A low-aluminum axle steel and a method of smelting the same

Abstract

The application discloses a kind of low-aluminum axle steel and its smelting method, comprising: deoxidizer control, LF refining control and vacuum treatment process control, wherein, Al-Ba alloy is added to molten steel as deoxidizer according to 1.5-2.0 kg / ton steel dosage of additive;Adjust the component of slag system and add 3-6% fluorite;Control the vacuum degree ≤60Pa, keep time ≥20 minutes, and combine bottom argon blowing to carry out strong stirring.Making the Al content in steel be stably controlled below 0.010%, the oxygen content is controlled below 0.0015%, the various inclusions in steel is controlled below 1 level, so that the steel purity is significantly improved, suitable for high standard rail transit axle steel manufacturing.By taking Al-Ba alloy as deoxidizer, the amount of aluminum is reduced, through high alkalinity + fluorite refining slag system coordination: can effectively reduce the viscosity of slag, adsorb floating inclusions, by controlling vacuum degree and keeping time, combined with bottom argon blowing strong stirring, can realize the deep degassing and inclusion removal of molten steel.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical technology, specifically relating to a low-aluminum axle steel and its smelting method. Background Technology

[0002] The axle is a critical running gear for train operation, and its quality is crucial to the safe operation of the train. Studies have shown that the main cause of train axle failure is brittle inclusions present in the axle steel.

[0003] Traditional axle steel smelting uses all-aluminum deoxidation. While this method is highly efficient, it leaves aluminum residue. This residue easily combines with dissolved oxygen in the molten steel to form Al2O3 inclusions or Al2O3-based complex inclusions, affecting the safe use and service life of the axle. Therefore, it is necessary to study reducing the amount of aluminum used as a deoxidizer while maintaining a good deoxidation effect to reduce brittle oxide inclusions and improve steel purity. Summary of the Invention

[0004] To address some or all of the technical problems existing in the prior art, the present invention provides a low-aluminum axle steel and its smelting method.

[0005] In one aspect of the present invention, the smelting method for low-aluminum axle steel includes:

[0006] (1) Deoxidizer control: Add Al-Ba alloy as deoxidizer to molten steel at a dosage of 1.5-2.0 kg / ton of steel;

[0007] (2) LF refining control, adjust the slag composition to CaO: 50-60%, SiO2: 3-8%, Al2O3: 15-20%, MgO: 3-8%, CaF2: 3-6%, BaO: 3-8%, and add 3-6% fluorite;

[0008] (3) Vacuum treatment process control: control the vacuum degree to ≤60Pa and the holding time to ≥20 minutes, and combine bottom blowing argon gas for stirring.

[0009] Furthermore, in LF refining control, the binary basicity R is controlled to be ≥8, and the slag amount is controlled to be 1.5%-1.8% of the molten steel weight.

[0010] Furthermore, the ratio of Al to Ba elements in the Al-Ba alloy is 6:4.

[0011] In another aspect of the invention, the provided low-aluminum axle steel is produced based on the above-mentioned smelting method for low-aluminum axle steel, wherein the low-aluminum axle steel has Al≤0.010%, T[O]≤15ppm, and the rolled axle blank has A, B, C, D, and DS type inclusions ≤1 grade.

[0012] The low-aluminum axle steel and its smelting method of the present invention have the following advantages and beneficial effects:

[0013] By using Al-Ba alloy as a deoxidizer, the amount of aluminum used is reduced. At the same time, the BaO-Al2O3 oxide generated has a low melting point and is more likely to float to the liquid surface. Through the synergistic effect of high basicity (R≥8) + fluorite refining slag system, the viscosity of the slag can be reduced, effectively adsorbing the floating inclusions. By ensuring a vacuum degree ≤60Pa and a holding time ≥20 minutes, combined with strong bottom blowing argon stirring, a vigorous reaction between slag and metal can be achieved under vacuum conditions, thereby achieving the purpose of deep degassing and inclusion removal of molten steel. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only for further understanding of the embodiments of the present invention and constitute a part of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings:

[0015] Figure 1 This is a flowchart of the low-aluminum axle steel smelting method of the present invention;

[0016] Figure 2 This is a microscopic schematic diagram of the 0.5 grade C inclusions of the present invention;

