Production method for controlling inclusion grade of steel 12Cr1MoVG for electric furnace smelting boiler

Abstract

The invention discloses a production method for controlling the inclusion grade of electric furnace smelting boiler steel 12Cr1MoVG, the inclusion grade of electric furnace smelting 12Cr1MoVG is reduced through the technological means of electric furnace end point control, alloy baking, optimization of argon flow in each stage, whole-course protection pouring, molten steel splashing prevention and the like, and finally the electric furnace smelting 12Cr1MoVG material obtains good comprehensive performance. A-class, B-class, D-class and Ds-class inclusions are controlled to be less than or equal to 1.0 grade; besides, the ecological electric furnace is adopted to smelt 12Cr1MoVG, so that the electric energy consumption can be reduced, the emission of carbon dioxide and dioxin is reduced, and the national dual-carbon strategic requirements are met.

Description

Technical Field

[0001] The invention relates to the technical field of metallurgy, and in particular to a production process for controlling the inclusion grade of 12Cr1MoVG boiler steel in electric furnace smelting. Background Art

[0002] With the continuous increase in the construction of my country's power infrastructure and the rapid development of petrochemical, boiler and aviation industries, the country's demand for energy and resources continues to increase. 12Cr1MoVG, as a special material for manufacturing high-pressure and ultra-high-pressure boilers, such as superheater tubes, reheater tubes and steam pipes, plays a pivotal role in my country's large-scale thermal power stations. Due to the harsh use conditions and stringent technical requirements of high-pressure boiler tube billet steel, it is required to have not only good process performance, but also high temperature, high pressure, corrosion resistance and thermal fatigue resistance. In order to achieve these key technical indicators, it is necessary to reasonably design the product composition and strictly control the size, shape and distribution of inclusions. On the other hand, in order to improve product quality and reduce the risks in the use of steel, downstream users require inclusion levels to be stricter than the GB / T5310-2017 standard. Compared with the converter, the steel for smelting boilers in electric furnaces without molten iron has low raw material carbon content, serious molten steel peroxidation, heavy LF desulfurization and deoxidation burden, and large amount of alloy addition, making it more difficult to accurately control the chemical composition.

[0003] Patent application No. 201811232906.0 announced "A 12Cr1MoV low alloy heat-resistant steel and its production process". The chemical composition of the heat-resistant steel is: C: 0.08% to 0.15%, Si: 0.15% to 0.30%, Mn: 0.40% to 0.60%, P: ≤0.03%, S: ≤0.03%, Cr: 0.90% to 1.10%, Mo: 0.25% to 0.35%, V: 0.15% to 0.28%, Als: 0.025% to 0.05%, and the rest is Fe. The process of controlled rolling-relaxation-online low-temperature tempering can efficiently and low-cost produce ferrite + pearlite type 12Cr1MoV low alloy heat-resistant steel with good comprehensive performance, but the patent does not mention smelting parameters and inclusion control measures.

[0004] In order to solve the above technical problems, it is necessary to develop a production process for controlling the inclusion level of 12Cr1MoVG boiler steel in electric furnace smelting to meet users' demand for high-quality boiler tube steel. Summary of the invention

[0005] In view of this, the present disclosure provides a production method for controlling the inclusion grade of 12Cr1MoVG boiler steel smelted in an electric furnace, so as to solve the problem that the chemical composition of 12Cr1MoVG boiler steel smelted in an electric furnace is difficult to accurately control and the inclusion grade is difficult to meet the high standards of customers.

[0006] To achieve the above-mentioned invention object, the production method for controlling the inclusion grade of 12Cr1MoVG steel for electric furnace smelting boiler comprises:

[0007] The method adopts the mode of continuous feeding of scrap steel, preheating of vertical furnace and steel retention in molten pool, and uses ecological electric furnace for smelting. The steel-making conditions of the smelting are that the final carbon is greater than 0.05%, P≤0.010%, and the temperature is 1610-1630℃.

