Coated substrate 1 gpa hot-formed steel phs and method of smelting thereof

Abstract

The application discloses a plated substrate 1GPa hot forming steel PHS and a smelting method thereof. The method comprises the following steps: S1, vanadium extraction is performed on molten iron raw material, and desulfurization pretreatment is performed to obtain semi-steel; S2, the semi-steel is added into a converter to perform oxygen blowing decarburization treatment; S3, a platform system is used to carry a ladle containing molten steel into an argon blowing station, and Al-Mg wire is fed into the molten steel to perform supplementary deoxidization; S4, an LF process and an RH process are sequentially performed to perform alloy fine adjustment treatment and remove inclusions; S5, the argon blowing station is entered, and Ca-Al wire is fed into the molten steel after the alloy fine adjustment treatment; and S6, a continuous casting process is performed to obtain the hot forming steel PHS. The method is easy to control inclusions, and high-quality and high-cleanliness hot forming steel PHS can be obtained.

Description

Technical Field

[0001] This invention belongs to the field of steel production technology, and specifically relates to a 1GPa hot-formed steel PHS with a coated substrate and its smelting method. Background Technology

[0002] Hot-formed steel sheets have significant market potential in commercial vehicles. Press-hardened steels (PHS), such as PHS1000 and PHS1500, are high-strength hot-formed steels with substantial deformation during subsequent rolling, thus placing high demands on the base material. However, conventional metal deoxidation methods produce numerous deoxidation products, making it difficult to control inclusions.

[0003] Furthermore, existing hot-formed steel processes often employ deoxidation using single-piece metals such as aluminum during smelting. On one hand, bulk aluminum has a low density and quickly floats to the surface of molten steel, reacting with oxygen in the air, resulting in low utilization. On the other hand, the large quantity of bulk aluminum added at once leads to a violent reaction, easily causing blowouts and posing significant safety hazards. CN101078034A discloses a magnesium-aluminum alloy cored wire that fully utilizes the high solubility of Mg in molten iron, employing Mg-containing and gold-containing composite deoxidation and wire feeding technology to achieve deoxidation of molten steel. The magnesium-aluminum alloy cored wire of this invention has the following chemical composition by mass percentage: Mg 5-13%, Al 11-14%, with the balance being Fe and unavoidable impurities. During steelmaking, the magnesium-aluminum alloy cored wire is inserted into the molten steel using a wire feeding machine. The addition of magnesium reduces the oxygen content in the steel, further refines inclusions, and solves problems related to steel cleanliness. However, magnesium-aluminum alloy cored wires use Fe as the main element, with low Mg and Al content, resulting in low deoxidation efficiency. Because the core of the wire is made of magnesium-aluminum alloy powder, it is prone to breakage during feeding. Furthermore, the powder reacts more rapidly, causing more intense splashing during on-site feeding, which affects construction safety.

[0004] Therefore, designing an easily controllable stamping hardening steel smelting method has important practical significance. Summary of the Invention

[0005] To address the existing technical problems, this invention proposes a 1GPa hot-formed steel PHS with a coated substrate and its smelting method.

[0006] According to the present invention, a method for smelting 1GPa hot-formed steel PHS with a coated substrate is provided, comprising the following steps: S1, vanadium extraction and desulfurization pretreatment of raw iron to obtain semi-steel; S2, adding the semi-steel to a converter for oxygen blowing decarburization treatment, and tapping the semi-steel into molten steel with a C content of 0.05~0.08 wt.%, wherein calcium carbide deoxidation is used during tapping, and the oxygen activity after deoxidation is controlled to be 50~100 ppm, wherein the calcium carbide contains ≥95 wt.% calcium carbide; S3, using a platform system to transport a ladle containing molten steel into an argon blowing station, feeding Al-Mg wire into the molten steel for supplemental deoxidation, with a target Al content of 0.040±0.010 wt.% in the molten steel, and the wire feeding speed controlled to be 3~5 m / s, wherein the Al-Mg wire contains 20~25% calcium carbide. S4, perform the LF and RH processes sequentially to fine-tune the alloy and remove inclusions; S5, feed the molten steel into the argon blowing station and introduce a Ca-Al wire; and S6, perform a continuous casting process to obtain a hot-formed steel PHS product with the following composition: C 0.10~0.13 wt.%, Si 0.15~0.25 wt.%, Mn 1.40~1.60 wt.%, P ≤0.015 wt.%, S ≤0.002 wt.%, Als 0.030~0.050 wt.%, Nb 0.015~0.030 wt.%, Cr 0.25~0.35 wt.%, Ti 0.025~0.035 wt.%, N ≤0.0040 wt.%, B 0.0025~0.0035 wt.%. wt.%, balance is Fe and unavoidable impurities.

