A smelting method for improving castability of high-aluminum generator claw pole steel

Abstract

The present invention relates to a smelting method for improving castability of high-aluminum generator claw pole steel. The chemical composition of the material is calculated by weight percentage as follows: [C]: 0.05-0.08%, [Si]: 0.05-0.10%, [Mn]: 0.25-0.40%, [P]≤0.025%, [S]: 0.015-0.025%, [Cr]: 0.05-0.10%, [Ni]: 0-0.10%, [Cu]: 0-0.10%, [Al]: 0.030-0.060%, [B]: 0.0020-0.0040%, and the rest is Fe. The claw pole steel is low-silicon, low-carbon, high-sulfur, and high-aluminum steel. During casting, problems such as nozzle nodules and stopper rod rising leading to pouring interruption are easily encountered. The present invention can improve the cleanliness of molten steel and ensure castability by designing a reasonable smelting process.

Description

Technical Field

[0001] The invention relates to a method for smelting high-aluminum generator claw pole steel, belonging to the technical field of metallurgy. Background Art

[0002] With the rapid development of the automobile and engineering machinery industries, the degree of electrification and automation is getting higher and higher, and higher requirements are also placed on the power generation performance of generators. As the power core of the generator, the claw pole's composition, structure, magnetic properties and processing technology will directly affect the generator's power generation performance, among which the magnetic property is the key indicator of the claw pole steel performance. In order to ensure that the claw pole steel has higher electromagnetic properties, the carbon content and silicon content of the steel are required to be lower. In order to inhibit the aging of low-carbon steel and improve the toughness, wear resistance and fatigue resistance of steel at low temperatures, the steel is required to contain a certain amount of aluminum. At the same time, in order to improve the processing performance of steel, the steel is required to contain a certain amount of S. The chemical composition of the claw pole steel produced by a certain company is calculated by weight percentage as follows: [C]: 0.05~0.08%, [Si]: 0.05~0.10%, [Mn]: 0.25~0.40%, [P]≤0.020%, [S]: 0.015~0.025%, [Cr]: 0.05~0.10%, [Ni]: 0~0.10%, [Cu]: 0~0.10%, [Al]: 0.030~0.060%, [B]: 0.0020~0.0040%, and the rest is Fe. It is a low-silicon, low-carbon, high-sulfur, and high-aluminum steel. In order to ensure that the aluminum and silicon contents of the molten steel meet the standards, this type of steel generally only uses aluminum deoxidation, resulting in a high Al2O3 content in the molten steel. Although soft stirring is used in the refining process to remove a portion of it, some Al2O3 still remains in the molten steel. In addition, due to the high oxygen content in the tundish in the second pouring furnace, the aluminum in the molten steel is easily secondary oxidized, further generating Al2O3, resulting in nozzle nodules during casting and problems such as interruption of casting caused by rising stopper rods. CN202011367313.2 A boron-containing steel for motor claw poles and its low-cost smelting process [C]: 0-0.05%, [Si]: 0.02-0.08%, [Mn]: 0.25-0.35%, [P]≤0.025%, [S]: 0.004-0.015%, [Cr]≤0.05%, [Ni]≤0.05%, [Cu]≤0.05%, [Al]: 0.010-0.025%, [B]: 0.0010-0.0060%, the rest is Fe and unavoidable impurities, the S content is required to be 0.004-0.015%, and the aluminum content is 0.010-0.025%. The higher the sulfur content and aluminum content in the molten steel, the easier it is to generate CaS and Al2O3, which are sensitive substances for nodules. However, the claw pole steel produced by the present invention has a high aluminum content and a sulfur content within a certain range, which is more prone to nodulation during casting than the above-mentioned steel. Therefore, the above-mentioned method cannot avoid the accident of nodulation and interruption of casting of the present invention.

[0003] How to solve the casting nodules of high-aluminum (Al≥0.03%) generator claw pole steel and ensure the castability of molten steel is the main technical problem to be solved by the present invention. Summary of the invention

[0004] In order to solve the problems in the background technology, the present invention provides a method for smelting high-aluminum generator claw pole steel. Under the condition of ensuring that the silicon content of molten steel does not exceed the process requirements, silicon manganese deoxidation is used as much as possible to reduce the generation of Al2O3 in the smelting process, and argon protection is required to be flushed into the tundish before casting to reduce the oxygen concentration in the tundish, reduce the secondary oxidation of molten steel, improve the cleanliness of molten steel, ensure castability, and shorten the refining soft blowing time and reduce the amount of calcium wire, improve production efficiency and reduce steelmaking costs. At the same time, by optimizing the structure of steel materials, adding part of pig iron to control the sulfur content of the converter end point to 0.025-0.035%, refining and making low-basicity slag with weak stirring, reducing molten steel desulfurization, and canceling the use of sulfide wire, further reducing molten steel pollution.