[0008] In the present disclosure and possible embodiments, the steel tapping time is controlled at 5 to 6 minutes. When 15 to 20 tons of steel are tapped, the baked alloys are added in sequence. The baking temperature is 600 to 800°C. The alloys and the added amounts are respectively 14.0 to 15.0 kg / t of low-carbon ferrochrome, 1.5 to 2.5 kg / t of aluminum wire segments, 4.0 to 5.0 kg / t of medium-carbon ferromanganese and 6.0 g / t of ladle lime.

[0009] In the present disclosure and possible embodiments, argon is supplied throughout the steel tapping process, the argon flow rate is 600-750 NL / min, and the steel is tapped in a circular flow.

[0010] In the present disclosure and possible embodiments, in the RH vacuum degassing process, the bottom blowing argon flow rates at each stage are: 150 to 300 NL / min for diffusion deoxidation; 300 to 450 NL / min for carburization, desulfurization and alloying; 100 to 250 NL / min when the composition of the molten steel is stable in the later stage of refining and the temperature rise stage is entered; 50 to 150 NL / min for temperature measurement, sampling and wire feeding; and 30 to 60 NL / min for static argon blowing.

[0011] In the present disclosure and possible embodiments, the static argon blowing time is >15 min.

[0012] In the present disclosure and possible embodiments, in the RH vacuum degassing process, after the ladle is placed on the ladle car, the argon gas is opened and blown open with a flow rate of 300-450NL / min. After entering the working position, the jacking operation is started, the insertion depth of the immersion tube is greater than 400mm, the argon gas is turned off, the vacuum degree is <100Pa, and the duration is >8min. After breaking the air, the argon gas is restored in time, and the silicon calcium wire and the covering agent are fed.

[0013] In the present disclosure and possible embodiments, a full-process protective casting mode is implemented in the continuous casting process, wherein the mode adopts argon protection casting in the long shroud and argon protection in the tundish casting area.

[0014] In the present disclosure and possible embodiments, the continuous casting process takes measures to prevent molten steel from splashing, and the measures to prevent molten steel from splashing include moving the dam backward to expand the flow field of the molten steel in the ladle and adjusting the flow state of the molten steel by a turbulator.

[0015] In the present disclosure and possible embodiments, in the continuous casting process, electromagnetic stirring of the crystallizer and electromagnetic stirring at the end of solidification are turned on, and the protective slag is low-carbon steel protective slag.

[0016] In the present disclosure and possible embodiments, in the LF refining process, molten steel is fed into the LF furnace, the arrival temperature is 1520-1540°C, a slight positive pressure is maintained in the furnace, submerged arc heating is adopted, and large argon blowing is prohibited by adjusting the argon flow rate during the refining process; after the initial power supply is 2-3 minutes to form liquid slag, carbon powder is added; a CaO-Al2O3-SiO2 refining slag system is adopted, and white slag operation is carried out throughout the process; a full analysis sample is taken when the temperature reaches 1560-1600°C, and 5.0-7.0 kg / t of lime, 1.5-2.5 kg / t of ferrosilicon, 4.0-5.0 kg / t of ferromolybdenum, 3.0-4.0 kg / t of ferrovanadium, and 1.5-4.0 kg / t of low-carbon ferrochromium are added to adjust the composition; the S of the molten steel outgoing is ≤0.010%, and the liquid surface is strictly prohibited from being exposed during the transfer of the ladle after refining.

[0017] The present invention has the following beneficial effects:

