Method for producing an alloyed strand, alloyed strand and steel product

Abstract

The application discloses a preparation method of an alloy casting blank, the alloy casting blank and a steel product. The method comprises the following steps: carrying out converter smelting on molten steel to obtain converter molten steel; tapping the converter molten steel and transferring the converter molten steel to a ladle; performing bottom argon blowing on the ladle during tapping, and the argon flow is 10-40 Nm3 / h; measuring the temperature of the molten steel in the ladle, calculating the alloy adding amount and adding batch according to the temperature measurement result and the target composition of the alloy casting blank, so as to control the temperature of the molten steel after adding the alloy, wherein the temperature of the molten steel is greater than or equal to the liquidus temperature of the target composition of the alloy casting blank plus 10 DEG C; adding the alloy into the molten steel in the ladle according to the alloy adding amount and the adding batch; and performing LF refining and continuous casting on the molten steel in the ladle to obtain the alloy casting blank.

Description

Technical Field

[0001] This application belongs to the field of steel plate smelting technology, specifically relating to a method for preparing alloy castings, alloy castings, and steel products. Background Technology

[0002] To significantly improve the overall properties of steel, such as strength, toughness, high-temperature resistance, and corrosion resistance, alloys such as ferromolybdenum and ferrotungsten are typically added to the converter in traditional processes.

[0003] Ferromolybdenum has a high melting point, while the tapping temperature of the converter generally does not exceed 1640℃ and the smelting cycle is short, making it difficult for ferromolybdenum to melt completely. Unmelted ferromolybdenum is poured into the slag pot with the slag, resulting in the loss of valuable alloy.

[0004] In addition, ferromolybdenum is relatively expensive. It also presents challenges such as susceptibility to theft, material loss during the feeding process, strict dimensional requirements, and high processing costs.

[0005] Therefore, how to prepare alloy castings and improve the yield of such alloys to reduce costs has become a key research direction. Summary of the Invention

[0006] In view of this, this application provides a method for preparing an alloy billet, an alloy billet, and a steel product. This method improves the yield of ferromolybdenum, reduces the loss of precious alloys, shortens the smelting cycle, and reduces production costs. It also reduces the inclusion content in the alloy billet, further improving the overall performance of the alloy billet.

[0007] In a first aspect, embodiments of this application provide a method for preparing an alloy casting, comprising: Molten steel is smelted in a converter to produce converter steel. The molten steel from the converter is tapped and transferred to a ladle; during the tapping process, argon gas is blown into the ladle from the bottom at a flow rate of 10-40 Nm³ / h. The temperature of the molten steel in the ladle is measured. Based on the temperature measurement results and the target composition of the alloy billet, the amount and batch of alloy to be added are calculated in order to control the temperature of the molten steel after the alloy is added. The temperature of the molten steel is controlled to be ≥ (liquidity temperature of the target composition of the alloy billet + 10℃). The alloy is added to the molten steel in the ladle according to the amount and batch of alloy added. The molten steel in the ladle is refined by LF and continuously cast to obtain an alloy billet.

[0008] In some embodiments, the alloy includes one or more of ferromolybdenum and ferrotungsten.

[0009] In some embodiments, the alloy billet comprises, by mass percentage: C: 0.08%-0.12%, Si: 0.25%-0.35%, Mn: 0.4%-0.5%, P: ≤0.017%, S: ≤0.005%, Alt<0.02%, Cr: 8.6%-9.0%, W: 1.60%-1.80%, Mo: 0.35%-0.45%, V: 0.16%-0.24%, Nb: 0.05%-0.08%, Ni: 0.1%-0.3%, B: 0.002%-0.004%, N: 0.01%-0.065%, with the balance being iron and unavoidable impurities.

[0010] In some embodiments, after measuring the temperature of the molten steel in the ladle, the argon flow rate is reduced to 10-30 Nm³. 3 / h.

[0011] In some embodiments, after adding an alloy to the molten steel in the ladle according to the amount and batch of alloy added, the method further includes: increasing the argon flow rate to 41-100 Nm³. 3 / h; Argon blowing from the bottom of the ladle is used to stir the molten steel in the ladle, and the stirring time is ≥3 minutes.

