A smelting process for low-nitrogen, low-oxygen, boron-containing steel

Abstract

The present invention relates to a method for smelting low-silicon and low-aluminum steel for a steam turbine main shaft, which comprises the following chemical components in terms of weight percentage: C≤0.35%, Si≤0.10%, Mn0.20%-0.40%, Cr 1.50-2.00%, Ni 3.25-3.75%, Mo 0.30-0.60%, V 0.07~0.15%, P≤0.010%, S≤0.010%, Al≤0.010%, Cu≤0.15%, and the balance is iron; the production process of the steel adopts an electric arc furnace to melt scrap steel, decarburize, dephosphorize, and tap steel, argon blowing in a ladle for refining, deoxidation and desulfurization, argon blowing for feeding aluminum wire, and adjusting the composition. When the temperature meets the requirements, the ladle is hoisted into a vacuum tank for further degassing and refining, and after vacuum treatment, it is cast into an electrode blank; its smelting process also includes electroslag remelting, using a 65%:25%:10% full pre-melted slag system + 4KgSiO2, and argon protection measures to electroslag the electrode blank into an electroslag ingot; the low-silicon and low-aluminum steel for the turbine main shaft made by this method has mechanical properties that meet the use requirements.

Description

Technical Field

[0001] The present invention belongs to the technical field of steelmaking process, and relates to a smelting process of low-nitrogen, low-oxygen, boron-containing steel which can significantly improve the hardenability of steel and improve the mechanical properties, cold deformation properties, welding properties and high-temperature properties of steel. Background Art

[0002] The greatest effect of boron in steel is that trace amounts of boron can significantly improve the steel's hardenability, improving its mechanical properties, cold deformation resistance, welding performance, and high-temperature performance. A trace amount of boron (0.001% to 0.002%) in steel can exponentially increase the hardenability of medium and low-structural steels. In the past, adjusting the boron composition involved adding ferroboron after vacuum degassing. Adding ferroboron increased the argon flow rate, blowing open the slag surface to release the molten steel, then wrapping the ferroboron with aluminum foil and adding it directly to the molten steel. This method of adding ferroboron makes the molten steel easily absorb air, resulting in a short residence time for ferroboron in the molten steel, a low yield, and a high likelihood of incompatibility with the molten steel composition. Summary of the Invention

[0003] The purpose of the present invention is to overcome the problems of unstable timing and yield of adding boron in the existing smelting technology and to provide a smelting process for low-nitrogen, low-oxygen, boron-containing steel. The steel smelted by this process has [H]≤1.1PPm, [O]≤18PPm, [N]≤60PPm, and [B]0.0012% to 0.002%. Trace boron can multiply its hardenability.

[0004] The object of the present invention is achieved like this:

[0005] A low-nitrogen, low-oxygen, boron-containing steel, characterized in that it comprises the following chemical components in weight percentage: C 0.50-0.60%, Si≤0.35%, Mn 0.60-0.90%, B 0.001-0.002%, Cr≤0.20%, Ni≤0.20%, Mo≤0.20%, Cu≤0.20%, P≤0.005%, S≤0.002%, and the balance is iron.

[0006] A low-nitrogen, low-oxygen, boron-containing steel, characterized by comprising, in weight percentage, the optimal selection of the following chemical components: C 0.52-0.58%, Si 0.15-0.35%, Mn 0.70-0.90%, B 0.001-0.002%, Cr≤0.20%, Ni≤0.20%, Mo≤0.10%, Cu≤0.10%, P≤0.005%, S≤0.002%, Al≤0.020%, the sum of the five harmful elements (As+Sn+Pb+Sb+Bi)≤0.025%, and the balance being iron.

[0007] A smelting process for low-nitrogen, low-oxygen, boron-containing steel as described above is characterized in that: the steel smelting process adopts an electric arc furnace to melt scrap steel, argon blowing in a ladle for refining, deoxidation and desulfurization, control of aluminum content, adjustment of boron content and temperature to meet requirements, hanging the ladle into a vacuum tank for further degassing and refining, and casting into steel ingots; specifically comprising the following steps:

[0008] Step 1) Select the charge: Select the raw materials for electric arc furnace smelting according to weight percentage, including 50-70% high-quality carbon steel scrap, 20-40% pig iron or sponge iron, and 10-30% return steel carbon head. Do not add slag steel or miscellaneous scrap steel when batching. The first sample of electric arc furnace melt analysis shows that As, Sn, Pb, Sb, and Bi are all ≤0.010%.

