Preparation method of high-chromium low-phosphorus steel

Abstract

The invention discloses a preparation method of high-chromium low-phosphorus steel, which comprises the following steps: carrying out dephosphorization treatment on a desulfurized molten iron raw material in a first converter to obtain dephosphorized molten steel in which the mass percentage content of phosphorus is less than or equal to 0.012 wt%; the dephosphorized molten steel is subjected to recarburization treatment, and dephosphorized recarburized molten steel is obtained; the dephosphorized and recarburized molten steel is subjected to silicon increasing treatment, silicon-increased molten steel is obtained, and the mass percentage content of the silicon element in the silicon-increased molten steel is 0.8 wt%-1.5 wt%; and the silicon-increased molten steel is subjected to carbon removing and chromium increasing treatment in the second converter, the high-chromium low-phosphorus molten steel is obtained, and the mass percentage content of chromium in the high-chromium low-phosphorus molten steel is larger than or equal to 8 wt%. According to the preparation method, the function distribution of the two converters is optimized, a complex stainless steel production process is divided into a dephosphorization converter process and a decarburization and chromium protection converter process, the dephosphorization converter process and the decarburization and chromium protection converter process are organically combined with an argon station treatment process, operation is easy and controllable, and the chromium yield is high.

Description

Technical Field

[0001] This application belongs to the field of metallurgical technology, and particularly relates to a method for preparing high-chromium and low-phosphorus steel. Background Art

[0002] Stainless steel belongs to alloy steel. Generally, the mass percentage content of chromium in stainless steel is greater than 10.5 wt%. There are two traditional methods for smelting stainless steel. One is the "two-step method", that is, the electric arc furnace (EAF) + argon oxygen decarburization furnace (AOD) or vacuum degassing furnace (VOD) method. The other is the "three-step method", that is, the EAF + converter (MRP, K-OBM or LD-OB) + VOD method, and the "basic oxygen furnace (BOF) + ladle furnace refining (LF) + vacuum circulation degassing (RH)" method developed after the 1980s. However, the existing smelting methods for producing high-chromium and low-phosphorus steel are all limited by the AOD furnace and the LF furnace. Summary of the Invention

[0003] The embodiment of this application provides a method for preparing high-chromium and low-phosphorus steel. By optimizing the function allocation of two converters, the complex stainless steel production process is split into a dephosphorization converter process and a decarburization and chromium-preserving converter process, and is organically combined with the argon station treatment process.

[0004] In the first aspect, a method for preparing high-chromium and low-phosphorus steel is provided, including: performing dephosphorization treatment on the desulfurized hot metal raw material in the first converter to obtain dephosphorized molten steel, wherein the mass percentage content of phosphorus element in the dephosphorized molten steel ≤ 0.012 wt%; performing carbon-increasing treatment on the dephosphorized molten steel to obtain dephosphorized and carbon-increased molten steel, wherein the mass percentage content of carbon element in the dephosphorized and carbon-increased molten steel is 1.4 wt% - 2.0 wt%; performing silicon-increasing treatment on the dephosphorized and carbon-increased molten steel to obtain silicon-increased molten steel, wherein the mass percentage content of silicon element in the silicon-increased molten steel is 0.8 wt% - 1.5 wt%; performing decarburization and chromium-increasing treatment on the silicon-increased molten steel in the second converter to obtain high-chromium and low-phosphorus molten steel, wherein the mass percentage content of chromium element in the high-chromium and low-phosphorus molten steel ≥ 8 wt%.

[0005] The method for preparing high-chromium and low-phosphorus steel of this application completes dephosphorization in the first converter, increases carbon during the tapping process of the first converter, increases silicon after the carbon-increasing is completed, and completes decarburization and chromium-increasing in the second converter. By optimizing the function allocation of two converters, the complex stainless steel production process is split into a dephosphorization converter process and a decarburization and chromium-preserving converter process, and is organically combined with the argon station treatment process. The operation is simple and controllable, and the chromium recovery rate is high.

