Silicon-killed stainless steel and method of melting to avoid inclusion precipitation of magnesium aluminate spinel

Abstract

The application discloses a silicon deoxidized stainless steel and a smelting method for avoiding crystallization of inclusions magnesium aluminum spinel, and belongs to the technical field of steelmaking, and comprises the following steps: smelting, according to the required component distribution of the steel grade, obtaining the molten steel with S≤0.0035% and pouring into AOD smelting; carrying out decarburization and temperature rising and nitrogen alloying by bottom blowing O2 / N2 mixed gas; after the carbon content reaches the target content, reducing Cr2O3 in the slag and deoxidizing and alloying; after slagging and stirring, tapping, transporting the ladle to LF treatment; adjusting the content of Ni, Mo and B elements in the molten steel, adding silicon carbide to carry out diffusion deoxidization on the slag, and adjusting the basicity of the top slag of the ladle; after feeding the silicon-calcium wire into the molten steel, starting soft blowing, adding a covering agent after the temperature reaches the standard, and then transporting to die casting or continuous casting; die casting or continuous casting, and pouring under the protection of argon gas cover in the whole process. By controlling the low Al and low Mg content in the molten steel in the smelting process of the silicon deoxidized stainless steel, the basicity of the top slag in the LF refining process is reduced, and the crystallization of low-melting-point inclusions magnesium aluminum spinel in the cooling and solidification process of the molten steel is limited.

Description

Technical Field

[0001] This invention belongs to the field of steelmaking technology, specifically relating to a silicon deoxidized stainless steel and a smelting method for avoiding inclusions in magnesium aluminum spinel. Background Technology

[0002] Most stainless steel grades employ silicon deoxidation in their smelting process to avoid the formation of magnesium-aluminum spinel inclusions in the steel caused by Al deoxidation, thus preventing harm to the steel's hot and cold working processes and product performance. Stainless steel deoxidation primarily utilizes a silicon-based inclusion plasticization treatment process. The plastic deformation capacity of oxide inclusions is directly related to their melting temperature, while their breakage capacity is mainly related to their elastic modulus. Historically, inclusion control has primarily focused on lowering the melting point to improve inclusion plasticity. Additionally, some production practices have involved controlling inclusion composition to obtain inclusions with low elastic modulus, enabling better breakage of inclusions in cord steel during steel rolling.

[0003] Oxide inclusions in silicon-deoxidized stainless steel can be divided into two categories: CaO-SiO2-MgO-Al2O3 and MnO-SiO2-Al2O3 systems. CaO-SiO2-MgO-Al2O3 system inclusions are larger and pose a greater threat to the processing and properties of stainless steel. Lowering the melting point is the target for inclusion control in silicon-deoxidized stainless steel. However, during the cooling and solidification of molten steel and subsequent heating processes, high-melting-point magnesium-aluminum spinel phase inclusions often precipitate from within the oxide inclusions in the low-melting-point CaO-SiO2-MgO-Al2O3 system. These precipitated magnesium-aluminum spinels severely detrimental to the hot and cold working of stainless steel and its product properties. While the oxide inclusion composition is usually controlled within the low-melting-point region with good plasticity during steelmaking, large-sized high-melting-point magnesium-aluminum spinels still accumulate within individual inclusions in the solidified ingots or continuously cast billets. Therefore, controlling the crystallization of oxide inclusions in stainless steel has become a bottleneck restricting the plasticization effect of inclusions. Summary of the Invention

[0004] To address the aforementioned technical problems, the present invention aims to provide a silicon-deoxidized stainless steel and a novel, efficient smelting method for preventing the precipitation of magnesium-aluminum spinel from inclusions. By controlling the low Al and low Mg content in the molten steel during the silicon-deoxidized stainless steel smelting process and reducing the basicity of the top slag during LF refining, the precipitation of magnesium-aluminum spinel from low-melting-point inclusions in the molten steel is limited during cooling and solidification.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] According to a first aspect of the present invention, a method for smelting silicon deoxidized stainless steel to avoid inclusions and crystallization of magnesium aluminum spinel is provided, comprising the following steps:

[0007] Step 1: Smelt in an electric arc furnace or medium frequency furnace, and prepare the steel according to the required composition of the steel grade to obtain molten steel with S≤0.0035% and add it to AOD for smelting;

[0008] Step 2: AOD smelting, bottom blowing O2 / N2 mixed gas for decarburization and heating and nitrogen alloying; after the carbon content reaches the target content, Cr2O3 in the low aluminum ferrosilicon alloy reducing slag is used for deoxidation and alloying; after slag making and stirring, the steel is tapped and the ladle is transported to LF processing.

[0009] Step 3: LF refining, adjusting the Ni, Mo and B elements in the molten steel to the target content, adding silicon carbide to diffuse deoxidize the slag, and adjusting the basicity of the ladle top slag; after feeding the molten steel with a silicon-calcium wire, start soft blowing, and after the temperature reaches the target, add a covering agent and then transport it to ingot casting or continuous casting.

[0010] Step 4: Ingot casting or continuous casting. Ingot casting uses the bottom pouring method. Both continuous casting and ingot casting are carried out under argon gas protection throughout the pouring process.

[0011] Furthermore, step 2 specifically includes:

[0012] Bottom-blown O2 / N2 mixed gas is used for decarburization and heating, as well as nitrogen alloying;

[0013] After the carbon content reaches the target content required for stainless steel, Cr2O3 in the low-aluminum ferrosilicon alloy reducing slag is used for deoxidation and alloying to control the low aluminum content in the steel.

[0014] Lime and fluorite are used to form slag, so as to achieve rapid desulfurization.

[0015] After creating new slag, stir with bottom-blown argon gas for 5-10 minutes, tap out the steel, and transport the ladle to LF for processing.

[0016] Furthermore, the Al content in the low-aluminum ferrosilicon alloy is ≤0.004%, and the Al content in the molten steel is ≤0.010%.

[0017] Furthermore, after the AOD reduction period ends and the slag is removed, lime and fluorite are added. This ensures that the AOD slag contains 3-10% CaF2, 4-7% MgO, ≤3% Al2O3, CaO / SiO2 = 1.9-2.8, and a slag volume of 2.3-3.2t.

[0018] Furthermore, the AOD smelting temperature is controlled between 1670℃ and 1750℃.

[0019] Furthermore, step 3 specifically includes:

[0020] By energizing and heating, nickel plates, ferromolybdenum, and ferroboron are added to adjust the Ni, Mo, and B elements in the molten steel to achieve the target content of the steel grade.