[0009] Step 2), the electric arc furnace starts to oxidize carbon ≥ 0.80%, the oxidation temperature ≥ 1550 ° C, and the decarburization amount ≥ 0.40%; the electric arc furnace tapping end point [C] ≥ 0.30%, [P] ≤ 0.003%, the temperature ≥ 1630 ° C, before the electric furnace tapping, add 2.0 kg / t of aluminum blocks to the ladle for precipitation deoxidation to quickly reduce the oxygen content in the steel, add 5.0 kg / t of high calcium lime as slag-making material to remove sulfur in the steel to the maximum extent, and the amount of steel left in the electric furnace is ≥ 5 tons to ensure that no slag is left when tapping to prevent phosphorus reversion of the molten steel;

[0010] Step 3), after the refining bag is in place, connect the argon gas, add 1~2.0kg / t of calcium carbide, 1.0~2.0kg / t of carbon powder, and 1.0~2.0kg / t of ferrosilicon powder for diffusion deoxidation, send electrochemical slag, measure the temperature, take samples, adjust the chemical composition after the slag is white, and blow argon to feed the aluminum wire according to the residual aluminum; during the refining period, use 0.5~1.0kg / t of carbon powder, 0.5~1.0kg / t of ferrosilicon powder, and 0.5~1.0kg / t of calcium silicon powder in small batches or multiple batches for deoxidation and maintain a reducing atmosphere to ensure uniform composition and temperature; after fully stirring under the white slag, take the first sample for analysis and analyze the N content at the same time. In order to enhance the desulfurization and deoxidation capacity of the reduced slag, the main components of the refined slag used according to the weight percentage regulations are: CaO 45~50%, SiO2 5.0~8.0%, MgO 3.0~5.0%, Fe2O3≤1.0%, Al2O3 40~45%, adjust the chemical composition of C, Si and Mn in the molten steel according to the analysis results of the first sample, and adjust the Al content in the molten steel by 0.015~0.030% according to the sample composition;

[0011] Step 4), ferroboron is added before vacuum degassing treatment, and then ferroboron is added at a 100% recovery rate after power supply for 5 minutes, and the boron content is adjusted to 0.003%. When adding boron, the ferroboron is wrapped with iron sheet, and the wrapped ferroboron is tied to the iron rod with iron wire. The argon flow rate is adjusted to 120-150NL / min, and the slag surface is slightly blown open to leak molten steel. Then the ferroboron is quickly inserted into the molten steel for 10-20 seconds, and the iron rod is pulled out. It is weakly stirred for 3-5 minutes, and the temperature is 1640-1660℃ and the bag is hung into the vacuum tank for degassing;

[0012] Step 5), the molten steel temperature is 1630-1650℃, and the steel enters the vacuum tank for exhaust. The vacuum degree is maintained below 67Pa for ≥15 minutes. After VD, hydrogen and oxygen are determined online to control [H]≤0.8ppm and [O]≤5.0ppm. A glass tube sample is taken to analyze the nitrogen content and control [N]≤40ppm. The residual [Al] is controlled at 0.010-0.020%. When the residual [Al] is lower than the required value, an Al wire should be fed. Argon is blown and weakly stirred for ≥10 minutes before tapping. Steel is poured directly after VD. The ladle temperature is 1530-1540℃. The molten steel must not be exposed during soft argon blowing, and a large amount of argon should not be used for stirring and cooling. When the temperature is appropriate, the steel can be tapped for pouring.

[0013] Step 6) It is preferred to use an ingot mold with good inner wall quality and clean it. The ingot mold used must be a tooling with a smooth inner wall, no cracks, and no pits, and it must be cleaned and dusted thoroughly. The ingot mold used must be preheated before sitting or a continuous ingot mold must be used. The mold temperature must be ≥30°C. After the ingot mold is seated, the protective slag is hung and the mold mouth is covered with a protective cover to prevent ash, dust and steel flowers from falling into the mold.