[0006] In the first possible implementation, the temperature of the desulfurized hot metal raw material is ≥1300°C; and / or, the mass percentage of silicon element in the desulfurized hot metal raw material is 0.20 wt% - 0.60 wt%, and the mass percentage of phosphorus element is ≤0.09 wt%; and / or, the mass percentage of carbon element in the dephosphorized molten steel is ≤0.03 wt%; and / or, the temperature of the dephosphorized molten steel before carbon addition treatment is 1650°C - 1680°C.

[0007] Combined with the above possible implementation, the first converter blows argon at the bottom and oxygen at the top. The supply intensity of argon is 0.04 Nm 3 / (min·t) - 0.06 Nm 3 / (min·t), and the supply intensity of oxygen is 3.2 Nm 3 / (min·t) - 3.7 Nm 3 / (min·t); the second converter blows argon at the bottom and oxygen at the top. The supply intensity of argon is 0.04 Nm 3 / (min·t) - 0.06 Nm 3 / (min·t), and the supply intensity of oxygen is 3.2 Nm 3 / (min·t) - 3.7 Nm 3 / (min·t).

[0008] Combined with the above possible implementation, the dephosphorization treatment includes: adding 15 kg / ton - 30 kg / ton of lime to the desulfurized hot metal raw material in batches after the first predetermined time for slag formation, and performing shaking furnace slag pouring after the second predetermined time for slag formation to obtain the molten steel after the first dephosphorization treatment; adding 20 kg / ton - 30 kg / ton of lime to the molten steel after the first dephosphorization treatment, and then performing secondary slag formation in the shaking furnace until the end point to obtain dephosphorized molten steel, where the basicity of the final slag is 3.2 - 3.5.

[0009] Combined with the above possible implementation, the first predetermined time is 1 min - 3 min, the second predetermined time is 4 min - 6 min, and the amount of poured slag accounts for 50% - 85% of the total slag amount.

[0010] Combined with the above possible implementation, the decarburization and chromium addition treatment includes: adding lime and light burned magnesia balls to the silicon-added molten steel for slag formation and then heating to a predetermined temperature; adjusting the supply intensity to the first oxygen supply intensity and the first argon supply intensity, and then adding ferrosilicon and high-carbon ferrochrome to the molten steel until the content of chromium element in the molten steel reaches the predetermined content; adjusting the supply intensity to the second argon intensity and stopping oxygen supply, stirring the molten steel, and adding ferrosilicon to reduce chromium oxides in the slag.

[0011] Combined with the above possible implementation, the first argon supply intensity is 0.09 Nm 3 / (min·t) - 0.15 Nm 3 / (min·t), the first oxygen supply intensity is 1.5 Nm 3 / (min·t) to 2.2 Nm 3 / (min·t); the second argon supply intensity is 0.09 Nm 3 / (min·t) to 0.15 Nm 3 / (min·t).

[0012] Combined with the above possible implementation manners, the predetermined temperature ≥ 1650 °C; and / or, the addition amount of ferrosilicon is 4.5 kg / ton to 6.0 kg / ton; high-carbon ferrochrome is added in multiple times, 1000 kg to 2000 kg each time, and the interval time between every two additions is 3 min to 4 min; and / or, the predetermined content of chromium element is 80% to 85% of the target content; and / or, the treatment time of chromium oxide in ferrosilicon reduction slag is 8 min to 10 min.

[0013] Combined with the above possible implementation manners, temperature measurement and sampling are carried out after the decarburization and chromium enrichment treatment.

[0014] Combined with the above possible implementation manners, alloy is added for adjustment according to the sampling result, and the steel is tapped after the composition and temperature meet the requirements. Brief Description of the Drawings

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required to be used in the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0016] Figure 1 is the process flow chart of the preparation method of the present application. Detailed Embodiments

[0017] The features and exemplary embodiments of each aspect of the present application will be described in detail below. In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the drawings and specific embodiments. It should be understood that the specific embodiments described herein are only intended to explain the present application, rather than to limit the present application. For those skilled in the art, the present application can be implemented without some of these specific details. The following description of the embodiments is only to provide a better understanding of the present application by showing examples of the present application.