[0021] Adding silicon carbide allows for diffusion deoxidation of the slag, and adding quartz sand or silica adjusts the basicity of the ladle top slag.

[0022] After feeding the silicon-calcium wire into the molten steel, soft blowing begins;

[0023] After the molten steel reaches the required temperature, a covering agent is added to the slag surface of the ladle, and then it is transported to the ingot casting or continuous casting process.

[0024] Furthermore, the amount of silicon carbide added is 1.0 to 1.5 kg / t, and the basicity of the ladle top slag (CaO / SiO2 = 1.3 to 1.8) is adjusted by adding quartz sand or silica. The slag content is 4 to 7%, Al2O3 content is ≤3%, FeO+MnO content is <1.0%, and the slag-to-steel ratio ranges from 0.03 to 0.06.

[0025] Furthermore, the graphite electrode in the LF refining process is energized and heated. The temperature of the molten steel in the entire LF refining process is 1520-1610℃. The alloy materials added in the LF refining process are all low-aluminum alloys, and the Al content and Mg content of the molten steel are controlled to be ≤0.010% and ≤0.0007%, respectively.

[0026] Furthermore, before bottom blowing and stirring in LF refining, 0.2-0.4 kg / t of silicon-calcium wire is fed to the molten steel for weak calcium treatment, controlling the calcium content of the molten steel to 0.0004%-0.0012%; the bottom blowing and stirring time in LF refining is 20-30 min, and the bottom blowing flow rate is 30-80 NL / min; before tapping the steel in LF refining, a covering agent is evenly added to the slag surface of the ladle, avoiding the use of magnesium-containing covering agents.

[0027] Furthermore, when using ingot casting, the entire process is protected during pouring, and the pouring temperature is equal to the liquidus temperature of the steel + 50–80°C; when using continuous casting, the superheat of the molten steel is 25–40°C. In both ingot casting and continuous casting, the total oxygen content of the molten steel is ≤35ppm.

[0028] According to a second aspect of the present invention, a silicon-deoxidized stainless steel is provided, wherein the silicon-deoxidized stainless steel is prepared by the smelting method described in any of the preceding aspects.

[0029] The beneficial effects of this invention are:

[0030] (1) The AOD smelting temperature is controlled at 1670℃~1750℃, and the CaF2 content in the slag is controlled at 3~10% to avoid the steel molten temperature being too high and the CaF2 content in the slag being too high, which would cause severe corrosion of the AOD furnace lining refractory material and thus increase the Mg content in the steel molten material. At the same time, it is conducive to rapid slag formation, adjustment of slag basicity and refining effect. In addition, this also greatly shortens the AOD smelting time, which will also reduce the corrosion of the AOD furnace lining refractory material and thus avoid the increase of Mg in the steel molten material.

[0031] (2) The LF refining slag system uses low alkalinity, which can reduce the Al2O3 content in oxide inclusions and reduce the formation area of ​​magnesium aluminum spinel in oxide inclusions. The LF refining process uses weak calcium treatment to increase the proportion of CaO content in oxide inclusions and reduce the proportion of Al2O3 and MgO content in oxide inclusions, which can effectively prevent the precipitation of magnesium aluminum spinel in oxide inclusions.

[0032] (3) In the LF refining process, the refining slag contains 4-7% MgO, which can reduce the corrosion of the ladle refractory materials and prevent the increase of magnesium content in the molten steel. Low-aluminum alloys are used for all alloy materials to prevent the increase of Al content in the molten steel. In summary, controlling the Al content in the molten steel to ≤0.010% and the Mg content to ≤0.0007% can effectively reduce the Al2O3 and MgO content in oxide inclusions, thereby preventing the precipitation of magnesium aluminum spinel from inclusions.

[0033] (4) In the LF refining process, the slag-to-steel ratio is maintained in the range of 0.03 to 0.06. At the same time, nitrogen gas is blown from the bottom at 30 to 80 NL / min for 20 to 30 minutes, which can make the molten slag fully cover the surface of the molten steel and effectively promote the removal of high melting point inclusions such as magnesium aluminum spinel. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0035] Figure 1 A flowchart of a smelting method for silicon deoxidized stainless steel to avoid inclusion precipitation of magnesium aluminum spinel according to the technical solution of the present invention.

[0036] Figure 2 This refers to a typical inclusion in the 304L stainless steel continuous casting billet in Example 1.

[0037] Figure 3 This refers to a typical inclusion in the 304L stainless steel continuous casting billet in Example 2.

[0038] Figure 4 This refers to a typical inclusion in the 304L stainless steel continuous casting billet in Example 3;

[0039] Figure 5 Typical inclusions in the S2205 stainless steel die-cast ingot of Example 4;

[0040] Figure 6 Typical inclusions in the S2205 stainless steel die-cast ingot of Example 5;

[0041] Figure 7 Typical inclusions in the S2205 stainless steel continuous casting billet in Example 6;

[0042] Figure 8 Typical inclusions in the S2205 stainless steel ingot of Comparative Example 1.

[0043] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0044] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this disclosure as detailed in the appended claims.

[0045] The terms "first," "second," etc., used in this disclosure are for distinguishing similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such use of data can be interchanged where appropriate so that the embodiments of this disclosure described herein can be implemented, for example, in orders other than those illustrated or described herein.

[0046] Furthermore, the terms “comprising” and “having”, and any variations thereof, are intended to cover non-exclusive inclusion, such that a process, method, system, product, or apparatus that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or apparatus.

[0047] Multiple, including two or more.

[0048] And / or, it should be understood that, for the purposes of this disclosure, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone.

[0049] This invention provides a method for smelting silicon-deoxidized stainless steel and a novel, efficient method for avoiding inclusion precipitation in magnesium aluminum spinel. Figure 1 As shown, the method includes:

[0050] Steelmaking raw materials are processed sequentially through electric arc furnace / medium frequency furnace, AOD refining, LF refining, and ingot casting / continuous casting processes to obtain ingots or continuous casting billets.

[0051] Here, in the electric arc furnace / medium frequency furnace process, the raw materials are batched according to the required composition of the steel grade to obtain molten steel, which is then refined with AOD.

[0052] Furthermore, the chemical composition of the molten steel produced by the electric arc furnace / medium frequency furnace, by mass percentage, includes: C≤0.10%, Mn≤3.0%, Si≤1.0%, Cr: 16~26%, Ni: 6~12%, Mo: 0~5%, N: 0.005~0.35%, S≤0.005%.

