Slag making method for silicon-free semi-steel steelmaking and silicon-free semi-steel steelmaking method

Abstract

The invention provides a slagging method for silicon-free semi-steel steelmaking, which comprises the following steps of: in the silicon-free semi-steel steelmaking process, manufacturing a CaO-FeO binary slag system in a non-deslagging furnace, or manufacturing a binary slag system taking CaO-FeO as a main component in the non-deslagging furnace. The invention further relates to a silicon-free semi-steel steelmaking method. In the converter steelmaking process, the CaO-FeO binary slag system or the binary slag system with CaO-FeO as the main component is manufactured for steelmaking, rapid dephosphorization and less-slag smelting in the earlier stage of smelting can be achieved, the steel grade with P smaller than or equal to 0.006% can be stably produced, and the rephosphorization mass content after tapping is smaller than or equal to 0.003%.

Description

Technical Field

[0001] The invention belongs to the technical field of semi-steel steelmaking after vanadium extraction in a converter, and specifically relates to a slag making method for silicon-free semi-steel steelmaking. The invention also relates to a method for silicon-free semi-steel steelmaking. Background Art

[0002] The molten steel obtained after vanadium extraction from vanadium-containing molten iron in a converter is called semi-steel. During the process of vanadium extraction from vanadium-containing molten iron in a converter, the silicon in the molten iron is completely oxidized and enters the vanadium slag. Therefore, the process of vanadium extraction from vanadium in a converter has the effect of vanadium extraction and desiliconization. The semi-steel does not contain silicon after vanadium extraction.

[0003] When using semi-steel as the main raw material for converter steelmaking, a large amount of silicon-containing materials need to be added to the slag-making material to produce converter slag with good fluidity and dephosphorization ability. The slag composition is mainly composed of CaO, SiO2, and FeO, so it is called CaO-SiO2-FeO ternary slag system. By controlling the reasonable basicity and FeO content, this ternary slag system has good dephosphorization ability and good metallurgical properties. Therefore, the existing converter steelmaking technology at home and abroad uses the CaO-SiO2-FeO ternary slag system for steelmaking.

[0004] However, the above-mentioned CaO-SiO2-FeO ternary slag system has the following technical problems: the main component SiO2 of the ternary slag system is an acidic substance, while the refractory materials of the converter lining are all alkaline refractory materials. The slag containing the SiO2 component corrodes the lining seriously, resulting in a short service life of the converter; the phosphorus volume ratio of the ternary slag system is low, and the amount of converter steelmaking slag is large; the dephosphorization effect of the converter is poor. When the mass content of the converter endpoint C is controlled to be 0.08% to 0.20%, the endpoint P>0.006%, and the control of the endpoint P≤0.006% is not achieved. level, and the mass content of phosphorus return after steel tapping is >0.003%; the CaO-SiO2-FeO ternary slag system has weak dephosphorization ability in the early stage of converter blowing; a large amount of high-melting-point substances calcium orthosilicate and calcium metasilicate are produced in the middle stage of converter blowing, causing "drying back" and gun sticking, and the converter steelmaking process is difficult to control; phosphorus return is serious in the late stage of converter blowing, and the mass content of phosphorus return after steel tapping is >0.003%. It is difficult to achieve the control level of the mass content of phosphorus return after steel tapping ≤0.003% using the most advanced slide plate slag blocking steel tapping technology; the amount of slag discharged during the converter tapping process is large. In addition, since additional slag-making materials containing silicon elements need to be added to make slag, the slag-making cost is high and the heat loss is large.

[0005] Therefore, there is still much room for improvement in the slag making method for silicon-free semi-steel steelmaking and the method for silicon-free semi-steel steelmaking. Summary of the invention

[0006] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a new slag making method for silicon-free semi-steel steelmaking. According to the advantage of silicon-free semi-steel in the converter blowing process that no silicon element is oxidized to generate SiO2, the method no longer uses the CaO-SiO2-FeO ternary slag system for smelting, but adopts a production mode of 5-7 furnaces as a cycle, and produces 5-7 furnaces of slag pouring once. In each cycle, the CaO-FeO binary slag system is directly manufactured in the non-slag pouring furnaces of the first 4-6 furnaces, or the binary slag system with CaO-FeO as the main component is manufactured in the non-slag pouring furnaces of the first 4-6 furnaces for smelting, and the slag pouring operation is performed in the last furnace of each cycle. The method has a better P removal ability while greatly reducing the slag amount. The advantage of greatly reducing the converter slag amount is that the slag pouring operation only needs to be performed once after continuous smelting of 5-7 furnaces, which has higher production efficiency and low cost than the prior art that slag pouring is required once per steelmaking furnace.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions: The invention provides a slag making method for silicon-free semi-steel steelmaking, which comprises manufacturing a CaO-FeO binary slag system in a non-slag dumping furnace during the silicon-free semi-steel steelmaking process, or manufacturing a binary slag system with CaO-FeO as main components in a non-slag dumping furnace.

