Steel for producing high-purity automobile sheet by electric arc furnace and method thereof

Abstract

The invention discloses high-purity steel for an automobile sheet produced by an electric arc furnace and a method thereof. The steel for the automobile sheet comprises the following chemical components in percentage by weight: less than or equal to 0.005% of C, less than or equal to 0.20% of Si, 0.75-1.00% of Mn, 0.050-0.080% of P, less than or equal to 0.015% of S, 0.020-0.035% of Al, 0.010-0.030% of Ti, 0.010-0.020% of Nb and the balance of Fe and inevitable impurity elements. The method comprises an electric furnace smelting process, an RH vacuum refining process and a continuous casting process. The high oxygen potential at the smelting end point of the electric arc furnace is fully utilized to provide favorable conditions for RH deep decarburization, secondary oxidation of the steel slag on the molten steel is inhibited, Al2O3 inclusions in the molten steel are remarkably reduced, the purity of the molten steel is greatly improved, and the electric arc furnace adopts the process of replacing molten iron with scrap steel for smelting, so that carbon emission is greatly reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of metallurgy, and particularly relates to a steel for high-purity automotive sheet produced by an electric arc furnace and a method therefor. Background Art

[0002] The steel for extra-deep drawing automotive sheet has excellent deep drawing performance and good non-aging properties, and is widely used in the automotive industry. The extra-deep drawing steel requires good surface quality and excellent deep drawing performance, which means that the molten steel produced must reach a high purity level. Currently, the production of steel for extra-deep drawing automotive sheet at home and abroad mostly adopts the long process of blast furnace and converter process, and there are few reports on the production of steel for automotive sheet by the short process of electric arc furnace. Based on the concept of low-carbon and environmental protection, electric arc furnace steelmaking, as a future development trend, adopts the process of blowing oxygen through the wall lance during smelting and adding strong deoxidizer aluminum particles and lime with large argon stirring during tapping. Since oxygen will transfer from the molten steel to the slag, the FeO content in the slag will increase. In addition, the more fully the lime reacts with the molten steel during tapping, the greater the increase in the FeO content in the slag, and the corresponding [O] content in the molten steel will be greatly reduced, which brings great difficulties to the subsequent RH deep decarburization. Moreover, the slag with high FeO will continuously cause "secondary oxidation" of the molten steel during continuous casting, resulting in an increase in Al 2 O 3 inclusions, which greatly affects the purity of the molten steel.

[0003] Therefore, how to take measures to control the purity of the molten steel in the modern electric arc furnace steelmaking process, so that the inclusion level in the products of the electric arc furnace process can reach a high level to meet the material usage requirements and improve the market competitiveness of the products of the electric arc furnace process is the key issue currently concerned in electric arc furnace steelmaking. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a steel for high-purity automotive sheet produced by an electric arc furnace and a method therefor. This method makes full use of the high oxygen potential at the end of electric arc furnace smelting to provide favorable conditions for RH deep decarburization, inhibits the "secondary oxidation" of the molten steel by the slag, and significantly reduces the Al 2 O 3 inclusions in the molten steel, greatly improving the purity of the molten steel.

[0005] To solve the above technical problems, the technical solution adopted by the present invention is: A steel for high-purity automotive sheet produced by an electric arc furnace, the chemical composition and its weight percentage of the steel for automotive sheet are: C ≤ 0.005%, Si ≤ 0.20%, Mn: 0.75 - 1.00%, P: 0.050 - 0.080%, S ≤ 0.015%, Al: 0.020 - 0.035%, Ti: 0.010 - 0.030%, Nb: 0.010 - 0.020%, and the rest are Fe and inevitable impurity elements.

[0006] The steel for automotive panel in the present invention has a yield strength ≥ 500 MPa, a tensile strength ≥ 780 MPa, and an elongation A 50 ≥ 28%.

[0007] The thickness of the steel for automotive panel in the present invention is 0.8 - 1.2 mm.