[0053] In the AOD refining process, during the oxidation period, a bottom-blown O2 / N2 mixed gas is used for decarburization and heating, with the molten steel temperature at 1700–1750℃. After the carbon content of the molten steel is reduced to the target level, the reduction period of AOD smelting begins. The bottom-blown gas is converted to argon, and Cr2O3 from the low-alumina ferrosilicon reducing slag is added to deoxidize the molten steel. After the AOD reduction period, the slag is skimmed off, and lime and fluorite are added to create new slag. The new slag has an Al2O3 content of ≤3% and a slag volume of 2.5–3.2 tons. The AOD smelting temperature is controlled at 1670℃–1750℃. The chemical composition of the AOD-produced molten steel, by mass percentage, includes: C ≤ 0.08%, Mn ≤ 3.0%, Si ≤ 1.0%, Cr: 16–26%, Ni: 6–12%, Mo: 0–5%, N: 0.005–0.35%, S ≤ 0.005%.

[0054] Furthermore, the low-aluminum ferrosilicon during the AOD reduction period comprises the following components by mass percentage: Si: 70%–80%, Al ≤ 0.004%, with the balance being iron and unavoidable impurities. The amount of low-aluminum ferrosilicon added is 25 ± 2 kg / t. While ensuring sufficient deoxidation of the molten steel, the low Al content in the molten steel is controlled to avoid an increase in the Al2O3 content in oxide inclusions.

[0055] Furthermore, the new slag produced after AOD slag removal contains 3-10% CaF2 and 4-7% MgO. The presence of a certain amount of CaF2 in the slag can lower its melting temperature and reduce erosion of the refractory materials. Similarly, the presence of a certain amount of MgO in the slag also reduces erosion of the refractory materials, preventing an increase in the Mg content in the molten steel due to refractory material erosion, which in turn increases the MgO content in inclusions.

[0056] Furthermore, after AOD slag removal, slag is re-formed, with a binary basicity of CaO / SiO2 = 1.9–2.8. If the slag basicity is too high, it will increase the activity of Mg and Al in the molten steel, leading to an increase in the MgO and Al2O3 content in inclusions. If the slag basicity is too high, the formation range of magnesium-aluminum spinel inclusions will also increase significantly. Therefore, it is necessary to maintain a low slag basicity to prevent excessively high MgO and Al2O3 content in inclusions.

[0057] In the LF refining process, after the ladle is in place, slag is removed, the temperature is increased by electricity, and nickel plates, ferromolybdenum, and ferroboron are added to adjust the Ni, Mo, and B elements in the molten steel to achieve the target steel grade content. Silicon carbide is added to the slag for diffusion deoxidation, and nitrogen is first blown at a high flow rate of 160-180 NL / min from the bottom. Quartz sand or silica is added to adjust the top slag of the ladle. After refining for 30-40 minutes, a silicon-calcium wire is fed into the molten steel for weak calcium treatment, controlling the calcium content of the molten steel to 0.0004%-0.0012%. After the weak calcium treatment, soft blowing is performed, with a low flow rate of nitrogen blown from the bottom. The temperature of the molten steel throughout the LF refining process is 1520-1610℃. Before LF refining, carbonized rice husk covering agent is evenly added to the slag surface of the ladle, avoiding the use of magnesium-containing covering agent. The Al content of the molten steel is controlled to be ≤0.010%, preferably 0.0018-0.0065%, more preferably 0.0018-0.0035%, and even more preferably 0.0018%; the Mg content is controlled to be ≤0.0007%, preferably 0.0002%-0.0006%, more preferably 0.0002%-0.0004%, and even more preferably 0.0002%.

[0058] It has been verified that the contents of the two are mutually restrictive. Specifically, when the Al content is higher than 0.010% and the Mg content is lower than 0.0007%, or when the Al content is lower than 0.010% and the Mg content is higher than 0.0007%, or when the Al content is higher than 0.010% and the Mg content is higher than 0.0007%, a large amount of magnesium aluminum spinel will precipitate inside the oxide inclusions.

[0059] Furthermore, in actual stainless steel smelting production, achieving an Al content below 0.0018% and a Mg content below 0.0002% in the steel is virtually impossible. Firstly, the alloying materials added during the stainless steel smelting process contain trace amounts of Al and Mg. Secondly, both AOD (Al₂O₃) and ladle refractory materials are sources of Mg in the steel. Controlling the Al content to below 0.0018% and the Mg content to below 0.0002% in the steel would be extremely difficult and costly.

[0060] After LF refining, the ladle is transported to continuous casting or ingot casting. The chemical composition of the molten steel from LF, by mass percentage, includes: C≤0.08%, Mn≤3.0%, Si≤1.0%, Cr: 16~26%, Ni: 6~12%, Mo: 0~5%, N: 0.005~0.35%, S≤0.005%, O≤0.005%.

[0061] Furthermore, the ferromolybdenum and ferroboron added in the LF refining process are low-aluminum ferromolybdenum alloys and low-aluminum ferroboron alloys, in order to control the Al content of the molten steel to ≤0.010% and the Mg content to ≤0.0007%, and to prevent the Al2O3 and MgO content in the oxide inclusions from being too high, thus preventing the precipitation of magnesium aluminum spinel.

[0062] Furthermore, the amount of silicon carbide added during the LF refining process is 1.0–1.5 kg / t;

[0063] The feed rate of the calcium silicon wire is 0.2–0.4 kg / t. Weak calcium treatment increases the CaO content in oxide inclusions and reduces the proportion of Al2O3 and MgO, effectively preventing the precipitation of magnesium aluminum spinel within the inclusions. If the feed rate is below 0.2 kg / t, the CaO content in the oxide inclusions is too low. On one hand, the inclusions have high melting points and are difficult to deform; on the other hand, the high proportion of Al2O3 and MgO in the inclusions leads to the precipitation of magnesium aluminum spinel within them. If the feed rate is above 0.4 kg / t, the CaO content in the oxide inclusions is too high, resulting in very high melting points and preventing deformation, thus harming the steel's processing and performance.

[0064] Furthermore, in LF refining, quartz sand or silica is added to adjust the binary basicity of the slag (CaO / SiO2 = 1.3–1.8), with MgO content of 4–7%, Al2O3 content ≤3%, FeO+MnO content <1.0%, and a slag-to-steel ratio ranging from 0.03 to 0.06. Low slag basicity reduces the content of MgO and Al2O3 in oxide inclusions and decreases the formation area of ​​Mg-aluminum spinel inclusions. A certain amount of MgO in the slag can mitigate the erosion of the ladle refractory material and effectively prevent Mg enrichment in the molten steel. Maintaining the slag-to-steel ratio within the range of 0.03–0.06 and the molten steel temperature within 1520–1610℃ ensures that the slag completely covers the surface of the molten steel, promoting the flotation and removal of locally enriched MgO·Al2O3 spinel inclusions in the molten steel.

