A method for producing a high-sulfur steel bar by using blast furnace slag

Abstract

The application discloses a production and preparation method of a blast furnace slag smelted sulfur-containing steel bar, and belongs to the field of metallurgical material preparation. The method adopts a converter+LF refining+RH vacuum degassing+continuous casting smelting process, replaces part of lime and sulfur lines with blast furnace waste slag, and produces and manufactures sulfur-containing free-cutting steel bars, so that the mechanical properties, high hardness, high steel purity and other indexes of the sulfur-containing free-cuting steel bars are ensured, the surface quality level of the sulfur-containing free-cutting steel bars is ensured, and the quality requirements of high-end products are met.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of special steel preparation, in particular to a production preparation method of sulfur-containing steel bar smelted by blast furnace slag. BACKGROUND

[0002] Free-cutting steel is divided into sulfur series, lead series, calcium series and their composite series. It was first developed to improve cutting speed, cutting precision and tool life. The mechanical properties are not high. With the development of mechanical manufacturing industry dominated by automobile industry, the requirement for material mechanical properties is higher and higher, and it is also required to have free machining property, which puts forward higher requirements for the development of free-cutting steel. High-strength steel with good cutting performance has very huge market potential, therefore, countries all over the world are researching high-strength free-cutting steel.

[0003] In the past decade, China's high-strength free-cutting steel has developed considerably, and has successively developed steel for manufacturing automobile engine connecting rod, crankshaft, gear and the like. However, its production level, quality, production cost and steel grade still have a gap with the world advanced countries. SUMMARY

[0004] The purpose of the present application is to provide a production preparation method of sulfur-containing free-cutting steel bar smelted by blast furnace slag instead of lime and sulfur line. The method adopts converter+LF+RH+continuous casting smelting process, and produces sulfur-containing free-cutting steel bar by replacing part of lime and sulfur line with blast furnace slag, which not only ensures the mechanical properties, high hardness and high steel purity of sulfur-containing free-cutting steel bar, but also ensures the surface quality level of sulfur-containing free-cutting steel bar, meeting the quality requirements of high-end products.

[0005] In order to achieve the above-mentioned purpose of the application, the present application provides a sulfur-containing steel bar smelted by blast furnace slag and a production preparation method thereof, including bar composition design and process design, and the specific steps are: converter smelting→LF refining→RH vacuum degassing→continuous casting heating→initial rolling mill rolling→continuous rolling mill set. The sulfur-containing free-cutting steel bar meets the quality requirements, and the mechanical properties, high hardness and high steel purity can also meet the standard requirements.

[0006] A sulfur-containing steel bar, the internal control chemical composition is as follows: C: 0.42% to 0.43%, Si: 0.22% to 0.28%, Mn: 0.77% to 0.82%, P: ≤0.013%, S: 0.012% to 0.023%, Cr: 1.05% to 1.10%, Alt: 0.023% to 0.036%, Cu: ≤0.04%, Ni: ≤0.04%, Mo: ≤0.04%, and the balance is iron and inevitable impurities.

[0007] Based on the above technical scheme, further, the carbon equivalent: Ceq=C+Si / 24+Mn / 6+Cr / 5+Mo / 4>=0.75%.

[0008] A production preparation method of a blast furnace slag smelting above-mentioned sulfur-containing steel bar, the process route comprises: converter smelting→ secondary refining (LF+RH)→ continuous casting→ heating process→ rolling process;

[0009] Wherein, the converter smelting: scrap and hot metal smelting are adopted, wherein scrap accounts for 25-35% and hot metal accounts for 65-70% by mass fraction; oxygen oxidation, violent boiling, tapping temperature is 1675-1680 DEG C, C is 0.13-0.15% when tapping, P is less than or equal to 0.010%, auxiliary materials and alloys are added when tapping 1 / 4-1 / 3. Alloy addition amount per ton of steel: silicon manganese 8.5-9 Kg / t, aluminum particle 1.2-1.3 Kg / t, high-carbon chromium iron 15.5-16.5 Kg / t, silicon iron 0.3-0.4 Kg / t, coke butter carbon additive 1.7-1.8 Kg / t. Auxiliary material addition amount per ton of steel: magnesite 8.7-9.2 Kg / t, active lime 17.5-18 Kg / t, lime 14.5-15 Kg / t, iron-carbon ball 6-6.5 Kg / t, small block coke 3.4-3.6 Kg / t; blast furnace slag is added during the addition of auxiliary materials, and the addition amount per ton of steel is 4-5 Kg / t steel.

