CN106048392A - Method for producing semi-processed cold-rolled non-oriented electrical steel rotors and stators by thin slab continuous casting and rolling process - Google Patents

Abstract

A thin slab continuous casting and rolling process to produce a semi-process cold-rolled non-oriented electrical steel rotor and stator production method, comprising: step 1), molten iron pretreatment; step 2), converter smelting: scrap steel with a total weight of 12% is added to the converter, And fixed oxygen tapping; step 3), argon blowing: add composite deoxidizer when tapping the converter, and blow argon throughout the process of tapping the converter; step 4), RH refining: send molten steel into the vacuum RH refining furnace for smelting ; step 5), continuous casting; step 6), pickling and cold rolling: step 7), annealing: after cold rolling, annealing at 650-750°C for 8-12 hours; step 8), post-treatment. The motor rotor and stator made of cold-rolled semi-process cold-rolled non-oriented electrical steel of the present invention have good electromagnetic performance and process performance, and have lower processing performance compared with the motor rotor and stator made of cold-rolled common non-oriented electrical steel , electromagnetic performance, cost, and environmental protection advantages.

Description

A kind of thin slab continuous casting and rolling process to produce semi-process cold-rolled non-oriented electrical steel Sub, stator production method

technical field

The invention relates to a method for non-oriented electrical steel rotors and stators, in particular to a production method for semi-process cold-rolled non-oriented electrical steel rotors and stators produced by a thin slab continuous casting and rolling process.

Background technique

Due to its complex production process, high technical content, difficult production and large investment, cold-rolled electrical steel can be produced by a few domestic steel plants such as Wuhan Iron and Steel, Baosteel, Anshan Iron and Steel, and Taiyuan Iron and Steel. These manufacturers all use casting slabs of traditional thickness Production is carried out by traditional technology, but with the large-scale industrial application of continuous casting and rolling (CSP) technology, another brand-new technology has been opened up for the production of electrical steel. Preliminary results show that the use of CSP to produce medium and low-grade non-oriented electrical steel has obvious advantages in investment, cost and quality. With the implementation of the national sustainable development strategy, environmental protection and energy conservation are one of the key issues in the development of my country's iron and steel industry today. Important direction, using semi-process cold-rolled non-oriented electrical steel to replace hot-rolled electrical steel has significant advantages in energy saving, environmental protection and cost.

Contents of the invention

To sum up, it is necessary for the present invention to provide a semi-process cold-rolled non-oriented electrical steel rotor and stator production method produced by the thin slab continuous casting and rolling process.

A thin slab continuous casting and rolling process to produce semi-process cold-rolled non-oriented electrical steel rotor and stator production method, comprising:

Step 1), molten iron pretreatment;

Step 2), converter smelting: adding scrap steel with a total weight of 12% into the converter, and tapping with constant oxygen;

Step 3), blowing argon: adding a composite deoxidizer when tapping the converter, and blowing argon throughout the process of tapping the converter;

Step 4), RH refining: sending molten steel into a vacuum RH refining furnace for smelting;

Step 5), continuous casting: the molten steel is cast into a 55-70mm thick slab through a thin slab continuous casting machine, the casting speed of the continuous casting machine is 3.0-4.5m/min, the temperature of the continuous casting slab into the furnace is ≥850°C, and the heating section in the furnace The temperature is 1000-1150°C, the slab exit temperature is 980-1120°C, the finish rolling exit temperature is 860-920°C, the coiling temperature is 680-720°C, the F1 reduction rate is ≥50%, and the F1～F4 cumulative reduction Ratio ≥ 90%, F7 reduction rate 15.6%, rolled into hot-rolled sheet with a thickness of 2-3mm;

Step 6), pickling and cold rolling: After the temperature of the hot-rolled sheet is lower than 60°C, it is pickled with hydrochloric acid with a concentration of 30-150g/L, the temperature of the acid tank is 60-80°C, and the pickling time is 60-120 seconds, and the Impurities and iron oxide scales on the surface of the steel coil are then cold-rolled;

Step 7), annealing: annealing at 650-750°C for 8-12 hours after cold rolling;

Step 8), post-processing: the annealed steel coil is smoothed by 2-10% elongation, tensioned and divided into coils, and the divided steel coil is divided into strips on the slitting machine, and continuously punched on a high-speed punching machine. The punching speed is 150-500 times/min, and the rotors and stators for motors are produced. Put these rotors and stators into the continuous annealing furnace, and under the protective atmosphere of N ₂ or N ₂ +H ₂ , in the annealing furnace Complete annealing at 700-900°C, then slowly cool to about 500-520°C, pass in water vapor, keep for a period of time for bluing treatment, so that a dense oxide film is formed on the surface of the punched sheet as an insulating film, and then laminated Manufactured into rotors and stators for motors.