[0018] For simplicity, only some numerical ranges are explicitly disclosed in this application. However, any lower limit can be combined with any upper limit to form a range not explicitly recited; and any lower limit can be combined with other lower limits to form a range not explicitly recited, and similarly any upper limit can be combined with any other upper limit to form a range not explicitly recited. In addition, although not explicitly recited, each point or single value between the range endpoints is included in this range. Thus, each point or single value can be used as its own lower or upper limit and combined with any other point or single value or combined with other lower or upper limits to form a range not explicitly recited.

[0019] The above summary of the invention of this application is not intended to describe every disclosed embodiment or every implementation in this application. The following description more specifically illustrates exemplary embodiments. Throughout the application, guidance is provided through a series of embodiments, which can be used in various combinations. In each instance, the listing is only a representative group and should not be construed as exhaustive. In addition, the terms "first" and "second" are used only for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of this application, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically defined.

[0020] There are two traditional smelting methods for high-chromium steel. One is the "two-step method", namely the EAF+AOD or VOD method, and the other is the "three-step method", namely the EAF+converter (MRP, K-OBM or LD-OB)+VOD method. After the 1980s, someone developed the "BOF+LF+RH" method to produce ferritic, austenitic, and martensitic stainless steels.

[0021] The "two-step method" or "three-step method" is only applicable to the production of stainless steel in an EAF furnace. Limited by raw material conditions, high-chromium steel with high requirements for phosphorus composition (mass percentage of chromium > 8wt%), especially high-chromium steel with a mass percentage of P ≤ 0.012% cannot be stably produced. When using the "BOF+LF+RH" method to produce stainless steel, if low phosphorus control is required, the BOF furnace needs to tap steel at a low temperature. Since high-chromium low-phosphorus steel and stainless steel production have the same large amount of alloy addition, the requirement for heating the molten steel in the LF furnace is extremely high, the treatment time is long, and three LF furnaces are required to match the production rhythm for long casting campaigns, making the production difficult. That is, the existing smelting methods for producing high-chromium low-phosphorus steel are all limited by the AOD furnace and the LF furnace.

[0022] In view of the above problems, the embodiments of this application provide a method for preparing high-chromium low-phosphorus steel. The preparation method of this application optimizes the function allocation of two converters, splits the complex stainless steel production process into a dephosphorization converter process and a decarburization and chromium-preserving converter process, and organically combines it with the argon station treatment process.

[0023] The preparation method of the high-chromium and low-phosphorus steel provided by the embodiments of the present application will be introduced below.

[0024] According to the present application, a preparation method of a high-chromium and low-phosphorus steel is as Figure 1 shown, including:

[0025] Step S01: Perform dephosphorization treatment on the desulfurized hot metal raw material in a first converter to obtain dephosphorized molten steel, wherein the mass percentage content of phosphorus element in the dephosphorized molten steel ≤ 0.012 wt%.

[0026] Step S02: Perform carbon addition treatment on the dephosphorized molten steel to obtain dephosphorized and carbon-added molten steel, wherein the mass percentage content of carbon element in the dephosphorized and carbon-added molten steel is 1.4 wt% - 2.0 wt%.

[0027] Step S03: Perform silicon addition treatment on the dephosphorized and carbon-added molten steel to obtain silicon-added molten steel, wherein the mass percentage content of silicon element in the silicon-added molten steel is 0.8 wt% - 1.5 wt%.

[0028] Step S04: Perform decarbonization and chromium addition treatment on the silicon-added molten steel in a second converter to obtain high-chromium and low-phosphorus molten steel, wherein the mass percentage content of chromium element in the high-chromium and low-phosphorus molten steel ≥ 8 wt%.

[0029] The inventors found that the preparation method of the high-chromium and low-phosphorus steel of the present application completes dephosphorization in the first converter, adds carbon during the tapping process of the first converter, adds silicon after the carbon addition is completed, and completes decarbonization and chromium addition in the second converter. Optimizing the function allocation of the two converters splits the complex stainless steel production process into a dephosphorization converter process and a decarbonization and chromium-preserving converter process, and through an organic combination with the argon station treatment process, the operation is simple and controllable, and the chromium recovery rate is high.