[0012] In some embodiments, before tapping the molten steel from the converter, the method includes: bypassing argon blowing during the converter smelting process.

[0013] In some embodiments, the liquidus temperature of the target composition of the alloy billet is 1512°C. The temperature of the molten steel in the ladle is measured, and based on the temperature measurement results and the target composition of the alloy billet, the amount and batch of alloy added are calculated to control the temperature of the molten steel after alloy addition. Controlling the molten steel temperature to be ≥ (liquidus temperature of the target composition of the alloy billet + 10°C) includes: the temperature measurement result 1534°C ≤ t1 ≤ 1640°C, the molybdenum content in the target composition of the alloy billet is 0.35%-0.45%, and the amount of molybdenum alloy added is 5.85~7.53 kg; the temperature measurement result t2 is 1571°C < t2 ≤ 1700°C, the tungsten content in the target composition of the alloy billet is 1.6%-1.8%, and the amount of tungsten alloy added is 23.23~26.14 kg per ton of molten steel.

[0014] In some embodiments, adding an alloy to molten steel in a ladle includes: moving the ladle of molten steel from the temperature measurement position of the argon station to the fire baffle position under the furnace, and using a forklift to accurately add the bagged alloy into the ladle so that the alloy is evenly distributed on the surface of the molten steel.

[0015] Secondly, embodiments of this application provide a method for preparing a continuously cast billet, including the method of the first aspect.

[0016] Thirdly, embodiments of this application provide a steel product, which is made from a continuously cast billet obtained by the method of the first aspect or a continuously cast billet obtained by the preparation method of the second aspect.

[0017] This application has at least the following beneficial effects: The method provided in this application controls the argon flow rate during converter smelting and tapping, the temperature measurement of molten steel before adding alloys, the argon blowing conditions, and the temperature of molten steel after adding alloys. This effectively solves the problems of low yield and difficulty in melting alloys due to their high melting point in traditional processes, avoids losses during storage and charging, significantly improves the overall yield of alloys, reduces production costs, and accelerates the smelting pace. It also reduces the inclusion content in alloy billets, further improving the overall performance of alloy billets. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the implementation regulations of this application, the drawings used in the embodiments of this application will be briefly introduced below. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A schematic flowchart of the preparation method of the alloy casting billet according to an embodiment of this application is shown. Detailed Implementation

[0020] To make the objectives, technical solutions, and beneficial technical effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the implementation details described in this specification are merely for illustrative purposes and are not intended to limit the scope of this application.

[0021] For simplicity, this application only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form a range not explicitly stated; and any lower limit can be combined with other lower limits to form a range not explicitly stated, just as any upper limit can be combined with any other upper limit to form a range not explicitly stated. Furthermore, although not explicitly stated, every point or individual value between the endpoints of the range is included within that range. Therefore, each point or individual value can be used as its own lower or upper limit and combined with any other point or individual value or with other lower or upper limits to form a range not explicitly stated.

[0022] In the description of this application, it should be noted that, unless otherwise stated, "above" and "below" include the stated number, and "multiple" in "one or more" means two or more.

[0023] The foregoing description of this application is not intended to describe every disclosed implementation or method. Instead, the following description provides more specific examples of exemplary embodiments. Throughout the application, guidance is provided through a series of embodiments, which can be used in various combinations. The examples listed are representative only and should not be construed as exhaustive.

[0024] As described in the background section, molybdenum and tungsten, as alloying components of steel, can give steel a uniform microcrystalline structure, lower the eutectoid decomposition temperature, expand the heat treatment temperature range, and increase the hardening depth. They can also improve the hardness, toughness, creep resistance, and corrosion resistance of steel. For example, ferromolybdenum is commonly used as an additive in the steel industry, but it is relatively expensive, with 60Mo costing 254,000 yuan / ton. With the significant drop in steel market prices, increasing the yield of molybdenum and tungsten to reduce costs during the smelting of high-grade steels has become crucial.