Wherein, the percentage of protective gas in this specification refers to the volume percentage of gas. The percentage of each element in molten steel refers to the mass percentage.

Wherein, the step 5) is specifically: the molten steel is cast into a 55-70mm thick slab through a thin slab continuous casting machine, the casting speed of the continuous casting machine is 3.0-4.5m/min, the furnace temperature of the continuous casting slab is ≥850°C, and the furnace The temperature in the inner heating section is 1000-1150°C, the slab exit temperature is 980-1120°C, the finish rolling exit temperature is 860-920°C, the coiling temperature is 680-720°C, F1 reduction rate ≥ 50%, F1～F4 Cumulative reduction rate ≥ 90%, F7 reduction rate 15.6%, rolled into a hot-rolled plate with a thickness of 2.5mm.

Wherein, the step 6) is specifically: after the temperature of the hot-rolled sheet is lower than 60°C, it is pickled with hydrochloric acid with a concentration of 30-150g/L, the temperature of the acid tank is 60-80°C, and the pickling time is 60-120 seconds, Remove impurities and iron oxide scales on the surface of the steel coil, and roll the pickled steel coil into a steel coil with a thickness of 0.50-0.55mm by a cold rolling tandem rolling mill.

Wherein, said step 8) is specifically: the steel coil after the annealing is processed through 2-10% elongation flattening, tension straightening and sub-coiling, the steel coil after the sub-coiling is divided into strips of different widths on the slitting machine, Continuous punching on the punching machine, the punching speed is 150-500 times/min, to produce loose pieces of rotors and stators for motors, put these rotors and stators into a continuous annealing furnace, and protect them under the protection of N ₂ or N ₂ +H ₂ Under the atmosphere, complete annealing in an annealing furnace at 700-900°C, then slowly cool to about 500-520°C, pass in water vapor, keep it for a period of time for bluing treatment, so that a layer of dense oxide film is formed on the surface of the punched sheet as The insulating film is then laminated to make a rotor and stator for a motor.

Wherein, the RH refining: the molten steel is sent to a vacuum RH refining furnace for smelting, and the steel is tapped when the S content is less than 80ppm.

Wherein, the specific method of RH refining is: sending the molten steel into a vacuum RH refining furnace for smelting, performing preliminary alloying according to the temperature of molten steel, oxygen content and the composition of the steel sample at the decarburization end point, and controlling the flow rate of argon to 140-170m ³ / h, first add aluminum block for deoxidation, then adjust Al to the target value, then add low-carbon ferromanganese, ferrophosphorus, etc. Sampling and oxygenation.

The process flow of this product is: molten iron pretreatment→converter smelting→argon blowing→RH scouring→CSP continuous casting→CSP heating furnace→CSP hot rolling→cold rolling→annealing→leveling and coiling→slitting→punching→annealing→electromagnetic Performance inspection→Packing and storage.

Smelted in a vacuum RH furnace. The core of the process is to use the RH vacuum degassing device to remove C in the molten steel to below 30ppm, solve the problem of the purity of the molten steel in electrical steel, and add alloys such as Mn and Al for alloying. Generally, S should be less than 80ppm when the molten steel leaves the station at RH.

Wherein, the RH refining: send the molten steel into a vacuum RH refining furnace for smelting, and add low-carbon Mn, Al and other alloys for alloying, so that the molten steel composition [C]≤0.003%, [Si]≤0.10%, 0.60%≤ [Mn]≤0.8%, [P]≤0.015%, [S]≤0.008%, 0.25%≤[Al]≤0.4%, tapping temperature 1580℃.

The core of the CSP continuous casting process is to control the increase of C and N in the process of molten steel from ladle-tundish-mold, using a special tundish covering agent and a special ultra-low C steel mold powder. The size of the slab is 55-70×1000-1275mm, and the casting speed is controlled at about 3.0-4.5m/min.