[0065] Furthermore, in the LF refining soft blowing process, a small flow rate of nitrogen is used for bottom blowing, ideally to control slight fluctuations on the slag surface, with a flow rate of 30–80 NL / min and a soft blowing time of 20–30 min. A reasonable bottom blowing regime is beneficial for the flotation and removal of large-sized, high-melting-point oxide inclusions. In addition, a reasonable bottom blowing regime will promote the reactivity of slag and steel, and further facilitate the control of inclusion composition.

[0066] During the continuous casting or ingot casting process, the entire pouring process is protected to prevent secondary oxidation of the molten steel, and the total oxygen content of the molten steel is controlled to be ≤35ppm. The chemical composition of the ingot, by mass percentage, includes: C≤0.08%, Mn≤3.0%, Si≤1.0%, Cr: 16~26%, Ni: 6~12%, Mo: 0~5%, N: 0.005~0.35%, S≤0.005%, O≤0.005%.

[0067] Furthermore, if the ingot casting process is adopted, protective pouring is used throughout the process, and the pouring temperature is the liquidus temperature of the steel +50 to 80°C.

[0068] If continuous casting is used, the molten steel is superheated to 25–40°C, and argon gas is used for protection throughout the casting process. To avoid contamination of the molten steel by refractory materials during casting, the refractory materials in the ladle, tundish, long nozzle, stopper rod, and submerged entry nozzle—parts that come into direct contact with the molten steel—are all non-aluminized, meaning Al₂O₃ + Al ≤ 2.5%. Otherwise, the Al content in the molten steel will increase, exceeding the upper limit of Al content given in the claims, leading to the precipitation of magnesium aluminum spinel within the oxide inclusions. Furthermore, steady-state casting is maintained throughout the process to avoid excessive casting speed causing slag entanglement on the molten steel surface.

[0069] In fact, by combining AOD smelting temperature, CaF2 content in AOD slag, LF refining slag composition, LF refining weak calcium treatment, slag-to-steel ratio, low Al content in alloy materials, LF soft blowing system, and refining temperature control, the goal of achieving MgO content ≤12% and Al2O3 content ≤25% in CaO-SiO2-MgO-Al2O3 inclusions in molten steel after LF refining can be achieved, ultimately avoiding the precipitation of magnesium aluminum spinel in inclusions.

[0070] Example 1:

[0071] This embodiment describes the operational steps of a method to avoid the precipitation of magnesium aluminum spinel in silicon-deoxidized stainless steel inclusions. The first embodiment specifically uses 304L stainless steel.

[0072] Electric arc furnace and medium frequency furnace processes: Electric arc furnaces and medium frequency furnaces smelt stainless steel mother liquor, using recycled steel, high-nickel pig iron, scrap steel, and alloy materials as raw materials. The medium frequency furnace is used to melt the alloy materials. The electric arc furnace smelting process employs a sliding plate slag-blocking and steel-retaining operation for tapping, with a tapping temperature of 1660℃. No slag-forming materials are added during the tapping process. After tapping, carbonized rice husks are evenly spread on the surface of the molten steel.

[0073] AOD process: The mother liquor from electric arc furnace and medium frequency furnace smelting is poured into the AOD furnace. In the AOD smelting process, chromium oxide from the low-alumina ferrosilicon reducing slag and molten steel are used for deoxidation. The Al content in the low-alumina ferrosilicon is ≤0.004%, and the Al content in the molten steel is 0.0025%. After the slag is skimmed off at the end of the AOD reduction period, 500 kg of lime and 300 kg of fluorite are added. The AOD slag has a CaF2 content of 7.8%, an MgO content of 5.8%, an Al2O3 content of 2.5%, a binary basicity of CaO / SiO2 = 1.9, and a slag volume of 2.3 t. The AOD smelting temperature is controlled between 1670℃ and 1750℃.

[0074] LF process: Upon arrival at the ladle, 1.0 kg / t of silicon carbide is added for diffusion deoxidation. Quartz sand is added to adjust the basicity of the ladle top slag (CaO / SiO2 = 1.5). The slag content is 5.2% MgO, 2.2% Al2O3, 7.2% CaF2, and <1.0% FeO+MnO, with a slag-to-steel ratio of 0.03. The graphite electrodes in the LF refining process are energized to raise the temperature, with the molten steel temperature ranging from 1520 to 1610℃ throughout the refining process. The alloying materials added in the LF refining process are all low-aluminum alloys, with an Al content of 0.0018% and a Mg content of 0.0002% in the molten steel. After the molten steel composition and temperature are suitable, carbonized rice husks are added to the ladle slag surface for insulation. The bottom-blowing argon flow rate is adjusted to 35–80 NL / min to control slight fluctuations on the slag surface, and soft blowing and stirring are performed for 30 minutes. Before the soft blowing and stirring in the LF refining process, 0.2 kg / t of silicon-calcium wire is fed to the molten steel for weak calcium treatment. The tapping temperature is 1540℃.

[0075] Continuous casting process: continuous casting with full protective pouring, total oxygen content of molten steel in the tundish is 30ppm, superheat of molten steel is 30℃, and casting speed is 1.1m / min.

[0076] See appendix Figure 2 It can be seen that the oxide inclusions are uniformly composed of CaO-SiO2-MgO-Al2O3, and no magnesium aluminum spinel is precipitated at any position in the inclusions. Furthermore, the melting point of the CaO-SiO2-MgO-Al2O3 inclusions is 1300℃.

[0077] Example 2:

[0078] This embodiment describes the operational steps of a method to avoid the precipitation of magnesium aluminum spinel in silicon-deoxidized stainless steel inclusions. The second embodiment specifically uses 304L stainless steel.

[0079] Electric arc furnace and medium frequency furnace processes: Electric arc furnaces and medium frequency furnaces smelt stainless steel mother liquor, using recycled steel, high-nickel pig iron, scrap steel, and alloy materials as raw materials. The medium frequency furnace is used to melt the alloy materials. The electric arc furnace smelting process employs a sliding plate slag-blocking and steel-retaining operation for tapping, with a tapping temperature of 1670℃. No slag-forming materials are added during the tapping process. After tapping, carbonized rice husks are evenly spread on the surface of the molten steel.