[0008] Another object of the present invention is to provide a method for producing high - purity steel for automotive panel by an electric arc furnace. The method includes an electric furnace smelting process, an RH vacuum refining process, and a continuous casting process; the electric furnace smelting process includes the following steps:

[0009] (1) During the tapping process after the electric furnace smelting is completed, the stirring flow rate of bottom - blown argon is adjusted to 50 - 80 NL / min;

[0010] (2) After tapping is completed, 4 - 8 kg / t of lime and 0.5 - 3 kg / t of modified refining slag are added into the ladle. The addition amount of lime of 4 - 8 kg / t means that the total addition amount of lime is calculated by adding 4 - 8 kg of lime per ton of molten steel; the addition amount of modified refining slag of 0.5 - 3 kg / t means that the total addition amount of modified refining slag is calculated by adding 0.5 - 3 kg of modified refining slag per ton of molten steel;

[0011] (3) After adding lime and modified refining slag, the stirring flow rate of bottom - blown argon is adjusted to 100 - 300 NL / min.

[0012] The RH vacuum refining process in the present invention: After the molten steel enters the station, the oxygen content is measured to be 400 - 550 ppm. Under high vacuum in RH, the molten steel has a net circulation of 8 - 20 min. Then the oxygen content of the molten steel is measured, and aluminum pellets are added under vacuum for final deoxidation according to the oxygen content in the molten steel until the oxygen content is below 5 ppm.

[0013] The RH vacuum refining process in the present invention: FeO in the steel slag ≤ 4.5%.

[0014] The continuous casting process in the present invention: During continuous casting, the tundish superheat is 10 - 30 °C, the casting speed is 0.8 - 1.65 m / min, the water flow rate in the mold is 4230 - 4280 NL / min, and the specific water ratio is 0.53 - 0.57 L / kg.

[0015] The chemical composition and its weight percentage of the continuous casting billet obtained by the continuous casting process in the present invention are: C ≤ 0.005%, Si ≤ 0.20%, Mn: 0.75 - 1.00%, P: 0.050 - 0.080%, S ≤ 0.015%, Al: 0.020 - 0.035%, Ti: 0.010 - 0.030%, Nb: 0.010 - 0.020%, and the rest are Fe and inevitable impurity elements.

[0016] The electric furnace smelting process of the present invention: The main chemical components of the modified refining slag are as follows: Al: 45 - 47%, Al 2 O 3 : 7 - 8%, CaO: 24 - 26%, CaF 2 : 5 - 7.5%, SiO 2 : 3 - 4.5%, MgO: 2 - 4%.

[0017] The method of the present invention uses an electric arc furnace to produce green steel materials. During the tapping process of the electric furnace, the bottom blowing argon stirring is controlled at a low flow rate. After tapping, lime and modified refining slag are added, and the bottom blowing argon flow rate is adjusted to spread the lime and modified refining slag. This significantly inhibits the reaction between the molten steel and the steel slag during the RH decarburization period. After the decarburization period ends and aluminum is added for deoxidation, the dissolved [O] in the molten steel drops to about 0.00015%, and [O] will no longer be transferred to the steel slag. A large amount of deoxidation product Al 2 O 3 enters the steel slag. Therefore, the "secondary oxidation" of the molten steel by the steel slag is inhibited, and the Al 2 O 3 inclusions in the molten steel are significantly reduced, greatly improving the purity of the molten steel

[0018] The beneficial effects of adopting the above technical solutions are as follows: 1. The present invention makes full use of the advantage of high oxygen potential at the end of the electric arc furnace smelting, ensuring a high [O] content in the molten steel before the RH enters the station, providing good conditions for the full reaction of C - O during the RH vacuum process, and promoting the effective floating of inclusions. 2. The present invention reduces the entry of the product FeO of the Fe - O reaction into the steel slag (FeO in the slag ≤ 4.5%), reduces the secondary oxidation of the molten steel during the continuous casting process, effectively controls the blockage of the flocculent substances in the continuous casting nozzle, and improves the purity of the molten steel. 3. The amount of steel slag in the present invention is controlled to a certain extent, reducing the addition amount of lime and deoxidizer, and lowering the smelting cost. 4. The electric arc furnace of the present invention uses scrap steel instead of hot metal for smelting, greatly reducing carbon emissions and providing technical support for the green and low - carbon development of the steel industry. Description of the Drawings