[0005] The specific method steps and control method parameters are as follows:

[0006] The chemical composition of the high-aluminum generator claw pole steel is calculated by weight percentage as follows: [C]: 0.05-0.08%, [Si]: 0.05-0.10%, [Mn]: 0.25-0.40%, [P] ≤ 0.025%, [S]: 0.015-0.025%, [Cr]: 0.05-0.10%, [Ni]: 0-0.10%, [Cu]: 0-0.10%, [Al]: 0.030-0.060%, [B]: 0.0020-0.0040%, and the rest is Fe.

[0007] The process flow of high-aluminum generator claw pole steel is: converter smelting → steel tapping → LF refining → continuous casting, which specifically includes the following steps:

[0008] Step 1, converter smelting, the converter steelmaking raw materials are scrap steel, molten iron and pig iron, the scrap steel accounts for 15-20% of the total mass of the steelmaking raw materials, the pig iron accounts for 5-10% of the total raw materials, the molten iron accounts for 70-80% of the total mass of the steelmaking raw materials, the carbon content of the steel is ≤0.05%, the phosphorus content of the steel is ≤0.025%, the sulfur content of the steel is 0.025-0.035%, and the steel tapping temperature is 1620-1650°C.

[0009] Further, preferably, in the step 1, the components of the pig iron are as follows by weight: C: 4.2-4.8%, Si: 0.2-0.8%, Mn: 0.1-0.5%, P: 0.08-0.15%, S: 0.025-0.05%, and the rest is iron.

[0010] Adding a portion of pig iron to the converter can meet the sulfur content requirements of the steel. At the same time, the refining process produces low-basicity slag, and with weak stirring, it reduces the desulfurization of molten steel. The sulfur content requirements of molten steel can be met without adding sulfide iron wire, avoiding the pollution of molten steel caused by the additional addition of sulfide iron wire;

[0011] Step 2: Steel tapping: Add 4.5-8.0kg / t silicon manganese, 0.45-0.75kg / t low carbon ferrochrome, 3.0-5.0kg slag remover and 0-0.3kg / t aluminum block in sequence for 1 / 3 of the steel tapping. At the end of steel tapping, use slag stopper + slide plate double-gear operation, and the slag amount is ≤3kg / t; use large flow stirring.

[0012] Furthermore, preferably, in the step 2, the composition of silicon manganese is Mn ≥ 55.0%, C ≤ 2.0%, Si ≥ 20.0%, and the rest is iron; the composition of the slag-forming agent is: CaO: 50-60%, SiO2: 20-30%, Al2O3: 20-30%, and some inevitable impurities; the composition of the slag is CaO: 40-50%, MgO: 4-6%, SiO2: 15-25%, FeO: 2-5%, MnO: 3-5%, Al2O3: 10-25%, and some inevitable impurities, and the slag basicity is controlled at 2.0-3.0; the bottom blowing argon flow rate is controlled at 2.0-4.0 L / min / t.

[0013] The use of silicon manganese for deoxidation and a slag basicity of 2.0 to 3.0 can ensure that the oxygen content of the molten steel is ≤30ppm and the silicon content of the molten steel is ≤0.1%, reducing the generation of Al2O3 and CaS at the same time.

[0014] Step three, LF furnace smelting, using calcium carbide and aluminum particles for deoxidation, calcium carbide dosage: 1.0-2.0kg / t, aluminum particle dosage: 0.5-1.0kg / t; feeding aluminum wire as the first step in the refining station, the target aluminum content of the molten steel is controlled at 0.035-0.045%, 0.10-0.15kg / t of ferroboron is added 5-10min after the aluminum wire is fed and the composition is fine-tuned to ensure that the composition of the molten steel meets the requirements, and small flow stirring is adopted in the refining process; after the refined molten steel composition is qualified, 30-100m calcium wire is added, and then soft stirring operation is performed, and the soft stirring time is 5.0-10.0min.

[0015] Further, as a preference, in the step 3, the bottom blowing argon flow rate during the refining process is controlled at 1.0-2.0 L / min / t by stirring with a small flow rate; the bottom blowing argon flow rate during soft stirring is controlled at 0.5-1.0 L / min / t. The slag composition after the refining furnace treatment is CaO: 46-58%, MgO: 3-8%, SiO2: 7-12%, Al2O3: 20-35%, and some inevitable impurities, and the slag basicity is controlled at 4.0-6.0.