[0017] Figure 3 This is a microscopic schematic diagram of the 0.5-level Ds-type inclusions of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0019] See Figure 1 The low-aluminum axle steel and its smelting method provided by this invention include:

[0020] (1) Deoxidizer control: Add Al-Ba alloy as a deoxidizer to molten steel at a dosage of 1.5-2.0 kg / ton of steel;

[0021] (2) LF refining control, adjust the slag composition to CaO: 50-60%, SiO2: 3-8%, Al2O3: 15-20%, MgO: 3-8%, CaF2: 3-6%, BaO: 3-8%, and add 3-6% fluorite;

[0022] (3) Vacuum treatment process control: control the vacuum degree to ≤60Pa and the holding time to ≥20 minutes, and combine bottom blowing argon gas for stirring.

[0023] By using Al-Ba alloy as a deoxidizer, the amount of aluminum used is reduced compared to the amount of pure aluminum added in 2.5 kg / ton of steel. At the same time, the BaO-Al2O3 oxide generated has a low melting point and is more likely to float to the liquid surface.

[0024] Adding fluorite can effectively reduce the viscosity of slag, making it more effective at adsorbing inclusions in steel that float to the surface of the liquid.

[0025] By ensuring a vacuum degree ≤60Pa and a holding time ≥20 minutes, combined with strong stirring with bottom-blown argon, inclusions in the molten steel can be caused to float to the surface, achieving a vigorous reaction between slag and metal under vacuum conditions, thereby achieving deep degassing of the molten steel and removal of inclusions.

[0026] Furthermore, in LF refining control, the binary basicity R is controlled to be ≥8, and the slag amount is controlled to be 1.5%-1.8% of the molten steel weight.

[0027] Slag systems with high basicity R(CaO / SiO2)≥8 are more conducive to adsorbing inclusions in steel that float to the liquid surface.

[0028] Furthermore, the ratio of Al to Ba elements in the Al-Ba alloy is 6:4.

[0029] The following specific embodiments further illustrate the low-aluminum axle steel and its smelting method of the present invention.

[0030] Example 1

[0031] The chemical composition of the EA1N axle steel in Example 1 of this invention, by mass percentage, satisfies the following: C≤0.40, Si≤0.50, Mn≤1.20, P≤0.020, S≤0.015, Cr≤0.30, Mo≤0.08, Ni≤0.30, Cu≤0.30, V≤0.06. The manufacturing method of the EA1N axle steel in Example 1 specifically includes the following steps:

[0032] (1) EBT-EAF electric furnace smelting was carried out. The raw materials were 12 tons of scrap steel and 75 tons of molten iron. Oxygen was blown through the side wall of the electric furnace during the electric furnace smelting process. 3716 kg of lime was added in two batches for electric furnace smelting.

[0033] (2) The electric furnace produced 84 tons of molten steel. The measured temperature of the molten steel was 1643℃. The chemical composition of the molten steel was: C = 0.25%, Si = 0.041%, Mn = 0.092%, P = 0.008%, S = 0.021%, Cr = 0.040%, Al = 0.004%, Cu = 0.007%, V = 0.001%.

[0034] (3) During the tapping process, 800 kg of lime, 400 kg of synthetic slag, 150 kg of ferrosilicon, 741 kg of high-carbon ferromanganese and 130 kg of Al-Ba deoxidizer are added with the molten steel.

[0035] (4) The molten steel is sent to the LF station for power supply and heating. 240kg lime, 90kg fluorite, 70kg high carbon ferromanganese, 60kg ferrovanadium and 250kg high carbon ferrochrome are added to the molten steel.

[0036] (5) According to actual testing, the composition of LF slag system is: CaO = 58%, SiO2 = 5.8%, Al2O3 = 18.8%, MgO = 5.6%, CaF2 = 5.6%, BaO = 5.4%, ∑(FeO+MnO) = 0.8%, R(CaO / SiO2) = 10;

[0037] (6) Send the molten steel into the VD station, move the VD sealing cover to evacuate the vacuum to 56 Pa, control the argon flow rate to 0.11 m3 / min, and maintain for 20 minutes.

