Method for improving stability and uniformity of Mn content in single vacuum 300M steel

Abstract

The invention relates to the technical field of metal smelting, and discloses a method for improving the stability and uniformity of the content of Mn in single vacuum 300M steel, a vacuum arc consumable electrode is smelted and poured through the procedures of electric furnace smelting, LF smelting, VD smelting and die casting, and the content of Mn in the electrode is controlled to be Mn target component * (1.33-1.54); during vacuum arc consumable remelting, in the arc starting stage, the vacuum degree is set by adopting ultimate vacuum, and a current + voltage control mode is adopted; in the smelting stage, argon with the pressure of 0.5-0.6 Pa is filled into a vacuum chamber, and a melting speed and molten drop control mode is adopted; in the feeding stage, 0.9-1 Pa of argon is filled into a vacuum chamber, and a current + voltage control mode is adopted. By means of the method, the Mn content uniformity of the single-vacuum medium-low alloy ultra-high strength steel vacuum consumable ingot and the stability between batches of furnaces can be effectively improved, and meanwhile the vacuum degassing capacity in the vacuum consumable process and the energy utilization efficiency in the smelting process are both considered.

Description

Technical Field

[0001] The present invention relates to the technical field of metal smelting, and in particular to a method for improving the stability and uniformity of the Mn content in single vacuum low alloy ultra-high strength steel. Background Art

[0002] The main elements in medium and low alloy ultra-high strength steel are generally C, Cr, Mn, Si, Ni, Mo, W, etc., among which the range of Mn is usually 0.2-1.5%. Single vacuum refers to the preparation of medium and low alloy ultra-high strength steel by the EBT+LF+VD+MC+vacuum arc consumable remelting (VAR) smelting route. At present, the Mn content of single vacuum medium and low alloy ultra-high strength steel is controlled by calculating the Mn content recovery rate of the VAR process in advance when preparing the vacuum consumable electrode, leaving a surplus of Mn volatilization for a vacuum arc consumable remelting process. At the same time, the vacuum degree set in the vacuum arc consumable remelting process is the limit vacuum degree, but because the gas content is large and the gas content volatility is relatively large when preparing the vacuum arc consumable remelting electrode ingot through the EBT+LF+VD+MC process, and the control limit vacuum capacity of different vacuum arc consumable furnaces is inconsistent, the Mn content of actual single vacuum medium and low alloy ultra-high strength steel is relatively volatile between different furnace batches, and even in severe cases, there is a risk of exceeding the upper limit of Mn content control. During the vacuum consumable melting process, due to the high vapor pressure of manganese, the entire process of consumable electrode melting-droplet-molten pool-solidification is prone to volatilization in a vacuum and high temperature environment, resulting in large fluctuations in its content.

[0003] Therefore, there is a need in the prior art for improving the method of increasing the stability and uniformity of the Mn content in single vacuum 300M steel. Summary of the invention

[0004] In view of this, the purpose of the embodiment of the present invention is to propose a method for improving the stability and uniformity of the Mn content in single vacuum 300M steel, so as to solve the problem that the Mn content of the existing single vacuum low alloy ultra-high strength steel fluctuates greatly and the stability between batches is poor.

[0005] Based on the above purpose, the embodiment of the present invention provides a method for improving the stability and uniformity of Mn content in single vacuum 300M steel, comprising the following steps: The vacuum arc consumable electrode is melted and cast through electric furnace melting, LF melting, VD melting and die casting processes, and the Mn content in the electrode is controlled to be the Mn target composition* (1.33~1.54); During vacuum arc consumable remelting, In the arc starting stage, the vacuum degree adopts the extreme vacuum setting and the current + voltage control mode is adopted; During the melting stage, argon is filled into the vacuum chamber at 0.5-0.6 Pa, and the melting speed + droplet control mode is adopted; During the feeding stage, argon is filled into the vacuum chamber at 0.9~1Pa, and the current + voltage control mode is adopted.

[0006] In some embodiments, [O]≤20 ppm and [N]≤60 ppm in the vacuum arc consumable electrode.

[0007] In some embodiments, during the arc starting stage, the current+voltage control mode includes: the current increases from 2KA to 18KA and then decreases to 15KA, and the voltage is 22-24V.

