Low-carbon steel smelting method based on BOF-VD-LF

Abstract

The invention provides a low-carbon steel smelting method based on BOF-VD-LF, and belongs to the field of low-carbon steel production. The method comprises the following steps: carrying out converter blowing on molten iron to obtain first molten steel; the first molten steel is subjected to converter tapping, and second molten steel with the set carbon content is obtained; carrying out temperature measurement and first oxygen determination on the second molten steel entering the VD refining station to obtain the entering temperature and the oxygen content; carrying out VD refining on the second molten steel entering the station after VD refining, and judging whether metallized pellets are added into the second molten steel or not according to the set carbon content and oxygen content to obtain third molten steel with the target carbon content; and performing LF refining on the third molten steel to obtain the molten steel for the low-carbon steel. In the VD refining process, a vacuum environment is used for promoting carbon-oxygen reaction in molten steel, and efficient decarburization is achieved. And meanwhile, due to the addition of the metallized pellets, the oxidability of the molten steel is improved, and the carbon-oxygen reaction is more sufficient. Therefore, the generation of aluminum oxide inclusions is reduced.

Description

Technical Field

[0001] The present application relates to the technical field of low-carbon steel production, and in particular to a low-carbon steel smelting method based on BOF-VD-LF. Background Art

[0002] Low carbon steel, also known as mild steel, is a carbon steel with a carbon content of less than 0.25%. Due to its good machinability and weldability, low carbon steel is often used to make parts such as chains, rivets, bolts, shafts, etc. It is also widely used in construction, automobiles, machinery and other fields.

[0003] RH furnaces can significantly reduce the impurity content in molten steel and improve the purity of molten steel through vacuum degassing, decarburization and other treatment processes. Currently, most steel mills use RH furnaces to produce low-carbon steel. However, the consumption of pure aluminum in the production of low-carbon steel using RH furnaces is too large, and a large amount of aluminum oxide inclusions are easily generated. Aluminum oxide inclusions damage the steel matrix, become the origin or cause of cracks, and damage the quality of steel. Therefore, how to reduce the number of aluminum oxide inclusions in low-carbon steel is a technical problem that needs to be solved urgently. Summary of the invention

[0004] The present application provides a low-carbon steel smelting method based on BOF-VD-LF to solve the following technical problem: how to reduce the amount of alumina inclusions in low-carbon steel.

[0005] The present application provides a low-carbon steel smelting method based on BOF-VD-LF, the method comprising:

[0006] The molten iron is blown in a converter to obtain the first molten steel;

[0007] tapping the first molten steel into a converter to obtain a second molten steel having a set carbon content;

[0008] The second molten steel entering the VD refining station is subjected to temperature measurement and first oxygen determination to obtain the entering station temperature and oxygen content;

[0009] Performing VD refining on the second molten steel after VD refining, and determining whether to add metallized pellets to the second molten steel according to the set carbon content and the oxygen content, to obtain a third molten steel with a target carbon content; and

[0010] The third molten steel is subjected to LF refining to obtain molten steel for low carbon steel.

[0011] Optionally, the determining whether to add metallized pellets to the second molten steel according to the set carbon content and the oxygen content includes:

[0012] According to the set carbon content and the set oxygen content, it is determined whether to add metallized pellets to the second molten steel; wherein

[0013] If the set carbon content and the set oxygen content satisfy the following relationship: [C1]-[O]>0.015%, adding a set mass of metallized pellets to the second molten steel;

[0014] If the set carbon content and the oxygen content satisfy the following relationship: [C1]-[O]≤0.015%, no metallized pellets are added;

[0015] In the formula, [C1] represents the set carbon content; [O] represents the oxygen content.

[0016] Optionally, the added mass of the metallized pellets satisfies the following relationship:

[0017] [C2]=[C1]-[(120+280*m)*0.0001+[O]]*0.75

[0018] In the formula, [C2] represents the value before the target carbon content %; [C1] represents the value before the set carbon content %; m represents the value of the added mass of metallized pellets, and the unit of m is t; [O] represents the value before the oxygen content %.