[0018] The production method of the present invention for controlling the inclusion level of 12Cr1MoVG steel for boiler smelting in an electric furnace reduces the inclusion level of 12Cr1MoVG steel for electric furnace smelting by means of electric furnace endpoint control, alloy baking, optimization of argon flow rate at each stage, full-process protection pouring, prevention of molten steel splashing and other process means, wherein the carbon-oxygen product is reduced by reducing the steel tapping temperature, and the endpoint carbon content is increased, thereby reducing the oxygen content of the molten steel, preventing overoxidation, reducing the source of endogenous inclusions from the source, and molten steel is tapped at a low temperature, and the erosion of the ladle lining is also reduced, and the number of foreign inclusions is reduced; by sealing and heating the alloy baking furnace, ferromanganese and ferrochrome are dehydrated and baked, which can reduce the entry of foreign gas into the molten steel on the one hand, and effectively reduce the temperature drop of the molten steel on the other hand, which is conducive to reducing the steel tapping temperature. Avoid excessive oxygen content in molten steel, reduce the number of deoxidation products, and reduce inclusions in steel; by reasonably controlling the argon flow rate at each stage and extending the net argon blowing time, ensure that the inclusions in the molten steel are fully floated, prevent the secondary oxidation of the molten steel, and reduce the smelting cost; prevent the secondary oxidation and nitrogen absorption of the molten steel by measures such as full-process protection of pouring and prevention of molten steel splashing; finally, the inclusion level of 12Cr1MoVG smelted in an electric furnace is reduced by the method of the present invention, and the 12Cr1MoVG material smelted in an electric furnace has good comprehensive performance, and the A, B, D and Ds inclusions are controlled to be ≤1.0 level; in addition, the use of an ecological electric furnace to smelt 12Cr1MoVG can reduce electricity consumption, reduce carbon dioxide and dioxin emissions, and meet the requirements of the national "dual carbon" strategy. DETAILED DESCRIPTION

[0019] The present disclosure is described below based on embodiments, but it is worth noting that the present disclosure is not limited to these embodiments. In the detailed description of the present disclosure below, some specific details are described in detail. However, for the parts that are not described in detail, those skilled in the art can also fully understand the present disclosure. At the same time, unless the context clearly requires, the words "including", "comprising" and the like in the entire specification and claims should be interpreted as including rather than exclusive or exhaustive meanings; that is, the meaning of "including but not limited to".

[0020] The production method of the present invention for controlling the inclusion grade of 12Cr1MoVG steel for electric furnace smelting boiler is described in detail, and the method steps are as follows:

[0021] 1. The chemical composition of molten steel for smelting 12Cr1MoVG is as follows:

[0022] C: 0.08%~0.15%, Si: 0.17%~0.37%, Mn: 0.40%~0.70%, P: ≤0.020%, S: ≤0.010%, Cr: 0.90%~1.20%, Mo: 0.25%~0.35%, V: 0.15%~0.30%, Al: ≤0.020%, Ni≤0.20%, Cu≤0.16%, As≤0.015%, Sn≤0.015%, Sb≤0.010%, Pb≤0.008%, Bi≤0.010%, and the rest is Fe.

[0023] 2. The production process is ecological electric furnace smelting → LF → RH → large square billet continuous casting, where:

[0024] (1) Ecological electric furnace smelting:

[0025] The ecological electric furnace adopts continuous feeding of scrap steel, preheating of vertical furnace and smelting in the molten pool steel retention mode.

[0026] The amount of scrap steel added is 80 to 100 tons. After being preheated to 600 to 800°C by the flue gas in the furnace, the scrap steel is pushed into the smelting area in the furnace by the steel pusher. In order to prevent the electrode from ionizing the N2 in the air and increasing the nitrogen in the molten steel, it is necessary to ensure that the height of the foam slag in the furnace can meet the submerged arc requirements.

[0027] Add 37.0-39.0kg / t of lime, 26.0-28.0kg / t of dolomite, and spray 12.0-15.5kg / t of carbon powder. When the tapping conditions meet the end point carbon greater than 0.05%, P≤0.010%, and the temperature is 1610-1630℃, start tapping.

[0028] The inventors of this application have found that the final oxygen content and tapping temperature of the electric furnace are too high, which is not conducive to the quality and cost control of molten steel. Therefore, the present invention is designed to reduce the carbon-oxygen accumulation and increase the final carbon content by reducing the tapping temperature during the electric furnace smelting stage, thereby reducing the oxygen content of the molten steel, preventing overoxidation, and reducing the source of endogenous inclusions from the source. In addition, low-temperature tapping of molten steel can also reduce the erosion of the ladle lining and reduce the number of foreign inclusions.

[0029] Argon is supplied throughout the steel tapping process, with a flow rate of 600-750NL / min. The steel is tapped in a circular flow, and the steel liquid is prohibited from flowing freely. The tapping time is controlled at 5-6min. When 15-20t of steel is tapped, the baked alloys are added in sequence, and the baking temperature is 600-800℃. Among them, low-carbon ferrochrome is 14.0-15.0kg / t, aluminum wire segment is 1.5-2.5kg / t, medium-carbon ferromanganese is 4.0-5.0kg / t, and 6.0kg / t of ladle lime is added.