The hot rolling process adopts a reasonable temperature system and reduction system. In order to ensure that the finished electrical steel product has coarse grains, the heating temperature is 1000-1150°C, the furnace temperature is 980-1120°C, the finish rolling exit temperature is 920-860°C, and the coiling temperature is 680-720°C. The hot-rolling reduction system design should solve the two problems of strip shape control and grain coarsening at the same time. Therefore, in the first 3 to 4 passes of rolling, the reduction rate should be controlled within the maximum range allowed by the equipment. Ratio ≥ 50%, F1-F4 cumulative reduction rate ≥ 90%, F7 pass adopts small reduction rate to adjust plate shape and induce grain coarsening, reduction rate ≤ 15%. In order to make the fine ferrite grains formed by phase transformation after rolling have sufficient growth time, high coiling temperature is adopted, in order to form easily broken oxide scale, the pickling process is more efficient, and ultra-rapid cooling mode is adopted after rolling .

The oxide scale on the surface of the product is not dense and prone to breakage, so hydrochloric acid pickling (HCl) is used to pickle the acid solution with a concentration of 30-150g/L, use a pickling accelerator, the temperature of the pickling tank is 60-80°C, and the pickling speed is 150 -200m/min, to ensure that the surface quality of the strip steel is well controlled, trimming after pickling, and the shear end surface after trimming is smooth, without burrs, and without gaps, and the total reduction rate during cold rolling should be greater than 75%. Large reduction rate (above 35%), the reduction rate of the last frame is ≤8%. At the same time, roll shifting, bending roll and convex roll control are used to improve the shape of the plate.

Recrystallization annealing is carried out in a bell furnace, the annealing temperature is controlled at 650-750° C., and the holding time is controlled at 8-12 hours. After annealing, the cold-rolled sheet is tempered and stretched by 2 to 10% in the tempering unit, and then tensioned and divided into coils.

The divided steel coils are divided into coils on the slitting machine, cut to the width required by the motor rotor and stator, and continuously punched on the high-speed punching machine at a speed of 150-500 times/min.

Under the protective atmosphere of N ₂ or N ₂ +H ₂ , complete annealing in a continuous annealing furnace at 700-900°C, and then slowly cool to about 450°C, pass in water vapor, keep it for a period of time for bluing treatment, and make the punched sheet A dense oxide film is formed on the surface as an insulating film, and then laminated to make an iron core.

Compared with the prior art, the semi-process cold-rolled non-oriented electrical steel manufactured by the present invention has the following advantages:

The investment cost of semi-process cold-rolled non-oriented electrical steel produced by thin slab continuous casting and rolling process is 20-30% lower than that of traditional process.

The product performance is stable, the surface quality, plate shape quality, and dimensional accuracy are good, meeting national standards and customer requirements.

The product processing performance is good and excellent.

The grade of the present invention is BD600 (50WB800), the thickness is 0.50mm semi-process cold-rolled non-oriented electrical steel, the product electromagnetic performance P15/50≤4.5W/kg, the magnetic induction intensity B50≥1.72T, and the current semi-process non-oriented electrical steel Compared with the national standard, the iron loss is 1.5W/kg lower, and the magnetic induction intensity is 0.02T higher

The semi-process cold-rolled non-oriented electrical steel rotor and stator produced by the thin slab continuous casting and rolling process produced by the present invention have good electromagnetic performance and process performance, and have better performance than the motor rotor and stator made of cold-rolled common non-oriented electrical steel. Low processing performance, electromagnetic performance, cost, environmental protection advantages.

detailed description

The present invention will be further described below in conjunction with some specific embodiments. The specific examples are to further describe the present invention in detail, without limiting the protection scope of the present invention.

Explanation of terms: RH refining is called RH vacuum circulation degassing refining method.

Example 1

A thin slab continuous casting and rolling process to produce semi-process cold-rolled non-oriented electrical steel rotor, stator production method, the implementation steps are:

Step 1), molten iron pretreatment: Pour the blast furnace molten iron into the ladle, and perform magnesium blowing desulfurization through the molten iron pretreatment;

Step 2), converter smelting: oxygen top-bottom compound blowing converter, pour the molten steel after desulfurization into the oxygen top-bottom compound blowing converter, add scrap steel accounting for 12% of the total weight into the converter at the same time, and pour it into the converter during the blowing process Limestone and fluorite are added into the furnace, when the composition of molten steel [C]≤0.06%, [P]≤0.04%, [S]≤0.15%, when the end point temperature of molten steel is 1680℃, steel is tapped with constant oxygen;