[0025] Current technological status: Ferrotungsten has a very high melting point, and when added to the converter, the yield is only 10%. Ferromolybdenum has a relatively high melting point. In the smelting process of Mo-containing steel, ferromolybdenum is added to the converter along with scrap steel in the scrap hopper. Ferromolybdenum is easily covered by slag and is not easy to melt, resulting in a relatively low Mo yield, which greatly increases the smelting cost. Furthermore, there is no specific method to improve the Mo yield during the smelting process.

[0026] Therefore, by measuring the temperature of the molten steel in the ladle and calculating the amount and batch of alloy to be added based on the temperature measurement results and the target composition of the alloy billet, the temperature of the molten steel after alloy addition is controlled. Adding alloy to the molten steel in the ladle according to the amount and batch increases the yield of ferromolybdenum and shortens the smelting cycle; it also reduces the inclusion content in the alloy billet, ensuring the cleanliness of the molten steel and product quality.

[0027] Figure 1 A schematic flowchart of the preparation method of the alloy billet according to an embodiment of this application is shown.

[0028] like Figure 1 As shown, the preparation method includes: S1 to S5.

[0029] S1. Molten steel is smelted in a converter to obtain converter steel.

[0030] In this step, a normal turnover package is used, and a steel ladle with a bottom is not used. Argon is blown through the bypass before steel is tapped to ensure that the bottom brick of the steel ladle has excellent air permeability before steel tapping.

[0031] S2. Tap the molten steel from the converter and transfer it to the ladle; during the tapping process, the ladle is bottom-blown with argon gas at a flow rate of 10-40 Nm³ / h.

[0032] Optionally, the argon flow rate can be any value or a range of combinations thereof from 10 Nm³ / h, 15 Nm³ / h, 20 Nm³ / h, 25 Nm³ / h, 30 Nm³ / h, 35 Nm³ / h, and 40 Nm³ / h.

[0033] Furthermore, during the tapping process, argon gas is blown into the ladle at a distance of 2 / 3 radius from the bottom center. Additionally, argon gas is blown into the ladle at a distance of 2 / 3 radius from the bottom center, specifically at the location of at least two permeable bricks. This facilitates the mixing of the bacterial solution with the molten steel, further improving temperature uniformity and alloy yield.

[0034] In this step, during the tapping process, the argon flow rate is controlled within the range of 10-40 Nm³ / h. Bottom blowing of argon is performed during the converter tapping process to control the argon flow rate, reduce the temperature drop of the molten steel, and ensure normal argon blowing through the ladle permeable bricks. By blowing argon at a low flow rate, it is possible to prevent blockage of the ladle permeable bricks and effectively reduce the temperature drop of the molten steel, ensuring a smooth and stable tapping process and creating favorable conditions for subsequent alloy addition.

[0035] S3. Measure the temperature of the molten steel in the ladle. Based on the temperature measurement results and the target composition of the alloy billet, calculate the amount and batch of alloy to be added in order to control the temperature of the molten steel after adding the alloy. The temperature of the molten steel should be controlled to be ≥ (liquidity temperature of the target composition of the alloy billet + 10℃).

[0036] In this step, the converter temperature generally needs to be increased to melt the ferromolybdenum inside the converter. According to the embodiment of this application, the ferromolybdenum is added to the ladle without increasing the temperature, thus reducing the tapping temperature by about 40°C, which is beneficial for converter dephosphorization and furnace lining maintenance.

[0037] S4. Add alloy to the molten steel in the ladle according to the amount and batch of alloy added.

[0038] In this step, it is important to properly control the argon blowing before and during the addition of ferromolybdenum to avoid production accidents caused by poor argon blowing in the ladle and molten steel splashing outside the ladle after the addition of ferromolybdenum.

[0039] Adding ferromolybdenum after steel tapping avoids the problem of ferromolybdenum not melting due to low furnace temperature, and also prevents poor argon blowing caused by adding ferromolybdenum to the ladle prematurely. Furthermore, compared to adding ferromolybdenum from a silo, it avoids theft, special size requirements, and losses during the feeding process.

[0040] S5. The molten steel in the ladle is refined by LF and continuously cast to obtain an alloy billet.