[0010] Based on the above technical scheme, further, the blast furnace slag comprises the main components of CaO: 41-43%, MgO: 7-8%, SiO2: 35-36%, Al2O3: 12-13%, S: 0.85-0.9% by mass fraction, and the rest is impurities.

[0011] The present application adds 4-5 Kg / t of blast furnace slag during the addition of auxiliary materials, which can reduce the amount of lime by 4-5 Kg / t. There is no need to boil sulfur line after RH vacuum.

[0012] Based on the above technical scheme, further, the particle size of the small block coke is 2-5 cm.

[0013] Based on the above technical scheme, further, the LF refining is: using 21000-24000A large current to heat up the slag, when the slag surface fluctuates, the molten steel and the arc are not exposed, the active lime is supplemented, the chemical composition is sampled and analyzed after 5 minutes, the alloy is supplemented according to the target value of the chemical composition, and the carbon powder (steam coal) is added for carbon addition, and the alloy and the carbon powder (steam coal) should be added to the argon stream to promote the alloy and the carbon powder to melt and homogenize quickly. When the temperature of the molten steel reaches 1610-1615 DEG C, 1-3 kg / t of diffusion deoxidizer is added for diffusion deoxidation, the furnace door is closed for 10-15 minutes, and when the temperature of the molten steel reaches 1620-1630 DEG C, the chemical composition is sampled and analyzed for the second time to confirm the deviation of the content of each chemical element composition from the target value, after the second sampling, the diffusion deoxidizer is supplemented to continue the slag adjustment, and the alloy is supplemented at a rate of 3.2-3.4 kg / t, 0.07-0.1 kg / t of aluminum particles, 0.35-0.42 kg / t of silicon iron, and 0.85-0.9 kg / t of coke powder carbon additive. The pH value of the molten slag is kept at 2.5-3.5, the viscosity of the molten slag is 0.80-1.20 Pa·s, and the white slag smelting is kept for 20-30 minutes at the same time. When the temperature of the molten steel reaches 1630-1640 DEG C, 1.3-1.4 meters / t of steel of Al wire is fed for final deoxidation, and after the wire feeding is finished, the argon is blown statically for 10-20 minutes. The auxiliary material is supplemented at a rate of 5.6-6 kg / t of active lime and 1.2-1.3 kg / t of steam coal.

[0014] Based on the above technical scheme, further, the RH refining is: the argon pressure is controlled at 0.1-0.3 MPa before the vacuum pump is started, the molten steel is slightly moved without being exposed, when the vacuum degree reaches 100-110 Pa, the timing is started, and the time is kept for 10-15 minutes, the aluminum particles and high manganese are supplemented according to the target composition of the molten steel composition, and the argon pressure is adjusted to 0.3-0.5 MPa at the same time. After the static argon blowing is finished, 1.1-1.2 meters / t of steel of silicon calcium wire is added.

[0015] Based on the above technical scheme, further, the continuous casting is: continuously casting at 1545-1555 DEG C, the tundish temperature is 1530-1536 DEG C, the casting speed is 0.46-0.48 m / min, the H content in the tundish is controlled to be less than or equal to 2 ppm, the electromagnetic stirring current of the crystallizer is 400-420 A, the final electromagnetic stirring current is 330-350 A, and the frequency is 8-9 Hz; the whole process is protected by casting, and the crystallizer protection slag is a medium carbon steel protection slag; the light press is put into the second, third and fourth rollers, and the press amounts are 3-3.2 mm, 4-4.2 mm and 4-4.2 mm respectively; the automatic and manual combined mode is adopted for the casting blank cutting, the red steel pad is used for the continuous casting blank, the two furnace castings are pressed to ensure the flatness, and the holding time is 30-40 hours.

[0016] Based on the above technical scheme, further, the size of the continuous casting billet is 350mm*470mm.

[0017] Based on the above technical scheme, further, the rolling process comprises rough rolling machine rolling→ continuous rolling mill group rolling.