Step 3), argon blowing: Add composite deoxidizer when tapping the converter, and blow argon throughout the process of tapping the converter. After blowing argon, measure the temperature of the molten steel, set oxygen, take samples, and feed aluminum into the molten steel according to the oxygen content in the molten steel Wire;

Step 4), RH refining: the molten steel is sent to the RH refining furnace for smelting, and alloys such as low-carbon Mn and Al are added for alloying, so that the molten steel composition [C]=0.002%, [Si]=0.08%, [Mn] = 0.7%, [P] = 0.012%, [S] = 0.006%, [Al] = 0.35%, the tapping temperature is 1580°C; the specific method is: put the molten steel into the vacuum RH refining furnace for smelting, according to the molten steel temperature , oxygen content and decarburization end point steel sample components for preliminary alloying, increase the argon flow rate and control it at 140-170m ³ /h, first add aluminum block for deoxidation, then adjust Al to the target value, and then add low carbon ferromanganese and phosphorus Iron and other components are initially adjusted. After the alloy is added, it is circulated for 3 minutes under the condition of ultimate vacuum ≤ 130Pa, temperature measurement, sampling, and oxygen determination. If the initial adjustment does not meet the requirements of the steel type, the composition is fine-tuned;

Step 5), continuous casting: the molten steel is cast into a 70mm thick slab through a thin slab continuous casting machine, the casting speed of the continuous casting machine is 3.8m/min, the temperature of the continuous casting slab into the furnace is ≥850°C, and the temperature of the heating section in the furnace is 1120°C , the temperature of the slab out of the furnace is 1080°C, the exit temperature of the finish rolling is 880°C, the coiling temperature is 700°C, the F1 reduction rate is 53.2%, the F2 reduction rate is 50.3%, and the F7 reduction rate is 12.6%. The rolling thickness is 2.5mm hot rolled plate;

Step 6) pickling and cold rolling: After the temperature of the hot-rolled sheet is lower than 60°C, it is pickled with 70g/L hydrochloric acid, the temperature of the acid tank is 75°C, and the pickling time is 75 seconds to remove impurities and oxidation on the surface of the steel coil. Iron sheet, the pickled steel coil is rolled into a steel coil with a thickness of 0.52mm by a cold-rolling tandem rolling mill;

Step 7), annealing: annealing at 680°C for 12 hours after cold rolling;

Step 8), post-processing: the steel coil after the annealing is smoothed by 5% elongation, stretched and divided into coils, and the steel coil after the division is divided into strips with a width of 64mm on the slitting machine, and continuously punched on a high-speed punching machine sheet, punching speed is 320 times/min, to produce rotors and stator loose sheets for motors, put these rotors and stators into continuous annealing furnace, under the protective atmosphere of _N2 or _N2 + _H2 , in the annealing furnace Complete annealing at 780°C, then slowly cool to about 520°C, pass in water vapor, keep for a period of time for bluing treatment, so that a dense oxide film is formed on the surface of the punched sheet as an insulating film, and then laminated to make a motor Rotor, stator.

The semi-process cold-rolled non-oriented electrical steel rotor and stator produced by this method have an iron loss of 4.2W/kg and a magnetic induction of 1.72T. Users can directly purchase them for motor manufacturing according to their needs. Since there is no coating, they have good Environmental protection and cost advantages.

Example 2

A thin slab continuous casting and rolling process to produce semi-process cold-rolled non-oriented electrical steel rotor, stator production method, the implementation steps are:

Step 1), molten iron pretreatment: Pour the blast furnace molten iron into the ladle, and perform magnesium blowing desulfurization through the molten iron pretreatment;

Step 2), converter smelting: oxygen top-bottom compound blowing converter, pour the molten steel after desulfurization into the oxygen top-bottom compound blowing converter, add scrap steel accounting for 12% of the total weight into the converter at the same time, and pour it into the converter during the blowing process Limestone and fluorite are added into the furnace, when the composition of molten steel [C]≤0.06%, [P]≤0.04%, [S]≤0.15%, when the end point temperature of molten steel is 1680℃, steel is tapped with constant oxygen;

Step 3), argon blowing: Add composite deoxidizer when tapping the converter, and blow argon throughout the process of tapping the converter. After blowing argon, measure the temperature of the molten steel, set oxygen, take samples, and feed aluminum into the molten steel according to the oxygen content in the molten steel Wire;