[0008] In some embodiments, during the smelting stage, the melting rate + droplet control mode includes: the melting rate is slowly reduced from 7.3 kg / min to 6.7 kg / min, and the droplet is 2.0-6.0 s -1 .

[0009] In some embodiments, during the feeding stage, the current+voltage control mode includes: the current is slowly reduced from 11KA to 6.5KA, and the voltage is 22-24V.

[0010] In some embodiments, during the feeding stage, the feeding melt rate is ≥ 2 kg / min.

[0011] In some embodiments, the arc starting phase time is controlled to be 110-120 minutes.

[0012] In some embodiments, the diameter of the vacuum arc consumable electrode is Φ810 mm to Φ820 mm.

[0013] In some embodiments, during molding, the pouring temperature is controlled to be 1530-1580°C.

[0014] The present invention also provides a 300M steel prepared by the above method, wherein the impurity element content of the 300M steel is: Al≤0.01%, TO≤0.0020%.

[0015] The present invention has at least the following beneficial technical effects: The method of the present invention can effectively improve the uniformity of Mn content in single vacuum low alloy ultra-high strength steel vacuum consumable ingots and the stability between batches, while taking into account the vacuum degassing capacity of the vacuum consumable process and the energy utilization efficiency of the smelting process. It solves the problem that the Mn content of the existing vacuum consumable ingots of medium and low alloy ultra-high strength steel is greatly different at the arc starting end and the feeding end, and the Mn content fluctuates greatly between batches of different furnaces, and even in severe cases, the Mn content exceeds the upper and lower control limits. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other embodiments can be obtained based on these drawings without paying creative work.

[0017] Figure 1 The present invention provides a schematic diagram of an embodiment of the pressure in the vacuum chamber and the control mode at each stage during vacuum arc consumable remelting. DETAILED DESCRIPTION

[0018] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the embodiments of the present invention are further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0019] The terms "including" and "having" and any variations thereof in the specification and claims of the present invention and the above-mentioned drawings are intended to cover non-exclusive inclusions; the terms "first", "second", etc. in the specification and claims of the present invention or the above-mentioned drawings are used to distinguish different objects rather than to describe a specific order. "Multiple" means two or more, unless otherwise clearly and specifically defined.

[0020] In addition, reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present invention. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0021] Based on the deficiencies of the prior art, the present invention improves the uniformity of the Mn content in the longitudinal direction of the vacuum consumable ingot, especially the uniformity of the Mn content at the head and tail of the vacuum consumable ingot, by controlling the vacuum degree of arc starting, smelting, and shrinkage feeding (hot capping) in the vacuum consumable process of medium and low alloy ultra-high strength steel. The stability of the Mn content of the vacuum consumable electrode of medium and low alloy ultra-high strength steel between batches is controlled, and the stability of the vacuum degree of the vacuum consumable remelting process is controlled at the same time to improve the volatility of the Mn content of the vacuum consumable ingot between different batches. The present invention can improve the uniformity of the Mn content of single vacuum medium and low alloy ultra-high strength steel and the stability between batches. At the same time, the vacuum degassing capacity of the vacuum consumable process and the energy utilization efficiency of the smelting process are taken into account.

[0022] The present invention provides a method for improving the stability and uniformity of Mn content in single vacuum 300M steel, wherein a vacuum arc consumable electrode is melted and cast through electric furnace melting, LF melting, VD melting, and die casting processes, and the Mn content in the electrode is controlled to be a Mn target composition* (1.33-1.54); During vacuum arc consumable remelting, In the arc starting stage, the vacuum degree adopts the extreme vacuum setting and the current + voltage control mode is adopted; During the melting stage, argon is filled into the vacuum chamber at 0.5-0.6 Pa, and the melting speed + droplet control mode is adopted; During the feeding stage, argon is filled into the vacuum chamber at 0.9~1Pa, and the current + voltage control mode is adopted.

[0023] Furthermore, [O]≤20ppm and [N]≤60ppm in the vacuum arc consumable electrode are controlled.