[0007] According to one embodiment of the present invention, in step S1, the C content of the raw material molten iron is ≥4.0 wt.%, and the residual element content satisfies: Cu ≤0.10 wt.%, Mo ≤0.05 wt.%, Ni ≤0.10 wt.%, Sn ≤0.03 wt.%, As ≤0.01 wt.%.

[0008] According to one embodiment of the present invention, in step S1, the composition of the semi-steel satisfies: C 3.4~4.0 wt.%, Mn 0.02~0.05 wt.%, P 0.05~0.08 wt.%, S ≤0.003 wt.%.

[0009] According to one embodiment of the present invention, in step S2, during the converter charging stage, S ≤ 0.001 wt.%; the converter is argon-blown throughout the tapping process, and after 2 / 3 of the steel is tapped, lime is added at a rate of 3~5 kg per ton of steel; when the steel composition meets P ≤ 0.010 wt.%, S ≤ 0.005 wt.%, and the temperature ≥ 1665 ℃, the thick slag is started to be tapped into the ladle; after tapping, 6~8 kg / ton of top slag modifier is added to the slag surface.

[0010] According to one embodiment of the present invention, the top slag modifier is a calcium-based top slag modifier with the following composition: CaC 230~50 wt.%, Al2O3 10~30 wt.%, CaO 20~40 wt.%, CaF 28~15 wt.%, S≤0.2 wt.%, P≤0.1 wt.%, and the remainder being unavoidable impurities.

[0011] According to one embodiment of the present invention, in step S4, the target chemical composition of the LF process is: C 0.10±0.01 wt.%, Si 0.18±0.05 wt.%, Mn 1.40±0.05 wt.%, P ≤0.015 wt.%, Cr 0.30±0.05 wt.%, Nb 0.022±0.005 wt.%, S ≤0.002 wt.%, Als 0.05±0.01 wt.%, with the balance being Fe and unavoidable impurities; the molten steel after the LF process is gently blown with a small argon flow rate for 3-5 minutes and then removed from the argon blowing station.

[0012] According to one embodiment of the present invention, in step S4, during the RH process, the RH is controlled to be ≤3 mbar and circulated for 10~15 min; the target chemical composition of the RH process is: C 0.12±0.01 wt.%, Si 0.20±0.05 wt.%, Mn 1.50±0.05 wt.%, P ≤0.015 wt.%, S ≤0.002 wt.%, Als 0.045±0.005 wt.%, N≤0.0035 wt.%, Cr 0.30±0.05 wt.%, Nb 0.022±0.005 wt.%, B 0.0030±0.0005 wt.%, with the balance being Fe and unavoidable impurities.

[0013] According to one embodiment of the present invention, in step S5, the feed rate of the Ca-Al wire is controlled to be 0.15~0.25 kg / t of molten steel; the wire feeding speed is controlled to be 4~6 m / s; after feeding the wire, the wire is gently blown with argon gas for 8~12 min and then removed from the argon blowing station.

[0014] According to one embodiment of the present invention, in step S6, the superheat of the molten steel in the continuous casting ladle is 20~35 ℃; peritectic steel is used for continuous casting, a small chamfered crystallizer is used, and light reduction is applied with a reduction of 3~5 mm; the target casting speed is 1.0~1.2 m / min, and constant speed casting is used in production.

[0015] According to one embodiment of the present invention, the hot-formed steel PHS is smelted by the above-described method.

