Low silicon and low sulfur steel grade control silicon return LF smelting method

Abstract

The application relates to a low-silicon low-sulfur steel LF smelting method for controlling silicon return, and belongs to the technical field of steel preparation; the method comprises the following steps: pre-argon blowing is conducted on converter molten steel; first top slag modification is conducted on the converter molten steel after the pre-argon blowing; slagging and temperature rising treatment is conducted on the converter molten steel after the top slag modification, and the bottom blowing flow of the slagging and temperature rising treatment process is 300-800 NL / min; strong stirring desulfurization is conducted on the converter molten steel after the slagging and temperature rising treatment; calcium treatment is conducted on the converter molten steel after the strong stirring desulfurization, then soft blowing is conducted, and LF smelting is completed; the bottom blowing flow is controlled in the slagging and temperature rising treatment process, so that columnar through flow of the converter molten steel is prevented, and the silicon return problem in the LF furnace refining process is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of steel production, and in particular to a LF smelting method for controlling back-silicon of low-silicon and low-sulfur steel. BACKGROUND

[0002] High-strength alloy structural aluminum killed steel requires a low mass fraction of silicon and sulfur. In terms of steelmaking, the LF furnace refining process is used to produce low-silicon (Si≤0.04%) and low-sulfur (S≤0.005%) aluminum killed steel. While deoxidizing and desulfurizing, the problem of "back-silicon" is brought about, which makes it difficult to control the content of silicon and greatly increases the smelting difficulty of refining. Sometimes, the silicon content is out of range, or due to improper operation method in balancing the relationship between preventing silicon increase and desulfurization, poor deoxidization and low desulfurization rate occur, and eyelet accidents occur during casting. SUMMARY

[0003] The present application provides a LF smelting method for controlling back-silicon of low-silicon and low-sulfur steel to improve the problem of back-silicon in the LF furnace refining process.

[0004] The inventors found in the process of invention that if columnar through flow occurs in the converter molten steel during slagging and temperature rising treatment, the final molten steel will have a more obvious back-silicon phenomenon.

[0005] The present application provides a LF smelting method for controlling back-silicon of low-silicon and low-sulfur steel, which comprises:

[0006] Pre-blowing argon to the converter molten steel;

[0007] First top slag modification to the converter molten steel after the pre-blowing argon;

[0008] Slagging and temperature rising treatment to the converter molten steel after the top slag modification, and the bottom blowing flow of the slagging and temperature rising treatment process is 300-800 NL / min;

[0009] Strong stirring desulfurization to the converter molten steel after the slagging and temperature rising treatment;

[0010] Calcium treatment to the converter molten steel after the strong stirring desulfurization, and then soft blowing to complete the LF smelting.

[0011] As an optional implementation, the slagging agent of the slagging and temperature rising treatment comprises self-produced synthetic slag;

[0012] Optionally, the components of the self-produced synthetic slag comprise, by mass fraction, CaO: 62%-68%, MgO: 5%-8%, Al2O3: 6%-10%, SiO2: 3%-5%, and CaF2: 8%-15%.

[0013] As an optional implementation, the slagging and temperature-raising treatment on the converter liquid steel after the top slag modification includes:

[0014] a first slagging and temperature-raising treatment on the converter liquid steel after the top slag modification;

[0015] a second slagging and temperature-raising treatment on the converter liquid steel after the first slagging and temperature-raising treatment;

[0016] wherein, the adding amount of slagging agent in the first slagging and temperature-raising treatment is 800-1200 kg, the temperature-raising time of the first slagging and temperature-raising treatment is 3-5 min, and the adding amount of slagging agent in the second slagging and temperature-raising treatment is 300-600 kg.

[0017] As an optional implementation, the feeding speed of calcium treatment is 2.0-3.0 m / s, and the bottom blowing flow of calcium treatment process is 80-120 NL / min.

[0018] As an optional implementation, the flow of pre-argon blowing is 1000-1200 NL / min, and the time of pre-argon blowing is 2-4 min.

[0019] As an optional implementation, the modifying agent of the first top slag modification includes first aluminum particles, and the adding amount of the first aluminum particles is 80-150 kg; and the bottom blowing flow of the first top slag modification process is 80-120 NL / min.