[0041] According to the embodiments of this application, by adding alloys using the method of this application, the overall yield of ferromolybdenum alloy is increased from 92.0% to 97.1%, and the overall yield of ferrotungsten alloy is increased from 10% to 97.0%, significantly reducing the loss of precious alloys and accelerating the smelting pace. The converter no longer needs to wait for scrap steel to fall onto the platform to add ferromolybdenum, avoiding the time spent waiting for scrap steel in the converter, thereby shortening the smelting cycle and improving production efficiency; the alloys do not require special processing, reducing additional processing costs; at the same time, it avoids the loss of alloys during storage and charging, further reducing production costs.

[0042] Furthermore, the method of this application reduces the inclusion content in the alloy casting, thereby further improving the overall performance of the alloy casting.

[0043] In some embodiments, before S2, before tapping the molten steel from the converter, the method includes: bypassing argon blowing during the converter smelting process.

[0044] Bypass argon blowing is used before tapping molten steel from the converter. The ladle's permeable bricks have good permeability. Under these conditions, alloys such as ferromolybdenum are added, which can be applied to low-phosphorus steel. Steel can be tapped directly or killed for 1-6 minutes before tapping.

[0045] "Bypass argon blowing" can be understood as an argon blowing operation using a backup gas supply pipeline to ensure that high-quality molten steel is continuously and gently stirred from refining to casting. Bypass argon blowing achieves "uninterrupted large-scale argon stirring," guaranteeing that the molten steel can be gently stirred throughout the entire process from the end of refining to the solidification of the steel during casting. This creates optimal conditions for the flotation of inclusions and is a key guarantee for the production of high-quality steel.

[0046] In some embodiments, S2, the liquidus temperature of the target composition of the alloy billet is 1512°C; the temperature of the molten steel in the ladle is measured, and based on the temperature measurement results and the target composition of the alloy billet, the amount and batch of alloy added are calculated to control the temperature of the molten steel after alloy addition, wherein controlling the molten steel temperature ≥ (liquidus temperature of the target composition of the alloy billet + 10°C) includes: The temperature measurement result is 1534℃≤t1≤1640℃, the target composition of the alloy billet has a molybdenum content of 0.35%-0.45%, and the amount of molybdenum alloy added is 5.85~7.53kg; The temperature measurement result t2 is 1571℃<t2≤1700℃, the tungsten content in the target composition of the alloy billet is 1.6%-1.8%, and the amount of tungsten alloy added is 23.23~26.14kg per ton of molten steel.

[0047] This is beneficial to the dephosphorization efficiency of the converter, improving the efficiency of the smelting process and reducing costs.

[0048] For example, if the tapping temperature is 1580℃, the tapping argon station temperature is 1550℃, and the liquidus temperature of the steel is 1510℃, adding 10℃ gives 1520℃, leaving a 30℃ margin. One ton of ferromolybdenum absorbs heat, causing a temperature drop of about 8℃. Adding 2 tons causes a total temperature drop of 16℃, leaving 14℃ remaining. Other alloys can be added at a rate of 1.75 tons.

[0049] In some embodiments, S3, after adding an alloy to the molten steel in the ladle according to the amount and batch of alloy added, the method further includes: increasing the argon flow rate, wherein the argon flow rate at this stage is 41-100 Nm. 3 / h; optionally, the argon flow rate can be any value or a range of combinations thereof from 41 Nm³ / h, 45 Nm³ / h, 50 Nm³ / h, 55 Nm³ / h, 60 Nm³ / h, 65 Nm³ / h, 70 Nm³ / h, 75 Nm³ / h, 80 Nm³ / h, 85 Nm³ / h, 90 Nm³ / h, 95 Nm³ / h, 100 Nm³ / h.

[0050] Argon blowing from the bottom of the ladle is used to stir the molten steel in the ladle, and the stirring time is ≥3 minutes.

[0051] Argon stirring promotes rapid melting of ferromolybdenum and ensures good permeability of the ladle after the addition of ferromolybdenum, thus preventing the permeable bricks from becoming clogged during the LF (refining furnace) process.

[0052] Stirring time and argon flow rate within the above range promote the melting of alloys such as ferromolybdenum and improve the yield of elements in ferromolybdenum and other alloys.