[0016] By employing the above technical solution, this invention, compared with existing technologies, utilizes a composite deoxidation method using calcium carbide and magnesium-aluminum alloy wire, unlike conventional single-metal deoxidation methods using aluminum or iron. Since the deoxidation product of calcium carbide is gaseous CO or CO2, which is directly released into the air, this method can significantly reduce the amount of deoxidation products—inclusions—in the steel. Simultaneously, magnesium can combine with inclusions in the steel to form finer inclusions, reducing the impact of inclusions on the quality of the base material. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0018] The smelting method for 1GPa hot-formed steel PHS based on the present invention generally includes the following steps:

[0019] S1, vanadium extraction and desulfurization pretreatment of raw iron are used to obtain semi-steel;

[0020] S2 involves adding the semi-steel to a converter for oxygen decarburization treatment, initially refining the semi-steel into molten steel with a C content of 0.05~0.08 wt.%, and then tapping it. During tapping, calcium carbide deoxidation is used, controlling the oxygen activity after deoxidation to 50~100 ppm, wherein the calcium carbide in the calcium carbide is ≥95 wt.%.

[0021] S3. The platform system is used to transport the ladle containing molten steel into the argon blowing station. Al-Mg wire is fed into the molten steel to supplement deoxidation. The target is Als in the molten steel: 0.040±0.010 wt.%, and the feeding speed is controlled at 3~5 m / s. The Al-Mg wire contains 20~25 wt.% Mg and 75~80 wt.% Al.

[0022] S4, perform the LF process and the RH process in sequence to perform alloy fine-tuning and remove inclusions;

[0023] S5, enter the argon blowing station, and feed Ca-Al wire into the molten steel after alloy fine-tuning; and

[0024] S6, perform continuous casting process to obtain hot-formed steel PHS product with the following composition: C 0.10~0.13 wt.%, Si 0.15~0.25 wt.%, Mn 1.40~1.60 wt.%, P ≤0.015 wt.%, S ≤0.002 wt.%, Als 0.030~0.050 wt.%, Nb 0.015~0.030 wt.%, Cr 0.25~0.35 wt.%, Ti 0.025~0.035 wt.%, N ≤0.0040 wt.%, B 0.0025~0.0035 wt.%, balance being Fe and unavoidable impurities.

[0025] In some embodiments, the raw material used in step S1 preferably has a C content ≥ 4.0 wt.%, and the residual element content satisfies: Cu ≤ 0.10 wt.%, Mo ≤ 0.05 wt.%, Ni ≤ 0.10 wt.%, Sn ≤ 0.03 wt.%, As ≤ 0.01 wt.%. The semi-steel obtained after vanadium extraction and desulfurization pretreatment can satisfy the following composition: C 3.4~4.0 wt.%, Mn 0.02~0.05 wt.%, P 0.05~0.08 wt.%, S ≤ 0.003 wt.%. Alternatively, those skilled in the art can also control the content of participating elements such as Cu, Mo, Ni, Sn, and As in the semi-steel according to actual needs.

[0026] In some embodiments, in step S2, the converter smelting process is controlled to meet the following conditions: during the converter charging stage, S ≤ 0.001 wt.%; argon blowing is used throughout the converter tapping process, and lime is added at a rate of 3-5 kg ​​per ton of steel after 2 / 3 of the steel has been tapped; calcium carbide deoxidation is used during tapping, and the oxygen activity after deoxidation is controlled to be 50-100 ppm. The calcium carbide may contain 60-80 wt.% Al and 20-40 wt.% Fe. Because hot-formed steel PHS has high strength and undergoes significant deformation during subsequent rolling, it has very high requirements for the base material. Therefore, conventional metal deoxidation, due to its numerous deoxidation products, is unfavorable for inclusion control. Calcium carbide is used as the primary deoxidizer, and its products are mainly CO gas and CaO, which are easily removed from the molten steel. However, simple calcium carbide deoxidation is difficult to reduce the oxygen in the molten steel to an extremely low level below 10 ppm. Using calcium carbide alone to reduce oxygen to a low level would require a large amount of calcium carbide, resulting in extremely high costs. Meanwhile, because calcium carbide must be in excess, and the excess amount is relatively high, there is a high risk of "explosion" accidents in the later stages, posing a safety hazard. According to the embodiments of the present invention, combined with final deoxidation of magnesium-aluminum alloy wire, on the one hand, the resulting inclusions can be made finer, which is beneficial to improving the cleanliness of molten steel and improving the quality of the base material; on the other hand, compared with using calcium carbide alone, it can effectively reduce costs and improve safety.