[0008] In one embodiment, the production of a CaO-FeO binary slag system in a non-slag dumping furnace comprises the following steps: S1, blowing and desiliconizing the blast furnace molten iron to obtain silicon-free semi-steel; S2, adding silicon-free semi-steel into the converter; S3, blowing oxygen into the converter to produce a large amount of FeO; S4. Active lime is added into the converter to provide CaO, thereby forming a CaO-FeO binary slag system. In one embodiment, the process of producing a binary slag system with CaO-FeO as the main component in a non-slag dumping furnace comprises the following steps: S10, blowing and desiliconizing the blast furnace molten iron to obtain silicon-free semi-steel; S20, adding silicon-free semi-steel into the converter, and adding scrap steel into the converter at the same time, wherein the mass ratio of scrap steel to silicon-free semi-steel is ≤15%, so as to control the mass content of SiO2 in the converter slag to be ≤1.5%; S30, blowing oxygen into the converter to produce a large amount of FeO; S40, adding active lime into the converter to provide CaO, thereby forming a binary slag system with CaO-FeO as main components.

[0009] In one embodiment, in step S1 or step S10, the blast furnace molten iron includes the following components by mass content: C 3.6%-4.5%, Si 0.10%-0.95%, Mn 0.05%-0.50%, P 0.030%-0.150%; the silicon-free semi-steel includes the following components by mass content: C 2.5%-4.0%, Si 0%, Mn 0.01%-0.05%, P 0.028%-0.150%.

[0010] In one embodiment, at the end point of converter blowing, the composition of the final molten steel includes the following components by mass: C 0.08% to 0.20%, P≤0.006%, and the mass content of phosphorus regeneration after steel tapping is ≤0.003%.

[0011] In one embodiment, in step S3 or step S30, the oxygen flow rate of the converter blowing is 22000 Nm 3 / h~38000Nm 3 / h, the oxygen lance position is controlled at 1.3m~1.5m; In step S4 or step S40, 1 t to 2 t / furnace of active lime is added within 1 to 2 minutes after the start of converter blowing.

[0012] In one embodiment, in the early stage of converter blowing, the mass content of FeO is ≥45%; when the mass content of FeO drops to 30%-40% in the middle stage of converter blowing, the oxygen flow rate is increased to 40000 Nm 3 / h~50000Nm 3 / h, raise the oxygen lance position to 1.8m ~ 3.0m.

[0013] In one embodiment, 5-7 furnaces are used as a production cycle, and a slag dumping operation is performed after 5-7 furnaces are produced. The first 4-6 furnaces in each production cycle are smelted by leaving slag in the whole furnace, and the slag dumping operation is performed after the last furnace is smelted, wherein the 4-6 furnaces that leave slag in the whole furnace are all smelted by CaO-FeO binary slag system or binary slag system with CaO-FeO as the main component; In the slag pouring furnace, the CaO-SiO2-FeO ternary slag system is used for smelting, wherein 500 kg to 1000 kg / furnace of slag-making agent containing SiO2 is added in the middle and late stages of converter blowing; or, In the slag pouring furnace, the flux fluorite or high-alumina slag adjusting agent is added in the later stage of converter blowing, and the total amount of flux added is 300 kg ~ 500 kg / furnace.

[0014] In one embodiment, in step S3 or step S30, FeO-rich cold pressed blocks may be added into the converter to adjust the FeO content in the binary slag system CaO-FeO.

[0015] The present invention also provides a method for silicon-free semi-steel steelmaking, which comprises adopting the slag-making method for semi-steel steelmaking described above to manufacture a CaO-FeO binary slag system in a non-slag-dumping furnace, or manufacturing a binary slag system with CaO-FeO as the main component in a non-slag-dumping furnace.

[0016] Compared with the prior art, the beneficial technical effects of the present invention are: (1) The converter uses silicon-free slag system for steelmaking, making full use of the fact that the main raw material for converter steelmaking, semi-steel, is silicon-free. Since no silicon-containing slag-making agent is added in the non-slag pouring furnace, there is no silicon element participating in the reaction of the converter to produce acidic substance SiO2, thereby producing a CaO-FeO binary slag system. This CaO-FeO binary slag system has a strong dephosphorization ability, and the alkaline slag also protects the furnace lining to the maximum extent.