[0030] In the present invention, inspired by the above findings, the ferromanganese and ferrochrome are dehydrated and baked by sealed heating in an alloy baking furnace. On the one hand, this can reduce the entry of foreign gas into the molten steel, and on the other hand, it can effectively reduce the temperature drop of the molten steel, which is beneficial to lowering the steelmaking temperature, avoiding excessive oxygen content in the molten steel, reducing the number of deoxidation products, and reducing inclusions in the steel.

[0031] (2) LF refining:

[0032] The molten steel leaving the ecological electric furnace is sent to the LF furnace for refining. The LF arrival temperature is 1520-1540℃. The LF furnace cover is ensured to be in close contact with the ladle, a slightly positive pressure is maintained in the furnace, submerged arc heating is used to prevent arc light leakage, the argon flow rate is continuously adjusted during the refining process, and large argon blowing is prohibited to prevent nitrogen absorption.

[0033] 2 to 3 minutes after the initial power supply to form liquid slag, carbon powder is added to start carbonization. The CaO-Al2O3-SiO2 refining slag system is used. The white slag operation is carried out throughout the process. The temperature reaches 1560-1600℃ to take a full analysis sample, and then 5.0-7.0kg / t of lime, 1.5-2.5kg / t of ferrosilicon, 4.0-5.0kg / t of ferromolybdenum, 3.0-4.0kg / t of ferrovanadium and 1.5-4.0kg / t of low-carbon ferrochromium are added to adjust the composition to ensure that the S of the molten steel leaving the station is ≤0.010%. It is strictly forbidden to expose the liquid surface during the transfer of the ladle after refining.

[0034] (3) RH vacuum degassing:

[0035] After the LF refining ladle is placed on the ladle car, turn on the argon gas to blow it open, with a flow rate of 300-450NL / min. After entering the working position, start the jacking operation, the immersion tube insertion depth is greater than 400mm, turn off the argon gas, the vacuum degree is <100Pa, and the duration is >8min. After breaking the air, restore the argon gas in time, feed 200m / furnace of silicon-calcium wire and 60-90kg / furnace of covering agent.

[0036] The inventors of the present application have found that bottom blowing argon has a great influence on slagging, composition fine-tuning, desulfurization, deoxidation and inclusion floating. Therefore, in order to reasonably control the argon flow rate at each stage, the present invention has made corresponding designs for the argon flow rate at each stage, as follows:

[0037] In order to make the inclusions in the molten steel float fully, prevent the secondary oxidation of the molten steel, and reduce the smelting cost, it is necessary to reasonably control the argon flow rate at each stage. During diffusion deoxidation, medium-intensity stirring is used to prevent the exposed molten steel surface from inhaling air, and the flow rate is controlled at 150-300NL / min; during carburization, desulfurization, and alloying, a large amount of argon stirring is required to strengthen the mixing of slag and material transfer, promote the desulfurization reaction, and the flow rate is controlled at 300-450NL / min; in the later stage of refining, the composition of the molten steel has stabilized and entered the heating stage. The argon flow rate should not be too large, otherwise it will easily lead to arc instability. , increase electrode consumption, the flow rate is controlled at 100-250NL / min; avoid slag rolling and secondary oxidation during temperature measurement, sampling and wire feeding, and the flow rate is 50-150NL / min; when blowing argon statically, the argon flow rate is controlled so that the molten steel is not visible when the steel liquid surface moves slightly, to ensure that the argon bubbles fully adsorb inclusions during the floating process, the flow rate is 30-60NL / min, and the static argon blowing time is>15min; in the present invention, the static argon blowing time is extended compared with the traditional time, because extending the net argon blowing time can promote the floating of inclusions in the molten steel.

[0038] (4) Continuous casting:

[0039] The molten steel after RH vacuum degassing is hoisted to the casting position, and the superheat of the molten steel is controlled to be less than 30℃. A continuous slag detection device is used for the continuous casting ladle to prevent slag from falling from the ladle.