[0027] Furthermore, when the molten steel composition meets the requirements of P≤0.010 wt.%, S≤0.005 wt.%, and temperature≥1665 ℃, thick slag is started to be tapped into the ladle; after tapping, 6~8 kg / ton of top slag modifier is added to the slag surface. The preferred top slag modifier is a calcium-based top slag modifier with the following composition: CaC2 30~50 wt.%, Al2O3 10~30 wt.%, CaO 20~40 wt.%, CaF2 8~15 wt.%, S≤0.2 wt.%, P≤0.1 wt.%, with the remainder being unavoidable impurities.

[0028] In some embodiments, during step S3, the ladle is continuously purged with argon, resulting in slag surface fluctuations but without the molten steel exposing the slag surface; the feeding speed is controlled at 3-5 m / s. Preferably, the Al-Mg alloy wire is specifically made from remelted aluminum and magnesium ingots and drawn, containing 20-25 wt.% Mg and 75-80 wt.% Al. On the one hand, compared to cored wires made from traditional aluminum-magnesium alloy powder, the aluminum and magnesium content in the Al-Mg wire of this invention is significantly increased, and the feeding process is less prone to breakage, making operation simpler. It also avoids the safety risks associated with the faster reaction rate of powders and the resulting violent splashing during on-site feeding. On the other hand, compared to the process of adding magnesium and aluminum block alloys, the feeding process of Al-Mg wire in this invention not only avoids the safety hazards of explosive spraying during deoxidation due to the large amount of magnesium and aluminum added at once and the violent reaction, but also allows direct feeding into the molten steel, preventing the situation where magnesium and aluminum block alloys, due to their low density, float on the surface of the molten steel and react with oxygen in the air, resulting in high overall utilization.

[0029] The LF (Ladle Refinishing Furnace) is a special refining vessel that typically employs submerged arc refining. Its main characteristics include: molten steel from the primary refining furnace is transferred to a ladle; electrodes are inserted into the slag above the molten steel in the ladle to generate an electric arc; synthetic slag is added to form a high-basicity white slag; and argon gas is used for stirring to maintain a strong reducing atmosphere in the ladle, thus performing submerged arc refining. Because argon stirring accelerates the chemical reaction between the slag and steel, and the electric arc heating provides temperature compensation, a longer refining time can be ensured. This reduces the oxygen and sulfur content in the steel, adsorbs inclusions to some extent, and achieves temperature regulation. The LF process is complete once the target chemical composition is achieved. In some embodiments, in step S4, the target chemical composition of the LF process is: C 0.10±0.01 wt.%, Si 0.18±0.05 wt.%, Mn 1.40±0.05 wt.%, P ≤0.015wt.%, Cr 0.30±0.05 wt.%, Nb 0.022±0.005 wt.%, S ≤0.002 wt.%, Als 0.05±0.01wt.%, with the balance being Fe and unavoidable impurities; the molten steel after the LF process is gently blown with a small argon flow rate for 3-5 minutes and then removed from the argon blowing station.

[0030] The Rh (Ruhstahl hausen Process) is a vacuum degassing method in steelmaking. It utilizes two refractory tubes inserted into the molten steel at the bottom of a vacuum ladle, one of which is purged with argon gas. This creates a density difference in the molten steel within the two tubes, causing the molten steel to circulate between the ladle and the vacuum ladle, resulting in a degassing reaction. Rh treatment effectively removes inclusions. In some embodiments, during step S4, the RH process is controlled to ≤3 mbar and circulated for 10-15 min; the target chemical composition of the RH process is: C 0.12±0.01 wt.%, Si 0.20±0.05 wt.%, Mn 1.50±0.05 wt.%, P ≤0.015 wt.%, S ≤0.002 wt.%, Als 0.045±0.005 wt.%, N ≤0.0035 wt.%, Cr 0.30±0.05 wt.%, Nb 0.022±0.005 wt.%, B 0.0030±0.0005 wt.%, with the balance being Fe and unavoidable impurities.