[0019] Figure 1 It is the morphology diagram of the nozzle after casting in Example 4;

[0020] Figure 2 It is the morphology diagram of the nozzle after casting in Example 8;

[0021] Figure 3 It is the morphology diagram of the nozzle after casting in Comparative Example 2. Detailed Embodiments

[0022] In order to make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention will be further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0023] Example 1

[0024] A method for producing high-purity steel for automotive sheets by an electric arc furnace, including an electric furnace smelting process, an RH vacuum refining process, and a continuous casting process; the specific control parameters are as follows:

[0025] 1) The electric furnace smelting process includes the following steps:

[0026] (1) During the tapping process after the electric furnace smelting is completed, the bottom blowing argon stirring flow rate is adjusted to 59 NL / min;

[0027] (2) After tapping is completed, 4.0 kg / t of lime and 1.2 kg / t of modified refining slag are added to the ladle;

[0028] (3) After adding lime and modified refining slag, adjust the bottom blowing argon stirring flow rate to 184 NL / min; the main chemical components of the modified refining slag are as follows: Al: 46.17%, Al 2 O 3 : 7.92%, CaO: 25.83%, CaF 2 : 6.91%, SiO 2 : 4.05%, MgO: 3.25% (the refining slag components in the other examples are the same).

[0029] 2) RH vacuum refining process: After the molten steel enters the station, the oxygen content is measured to be 420 ppm. After the molten steel undergoes a net circulation of 8 minutes under high vacuum in RH, the oxygen content in the molten steel is measured to be 169 ppm. According to the oxygen content, 52 kg of aluminum pellets are added under vacuum for final deoxidation until the oxygen content reaches 5 ppm.

[0030] 3) Continuous casting process: During continuous casting, the tundish superheat is 30 °C, the casting speed is 0.8 m / min, the mold water flow rate is 4230 NL / min, and the specific water quantity is 0.55 L / kg.

[0031] Example 2

[0032] A method for producing high-purity steel for automotive sheets by an electric arc furnace, including an electric furnace smelting process, an RH vacuum refining process, and a continuous casting process; the specific control parameters are as follows:

[0033] 1) The electric furnace smelting process includes the following steps:

[0034] (1) During the tapping process after the electric furnace smelting is completed, the bottom blowing argon stirring flow rate is adjusted to 63 NL / min;

[0035] (2) After tapping, add 4.8 kg / t of lime and 0.9 kg / t of modified refining slag into the ladle;

[0036] (3) After adding lime and modified refining slag, adjust the bottom-blowing argon stirring flow rate to 213 NL / min.

[0037] 2) RH vacuum refining process: After the molten steel enters the station, measure the oxygen content at 452 ppm. After 9 minutes of net circulation of the molten steel under high vacuum in RH, measure the oxygen content in the molten steel at 177 ppm. According to the oxygen content, add 54 kg of aluminum pellets under vacuum for final deoxidation until the oxygen content reaches 3 ppm.

[0038] 3) Continuous casting process: During continuous casting, the tundish superheat is 19 °C, the casting speed is 1.35 m / min, the mold water flow rate is 4240 NL / min, and the specific water ratio is 0.53 L / kg.

[0039] Example 3

[0040] A method for producing high-purity steel for automotive sheets by an electric arc furnace, including an electric furnace smelting process, an RH vacuum refining process, and a continuous casting process; the specific control parameters are as follows:

[0041] 1) Electric furnace smelting process, including the following steps:

[0042] (1) During tapping after electric furnace smelting is completed, adjust the bottom-blowing argon stirring flow rate to 69 NL / min;

[0043] (2) After tapping, add 5.1 kg / t of lime and 2.2 kg / t of modified refining slag into the ladle;

[0044] (3) After adding lime and modified refining slag, adjust the bottom-blowing argon stirring flow rate to 100 NL / min.

[0045] 2) RH vacuum refining process: After the molten steel enters the station, measure the oxygen content at 400 ppm. After 11 minutes of net circulation of the molten steel under high vacuum in RH, measure the oxygen content in the molten steel at 198 ppm. According to the oxygen content, add 60 kg of aluminum pellets under vacuum for final deoxidation until the oxygen content reaches 2 ppm.