[0014] Step 7) After the calming is completed, drain the outside of the injection pipe to let the drainage sand and low-temperature sand-containing molten steel flow out, control the flushing flow rate to 120-200kg, and then quickly flush the low-temperature steel in the nozzle to preheat the upper and lower slides, and then quickly direct the car, after the injection pipe is aligned, open the nozzle 60-80%, let the molten steel quickly fill the soup channel, exhaust the gas in the soup channel, so that the molten steel does not gushing and splashing;

[0015] Step 8) When the molten steel enters the mold after pouring, follow the flow in time to fill the ingot tail ball to form a molten pool, reduce eddy circulation, and maintain a steady rise; when the molten steel in the ingot body is 50 to 80 mm away from the cap mouth line, the flow must be reduced to allow the molten steel to steadily enter the cap mouth. If the ingot body injection speed is still maintained, a mixture of steel slag will quickly form at the chamfer of the ingot body and the cap mouth, causing splashing, resulting in various quality defects at the head of the ingot; after the molten steel is capped, mid-flow filling begins, and the argon flow rate is reduced as required, while the injection flow is gradually reduced. When it reaches 2 / 3 of the cap mouth line, 1 to 3 kg of heating agent is added. At this time, a trickle filling is started, and the pouring height is specified, and the nozzle is closed; after the pouring is completed, carbonized rice husks are added to further maintain the riser shrinkage compensation effect.

[0016] The beneficial effects of the present invention are as follows: Through optimized ingredient preparation, electric arc furnace smelting, and argon-blowing ladle furnace refining and feeding aluminum wire, the [Al] content is controlled to 0.015-0.030%. Ferroboron is added before vacuum degassing. When adding boron, the ferroboron is wrapped with iron sheets and tied to an iron rod with wire. The argon flow rate is adjusted to 120-150 NL / min (the slag surface is slightly blown open to allow molten steel to leak out). The ferroboron is then inserted into the molten steel for 20-30 seconds, after which the rod is removed and weakly stirred for 3-5 minutes. The ladle is then placed in a vacuum tank for degassing at a temperature of 1630-1650°C. The steel smelted using this process has a [B] content of 0.0012%-0.002%. This trace amount of boron can significantly improve its hardenability. DETAILED DESCRIPTION

[0017] Example 1: A smelting process for low-nitrogen, low-oxygen, boron-containing steel, comprising the following steps:

[0018] Step 1) Select the charge: Select the raw materials for electric arc furnace smelting according to weight percentage, including 50-70% high-quality carbon steel scrap, 20-40% pig iron or sponge iron, and 10-30% return steel carbon head. Do not add slag steel and other miscellaneous scrap steel when batching. The first sample of electric arc furnace melt analysis shows that As, Sn, Pb, Sb, and Bi are all ≤0.010%.

[0019] Step 2), the electric arc furnace starts to oxidize carbon ≥ 0.80%, the oxidation temperature ≥ 1550 ° C, and the decarburization amount ≥ 0.40%; the electric arc furnace tapping end point [C] ≥ 0.30%, [P] ≤ 0.003%, the temperature ≥ 1630 ° C, before the electric furnace tapping, add 2.0 kg / t of aluminum blocks to the ladle for precipitation deoxidation to quickly reduce the oxygen content in the steel, add 5.0 kg / t of high calcium lime as slag-making material to remove sulfur in the steel to the maximum extent, and the amount of steel left in the electric furnace is ≥ 5 tons to ensure that no slag is left when tapping to prevent phosphorus reversion of the molten steel;

[0020] Step 3) After the refining bag is in place, connect the argon gas, add 1-2.0kg / t of calcium carbide, 1.0-2.0kg / t of carbon powder, and 1.0-2.0kg / t of ferrosilicon powder for diffusion deoxidation, send the electrochemical slag, measure the temperature, take samples, adjust the chemical composition after the slag turns white, and blow argon to feed the aluminum wire according to the residual aluminum. During refining, deoxidize the steel in small batches or multiple batches using 0.5-1.0 kg / t of carbon powder, 0.5-1.0 kg / t of ferrosilicon powder, and 0.5-1.0 kg / t of calcium silicate powder to maintain a reducing atmosphere and ensure uniform composition and temperature. After thorough stirring under white slag, take the first sample for analysis and analyze the nitrogen content simultaneously. To enhance the desulfurization and deoxidation capabilities of the reducing slag, the main components of the refining slag used are: CaO 45-50%, SiO2 5.0-8.0%, MgO 3.0-5.0%, Fe2O3 ≤1.0%, Al2O3 40-45%. Adjust the chemical composition of C, Si, and Mn in the molten steel based on the results of the first sample analysis. Adjust the Al content in the molten steel by 0.015-0.030% based on the sample composition.