[0030] In some specific embodiments, the temperature of the desulfurized hot metal raw material is ≥ 1300 °C. For example, the temperature of the desulfurized hot metal raw material can be 1300 °C, 1310 °C, 1320 °C, 1330 °C, 1340 °C, 1350 °C, 1360 °C, 1370 °C, 1380 °C, 1390 °C, 1400 °C, or any combination range of the above values; and / or, the mass percentage content of silicon element in the desulfurized hot metal raw material is 0.20 wt% - 0.60 wt%. For example, the mass percentage content of silicon element in the desulfurized hot metal raw material can be 0.2 wt%, 0.25 wt%, 0.3 wt%, 0.35 wt%, 0.4 wt%, 0.45 wt%, 0.5 wt%, 0.55 wt%, 0.6 wt%, or any combination range of the above values, and the mass percentage content of phosphorus element in the desulfurized hot metal raw material is ≤ 0.09 wt%. For example, the mass percentage content of phosphorus element in the desulfurized hot metal raw material can be 0.09 wt%, 0.085 wt%, 0.08 wt%, 0.075 wt%, 0.07 wt%, 0.06 wt%, or any combination range of the above values; and / or, the mass percentage content of carbon element in the dephosphorized molten steel is ≤ 0.03 wt%. For example, the mass percentage content of carbon element in the dephosphorized molten steel can be 0.03 wt%, 0.025 wt%, 0.02 wt%, 0.015 wt%, 0.01 wt%, 0.005 wt%, or any combination range of the above values; and / or, the temperature of the dephosphorized molten steel before carbon addition treatment is 1650 °C - 1680 °C. For example, it can be 1650 °C, 1655 °C, 1660 °C, 1665 °C, 1670 °C, 1675 °C, 1680 °C, or any combination range of the above values.

[0031] In some specific embodiments, the first converter blows argon at the bottom and oxygen at the top. The gas supply intensity of argon is 0.04 Nm 3 / (min·t) - 0.06 Nm 3 / (min·t). For example, it can be 0.04 Nm 3 / (min·t), 0.045 Nm 3 / (min·t), 0.05 Nm 3 / (min·t), 0.055 Nm 3 / (min·t), 0.06 Nm 3 / (min·t), or any combination range of the above values; the gas supply intensity of oxygen is 3.2 Nm 3 / (min·t) - 3.7 Nm 3 / (min·t). For example, it can be 3.2 Nm 3 / (min·t), 3.25 Nm 3 / (min·t), 3.3 Nm 3 / (min·t), 3.4 Nm 3 / (min·t), 3.5 Nm 3 / (min·t), 3.6 Nm 3 / (min·t), 3.7 Nm 3 / (min·t), or any combination range of the above values; the second converter blows argon at the bottom and oxygen at the top, and the supply intensity of argon is 0.04 Nm 3 / (min·t) ~ 0.06 Nm 3 / (min·t), for example, it can be 0.04 Nm 3 / (min·t), 0.045 Nm 3 / (min·t), 0.05 Nm 3 / (min·t), 0.055 Nm 3 / (min·t), 0.06 Nm 3 / (min·t), or any combination range of the above values; the supply intensity of oxygen is 3.2 Nm 3 / (min·t) ~ 3.7 Nm 3 / (min·t), for example, it can be 3.2 Nm 3 / (min·t), 3.25 Nm 3 / (min·t), 3.3 Nm 3 / (min·t), 3.4 Nm 3 / (min·t), 3.5 Nm 3 / (min·t), 3.6 Nm 3 / (min·t), 3.7 Nm 3 / (min·t), or any combination range of the above values.

[0032] In some specific embodiments, the dephosphorization treatment includes: adding 15 kg / ton of steel to 30 kg / ton of steel of lime to the desulfurized hot metal raw material in batches after the first predetermined time for slag formation, and performing tilting furnace slag pouring after the second predetermined time of slag formation to obtain the molten steel after the first dephosphorization treatment; adding 20 kg / ton of steel to 30 kg / ton of steel of lime to the molten steel after the first dephosphorization treatment, and then performing tilting furnace secondary slag formation to the end point to obtain dephosphorized molten steel, wherein the basicity of the final slag is 3.2 to 3.5. For example, the basicity of the final slag can be 3.2, 3.3, 3.4, 3.5, or any combination range of the above values.