[0019] Optionally, the chemical components of the metallized pellets include, by mass fraction: Fe: 25% to 35%, CaO: 5% to 10%, Al2O3: 1% to 3%, ZnO: 1% to 3%, Na2O: 1% to 3%, K2O: 0.1% to 2%, and FeO: 40% to 60%.

[0020] Optionally, in terms of mass fraction, the set carbon content is 0.05% to 0.08%, the target carbon content is less than 0.01%, and the oxygen content is 0.025% to 0.05%.

[0021] Optionally, the deep vacuum argon flow rate of the VD refining is 180NL / min to 220NL / min, and the deep vacuum time of the VD refining is 3min to 8min.

[0022] Optionally, the carbon content of the first molten steel is 0.06% to 0.09% by mass; and / or the temperature of the first molten steel is 1630°C to 1650°C.

[0023] Optionally, no aluminum product is added during the process of tapping steel from the converter.

[0024] Optionally, the carbon content of the molten steel for low carbon steel is less than 0.025% and the oxygen content is 0.0002% to 0.0005% by mass.

[0025] Optionally, the number of alumina inclusions in the molten steel for low carbon steel is less than 0.01 / mm 2 , wherein the diameter of the alumina inclusions is ≥20um.

[0026] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0027] The present application provides a low-carbon steel smelting method based on BOF-VD-LF, comprising: blowing molten iron in a converter to obtain a first molten steel; tapping the first molten steel in a converter to obtain a second molten steel with a set carbon content; measuring the temperature and first oxygen determination of the second molten steel entering the VD refining station to obtain the station entry temperature and oxygen content; performing VD refining on the second molten steel after VD refining, and determining whether to add metallized pellets to the second molten steel according to the set carbon content and the oxygen content to obtain a third molten steel with a target carbon content; and performing LF refining on the third molten steel to obtain molten steel for low-carbon steel. First, a converter is used to increase the carbon content in the molten steel, and then a vacuum environment is used in the VD refining process to promote the carbon-oxygen reaction in the molten steel to achieve efficient decarburization. At the same time, the addition of metallized pellets increases the oxidizability of the molten steel, and the carbon-oxygen reaction is more sufficient, which helps to further reduce the carbon content in the molten steel and remove excess oxygen. The sufficient carbon-oxygen reaction reduces the dependence on aluminum deoxidation, thereby reducing the generation of aluminum oxide inclusions. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0029] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0030] Figure 1 A schematic flow chart of a low-carbon steel smelting method based on BOF-VD-LF provided in an embodiment of the present application. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0032] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have 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 numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0033] In addition, in the description of the specification of the present application, the terms "including", "comprising", etc. mean "including but not limited to". In this article, relational terms such as "first" and "second", etc. are only 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 these entities or operations. In this article, "and / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. Wherein A and B can be singular or plural. In this article, "at least one" means one or more, and "plurality" means two or more. "At least one", "the following at least one item (items)" or similar expressions refer to any combination of these items, including any combination of single items (items) or plural items (items). For example, "at least one of a, b, or c", or "at least one of a, b and c", can both mean: a, b, c, ab (i.e. a and b), ac, bc or abc, where a, b, c can be single or plural, respectively.

[0034] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0035] Figure 1A schematic flow chart of a low-carbon steel smelting method based on BOF-VD-LF provided in an embodiment of the present application.

[0036] See also Figure 1 The present application provides a low-carbon steel smelting method based on BOF-VD-LF, the method comprising:

[0037] S1, blowing the molten iron in a converter to obtain the first molten steel;

[0038] The molten iron is fed into the converter and blown with oxygen to make the impurities in the molten iron react with oxygen to generate gas or compounds, thereby reducing the impurity content in the molten steel. The main purpose of this stage is to improve the purity of the molten steel and preliminarily adjust the carbon content.