[0020] As an optional implementation, in the strong stirring desulfurization process, the temperature of the converter liquid steel is >1580℃; and / or

[0021] the bottom blowing flow of the strong stirring desulfurization is 1100-1300 NL / min, and the time of the strong stirring desulfurization is 3-5 min.

[0022] As an optional implementation, before the strong stirring desulfurization, the method further includes:

[0023] color judgment on the slag produced by the slagging and temperature-raising treatment;

[0024] if the color of the slag is light gray or light green, the strong stirring desulfurization is performed;

[0025] if the color of the slag is black, a second top slag modification is performed, and then color judgment on the slag is performed again, wherein the modifying agent of the second top slag modification includes second aluminum particles, and the adding amount of the second aluminum particles is 50-80 kg; or

[0026] before the strong stirring desulfurization, the method further includes:

[0027] judging the composition of the slag sub-product generated in the slagging and temperature rising process;

[0028] if the sum of the mass content of FeO and MnO in the slag sub-product is ≤1.0%, the strong stirring desulfurization is performed;

[0029] if the sum of the mass content of FeO and MnO in the slag sub-product is >1.0%, the second top slag modification is performed, and then the composition of the slag sub-product is judged again, wherein the modifier of the second top slag modification comprises second aluminum particles, and the addition amount of the second aluminum particles is 50-80 kg.

[0030] As an optional implementation, after the strong stirring desulfurization, the method further comprises sampling and sample temperature rising, the bottom blowing flow rate of the sampling process is 80-120 NL / min, and the bottom blowing flow rate of the sample temperature rising process is 300-800 NL / min.

[0031] As an optional implementation, the flow rate of the soft blowing is 50-100 NL / min, and the time of the soft blowing is 8-10 min.

[0032] The above technical solution provided by the embodiments of the present application has the following advantages compared with the prior art:

[0033] The method provided by the embodiments of the present application controls the bottom blowing flow rate in the slagging and temperature rising process to prevent the formation of columnar through flow of the converter molten steel, thereby improving the silicon back problem in the LF refining process. BRIEF DESCRIPTION OF DRAWINGS

[0034] The accompanying drawings, which are incorporated into and form part of the specification, illustrate embodiments consistent with the present application and, together with the specification, serve to explain the principles of the application.

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, those skilled in the art can obtain other drawings according to these drawings without any creative effort.

[0036] Figure 1 The flow chart of the method provided by the embodiments of the present application. DETAILED DESCRIPTION

[0037] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0038] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0039] like Figure 1 As shown in the embodiment of this application, a method for controlled silicon reversion in the LF smelting of low-silicon, low-sulfur steel grades is provided, the method comprising:

[0040] S1. Pre-blowing argon into the molten steel in the converter;

[0041] In some embodiments, the flow rate of the pre-blown argon is 1000-1200 NL / min, and the pre-blown argon time is 2-4 min.

[0042] Specifically, in this embodiment, after the molten steel from the converter arrives at the station, it is pre-blown with argon for 3 minutes at an argon flow rate of 1000-1200 NL / min to confirm the uniformity of composition and the slag-forming and bottom-blowing effects.

[0043] S2. Perform the first top slag modification on the converter molten steel after the pre-blowing of argon;

[0044] In some embodiments, the modifier for the first top slag modification includes first aluminum particles, the amount of which is 80-150 kg; and the bottom blowing flow rate of the first top slag modification process is 80-120 NL / min.

[0045] Specifically, in this embodiment, after bottom blowing argon is completed, the converter molten steel is temperature measured, sampled, and slag-coated. According to the color of the top slag, 80-150 kg of aluminum particles are added to deoxidize and modify the slag. The argon flow rate for modification is 100 NL / min.

[0046] S3. The converter steel after the top slag modification is subjected to slag-forming and heating treatment, wherein the bottom blowing flow rate of the slag-forming and heating treatment process is 300-800 NL / min;

[0047] In some embodiments, the slag-forming agent for the slag-forming heating treatment includes self-produced synthetic slag; optionally, the composition of the self-produced synthetic slag, by mass fraction, includes: CaO: 62%-68%, MgO: 5%-8%, Al2O3: 6%-10%, SiO2: 3%-5%, and CaF2: 8%-15%.

[0048] In some embodiments, the slagging and temperature-raising treatment on the converter liquid steel after the top slag modification is completed comprises:

[0049] S3.1. performing a first slagging and temperature-raising treatment on the converter liquid steel after the top slag modification is completed, wherein the first slagging and temperature-raising treatment is performed by adding 800-1200 kg of slagging agent, and the first slagging and temperature-raising treatment is performed for 3-5 min.