[0024] like Figure 1 The figure shows the pressure in the vacuum chamber and the control mode settings at each stage during vacuum arc consumable remelting. Specifically, In the arc starting stage, the vacuum degree adopts the extreme vacuum setting, and the current + voltage control mode includes: the current increases from 2KA to 18KA and then decreases to 15KA, and the voltage is 22~24V.

[0025] During the melting stage, argon was filled into the vacuum chamber at 0.5-0.6 Pa. The melting rate + droplet control mode included: the melting rate was slowly reduced from 7.3 kg / min to 6.7 kg / min, and the droplet was 2.0-6.0 s -1 .

[0026] During the feeding stage, argon is filled into the vacuum chamber at 0.9~1Pa, and the current + voltage control mode includes: the current is slowly reduced from 11KA to 6.5KA, and the voltage is 22~24V.

[0027] In some embodiments, during the feeding stage, the feeding melt rate is ≥ 2 kg / min.

[0028] In some embodiments, the arc starting phase time is controlled to be 110-120 minutes.

[0029] In some embodiments, the diameter of the vacuum arc consumable electrode is Φ810 mm to Φ820 mm.

[0030] In some embodiments, during molding, the pouring temperature is controlled to be 1530-1580°C.

[0031] The advantages of the present invention are: a method for ensuring that the Mn content of medium-low alloy ultra-high strength steel vacuum consumable ingots is stable and consistent between different furnace batches, and a method for ensuring that the Mn content of the vacuum consumable ingots is uniform at the longitudinal head and tail (arcing end and feeding end).

[0032] Specifically, this approach involves the following two aspects: 1) By controlling the stability of the Mn content of vacuum consumable electrodes for medium and low alloy ultra-high strength steel prepared by the EBT+LF+VD+MC process between batches, and controlling the stability of the melting rate and vacuum degree during the vacuum consumable remelting process, the volatility of the Mn content of vacuum consumable ingots between different batches can be improved. At the same time, the gas content in the vacuum arc consumable electrode can be reduced as much as possible, reducing the difficulty of stabilizing the pressure in the vacuum chamber during vacuum arc consumable remelting (VAR) melting.

[0033] 2) By controlling the vacuum degree in the three stages of arc starting, melting and feeding during the vacuum consumable process of medium and low alloy ultra-high strength steel, the uniformity of Mn content in the longitudinal direction of the vacuum consumable ingot is improved, especially the uniformity of Mn content at the arc starting end and the feeding end of the vacuum consumable ingot.

[0034] The above two methods can improve the uniformity of Mn content and batch-to-batch stability of single vacuum low alloy ultra-high strength steel, while taking into account the vacuum degassing capacity of the vacuum self-consumption process and the energy utilization efficiency of the smelting process.

[0035] The present invention will be further explained below in conjunction with specific embodiments.

[0036] Example 1 A method for improving the stability and uniformity of Mn content in single vacuum low alloy ultra-high strength steel, taking single vacuum preparation of low alloy ultra-high strength steel 300M (40Si2Ni2CrMoVA) as an example, specifically includes the following steps: 1) Low-medium alloy ultra-high strength steel 300M (40Si2Ni2CrMoVA) is melted by EBT+LF+VD+MC process to produce vacuum arc consumable electrode. The Mn content in the electrode is controlled at 1.1-1.15%, the gas content [O] is 15ppm, and [N] is 58ppm. Casting of Φ820mm vacuum arc consumable electrode.

[0037] 2) When smelting medium and low alloy ultra-high strength steel 300M (40Si2Ni2CrMoVA) steel Φ910mm ingot by vacuum arc consumable remelting (VAR), the vacuum degree in the arc starting stage adopts the limit vacuum setting, the current + voltage control mode is adopted, the arc starting stage time is 110min, the current increases from 2KA to 18KA and then decreases to 15KA, and the voltage is 22-24V; 3) In the normal melting stage, fill the vacuum chamber with argon 0.5Pa, adopt the melting speed + droplet control mode, the melting speed is slowly reduced from 7.3kg / min to 6.7kg / min, and the droplet is 2.0-6.0 s -1 ; 4) In the feeding stage, 0.9Pa of argon is filled into the vacuum chamber, and the current + voltage control mode is adopted. The current is slowly reduced from 11KA to 6.5KA, and the voltage is 22-24V. At the beginning of the feeding stage, the weight of the consumable electrode is 1100kg, the feeding melting rate is ≥2kg / min, and the end weight is 100kg.