[0016] Step 4, continuous casting. The continuous casting process uses a 220mm×260mm cross-section for production, and adopts full-process protection casting. The continuous casting tundish uses an integral smear plug rod tundish, which is baked to 1050-1150°C. After the tundish is baked, it is flushed with argon for protection. The superheat of the first tundish is controlled at 40-50°C, the superheat of the continuous casting furnace is controlled at 25-35°C, and the pulling speed is controlled at 0.90-1.0m / min; the crystallizer adopts electromagnetic stirring and non-sinusoidal vibration mode, the electromagnetic stirring current of the crystallizer is 120-180A, and the frequency is 2.2-2.8Hz; the amplitude of the crystallizer is controlled at -2.5-2.5mm, and the frequency is controlled at 130+40V opm (V represents the pulling speed, and opm is the unit of vibration frequency); the secondary cooling adopts mist cooling and weak cooling water distribution.

[0017] Furthermore, preferably, in step 4, the continuous casting tundish is protected by argon flushing, the argon flushing time is ≥10 min, and the oxygen content is measured by an oxygen meter before pouring, and the oxygen concentration is required to be ≤1%.

[0018] Before pouring, argon is passed into the ladle to reduce the oxygen partial pressure. The oxygen concentration is required to be ≤1.0%. This can significantly reduce the secondary oxidation of Al in the molten steel, thereby ensuring smooth casting.

[0019] The beneficial effects of the present invention are:

[0020] 1. Under the condition that the silicon content of molten steel does not exceed the process upper limit, a progressive deoxidation method is adopted. First, silicon-manganese alloy is used for shallow deoxidation, and a certain slag basicity is used to remove the oxygen content of the molten steel to below 30ppm, and then aluminum blocks are used for deep deoxidation. The amount of silicon-manganese is clarified, which can greatly reduce the generation of Al2O3 and the risk of water plugging during the casting process. It can also shorten the refining soft stirring time and the amount of calcium wire used, while reducing the generation of CaS.

[0021] 2. Silicon manganese is used for deoxidation during the steel-making process, and slag-forming agents are used to make slag. No lime is added during steel-making, and the slag basicity is controlled at 2.0-3.0. At the same time, the bottom blowing argon flow rate is reduced during the refining process to weaken the slag-metal reaction, which can greatly reduce the desulfurization reaction and ensure that the sulfur content of the molten steel is within the process range (the sulfur content of the converter steel-making can meet the steel grade requirements). There is no need to add sulfur-containing alloys such as sulfur wire, which further ensures the cleanliness of the molten steel.

[0022] 3. Before casting, the baked tundish is protected by argon gas, and the oxygen concentration in the sealed tundish is ensured to be less than 1% to reduce the secondary oxidation of the first furnace steel. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The casting curve diagram of Example 1 when the number of continuous casting furnaces is 8.

[0024] Figure 2The casting curve diagram of Example 2 when the number of continuous casting furnaces is 8 furnaces.

[0025] Figure 3 Casting curve diagram of Comparative Example 1. DETAILED DESCRIPTION

[0026] Embodiment 1:

[0027] 1. Converter smelting uses 115t molten iron + 22t scrap steel + 10t pig iron as raw materials for smelting. The phosphorus content of the converter steel is 0.015%, the carbon content of the steel is 0.04%, the sulfur content of the steel is 0.028%, and the steel tapping temperature is 1630℃.

[0028] 2. Steel tapping: 675kg silicon manganese, 75kg low-carbon ferrochrome and 550kg slag reducing agent are added in sequence for 1 / 3 of the steel. At the end of steel tapping, slag plug + slide plate double-gear operation is adopted, and the slag discharge amount is about 280kg. The bottom blowing flow rate during steel tapping is controlled at 500L / min. The slag composition at the end of steel tapping is CaO: 46.2%, MgO: 5.3, SiO2: 22.5%, FeO: 4.1%, MnO: 4.3%, Al2O3: 17.1%, as well as inevitable impurities, and the slag basicity is 2.1.

[0029] 3. LF furnace smelting: after refining to the station, bottom blowing and stirring are started, and the bottom blowing flow rate is controlled at 140L / min (steel output is 135t, 1.04L / min / t), and temperature, oxygen content and sampling are performed. The molten steel temperature is 1570℃, and the oxygen content of the molten steel is 25ppm. The composition of the molten steel at the station is: [C] 0.045%, [Si] 0.08%, [Mn] 0.35%, [P] ≤ 0.016%, [S] 0.026%, [Cr] 0.06%, [Ni] 0.03%, [Cu] 0.03%, [Al] 0.003%; 180kg calcium carbide and 80kg aluminum granules are added, and 300m aluminum wire is fed. After 5 minutes, 1 8kg of ferroboron; the second sampling and testing of the composition, the composition of the molten steel is [C] 0.055%, [Si] 0.08%, [Mn] 0.35%, [P] ≤ 0.016%, [S] 0.023%, [Cr] 0.06%, [Ni] 0.03%, [Cu] 0.03%, [Al] 0.038%, [B] 0.003%; the slag sample analysis composition is: CaO: 50.3%, MgO: 6.5, SiO2: 11.2%, Al2O3: 29.1%, and some inevitable impurities, slag basicity: 4.5; 60m of calcium wire was added, followed by soft stirring operation, and the soft stirring time was 7.5min.