[0080] AOD process: The mother liquor from electric arc furnace and medium frequency furnace smelting is poured into the AOD furnace. In the AOD smelting process, chromium oxide from the low-alumina ferrosilicon reducing slag and molten steel are used for deoxidation. The Al content in the low-alumina ferrosilicon is ≤0.004%, and the Al content in the molten steel is 0.0082%. After the slag is removed at the end of the AOD reduction period, 660 kg of lime and 280 kg of fluorite are added. The AOD slag contains 8.2% CaF2, 7% MgO, and 2.3% Al2O3. The binary basicity of the slag is CaO / SiO2 = 2.8, and the slag volume is 3.2 t.

[0081] LF process: Upon arrival at the ladle, 1.5 kg / t of silicon carbide is added for diffusion deoxidation. Quartz sand is added to adjust the basicity of the ladle top slag (CaO / SiO2 = 1.8). The slag content is 6.7% MgO, 2.0% Al2O3, 7.3% CaF2, and <1.0% FeO+MnO, with a slag-to-steel ratio of 0.06. The graphite electrodes in the LF refining process are energized to raise the temperature, with the molten steel temperature ranging from 1520 to 1610℃ throughout the refining process. The alloying materials added in the LF refining process are all low-aluminum alloys, with an Al content of 0.0077% and a Mg content of 0.0007% in the molten steel. After the molten steel composition and temperature are suitable, carbonized rice husks are added to the surface of the ladle slag for insulation. The bottom-blowing argon flow rate is adjusted to 35–80 NL / min to control slight fluctuations on the slag surface, and soft blowing and stirring are performed for 26 minutes. Before the soft blowing and stirring in the LF refining process, 0.4 kg / t of silicon-calcium wire is fed to the molten steel for weak calcium treatment. The tapping temperature is 1580℃.

[0082] Continuous casting process: continuous casting with full protection during pouring, total oxygen content of molten steel in the tundish is 28ppm, superheat of molten steel is 40℃, and casting speed is 1.2m / min.

[0083] See appendix Figure 3 It can be seen that the oxide inclusions are uniformly composed of CaO-SiO2-MgO-Al2O3, and no magnesium aluminum spinel is precipitated at any position in the inclusions. Furthermore, the melting point of the CaO-SiO2-MgO-Al2O3 inclusions is 1430℃.

[0084] Example 3:

[0085] This embodiment describes the operational steps of a method to avoid the precipitation of magnesium aluminum spinel in silicon-deoxidized stainless steel inclusions. The third embodiment specifically uses 304L stainless steel.

[0086] Electric arc furnace and medium frequency furnace processes: Electric arc furnaces and medium frequency furnaces smelt stainless steel mother liquor, using recycled steel, high-nickel pig iron, scrap steel, and alloy materials as raw materials. The medium frequency furnace is used to melt the alloy materials. The electric arc furnace smelting process employs a sliding plate slag-blocking and steel-retaining operation for tapping, with a tapping temperature of 1665℃. No slag-forming materials are added during the tapping process. After tapping, carbonized rice husks are added and evenly spread on the surface of the molten steel.

[0087] AOD process: The mother liquor from electric arc furnace and medium frequency furnace smelting is poured into the AOD furnace. In the AOD smelting process, chromium oxide from the low-alumina ferrosilicon reducing slag and molten steel are used for deoxidation. The Al content in the low-alumina ferrosilicon is ≤0.004%, and the Al content in the molten steel is 0.0055%. After the slag is removed at the end of the AOD reduction period, 550 kg of lime and 350 kg of fluorite are added. The AOD slag has a CaF2 content of 5.8%, an MgO content of 6.2%, an Al2O3 content of 2.2%, a binary basicity of slag CaO / SiO2 = 2.5, and a slag volume of 2.7 t.

[0088] LF process: Upon arrival at the ladle, 1.3 kg / t of silicon carbide is added for diffusion deoxidation. Quartz sand is added to adjust the basicity of the ladle top slag (CaO / SiO2 = 1.5). The slag content is 5.8% MgO, 2.0% Al2O3, 5.2% CaF2, and <1.0% FeO+MnO, with a slag-to-steel ratio of 0.045. The graphite electrodes in the LF refining process are energized to raise the temperature, with the molten steel temperature ranging from 1520 to 1610℃ throughout the refining process. The alloying materials added in the LF refining process are all low-aluminum alloys, with an Al content of 0.0050% and a Mg content of 0.0005% in the molten steel. After the molten steel composition and temperature are suitable, carbonized rice husks are added to the surface of the ladle slag for insulation. The bottom-blowing argon flow rate is adjusted to 35–80 NL / min to control slight fluctuations on the slag surface, and soft blowing and stirring are performed for 20 minutes. Before the soft blowing and stirring in the LF refining process, 0.3 kg / t of silicon-calcium wire is fed to the molten steel for weak calcium treatment. The tapping temperature is 1555℃.

[0089] Continuous casting process: continuous casting with full protective pouring, total oxygen content of molten steel in the tundish is 32ppm, superheat of molten steel is 32℃, and casting speed is 1.1m / min.

[0090] See appendix Figure 4 It can be seen that the oxide inclusions are uniformly composed of CaO-SiO2-MgO-Al2O3, and no magnesium aluminum spinel is precipitated at any position in the inclusions. Furthermore, the melting point of the CaO-SiO2-MgO-Al2O3 inclusions is 1375℃.

[0091] Example 4:

[0092] This embodiment describes the operational steps of a method to avoid the precipitation of magnesium aluminum spinel inclusions in silicon deoxidized stainless steel. Embodiment four specifically uses S2205 stainless steel.

[0093] Medium frequency furnace process: The medium frequency furnace smelts stainless steel mother liquor. The raw materials are recycled steel, high-nickel pig iron, scrap steel and alloy materials. The tapping temperature is 1702℃.

[0094] AOD process: Two 30t batches of molten steel are smelted in an intermediate frequency furnace and then added to the AOD furnace. In the AOD smelting process, chromium oxide from the low-alumina ferrosilicon reducing slag is used to deoxidize the molten steel. The Al content in the low-alumina ferrosilicon is ≤0.004%, and the Al content in the molten steel is 0.0032%. After the slag is skimmed off at the end of the AOD reduction period, 510kg of lime and 330kg of fluorite are added. The AOD slag contains 3.3% CaF2, 4.6% MgO, and 2.2% Al2O3. The binary basicity of the slag, CaO / SiO2 = 1.9, and the slag quantity is 2.3t.