[0017] (2) When adding silicon-free semi-steel into the converter, scrap steel is added into the converter, and while utilizing the heat source of scrap steel, a binary slag system with CaO-FeO as the main component is produced. Since the mass content of SiO2 in the slag is ≤1.5% by controlling the mass ratio of scrap steel to silicon-free semi-steel, and the trace content of SiO2 can be ignored, the binary slag system with CaO-FeO as the main component also has a strong dephosphorization ability, and the alkaline slag also protects the furnace lining to the maximum extent.

[0018] (3) The method of the present invention has a stronger P removal ability than the existing converter slag making technology. When smelting high-quality steel with P≤0.006%, the mass content of the converter end carbon can be controlled within the range of ≤0.20%, which has a wider end carbon control range than the technology of deep dephosphorization with the mass content of the end carbon controlled within the range of ≤0.05% in the prior art. By using the method of the present invention to carry out converter steelmaking, the P removal ability of the slag is greatly improved compared with the steelmaking method of the prior art, and rapid dephosphorization in the early stage of smelting and less slag smelting can be achieved. High-strength high-quality steel with P≤0.006% can be stably produced. The composition of the end molten steel can be accurately controlled within the following mass content composition range according to the composition requirements of the specific steel grade: C 0.08%~0.20%, P≤0.006%, especially when the mass content of the end carbon is increased to the control upper limit of 0.20%, the end P can still be stably controlled at a level of ≤0.006%, and the mass content of phosphorus recovery after steel tapping can be controlled at ≤0.003%. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0020] Figure 1 A schematic flow chart of a slag making method for silicon-free semi-steel steelmaking according to the present invention; Figure 2 Another schematic flow chart of the slag making method for silicon-free semi-steel steelmaking of the present invention; Figure 3 Another schematic flow chart of the slag making method for silicon-free semi-steel steelmaking according to the present invention. DETAILED DESCRIPTION

[0021] The following is a further detailed description of the embodiments of the present disclosure in conjunction with the accompanying drawings and examples. The detailed description of the following embodiments and the accompanying drawings are used to exemplarily illustrate the principles of the present disclosure, but cannot be used to limit the scope of the present disclosure. The present disclosure can be implemented in many different forms and is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

[0022] The present disclosure provides these embodiments to make the present disclosure thorough and complete, and to fully express the scope of the present disclosure to those skilled in the art. It should be noted that unless otherwise specifically stated, the relative arrangement of the parts and steps, the composition of the materials, the numerical expressions and the numerical values ​​set forth in these embodiments should be interpreted as being merely exemplary, and not as limiting.

[0023] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0024] The terms "including" and "having" and any variations thereof in the specification and claims of the present invention and the above-mentioned drawings are intended to cover non-exclusive inclusions; the terms "first", "second", etc. in the specification and claims of the present disclosure or the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order. "Multiple" means two or more, unless otherwise clearly and specifically limited.

[0025] The present invention provides a slag making method for silicon-free semi-steel steelmaking, such as Figure 1As shown, the method includes manufacturing a CaO-FeO binary slag system in a non-slag dumping furnace during silicon-free semi-steelmaking, or manufacturing a binary slag system with CaO-FeO as the main component in a non-slag dumping furnace.

[0026] In a preferred embodiment, if Figure 2 As shown, the process of manufacturing a CaO-FeO binary slag system in a non-slag dumping furnace includes the following steps: S1, carrying out converter blowing and desiliconization on blast furnace molten iron to obtain silicon-free semi-steel; S2, adding silicon-free semi-steel into the converter; S3, blowing oxygen into the converter to produce a large amount of FeO; S4. Active lime is added into the converter to provide CaO, thereby forming a CaO-FeO binary slag system. In a preferred embodiment, in step S1, the blast furnace molten iron includes the following mass contents: C 3.6%-4.5%, Si 0.10%-0.95%, Mn 0.05%-0.50%, P 0.030%-0.150%. The silicon-free semi-steel includes the following mass contents: C 2.5%-4.0%, Si 0%, Mn 0.01%-0.05%, P 0.028%-0.150%. At the end of converter blowing, the composition of the end molten steel can be precisely controlled within the following mass content range according to the composition requirements of the specific steel grade: C 0.08%-0.20%, P≤0.006%, especially when the mass content of the end carbon is increased to the control upper limit of 0.20%, the mass content of the end P can still be stably controlled at a level of ≤0.006%, and the mass content of phosphorus after steel tapping can be controlled to ≤0.003%.