[0039] In some embodiments, the carbon content of the first molten steel is 0.06% to 0.09% by mass; and / or the temperature of the first molten steel is 1630°C to 1650°C.

[0040] The appropriate converter end temperature is conducive to the deoxidation reaction in the VD process, and the appropriate carbon content can better promote the carbon-oxygen reaction repeatedly, reduce the amount of aluminum products added and reduce costs. For example, the carbon content of the first molten steel can be 0.06%, 0.065%, 0.07%, 0.075%, 0.08%, 0.085%, 0.09%, etc., and the temperature of the first molten steel can be 1630°C, 1635%, 1640%, 1645%, 1650°C, etc.

[0041] S2, tapping the first molten steel into a converter to obtain a second molten steel with a set carbon content;

[0042] The first molten steel after blowing is poured out from the converter to obtain the second molten steel with a set carbon content. The carbon content setting at this stage needs to be determined according to the subsequent process requirements and steel grade characteristics.

[0043] In some embodiments, no aluminum product is added during the steel tapping process of the converter.

[0044] The molten steel will be stirred when it is being tapped. After the aluminum products are added, the aluminum products and the molten steel come into contact with each other in the air and burn, resulting in waste of the aluminum products.

[0045] S3, measuring the temperature of the second molten steel entering the VD refining station and performing a first oxygen determination to obtain the station entry temperature and oxygen content;

[0046] The second molten steel entering the VD refining station is temperature-measured and oxygen-determined, and the entering temperature and oxygen content are recorded. The entering temperature and oxygen content data are important bases for adjusting process parameters in the subsequent VD refining process.

[0047] In some embodiments, the inlet temperature is 1580°C to 1590°C.

[0048] The entry temperature is limited to 1580°C to 1590°C, which is beneficial to the VD process to promote the deoxidation reaction. For example, the entry temperature can be 1580°C, 1582°C, 1584°C, 1586°C, 1588°C, 1590°C, etc.

[0049] S4, performing VD refining on the second molten steel after VD refining, and determining whether to add metallized pellets to the second molten steel according to the set carbon content and the oxygen content, to obtain a third molten steel with a target carbon content;

[0050] The second molten steel is sent to the VD refining furnace for vacuum degassing and decarburization. According to the set carbon content and oxygen content, the carbon-oxygen reaction balance in the molten steel is adjusted by adding metallized pellets to achieve the control of the target carbon content.

[0051] In some embodiments, the step of determining whether to add metallized pellets to the second molten steel according to the set carbon content and the oxygen content includes:

[0052] According to the set carbon content and the set oxygen content, it is determined whether to add metallized pellets to the second molten steel; wherein

[0053] If the set carbon content and the set oxygen content satisfy the following relationship: [C1]-[O]>0.015%, adding a set mass of metallized pellets to the second molten steel;

[0054] If the set carbon content and the oxygen content satisfy the following relationship: [C1]-[O]≤0.015%, no metallized pellets are added;

[0055] In the formula, [C1] represents the set carbon content; [O] represents the oxygen content.

[0056] When the carbon content of the second molten steel after the converter is discharged is significantly different from the oxygen content of the VD entering the station (>0.015%), it indicates that the carbon content in the molten steel is relatively high and the oxygen content is relatively low. In order to promote the carbon-oxygen reaction in the molten steel, further reduce the carbon content, and ensure the purity and quality of the molten steel, it is necessary to add metallized pellets to the molten steel. The oxides in the metallized pellets can increase the oxidizability of the molten steel and promote the carbon-oxygen reaction, thereby achieving the decarburization goal. After the addition of the metallized pellets, the carbon-oxygen reaction in the molten steel will be significantly promoted under the vacuum environment of VD refining. As the reaction proceeds, the carbon content in the molten steel will gradually decrease.

[0057] In some embodiments, the added mass of the metallized pellets satisfies the following relationship:

[0058] [C2]=[C1]-[(120+280*m)*0.0001+[O]]*0.75

[0059] In the formula, [C2] represents the value before the target carbon content %; [C1] represents the value before the set carbon content %; m represents the value of the added mass of metallized pellets, and the unit of m is t; [O] represents the value before the oxygen content %.