[0095] LF process: Upon arrival at the ladle, 1.0 kg / t of silicon carbide is added for diffusion deoxidation. Silica is added to adjust the basicity of the ladle top slag (CaO / SiO2 = 1.3). The slag content is 4.4% MgO, 1.9% Al2O3, 2.9% CaF2, and <1.0% FeO+MnO, with a slag-to-steel ratio of 0.03. The graphite electrode in the LF refining process is energized to raise the temperature, with the molten steel temperature ranging from 1520 to 1610℃ throughout the refining process. The alloying materials added in the LF refining process are all low-aluminum alloys, with an Al content of 0.0024% and a Mg content of 0.0003% in the molten steel. After the molten steel composition and temperature are suitable, carbonized rice husks are added to the ladle slag surface for insulation. The bottom-blowing argon flow rate is adjusted to 35–80 NL / min to control slight fluctuations on the slag surface, and soft blowing and stirring are performed for 30 minutes. Before the soft blowing and stirring in the LF refining process, 0.2 kg / t of silicon-calcium wire is fed to the molten steel for weak calcium treatment. The tapping temperature is 1558℃.

[0096] Ingot casting process: The entire ingot casting process adopts the pouring method and protective pouring. The total oxygen content of the molten steel in the ladle is 35ppm, and the pouring temperature of the molten steel is 1548℃.

[0097] See appendix Figure 5 It can be seen that the oxide inclusions are uniformly composed of CaO-SiO2-MgO-Al2O3, and no magnesium aluminum spinel is precipitated at any position in the inclusions. Furthermore, the melting point of the CaO-SiO2-MgO-Al2O3 inclusions is 1310℃.

[0098] Example 5:

[0099] This embodiment describes the operational steps of a method to avoid the precipitation of magnesium aluminum spinel inclusions in silicon-deoxidized stainless steel. Embodiment 5 specifically uses S2205 stainless steel.

[0100] Medium frequency furnace process: The medium frequency furnace smelts stainless steel mother liquor. The raw materials are recycled steel, high-nickel pig iron, scrap steel and alloy materials. The tapping temperature is 1680℃.

[0101] AOD process: Two 30t furnaces of molten steel are smelted sequentially in an intermediate frequency furnace and then added to the AOD furnace. In the AOD smelting process, chromium oxide from the low-alumina ferrosilicon reducing slag is used to deoxidize the molten steel. The Al content in the low-alumina ferrosilicon is ≤0.004%, and the Al content in the molten steel is 0.0093%. After skimming off the slag at the end of the AOD reduction period, 715kg of lime and 536kg of fluorite are added. The AOD slag contains 9.3% CaF2, 7% MgO, and 2.8% Al2O3, with a binary basicity of CaO / SiO2 = 2.8, and a slag volume of 3.2t.

[0102] LF process: Upon arrival at the ladle, 1.5 kg / t of silicon carbide is added for diffusion deoxidation. Silica is added to adjust the basicity of the ladle top slag (CaO / SiO2 = 1.8). The slag content is 6.5% MgO, 2.1% Al2O3, 8.7% CaF2, and <1.0% FeO+MnO, with a slag-to-steel ratio of 0.06. The graphite electrodes in the LF refining process are energized to raise the temperature, with the molten steel temperature ranging from 1520 to 1610℃ throughout the refining process. The alloying materials added in the LF refining process are all low-aluminum alloys, with an Al content of 0.0072% and a Mg content of 0.0007% in the molten steel. After the molten steel composition and temperature are suitable, carbonized rice husks are added to the ladle slag surface for insulation. The bottom-blowing argon flow rate is adjusted to 35–80 NL / min to control slight fluctuations on the slag surface, and soft blowing and stirring are performed for 25 minutes. Before the soft blowing and stirring in the LF refining process, 0.4 kg / t of silicon-calcium wire is fed to the molten steel for weak calcium treatment. The tapping temperature is 1588℃.

[0103] Ingot casting process: The entire ingot casting process adopts the pouring method and protective pouring. The total oxygen content of the molten steel in the ladle is 29ppm, and the pouring temperature of the molten steel is 1578℃.

[0104] See appendix Figure 6 It can be seen that the oxide inclusions are uniformly composed of CaO-SiO2-MgO-Al2O3, and no magnesium aluminum spinel is precipitated at any position in the inclusions. Furthermore, the melting point of the CaO-SiO2-MgO-Al2O3 inclusions is 1450℃.

[0105] Example 6:

[0106] This embodiment describes the operational steps of a method to avoid the precipitation of magnesium aluminum spinel in inclusions in silicon-deoxidized stainless steel. Embodiment six specifically uses S2205 stainless steel.

[0107] Medium frequency furnace process: The medium frequency furnace smelts stainless steel mother liquor. The raw materials are recycled steel, high-nickel pig iron, scrap steel and alloy materials. The tapping temperature is 1690℃.

[0108] AOD process: Two 30t furnaces of molten steel are smelted sequentially in an intermediate frequency furnace and then added to the AOD furnace. In the AOD smelting process, chromium oxide from the low-alumina ferrosilicon reducing slag is used to deoxidize the molten steel. The Al content in the low-alumina ferrosilicon is ≤0.004%, and the Al content in the molten steel is 0.0057%. After skimming off the slag at the end of the AOD reduction period, 632kg of lime and 477kg of fluorite are added. The AOD slag contains 6.4% CaF2, 6% MgO, and 2.4% Al2O3, with a binary basicity of CaO / SiO2 = 2.4, and a slag volume of 2.8t.

[0109] LF process: Upon arrival at the ladle, 1.2 kg / t of silicon carbide is added for diffusion deoxidation. Quartz sand is added to adjust the basicity of the ladle top slag (CaO / SiO2 = 1.6). The slag content is 5.6% MgO, 2.1% Al2O3, 5.9% CaF2, and <1.0% FeO+MnO, with a slag-to-steel ratio of 0.048. The graphite electrodes in the LF refining process are energized to raise the temperature, with the molten steel temperature ranging from 1520 to 1610℃ throughout the refining process. The alloying materials added in the LF refining process are all low-aluminum alloys, with an Al content of 0.0044% and a Mg content of 0.0005% in the molten steel. After the molten steel composition and temperature are suitable, carbonized rice husks are added to the ladle slag surface for insulation. The bottom-blowing argon flow rate is adjusted to 35–80 NL / min to control slight fluctuations on the slag surface, and soft blowing and stirring are performed for 23 minutes. Before the soft blowing and stirring in the LF refining process, 0.32 kg / t of silicon-calcium wire is fed to the molten steel for weak calcium treatment. The tapping temperature was 1564℃.