[0027] In a preferred embodiment, in step S3, the oxygen flow rate of the converter blowing is 22000 Nm 3 / h~38000Nm 3 / h, and the oxygen lance position is controlled at 1.3m-1.5m. In step S4, within 1min-2min of the start of converter blowing, 1t-2t / furnace of active lime is added for slagging, the purpose of which is to quickly increase the CaO content in the converter and combine with the large amount of FeO produced by the blowing of oxygen to form a CaO-FeO binary slag system.

[0028] In a preferred embodiment, in the early stage of converter blowing, the mass content of FeO is ≥45%, so the CaO-FeO binary slag system is in liquid state and has good fluidity in the early stage of converter blowing. A large amount of P element in the molten steel in the early stage of converter blowing is oxidized to generate P2O5. Since P2O5 is an acidic substance and the CaO-FeO binary slag system is a pure alkaline slag, the CaO-FeO binary slag system has a strong ability to fix P2O5. Therefore, the P content in the molten steel can be greatly reduced in the early stage of blowing.

[0029] When the FeO content drops to 30% to 40% in the middle of converter blowing, the CaO-FeO binary slag system will experience a slight "drying out" phenomenon. At this time, the "drying out" phenomenon of the slag can be alleviated by appropriately increasing the oxygen supply and raising the oxygen lance position. In a preferred embodiment, the oxygen flow rate is increased to 40,000 Nm 3 / h~50000Nm 3 / h, raise the oxygen lance position to 1.8m ~ 3.0m.

[0030] It should be understood by those skilled in the art that, unlike the prior art CaO-SiO2-FeO ternary slag system "drying back" to generate high melting point and high adhesiveness calcium orthosilicate and calcium metasilicate, the present invention's CaO-FeO binary slag system "drying back" mainly generates highly active and weakly adhesive CaO, which is no different from continuing to add CaO slagging agent into the converter, so the oxygen gun will not be adhered to the extent that it cannot be cleaned during the "drying back" process. In addition, the weak oxidizing substance P2O5 in calcium phosphate will not be replaced by SiO2 with stronger acidity during the "drying back" process, so the present invention's CaO-FeO binary slag system will not be rephosphorized in the middle stage of converter blowing, and compared with the prior art CaO-SiO2-FeO ternary slag system, the present invention's CaO-FeO binary slag system still has a strong dephosphorization ability in the middle stage of converter blowing.

[0031] In the later stage of converter blowing, with the increase of temperature and FeO content in slag, the dephosphorization capacity of converter blowing in the later stage is further enhanced. Since the dephosphorization capacity of the present invention is better than the dephosphorization capacity of the CaO-SiO2-FeO ternary slag system in the prior art, the control target of high carbon, low oxygen and low phosphorus is achieved at the end of converter blowing, the mass content of terminal carbon is controlled to be 0.08% to 0.20%, the terminal oxygen activity is ≤200ppm, the phosphorus content of molten steel is controlled to reach P≤0.006%, and the mass content of phosphorus returned after steelmaking is ≤0.003%.

[0032] In a preferred embodiment, the method of the present invention takes 5-7 furnaces as a production cycle, and performs a slag pouring operation after producing 5-7 furnaces. The first 4-6 furnaces in each production cycle adopt the whole furnace slag smelting, and the last furnace is smelted after smelting. (CaO-FeO binary slag system slag making method has less slag and stronger dephosphorization effect. There is no need to perform slag pouring operation for continuous production of 4-6 furnaces, which is a non-slag pouring furnace. The 5th to 7th furnaces perform slag pouring operation, and the furnaces in which the slag pouring operation is performed are slag pouring furnaces). At the end of the converter blowing of the non-slag pouring furnace, all the slag is left in the converter to be used for the next furnace silicon-free semi-steel blowing. Since the slag obtained by the CaO-FeO binary slag system slag making method of the present invention is less, and the slag fluidity during converter tapping is weaker than that of the CaO-SiO2-FeO ternary slag system of the prior art, there is almost no slag pouring during the converter tapping process, and all the CaO-FeO slag is retained in the converter and does not enter the ladle with the molten steel, and the return P is ≤0.003% after tapping. After 4-6 furnaces of continuous production without slag dumping, the phosphorus content in the reused CaO-FeO slag continues to increase, and the slag volume also increases due to repeated smelting, so slag dumping operations are required in the 5th to 7th furnaces.