[0046] 3) Continuous casting process: During continuous casting, the tundish superheat is 10 °C, the casting speed is 1.25 m / min, the mold water flow rate is 4242 NL / min, and the specific water ratio is 0.55 L / kg.

[0047] Example 4

[0048] A method for producing high-purity steel for automotive sheets by an electric arc furnace, including an electric furnace smelting process, an RH vacuum refining process, and a continuous casting process; the specific control parameters are as follows:

[0049] 1) Electric furnace smelting process, including the following steps:

[0050] (1) During the tapping process after the electric furnace smelting is completed, the stirring flow rate of bottom-blown argon is adjusted to 80 NL / min;

[0051] (2) After tapping is completed, 6.5 kg / t of steel of lime and 2.8 kg / t of steel of modified refining slag are added into the ladle;

[0052] (3) After adding lime and modified refining slag, the stirring flow rate of bottom-blown argon is adjusted to 212 NL / min.

[0053] 2) RH vacuum refining process: After the molten steel enters the station, the oxygen content is measured to be 458 ppm. After the molten steel has a net circulation of 20 min under high vacuum in RH, the oxygen content in the molten steel is measured to be 184 ppm. According to the oxygen content, 56 kg of aluminum pellets are added under vacuum for final deoxidation until the oxygen content reaches 4 ppm.

[0054] 3) Continuous casting process: During continuous casting, the ladle superheat is 28 °C, the casting speed is 1.10 m / min, the water flow rate in the mold is 4280 NL / min, and the specific water ratio is 0.54 L / kg.

[0055] Example 5

[0056] A method for producing high-purity automotive sheet steel by an electric arc furnace, including an electric furnace smelting process, an RH vacuum refining process, and a continuous casting process; the specific control parameters are as follows:

[0057] 1) Electric furnace smelting process, including the following steps:

[0058] (1) During the tapping process after the electric furnace smelting is completed, the stirring flow rate of bottom-blown argon is adjusted to 75 NL / min;

[0059] (2) After tapping is completed, 6.1 kg / t of steel of lime and 1.9 kg / t of steel of modified refining slag are added into the ladle;

[0060] (3) After adding lime and modified refining slag, the stirring flow rate of bottom-blown argon is adjusted to 300 NL / min.

[0061] 2) RH vacuum refining process: After the molten steel enters the station, the oxygen content is measured to be 513 ppm. After the molten steel has a net circulation of 17 min under high vacuum in RH, the oxygen content in the molten steel is measured to be 202 ppm. According to the oxygen content, 62 kg of aluminum pellets are added under vacuum for final deoxidation until the oxygen content reaches 5 ppm.

[0062] 3) Continuous casting process: During continuous casting, the ladle superheat is 23 °C, the casting speed is 1.65 m / min, the water flow rate in the mold is 4255 NL / min, and the specific water ratio is 0.56 L / kg.

[0063] Example 6

[0064] A method for producing high-purity steel for automotive sheets by an electric arc furnace, including an electric furnace smelting process, an RH vacuum refining process, and a continuous casting process; the specific control parameters are as follows:

[0065] 1) The electric furnace smelting process includes the following steps:

[0066] (1) During the tapping process after the electric furnace smelting is completed, the bottom blowing argon stirring flow rate is adjusted to 69 NL / min;

[0067] (2) After tapping is completed, 4.7 kg / t of steel of lime and 0.5 kg / t of steel of modified refining slag are added into the ladle;

[0068] (3) After adding lime and modified refining slag, the bottom blowing argon stirring flow rate is adjusted to 188 NL / min.

[0069] 2) The RH vacuum refining process: After the molten steel enters the station, the oxygen content is measured to be 433 ppm. After the molten steel has a net circulation of 12 min under high vacuum in RH, the oxygen content in the molten steel is measured to be 179 ppm. According to the oxygen content, 55 kg of aluminum pellets are added under vacuum for final deoxidation until the oxygen content reaches 3 ppm.