Step 4), RH refining: send the molten steel into a vacuum RH refining furnace for smelting, and add low-carbon Mn, Al and other alloys for alloying, so that the components of molten steel [C]=0.003%, [Si]=0.09%, [Mn] = 0.75%, [P] = 0.015%, [S] = 0.008%, [Al] = 0.38%, the tapping temperature is 1590°C; the specific method is: put the molten steel into the vacuum RH refining furnace for smelting, according to the molten steel temperature , oxygen content and decarburization end point steel sample components for preliminary alloying, increase the argon flow rate and control it at 140-170m ³ /h, first add aluminum block for deoxidation, then adjust Al to the target value, and then add low carbon ferromanganese and phosphorus Iron and other components are initially adjusted. After the alloy is added, it is circulated for 3 minutes under the condition of ultimate vacuum ≤ 130Pa, temperature measurement, sampling, and oxygen determination. If the initial adjustment does not meet the requirements of the steel type, the composition is fine-tuned;

Step 5), continuous casting: the molten steel is cast into a 70mm thick slab through a thin slab continuous casting machine, the casting speed of the continuous casting machine is 3.8m/min, the temperature of the continuous casting slab into the furnace is ≥850°C, and the temperature of the heating section in the furnace is 1120°C , the temperature of the slab out of the furnace is 1080°C, the exit temperature of the finish rolling is 880°C, the coiling temperature is 680°C, the reduction rate of F1 is 54.1%, the reduction rate of F2 is 51.2%, and the reduction rate of F7 is 14.7%. 2.5mm hot rolled plate;

Step 6) pickling and cold rolling: After the temperature of the hot-rolled sheet is lower than 60°C, it is pickled with 70g/L hydrochloric acid, the temperature of the acid tank is 75°C, and the pickling time is 75 seconds to remove impurities and oxidation on the surface of the steel coil. Iron sheet, the steel coil after pickling is rolled into a steel coil with a thickness of 0.53mm by a cold-rolling tandem rolling mill;

Step 7), annealing: annealing at 700°C for 12 hours after cold rolling;

Step 8), post-processing: After annealing, the cold-rolled coil is treated with 8% elongation, stretched, straightened and divided into coils, and the steel coil after division is divided into strips with a width of 64mm on the slitting machine, and continuously punched on a high-speed punching machine slices, the punching speed is 200 times/min, and the rotors and stators for motors are produced. Put these rotors and stators into the continuous annealing furnace, and under the protective atmosphere of N ₂ or N ₂ +H ₂ , in the annealing furnace Complete annealing at 780°C, then slowly cool to about 500°C, pass in water vapor, keep for a period of time for bluing treatment, so that a dense oxide film is formed on the surface of the punched sheet as an insulating film, and then laminated to make a motor Rotor, stator.

The semi-process cold-rolled non-oriented electrical steel rotor and stator produced by this method have an iron loss of 4.12W/kg and a magnetic induction of 1.72T. Users can directly purchase them for motor manufacturing according to their needs. Since there is no coating, they have good Environmental protection and cost advantages.

The above is only an embodiment of the present invention, and does not limit the patent scope of the present invention. Any equivalent structure or equivalent process conversion made by using the content of the description of the present invention, or directly or indirectly used in other related technical fields, shall be The same reasoning is included in the patent protection scope of the present invention.

Claims (7)