[0033] The 4-6 furnaces (non-slag dumping furnaces) with full slag retention all use CaO-FeO binary slag system or binary slag system with CaO-FeO as the main component for smelting. During the non-slag dumping furnace, the previous furnace is blown without slag dumping and the next furnace is blown directly. In the slag dumping furnace, the CaO-SiO2-FeO ternary slag system used consistently at home and abroad is used for smelting. In the middle and late stages of converter blowing, 500 kg to 1000 kg of slag-making agent containing SiO2 is added per furnace to transform the CaO-FeO slag into the CaO-SiO2-FeO ternary slag system with better fluidity during slag dumping. The purpose is to prevent a large amount of visible iron from being entrained in the slag of the slag dumping furnace, which increases iron loss. Alternatively, in the slag pouring furnace, the smelting method without adding SiO2 components is continued. This slag pouring furnace needs to add flux such as fluorite or high-alumina slag regulator (the main component is Al2O3) in the later stage of converter blowing to improve the fluidity of CaO-FeO slag. When the total amount of flux added is 300 kg to 500 kg / furnace, the fluidity of the slag is significantly improved during slag pouring, and the purpose of reducing iron loss in the slag is achieved at the same time. Those skilled in the art should understand that, during the converter blowing process, the present invention does not add silicon-containing substances into the converter during non-slag pouring cycles, such as silicon-containing slag-forming agents (such as quartz sand, SiO2-containing composite slag, etc.), silicon-containing temperature raising agents (such as ferrosilicon), etc., and the present invention only adds SiO2-containing slag-forming agents during the slag pouring cycles.

[0034] In a preferred embodiment, in step S3 or step S30, a slag-forming agent such as cold pressed blocks rich in FeO may be added into the converter to adjust the FeO content in the binary slag system CaO-FeO.

[0035] like Figure 3 As shown, the process of manufacturing a binary slag system with CaO-FeO as the main component in a non-slag dumping furnace includes the following steps: S10, performing converter blowing and desiliconization on blast furnace molten iron to obtain silicon-free semi-steel; S20, adding silicon-free semi-steel into the converter, and adding scrap steel into the converter at the same time. Since the silicon element brought in by the scrap steel is oxidized into SiO2, the mass ratio of the scrap steel to the silicon-free semi-steel is controlled to be ≤15%, so as to strictly control the mass content of SiO2 in the converter slag after adding the scrap steel to be ≤1.5%; S30, blowing oxygen into the converter to produce a large amount of FeO; S40, adding active lime into the converter to provide CaO, thereby forming a binary slag system with CaO-FeO as main components.

[0036] The difference between manufacturing a binary slag system with CaO-FeO as the main component in a non-slag pouring furnace and manufacturing a binary slag system with CaO-FeO in a non-slag pouring furnace is that, compared with step S2 of the latter, the former additionally adds scrap steel in step S20, so the heat source of the scrap steel can be used, and no heat waste will be caused. In addition, since the scrap steel contains part of the silicon element, the mass ratio of the added scrap steel to the silicon-free semi-steel is limited to ≤15%, so that the mass content of SiO2 in the converter slag can be controlled to ≤1.5%. Although the binary slag system with CaO-FeO as the main component contains SiO2, the trace content (≤1.5%) of SiO2 in the slag can be ignored, so it will not affect the dephosphorization ability of the binary slag system with CaO-FeO as the main component, so the binary slag system with CaO-FeO as the main component and the CaO-FeO binary slag system have comparable dephosphorization abilities. Except for step S20, the process conditions for producing a binary slag system with CaO—FeO as a main component in a non-slag dumping furnace and the process conditions for producing a binary slag system with CaO—FeO as a main component in a non-slag dumping furnace are the same.

[0037] The present invention is applicable to enterprises that use silicon-free semi-steel or silicon-free molten iron for converter steelmaking. In the converter steelmaking process, by manufacturing CaO-FeO binary slag system or CaO-FeO as the main component binary slag system steelmaking, rapid dephosphorization in the early stage of smelting and less slag smelting can be achieved, and steel grades with P≤0.006% can be stably produced. The present invention is not applicable to converter steelmaking operations using full molten iron as the main raw material with a silicon content of ≥0.05%.

[0038] The present invention also provides a method for silicon-free semi-steel steelmaking, which comprises adopting the above-mentioned slag-making method for semi-steel steelmaking to manufacture a CaO-FeO binary slag system in a non-slag-dumping furnace, or manufacturing a binary slag system with CaO-FeO as the main component in a non-slag-dumping furnace.