[0070] 3) The continuous casting process: During continuous casting, the ladle superheat is 16 °C, the casting speed is 1.25 m / min, the mold water flow rate is 4262 NL / min, and the specific water ratio is 0.55 L / kg.

[0071] Example 7

[0072] A method for producing high-purity steel for automotive sheets by an electric arc furnace, including an electric furnace smelting process, an RH vacuum refining process, and a continuous casting process; the specific control parameters are as follows:

[0073] 1) The electric furnace smelting process includes the following steps:

[0074] (1) During the tapping process after the electric furnace smelting is completed, the bottom blowing argon stirring flow rate is adjusted to 73 NL / min;

[0075] (2) After tapping is completed, 4.2 kg / t of steel of lime and 3.0 kg / t of steel of modified refining slag are added into the ladle;

[0076] (3) After adding lime and modified refining slag, the bottom blowing argon stirring flow rate is adjusted to 191 NL / min.

[0077] 2) The RH vacuum refining process: After the molten steel enters the station, the oxygen content is measured to be 492 ppm. After the molten steel has a net circulation of 15 min under high vacuum in RH, the oxygen content in the molten steel is measured to be 195 ppm. According to the oxygen content, 60 kg of aluminum pellets are added under vacuum for final deoxidation until the oxygen content reaches 4 ppm.

[0078] (3) Continuous casting process: During continuous casting, the tundish superheat is 22°C, the casting speed is 1.20 m / min, the mold water flow rate is 4258 NL / min, and the specific water ratio is 0.57 L / kg.

[0079] Example 8

[0080] A method for producing high-purity steel for automotive sheets by an electric arc furnace, including an electric furnace smelting process, an RH vacuum refining process, and a continuous casting process; the specific control parameters are as follows:

[0081] (1) Electric furnace smelting process, including the following steps:

[0082] (1) During the tapping process after the electric furnace smelting is completed, the bottom blowing argon stirring flow rate is adjusted to 50 NL / min;

[0083] (2) After tapping is completed, 8.0 kg / t of lime and 1.4 kg / t of modified refining slag are added to the ladle;

[0084] (3) After adding lime and modified refining slag, the bottom blowing argon stirring flow rate is adjusted to 176 NL / min.

[0085] (2) RH vacuum refining process: After the molten steel enters the station, the oxygen content is measured to be 550 ppm. After the molten steel has a net circulation of 16 min under high vacuum in RH, the oxygen content in the molten steel is measured to be 188 ppm. According to the oxygen content, 57 kg of aluminum pellets are added under vacuum for final deoxidation until the oxygen content reaches 2 ppm.

[0086] (3) Continuous casting process: During continuous casting, the tundish superheat is 12°C, the casting speed is 1.30 m / min, the mold water flow rate is 4270 NL / min, and the specific water ratio is 0.53 L / kg.

[0087] Comparative Example 1

[0088] A method for producing high-purity steel for automotive sheets by an electric arc furnace, including an electric furnace smelting process, an RH vacuum refining process, and a continuous casting process; the specific control parameters are as follows:

[0089] (1) Electric furnace smelting process, including the following steps:

[0090] (1) During the tapping process, 6.2 kg / t of lime and 2.5 kg / t of metallic aluminum pellet deoxidizer are added;

[0091] (2) During the tapping process, the bottom blowing argon stirring flow rate is adjusted to 62 NL / min, and the lime and deoxidizer are spread out.

[0092] (2) RH vacuum refining process: After the molten steel enters the station, the oxygen content is measured to be 314 ppm. After the molten steel has a net circulation of 12 min under high vacuum in RH, the oxygen content in the molten steel is measured to be 156 ppm. According to the oxygen content, 80 kg of aluminum pellets are added under vacuum for final deoxidation.

[0093] 3) Continuous casting process: During continuous casting, the tundish superheat is 21°C, the casting speed is 1.20 m / min, the mold water flow rate is 4265 NL / min, and the specific water ratio is 0.54 L / kg.