[0018] Based on the above technical scheme, further, the rolling in the process route is followed by heat preservation→ finishing→ inspection→ packaging and delivery to the warehouse→ delivery.

[0019] Based on the above technical scheme, further, the production specification of the bar is Φ50-250mm, preferably Φ65mm.

[0020] The beneficial effects of the present application are:

[0021] (1) The excavator support wheel shaft steel S40CrM bar is produced by adopting the converter+LF+RH+smelting process and the process of smelting sulfur-free cutting steel by replacing lime and sulfur line with blast furnace slag, the production specification is Φ65mm, the mechanical property requirements are met, and the steel purity is ensured.

[0022] (2) The reasonable component design and production process ensure the surface quality and impact performance.

[0023] (3) The macrostructure, non-metallic inclusions and mechanical properties of the finished steel meet the requirements of high-end products. DETAILED DESCRIPTION

[0024] The following non-limiting examples can enable those skilled in the art to more fully understand the present application, but do not limit the present application in any way.

[0025] The particle size of the small block coke in the following examples is 3-4cm.

[0026] Example 1

[0027] 1 Chemical composition

[0028] (1) The chemical composition, by mass percentage, is C: 0.43%, Si: 0.25%, Mn: 0.77%, P: 0.010%, S: 0.013%, Cr: 1.07%, Alt: 0.024%, Cu: 0.02%, Ni: 0.02%, Mo: 0.02%, and the balance is iron and unavoidable impurities.

[0029] (2) Carbon equivalent: Ceq=C+Si / 24+Mn / 6+Cr / 5+Mo / 4=0.787%.

[0030] 2 Sulfur-free cutting steel S40CrM converter continuous casting process parameter design

[0031] Process route: 180 t converter smelting → secondary refining (LF + RH) → 350 mm * 470 mm continuous casting → heating furnace heating → rolling (Φ65 mm) → heat preservation → finishing → inspection → packaging and delivery to the warehouse → shipment; among them:

[0032] (1) Converter smelting: using scrap steel and hot metal smelting, among which the mass fraction of scrap steel accounts for 27%, and hot metal accounts for 73%; the tapping temperature is 1678℃, the C is 0.13% at tapping, and the P is 0.010%; auxiliary materials and alloys are added at 1 / 4 tapping. Alloy addition per ton of steel: silicon manganese 8.7 Kg / t, aluminum particles 1.2 Kg / t, high-carbon chromium iron 15.7 Kg / t, silicon iron 0.35 Kg / t, and coke powder carbon additive 1.75 Kg / t. Auxiliary material addition per ton of steel: magnesite 8.8 Kg / t, active lime 17.7 Kg / t, lime 14.7 Kg / t, iron-carbon ball 6.3 Kg / t, and small block coke 3.5 Kg / t.

[0033] Blast furnace slag addition process: ① The composition of blast furnace slag is CaO: 42%, MgO: 7%, SiO2: 36%, Al2O3: 12%, S: 0.869%, and the rest is impurities. ② 4 Kg / t of blast furnace slag is added during the addition of auxiliary materials, which can reduce the amount of lime by 4 Kg / t.

[0034] ③ RH vacuum does not boil sulfur line.

[0035] (2) LF furnace: using 22000A high current to heat and slag, when the slag surface fluctuates, the molten steel and the electric arc are not exposed, active lime is added, and the chemical composition is analyzed after 5 minutes for the first time. Add alloy according to the target value of chemical composition, and add carbon powder (dynamic coal) for carbonization. Alloy and carbon powder should be added to the argon stream to promote rapid melting and homogenization of alloy and carbon powder. When the temperature of the molten steel reaches 1612℃, add 2 kg / t of diffusion deoxidizer for diffusion deoxidation, and close the door for 10 minutes. When the temperature of the molten steel reaches 1623℃, the second sampling analyzes the chemical composition to confirm the deviation of each chemical element content from the target value. After the second sampling, continue to adjust the slag by adding diffusion deoxidizer, and add alloy: high-carbon chromium iron 3.3 kg / t, aluminum particles 0.08 kg / t, silicon iron 0.37 kg / t, and coke powder carbon additive 0.88 kg / t. Maintain the pH value of the molten slag to 2.8 and the viscosity of the molten slag to 0.90 Pa·s, and continue white slag smelting for 24 minutes. When the temperature of the molten steel reaches 1635℃, perform final deoxidation by feeding Al wire 1.35 meters / t, and start argon blowing after the wire feeding is completed, and maintain for 15 minutes. Add auxiliary materials: active lime 5.8 Kg / t, and dynamic coal 1.26 Kg / t.