[0039] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0040] Example 1-1 The method for producing a CaO-FeO binary slag system in a non-slag dumping furnace comprises the following steps: S1. Blowing and desiliconizing blast furnace iron to obtain silicon-free semi-steel. The blast furnace iron comprises the following components by mass content: C 3.6%, Si 0.10%, Mn 0.05%, P 0.030%. The silicon-free semi-steel comprises the following components by mass content: C 3.4%, Si 0%, Mn 0.02%, P 0.028%.

[0041] S2, adding silicon-free semi-steel into the converter; S3, blowing oxygen into the converter to produce a large amount of FeO. The oxygen flow rate of the converter is 22000 Nm 3 / h, the oxygen lance position is controlled at 1.3m.

[0042] S4. Add active lime into the converter to provide CaO, thereby forming a CaO-FeO binary slag system. 1 t / furnace of active lime is added within 1 minute after the start of converter blowing.

[0043] In the early stage of converter blowing, the FeO mass content is 45%. When the FeO mass content drops to 30% in the middle stage of converter blowing, the oxygen flow rate is increased to 40000Nm 3 / h, raise the oxygen lance position to 1.8m.

[0044] After 4 heats of smelting with slag left in the whole furnace, the slag pouring operation is carried out after the 5th heat of smelting. In the slag pouring heat, 500kg of slag-making agent containing SiO2 is added in the middle and late stages of converter blowing.

[0045] At the end of converter blowing, the composition of the final molten steel in the heat includes the following components by mass: C 0.09%, P 0.004%, and the mass content of rephosphorus after steelmaking is 0.001%.

[0046] Example 1-2 In a non-slag dumping furnace, a binary slag system with CaO-FeO as the main component is manufactured. The only difference between Example 1-2 and Example 1-1 is that scrap steel is simultaneously added to the converter in step S20, wherein the mass ratio of scrap steel to silicon-free semi-steel is 15%, so as to control the mass content of SiO2 in the converter slag to be less than 1.5%.

[0047] At the end point of converter blowing, the composition of the final molten steel in the heat includes the following components by mass: C 0.08%, P 0.005%, and the mass content of rephosphorus after steel tapping is 0.001%.

[0048] Example 2-1 The method for producing a CaO-FeO binary slag system in a non-slag dumping furnace comprises the following steps: S1. Blowing and desiliconizing blast furnace iron to obtain silicon-free semi-steel. The blast furnace iron comprises the following components by mass content: C 4.0%, Si 0.50%, Mn 0.20%, P 0.090%. The silicon-free semi-steel comprises the following components by mass content: C 3.7%, Si 0%, Mn 0.04%, P 0.089%.

[0049] S2, adding silicon-free semi-steel into the converter; S3, blowing oxygen into the converter to produce a large amount of FeO. The oxygen flow rate of the converter is 30000 Nm 3 / h, the oxygen lance position is controlled at 1.4m.

[0050] S4. Add active lime into the converter to provide CaO, thereby forming a CaO-FeO binary slag system. 1.5 t / furnace of active lime is added within 1.5 min after the start of converter blowing.

[0051] In the early stage of converter blowing, the FeO mass content is 46%. When the FeO mass content drops to 35% in the middle stage of converter blowing, the oxygen flow rate is increased to 45000Nm 3 / h, raise the oxygen lance position to 2.2m.

[0052] After 5 heats of slag smelting, the slag pouring operation was carried out after the 6th heat of smelting. In the slag pouring heat, 1000kg of slag-making agent containing SiO2 was added in the middle and late stages of converter blowing.

[0053] At the end point of converter blowing, the composition of the final molten steel includes the following components by mass: C 0.20%, P 0.003%, and the mass content of phosphorus resorption after steel tapping is 0.002%.

[0054] Example 2-2 In a non-slag dumping furnace, a binary slag system with CaO-FeO as the main component is manufactured. The only difference between Example 2-2 and Example 2-1 is that scrap steel is simultaneously added to the converter in step S20, wherein the mass ratio of scrap steel to silicon-free semi-steel is 13% to control the mass content of SiO2 in the converter slag to be less than 1.5%.

[0055] At the end point of converter blowing, the composition of the final molten steel includes the following components by mass: C 0.19%, P 0.003%, and the mass content of rephosphorus after steelmaking is 0.001%.

[0056] Example 3-1 The method for producing a CaO-FeO binary slag system in a non-slag dumping furnace comprises the following steps: S1. Blowing and desiliconizing blast furnace iron to obtain silicon-free semi-steel. The blast furnace iron comprises the following components by mass: C 4.5%, Si 0.95%, Mn 0.50%, P 0.150%. The silicon-free semi-steel comprises the following components by mass: C 4.0%, Si 0%, Mn 0.05%, P 0.149%.