[0060] The present invention determines the addition amount of metallized pellets by theoretical calculation based on the carbon content of the second molten steel after the converter is tapped, the oxygen content when the VD enters the station and the target carbon content (<0.01%), combined with the oxidation capacity and decarburization efficiency of the metallized pellets.

[0061] In some embodiments, the chemical components of the metallized pellets include, by mass fraction: Fe: 25% to 35%, CaO: 5% to 10%, Al2O3: 1% to 3%, ZnO: 1% to 3%, Na2O: 1% to 3%, K2O: 0.1% to 2%, and FeO: 40% to 60%.

[0062] FeO: As the main oxide in metallized pellets, FeO plays a key role in molten steel. It not only provides additional oxygen to the molten steel and promotes the carbon-oxygen reaction, but also helps to remove impurity elements in the molten steel, such as sulfur and phosphorus. Metallized pellets with high FeO content can more effectively increase the oxidizability of the molten steel, thereby accelerating the decarburization process. Na2O: Although the content of Na2O in metallized pellets is relatively low, it is also a strong oxidant. In molten steel, Na2O can work with other oxides to further increase the oxidizing ability of molten steel. However, it should be noted that excessive Na2O content may have an adverse effect on the quality of molten steel and subsequent treatment processes, so its addition amount needs to be reasonably controlled. Other oxides (such as CaO, Al2O3, ZnO, K2O): These oxides also play an important role in metallized pellets. They can not only work synergistically with FeO to improve the oxidizability of molten steel, but may also affect the physical and chemical properties of molten steel. For example, CaO can combine with sulfur in molten steel to form calcium sulfide precipitates, thereby removing sulfur from the molten steel; Al2O3 and ZnO may affect the microstructure and mechanical properties of the molten steel. Exemplarily, the Fe content can be 25%, 27%, 29%, 30%, 32%, 34%, 35%, etc., the CaO content can be 5%, 6%, 7%, 8%, 9%, 10%, etc., the Al2O3 content can be 1%, 1.2%, 1.5%, 2%, 2.5%, 3%, etc., the ZnO content can be 1%, 1.2%, 1.5%, 2%, 2.5%, 3%, etc., the Na2O content can be 1%, 1.2%, 1.5%, 2%, 2.5%, 3%, etc., the K2O content can be 0.1%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, etc., and the FeO content can be 40%, 45%, 50%, 55%, 60%, etc.

[0063] In some embodiments, the set carbon content is 0.05% to 0.08%, the target carbon content is less than 0.01%, and the oxygen content is 0.025% to 0.05%, calculated by mass fraction.

[0064] The carbon content of the second molten steel after the converter is tapped is limited to 0.05% to 0.08% and the oxygen content is limited to 0.025% to 0.05%, which can better match the carbon-oxygen reaction, reduce the amount of aluminum products added and reduce costs. For example, the carbon content can be set to 0.05%, 0.06%, 0.07%, 0.08%, etc., and the oxygen content can be set to 0.025%, 0.03%, 0.035%, 0.04%, 0.045%, 0.05%, etc.

[0065] In some embodiments, the deep vacuum argon flow rate of the VD refining is 180 NL / min to 220 NL / min, and the deep vacuum time of the VD refining is 3 min to 8 min.

[0066] In VD refining, argon is mainly used to promote the floating of gases and inclusions in molten steel and the decarburization reaction. The deep vacuum argon flow rate of VD refining is limited to 180NL / min~220NL / min, and the deep vacuum time of VD refining is 3min~8min, which can ensure that the molten steel is fully decarburized. Exemplarily, the deep vacuum argon flow rate of VD refining can be 180NL / min, 190NL / min, 200NL / min, 210NL / min, 220NL / min, etc., and the deep vacuum time of VD refining can be 3min, 4min, 5min, 6min, 7min, 8min, etc.