[0031] In some embodiments, in step S5, the feed rate of the Ca-Al wire is controlled to be 0.15~0.25 kg / t of molten steel; the wire feeding speed is controlled to be 4~6 m / s; after feeding the wire, the wire is gently blown with argon gas for 8~12 min and then removed from the argon blowing station.

[0032] In some embodiments, in step S6, the superheat of the molten steel in the continuous casting ladle is 20~35 ℃; peritectic steel is used for continuous casting, a small chamfered crystallizer is used, and light reduction is applied with a reduction of 3~5 mm; the target casting speed is 1.0~1.2 m / min, and constant speed casting is preferred in production.

[0033] After the above steps, the hot-formed steel PHS product is finally obtained.

[0034] The following description is based on specific embodiments.

[0035] Example 1

[0036] The smelting method of the 1GPa hot-formed steel PHS for the coated substrate in this embodiment includes the following steps:

[0037] Step S1: The molten iron entering the steel mill has a C content of 4.21 wt.%, and residual elements of Cu: 0.051 wt.%, Mo: 0.024 wt.%, Ni: 0.041 wt.%, Sn: 0.025 wt.%, and As: 0.0062 wt.%. Using the above molten iron as raw material, the raw material molten iron is subjected to vanadium extraction and desulfurization pretreatment to obtain semi-steel. This semi-steel contains, by weight percentage, 3.56 wt.% C, 0.041 wt.% Mn, 0.062 wt.% P, 0.002 wt.% S, 0.03 wt.% V, and trace amounts of Cr, Si, and Ti. The residual elements are Cu: 0.061 wt.%, Mo: 0.025 wt.%, Ni: 0.041 wt.%, Sn: 0.024 wt.%, and As: 0.0061 wt.%. wt.%; the balance is iron and unavoidable impurities.

[0038] In step S2, 237.1 tons of the aforementioned semi-steel are added to a 220-ton (nominal capacity) top-and-bottom blown converter. The oxygen blowing and decarburization function of the converter is used to initially refine the semi-steel into molten steel. When the molten steel reaches a C content of 0.051 wt.%, a Mn content of 0.033 wt.%, a P content of 0.0087 wt.%, a S content of 0.0045 wt.%, and a temperature of 1679 ℃, the thick slag is started to be tapped into the ladle. Argon blowing is performed throughout the tapping process. After 2 / 3 of the steel has been tapped, 4 kg / t of active lime is added to the ladle for mixing. Calcium carbide is added for deoxidation during tapping, resulting in an oxygen content of 55 ppm. After tapping, 6 kg / t of calcium-based top slag modifier is added.

[0039] Step S3: The small platform enters the station to feed Al-Mg wire at a speed of 4 m / s, with a target Al content of 0.045 wt.% in the steel. The Al-Mg wire contains 23 wt.% Mg and 77 wt.% Al.

[0040] Step S4 involves sequentially performing the LF and RH processes to fine-tune the alloy and remove inclusions. Specifically,

[0041] Step S41, the chemical composition of the alloy after adjustment in the LF process is shown in Table 1:

[0042] Table 1. Composition of LF alloy after fine-tuning / wt.%

[0043]

[0044] Before leaving the station, the LF molten steel was gently blown with a small argon flow for 3 minutes. During the gentle blowing process, the molten steel was turned over and not exposed.

[0045] Step S42, RH≤3 mbar, cyclic processing time 10 min.

[0046] The chemical composition of the RH process is shown in Table 2:

[0047] Table 2 Chemical composition of RH process / wt.%

[0048]

[0049] Step S5: After the alloy fine-tuning treatment is completed, 0.15 kg / t of molten steel is fed into the Ca-Al wire. Before leaving the station, the molten steel is gently blown with a small argon flow rate for 8 minutes. During the gentle blowing process, the molten steel is agitated and not exposed.

[0050] Step S6: Perform continuous casting to obtain the hot-formed steel PHS product. Control the superheat of the molten steel in the continuous casting ladle at 22 ℃. Use medium-carbon low-alloy steel protective slag, a small-beveled crystallizer, and light reduction (3 mm) at a casting speed of 1.2 m / min. See Table 3 for the inspection results of the hot-formed steel PHS product samples.