[0050] S3.2. performing a second slagging and temperature-raising treatment on the converter liquid steel after the first slagging and temperature-raising treatment is completed, wherein the second slagging and temperature-raising treatment is performed by adding 300-600 kg of slagging agent.

[0051] Specifically, in this embodiment, after the top slag modification is completed, 800-1200 kg of the first batch of self-produced synthetic slag is added to the converter liquid steel, the electrode is started to arc, the slag is melted, and the temperature is raised for 3-5 min to quickly form a high-alkalinity slag, and then the second batch of self-produced synthetic slag is added again, and the argon flow rate is controlled to be 300-800 NL / min during the slagging and temperature-raising to avoid the formation of columnar through flow due to excessive argon blowing intensity and serious silicon return.

[0052] In some embodiments, before the strong stirring desulfurization, the method further comprises: judging the color of the slag produced by the slagging and temperature-raising treatment; if the color of the slag is light gray or light green, the strong stirring desulfurization is performed; if the color of the slag is black, the second top slag modification is performed again, and then the color of the slag is judged again, wherein the modification agent of the second top slag modification comprises second aluminum particles, and the addition amount of the second aluminum particles is 50-80 kg, or, before the strong stirring desulfurization, the method further comprises: judging the composition of the slag produced by the slagging and temperature-raising treatment; if the sum of the mass contents of FeO and MnO in the slag is ≤1.0%, the strong stirring desulfurization is performed; if the sum of the mass contents of FeO and MnO in the slag is >1.0%, the second top slag modification is performed, and then the composition of the slag is judged again, wherein the modification agent of the second top slag modification comprises second aluminum particles, and the addition amount of the second aluminum particles is 50-80 kg.

[0053] Specifically, in this embodiment, the color of the slag before the strong stirring desulfurization is required to be light gray or light green, and the FeO+MnO in the slag is controlled to be ≤1.0% for the best, and if the color of the top slag is black, 50-80 kg of aluminum particles are added to the slag surface to perform the second slag modification to make the top slag in weak reducing property.

[0054] S4. performing strong stirring desulfurization on the converter liquid steel after the slagging and temperature-raising treatment is completed;

[0055] In some embodiments, the temperature of the converter liquid steel is >1580℃ during the strong stirring desulfurization; in other words, the temperature is controlled to be >1580℃ before the strong stirring desulfurization to ensure slag solubility; the bottom blowing flow rate of the strong stirring desulfurization is 1100-1300 NL / min, and the time of the strong stirring desulfurization is 3-5 min.

[0056] Specifically, in the present embodiment, the liquid steel is stirred by argon for 3-5 min according to the sulfur content at the inlet station before the slag becomes light gray or light green, the argon flow rate of the strong stirring desulfurization is 1200 NL / min, and the desulfurization rate is ensured to be 50%-70%.

[0057] In some embodiments, after the strong stirring desulfurization, the method further comprises sampling and sample temperature rising, the bottom blowing flow rate of the sampling process is 80-120 NL / min, and the bottom blowing flow rate of the sample temperature rising process is 300-800 NL / min.

[0058] Specifically, in the present embodiment, the argon flow rate is reduced to 100 NL / min after the strong stirring desulfurization, temperature measurement and sampling are performed, the electrode is continued to be heated during the sample temperature rising process, and the argon flow rate is restored to 300-800 NL / min.

[0059] S5. The converter liquid steel after the strong stirring desulfurization is subjected to calcium treatment, and then soft blowing is performed to complete the LF smelting.

[0060] In some embodiments, the wire feeding speed of the calcium treatment is 2.0-3.0 m / s, the bottom blowing flow rate of the calcium treatment process is 80-120 NL / min, the flow rate of the soft blowing is 50-100 NL / min, and the time of the soft blowing is 8-10 min.

[0061] Specifically, in the present embodiment, after the composition is adjusted according to the process sample, calcium treatment is performed, silicon is increased to prevent splashing of the steel slag caused by the calcium treatment, the wire feeding speed is controlled to be 2.5 m / s, and the bottom blowing flow rate is 100 NL / min; after the wire feeding is completed, soft blowing is performed, the soft blowing is performed for 8-10 min, and the soft blowing is completed, and the soft blowing flow rate is controlled to be 50-100 NL / min.