[0057] S2, adding silicon-free semi-steel into the converter; S3, blowing oxygen into the converter to produce a large amount of FeO. The oxygen flow rate of the converter is 38000 Nm 3 / h, the oxygen lance position is controlled at 1.5m.

[0058] S4. Add active lime into the converter to provide CaO, thereby forming a CaO-FeO binary slag system. 2 t / furnace of active lime is added within 2 minutes after the start of converter blowing.

[0059] In the early stage of converter blowing, the FeO mass content is 47%. When the FeO mass content drops to 40% in the middle stage of converter blowing, the oxygen flow rate is increased to 50000 Nm 3 / h, raise the oxygen lance position to 3.0m.

[0060] After 6 furnaces of slag smelting, the slag pouring operation was carried out after the 7th furnace. In the slag pouring furnace, 800kg of slag-making agent containing SiO2 was added in the middle and late stages of converter blowing.

[0061] At the end point of converter blowing, the composition of the final molten steel includes the following components by mass content: C 0.13%, P 0.003%, and the mass content of phosphorus regeneration after steel tapping is 0.001%.

[0062] Example 3-2 In a non-slag dumping furnace, a binary slag system with CaO-FeO as the main component is manufactured. The only difference between Example 3-2 and Example 3-1 is that scrap steel is simultaneously added to the converter in step S20, wherein the mass ratio of scrap steel to silicon-free semi-steel is 11% to control the mass content of SiO2 in the converter slag to be less than 1.5%.

[0063] At the end point of converter blowing, the composition of the final molten steel includes the following components by mass: C 0.12%, P 0.002%, and the mass content of phosphorus regeneration after steel tapping is 0.001%.

[0064] Example 3-3 In the non-slag pouring furnace, a CaO-FeO binary slag system is manufactured. The difference between Example 3-3 and Example 3-1 is that the smelting is continued by the method without adding SiO2 component, but in the slag pouring furnace, a solvent is added in the later stage of converter blowing, and 200kg fluorite and 300kg high alumina slag adjusting agent are added.

[0065] At the end point of converter blowing, the composition of the final molten steel includes the following components by mass: C 0.12%, P 0.002%, and the mass content of phosphorus regeneration after steel tapping is 0.001%.

[0066] Comparative Example 1 The main difference between Comparative Example 1 and Example 1-1 is that in the silicon-free semi-steel steelmaking process, Comparative Example 1 adopts the slag making method of the prior art, and the converter slag manufactured from beginning to end is a CaO-SiO2-FeO ternary slag system. At the end of the converter blowing, the composition of the terminal molten steel includes the following components by mass content: C 0.005%, P 0.012%, and the mass content of rephosphorization after steel tapping is 0.004%.

[0067] Comparative Example 2 The main difference between Comparative Example 2 and Example 2-1 is that in the silicon-free semi-steel steelmaking process, Comparative Example 2 adopts the slag making method of the prior art, and the converter slag manufactured from beginning to end is a CaO-SiO2-FeO ternary slag system. At the end of the converter blowing, the composition of the terminal molten steel includes the following components by mass content: C 0.010%, P 0.018%, and the mass content of rephosphorization after steel tapping is 0.004%.

[0068] Comparative Example 3 The main difference between Comparative Example 3 and Example 3-1 is that in the silicon-free semi-steel steelmaking process, Comparative Example 3 adopts the slag making method of the prior art, and the converter slag manufactured from beginning to end is a CaO-SiO2-FeO ternary slag system. At the end of the converter blowing, the composition of the terminal molten steel includes the following components by mass content: C 0.013%, P 0.019%, and the mass content of rephosphorization after steel tapping is 0.005%.

[0069] It should be particularly pointed out that the various components or steps in the above-mentioned embodiments can be cross-linked, replaced, added, or deleted with each other. Therefore, the combinations formed by these reasonable arrangements and combinations should also fall within the scope of protection of the present invention, and the scope of protection of the present invention should not be limited to the embodiments.

[0070] A person skilled in the art should understand that the discussion of any of the above embodiments is only exemplary and is not intended to imply that the scope of the disclosure of the embodiments of the present invention (including the claims) is limited to these examples; under the concept of the embodiments of the present invention, the technical features in the above embodiments or different embodiments can also be combined, and there are many other changes in different aspects of the embodiments of the present invention as described above, which are not provided in detail for the sake of simplicity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiments of the present invention should be included in the protection scope of the embodiments of the present invention.