[0110] Continuous casting process: continuous casting with full protective pouring, total oxygen content of molten steel in the tundish is 32ppm, superheat of molten steel is 32℃, and casting speed is 1.1m / min.

[0111] See appendix Figure 7 It can be seen that the oxide inclusions are uniformly composed of CaO-SiO2-MgO-Al2O3, with no magnesium aluminum spinel precipitated at any location within the inclusions, and the melting point of the CaO-SiO2-MgO-Al2O3 inclusions is 1390℃. Comparative Example 1:

[0112] In the original process for producing 2205 stainless steel, two 30-ton furnaces of molten steel were produced using an intermediate frequency furnace. The raw materials were recycled steel, high-nickel pig iron, scrap steel, and alloy materials, which were then mixed with Al₂O₃ (AOD) for smelting. During the AOD smelting process, chromium oxide from the low-alumina ferrosilicon reducing slag was used to deoxidize the molten steel. The Al content in the low-alumina ferrosilicon was ≤0.004%, and the Al content in the molten steel was 0.016%. After the AOD reduction period, lime and fluorite were added to rebuild the slag. The binary basicity of the AOD slag, CaO / SiO₂, was 3.0, and the slag volume was 3.3 tons. The molten steel from the AOD smelting process was poured into a ladle and transported to the LF station for refining. The inclusion type in the AOD ladle was CaO-SiO₂-MgO-Al₂O₃. After the LF ladle arrives at the station, silicon carbide diffusion deoxidation is added, and quartz sand is added to adjust the basicity of the ladle top slag (CaO / SiO2 = 2.5). The slag contains 8.5% MgO and 3.1% Al2O3, with a slag-to-steel ratio of 0.048. The LF refining graphite electrode is energized to raise the temperature, and the temperature range of the molten steel throughout the refining process is 1520–1610℃. The alloying materials added in the LF refining process are all low-aluminum alloys, with an Al content of 0.012% and a Mg content of 0.0011% in the molten steel. After the molten steel composition and temperature are suitable, carbonized rice husks are added to the surface of the ladle slag for insulation. The bottom-blowing argon flow rate is adjusted to 35–80 NL / min to control slight fluctuations on the slag surface, and soft blowing and stirring are performed for 30 minutes. Before the soft blowing and stirring in the LF refining process, 0.6 kg / t of silicon-calcium wire is fed to the molten steel for weak calcium treatment. The tapping temperature is 1564℃. The inclusions in the ladle are of the CaO-SiO2-MgO-Al2O3 type.

[0113] Ingot casting process: The entire ingot casting process adopts the pouring method and protective pouring. The total oxygen content of the molten steel in the ladle is 35ppm, and the pouring temperature of the molten steel is 1552℃.

[0114] See appendix Figure 8 It can be seen that a large number of large-sized magnesium aluminum spinel crystals precipitated inside the CaO-SiO2-MgO-Al2O3 inclusions in the die-cast ingot.

[0115] Comparative Example 2:

[0116] This comparative example describes the operational steps of a method to avoid the precipitation of magnesium aluminum spinel inclusions in silicon-deoxidized stainless steel. The comparative example is 304L stainless steel.

[0117] Electric arc furnace and medium frequency furnace processes: Electric arc furnaces and medium frequency furnaces smelt stainless steel mother liquor, using recycled steel, high-nickel pig iron, scrap steel, and alloy materials as raw materials. The medium frequency furnace is used to melt the alloy materials. The electric arc furnace smelting process employs a sliding plate slag-blocking and steel-retaining operation for tapping, with a tapping temperature of 1675℃. No slag-forming materials are added during the tapping process. After tapping, carbonized rice husks are evenly spread on the surface of the molten steel.

[0118] AOD process: The mother liquor from electric arc furnace and medium frequency furnace smelting is poured into the AOD furnace. In the AOD smelting process, chromium oxide from the low-alumina ferrosilicon reducing slag and molten steel are used for deoxidation. The Al content in the low-alumina ferrosilicon is ≤0.004%, and the Al content in the molten steel is 0.015%. After the slag is removed at the end of the AOD reduction period, 600 kg of lime and 270 kg of fluorite are added. The AOD slag has a CaF2 content of 8.5%, an MgO content of 6.5%, an Al2O3 content of 2.1%, a binary basicity of slag CaO / SiO2 = 2.2, and a slag volume of 2.9 t.

[0119] LF process: Upon arrival at the ladle, 1.4 kg / t of silicon carbide is added for diffusion deoxidation. Quartz sand is added to adjust the basicity of the ladle top slag (CaO / SiO2 = 1.6). The slag content is 5.7% MgO, 2.0% Al2O3, 7.6% CaF2, and <1.0% FeO+MnO, with a slag-to-steel ratio of 0.04. The graphite electrodes in the LF refining process are energized to raise the temperature, with the molten steel temperature ranging from 1530 to 1610℃ throughout the refining process. The alloying materials added in the LF refining process are all low-aluminum alloys, with an Al content of 0.0138% and a Mg content of 0.0006% in the molten steel. After the molten steel composition and temperature are suitable, carbonized rice husks are added to the ladle slag surface for insulation. The bottom-blowing argon flow rate is adjusted to 35–80 NL / min to control slight fluctuations on the slag surface, and soft blowing and stirring are performed for 28 minutes. Before the soft blowing and stirring in the LF refining process, 0.4 kg / t of silicon-calcium wire is fed to the molten steel for weak calcium treatment. The tapping temperature is 1560℃.

[0120] Continuous casting process: continuous casting with full protection during pouring, total oxygen content of molten steel in the tundish is 26ppm, superheat of molten steel is 33℃, and casting speed is 1.2m / min.

[0121] A large number of large-sized magnesium aluminum spinel rich in Al2O3 precipitated inside the oxide inclusions in the continuously cast billet.

[0122] Comparative Example 3:

[0123] This comparative example describes the operational steps of a method to avoid the precipitation of magnesium aluminum spinel inclusions in silicon-deoxidized stainless steel. The comparative example is S2205 stainless steel.

[0124] Electric arc furnace and medium frequency furnace process: The electric arc furnace and medium frequency furnace smelt stainless steel mother liquor. The raw materials are recycled steel, high-nickel pig iron, scrap steel and alloy materials. The tapping temperature is 1685℃.