[0030] 4. Continuous casting: The continuous casting process uses a 220mm×260mm cross-section for production, and adopts full-process protection casting. The continuous casting tundish uses an integral smear plug tundish, which is baked to 1120°C. After the tundish is baked, it is flushed with argon for protection. The argon flushing time is 12 minutes. The oxygen concentration measured by the oxygen meter is 0.5%. The superheat of the first ladle is 50°C, the superheat of the continuous casting furnace is 28°C, and the pulling speed is controlled at 0.95m / min; the crystallizer adopts electromagnetic stirring and non-sinusoidal vibration mode, the crystallizer electromagnetic stirring current is 150A, and the frequency is 2.5Hz; the crystallizer amplitude is controlled at -2.5~2.5mm, and the frequency is controlled at 130+40V opm; the secondary cooling adopts mist cooling, the specific water volume is 0.3L / kg, and the distribution ratio of each section of the secondary cooling is 44:33:23.

[0031] Figure 1 This is the casting curve of Example 1. The number of continuous casting furnaces is 8. The continuous casting process uses two tundishes for simultaneous casting. Each tundish controls 4 streams, for a total of 8 streams. It can be seen that the continuous casting curve is stable, which does not mean a maximum of 8 continuous casting furnaces. The actual production can reach 15 furnaces or more.

[0032] Embodiment 2:

[0033] 1. Converter smelting uses 110t molten iron + 27t scrap steel + 11t pig iron as raw materials for smelting. The phosphorus content of the converter steel is 0.013%, the carbon content of the steel is 0.045%, the sulfur content of the steel is 0.032%, and the steel tapping temperature is 1628℃.

[0034] 2. Steel tapping: 685kg of silicon manganese, 80kg of low-carbon ferrochrome, 550kg of slag-removing agent and 30kg of aluminum block are added in sequence for 1 / 3 of the steel. At the end of steel tapping, slag plug + slide plate double-gear operation is adopted, and the slag discharge amount is about 270kg. The bottom blowing flow rate during steel tapping is controlled at 500L / min. The slag composition at the end of steel tapping is CaO: 47.8%, MgO: 5.2, SiO2: 18.6%, FeO: 2.3%, MnO: 3.1%, Al2O3: 21.3%, and some inevitable impurities. The slag basicity is 2.6.

[0035] 3. LF furnace smelting, after refining to the station, start bottom blowing and stirring, the bottom blowing flow rate is controlled at 140L / min, and the temperature, oxygen content and sampling are measured. The molten steel temperature is 1565℃, the molten steel oxygen content is 20ppm, and the molten steel composition at the station is: [C] 0.052%, [Si] 0.082%, [Mn] 0.34%, [P] ≤ 0.015%, [S] 0.025%, [Cr] 0.06%, [Ni] 0.03%, [Cu] 0.03%, [Al] 0.005%; add 170kg calcium carbide and 90kg aluminum particles, and feed 320m aluminum wire. After 5 minutes, add 20kg boron Iron; the second sampling and testing of the composition, the molten steel composition is [C] 0.065%, [Si] 0.083%, [Mn] 0.34%, [P] ≤ 0.015%, [S] 0.022%, [Cr] 0.06%, [Ni] 0.03%, [Cu] 0.03%, [Al] 0.040%, [B] 0.003%; the slag sample analysis composition is: CaO: 53.6%, MgO: 6.2, SiO2: 9.6%, Al2O3: 30.6%, slag basicity 5.6; 80m calcium wire was added, followed by soft stirring operation, and the soft stirring time was 8.5min.

[0036] 4. Continuous casting: The continuous casting process uses a 220mm×260mm cross-section for production, and adopts full-process protection casting. The continuous casting tundish uses an integral smear plug tundish, which is baked to 1120°C. After the tundish is baked, it is flushed with argon for protection. The argon flushing time is 15 minutes. The oxygen concentration measured by the oxygen meter is 0.4%. The overheat of the first ladle is 47°C, the overheat of the continuous casting furnace is 25°C, and the pulling speed is controlled at 0.95m / min. The crystallizer adopts electromagnetic stirring and non-sinusoidal vibration mode. The electromagnetic stirring current of the crystallizer is 150A and the frequency is 2.5Hz. The amplitude of the crystallizer is controlled at -2.5~2.5mm, and the frequency is controlled at 130+40V opm. The secondary cooling adopts mist cooling, the specific water volume is 0.3L / kg, and the distribution ratio of each section of the secondary cooling is 44:33:23.