[0040] In the present invention, the whole process of casting is required to be protected, and argon protection is adopted for long water nozzle casting and argon protection is adopted for the casting area of ​​the middle ladle; the dam is moved backward to expand the flow field of the molten steel in the ladle, and the flow state of the molten steel is adjusted by the turbulator to prevent the molten steel from splashing, thereby achieving the purpose of preventing the secondary oxidation of the molten steel and nitrogen absorption.

[0041] In this process, electromagnetic stirring of the crystallizer and electromagnetic stirring at the end of solidification are turned on. The electromagnetic stirring parameters are shown in Table 1. Low-carbon steel protective slag is used as the protective slag, and the billet pulling speed is controlled according to Table 2.

[0042] Table 1 Electromagnetic stirring parameters

[0043]

[0044] Table 2 Casting speed control targets

[0045] Superheat℃ Blank <15 15～20 20～30 30～35 35～40 ＞40 Pulling speed m / min Bloom 0.50 0.50 0.48 0.45 0.45 0.43

[0046] Example 1

[0047] According to the production method of the present invention for controlling the inclusion grade of 12Cr1MoVG steel for boiler smelting in an electric furnace, 12Cr1MoVG is prepared, and the specific steps are as follows:

[0048] 1. By weight percentage, the chemical composition of 12Cr1MoVG is:

[0049] C: 0.08%~0.15%, Si: 0.17%~0.37%, Mn: 0.40%~0.70%, P: ≤0.020%, S: ≤0.010%, Cr: 0.90%~1.20%, Mo: 0.25%~0.35%, V: 0.15%~0.30%, Alt: ≤0.020%, Ni≤0.20%, Cu≤0.16%, As≤0.015%, Sn≤0.015%, Sb≤0.010%, Pb≤0.008%, Bi≤0.010%, and the rest is Fe.

[0050] 2. According to the process flow of ecological electric furnace full scrap steel smelting → LF → RH → large square billet continuous casting, the specific process steps are as follows:

[0051] (1) Ecological electric furnace smelting:

[0052] The ecological electric furnace adopts continuous feeding of scrap steel, preheating of vertical furnace and smelting in the molten pool steel retention mode.

[0053] The amount of scrap steel added is 84t. After being preheated to 650℃ by the flue gas in the furnace, the scrap steel is pushed into the smelting area in the furnace by the steel pusher. In order to prevent the electrode from ionizing N2 in the air and increasing nitrogen in the molten steel, it is necessary to ensure that the height of the foam slag in the furnace can meet the submerged arc requirements.

[0054] 38.0kg / t of lime, 27.0kg / t of dolomite were added, 15.2kg / t of carbon powder was injected, the steel tapping end point C: 0.05%, P: 0.004%, and the temperature was 1625℃.

[0055] Argon is supplied throughout the steel tapping process with a flow rate of 650NL / min. The steel is tapped in a circular flow and the molten steel is prohibited from spreading. The tapping time is controlled at 5-6min. When 15-20t of steel is tapped, the baked alloys are added in sequence. The baking temperature is controlled between 600 and 800℃ to reduce the entry of foreign gas into the molten steel. Among them, 14.0kg / t of low-carbon ferrochrome, 2.0kg / t of aluminum segments, 4.2kg / t of medium-carbon ferromanganese are added, and 600kg / furnace of ladle lime is added.

[0056] (2) LF refining:

[0057] The molten steel after leaving the station is sent to the LF furnace for refining. The LF arrival temperature is 1524℃. Ensure that the LF furnace cover is in close contact with the ladle, maintain a slightly positive pressure in the furnace, use submerged arc heating to prevent arc light leakage, and continuously adjust the argon flow rate during the refining process. Large argon blowing is prohibited to prevent nitrogen absorption.

[0058] 2 minutes after the initial power supply to form liquid slag, carbon powder is added to start carbon increase, and the CaO-Al2O3-SiO2 refining slag system is used. White slag operation is carried out throughout the process. The temperature reaches 1580℃ and a full analysis sample is taken. Then 6.0kg / t of lime, 2.1kg / t of ferrosilicon, 4.5kg / t of ferromolybdenum, 3.3kg / t of ferrovanadium and 3.8kg / t of low-carbon ferrochrome are added to adjust the composition. The S of the molten steel outgoing is 0.005%. It is strictly forbidden to expose the liquid surface during the transfer of the ladle after refining.