[0033] In some specific embodiments, the first predetermined time is 1 min to 3 min. For example, it can be 1 min, 1.5 min, 2 min, 2.5 min, 3 min, or any combination range of the above values. The second predetermined time is 4 min to 6 min. For example, it can be 4 min, 4.5 min, 5 min, 5.5 min, 6 min, or any combination range of the above values. The amount of slag poured out accounts for 50% to 85% of the total slag amount. For example, it can be 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, or any combination range of the above values.

[0034] In some specific embodiments, the decarbonization and chromium enrichment treatment includes: adding lime and calcined magnesite balls to the silicon-added molten steel to form slag and then heating to a predetermined temperature; adjusting the gas supply intensity to the first oxygen supply intensity and the first argon supply intensity, and then adding ferrosilicon and high-carbon ferrochrome to the molten steel until the content of chromium element in the molten steel reaches the predetermined content; adjusting the gas supply intensity to the second argon intensity and stopping oxygen supply, strongly stirring the molten steel, and adding ferrosilicon to reduce chromium oxides in the slag.

[0035] In some specific embodiments, the first argon supply intensity is 0.09 Nm 3 / (min·t) to 0.15 Nm 3 / (min·t). For example, it can be 0.09 Nm 3 / (min·t), 0.1 Nm 3 / (min·t), 0.11 Nm 3 / (min·t), 0.12 Nm 3 / (min·t), 0.13 Nm 3 / (min·t), 0.14 Nm 3 / (min·t), 0.15 Nm 3 / (min·t), or any combination range of the above values. The first oxygen supply intensity is 1.5 Nm 3 / (min·t) to 2.2 Nm 3 / (min·t). For example, it can be 1.5 Nm 3 / (min·t), 1.6 Nm 3 / (min·t), 1.7 Nm 3 / (min·t), 1.8 Nm 3 / (min·t), 1.9 Nm 3 / (min·t), 2.0 Nm 3 / (min·t), 2.1 Nm 3 / (min·t), 2.2 Nm 3 / (min·t), or any combination range of the above values; the second argon supply intensity is 0.09 Nm 3 / (min·t) to 0.15 Nm 3 / (min·t), for example, it can be 0.09 Nm 3 / (min·t), 0.1 Nm 3 / (min·t), 0.11 Nm 3 / (min·t), 0.12 Nm 3 / (min·t), 0.13 Nm 3 / (min·t), 0.14 Nm 3 / (min·t), 0.15 Nm 3 / (min·t), or any combination range of the above values.

[0036] In some specific embodiments, the predetermined temperature ≥ 1650 °C, for example, it can be 1650 °C, 1655 °C, 1660 °C, 1665 °C, 1670 °C, 1675 °C, 1680 °C, 1690 °C, 1700 °C, or any combination range of the above values; and / or, the addition amount of ferrosilicon is 4.5 kg / ton to 6.0 kg / ton; high-carbon ferrochrome is added in multiple times, each time 1000 kg to 2000 kg, and the interval time between two additions is 3 min to 4 min, for example, it can be 3 min, 3.2 min, 3.5 min, 3.8 min, 4 min; and / or, the predetermined content of chromium element is 80% to 85% of the target content, for example, it can be 80%, 81%, 82%, 83%, 84%, 85%, or any combination range of the above values; and / or, the treatment time of chromium oxide in ferrosilicon reduction slag is 8 min to 10 min, for example, it can be 8 min, 8.5 min, 9 min, 9.5 min, 10 min, or any combination range of the above values.

[0037] In some specific embodiments, temperature measurement and sampling are carried out after the decarburization and chromium enrichment treatment.

[0038] In some specific embodiments, alloy is added for adjustment according to the sampling results to adjust the composition, and tapping is carried out after the composition and temperature meet the requirements.

[0039] In addition, the term " / and" in this text is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A / and B can mean: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this text generally indicates that the associated objects before and after are in an "or" relationship.

[0040] The following embodiments more specifically describe the content disclosed in the present application, and these embodiments are only for illustrative purposes.

[0041] Because various modifications and variations within the scope of the disclosure of the present application will be apparent to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are by mass, and all raw materials used in the embodiments are commercially available or prepared by conventional methods and can be used directly without further treatment, and the instruments used in the embodiments are all commercially available.