[0037] Figure 2 This is the casting curve of Example 2. The number of continuous casting furnaces is 8. The continuous casting process uses two tundishes for simultaneous casting. Each tundish controls 4 streams, for a total of 8 streams. It can be seen that the continuous casting curve is stable, which does not mean a maximum of 8 continuous casting furnaces. The actual production can reach 15 furnaces or more.

[0038] Comparative Example 1:

[0039] 1. Converter smelting uses 115t molten iron + 32t scrap steel as raw materials. The phosphorus content of converter steel is 0.015%, the carbon content of steel is 0.042%, the sulfur content of steel is 0.022%, and the tapping temperature is 1635℃.

[0040] 2. Steel tapping: 1 / 3 of the steel is tapped in order: 150kg of aluminum block, 75kg of low-carbon ferrochrome, 500kg of lime, and 200kg of slag-removing agent. At the end of steel tapping, slag plug + slide plate double-gear operation is adopted, and the slag discharge amount is about 300kg. The bottom blowing flow rate during the steel tapping process is controlled at 450L / min. The slag composition at the end of steel tapping is CaO: 53.6%, MgO: 5.0, SiO2: 8.2%, FeO: 1.2%, MnO: 3.1%, Al2O3: 25.6%, and some inevitable impurities. The slag basicity is 6.5.

[0041] 3. LF furnace smelting, after refining to the station, start bottom blowing and stirring, the bottom blowing flow rate is controlled at 420L / min, and temperature, oxygen determination and sampling are performed. The molten steel temperature is 1575℃, the molten steel oxygen content is 12ppm, and the molten steel composition at the station is: [C] 0.047%, [Si] 0.005%, [Mn] 0.35%, [P] ≤ 0.016%, [S] 0.003%, [Cr] 0.06%, [Ni] 0.03%, [Cu] 0.03%, [Al] 0.012%; add 150kg calcium carbide, 100kg aluminum granules and 100kg ferrosilicon, and feed 250m aluminum wire. After 5 minutes, add 20kg ferroboron and 150m ferrosulphide wire. 0m; the second sampling and testing of the composition, the molten steel composition is [C] 0.059%, [Si] 0.062%, [Mn] 0.35%, [P] ≤ 0.016%, [S] 0.019%, [Cr] 0.06%, [Ni] 0.03%, [Cu] 0.03%, [Al] 0.044%, [B] 0.003%; the slag sample analysis composition is: CaO: 50.6%, MgO: 4.5, SiO2: 5.9%, Al2O3: 37.2%, and some inevitable impurities, the slag basicity is 8.6; 420m calcium wire is added, and then soft stirring operation is carried out, and the soft stirring time is 20.6min.

[0042] 4. Continuous casting: The continuous casting process uses a 220mm×260mm cross-section production, adopts full-process protection casting, and the continuous casting tundish uses an integral coating plug tundish. The tundish is baked to 1120℃, the superheat of the first tundish is 48℃, the superheat of the continuous casting furnace is 22℃, and the pulling speed is controlled at 0.95m / min; the crystallizer adopts electromagnetic stirring and non-sinusoidal vibration mode, the crystallizer electromagnetic stirring current is 150A, and the frequency is 2.5Hz; the crystallizer amplitude is controlled at -2.5~2.5mm, and the frequency is controlled at 130+40V opm; the secondary cooling adopts mist cooling, the specific water volume is 0.35L / kg, and the distribution ratio of each section of the secondary cooling is 40:35:25.

[0043] Comparative Example 1 and the traditional process use aluminum for deoxidation, and the oxidation product produced is basically Al2O3, with basically no SiO2, and the basicity is generally above 5.0, and the slag basicity cannot be controlled at 2.0-3.0. The casting curve fluctuates greatly and cannot achieve the stable curve of the present invention.

[0044] Figure 3 This is the conventional continuous casting casting curve of Comparative Example 1. The casting curve fluctuates greatly and the 5-8th stream is interrupted in the first furnace due to the blocking of the water outlet. The remaining 1-4 streams are cast for a total of 5 furnaces.

[0045] Comparative Example 2

[0046] 1. Converter smelting uses 115t molten iron + 22t scrap steel + 10t pig iron as raw materials for smelting. The phosphorus content of the converter steel is 0.015%, the carbon content of the steel is 0.04%, the sulfur content of the steel is 0.028%, and the steel tapping temperature is 1630℃.

[0047] 2. Steel tapping: 675kg silicon manganese, 75kg low-carbon ferrochrome and 350kg slag reducing agent are added in sequence for 1 / 3 of the steel. At the end of steel tapping, slag plug + slide plate double-gear operation is adopted, and the slag discharge amount is about 280kg. The bottom blowing flow rate during steel tapping is controlled at 500L / min. The slag composition at the end of steel tapping is CaO: 32.8%, MgO: 5.3, SiO2: 27.3%, FeO: 5.7%, MnO: 4.7%, Al2O3: 20.3%, and some inevitable impurities. The slag basicity is 1.2.