[0125] AOD process: The mother liquor from the electric arc furnace and medium-frequency furnace for smelting stainless steel is added to the AOD furnace. In the AOD smelting process, chromium oxide from the low-alumina ferrosilicon reducing slag is used to deoxidize the molten steel. The Al content in the low-alumina ferrosilicon is ≤0.004%, and the Al content in the molten steel is 0.0055%. After the slag is skimmed off at the end of the AOD reduction period, 620 kg of lime and 400 kg of fluorite are added. The AOD slag has a CaF2 content of 6.8%, an MgO content of 6.9%, an Al2O3 content of 2.2%, a binary basicity of CaO / SiO2 = 2.5, and a slag volume of 2.7 t.

[0126] LF process: Upon arrival at the ladle, 1.2 kg / t of silicon carbide is added for diffusion deoxidation. Quartz sand is added to adjust the basicity of the ladle top slag (CaO / SiO2 = 1.8). The slag content is 5.9% MgO, 2.0% Al2O3, 6.3% CaF2, and <1.0% FeO+MnO, with a slag-to-steel ratio of 0.04. The graphite electrodes in the LF refining process are energized to raise the temperature, with the molten steel temperature ranging from 1520 to 1600℃ throughout the refining process. The alloying materials added in the LF refining process are all low-aluminum alloys, with an Al content of 0.0048% and a Mg content of 0.0010% in the molten steel. After the molten steel composition and temperature are suitable, carbonized rice husks are added to the ladle slag surface for insulation. The bottom-blowing argon flow rate is adjusted to 35–80 NL / min to control slight fluctuations on the slag surface, and soft blowing and stirring are performed for 28 minutes. Before the soft blowing and stirring in the LF refining process, 0.32 kg / t of silicon-calcium wire is fed to the molten steel for weak calcium treatment. The tapping temperature is 1550℃.

[0127] Continuous casting process: continuous casting with full protective pouring, total oxygen content of molten steel in the tundish is 30ppm, superheat of molten steel is 30℃, and casting speed is 1.1m / min.

[0128] A large number of large-sized magnesium aluminum spinel rich in Al2O3 precipitated inside the oxide inclusions in the continuously cast billet.

[0129] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for smelting silicon-deoxidized stainless steel to avoid the precipitation of magnesium aluminum spinel inclusions, characterized in that, Includes the following steps: Step 1: Smelt in an electric arc furnace or medium frequency furnace, and prepare the steel according to the required composition of the steel grade to obtain molten steel with S≤0.0035% and add it to AOD for smelting; Step 2: AOD smelting, bottom blowing O2 / N2 mixed gas for decarburization and heating and nitrogen alloying; after the carbon content reaches the target content, Cr2O3 in the low aluminum ferrosilicon alloy reducing slag is used for deoxidation and alloying; after slag making and stirring, the steel is tapped and the ladle is transported to LF processing. Step 3: LF refining, adjusting the Ni, Mo and B elements in the molten steel to the target content, adding silicon carbide to diffuse deoxidize the slag, and adjusting the basicity of the ladle top slag; after feeding the molten steel with a silicon-calcium wire, start soft blowing, and after the temperature reaches the target, add a covering agent and then transport it to ingot casting or continuous casting. Step 4: Ingot casting or continuous casting, with argon gas protection throughout the pouring process; In the LF refining process, the graphite electrode is energized and heated. The temperature of the molten steel in the entire LF refining process is 1520~1610℃. The alloy materials added in the LF refining process are all low-aluminum alloys, and the Al content and Mg content of the molten steel are controlled to be ≤0.010% and ≤0.0007%.

2. The method according to claim 1, characterized in that, Step 2 specifically includes: Bottom-blown O2 / N2 mixed gas is used for decarburization and heating, as well as nitrogen alloying; After the carbon content reaches the target content required for stainless steel, Cr2O3 in the low-aluminum ferrosilicon alloy reducing slag is used for deoxidation and alloying to control the low aluminum content in the steel. Lime and fluorite are used to form slag, so as to achieve rapid desulfurization. After creating new slag, stir with bottom-blown argon gas for 5-10 minutes, tap out the steel, and transport the ladle to LF for processing.

3. The method according to claim 1, characterized in that, The low-aluminum ferrosilicon alloy contains ≤0.004% Al, and the molten steel contains ≤0.010% Al.

4. The method according to claim 1, characterized in that, After the AOD reduction period ends and the slag is removed, lime and fluorite are added; the AOD smelting temperature is controlled at 1670℃~1750℃.

5. The method according to claim 1, characterized in that, Step 3 specifically includes: By energizing and heating, nickel plates, ferromolybdenum, and ferroboron are added to adjust the Ni, Mo, and B elements in the molten steel to achieve the target content of the steel grade. Adding silicon carbide allows for diffusion deoxidation of the slag, and adding quartz sand or silica adjusts the basicity of the ladle top slag. After feeding the silicon-calcium wire into the molten steel, soft blowing begins; After the molten steel reaches the required temperature, a covering agent is added to the slag surface of the ladle, and then it is transported to the die casting or continuous casting process.

6. The method according to claim 1, characterized in that, The amount of silicon carbide added is 1.0~1.5 kg / t. Quartz sand or silica is added to adjust the basicity of the ladle top slag CaO / SiO2=1.3~1.

8. The MgO content in the slag is 4~7%, the Al2O3 content is ≤3%, the FeO+MnO content is <1.0%, and the slag-to-steel ratio is in the range of 0.03~0.

06.

7. The method according to claim 1, characterized in that, Before bottom blowing and stirring in LF refining, feed 0.2~0.4kg / t silicon-calcium wire to perform weak calcium treatment on the molten steel, controlling the calcium content of the molten steel to 0.0004%~0.0012%; the bottom blowing and stirring time in LF refining is 20~30min, and the bottom blowing flow rate is 30~80NL / min; before tapping the steel in LF refining, add a covering agent evenly to the slag surface of the ladle, avoiding the use of magnesium-containing covering agents.

8. The method according to claim 1, characterized in that, When using the die casting process, die casting employs full-process protective pouring, and the pouring temperature = liquidus temperature of the steel + (50~80)℃; when using the continuous casting process, the superheat of the molten steel is 25~40℃; in die casting / continuous casting employs full-process protective pouring, and the total oxygen content of the molten steel is ≤35ppm.

9. A silicon-deoxidized stainless steel, characterized in that, The silicon-deoxidized stainless steel is prepared by the smelting method according to any one of claims 1 to 8.

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