[0053] In some embodiments, after S3, after measuring the temperature of the molten steel in the ladle, the argon flow rate is reduced to 10-30 Nm³. 3 / h. Optionally, the argon flow rate can be any value or a range of combinations thereof from 10 Nm³ / h, 11 Nm³ / h, 12 Nm³ / h, 13 Nm³ / h, 14 Nm³ / h, 15 Nm³ / h, 20 Nm³ / h, 25 Nm³ / h, 26 Nm³ / h, 27 Nm³ / h, 28 Nm³ / h, 29 Nm³ / h, and 30 Nm³ / h.

[0054] Appropriately reducing the argon flow rate can prevent the venting bricks in the ladle from becoming clogged, while also avoiding excessive exposure of molten steel and the risk of molten steel splashing out of the ladle when adding ferromolybdenum later, thus ensuring production safety.

[0055] In some embodiments, S4, adding an alloy to the molten steel in the ladle includes: moving the ladle of molten steel from the temperature measurement position of the argon station to the fire baffle position under the furnace, and using a forklift to accurately add the bagged alloy into the ladle so that the alloy is evenly distributed on the surface of the molten steel.

[0056] According to the embodiments of this application, the addition method is simpler, using bagged addition, with the forklift forking the top of the bag, eliminating the need for wooden frame packaging, saving materials, and the distance between the ferromolybdenum and the ladle is shorter, resulting in less impact kinetic energy and preventing large splashes of molten steel, and there are no requirements for the clearance of the ladle.

[0057] In some embodiments, S3 or S4, the alloy includes one or more of ferromolybdenum and ferrotungsten. In ferromolybdenum, the mass content of molybdenum is ≥60%; in ferrotungsten, the mass content of tungsten is 70%~75%.

[0058] In some embodiments, S5, the alloy billet comprises, by mass percentage: C: 0.15%-0.18%, Si: 0.10%-0.30%, Mn: 1.1%-1.3%, P≤0.010%, Mo: 0.58%-0.68%, V: 0.03%-0.05%, Als: 0.04%-0.08%.

[0059] In some embodiments, the alloy billet comprises, by mass percentage: C: 0.08%-0.12%, Si: 0.25%-0.35%, Mn: 0.4%-0.5%, P: ≤0.017%, S: ≤0.005%, Alt<0.02%, Cr: 8.6%-9.0%, W: 1.60%-1.80%, Mo: 0.35%-0.45%, V: 0.16%-0.24%, Nb: 0.05%-0.08%, Ni: 0.1%-0.3%, B: 0.002%-0.004%, N: 0.01%-0.065%, with the balance being iron and unavoidable impurities.

[0060] The alloy billet can be an LG1100QT billet. The performance of this alloy billet is normal, with a yield strength of 1100~1201MPa and a tensile strength of 1200~1400MPa.

[0061] Secondly, embodiments of this application provide a method for preparing a continuously cast billet, including the method of the first aspect.

[0062] Thirdly, embodiments of this application provide a steel product, which is made from a continuously cast billet obtained by the method of the first aspect or a continuously cast billet obtained by the preparation method of the second aspect.

[0063] Example The following embodiments describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on weight, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0064] Example 1 This application provides a method for preparing an alloy casting billet, including: Molten steel is smelted in a converter to produce converter steel, and argon is blown through the converter during the smelting process. The molten steel from the converter is tapped and transferred to a ladle; during the tapping process, argon gas is blown into the ladle from the bottom at a flow rate of 40 Nm³ / h. The temperature of the molten steel in the ladle is measured. Based on the temperature measurement results and the target composition of the alloy billet, the amount and batch of ferromolybdenum to be added are calculated to control the temperature of the molten steel after the addition of ferromolybdenum. Specifically, the temperature of the molten steel is controlled to be ≥1527°C (the liquidus temperature of the target composition of the alloy billet +10°C). After measuring the temperature of the molten steel in the ladle, the argon flow rate is reduced to 20 Nm³. 3 / h.