Claims

1. A slag making method for silicon-free semi-steel steelmaking, characterized in that: The method comprises the steps of manufacturing a CaO-FeO binary slag system in a non-slag dumping furnace during a silicon-free semi-steel steelmaking process, or manufacturing a binary slag system with CaO-FeO as a main component in a non-slag dumping furnace.

2. The slag making method for semi-steel steelmaking according to claim 1, characterized in that: The production of CaO-FeO binary slag system in a non-slag dumping furnace includes the following steps: S1, blowing and desiliconizing the blast furnace molten iron to obtain silicon-free semi-steel; S2, adding silicon-free semi-steel into the converter; S3, blowing oxygen into the converter to produce a large amount of FeO; S4. Active lime is added into the converter to provide CaO, thereby forming a CaO-FeO binary slag system.

3. The slag making method for semi-steel steelmaking according to claim 1, characterized in that: The production of a binary slag system with CaO-FeO as the main component in a non-slag dumping furnace includes the following steps: S10, blowing and desiliconizing the blast furnace molten iron to obtain silicon-free semi-steel; S20, adding silicon-free semi-steel into the converter, and adding scrap steel into the converter at the same time, wherein the mass ratio of scrap steel to silicon-free semi-steel is ≤15%, so as to control the mass content of SiO2 in the converter slag to be ≤1.5%; S30, blowing oxygen into the converter to produce a large amount of FeO; S40, adding active lime into the converter to provide CaO, thereby forming a binary slag system with CaO-FeO as main components.

4. The slag making method for semi-steel steelmaking according to claim 2 or 3, characterized in that: In step S1 or step S10, Blast furnace hot metal includes the following components by mass: C 3.6% to 4.5%, Si 0.10% to 0.95%, Mn 0.05% to 0.50%, P 0.030% to 0.150%; Silicon-free semi-steel includes the following components by mass content: C 2.5%~4.0%, Si 0%, Mn 0.01%~0.05%, P0.028%~0.150%.

5. The slag making method for semi-steel steelmaking according to claim 4, characterized in that: At the end point of converter blowing, the composition of the end point molten steel includes the following components by mass content: C 0.08%~0.20%, P≤0.006%, and the mass content of phosphorus returned after steelmaking is ≤0.003%.

6. The slag making method for semi-steel steelmaking according to claim 2 or 3, characterized in that: In step S3 or step S30, the oxygen flow rate of the converter blowing is 22000 Nm 3 / h~38000Nm 3 / h, the oxygen lance position is controlled at 1.3m~1.5m; In step S4 or step S40, 1 t to 2 t / furnace of active lime is added within 1 to 2 minutes after the start of converter blowing.

7. The slag making method for semi-steel steelmaking according to claim 6, characterized in that: In the early stage of converter blowing, the mass content of FeO is ≥45%; When the FeO content drops to 30% to 40% in the middle of the converter blowing, the oxygen flow rate is increased to 40,000 Nm 3 / h~50000Nm 3 / h, raise the oxygen lance position to 1.8m ~ 3.0m.

8. The slag making method for semi-steel steelmaking according to claim 2 or 3, characterized in that: Take 5-7 furnaces as one production cycle, and perform one slag dumping operation after producing 5-7 furnaces. The first 4-6 furnaces in each production cycle adopt full furnace slag smelting, and the last furnace is smelted after smelting. Among them, the 4-6 furnaces that retain all slag all adopt CaO-FeO binary slag system or binary slag system with CaO-FeO as main components for smelting; In the slag pouring furnace, the CaO-SiO2-FeO ternary slag system is used for smelting, wherein 500 kg to 1000 kg / furnace of slag-making agent containing SiO2 is added in the middle and late stages of converter blowing; or, In the slag pouring furnace, the flux fluorite or high-alumina slag adjusting agent is added in the later stage of converter blowing, and the total amount of flux added is 300 kg ~ 500 kg / furnace.

9. The slag making method for semi-steel steelmaking according to claim 2 or 3, characterized in that: In step S3 or step S30, FeO-rich cold pressed blocks may be added into the converter to adjust the FeO content in the binary slag system CaO-FeO.

10. A method for making silicon-free semi-steel steel, characterized in that: The method comprises adopting the slag-making method for semi-steelmaking according to any one of claims 1 to 9 to manufacture a CaO-FeO binary slag system in a non-slag-dumping furnace, or manufacturing a binary slag system with CaO-FeO as the main component in a non-slag-dumping furnace.

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