[0048] 3. LF furnace smelting, after refining to the station, start bottom blowing and stirring, the bottom blowing flow rate is controlled at 140L / min, and temperature, oxygen determination and sampling are performed. The molten steel temperature is 1570℃, the molten steel oxygen content is 98ppm, and the molten steel composition at the station is: [C] 0.045%, [Si] 0.08%, [Mn] 0.35%, [P] ≤ 0.016%, [S] 0.013%, [Cr] 0.06%, [Ni] 0.03%, [Cu] 0.03%, [Al] 0.0001%; ​​add 180kg calcium carbide, 150kg aluminum particles and 200kg lime, and feed 400m aluminum wire. After 5 minutes, add 18kg ferroboron; The composition of the molten steel was [C] 0.055%, [Si] 0.08%, [Mn] 0.35%, [P] ≤ 0.016%, [S] 0.023%, [Cr] 0.06%, [Ni] 0.03%, [Cu] 0.03%, [Al] 0.038%, and [B] 0.003% after secondary sampling and analysis. The composition of the slag sample was CaO: 51.3%, MgO: 6.7, SiO2: 12.2%, Al2O3: 28.6%, and some inevitable impurities. The slag basicity was 4.2. 150m calcium wire was added, followed by soft stirring operation for 15.0min.

[0049] Compared with Example 1, Comparative Example 2 has the same deoxidation method, but the slag basicity is not controlled between 2.0 and 3.0. The basicity of Comparative Example 2 is lower than 2.0, the oxygen content of the molten steel is relatively high, more aluminum is added for deoxidation, a larger amount of calcium is fed, the soft stirring time is longer, and the cost is high.

[0050] If only the basicity is controlled below 2.0, while other conditions such as the amount of aluminum, the amount of calcium, and soft stirring are the same as in Example 1, the castability is poor, the number of continuous casting furnaces decreases, and the number of continuous casting furnaces is less than 8 furnaces.

[0051] Comparative Example 3

[0052] 1. Converter smelting uses 115t molten iron + 22t scrap steel + 10t pig iron as raw materials for smelting. The phosphorus content of the converter steel is 0.015%, the carbon content of the steel is 0.04%, the sulfur content of the steel is 0.028%, and the steel tapping temperature is 1630℃.

[0053] 2. Steel tapping: 675kg silicon manganese, 75kg low-carbon ferrochrome, 550kg slag reducing agent and 200kg lime are added in sequence for 1 / 3 of the steel tapping. At the end of steel tapping, slag plug + slide plate double-gear operation is adopted, and the slag discharge amount is about 280kg. The bottom blowing flow rate during steel tapping is controlled at 500L / min. The slag composition at the end of steel tapping is CaO: 46.2%, MgO: 5.3, SiO2: 22.5%, FeO: 3.8%, MnO: 4.7%, Al2O3: 17.1%, and the slag basicity is 3.7.

[0054] 3. LF furnace smelting, after refining to the station, start bottom blowing and stirring, the bottom blowing flow rate is controlled at 140L / min, and temperature, oxygen determination and sampling are performed. The molten steel temperature is 1570℃, the molten steel oxygen content is 22ppm, and the molten steel composition at the station is: [C] 0.045%, [Si] 0.08%, [Mn] 0.35%, [P] ≤ 0.016%, [S] 0.011%, [Cr] 0.06%, [Ni] 0.03%, [Cu] 0.03%, [Al] 0.003%; add 180kg calcium carbide and 80kg aluminum particles, and feed 300m aluminum wire and 120m pyrite wire. After 5 minutes, add 18kg ferroboron; the second The samples were taken and the composition was tested. The composition of the molten steel was [C] 0.055%, [Si] 0.08%, [Mn] 0.35%, [P] ≤ 0.016%, [S] 0.023%, [Cr] 0.06%, [Ni] 0.03%, [Cu] 0.03%, [Al] 0.038%, [B] 0.003%; the slag sample was taken for analysis and the composition was: CaO: 52.9%, MgO: 6.4, SiO2: 10.2%, Al2O3: 28.9%, and some inevitable impurities, slag basicity: 5.2; 120m calcium wire was added, and then soft stirring operation was carried out, and the soft stirring time was 17.0min.

[0055] Compared with Example 1, Comparative Example 3 has the same deoxidation method, and the main difference is that the slag basicity is not controlled between 2.0 and 3.0. The basicity of Comparative Example 3 is higher than 3.0. If the basicity is too high, more molten steel will be desulfurized, and a sulfur replenishment line will be required, which will lead to an increase in calcium treatment volume, extended soft blowing time, high cost, and poor castability of the molten steel.