[0051] Table 3. Finished Product Composition / wt.%

[0052]

[0053] Example 2

[0054] The smelting method of the 1GPa hot-formed steel PHS for the coated substrate in this embodiment includes the following steps:

[0055] Step S1: The molten iron entering the steel plant has a C content of 4.23 wt.%, and residual elements Cu: 0.062 wt.%, Mo: 0.021 wt.%, Ni: 0.034 wt.%, Sn: 0.020 wt.%, As: 0.0063 wt.%. Using the above molten iron as raw material, the raw material molten iron is subjected to vanadium extraction and desulfurization pretreatment to obtain semi-steel. The semi-steel contains, by weight percentage, 3.48 wt.% C, 0.032 wt.% Mn, 0.073 wt.% P, 0.002 wt.% S, 0.026 wt.% V, and trace amounts of Cr, Si, and Ti. The residual elements Cu: 0.051 wt.%, Mo: 0.023 wt.%, Ni: 0.031 wt.%, Sn: 0.018 wt.%, As: 0.0063 wt.%. wt.%; the balance is iron and unavoidable impurities.

[0056] In step S2, 231.4 tons of the aforementioned semi-steel are added to a 220-ton (nominal capacity) top-and-bottom blown converter. The oxygen blowing and decarburization function of the converter is used to initially refine the semi-steel into molten steel. When the molten steel reaches a C content of 0.06 wt.%, a Mn content of 0.033 wt.%, a P content of 0.0086 wt.%, a S content of 0.0043 wt.%, and a temperature of 1676 ℃, the thick slag is started to be tapped into the ladle. Argon blowing is performed throughout the tapping process. After 2 / 3 of the steel has been tapped, 4 kg / t of active lime is added to the ladle for mixing. Calcium carbide is added for deoxidation during tapping, resulting in an oxygen content of 78 ppm. After tapping, 7 kg / t of calcium-based top slag modifier is added.

[0057] Step S3: The small platform enters the station to feed Al-Mg wire at a speed of 5 m / s, with a target Al content of 0.045 wt.% in the steel. The Al-Mg wire contains 21 wt.% Mg and 79 wt.% Al.

[0058] Step S4 involves sequentially performing the LF and RH processes to fine-tune the alloy and remove inclusions. Specifically,

[0059] Step S41, the chemical composition of the alloy after adjustment in the LF process is shown in Table 4.

[0060] Table 4. Composition of LF alloy after fine-tuning / wt.%

[0061]

[0062] Before leaving the station, the LF molten steel was gently blown out with a small argon flow for 4 minutes. During the gentle blowing process, the molten steel was turned over and not exposed.

[0063] Step S42, RH ≤ 3 mbar, circulation time 13 min. Chemical composition of the RH process is shown in Table 5:

[0064] Table 5 Chemical composition of RH process / wt.%

[0065]

[0066] Step S5: After the alloy fine-tuning treatment is completed, 0.20 kg / t of molten steel is fed into the Ca-Al line. Before the molten steel leaves the station, it is gently blown with a small argon flow rate for 10 minutes. During the gentle blowing process, the molten steel is agitated and not exposed.

[0067] Step S6: Perform continuous casting to obtain the hot-formed steel PHS product. Control the superheat of the molten steel in the continuous casting ladle to 25 ℃. Use medium-carbon low-alloy steel protective slag, a small-beveled crystallizer, and light reduction (4 mm reduction) at a casting speed of 1.1 m / min. See Table 6 for the inspection results of the hot-formed steel PHS product samples.