[0021] Step 4), ferroboron is added before vacuum degassing treatment, and then ferroboron is added at a 100% recovery rate after power supply for 5 minutes, and the boron content is adjusted to 0.003%. When adding boron, the ferroboron is wrapped with iron sheet, and the wrapped ferroboron is tied to the iron rod with iron wire. The argon flow rate is adjusted to 120-150NL / min, and the slag surface is slightly blown open to leak molten steel. Then, the ferroboron is inserted into the molten steel for 10-20 seconds, and the iron rod is pulled out. It is weakly stirred for 3-5 minutes, and the temperature is 1640-1660℃ and the bag is hung into the vacuum tank for degassing;

[0022] Step 5), the molten steel temperature is 1630-1650℃, and it enters the vacuum tank for evacuation, and the vacuum degree is maintained below 67Pa for ≥15 minutes. After VD, hydrogen and oxygen are determined online to control [H]≤0.8ppm and [O]≤5.0ppm; take a glass tube sample to analyze the nitrogen content and control [N]≤40ppm; control the residual [Al] to 0.010-0.020% (when the residual [Al] is lower than the required value, the Al wire should be fed), and the argon blowing and weak stirring time before tapping is ≥10 minutes. After VD, steel is poured directly, and the ladle temperature is 1530-1540℃. The molten steel must not be exposed during soft argon blowing, and large amounts of argon must not be used for stirring and cooling. When the temperature is appropriate, the steel can be tapped for pouring;

[0023] Step 6) Choose bricks with smooth inner wall and no burrs, no cracks and smooth inner wall for the brick channel and injection pipe; when laying, the brick teeth should be evenly mortared and not too much; after the laying is completed, the flow steel brick system should be blown clean with compressed air; the steel ingot mold with good inner wall quality is preferred and cleaned. The ingot mold used must be a tooling with smooth inner wall, no cracks and no pits, and it must be brushed clean and thoroughly blown and dusted. The steel ingot mold used must be preheated before sitting or use a continuous steel ingot mold, and the standby mold temperature must be ≥30℃; after the ingot mold is seated, the protective slag is hung well and the mold mouth is covered with a protective cover to prevent ash, dust and steel flowers from falling into the mold;

[0024] Step 7) After the calming is completed, drain the outside of the injection pipe to let the drainage sand and low-temperature sand-containing molten steel flow out, control the flushing flow rate to 120-200kg, and then quickly flush the low-temperature steel in the nozzle to preheat the upper and lower slides, and then quickly direct the car, after the injection pipe is aligned, open the nozzle 60-80%, let the molten steel quickly fill the soup channel, exhaust the gas in the soup channel, so that the molten steel does not gushing and splashing;

[0025] Step 8) When the molten steel enters the mold after pouring, follow the flow in time to fill the tail ball of the ingot to form a molten pool, reduce eddy circulation, and maintain a steady rise; when the molten steel in the ingot body is 50 to 80 mm away from the cap mouth line, the flow must be reduced to allow the molten steel to steadily enter the cap mouth. If the ingot body injection speed is still maintained, a mixture of steel slag will quickly form at the chamfer of the ingot body and the cap mouth, causing splashing, resulting in various quality defects at the head of the ingot; after the molten steel is capped, mid-flow filling begins, and the argon flow rate is reduced as required, while the injection flow is gradually reduced. When it reaches 2 / 3 of the cap mouth line, 1-3 kg of heating agent is added. At this time, a trickle filling is started, and the pouring height is specified, and the nozzle is closed; after the pouring is completed, carbonized rice husks are added to further maintain the riser shrinkage compensation effect.

[0026] Appendix 1: Chemical composition of the boron-containing steel smelted by the present invention (m%)