[0059] (3) RH vacuum degassing:

[0060] After the ladle is placed on the ladle car, turn on the argon gas to blow it open, with a flow rate of 400NL / min. After entering the working position, start the jacking operation, the immersion tube insertion depth is greater than 400mm, turn off the argon gas, the vacuum degree is <100Pa, and the duration is 8min. After breaking through the air, restore the argon gas in time, feed 200m / furnace of silicon-calcium wire and 60kg / furnace of covering agent, and the static argon blowing time is 20min.

[0061] In order to make the inclusions in the molten steel float fully, it is necessary to reasonably control the argon flow rate at each stage: 200NL / min for diffusion deoxidation, 350NL / min for carburization, desulfurization and alloying, 200NL / min for the later stage of refining, 100NL / min for temperature measurement, sampling and wire feeding, and 50NL / min for static argon blowing.

[0062] (4) Continuous casting:

[0063] The molten steel after vacuum degassing was hoisted to the casting position, the average superheat of the molten steel was 30℃, the casting speed was 0.48m / min, and the continuous casting ladle was equipped with a continuous slag detection device to prevent slag from falling from the ladle. The whole process of casting was protected to prevent secondary oxidation and nitrogen absorption of the molten steel. The electromagnetic stirring of the crystallizer and the electromagnetic stirring at the end of solidification were turned on. The protective slag was low-carbon steel protective slag. The continuous casting parameters are shown in Table 3.

[0064] Table 3 Continuous casting process of the present invention

[0065]

[0066] 3. The composition and test results of the 12Cr1MoVG finished product produced in this embodiment are shown in Table 4-8.

[0067] Table 4 Composition of 12Cr1MoVG finished product of this embodiment 1

[0068]

[0069] Table 5 12Cr1MoVG non-metallic inclusion test results of this embodiment 1

[0070] Example A thin A thick B thin B thick C Thin C thick D Thin D thick Ds 1 1.0 1.0 0.5 0.5 0 0 0 0 0.5 1 1.0 1.0 0.5 0.5 0 0 0 0 0.5 standard ≤1.5 ≤1.5 ≤1.5 ≤1.5 ≤1.0 ≤1.0 ≤1.5 ≤1.5 ≤1.5 Internal Control ≤1.0 ≤1.5 ≤1.0 ≤1.5 ≤1.0 ≤1.0 ≤1.0 ≤1.5 ≤1.5

[0071] Note: The non-metallic inclusion inspection adopts GB / T10561-2005 A method.

[0072] Table 6 12Cr1MoVG low magnification test results of this embodiment 1

[0073]

[0074]

[0075] Table 7 12Cr1MoVG gas content test results of this embodiment 1

[0076] Example Specification / mm N / ppm H / ppm O / ppm 1 85 72 0.4 11 standard ≤80 ≤2 ≤30

[0077] Table 8 12Cr1MoVG upset forging test results of this embodiment 1

[0078] Example Specification / mm Test results 1 85 qualified

[0079] According to the data in Tables 4-8, in accordance with the GB / T5310-2017 standard, the inclusion levels of 12Cr1MoVG produced in Example 1 are all below level 1.0, which is stricter than the GB / T5310-2017 standard, meeting the customer's requirements that are stricter than the national standard, and all other indicators also meet the standard requirements.

[0080] The above-described embodiments are only embodiments of the present disclosure, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the present disclosure. It should be noted that, for a person of ordinary skill in the art, without departing from the concept of the present disclosure, several variations, equivalent substitutions, improvements, etc. may be made, all of which fall within the scope of protection of the present disclosure. Therefore, the scope of protection of the present disclosure shall be subject to the attached claims.

Claims

1. A production method for controlling the inclusion level of 12Cr1MoVG boiler steel in electric furnace smelting, characterized in that: include: The method adopts the mode of continuous feeding of scrap steel, preheating of vertical furnace and steel retention in molten pool, and uses ecological electric furnace for smelting. The steel-making conditions of the smelting are that the final carbon is greater than 0.05%, P≤0.010%, and the temperature is 1610-1630℃.