[0036] (3) RH refining: argon pressure is controlled at 0.18 MPa before vacuum pump is started, so that the slag surface slightly moves the molten steel without being exposed, when the vacuum degree reaches 100 Pa, the timing is started, the holding time is 13 min, according to the composition of the molten steel, the aluminum particles and high manganese are added, at the same time, the argon pressure is adjusted to 0.4 MPa, after the end of the static argon blowing, the silicon calcium wire 1.1 m / t is added.

[0037] (4) Continuous casting: continuous casting at 1549 ℃, tundish temperature 1532 ℃, casting speed 0.46 m / min, H control in tundish 1.2 ppm, electromagnetic stirring current in crystallizer 400 A, electromagnetic stirring current at the end 330 A, frequency 8 Hz; whole process protection casting, crystallizer protection slag medium carbon steel protection slag is used; light press is put into the 2nd, 3rd and 4th rollers, the press amount is 3 mm, 4 mm and 4 mm respectively; the automatic and manual combined mode is used for casting blank cutting, the red steel pad is used for continuous casting blank, the upper pressure of two furnace blanks is used to ensure the flatness, the holding time is 34 h.

[0038] Example 2

[0039] 1 Chemical composition

[0040] (1) The chemical composition is C: 0.43%, Si: 0.24%, Mn: 0.78%, P: 0.011%, S: 0.015%, Cr: 1.08%, Alt: 0.026%, Cu: 0.02%, Ni: 0.02%, Mo: 0.03%, the balance is iron and inevitable impurities.

[0041] (2) Carbon equivalent: Ceq = C + Si / 24 + Mn / 6 + Cr / 5 + Mo / 4 = 0.79%.

[0042] 2 Sulfur-containing free-cutting steel S40CrM converter continuous casting process parameter design

[0043] Process route: 180 t converter smelting → secondary refining (LF + RH) → 350 mm * 470 mm continuous casting → heating furnace heating → rolling (Φ65 mm) → holding → finishing → inspection → packaging and delivery to the warehouse → delivery; wherein:

[0044] (1) Converter smelting: using scrap and molten iron smelting, wherein the mass fraction of scrap accounts for 28%, and the mass fraction of molten iron accounts for 72%; oxygen oxidation, vigorous boiling, tapping temperature 1677 ℃, C 0.13% at tapping, P 0.010% at tapping, auxiliary materials and alloys are added at 1 / 4 tapping. Alloy addition amount per ton of steel: silicon manganese 8.8 Kg / t, aluminum particles 1.2 Kg / t, high-carbon chromium iron 15.8 Kg / t, silicon iron 0.35 Kg / t, coke powder carbon additive 1.75 Kg / t. Auxiliary material addition amount per ton of steel: magnesite 8.8 Kg / t, active lime 18 Kg / t, lime 14.7 Kg / t, iron-carbon ball 6 Kg / t, small block coke 3.5 Kg / t.

[0045] Blast furnace slag addition process: ①The composition of blast furnace slag is CaO: 42%, MgO: 7%, SiO2: 36%, Al2O3: 13%, S: 0.87%, and the balance is impurities. ②During the addition of auxiliary materials, 4-5 Kg / t of blast furnace slag is added, which can reduce 4-5 Kg / t of lime. ③After RH vacuum, no more sulfur line is boiled.