[0067] S5. The third molten steel is subjected to LF refining to obtain molten steel for low carbon steel.

[0068] The third molten steel after VD refining is sent to the LF refining furnace for further composition adjustment and temperature control. The LF refining furnace can accurately control the alloy element content and temperature in the molten steel to meet the performance requirements of the final product.

[0069] In some embodiments, the carbon content of the molten steel for low carbon steel is less than 0.025% and the oxygen content is 0.0002% to 0.0005% by mass.

[0070] In some embodiments, the number of alumina inclusions in the molten steel for low carbon steel is less than 0.01 / mm 2 , wherein the diameter of the alumina inclusions is ≥20um.

[0071] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are intended only to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for which specific conditions are not specified in the following examples are usually measured according to industry standards. If there is no corresponding industry standard, then the conditions recommended by the manufacturer are followed.

[0072] Example 1

[0073] This embodiment provides a low-carbon steel smelting method based on BOF-VD-LF, comprising the following steps:

[0074] S11, blowing the molten iron in a converter to obtain first molten steel; the carbon content of the first molten steel is 0.07%, and the temperature of the first molten steel is 1637° C.;

[0075] S21, tapping the first molten steel into a converter, without adding aluminum products during the tapping process, to obtain a second molten steel having a set carbon content; the carbon content of the second molten steel is 0.056%;

[0076] S31, measuring the temperature and performing the first oxygen determination on the second molten steel entering the VD refining station to obtain the entering station temperature and oxygen content; the entering station temperature is 1587° C., and the entering station oxygen content is 0.0375%;

[0077] S41, VD refining is performed on the second molten steel after VD refining, the carbon content of the second molten steel minus the oxygen content entering the station = 0.0185%, and metallized pellets need to be added to increase the oxidative decarburization of the molten steel to ensure that the carbon content at the end of VD is less than 0.01%. The amount of metallized pellets added is 0.5t, and the carbon content at the end of VD is calculated to be 0.0084% according to [C2] = [C1] - [(120 + 280*m) * 0.0001 + [O]] * 0.75, and the third molten steel with the target carbon content is obtained. The argon flow rate of deep vacuum treatment is 200NL / min and the time is 6min. The carbon content of the third molten steel after VD is actually 0.0076%;

[0078] S51, LF refining is performed on the third molten steel to obtain molten steel for low carbon steel, the carbon content of the molten steel for low carbon steel after LF furnace refining is 0.022%, and the O content is 0.0002%. The molten steel for low carbon steel is continuously cast to obtain low carbon steel, and the number of aluminum oxide inclusions (diameter ≥ 20um) in the low carbon steel is 0.007 pieces / mm 2 .

[0079] Example 2

[0080] This embodiment provides a low-carbon steel smelting method based on BOF-VD-LF, comprising the following steps:

[0081] S12, blowing the molten iron in a converter to obtain first molten steel; the carbon content of the first molten steel is 0.075%, and the temperature of the first molten steel is 1640° C.;

[0082] S22, tapping the first molten steel into a converter, without adding aluminum products during the tapping process, to obtain a second molten steel having a set carbon content; the carbon content of the second molten steel is 0.067%;

[0083] S32, measuring the temperature and performing the first oxygen determination on the second molten steel entering the VD refining station to obtain the entering station temperature and oxygen content; the entering station temperature is 1590° C., and the entering station oxygen content is 0.0305%;

[0084] S42, VD refining is performed on the second molten steel after VD refining - the oxygen content entering the station = 0.0365%, and metallized pellets need to be added to increase the oxidative decarburization of the molten steel to ensure that the carbon content at the end of VD is less than 0.01%. The amount of metallized pellets added is 1.3t, and the carbon content at the end of VD is calculated to be 0.0078% according to [C2] = [C1] - [(120 + 280*m) * 0.0001 + [O]] * 0.75, and the third molten steel with the target carbon content is obtained. The argon flow rate of deep vacuum treatment is 200NL / min and the time is 8min. The carbon content of the third molten steel after VD is actually 0.0070%;

[0085] S52, LF refining is performed on the third molten steel to obtain molten steel for low carbon steel, the carbon content of the molten steel for low carbon steel after LF furnace refining is 0.021%, and the O content is 0.0003%. The molten steel for low carbon steel is continuously cast to obtain low carbon steel, and the number of aluminum oxide inclusions (diameter ≥ 20um) in the low carbon steel is 0.006 pieces / mm 2 .