[0056] Comparative Example 4

[0057] 1. Converter smelting uses 115t molten iron + 22t scrap steel + 10t pig iron as raw materials for smelting. The phosphorus content of the converter steel is 0.015%, the carbon content of the steel is 0.04%, the sulfur content of the steel is 0.028%, and the steel tapping temperature is 1630℃.

[0058] 2. Steel tapping: 400kg silicon manganese, 75kg low-carbon ferrochrome and 460kg slag reducing agent are added in sequence for 1 / 3 of the steel tapping. At the end of steel tapping, slag plug + slide plate double-gear operation is adopted, and the slag discharge amount is about 280kg. The bottom blowing flow rate during steel tapping is controlled at 500L / min. The slag composition at the end of steel tapping is CaO: 46.2%, MgO: 5.3, SiO2: 22.5%, FeO: 4.2%, MnO: 4.7%, Al2O3: 17.1%, and some inevitable impurities. The slag basicity is 2.1.

[0059] 3. LF furnace smelting, after refining to the station, start bottom blowing and stirring, bottom blowing flow rate is controlled at 140L / min, and temperature, oxygen determination and sampling are performed. The molten steel temperature is 1570℃, and the oxygen content of the molten steel is 105ppm. The composition of the molten steel at the station is: [C] 0.045%, [Si] 0.02%, [Mn] 0.34%, [P] ≤ 0.015%, [S] 0.027%, [Cr] 0.06%, [Ni] 0.03%, [Cu] 0.03%, [Al] 0.003%; add 180kg of calcium carbide and 160kg of aluminum particles, and feed 420m of aluminum wire. After 5 minutes, add 18kg of ferroboron; take samples for the second time and The chemical composition of the molten steel was [C] 0.055%, [Si] 0.08%, [Mn] 0.35%, [P] ≤ 0.016%, [S] 0.024%, [Cr] 0.06%, [Ni] 0.03%, [Cu] 0.03%, [Al] 0.038%, and [B] 0.003%. The slag sample was analyzed and the composition was: CaO: 51.3%, MgO: 6.7, SiO2: 12.2%, Al2O3: 28.6%, and some inevitable impurities. The slag basicity was 4.2. 150m calcium wire was added, followed by soft stirring operation for 15.0min.

[0060] Compared with Example 1, Comparative Example 4 uses silicon manganese for deoxidation, but the deoxidation effect cannot be guaranteed, and the amount of aluminum needs to be increased, which further leads to an increase in the amount of calcium treatment and the soft blowing time, which greatly increases the cost. In addition, its castability is poor, and the number of continuous casting furnaces decreases, and the number of continuous casting furnaces is less than 8 furnaces.

[0061] Comparative Example 5

[0062] 1. Converter smelting uses 115t molten iron + 22t scrap steel + 10t pig iron as raw materials for smelting. The phosphorus content of the converter steel is 0.015%, the carbon content of the steel is 0.04%, the sulfur content of the steel is 0.028%, and the steel tapping temperature is 1630℃.

[0063] 2. Steel tapping: 1200kg silicon manganese and 650kg slag reducing agent are added in sequence for 1 / 3 of the steel. At the end of steel tapping, slag plug + slide plate are used for double-gear operation, and the slag discharge amount is about 280kg. The bottom blowing flow rate during steel tapping is controlled at 500L / min. The slag composition at the end of steel tapping is CaO: 47.2%, MgO: 5.3, SiO2: 21.5%, FeO: 3.5%, MnO: 3.3%, Al2O3: 16.2%, and some inevitable impurities. The slag basicity is 2.2.

[0064] 3. LF furnace smelting, after refining to the station, bottom blowing and stirring are turned on, the bottom blowing flow rate is controlled at 140L / min, and temperature, oxygen determination and sampling are performed. The molten steel temperature is 1570℃, the molten steel oxygen content is 21ppm, and the molten steel composition at the station is: [C] 0.045%, [Si] 0.12%, [Mn] 0.43%, [P] ≤ 0.016%, [S] 0.025%, [Al] 0.003%. Comparative Example 5 Compared with Example 1, silicon manganese deoxidation is adopted. If the amount of silicon manganese is too large, the silicon content of the molten steel will exceed the requirements of the steel grade. This test is difficult to carry out on the claw pole steel grade involved in the present invention, and the elements are difficult to control within the required range. Therefore, the scheme of Comparative Example 5 is tested on 70 steel grades. The results show that when the amount of silicon manganese is too large, the silicon content of the molten steel exceeds the standard and the manganese content of the molten steel also exceeds the standard, and the requirements cannot be met.

[0065] Comparative Example 6

[0066] Comparative Example 6 is compared with Example 1, in which the oxygen concentration in the tundish is not controlled to be ≤1.0%. The aluminum in the molten steel will undergo secondary oxidation with the oxygen in the air in the tundish, regenerating Al2O3, which will cause the stopper rod to rise and the nozzle to be blocked. This experiment cannot be carried out.