[0046] (2) LF furnace: 22000A large current is used to heat and slag, when the slag surface fluctuates, the molten steel and the electric arc are not exposed, active lime is added, the chemical composition is analyzed after 5 minutes, the alloy is added according to the target value of the chemical composition, and carbon powder (steam coal) is added for carbon addition, the alloy and carbon powder should be added to the argon stream to promote the rapid melting and homogenization of the alloy and carbon powder. When the temperature of the molten steel reaches 1612℃, 2kg / t of diffusion deoxidizer is added for diffusion deoxidation, the furnace door is closed for 10 minutes, and when the temperature of the molten steel reaches 1625℃, the chemical composition is analyzed for the second time to confirm the deviation of each chemical element composition from the target value. After the second sample is taken away, the diffusion deoxidizer is continuously added for slag adjustment, the alloy is added: high-carbon chromium iron 3.3kg / t, aluminum particles 0.08kg / t, silicon iron 0.38kg / t, and coke butter carbon additive 0.87kg / t. The slag basicity pH value is maintained at 2.8, the slag viscosity is 0.90 Pa·s, and the white slag smelting is continuously maintained for 27 minutes. When the temperature of the molten steel reaches 1636℃, the final deoxidation Al wire 1.35 meters / t is fed, and after the wire feeding is completed, the argon is blown statically for 16 minutes. The auxiliary materials are added: active lime 5.8 Kg / t, and steam coal 1.25 Kg / t.

[0047] (3) RH refining: The argon pressure is controlled at 0.18 MPa before the vacuum pump is started, the molten steel is slightly moved without exposure, and when the vacuum degree reaches 100 Pa, the timing is started, and the holding time is 10-15 minutes, and the aluminum particles and high manganese are added according to the composition of the molten steel. At the same time, the argon pressure is adjusted to 0.4 MPa, and after the static argon blowing is completed, 1.1 meters / t of silicon calcium wire is added.

[0048] (4) Continuous casting: continuous casting at 1549℃, tundish temperature 1532℃, casting speed 0.46m / min, tundish H control 1.5ppm, crystallizer electromagnetic stirring current 400A, end electromagnetic stirring current 330A, frequency 8Hz; whole process protection casting, crystallizer protection slag using medium carbon steel protection slag; light press-down into the 2nd, 3rd, 4th roller, press-down amount is 3mm, 4mm, 4mm respectively; casting blank cutting adopts automatic and manual combined mode, red steel pad at the top of continuous casting blank, and the casting blank of two furnaces is pressed to ensure flatness, and the holding time is 35h.

[0049] Example 3

[0050] 1 Composition optimization design

[0051] (1) The internal control chemical composition is determined as follows in mass percent: C: 0.42%, Si: 0.26%, Mn: 0.77%, P: 0.010%, S: 0.018%, Cr: 1.07%, Al: 0.028%, Cu: 0.02%, Ni: 0.02%, Mo: 0.02%, and the balance being iron and inevitable impurities.

[0052] (2) Carbon equivalent: Ceq = C + Si / 24 + Mn / 6 + Cr / 5 + Mo / 4 = 0.78%.

[0053] 2. Production process parameters design of sulfur-containing free-cutting steel S40CrM in converter and continuous casting

[0054] Process route: 180 t converter smelting → secondary refining (LF + RH) → 350 mm * 470 mm continuous casting → heating furnace heating → rolling (Φ65 mm) → heat preservation → finishing → inspection → packaging and delivery to the warehouse → shipment; wherein:

[0055] (1) Converter smelting: using scrap and hot metal smelting, wherein the mass fraction of scrap accounts for 25%, and hot metal accounts for 75%; oxygen oxidation, vigorous boiling, tapping temperature 1676℃, C is 0.13% at tapping, P is 0.010% at tapping, and auxiliary materials and alloys are added at 1 / 4 tapping. Alloy addition amount per ton of steel: silicon manganese 8.7 Kg / t, aluminum particles 1.2 Kg / t, high-carbon chromium iron 15.8 Kg / t, silicon iron 0.3 Kg / t, and coke powder carbon additive 1.7 Kg / t. Auxiliary material addition amount per ton of steel: magnesite 8.9 Kg / t, active lime 17.9 Kg / t, lime 14.8 Kg / t, iron-carbon ball 6.2 Kg / t, and small block coke 3.5 Kg / t.

[0056] Blast furnace slag addition process: ① The composition of blast furnace slag is as follows in mass percent: CaO: 42%, MgO: 8%, SiO2: 35%, Al2O3: 12%, S: 0.87%, and the balance being impurities. ② 4 Kg / t of blast furnace slag is added during the addition of auxiliary materials, which can reduce the amount of lime by 4 Kg / t.

[0057] ③ No sulfur line is boiled after RH vacuum.