2. The method for controlling the inclusion level of 12Cr1MoVG steel for electric furnace smelting boiler according to claim 1, characterized in that: The steel tapping time is controlled at 5 to 6 minutes. When 15 to 20 tons of steel are tapped, the baked alloys are added in sequence. The baking temperature is 600 to 800° C. The alloys and the added amounts are respectively 14.0 to 15.0 kg / t of low-carbon ferrochrome, 1.5 to 2.5 kg / t of aluminum wire segments, 4.0 to 5.0 kg / t of medium-carbon ferromanganese and 6.0 g / t of ladle lime.

3. The method for controlling the inclusion level of 12Cr1MoVG steel for electric furnace smelting boiler according to claim 2, characterized in that: Argon is supplied throughout the steel tapping process, with an argon flow rate of 600-750NL / min, and steel is tapped in a circular flow.

4. The method for controlling the inclusion grade of 12Cr1MoVG steel for electric furnace smelting boiler according to any one of claims 1 to 3, characterized in that: In the RH vacuum degassing process, the bottom blowing argon flow rates at each stage are: 150-300NL / min for diffusion deoxidation; 300-450NL / min for carburization, desulfurization and alloying; 100-250NL / min when the composition of the molten steel is stable in the later stage of refining and the temperature rise stage is entered; 50-150NL / min for temperature measurement, sampling and wire feeding; and 30-60NL / min for static argon blowing.

5. The production method for controlling the inclusion level of 12Cr1MoVG steel for electric furnace smelting boiler according to claim 4, characterized in that: The static argon blowing time is>15min.

6. The method for controlling the inclusion level of 12Cr1MoVG steel for electric furnace smelting boiler according to claim 5, characterized in that: In the RH vacuum degassing process, after the ladle is placed on the ladle car, the argon gas is opened and blown open with a flow rate of 300-450NL / min. After entering the working position, the jacking operation is started, the insertion depth of the immersion tube is greater than 400mm, the argon gas is turned off, the vacuum degree is <100Pa, and the duration is >8min. After breaking the air, the argon gas is restored in time, and the silicon calcium wire and the covering agent are fed.

7. The method for controlling the inclusion grade of 12Cr1MoVG steel for electric furnace smelting boiler according to any one of claims 1 to 3, 5 or 6, characterized in that: A full-process protective casting mode is implemented in the continuous casting process, wherein the mode adopts argon protection casting at the long water gate and argon protection in the tundish casting area.

8. The method for controlling the inclusion level of 12Cr1MoVG steel for electric furnace smelting boiler according to claim 7, characterized in that: The continuous casting process adopts measures to prevent molten steel from splashing, and the measures to prevent molten steel from splashing include measures to move the dam backward to expand the flow field of the molten steel in the ladle and measures to adjust the flow state of the molten steel through a turbulator.

9. The method for controlling the inclusion level of 12Cr1MoVG steel for electric furnace smelting boiler according to claim 8, characterized in that: In the continuous casting process, electromagnetic stirring of the crystallizer and electromagnetic stirring at the end of solidification are turned on, and low-carbon steel protective slag is used as the protective slag.

10. The production method for controlling the inclusion level of 12Cr1MoVG steel for electric furnace smelting boiler according to claim 8 or 9, characterized in that: In the LF refining process, molten steel is fed into the LF furnace with an arrival temperature of 1520-1540℃. A slight positive pressure is maintained in the furnace, and submerged arc heating is adopted. During the refining process, large argon blowing is prohibited by adjusting the argon flow rate. Carbon powder is added 2-3 minutes after the initial power supply to form liquid slag. The CaO-Al2O3-SiO2 refining slag system is adopted, and white slag operation is carried out throughout the process. When the temperature reaches 1560-1600℃, a full analysis sample is taken, and 5.0-7.0kg / t of lime, 1.5-2.5kg / t of ferrosilicon, 4.0-5.0kg / t of ferromolybdenum, 3.0-4.0kg / t of ferrovanadium, and 1.5-4.0kg / t of low-carbon ferrochromium are added to adjust the composition. The S of the molten steel leaving the station is ≤0.010%, and the liquid surface is strictly prohibited from being exposed during the transfer of the ladle after refining.

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