1. A thin slab continuous casting and rolling process produces semi-process cold-rolled non-oriented electrical steel rotor and stator production method, which is characterized in that it comprises: Step 1), molten iron pretreatment; Step 2), converter smelting: adding scrap steel with a total weight of 12% into the converter, and tapping with constant oxygen; Step 3), blowing argon: adding a composite deoxidizer when tapping the converter, and blowing argon throughout the process of tapping the converter; Step 4), RH refining: sending molten steel into a vacuum RH refining furnace to smelt Al; Step 5), continuous casting: the molten steel is cast into a 55-70mm thick slab through a thin slab continuous casting machine, the casting speed of the continuous casting machine is 3.0-4.5m/min, the temperature of the continuous casting slab into the furnace is ≥850°C, and the heating section in the furnace The temperature is 1000-1150°C, the slab exit temperature is 980-1120°C, the finish rolling exit temperature is 860-920°C, the coiling temperature is 680-720°C, the F1 reduction rate is ≥50%, and the F1～F4 cumulative reduction Ratio ≥ 90%, F7 reduction rate 15.6%, rolled into hot-rolled sheet with a thickness of 2-3mm; Step 6), pickling and cold rolling: After the temperature of the hot-rolled sheet is lower than 60°C, it is pickled with hydrochloric acid with a concentration of 30-150g/L, the temperature of the acid tank is 60-80°C, and the pickling time is 60-120 seconds, and the Impurities and iron oxide scales on the surface of the steel coil are then cold-rolled; Step 7), annealing: annealing at 650-750°C for 8-12 hours after cold rolling; Step 8), post-processing: the annealed steel coil is smoothed by 2-10% elongation, stretched and straightened into coils, and the coiled steel coils are divided into strips of different widths on the slitting machine, and continuously processed on a high-speed punching machine Punching, the punching speed is 150-500 times/min, and the rotors and stators for motors are produced. Put these rotors and stators into a continuous annealing furnace, under the protective atmosphere of _N2 or _N2 + _H2 , Perform complete annealing in an annealing furnace at 700-900°C, then slowly cool to about 400-520°C, pass in water vapor, keep for a period of time for bluing treatment, so that a dense oxide film is formed on the surface of the punched sheet as an insulating film, Then the laminations are made into rotors and stators for motors. 2. The method of claim 1, wherein: The step 5) is specifically: the molten steel is cast into a 55-70mm thick slab through a thin slab continuous casting machine, the casting speed of the continuous casting machine is 3.0-4.5m/min, the temperature of the continuous casting slab into the furnace is ≥850°C, and the furnace is heated The section temperature is 1000-1150°C, the slab exit temperature is 980-1120°C, the finish rolling exit temperature is 860-920°C, the coiling temperature is 680-720°C, the F1 reduction rate is ≥50%, and the F1～F4 cumulative pressure Reduction rate ≥ 90%, F7 reduction rate 15.6%, rolled into a hot-rolled plate with a thickness of 2-3mm. 3. The method of claim 2, wherein: The step 6) is specifically: after the temperature of the hot-rolled sheet is lower than 60°C, it is pickled with hydrochloric acid with a concentration of 30-150g/L, the temperature of the acid bath is 60-80°C, and the pickling time is 60-120 seconds, and the steel plate is removed. Impurities and iron oxide scales on the surface of the coil, the steel coil after pickling is rolled into a steel coil with a thickness of 0.50-0.55mm by a cold-rolling tandem rolling mill. 4. The method of claim 3, wherein: The step 8) is specifically: after the annealed steel coil is smoothed by 2-10% elongation, it is stretched and divided into coils, and the divided steel coil is divided into strips on the slitting machine, and the sheets are continuously punched on a high-speed punching machine , the punching speed is 150-500 times/min, and the rotors and stators for motors are produced, and these rotors and stators are put into a continuous annealing furnace, under the protective atmosphere of N ₂ or N ₂ +H ₂ , annealing Complete annealing in the furnace at 700-900°C, then slowly cool to about 400-520°C, pass in water vapor, keep for a period of time for bluing treatment, so that a dense oxide film is formed on the surface of the punched sheet as an insulating film, and then laminated The sheets are made into rotors and stators for motors. 5. The method according to any one of claims 1-4, characterized in that: The RH refining: send the molten steel into a vacuum RH refining furnace for smelting, and add alloys such as low-carbon Mn and Al for alloying, and tap out when the S content is less than 80ppm. 6. The method according to claim 5, characterized in that: The RH refining: send the molten steel into a vacuum RH refining furnace for smelting, and add low-carbon Mn, Al and other alloys for alloying, so that the components of molten steel [C]≤0.003%, [Si]≤0.10%, 0.60%≤[Mn ]≤0.8%, [P]≤0.015%, [S]≤0.008%, 0.25%≤[Al]≤0.4%, tapping temperature 1580℃. 7. The method according to claim 6, characterized in that: The specific method of RH refining is as follows: sending molten steel into a vacuum RH refining furnace for smelting, performing preliminary alloying according to the temperature of molten steel, oxygen content and the composition of the steel sample at the end of decarburization, and controlling the flow rate of argon to 140-170m ³ /h, First add aluminum block for deoxidation, then adjust Al to the target value, then add low-carbon ferromanganese, ferrophosphorus, etc. Oxygen.