[0067] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and concepts of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for smelting high-aluminum generator claw pole steel, characterized in that: The process flow is converter smelting-steel tapping-LF refining-continuous casting. The specific operation steps are: Step 1: converter smelting. The raw materials for converter steelmaking are scrap steel, molten iron and pig iron. The carbon content of the steel is ≤0.05%, the phosphorus content of the steel is ≤0.020%, the sulfur content of the steel is 0.025~0.035%, and the steel tapping temperature is 1620~1650℃; Step 2: steel tapping. During the steel tapping process, 4.5-8.0 kg / t of silicon manganese, 0.45-0.75 kg / t of low-carbon ferrochrome, 3.0-5.0 kg / t of slag remover, and 0-0.3 kg / t of aluminum block are added in sequence. At the end of steel tapping, a slag stopper + slide plate double-block operation is adopted. The slag discharge amount is ≤3.0 kg / t, and the slag basicity is controlled at 2.0-3.

0. A large flow rate is used for stirring. Step 3: LF furnace smelting, using calcium carbide and aluminum particles for combined deoxidation; feeding aluminum wire according to the refining station, the target aluminum content of molten steel is controlled at 0.035-0.045%, adding ferroboron after the aluminum wire is fed and fine-tuning the composition to ensure that the molten steel composition meets the requirements, and stirring with a small flow rate during the refining process; after the refining furnace treatment, the slag basicity is controlled at 4.0-6.0, and after the refined molten steel composition is qualified, 30-100m calcium wire is added, and then soft stirring operation is performed, and the soft stirring time is 5.0-10.0min; Step 4, continuous casting, using full-process protection casting, the continuous casting tundish uses an integral coating plug tundish, the tundish is baked to 1050~1150℃, and after the tundish is baked, it is flushed with argon protection. Before pouring, an oxygen meter is used to measure the oxygen content, and the oxygen concentration is required to be ≤1%. The superheat of the first furnace is controlled at 40~50℃, the superheat of the continuous casting furnace is controlled at 25~35℃, and the pulling speed is controlled at 0.90~1.0m / min; the crystallizer adopts electromagnetic stirring and non-sinusoidal vibration mode; the secondary cooling adopts mist cooling and weak cooling water distribution.

2. The smelting method of high-aluminum generator claw pole steel according to claim 1, characterized in that: In step 1, the composition of the pig iron is as follows by weight: C: 4.2%-4.8%, Si: 0.2%-0.8%, Mn: 0.1%-0.5%, P: 0.08%-0.15%, S: 0.025%-0.05%, and the rest is iron.

3. The smelting method of high aluminum generator claw pole steel according to claim 1, characterized in that: Scrap steel accounts for 15-20% of the total mass of the steelmaking raw materials, pig iron accounts for 5-10% of the total mass of the steelmaking raw materials, and molten iron accounts for 70-80% of the total mass of the steelmaking raw materials.

4. The smelting method of high aluminum generator claw pole steel according to claim 1, characterized in that: In step 2, the composition of silicon manganese is Mn ≥ 55.0%, C ≤ 2.0%, Si ≥ 20.0%, and the rest is iron; the composition of the slag-forming agent is: CaO: 50-60%, SiO2: 20-30%, Al2O3: 20-30%, and the rest are inevitable impurities; the composition of the slag is CaO: 40-50%, MgO: 4-6%, SiO2: 15-25%, FeO: 2-5%, MnO: 3-5%, Al2O3: 10-25%, and the rest are inevitable impurities; the bottom blowing argon flow rate is controlled at 2.0-4.0 L / min / t.

5. The smelting method of high-aluminum generator claw pole steel according to claim 1, characterized in that: In step three, the amount of calcium carbide is 1.0-2.0 kg / t, and the amount of aluminum particles is 0.5-1.0 kg / t; 0.10-0.15 kg / t of ferroboron is added 5-10 minutes after the aluminum wire is fed and the composition is fine-tuned.

6. The smelting method of high aluminum generator claw pole steel according to claim 1, characterized in that: In step three, the bottom blowing argon flow rate during the refining process adopts small flow stirring and is controlled at 1.0~2.0 L / min / t; the bottom blowing argon flow rate with soft stirring is controlled at 0.5~1.0 L / min / t. The slag composition after the refining furnace treatment is CaO: 46~58%, MgO: 3~8%, SiO2: 7~12%, Al2O3: 20~35%, and the rest are unavoidable impurities.

7. The smelting method of high aluminum generator claw pole steel according to claim 1, characterized in that: In step 4, the continuous casting tundish is protected by argon flushing, and the argon flushing time is ≥10min; the crystallizer electromagnetic stirring current is 120~180A, and the frequency is 2.2~2.8Hz; the crystallizer amplitude is controlled at -2.5~2.5mm.

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