[0042] The percentages involved in this specific embodiment are all mass percentages.

[0043] Example 1

[0044] In this embodiment, the target steel grade is GC4011A3, and its composition by mass percentage includes: C: 0.07 wt% - 0.13 wt%, Si: 0.30 wt% - 0.50 wt%, Mn: 0.40 wt% - 0.50 wt%, P: ≤0.010 wt%, S: ≤0.010 wt%, Cr: 8.5 wt% - 9.5 wt%, and the balance is iron and other inevitable trace elements. It is prepared by the following method:

[0045] Add the desulfurized molten steel into a 100-ton top-bottom combined blowing converter. The bottom blowing gas supply intensity is 0.04 Nm 3 / (min·t), and the top blowing oxygen supply intensity is 3.2 Nm 3 / (min·t). Add 23 kg of lime per ton of steel within 1 min - 3 min after the start of blowing. The lime is added in two batches. Pour out the pre-stage slag after 4.8 min of blowing. The amount of slag poured out is 65% of the total slag amount. Shake the converter for secondary slag making and blow to the end point. The lime addition amount is 28 kg per ton of steel, and the basicity of the final slag is 3.3 to obtain the dephosphorized molten steel. The mass percentage of phosphorus element in the dephosphorized molten steel is 0.0068 wt%, and the mass percentage of carbon element is 0.0283 wt%.

[0046] The tapping temperature of the dephosphorized molten steel is 1668 °C. Add 6.2 kg / t of ferroaluminum for deoxidation during the tapping process and use 95 carbon powder for carbon increase to obtain the dephosphorized and carbon-increased molten steel. The mass percentage of carbon element in the dephosphorized and carbon-increased molten steel is 1.5803 wt%.

[0047] Adopt the argon station process to add ferrosilicon to the dephosphorized and carbon-increased molten steel to increase silicon, and obtain the silicon-increased molten steel. The mass percentage of silicon element in the silicon-increased molten steel is 1.2504 wt%.

[0048] Add the silicon-increased molten steel into a 100-ton top-bottom combined blowing converter. The bottom blowing argon intensity is 0.04 Nm 3 / (min·t), and the top blowing oxygen supply intensity is 3.2 Nm3 Smelting at (min.t), adding lime and lightly burned magnesia balls to form slag, then raising the temperature to 1654 °C, and adjusting the bottom blowing gas supply intensity to 0.1 Nm 3 / (min.t), and adjusting the top blowing oxygen supply intensity to 1.7 Nm 3 / (min.t). At the same time, add 4.8 kg of ferrosilicon per ton of steel to the furnace to protect chromium, and batch add high-carbon ferrochrome to the furnace from the high-level bunker. The addition amount each time is 1800 kg, and the interval time is 3 min - 4 min. When the mass percentage content of chromium element in the molten steel reaches 7.303 wt%, raise the lance to stop blowing oxygen; adjust the bottom blowing gas supply intensity to 0.21 Nm 3 / (min.t) and carry out strong stirring, add ferrosilicon to reduce chromium oxides in the slag, and the treatment time is 8.3 min. During this process, add ferromanganese to adjust manganese. Tap the molten steel at a temperature of 1659 °C. Sampling analysis shows that by mass percentage: C: 0.0853 wt%, Si: 0.3543 wt%, Mn: 0.4358 wt%, P: 0.0082 wt%, S: 0.0072 wt%, Cr: 8.8354 wt%, and the balance is iron and other inevitable trace elements.

[0049] In this example, the chromium recovery rate of alloying chromium in the high-chromium and low-phosphorus molten steel is 95.03%, which is equivalent to the AOD method. The mass percentage content of phosphorus element in the high-chromium and low-phosphorus molten steel is 0.0082 wt%, meeting the requirements of the steel grade.

[0050] Example 2

[0051] In this example, the target steel is AC4011A6, and its composition by mass percentage includes: C: 0.013 wt% - 0.20 wt%, Si: 0.35 wt% - 0.48 wt%, Mn: 0.28 wt% - 0.52 wt%, P: ≤0.012 wt%, S: ≤0.010 wt%, Cr: 13.2 wt% - 14 wt%, and the balance is iron and other inevitable trace elements.