[0068] Table 6. Finished Product Composition / wt.%

[0069]

[0070] Example 3

[0071] The smelting method of the 1GPa hot-formed steel PHS of the coated substrate in this embodiment includes the following steps: Step S1, the molten iron entering the steel plant has a C content of 4.28 wt.%, and residual elements Cu: 0.055 wt.%, Mo: 0.026 wt.%, Ni: 0.041 wt.%, Sn: 0.026 wt.%, As: 0.0071 wt.%; using the above molten iron as raw material, the raw material molten iron is subjected to vanadium extraction and desulfurization pretreatment to obtain semi-steel, which contains, by weight percentage, 3.56 wt.% C, 0.041 wt.% Mn, 0.062 wt.% P, 0.002 wt.% S, 0.03 wt.% V, and trace amounts of Cr, Si, and Ti, with residual elements Cu: 0.053 wt.%, Mo: 0.024 wt.%, Ni: 0.039 wt.%, Sn: 0.024 wt.%. wt.%, As: 0.0068 wt.%; the balance is iron and unavoidable impurities.

[0072] In step S2, 230.7 tons of the aforementioned semi-steel are added to a 220-ton (nominal capacity) top-and-bottom blown converter. The oxygen blowing and decarburization function of the converter is used to initially refine the semi-steel into molten steel. When the molten steel reaches a C content of 0.075 wt.%, a Mn content of 0.031 wt.%, a P content of 0.0092 wt.%, a S content of 0.0038 wt.%, and a temperature of 1668 ℃, the thick slag is started to be tapped into the ladle. Argon blowing is performed throughout the tapping process. After 2 / 3 of the steel has been tapped, 5 kg / t of active lime is added to the ladle for mixing. Calcium carbide is added for deoxidation during tapping, resulting in an oxygen content of 98 ppm. After tapping, 8 kg / t of calcium-based top slag modifier is added.

[0073] Step S3: The small platform enters the station to feed Al-Mg wire at a speed of 3 m / s, with a target Al content of 0.048 wt.% in the steel. The Al-Mg wire contains 25 wt.% Mg and 75 wt.% Al.

[0074] Step S4 involves sequentially performing the LF and RH processes to fine-tune the alloy and remove inclusions. Specifically,

[0075] Step S41, the chemical composition of the alloy after adjustment in the LF process is shown in Table 7.

[0076] Table 7. Composition of LF alloy after fine-tuning / wt.%

[0077]

[0078] Before leaving the station, the LF molten steel was gently blown with a small argon flow for 4 minutes. During the gentle blowing process, the molten steel was turned over and not exposed.

[0079] Step S42, RH ≤ 3 mbar, circulation time 13 min. Chemical composition of the RH process is shown in Table 8:

[0080] Table 8 Chemical composition of RH process / wt.%

[0081]

[0082] Step S5: After the alloy fine-tuning treatment is completed, 0.25 kg / t of molten steel is fed into the Ca-Al wire. Before leaving the station, the molten steel is gently blown with a small argon flow rate for 10 minutes. During the gentle blowing process, the molten steel is agitated and not exposed.

[0083] Step S6: Perform continuous casting to obtain hot-formed steel PHS finished product. Control the superheat of molten steel in the continuous casting ladle to 28 ℃. Use medium-carbon low-alloy steel protective slag, a small-beveled crystallizer, and light reduction (5 mm reduction) at a casting speed of 1.0 m / min. See Table 9 for the inspection results of the hot-formed steel PHS finished product samples.

[0084] Table 9. Finished Product Composition / wt.%

[0085]

[0086] The above embodiments merely illustrate implementation methods of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A method for smelting 1GPa hot-formed steel PHS with a coated substrate, characterized in that, Includes the following steps: S1, vanadium extraction and desulfurization pretreatment of raw iron are used to obtain semi-steel; S2, the semi-steel is added to a converter for oxygen decarburization treatment, and the semi-steel is initially refined into molten steel with a C content of 0.05~0.08 wt.% before tapping. The tapping process uses calcium carbide for deoxidation, controlling the oxygen activity after deoxidation to 50~100 ppm, wherein the calcium carbide contains ≥95 wt.% calcium carbide. S3, using a platform system to transport a ladle containing molten steel into an argon blowing station, and feeding Al-Mg wire into the molten steel to supplement deoxidation, with a target Al content of 0.040±0.010 wt.% in the molten steel, and the feeding speed controlled at 3~5 m / s, wherein the Al-Mg wire contains 20~25 wt.% Mg and 75~80 wt.% Al; S4, perform the LF process and the RH process in sequence to perform alloy fine-tuning and remove inclusions; S5, enter the argon blowing station and feed Ca-Al wire into the alloy-fine-tuned molten steel; and S6, perform continuous casting process to obtain hot-formed steel PHS product with the following composition: C 0.10~0.13 wt.%, Si 0.15~0.25 wt.%, Mn 1.40~1.60 wt.%, P ≤0.015 wt.%, S ≤0.002 wt.%, Als 0.030~0.050 wt.%, Nb 0.015~0.030 wt.%, Cr 0.25~0.35 wt.%, Ti 0.025~0.035 wt.%, N ≤0.0040 wt.%, B 0.0025~0.0035 wt.%, balance being Fe and unavoidable impurities.

