reduce nozzle clogging during the later continuous casting process.

[0050] Implementation Case 2:

[0051] A hot strip rolling production line is matched with a converter with a volume of 240 tons, and adjacent heats of automotive beam steel BT610L (the required aluminum content in the steel is 0.030%) are produced in the same casting heat. The oxygen content in the molten steel tapped from the converter is 700 ppm. A production comparison test is carried out by implementing the process of the present invention (adding 265 kg of rare earth aluminum-carbon composite deoxidizer) and the conventional process. Except for adding rare earth, the other processes in the two schemes are exactly the same during the production process. The chemical composition of the finally produced steel grade is shown in Table 6, and the rare earth content in the steel after implementing the present invention is 17 ppm.

[0052] Table 6 Chemical composition of BT610L (Wt%)

[0053]

[0054] The main components of inclusions in the steel plate samples produced by the two processes were examined by scanning electron microscopy. The results show that the inclusions in the steel sample of the conventional process are MnS, TiN with a size of about 8 - 10 μm and oxide inclusions containing Ca, Al, and Mg (see Figure 1 ). Under the process of the present invention, the inclusions in the steel plate sample are metamorphosed and refined into inclusion compounds of rare earth Ce sulfur oxides with a size of about 2 - 5 μm, and the inclusion size is significantly reduced (see Figure 2 ).

[0055] The metallographic structures of the finished BT610L steel plates produced by the rare earth aluminum-carbon composite deoxidizer of the present invention and the conventional process were observed and compared. As Figure 3 shown, the structure and grains of the steel plate produced by implementing the production process of the present invention are more uniform and finer. The fine and uniform structure is beneficial to improving the strength and toughness of the steel plate.

[0056] The mechanical properties of the finished BT610L steel plates produced by the rare earth aluminum-carbon composite deoxidizer of the present invention and the conventional process were tested (Table 7). The results show that the tensile strength, yield strength, and elongation of the steel plate produced by implementing the present invention are all better than those of the steel plate produced by the conventional process.

[0057] Table 7 Mechanical properties of products under two process conditions

[0058]

[0059] The above-described embodiments are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solution of the present invention should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A rare earth composite deoxidizer suitable for aluminum deoxidation and steelmaking process, characterized in that: The chemical composition by weight percentage of the rare earth aluminum-carbon composite deoxidizer includes: 30%-50% of rare earth iron alloy particles with a particle size of 2-5mm, 10%-20% of activated carbon particles with a particle size of 0.5-2mm, 30%-50% of aluminum particles with a particle size of 2-5mm, and 2%-3% of a binder.

2. The rare earth composite deoxidizer for aluminum deoxidation and steelmaking process according to claim 1, characterized in that: The rare earth iron alloy contains 50% rare earth cerium.

3. The rare earth composite deoxidizer for aluminum deoxidation and steelmaking process according to claim 1, characterized in that: The adhesive includes epoxy resin and water.

4. The rare earth composite deoxidizer for aluminum deoxidation and steelmaking process according to claim 1, characterized in that: The mass ratio of the epoxy resin to water is 1:

4.

5. The method for preparing the rare earth composite deoxidizer for aluminum deoxidation and steelmaking process according to claim 1, characterized in that: After the materials are mixed evenly, they are processed into 50-100mm balls / lumps by a metal powder ball / block press.

6. The method for using the rare earth composite deoxidizer for aluminum deoxidation and steelmaking process according to claim 1, characterized in that: Before use, the rare earth aluminum carbon composite deoxidizer balls / lumps are dried at 50-200°C for more than 2 hours, and are directly added to the molten steel in the ladle through the silo during deoxidation of the converter.

7. The method for using the rare earth composite deoxidizer for aluminum deoxidation and steelmaking according to claim 6, characterized in that: Specific adding method and steps: after the converter smelting is completed, the oxygen content in the steel is measured to calculate the amount of subsequent deoxidation alloy. To ensure that the rare earth aluminum-carbon composite deoxidizer fully reacts with the molten steel, the rare earth aluminum-carbon composite deoxidizer is started to be added when the output of the converter molten steel reaches 1 / 3.

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