[0027] Furnace number C Si Mn P S Al B [H] / ppm [O] / ppm [N] / ppm 0901 0.56 0.23 0.66 0.008 0.002 0.008 0.0017 1.0 18 58 0902 0.55 0.21 0.71 0.010 0.003 0.008 0.0016 1.2 16 60 1184 0.54 0.24 0.74 0.011 0.004 0.014 0.0017 0.90 15 55 1371 0.57 0.26 0.70 0.006 0.003 0.006 0.0018 0.85 13 54 1372 0.57 0.25 0.72 0.008 0.004 0.009 0.0017 0.88 15 53 1471 0.56 0.21 0.74 0.007 0.004 0.006 0.0015 0.96 16 51 1472 0.55 0.23 0.69 0.006 0.004 0.005 0.0015 1.05 15 59 1488 0.55 0.25 0.71 0.006 0.006 0.007 0.0017 1.02 14 60 1489 0.58 0.22 0.70 0.015 0.009 0.004 0.0016 1.06 18 54 1581 0.55 0.21 0.78 0.009 0.005 0.005 0.0013 0.99 16 52 1710 0.56 0.25 0.71 0.008 0.004 0.006 0.0016 1.00 15 60 1713 0.55 0.23 0.69 0.009 0.003 0.005 0.0016 1.10 17 58 1714 0.54 0.26 0.70 0.006 0.003 0.010 0.0020 1.08 18 57 1818 0.55 0.27 0.71 0.009 0.004 0.009 0.0015 0.98 16 56 1819 0.56 0.28 0.79 0.010 0.003 0.011 0.0017 0.96 15 53 average value 0.56 0.24 0.72 0.009 0.004 0.008 0.0016 0.85 13 58

[0028] Attached Table 2: Yield of Boron-Containing Steel Smelted by the Present Invention

[0029] Furnace number Boron iron addition amount / kg Molten steel volume / t Yield / % Consumption per ton of steel / kg 0901 12 62.0 64.2 0.19 0902 12 60.0 56.6 0.21 1184 14 64.0 56.6 0.22 1371 16 61.0 49.9 0.26 1372 20 65.0 40.0 0.31 1448 16 62.0 42.6 0.26 1449 14 60.0 46.5 0.23 1463 16 64.0 49.9 0.25 1464 14 60.0 48.8 0.24 1581 14 62.0 42.2 0.22 1710 15 65.0 50.4 0.23 1686 12 60.0 58.3 0.20 1687 14 60.2 62.7 0.23 1818 15 65.0 47.6 0.23 1819 14 63 55.8 0.22 average value 15 64 51.47 0.23 .