[0065] Ferromolybdenum is added to the molten steel in the ladle according to the amount and batch number of alloy added. When adding the alloy, the molten steel is brought to the position of the furnace bottom baffle, and a forklift is used to accurately add the bagged alloy into the ladle to ensure even distribution of the alloy on the surface of the molten steel. After adding the alloy, the argon gas flow rate is increased to 60 Nm³. 3 / h; The molten steel in the ladle is stirred by bottom blowing argon gas for 5 minutes. Specifically, the two permeable bricks are located at a radius of 2 / 3 away from the bottom center to blow argon gas into the ladle.

[0066] The molten steel in the ladle is refined by LF refining and continuous casting to obtain an alloy billet. The alloy billet, by mass percentage, comprises: C: 0.08%-0.12%, Si: 0.25%-0.35%, Mn: 0.4%-0.5%, P: ≤0.017%, S: ≤0.005%, Alt<0.02%, Cr: 8.6%-9.0%, W: 1.60%-1.80%, Mo: 0.35%-0.45%, V: 0.16%-0.24%, Nb: 0.05%-0.08%, Ni: 0.1%-0.3%, B: 0.002%-0.004%, N: 0.01%-0.065%, with the balance being iron and unavoidable impurities. Specifically, the target composition of the alloy billet is 0.365% molybdenum and 1.63% tungsten.

[0067] The target liquidus temperature of the alloy billet is 1512℃. The temperature of the molten steel in the ladle is measured. Based on the measurement results and the target composition of the alloy billet, the amount and batch of alloy to be added are calculated to control the temperature of the molten steel after alloy addition. Specifically, controlling the molten steel temperature to ≥1527℃ (the target liquidus temperature of the alloy billet + 10℃) includes: The temperature measurement result was 1601℃, the amount of ferromolybdenum alloy added was 6.27 kg per ton of molten steel, and the amount of ferrotungsten alloy added was 23.33 kg per ton of molten steel.

[0068] Example 2 The difference between this embodiment and Embodiment 1 is that: The temperature measurement result was 1598℃, the amount of ferromolybdenum alloy added was 6.27 kg per ton of molten steel, and the amount of ferrotungsten alloy added was 23.33 kg per ton of molten steel.

[0069] Example 3 The difference between this embodiment and Embodiment 1 is that: The target liquidus temperature of the alloy billet is 1512℃. The target composition of the alloy billet contains 0.45% molybdenum and 1.70% tungsten. The measured temperature is 1590℃. The amount of ferromolybdenum alloy added is 7.75 kg per ton of molten steel, and the amount of ferrotungsten alloy added is 24.34 kg per ton of molten steel.

[0070] Example 4 The difference between this embodiment and Embodiment 1 is that: when bottom blowing argon, two permeable bricks are positioned at the center of the bottom of the ladle to perform bottom blowing argon on the ladle.

[0071] Comparative Example 1 The difference between this comparative example and Example 1 is that the liquidus temperature of the target composition of the alloy billet is 1512℃; the temperature measured by the argon station is 1570℃; the molybdenum content in the target composition of the alloy billet is 0.365%, the tungsten content is 1.63%, the amount of ferromolybdenum alloy added is 6.27 kg per ton of molten steel, and the amount of ferrotungsten alloy added is 23.33 kg per ton of molten steel. After the alloy is added, the argon flow rate is 8 Nm³ / h. The argon flow rate is relatively low, the alloy freezes at the bottom of the ladle, most of the alloy does not melt, and the alloy yield is low.

[0072] Comparative Example 2 The difference between this comparative example and Example 1 is that the liquidus temperature of the target composition of the alloy billet is 1512℃; the temperature measured by the argon station is 1572℃; the target composition of the alloy billet contains 0.365% molybdenum and 1.63% tungsten; the amount of ferromolybdenum alloy added is 6.27 kg per ton of molten steel; the amount of ferrotungsten alloy added is 23.33 kg per ton of molten steel; after adding the alloy, the argon flow rate is 42 Nm³ / h, and the stirring is stopped after 1 min. Due to the short subsequent argon blowing time and poor argon permeability of the ladle, the alloy is frozen at the bottom of the ladle, most of the alloy is not melted, and the alloy yield is low.

[0073] Test section The continuously cast billets prepared by the methods in the examples and comparative examples were tested.