[0052] Add the desulfurized molten steel into a 100-ton top-bottom combined blowing converter, with the bottom blowing gas supply intensity of 0.04 Nm 3 / (min.t), and the top blowing oxygen supply intensity of 3.2 Nm 3 / (min.t). Add 25 kg of lime per ton of steel within 1 min - 3 min after starting blowing, adding in two batches. Pour the pre-stage slag after blowing for 5.6 min, and the poured slag amount is 80% of the total slag amount. Shake the furnace to re-form slag and blow to the end point. The lime addition amount is 28 kg per ton of steel, and the basicity of the final slag is 3.3 to obtain dephosphorized molten steel. The mass percentage content of phosphorus element in the dephosphorized molten steel is 0.0072 wt%, and the mass percentage content of carbon element is 0.0216 wt%.

[0053] The tapping temperature of the dephosphorized molten steel is 1655°C. During tapping, 6.8 kg / t of ferro-aluminum is added for deoxidation, and 95 carbon powder is used for carbon increase, obtaining dephosphorized and carbon-increased molten steel. The mass percentage content of carbon element in the dephosphorized and carbon-increased molten steel is 1.6303 wt%.

[0054] Ferrosilicon is added to the dephosphorized and carbon-increased molten steel by the argon station process to increase silicon, obtaining silicon-increased molten steel. The mass percentage content of silicon element in the silicon-increased molten steel is 1.3208 wt%.

[0055] The silicon-increased molten steel is added into a 100-ton top-bottom combined blowing converter. The bottom blowing argon intensity is 0.04 Nm 3 / (min·t), and the top blowing oxygen supply intensity is 3.2 Nm 3 / (min·t) for smelting. Lime and lightly burned magnesia balls are added to make slag, and then the temperature is raised to 1661°C. The bottom blowing gas supply intensity is adjusted to 0.12 Nm 3 / (min·t), and the top blowing gas supply intensity is adjusted to 1.8 Nm 3 / (min·t). At the same time, 4.5 kg of ferrosilicon per ton of steel is added to the furnace, and high-carbon ferrochrome is added to the furnace in batches from the high-position bin. The addition amount each time is 1600 kg, and the interval time is 3 min - 4 min. When the mass percentage content of Cr in the molten steel reaches 10.8226 wt%, the oxygen lance is lifted to stop blowing oxygen, and the bottom blowing gas supply intensity is adjusted to 0.20 Nm 3 / (min·t) for strong stirring, and ferrosilicon is added to reduce chromium oxides in the slag. The treatment time is 9.8 min. The molten steel is tapped at a temperature of 1653°C. Sampling analysis shows that by mass percentage: C: 0.1528 wt%, Si: 0.3552 wt%, Mn: 0.4027 wt%, P: 0.0078 wt%, S: 0.0053 wt%, Cr: 13.5278 wt%, and the balance is iron and other inevitable trace elements.

[0056] In this embodiment, the chromium recovery rate of the high-chromium and low-phosphorus molten steel alloying is 95.67%, which is equivalent to the AOD method. The mass percentage content of phosphorus element in the high-chromium and low-phosphorus molten steel is 0.0078 wt%, meeting the requirements of the steel grade.

[0057] As described above, it is only the specific implementation manner of this application, but the protection scope of this application is not limited thereto. Any person skilled in the art within the technical scope disclosed in this application can easily think of various equivalent modifications or substitutions, and these modifications or substitutions should all be covered within the protection scope of this application. Therefore, the protection scope of this application should be subject to the protection scope of the claims.

Claims

1. A method for preparing high chromium and low phosphorus steel, characterized in that: include: Dephosphorizing the desulfurized molten iron raw material in a first converter to obtain dephosphorized molten steel, wherein the mass percentage of phosphorus in the dephosphorized molten steel is ≤0.012wt%; Carburizing the dephosphorized molten steel to obtain dephosphorized and carburized molten steel, wherein the mass percentage of carbon in the dephosphorized and carburized molten steel is 1.4wt% to 2.0wt%; Performing silicon-enhanced treatment on the dephosphorized and carbon-enhanced molten steel to obtain silicon-enhanced molten steel, wherein the mass percentage of silicon in the silicon-enhanced molten steel is 0.8wt% to 1.5wt%; The silicon-enriched molten steel is subjected to a decarburization and chromium-enrichment treatment in a second converter to obtain high-chromium and low-phosphorus molten steel, wherein the mass percentage of chromium in the high-chromium and low-phosphorus molten steel is ≥8wt%.