[0038] The results of testing the Mn content at the arc starting end and the feeding end of the vacuum arc consumable electrode and the vacuum arc consumable remelting ingot are shown in Table 1.

[0039] Example 2 A method for improving the stability and uniformity of Mn content in single vacuum low alloy ultra-high strength steel, taking single vacuum preparation of low alloy ultra-high strength steel 300M (40Si2Ni2CrMoVA) as an example, specifically includes the following steps: 1) Low-medium alloy ultra-high strength steel 300M (40Si2Ni2CrMoVA) is melted by EBT+LF+VD+MC process to produce vacuum arc consumable electrode. The Mn content in the electrode is controlled at 1.05-1.10%, the gas content [O] is 16ppm, and [N] is 56ppm. Casting of Φ820mm vacuum arc consumable electrode.

[0040] 2) When smelting medium and low alloy ultra-high strength steel 300M (40Si2Ni2CrMoVA) steel Φ910mm ingot by vacuum arc consumable remelting (VAR), the vacuum degree in the arc starting stage adopts the limit vacuum setting, the current + voltage control mode is adopted, the arc starting stage time is 110min, the current increases from 2KA to 18KA and then decreases to 15KA, and the voltage is 22-24V; 3) In the normal melting stage, fill the vacuum chamber with argon at 0.55Pa, adopt the melting speed + droplet control mode, the melting speed is slowly reduced from 7.3kg / min to 6.7kg / min, and the droplet is 2.0-6.0 s -1 ; 4) In the feeding stage, argon is filled into the vacuum chamber at 0.95Pa, and the current + voltage control mode is adopted. The current is slowly reduced from 11KA to 6.5KA, and the voltage is 22-24V. At the beginning of the feeding stage, the weight of the consumable electrode is 1100kg, the feeding melting rate is ≥2kg / min, and the end weight is 100kg.

[0041] The results of testing the Mn content at the arc starting end and the feeding end of the vacuum arc consumable electrode and the vacuum arc consumable remelting ingot are shown in Table 1.

[0042] Example 3 A method for improving the stability and uniformity of Mn content in single vacuum low alloy ultra-high strength steel, taking single vacuum preparation of low alloy ultra-high strength steel 300M (40Si2Ni2CrMoVA) as an example, specifically includes the following steps: 1) Low-medium alloy ultra-high strength steel 300M (40Si2Ni2CrMoVA) is melted by EBT+LF+VD+MC process to produce vacuum arc consumable electrode. The Mn content in the electrode is controlled at 1.0-1.05%, the gas content [O] is 15ppm, and [N] is 58ppm. Casting of Φ810mm vacuum arc consumable electrode.

[0043] 2) When smelting low-alloy ultra-high strength steel 300M (40Si2Ni2CrMoVA) steel Φ920mm ingot by vacuum arc consumable remelting (VAR), the vacuum degree in the arc starting stage adopts the limit vacuum setting, the current + voltage control mode is adopted, the arc starting stage time is 110min, the current increases from 2KA to 18KA and then decreases to 15KA, and the voltage is 22-24V; 3) In the normal melting stage, 0.6Pa of argon is filled into the vacuum chamber, and the melting rate + droplet control mode is adopted. The melting rate is slowly reduced from 7.3kg / min to 6.7kg / min, and the droplet is 2.0-6.0 s -1 ; 4) In the feeding stage, 1Pa of argon is filled into the vacuum chamber, and the current + voltage control mode is adopted. The current is slowly reduced from 11KA to 6.5KA, and the voltage is 22-24V. At the beginning of the feeding stage, the weight of the consumable electrode is 1100kg, the feeding melting rate is ≥2kg / min, and the end weight is 100kg.

[0044] The results of testing the Mn content at the arc starting end and the feeding end of the vacuum arc consumable electrode and the vacuum arc consumable remelting ingot are shown in Table 1.