[0074] 1. The chemical composition of the continuously cast billets obtained in the examples and comparative examples was tested according to the method of GB / T20066-2006. Yield = Mass of alloying element in the billet / Amount of alloying element added.

[0075] 2. Detection of the quantity density of inclusions in continuously cast billets: in accordance with GB / T 40304-2021 "Determination of non-metallic inclusion content in steel - full cross section method of steel billet".

[0076] 3. Detection of the types and sizes of inclusions in steel: The detection shall be carried out in accordance with the method of GB / T 10561—2005 "Determination of non-metallic impurities in steel - Microscopic examination method of standard rating chart".

[0077] Table 1 shows the test results of the continuously cast billets in the examples and comparative examples.

[0078] The performance parameters measured above are taken as average values.

[0079] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any skillful means or substitutions should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for preparing an alloy casting billet, characterized in that, include: Molten steel is smelted in a converter to produce converter steel. The molten steel from the converter is tapped and transferred to a ladle; wherein, during the tapping process, bottom-blowing argon gas is applied to the ladle at a flow rate of 10-40 Nm³. 3 / h; The temperature of the molten steel in the ladle is measured. Based on the temperature measurement results and the target composition of the alloy billet, the amount and batch of alloy to be added are calculated in order to control the temperature of the molten steel after the alloy is added. The temperature of the molten steel is controlled to be ≥ (liquidity temperature of the target composition of the alloy billet + 10°C). The alloy is added to the molten steel in the ladle according to the amount of alloy added and the batch number added. The molten steel in the ladle is refined by LF refining and continuous casting to obtain an alloy billet. After measuring the temperature of the molten steel in the ladle, the argon gas flow rate is reduced to 10-30 Nm³. 3 / h, After adding the alloy to the molten steel in the ladle according to the amount and batch number of the alloy added, the method further includes: increasing the argon flow rate to 41-100 Nm³. 3 / h; Argon blowing from the bottom of the ladle is used to stir the molten steel in the ladle, and the stirring time is ≥3 minutes. The target liquidus temperature of the alloy billet is 1512℃; the temperature of the molten steel in the ladle is measured, and the amount and batch of alloy added are calculated based on the temperature measurement results and the target composition of the alloy billet to control the temperature of the molten steel after alloy addition, wherein controlling the molten steel temperature ≥ (liquidus temperature of the target composition of the alloy billet + 10℃) includes: The temperature measurement result t1 is 1534℃≤t1≤1640℃, the target composition of the alloy billet has a molybdenum content of 0.35%-0.45%, and the amount of molybdenum alloy added is 5.85~7.53kg per ton of molten steel; The measured temperature t2 is 1571℃ < t2 ≤ 1700℃. The target composition of the alloy billet has a tungsten content of 1.6%-1.8%, and the amount of tungsten alloy added is 23.23 kg per ton of molten steel to 26.14 kg per ton of molten steel. The process of adding alloy to the molten steel in the ladle includes: moving the ladle of molten steel from the temperature measurement position of the argon station to the position of the fire baffle door under the furnace, and using a forklift to accurately add the bagged alloy into the ladle so that the alloy is evenly distributed on the surface of the molten steel.

2. The method according to claim 1, characterized in that, The alloy includes one or more of ferromolybdenum and ferrotungsten.

3. The method according to claim 1, characterized in that, The alloy billet comprises, by mass percentage: C: 0.08%-0.12%, Si: 0.25%-0.35%, Mn: 0.4%-0.5%, P: ≤0.017%, S: ≤0.005%, Alt<0.02%, Cr: 8.6%-9.0%, W: 1.60%-1.80%, Mo: 0.35%-0.45%, V: 0.16%-0.24%, Nb: 0.05%-0.08%, Ni: 0.1%-0.3%, B: 0.002%-0.004%, N: 0.01%-0.065%, with the balance being iron and unavoidable impurities.

4. The method according to claim 1, characterized in that, Before tapping the molten steel from the converter, the method includes: bypassing argon blowing during the converter smelting process.

5. A steel product, characterized in that, Steel products are made from alloy billets prepared by any one of claims 1 to 4.

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