[0058] (2) LF furnace: using 23000 A large current heating slag, when the slag surface fluctuation, molten steel and arc not bare, add active lime, 5 min after the first sampling analysis chemical composition, according to the chemical composition target value of alloy, and add carbon powder (power coal) for carbon addition, alloy and carbon powder should be added to the argon stream, to promote alloy and carbon powder quickly melt and homogenization. When the molten steel temperature reaches 1612 ℃, add 2 kg / t diffusion deoxidizer for diffusion deoxidation, close the door 10 min, when the molten steel temperature reaches 1626 ℃, second sampling analysis chemical composition, to confirm the deviation of each chemical element content from the target value, after the second sample, add diffusion deoxidizer to continue to adjust the slag, add alloy: high carbon chromium iron 3.2 kg / t, aluminum particles 0.08 kg / t, silicon iron 0.38 kg / t, coke carbon additive 0.87 kg / t. Maintain the slag basicity pH value of 2.9, slag viscosity 0.95 Pa·s, while continue to maintain white slag smelting 26 min, when the molten steel temperature reaches 1635 ℃, the final deoxidation feeding Al wire 1.3 m / t, after feeding wire start static argon, keep time 17 min. Add auxiliary materials: active lime 5.8 Kg / t, power coal 1.2 Kg / t.

[0059] (3) RH refining: before the vacuum pump starts, the argon pressure is controlled at 0.2 MPa, the slag surface is slightly moving and the molten steel is not bare, when the vacuum degree reaches 100 Pa, start timing, keep time 12 min, add aluminum particles and high manganese according to the composition of the molten steel, at the same time, adjust the argon pressure to 0.4 MPa, after static argon, add silicon calcium wire 1.1 m / t.

[0060] (4) Continuous casting: continuous casting 1550 ℃, tundish temperature 1532 ℃, casting speed 0.46 m / min, tundish H control 1.3 ppm, crystallizer electromagnetic stirring current 400 A, end electromagnetic stirring current 330 A, frequency 8 Hz; whole process protection casting, crystallizer protection slag using medium carbon steel protection slag; light press down into the 2nd, 3rd, 4th roller, press down amount is 3 mm, 4 mm, 4 mm respectively; casting blank cutting adopts automatic and manual combination, continuous casting blank red steel pad bottom, upper pressure two furnace blank to ensure flatness, holding time 36 h.

[0061] Product test results of examples 1-3

[0062] (1) Low magnification structure of Φ65 mm steel

[0063] No. General porosity Center porosity Ingot type segregation General spotted segregation Edge spotted segregation Standard ≤1.5 ≤1.5 ≤1.5 ≤1.0 ≤1.0 Example 1 0.5 0.5 0.5 0 0 Example 1 0.5 0.5 0.5 0 0 Example 2 0.5 0.5 0.5 0 0 Example 2 0.5 0.5 0.5 0 0 Example 3 0.5 0.5 0.5 0 0 Example 3 0.5 0.5 0.5 0 0

[0064] (2) Impact property of Φ65 mm steel

[0065]

[0066]

[0067] For any skilled person familiar in the art, many possible variations and modifications, or equivalent embodiments of equivalent variations, can be made to the technical solutions of the present application by using the technical contents disclosed above without departing from the scope of the technical solutions of the present application. Therefore, any simple modification, equivalent variation and modification made to the above embodiments according to the technical essence of the present application without departing from the content of the technical solutions of the present application should still belong to the scope of protection of the technical solutions of the present application.

Claims

1. A method for preparing sulfur-containing steel bars from blast furnace slag, characterized in that, The sulfur-containing steel bar, by mass percentage, comprises: C: 0.42%–0.43%, Si: 0.22%–0.28%, Mn: 0.77%–0.82%, P: ≤0.013%, S: 0.012%–0.023%, Cr: 1.05%–1.10%, Alt: 0.023%–0.036%, Cu: ≤0.04%, Ni: ≤0.04%, Mo: ≤0.04%, carbon equivalent ≥0.75%, with the balance being iron and unavoidable impurities; The method for preparing sulfur-containing steel bars from blast furnace slag includes: converter smelting → LF+RH refining → continuous casting → heating process → rolling → heat preservation. The converter smelting process involves using scrap steel and molten iron, with scrap steel comprising 25-35% and molten iron comprising 65-70% by mass. Oxygen oxidation and vigorous boiling are employed, with a tapping temperature of 1675-1680℃. At tapping, the carbon content is 0.13-0.15%, and the phosphorus content is ≤0.010%. Auxiliary materials and alloys are added when 1 / 4 to 1 / 3 of the steel has been tapped. The alloy addition amounts per ton of steel are: 8.5-9 kg / t silicon manganese and 1.2-1.3 kg / t aluminum granules. High-carbon ferrochrome 15.5~16.5kg / t, ferrosilicon 0.3~0.4kg / t, coke butadiene carbon raiser 1.7~1.8kg / t; Auxiliary materials added per ton of steel: magnesite 8.7~9.2kg / t, active lime 17.5~18kg / t, lime 14.5~15kg / t, iron-carbon balls 6~6.5kg / t, small coke 3.4~3.6kg / t; Blast furnace slag 4~5kg / t steel added during the process of adding auxiliary materials.