[0045] Comparative Example 1 The single vacuum preparation of medium-low alloy ultra-high strength steel 300M (40Si2Ni2CrMoVA) is used as a comparative example, and the specific operation steps include the following: 1) Low-medium alloy ultra-high strength steel 300M (40Si2Ni2CrMoVA) is melted by EBT+LF+VD+MC process. The Mn content in the electrode is controlled at 1.2-1.4%, the gas content [O] is 22ppm, and [N] is 65ppm. Casting Φ810mm vacuum arc consumable electrode.

[0046] 2) When vacuum arc consumable remelting (VAR) is used to melt medium and low alloy ultra-high strength steel 300M (40Si2Ni2CrMoVA) steel Φ920mm ingots, the extreme vacuum setting is used in the arc starting-normal smelting-shrinkage stage, and the actual pressure range in the melting vacuum chamber is 0.12-0.23Pa. The current + voltage control mode is adopted in the arc starting stage. The arc starting stage time is 110min. The current increases from 2KA to 18KA and then decreases to 15KA. The voltage is 22-24V; in the normal melting stage, the melting speed + droplet control mode is adopted. The melting speed is slowly reduced from 7.3kg / min to 6.7kg / min, and the droplet is 2.0-6.0 s -1 ; In the feeding stage, the current + voltage control mode is adopted, and the current is slowly reduced from 11KA to 6.5KA, and the voltage is 22-24V. At the beginning of the feeding stage, the weight of the consumable electrode is 1100kg, the feeding melting rate is ≥2kg / min, and the end weight is 100kg.

[0047] The results of testing the Mn content at the arc starting end and the feeding end of the vacuum arc consumable electrode and the vacuum arc consumable remelting ingot are shown in Table 1.

[0048] Comparative Example 2 The single vacuum preparation of medium-low alloy ultra-high strength steel 300M (40Si2Ni2CrMoVA) is used as a comparative example, and the specific operation steps include the following: 1) Low-medium alloy ultra-high strength steel 300M (40Si2Ni2CrMoVA) is melted by EBT+LF+VD+MC process. The Mn content in the electrode is controlled at 1.2-1.4%. The gas content [O] is 25ppm, [N] is 70ppm. Casting Φ810mm vacuum arc consumable electrode.

[0049] 2) When vacuum arc consumable remelting (VAR) is used to melt medium and low alloy ultra-high strength steel 300M (40Si2Ni2CrMoVA) steel Φ920mm ingots, the extreme vacuum setting is used in the arc starting-normal smelting-shrinkage stage, and the actual pressure range in the melting vacuum chamber is 0.15-0.35Pa. The current + voltage control mode is adopted in the arc starting stage. The arc starting stage time is 110min. The current increases from 2KA to 18KA and then decreases to 15KA. The voltage is 22-24V; in the normal melting stage, the melting speed + droplet control mode is adopted. The melting speed is slowly reduced from 7.3kg / min to 6.7kg / min, and the droplet is 2.0-6.0 s -1 ; In the feeding stage, the current + voltage control mode is adopted, and the current is slowly reduced from 11KA to 6.5KA, and the voltage is 22-24V. At the beginning of the feeding stage, the weight of the consumable electrode is 1100kg, the feeding melting rate is ≥2kg / min, and the end weight is 100kg.

[0050] The results of testing the Mn content at the arc starting end and the feeding end of the vacuum arc consumable electrode and the vacuum arc consumable remelting ingot are shown in Table 1.

[0051] Table 1 Mn content of 300M steel electrode and consumable ingot arc starting end and feeding end in Examples 1-3 and Comparative Examples 1-2

[0052] In comparison with Table 1, it can be clearly found that the difference in Mn content between the arc starting end and the feeding end of the vacuum consumable ingot in Example 1-3 is smaller than that in Comparative Example 1-2, and the fluctuation of Mn content between different furnace batches is smaller. At the same time, the Mn yield of Example 1-3 is relatively higher than that of Comparative Example 1-2.