Claims

1. A smelting process for low-nitrogen, low-oxygen, boron-containing steel, characterized by: The low-nitrogen, low-oxygen, boron-containing steel comprises the following chemical components by weight percentage: C 0.50-0.60%, Si≤0.35%, Mn 0.60-0.90%, B 0.001-0.002%, Cr≤0.20%, Ni≤0.20%, Mo≤0.20%, Cu≤0.20%, P≤0.005%, S≤0.002%, and the balance is iron. The smelting process of the low-nitrogen, low-oxygen, boron-containing steel adopts an electric arc furnace to melt scrap steel, argon blowing and refining in a ladle, deoxidation and desulfurization, control of aluminum content, adjustment of boron content and temperature to meet requirements, hanging the ladle into a vacuum tank for further degassing and refining, and casting into a steel ingot. The smelting process specifically comprises the following steps: Step 1) Select the charge: Select the raw materials for electric arc furnace smelting according to weight percentage, including 50-70% high-quality carbon steel scrap, 20-40% pig iron or sponge iron, and 10-30% return steel carbon head. Do not add slag steel or miscellaneous scrap steel when batching. The first sample of electric arc furnace melt analysis shows that As, Sn, Pb, Sb, and Bi are all ≤0.010%. Step 2), the electric arc furnace starts to oxidize carbon ≥ 0.80%, the oxidation temperature ≥ 1550 ° C, and the decarburization amount ≥ 0.40%; the electric arc furnace tapping end point [C] ≥ 0.30%, [P] ≤ 0.003%, the temperature ≥ 1630 ° C, before the electric furnace tapping, add 2.0 kg / t of aluminum blocks to the ladle for precipitation deoxidation to quickly reduce the oxygen content in the steel, add 5.0 kg / t of high calcium lime as slag-making material to remove sulfur in the steel to the maximum extent, and the amount of steel left in the electric furnace is ≥ 5 tons to ensure that no slag is left when tapping to prevent phosphorus reversion of the molten steel; Step 3), after the refining bag is in place, connect the argon gas, add 1~2.0kg / t of calcium carbide, 1.0~2.0kg / t of carbon powder, and 1.0~2.0kg / t of ferrosilicon powder for diffusion deoxidation, send electrochemical slag, measure the temperature, take samples, adjust the chemical composition after the slag is white, and blow argon to feed the aluminum wire according to the residual aluminum; during the refining period, use 0.5~1.0kg / t of carbon powder, 0.5~1.0kg / t of ferrosilicon powder, and 0.5~1.0kg / t of calcium silicon powder in small batches or multiple batches for deoxidation and maintain a reducing atmosphere to ensure uniform composition and temperature; after fully stirring under the white slag, take the first sample for analysis and analyze the N content at the same time. In order to enhance the desulfurization and deoxidation capacity of the reduced slag, the main components of the refined slag used according to the weight percentage regulations are: CaO 45~50%, SiO2 5.0~8.0%, MgO 3.0~5.0%, Fe2O3≤1.0%, Al2O3 40~45%, adjust the chemical composition of C, Si and Mn in the molten steel according to the analysis results of the first sample, and adjust the Al content in the molten steel by 0.015~0.030% according to the sample composition; Step 4), ferroboron is added before vacuum degassing treatment, and then ferroboron is added at a 100% recovery rate after power supply for 5 minutes, and the boron content is adjusted to 0.003%. When adding boron, the ferroboron is wrapped with iron sheet, and the wrapped ferroboron is tied to the iron rod with iron wire. The argon flow rate is adjusted to 120-150NL / min, and the slag surface is slightly blown open to leak molten steel. Then the ferroboron is quickly inserted into the molten steel for 10-20 seconds, and the iron rod is pulled out. It is weakly stirred for 3-5 minutes, and the temperature is 1640-1660℃ and the bag is hung into the vacuum tank for degassing; Step 5), the molten steel temperature is 1630-1650℃, and the steel enters the vacuum tank for exhaust. The vacuum degree is maintained below 67Pa for ≥15 minutes. After VD, hydrogen and oxygen are determined online to control [H]≤0.8ppm and [O]≤5.0ppm. A glass tube sample is taken to analyze the nitrogen content and control [N]≤40ppm. The residual [Al] is controlled at 0.010-0.020%. When the residual [Al] is lower than the required value, an Al wire should be fed. Argon is blown and weakly stirred for ≥10 minutes before tapping. Steel is poured directly after VD. The ladle temperature is 1530-1540℃. The molten steel must not be exposed during soft argon blowing, and a large amount of argon should not be used for stirring and cooling. When the temperature is appropriate, the steel can be tapped for pouring. Step 6) It is preferred to use an ingot mold with good inner wall quality and clean it. The ingot mold used must be a tooling with a smooth inner wall, no cracks, and no pits, and it must be cleaned and dusted thoroughly. The ingot mold used must be preheated before sitting or a continuous ingot mold must be used. The mold temperature must be ≥30°C. After the ingot mold is seated, the protective slag is hung and the mold mouth is covered with a protective cover to prevent ash, dust and steel flowers from falling into the mold. Step 7) After the calming is completed, drain the outside of the injection pipe to let the drainage sand and low-temperature sand-containing molten steel flow out, control the flushing flow rate to 120-200kg, and then quickly flush the low-temperature steel in the nozzle to preheat the upper and lower slides, and then quickly direct the car, after the injection pipe is aligned, open the nozzle 60-80%, let the molten steel quickly fill the soup channel, exhaust the gas in the soup channel, so that the molten steel does not gushing and splashing; Step 8) When the molten steel enters the mold after pouring, follow the flow in time to fill the ingot tail ball to form a molten pool, reduce eddy circulation, and maintain a steady rise; when the molten steel in the ingot body is 50 to 80 mm away from the cap mouth line, the flow must be reduced to allow the molten steel to steadily enter the cap mouth. If the ingot body injection speed is still maintained, a mixture of steel slag will quickly form at the chamfer of the ingot body and the cap mouth, causing splashing, resulting in various quality defects at the head of the ingot; after the molten steel is capped, mid-flow filling begins, and the argon flow rate is reduced as required, while the injection flow is gradually reduced. When it reaches 2 / 3 of the cap mouth line, 1 to 3 kg of heating agent is added. At this time, a trickle filling is started, and the pouring height is specified, and the nozzle is closed; after the pouring is completed, carbonized rice husks are added to further maintain the riser shrinkage compensation effect.

2. The smelting process of a low-nitrogen, low-oxygen, boron-containing steel according to claim 1, characterized in that: The low-nitrogen, low-oxygen, boron-containing steel preferably includes the following chemical composition in terms of weight percentage: C 0.52-0.58%, Si 0.15-0.35%, Mn 0.70-0.90%, B 0.001-0.002%, Cr≤0.20%, Ni≤0.20%, Mo ≤0.10%, Cu≤0.10%, P≤0.005%, S≤0.002%, Al≤0.020%, the sum of the five harmful elements As+Sn+Pb+Sb+Bi≤0.025%, and the balance being iron.