[0038] (7) After breaking the void, add a covering agent to the molten steel, adjust the bottom blowing argon flow rate to 35NL / min, and stir gently for 20 minutes;

[0039] (8) After the VD vacuum treatment, the actual test showed that the temperature of the molten steel was 1575℃. The chemical composition of the molten steel was: C = 0.33%, Si = 0.24%, Mn = 1.05%, P = 0.007%, S = 0.002%, Cr = 0.12%, Al = 0.008%, V = 0.04%, Ni = 0.01%, Mo = 0.01%, Cu = 0.01%;

[0040] (9) The ladle is transferred to the casting platform and continuously cast into a φ690mm billet. The billet is then heated and rolled into axle blanks at the steel rolling mill;

[0041] (10) Actual testing showed that the Al content of the shaft blank was 0.007% and T[O] = 0.0012%. The inclusion analysis results were A: grade 0, B: grade 0, C: grade 0.5, D: grade 0.5, DS: grade 0.5.

[0042] Example 2

[0043] (1) EBT-EAF electric furnace smelting was carried out. The smelting steps were the same as in Example 1, except that the amount of Al-Ba alloy added during tapping was 160 kg.

[0044] (2) The LF refining steps are the same as in Example 1, except that the amount of lime added is 300 kg and the amount of fluorite added is 100 kg;

[0045] (3) According to actual testing, the composition of LF slag system is: CaO = 59.3%, SiO2 = 4.5%, Al2O3 = 19.2%, MgO = 5.8%, CaF2 = 5.3%, BaO = 5.2%, ∑(FeO+MnO) = 0.7%, R(CaO / SiO2) = 13.2;

[0046] (4) The LF refining steps are the same as in Example 1, except that the vacuum degree is 56 Pa and the argon flow rate is 0.11 m³ / s. 3 / min, hold time is 25 minutes;

[0047] (5) Continuous casting and rolling are the same as in Example 1;

[0048] (6) Actual testing showed that the Al content of the shaft blank was 0.006%, and T[O] = 0.0010%. The inclusion analysis results were A: grade 0, B: grade 0, C: grade 0, D: grade 0.5, and DS: grade 0.5.

[0049] In summary, by using Al-Ba alloy as a deoxidizer, the amount of aluminum used is reduced. At the same time, the BaO-Al2O3 oxide generated has a low melting point and is more likely to float to the liquid surface. Through the synergistic effect of a high basicity (R≥8) + fluorite refining slag system, the viscosity of the slag can be reduced, effectively adsorbing the floating inclusions. By ensuring a vacuum degree ≤60Pa and a holding time ≥20 minutes, combined with strong bottom blowing argon stirring, a vigorous reaction between slag and metal can be achieved under vacuum conditions, thereby achieving the purpose of deep degassing and inclusion removal of molten steel.

[0050] It should be noted that, unless otherwise specified, the terms used herein have the meanings commonly understood by those skilled in the art. Furthermore, when a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum. Further, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Moreover, when multiple ranges are provided to describe features, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0051] It should also be noted that, in this document, the term "comprising" or any other variation thereof is intended to cover non-exclusive inclusion, such that an article or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or device.

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the present invention.

Claims

1. A method for smelting low-aluminum axle steel, characterized in that, include: (1) Deoxidizer control: Al-Ba alloy is added to molten steel as a deoxidizer at a dosage of 1.5-2.0 kg / ton of steel; (2) LF refining control, adjust the slag composition to CaO: 50-60%, SiO2: 3-8%, Al2O3: 15-20%, MgO: 3-8%, CaF2: 3-6%, BaO: 3-8%, and add 3-6% fluorite; (3) Vacuum treatment process control: control the vacuum degree ≤60Pa and the holding time ≥20 minutes, and combine bottom blowing argon gas for stirring.

2. The smelting method for low-aluminum axle steel according to claim 1, characterized in that, In LF refining control, the binary basicity R is controlled to be ≥8, and the slag amount is controlled to be 1.5%-1.8% of the molten steel weight.

3. The smelting method for low-aluminum axle steel according to claim 1, characterized in that, The ratio of Al to Ba elements in the Al-Ba alloy is 6:

4.

4. A low-aluminum axle steel, prepared according to the smelting method of low-aluminum axle steel as described in any one of claims 1-3, characterized in that, The low-aluminum axle steel has an Al content of ≤0.010%, a T[O] content of ≤15ppm, and the rolled axle blank has an inclusion level of A, B, C, D, and DS of ≤1.

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