2. The method according to claim 1, characterized in that, In step S1, the C content of the raw material molten iron is ≥4.0 wt.%, and the residual element content satisfies: Cu ≤0.10 wt.%, Mo ≤0.05 wt.%, Ni ≤0.10 wt.%, Sn ≤0.03 wt.%, As ≤0.01 wt.%.

3. The method according to claim 1, characterized in that, In step S1, the composition of the semi-steel satisfies: C 3.4~4.0 wt.%, Mn 0.02~0.05 wt.%, P 0.05~0.08 wt.%, S ≤0.003 wt.%.

4. The method according to claim 3, characterized in that, In step S2, During the converter charging stage, S ≤ 0.001 wt.%; Argon blowing is used for steel tapping in the converter throughout the process. After 2 / 3 of the steel has been tapped, lime is added in a mixture of 3-5 kg ​​per ton of steel. When the steel composition meets the requirements of P≤0.010 wt.%, S≤0.005 wt.%, and temperature≥1665 ℃, thick slag begins to be discharged into the ladle. After tapping, add 6-8 kg / ton of steel top slag modifier to the slag surface.

5. The method according to claim 4, characterized in that, The top slag modifier is a calcium-based top slag modifier with the following composition: CaC2 30~50 wt.%, Al2O3 10~30 wt.%, CaO 20~40 wt.%, CaF2 8~15 wt.%, S≤0.2 wt.%, P≤0.1 wt.%, and the remainder being unavoidable impurities.

6. The method according to claim 1, characterized in that, In step S4, The target chemical composition for the LF process is: C 0.10±0.01 wt.%, Si 0.18±0.05 wt.%, Mn 1.40±0.05 wt.%, P ≤0.015 wt.%, Cr 0.30±0.05 wt.%, Nb 0.022±0.005 wt.%, S ≤0.002 wt.%, Als 0.05±0.01 wt.%, with the balance being Fe and unavoidable impurities; After the LF process, the molten steel is gently blown with a small argon flow rate for 3-5 minutes and then removed from the argon blowing station.

7. The method according to claim 1, characterized in that, In step S4, During the RH process, the RH is controlled to be ≤3 mbar and cyclically processed for 10~15 min. The target chemical composition for the RH process is: C 0.12±0.01 wt.%, Si 0.20±0.05 wt.%, Mn 1.50±0.05 wt.%, P ≤0.015 wt.%, S ≤0.002 wt.%, Als 0.045±0.005 wt.%, N ≤0.0035 wt.%, Cr 0.30±0.05 wt.%, Nb 0.022±0.005 wt.%, B 0.0030±0.0005 wt.%, with the balance being Fe and unavoidable impurities.

8. The method according to claim 1, characterized in that, In step S5, The feed rate of the Ca-Al wire is controlled to be 0.15~0.25 kg / t of molten steel; Control the wire feeding speed to 4~6 m / s; After feeding the wire, gently blow argon gas for 8-12 minutes, then remove it from the argon blowing station.

9. The method according to claim 2, characterized in that, In step S6, The superheat of molten steel in the continuous casting ladle is 20~35℃; Continuous casting uses peritectic steel for protection, a small chamfered crystallizer, and light reduction, with a reduction of 3~5 mm. Target casting speed: 1.0~1.2 m / min, constant speed casting is used in production.

10. A coated substrate 1GPa hot-formed steel PHS, characterized in that, The hot-formed steel PHS is smelted by the method described in any one of claims 1-9.

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