[0094] Comparative Example 2

[0095] A method for producing high-purity steel for automotive sheets by an electric arc furnace, including an electric furnace smelting process, an RH vacuum refining process, and a continuous casting process; the specific control parameters are as follows:

[0096] 1) Electric furnace smelting process, including the following steps:

[0097] (1) During tapping, 5.8 kg / t of lime and 2.1 kg / t of modified refining slag are added;

[0098] (2) Subsequently, during tapping, the bottom-blowing argon stirring flow rate is adjusted to 78 NL / min, and the lime and refining slag are spread out.

[0099] 2) RH vacuum refining process: After the molten steel enters the station, the oxygen content is measured to be 356 ppm. After 15 minutes of net circulation of the molten steel under high vacuum in RH, the oxygen content in the molten steel is measured to be 161 ppm, and 70 kg of aluminum pellets are added under vacuum for final deoxidation.

[0100] 3) Continuous casting process: During continuous casting, the tundish superheat is 27°C, the casting speed is 1.15 m / min, the mold water flow rate is 4274 NL / min, and the specific water ratio is 0.56 L / kg.

[0101] For Examples 1-8 and Comparative Examples 1 and 2, a full-process oxygen determination analysis was carried out in the RH vacuum refining process, and the specific results are shown in Table 1 below. For Examples 1-8 and Comparative Examples 1 and 2, during continuous casting, a ladle sampler was used to extract molten steel samples in the tundish and processed into high-magnification analysis samples (5 groups of samples for each example). An ASPEX scanning electron microscope with automatic scanning, analysis, and statistical functions was used to analyze and measure the non-metallic inclusions in the samples. The scanning inspection area for each sample is 200 mm 2 , and the specific results are shown in Table 2 below; the chemical composition of the steel plates obtained in Examples 1-8 and Comparative Examples 1 and 2 (same as the continuous casting billets) is shown in Table 3, and the specifications and properties of the steel plates are shown in Table 4.

[0102] Table 1 Full-process oxygen determination analysis results of Examples 1-8 and Comparative Examples 1 and 2 in the RH vacuum refining process

[0103]

[0104]

[0105] Table 2 Analysis and measurement results of non-metallic inclusions in Examples 1-8 and Comparative Examples 1 and 2

[0106]

[0107] Examples 4, 8 and Comparative Example 2 are the heats with the tundish nozzle replaced. Figure 1 、 Figure 2 、 Figure 3 They respectively represent the nozzle morphologies after the casting of Example 4, Example 8 and Comparative Example 2 (the nozzles were replaced after producing 4 heats). It can be seen from the figure that compared with Comparative Example 2, the flocculent tumors on the nozzles of Example 4 and Example 8 have been significantly improved.

[0108] Compared with Comparative Examples 1 and 2, after the electric arc furnace smelting in Examples 1 - 8, a high [O] content in the molten steel was ensured before entering RH, providing good conditions for the full reaction of C - O during the RH vacuum process, promoting the floating of inclusions into the slag; reducing the secondary oxidation of the molten steel during continuous casting, effectively controlling the blockage of flocculent tumors in the continuous casting nozzle, and improving the purity of the molten steel; the amount of slag was controlled to a certain extent, reducing the addition amount of deoxidizer aluminum pellets, and reducing the smelting cost; greatly reducing carbon emissions, providing technical support for the green and low - carbon development of the iron and steel industry.

[0109] Table 3 Chemical compositions of the steel plates obtained in Examples 1 - 8 and Comparative Examples 1 and 2 (%)

[0110] Serial number C Si Mn P S Al Ti Nb Example 1 0.0043 0.15 0.84 0.050 0.010 0.020 0.015 0.010 Example 2 0.0045 0.20 0.75 0.065 0.012 0.025 0.017 0.015 Example 3 0.0050 0.19 0.89 0.070 0.009 0.033 0.030 0.013 Example 4 0.0049 0.12 0.92 0.080 0.015 0.022 0.028 0.018 Example 5 0.0038 0.14 0.95 0.074 0.013 0.035 0.024 0.014 Example 6 0.0030 0.17 0.97 0.058 0.008 0.028 0.022 0.016 Example 7 0.0041 0.16 1.00 0.069 0.005 0.030 0.010 0.017 Example 8 0.0035 0.13 0.88 0.73 0.007 0.021 0.019 0.020 Comparative example 1 0.0049 0.12 0.92 0.080 0.015 0.022 0.028 0.018 Comparative example 2 0.0038 0.14 0.95 0.074 0.013 0.035 0.024 0.014