[0086] Comparative Example 1

[0087] This comparative example provides a low-carbon steel smelting method based on BOF-VD-LF, comprising the following steps:

[0088] S13, blowing the molten iron in a converter to obtain first molten steel; the carbon content of the first molten steel is 0.087%, and the temperature of the first molten steel is 1627° C.;

[0089] S23, tapping the first molten steel into a converter, without adding aluminum products during the tapping process, to obtain a second molten steel having a set carbon content; the carbon content of the second molten steel is 0.072%;

[0090] S33, measuring the temperature and performing the first oxygen determination on the second molten steel entering the VD refining station to obtain the entering station temperature and oxygen content; the entering station temperature is 1590° C., and the entering station oxygen content is 0.0354%;

[0091] S43, VD refining is performed on the second molten steel after VD refining, without adding metallized pellets, to obtain a third molten steel with a target carbon content, the argon flow rate of deep vacuum treatment is 200 NL / min and the time is 8 min, and the carbon content of the third molten steel after VD is actually 0.0192%;

[0092] S53, the third molten steel is subjected to LF refining to obtain molten steel for low carbon steel, the carbon content of the molten steel for low carbon steel after LF furnace refining is 0.026%, and the O content is 0.0007%. The molten steel for low carbon steel is continuously cast to obtain low carbon steel, and the number of aluminum oxide inclusions (diameter ≥ 20um) in the low carbon steel is 0.012 pieces / mm 2 .

[0093] Comparative Example 2

[0094] This comparative example provides a low-carbon steel smelting method based on BOF-VD-LF, comprising the following steps:

[0095] S13, blowing the molten iron in a converter to obtain first molten steel; the carbon content of the first molten steel is 0.073%, and the temperature of the first molten steel is 1635° C.;

[0096] S23, tapping the first molten steel into a converter, without adding aluminum products during the tapping process, to obtain a second molten steel having a set carbon content; the carbon content of the second molten steel is 0.062%;

[0097] S33, measuring the temperature and performing the first oxygen determination on the second molten steel entering the VD refining station to obtain the entering station temperature and oxygen content; the entering station temperature is 1578° C., and the entering station oxygen content is 0.0417%;

[0098] S43, VD refining is performed on the second molten steel after VD refining, without adding metallized pellets, to obtain a third molten steel with a target carbon content, the argon flow rate of deep vacuum treatment is 200 NL / min and the time is 8 min, and the carbon content of the third molten steel after VD is actually 0.0157%;

[0099] S53, the third molten steel is subjected to LF refining to obtain molten steel for low carbon steel, the carbon content of the molten steel for low carbon steel after LF furnace refining is 0.031%, and the O content is 0.0008%. The molten steel for low carbon steel is continuously cast to obtain low carbon steel, and the number of aluminum oxide inclusions (diameter ≥ 20um) in the low carbon steel is 0.012 pieces / mm 2 .

[0100] In addition, one or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

[0101] In the embodiment of the present invention, the BOF-VD-LF smelting method integrates multiple process steps such as converter blowing, VD vacuum refining and LF refining, thereby realizing the whole process control of molten steel from rough refining to refining.

[0102] In the embodiment of the present invention, high-precision control of the carbon content, oxygen content and alloy element content in molten steel can be achieved through accurate control and adjustment of each process step.

[0103] In the embodiment of the present invention, decarburization and deoxidation by carbon-oxygen reaction reduce the deoxidation cost; at the same time, the waste of alloy elements and the rework rate of molten steel are reduced through precise control, further reducing the production cost.