[0062] By using the method, the LF desulfurization rate is 50-70%, the sulfur content at the end is lower than 0.005%, the phenomenon of silicon return of the liquid steel can be obviously controlled, the average amount of silicon return is reduced from 0.030% to 0.020%, thereby the composition qualification rate of the low-silicon and low-sulfur steel grade is effectively improved, and quality accidents caused by composition exceeding the standard are avoided.

[0063] The application will be further described in conjunction with specific examples. It should be understood that these examples are only used to illustrate the application and not used to limit the scope of the application. The experimental methods in the following examples, if no specific conditions are noted, are generally determined according to national standards. If there is no corresponding national standard, the general international standards, conventional conditions, or the conditions suggested by the manufacturer are used.

[0064] Example 1

[0065] Taking the production of low-silicon and low-sulfur steel AA412031 with a capacity of 300 tons as an example, the following is the specific process:

[0066] After the molten steel arrives at the station, pre-blowing argon is performed for 3 minutes, the argon flow rate is 1000 NL / min, and the Al content after viewing the furnace is 0.036%,

[0067] The temperature at the station is 1558℃, the sample at the station and the sample with slag are taken, the color is dark black, 100 kg of aluminum particles are added for slag modification and deoxidation in the slag, and the argon flow rate during modification is 100 NL / min;

[0068] After the top slag is modified, the first batch of 1000 kg of self-produced synthetic slag is added, the electrode is started, the slag is melted, and the temperature is raised for 3 minutes, then the second batch of 800 kg of self-produced synthetic slag is added again, the argon flow rate during slagging and temperature rising is 400 NL / min; the heating and temperature rising time is 11 minutes, the sample at the station reports that the S content is 0.0066% and the Si content is 0.012% during heating, the temperature is 1585℃ after heating, the color of the sample with slag is light green, the slag sample is sent, and the strong stirring desulfurization is started, the argon flow rate is 1200 NL / min;

[0069] After 3 minutes of strong stirring, the argon flow rate is reduced to 100 NL / min, the temperature is 1575℃, the process sample is taken and sent, the electrode continues to rise for 4 minutes during the process of taking the sample, the argon flow rate is 400 NL / min, the process sample reports that the S content is 0.0018% and the Si content is 0.027%, and the top slag FeO+MnO=0.07%.

[0070] After the composition is adjusted according to the process sample, calcium treatment is performed, the wire feeding speed is controlled at 2.5 m / s, the wire feeding length is 260 m, and the bottom blowing flow rate during wire feeding is 100 NL / min.

[0071] After the wire feeding is completed, soft blowing is started, the soft blowing flow rate is 50 NL / min, the end sample is taken after 4 minutes of soft blowing, the end sample reports that the S content is 0.0014% and the Si content is 0.030%, which meets the requirements of the steel grade that S≤0.0050% and Si≤0.04%.

[0072] Using this method, the desulfurization rate can be 50-70%, the phenomenon of molten steel returning silicon is significantly controlled, and the average amount of returned silicon is reduced from 0.030% to 0.020%.

[0073] Various embodiments of the application can take the form of a range; it should be understood that the description in the form of a range is merely for the sake of convenience and brevity, and should not be construed as a rigid limitation of the scope of the application; therefore, it should be considered that the range described has specifically disclosed all possible sub-ranges and single values within the range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single values within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fraction or integer) within the indicated range.

[0074] In the present application, the orientation words such as "upper" and "lower" are specifically the directions of the drawing surface in the drawings, unless otherwise stated. In addition, in the description of the specification of the present application, the terms "include", "contain" and the like mean "include but are not limited to".

[0075] In the present application, the relationship terms such as "first" and "second" are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between the entities or operations. In the present application, "and / or" describes the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B can represent the cases of A alone, A and B together, and B alone. Wherein A, B can be singular or plural. In the present application, "at least one" means one or more, and "multiple" means two or more. "At least one", "at least one of the following" or the like means any combination of the items, including single item or any combination of multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can represent a, b, c, a-b (i.e. a and b), a-c, b-c, or a-b-c, wherein a, b, and c can be single or multiple.