2. The method for preparing high chromium and low phosphorus steel according to claim 1, characterized in that: The temperature of the desulfurized molten iron raw material is ≥1300°C; And / or, the mass percentage of silicon in the desulfurized molten iron raw material is 0.20wt% to 0.60wt%, and the mass percentage of phosphorus is ≤0.09wt%; And / or, the mass percentage of carbon element in the dephosphorized molten steel is ≤0.03wt%; And / or, the temperature of the dephosphorized molten steel before the carburization treatment is 1650°C to 1680°C.

3. The preparation method according to claim 1, characterized in that: The first converter is bottom-blown with argon and top-blown with oxygen. The argon supply intensity is 0.04Nm 3 / (min·t)~0.06Nm 3 / (min·t), oxygen supply intensity is 3.2Nm 3 / (min·t)~3.7Nm 3 / (min·t); The second converter is bottom-blown with argon and top-blown with oxygen. The argon supply intensity is 0.04Nm 3 / (min·t)~0.06Nm 3 / (min·t), oxygen supply intensity is 3.2Nm 3 / (min·t)~3.7Nm 3 / (min·t).

4. The preparation method according to claim 1, characterized in that: The dephosphorization treatment comprises: After the first predetermined time, 15kg / ton steel to 30kg / ton steel of lime is added to the desulfurized molten iron raw material in batches to make slag, and after the second predetermined time of slag making, the furnace is shaken and the slag is poured to obtain the molten steel for the first dephosphorization treatment; 20kg / ton steel to 30kg / ton steel of lime is added to the molten steel after the first dephosphorization treatment, and then the furnace is shaken for secondary slag making to the end point to obtain dephosphorized molten steel, wherein the basicity of the final slag is 3.2-3.

5.

5. The preparation method according to claim 4, characterized in that: The first predetermined time is 1 min to 3 min, the second predetermined time is 4 min to 6 min, and the amount of slag poured out accounts for 50% to 85% of the total slag amount.

6. The preparation method according to claim 1, characterized in that: The decarburization and chromium-increasing treatment comprises: Adding lime and light-burned magnesium balls into silicon-enriched molten steel to form slag and then heating it to a predetermined temperature; After adjusting the gas supply intensity to a first oxygen gas supply intensity and a first argon gas supply intensity, ferrosilicon and high carbon ferrochrome are added into the molten steel until the content of chromium in the molten steel reaches a predetermined content; The gas supply intensity is adjusted to the second argon intensity and the oxygen supply is stopped, the molten steel is stirred, and ferrosilicon is added to reduce the chromium oxide in the slag.

7. The preparation method according to claim 6, characterized in that: The first argon gas supply intensity is 0.09Nm 3 / (min·t)~0.15Nm 3 / (min·t), the first oxygen supply intensity is 1.5Nm 3 / (min·t)~2.2Nm 3 / (min·t); The second argon gas supply intensity is 0.09Nm 3 / (min·t)~0.15Nm 3 / (min·t).

8. The preparation method according to claim 6, characterized in that: The predetermined temperature is ≥ 1650°C; And / or, the amount of ferrosilicon added is 4.5kg / ton to 6.0kg / ton; high carbon ferrochrome is added in multiple times, 1000kg to 2000kg each time, and the interval between each two additions is 3min to 4min; and / or, the predetermined content of chromium is 80% to 85% of the target content; And / or, the treatment time of chromium oxide in ferrosilicon reduction slag is 8 minutes to 10 minutes.

9. The preparation method according to claim 1, characterized in that: Temperature measurement and sampling are performed after the decarburization and chromium addition treatment.

10. The preparation method according to claim 9, characterized in that: According to the sampling results, additional alloy is added to adjust the composition, and the steel is produced after the composition and temperature meet the requirements.

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