[0111] Table 4 Specifications and properties of the steel plates obtained in Examples 1 - 8 and Comparative Examples 1 and 2

[0112]

[0113] The above - mentioned examples are only used to illustrate rather than limit the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above - mentioned examples, those of ordinary skill in the art should understand that: the present invention can still be modified or equivalently replaced, and any modification or partial replacement without departing from the spirit and scope of the present invention should be covered by the scope of the claims of the present invention.

Claims

1. An electric arc furnace for producing high-purity steel for automobile plates, characterized in that: The chemical composition and weight percentage of the steel for automobile plates are: C≤0.005%, Si≤0.20%, Mn: 0.75-1.00%, P: 0.050-0.080%, S≤0.015%, Al: 0.020-0.035%, Ti: 0.010-0.030%, Nb: 0.010-0.020%, and the rest are Fe and unavoidable impurity elements.

2. The method of producing high purity automobile sheet steel by an electric arc furnace according to claim 1, characterized in that: The yield strength of the automobile steel sheet is ≥500MPa, the tensile strength is ≥780MPa, and the elongation is A 50 ≥28%.

3. The electric arc furnace for producing high purity automobile sheet steel according to claim 1 or 2, characterized in that: The automobile plate steel is 0.8-1.2 mm.

4. A method for producing high-purity steel for automobile sheets using an electric arc furnace according to any one of claims 1 to 3, characterized in that: The method comprises an electric furnace smelting process, an RH vacuum refining process, and a continuous casting process; the electric furnace smelting process comprises the following steps: (1) During the steelmaking process after the electric furnace smelting is completed, the bottom blowing argon stirring flow rate is adjusted to 50-80 NL / min; (2) After steel tapping is completed, add 4-8 kg / t of lime and 0.5-3 kg / t of modified refined slag into the ladle; (3) After adding lime and reforming refined slag, adjust the bottom blowing argon stirring flow rate to 100-300 NL / min.

5. The method for producing high-purity steel for automobile sheets by electric arc furnace according to claim 4, characterized in that: The RH vacuum refining process: after the molten steel enters the station, the oxygen content is measured at 400-550ppm, the molten steel is circulated for 8-20min under RH high vacuum, the oxygen content in the molten steel is measured, and then aluminum particles are added under vacuum according to the oxygen content in the molten steel for final deoxidation to an oxygen content of less than 5ppm.

6. The method for producing high-purity steel for automobile sheets by electric arc furnace according to claim 4, characterized in that: The RH vacuum refining process: FeO in the steel slag is ≤4.5%.

7. A method for producing high-purity steel for automobile sheets in an electric arc furnace according to any one of claims 4 to 6, characterized in that: The continuous casting process includes: an overheating temperature of 10 to 30° C., a pulling speed of 0.8 to 1.65 m / min, a crystallizer water flow rate of 4230 to 4280 NL / min, and a specific water volume of 0.53 to 0.57 L / kg.

8. A method for producing high-purity steel for automobile sheets in an electric arc furnace according to any one of claims 4 to 6, characterized in that: The chemical composition and weight percentage of the continuous casting billet obtained in the continuous casting process are: C≤0.005%, Si≤0.20%, Mn: 0.75-1.00%, P: 0.050-0.080%, S≤0.015%, Al: 0.020-0.035%, Ti: 0.010-0.030%, Nb: 0.010-0.020%, and the rest are Fe and unavoidable impurity elements.

9. A method for producing high-purity steel for automobile sheets in an electric arc furnace according to any one of claims 4 to 6, characterized in that: The electric furnace smelting process: the main chemical components of the modified refined slag are as follows: Al: 45-47%, Al2O3: 7-8%, CaO: 24-26%, CaF2: 5-7.5%, SiO2: 3-4.5%, MgO: 2-4%.

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