[0076] The above description is merely a specific implementation of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for controlling silicon reversion in the LF melting of a low-silicon, low-sulfur steel grade, characterized in that, The method comprises: carrying out pre-argon blowing on the converter liquid steel; carrying out first top slag modification on the converter liquid steel after the pre-argon blowing is completed; carrying out slagging and temperature-raising treatment on the converter liquid steel after the first top slag modification is completed, the bottom blowing flow rate of the slagging and temperature-raising treatment process being 300-800 NL / min to prevent the converter liquid steel from forming columnar through flow and control silicon return; carrying out strong stirring desulfurization on the converter liquid steel after the slagging and temperature-raising treatment is completed; carrying out calcium treatment on the converter liquid steel after the strong stirring desulfurization is completed, and then carrying out soft blowing to complete LF smelting; the slagging agent of the slagging and temperature-raising treatment comprises self-produced synthetic slag; the components of the self-produced synthetic slag comprise, in terms of mass fraction, CaO: 62%-68%, MgO: 5%-8%, Al2O3: 6%-10%, SiO2: 3%-5% and CaF2: 8%-15%; the slagging and temperature-raising treatment on the converter liquid steel after the first top slag modification is completed comprises: carrying out first slagging and temperature-raising treatment on the converter liquid steel after the first top slag modification is completed; carrying out second slagging and temperature-raising treatment on the converter liquid steel after the first slagging and temperature-raising treatment is completed; wherein the addition amount of the slagging agent of the first slagging and temperature-raising treatment is 800-1200 kg, the temperature-raising time of the first slagging and temperature-raising treatment is 3-5 min, and the addition amount of the slagging agent of the second slagging and temperature-raising treatment is 300-600 kg.

2. The low silicon and low sulfur steel grade control silicon return LF melting method according to claim 1, characterized by, the wire feeding speed of the calcium treatment is 2.0-3.0 m / s, and the bottom blowing flow rate of the calcium treatment process is 80-120 NL / min.

3. The low silicon and low sulfur steel grade control silicon reversion LF melting method according to claim 1, characterized by, the flow rate of the pre-argon blowing is 1000-1200 NL / min, and the time of the pre-argon blowing is 2-4 min.

4. The low silicon and low sulfur steel grade control silicon reversion LF melting method according to claim 1, characterized by, the modification agent of the first top slag modification comprises first aluminum particles, and the addition amount of the first aluminum particles is 80-150 kg; the bottom blowing flow rate of the first top slag modification process is 80-120 NL / min.

5. The low silicon and low sulfur steel grade control silicon reversion LF melting method according to claim 1, characterized by, in the strong stirring desulfurization process, the temperature of the converter liquid steel is >1580℃; and / or the bottom blowing flow rate of the strong stirring desulfurization is 1100-1300 NL / min, and the time of the strong stirring desulfurization is 3-5 min.

6. The low silicon and low sulfur steel grade control silicon reversion LF melting method according to claim 1, characterized by, before the strong stirring desulfurization, the method further comprises: carrying out color judgment on the slag produced by the slagging and temperature-raising treatment; if the color of the slag is light gray or light green, the strong stirring desulfurization is carried out; if the color of the slag is black, second top slag modification is carried out, and then color judgment on the slag is carried out again, wherein the modification agent of the second top slag modification comprises second aluminum particles, and the addition amount of the second aluminum particles is 50-80 kg; or before the strong stirring desulfurization, the method further comprises: carrying out component judgment on the slag produced by the slagging and temperature-raising treatment; if the sum of the mass contents of FeO and MnO in the slag is ≤1.0%, the strong stirring desulfurization is carried out; if the sum of the mass contents of FeO and MnO in the slag is >1.0%, second top slag modification is carried out, and then component judgment on the slag is carried out again, wherein the modification agent of the second top slag modification comprises second aluminum particles, and the addition amount of the second aluminum particles is 50-80 kg.

7. The low silicon and low sulfur steel grade control silicon reversion LF melting method according to claim 1, characterized by, After the strong stirring desulfurization, the method further comprises sampling and sample temperature rising, the bottom blowing flow rate of the sampling process is 80-120 NL / min; the bottom blowing flow rate of the sample temperature rising process is 300-800 NL / min.

8. The low silicon and low sulfur steel grade control silicon reversion LF melting method according to claim 1, characterized by, The flow rate of the soft blowing is 50-100 NL / min, and the time of the soft blowing is 8-10 min.

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