[0053] The above is a detailed introduction to a method provided by the present invention for reducing the longitudinal and transverse performance differences of medium and low alloy ultra-high strength steel bars. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present invention, the present invention can also be improved and modified in a number of ways, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

[0054] On the other hand, the present invention further provides a 300M steel prepared by the above method, wherein the impurity element content of the 300M steel is: Al≤0.01%, TO≤0.0020%.

[0055] The above are exemplary embodiments disclosed in the present invention, but it should be noted that various changes and modifications may be made without departing from the scope disclosed in the embodiments of the present invention as defined in the claims. The functions, steps and / or actions of the method claims according to the disclosed embodiments described herein do not need to be performed in any particular order. In addition, although the elements disclosed in the embodiments of the present invention may be described or required in individual form, they may also be understood as multiple unless explicitly limited to the singular.

[0056] It should be understood that, as used herein, the singular forms "a", "an" are intended to include the plural forms as well, unless the context clearly supports an exception. It should also be understood that, as used herein, "and / or" refers to any and all possible combinations including one or more of the associated listed items.

[0057] The serial numbers of the embodiments disclosed in the above embodiments of the present invention are only for description and do not represent the advantages or disadvantages of the embodiments.

[0058] A person skilled in the art should understand that the discussion of any of the above embodiments is only exemplary and is not intended to imply that the scope of the disclosure of the embodiments of the present invention (including the claims) is limited to these examples; under the concept of the embodiments of the present invention, the technical features in the above embodiments or different embodiments can also be combined, and there are many other changes in different aspects of the above embodiments of the present invention, which are not provided in detail for the sake of simplicity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiments of the present invention should be included in the protection scope of the embodiments of the present invention.

Claims

1. A method for improving the stability and uniformity of Mn content in single vacuum 300M steel, characterized in that: The vacuum arc consumable electrode is melted and cast through electric furnace melting, LF melting, VD melting and die casting processes, and the Mn content in the electrode is controlled to be the Mn target composition* (1.33-1.54); During vacuum arc consumable remelting, In the arc starting stage, the vacuum degree adopts the extreme vacuum setting and the current + voltage control mode is adopted; During the melting stage, argon is filled into the vacuum chamber at 0.5-0.6 Pa, and the melting speed + droplet control mode is adopted; During the feeding stage, argon is filled into the vacuum chamber at 0.9~1Pa, and the current + voltage control mode is adopted.

2. The method for improving the stability and uniformity of Mn content in single vacuum 300M steel according to claim 1, characterized in that: Control [O]≤20ppm, [N]≤60ppm in vacuum arc consumable electrode.

3. The method for improving the stability and uniformity of Mn content in single vacuum 300M steel according to claim 1, characterized in that: In the arc starting stage, the current+voltage control mode includes: the current increases from 2KA to 18KA and then decreases to 15KA, and the voltage is 22~24V.

4. The method for improving the stability and uniformity of Mn content in single vacuum 300M steel according to claim 1, characterized in that: In the smelting stage, the melting rate + droplet control mode includes: the melting rate is slowly reduced from 7.3 kg / min to 6.7 kg / min, and the droplet is 2.0~6.0 s -1 .

5. The method for improving the stability and uniformity of Mn content in single vacuum 300M steel according to claim 1, characterized in that: In the feeding stage, the current+voltage control mode includes: the current slowly decreases from 11KA to 6.5KA, and the voltage is 22~24V.

6. The method for improving the stability and uniformity of Mn content in single vacuum 300M steel according to claim 1, characterized in that: During the shrinkage feeding stage, the shrinkage melting rate is ≥2kg / min.

7. The method for improving the stability and uniformity of Mn content in single vacuum 300M steel according to claim 1, characterized in that: The arc starting stage time is controlled to be 110~120min.

8. The method for improving the stability and uniformity of Mn content in single vacuum 300M steel according to claim 1, characterized in that: The diameter of the vacuum arc consumable electrode is Φ810mm~Φ820mm.

9. The method for improving the stability and uniformity of Mn content in single vacuum 300M steel according to claim 1, characterized in that: During mold casting, the pouring temperature is controlled at 1530~1580℃.

10. A 300M steel prepared by the method according to any one of claims 1 to 9, characterized in that: The impurity element content of the 300M steel is: Al≤0.01%, TO≤0.0020%.

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