2. The preparation method according to claim 1, characterized in that, The blast furnace slag comprises the following main components by mass fraction: CaO: 41-43%, MgO: 7-8%, SiO2: 35-36%, Al2O3: 12-13%, and S: 0.85-0.9%.

3. The preparation method according to claim 1, characterized in that, The particle size of the small coke pieces is 2-5 cm.

4. The preparation method according to claim 1, characterized in that, The LF refining process involves: using a high current of 21000–24000A to heat and slag; when the slag surface fluctuates and the molten steel and electric arc are not exposed, adding active lime; after 5 minutes, taking a first sample to analyze the chemical composition; adding alloys according to the target chemical composition values; and adding thermal coal for carbonization; the alloys and thermal coal are added to the argon flow; when the molten steel temperature reaches 1610–1615℃, adding 1–3 kg / t of diffusion deoxidizer for diffusion deoxidation; closing the furnace door for 10 minutes; when the molten steel temperature reaches 1620–1630℃, taking a second sample to analyze the chemical composition to confirm the deviation of each chemical element content from the target value; after the second sample is removed, adding diffusion deoxidizer to continue slag adjustment; and so on. The alloying dosage per ton of steel is as follows: 3.2–3.4 kg / t high-carbon ferrochrome, 0.07–0.1 kg / t aluminum granules, 0.35–0.42 kg / t ferrosilicon, and 0.85–0.9 kg / t coke carburizer. Maintain the slag basicity (pH) at 2.5–3.5 and the slag viscosity at 0.80–1.20 Pa·s. Continue white slag smelting for 20–30 minutes. When the molten steel temperature reaches 1630–1640℃, perform final deoxidation and feed Al wire at a rate of 1.3–1.4 meters / t of steel. After wire feeding, begin static argon blowing for 10–20 minutes. The supplementary auxiliary materials added per ton of steel are: 5.6–6 kg / t quicklime and 1.2–1.3 kg / t thermal coal.

5. The preparation method according to claim 1, characterized in that, The RH refining process is as follows: Before starting the vacuum pump, the argon pressure is controlled at 0.1-0.3 MPa to ensure that the molten steel is not exposed when the slag surface is slightly moved. When the vacuum degree reaches 100-110 Pa, the timing is started and maintained for 10-15 minutes. Depending on the composition of the molten steel, aluminum particles and high manganese are added according to the target composition. At the same time, the argon pressure is adjusted to 0.3-0.5 MPa. After the static argon blowing is completed, 1.1-1.2 meters / ton of silicon-calcium wire is added.

6. The preparation method according to claim 1, characterized in that, The continuous casting process is as follows: continuous casting at 1545–1555℃, tundish temperature at 1530–1536℃, casting speed at 0.46–0.48 m / min, tundish H control ≤2 ppm, crystallizer electromagnetic stirring current at 400–420 A, end electromagnetic stirring current at 330–350 A, frequency at 8–9 Hz; full-process protective casting, using medium carbon steel protective slag in the crystallizer; lightly pressing the 2nd, 3rd, and 4th rolls, with reductions of 3–3.2 mm, 4–4.2 mm, and 4–4.2 mm respectively; billet cutting using a combination of automatic and manual methods, with the continuously cast billet placed on a red steel base, and two heats of billet pressed on top to ensure flatness, with a holding time of 30–40 hours.

7. The preparation method according to claim 1, characterized in that, The production specifications of the bars are Φ50~250mm.

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