[0104] In the embodiment of the present invention, the low carbon steel has the characteristics of high purity, few inclusions, excellent mechanical properties, etc., and can meet the stringent requirements of high-end users on steel quality.

[0105] In the embodiment of the present invention, carbon deoxidation is used to reduce the deoxidation cost of aluminum products, and the consumption of pure aluminum is reduced by about 1.1kg / t per ton of steel (the original aluminum consumption per ton of steel is 4.0kg, and the aluminum consumption per ton of steel after improvement is 2.9kg), and the cost of aluminum products is reduced by about 19.8 yuan / ton of steel. The purity of molten steel is improved, and alumina inclusions are reduced, and the inclusion level (diameter ≥ 20um) is ≤ 0.01 / mm 2 .

[0106] The above description is only a specific implementation of the present application, so that those skilled in the art can 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 the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A low carbon steel smelting method based on BOF-VD-LF, characterized in that: The method comprises: The molten iron is blown in a converter to obtain the first molten steel; tapping the first molten steel into a converter to obtain a second molten steel having a set carbon content; The second molten steel entering the VD refining station is subjected to temperature measurement and first oxygen determination to obtain the entering station temperature and oxygen content; Performing VD refining on the second molten steel after VD refining, and determining whether to add metallized pellets to the second molten steel according to the set carbon content and the oxygen content, to obtain a third molten steel with a target carbon content; and The third molten steel is subjected to LF refining to obtain molten steel for low carbon steel.

2. The method according to claim 1, characterized in that The step of determining whether to add metallized pellets to the second molten steel according to the set carbon content and the set oxygen content comprises: According to the set carbon content and the set oxygen content, it is determined whether to add metallized pellets to the second molten steel; wherein If the set carbon content and the set oxygen content satisfy the following relationship: [C1]-[O]>0.015%, adding a set mass of metallized pellets to the second molten steel; If the set carbon content and the oxygen content satisfy the following relationship: [C1]-[O]≤0.015%, no metallized pellets are added; In the formula, [C1] represents the set carbon content; [O] represents the oxygen content.

3. The method according to claim 2, characterized in that The added mass of the metallized pellets satisfies the following relationship: [C2]=[C1]-[(120+280*m)*0.0001+[O]]*0.75 In the formula, [C2] represents the value before the target carbon content %; [C1] represents the value before the set carbon content %; m represents the value of the added mass of metallized pellets, and the unit of m is t; [O] represents the value before the oxygen content %.

4. The method according to claim 3, characterized in that Calculated by mass fraction, the chemical components of the metallized pellets include: Fe: 25% to 35%, CaO: 5% to 10%, Al2O3: 1% to 3%, ZnO: 1% to 3%, Na2O: 1% to 3%, K2O: 0.1% to 2%, and FeO: 40% to 60%.

5. The method according to claim 3, characterized in that: In terms of mass fraction, the set carbon content is 0.05% to 0.08%, the target carbon content is less than 0.01%, and the oxygen content is 0.025% to 0.05%.

6. The method according to claim 1, characterized in that The deep vacuum argon flow rate of the VD refining is 180NL / min to 220NL / min, and the deep vacuum time of the VD refining is 3min to 8min.

7. The method according to claim 1, characterized in that In terms of mass fraction, the carbon content of the first molten steel is 0.06% to 0.09%; and / or the temperature of the first molten steel is 1630° C. to 1650° C.

8. The method according to claim 1, characterized in that No aluminum products are added during the process of tapping the converter.

9. The method according to claim 1, characterized in that: Calculated by mass fraction, the carbon content of the molten steel for low carbon steel is less than 0.025%, and the oxygen content is 0.0002% to 0.0005%.

10. The method according to claim 1, characterized in that The number of aluminum oxide inclusions in the low carbon steel molten steel is less than 0.01 / mm 2 , wherein the diameter of the alumina inclusions is ≥20um.

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