High-nitrogen plastic mold steel and preparation method thereof

Abstract

The application discloses a high-nitrogen plastic mold steel, which comprises the following components: C with a mass percentage of 0.28-0.33%, Si with a mass percentage of 0.25-0.38%, Mn with a mass percentage of 0.4-0.8%, Cr with a mass percentage of 14.5-15.5%, Mo with a mass percentage of 0.9-1%, N with a mass percentage of 0.095-0.115%, P with a mass percentage of less than or equal to 0.02%, S with a mass percentage of less than or equal to 0.003%, and O with a mass percentage of less than or equal to 0.0025%. The method for protecting atmosphere electroslag remelting the high-nitrogen plastic mold steel can ensure the nitrogen content of the plastic mold steel and improve the comprehensive characteristics of the plastic mold steel, for example, the setting parameters of the slag system and the filling ratio can ensure that the crystallized steel ingot is dense, the material is uniform, and non-metallic inclusions can be removed well; the N charging flow rate in the remelting process can keep the balance between the furnace atmosphere and the N content in the molten steel, and can ensure that the N content deviation of the whole steel ingot is small and consistent with the parent material before remelting.

Description

Technical Field

[0001] This invention relates to the field of metallurgical processing technology, and in particular to a high-nitrogen plastic mold steel and its preparation method. Background Technology

[0002] High-nitrogen plastic mold steel is a new type of engineering material that has emerged in recent years. The addition of nitrogen improves the strength and corrosion resistance of the plastic mold steel. To better meet industry requirements, it is necessary to further improve the overall characteristics of the material, such as purity and uniformity.

[0003] Therefore, how to improve the overall characteristics of high-nitrogen plastic molds while ensuring the nitrogen content has become an urgent technical problem to be solved. Summary of the Invention

[0004] The purpose of this invention is to provide a high-nitrogen plastic mold steel and its preparation method, which can improve its overall characteristics while ensuring the nitrogen content in the high-nitrogen plastic mold.

[0005] To achieve the above objectives, the present invention provides a high-nitrogen plastic mold steel, which comprises the following components by mass percentage: 0.28-0.33% C, 0.25-0.38% Si, 0.4-0.8% Mn, 14.5-15.5% Cr, 0.9-1% Mo, 0.095-0.115% N, ≤0.02% P, ≤0.003% S, and ≤0.0025% O.

[0006] Optionally, the size of the non-metallic inclusions in the high-nitrogen plastic mold steel is 1-3 μm.

[0007] This invention also provides a method for preparing high-nitrogen plastic mold steel, the method comprising:

[0008] Obtain the refined electrode rod;

[0009] Electroslag ingots are obtained by remelting the refined electrode rods in a protective atmosphere electroslag furnace.

[0010] The electroslag ingot is subjected to demolding, annealing and forging treatment to obtain high-nitrogen plastic mold steel;

[0011] The high-nitrogen plastic mold steel comprises the following components by mass percentage: 0.28-0.33% C, 0.25-0.38% Si, 0.4-0.8% Mn, 14.5-15.5% Cr, 0.9-1% Mo, 0.095-0.115% N, ≤0.02% P, ≤0.003% S, and ≤0.0025% O.

[0012] Optionally, obtaining the refined electrode rod includes:

[0013] The initial electrode rod was prepared using an electric arc furnace + LF + VOD process;

[0014] N-Cr is added to adjust the N content of the initial electrode rod to obtain a refined electrode rod.

[0015] Optionally, the N-Cr comprises: 8.5-9% N by mass, 0.02-0.025% P by mass, 0.015-0.02% S by mass, 0.02-0.025% C by mass, and 0.8-0.9% Si by mass.

[0016] Optionally, the slag material in the electroslag remelting furnace includes: a slag system of pre-melted slag with a CaF2:Al2O3 mass ratio of 7:3; and Al particles and Ca-Si powder added to the mixed slag.

[0017] Optionally, the refined electrode rod is Electrode rod, the high-nitrogen plastic mold steel is round steel;

[0018] Correspondingly, the slag volume is 105±5kg; 43-48g of Al particles and 170-220g of Ca-Si powder are added to the mixed slag.

[0019] Optionally, generate the The conditions for electroslag remelting of round steel bars include: before powering on, the electroslag furnace is first charged with nitrogen for 12-15 minutes, with the nitrogen purity being 97% and the nitrogen flow rate being 55-70 L / min; the pressure swing setting range is 4.0-1.0V; the melting rate setting range is 7.0-5.5 kg / min; the filling time is 50-70 min; and the furnace cooling time is 50-60 min.

[0020] Optionally, the size of the non-metallic inclusions in the high-nitrogen plastic mold steel is 1-3 μm.

[0021] The technical effects and advantages of this invention are as follows:

[0022] This invention provides a high-nitrogen plastic mold steel, which comprises the following components by mass percentage: 0.28-0.33% C, 0.25-0.38% Si, 0.4-0.8% Mn, 14.5-15.5% Cr, 0.9-1% Mo, 0.095-0.115% N, ≤0.02% P, ≤0.003% S, and ≤0.0025% O.

[0023] This invention employs a protective atmosphere electroslag remelting method for high-nitrogen plastic mold steel, which improves its overall characteristics while maintaining the nitrogen content in the high-nitrogen plastic mold. For example, the settings of the slag system (CaF2:Al2O3 mass ratio of 7:3) and the filling ratio (diameter ratio of electrode rod to round steel) ensure dense crystallization of the steel ingot, uniform material composition and microstructure, and effectively remove non-metallic inclusions. The nitrogen flow rate during the remelting process maintains a balance between the furnace atmosphere and the nitrogen content in the molten steel, ensuring minimal deviation in the nitrogen content of the entire ingot and consistency with the pre-remelting base material.

[0024] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention can be realized and obtained by means of the structures pointed out in the description and the drawings. Attached Figure Description

[0025] Figure 1 A flowchart illustrating the preparation method of high-nitrogen plastic mold steel;

[0026] Figure 2 This is a dimensional diagram of non-metallic inclusions. Detailed Implementation

[0027] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Furthermore, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0028] It should be noted that the structures, proportions, sizes, etc., illustrated in the accompanying drawings are merely for illustrative purposes to aid those skilled in the art and to facilitate understanding and reading. They are not intended to limit the scope of the invention and therefore have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, without affecting the effectiveness and purpose of the invention, should still fall within the scope of the technical content disclosed herein. Furthermore, the terms "upper," "lower," "left," "right," "middle," and "one" used in this specification are merely for clarity and not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0029] High-nitrogen plastic mold steel is a new type of engineering material that has emerged in recent years. The addition of nitrogen improves the strength and corrosion resistance of the plastic mold steel. To better meet industry requirements, it is necessary to further improve the overall characteristics of the material, such as purity and uniformity.

[0030] Therefore, how to improve the overall characteristics of high-nitrogen plastic molds while ensuring the nitrogen content has become an urgent technical problem to be solved.

[0031] To address the aforementioned technical problems, this invention discloses a high-nitrogen plastic mold steel, comprising the following components: 0.28-0.33% C by mass, 0.25-0.38% Si by mass, 0.4-0.8% Mn by mass, 14.5-15.5% Cr by mass, 0.9-1% Mo by mass, 0.095-0.115% N by mass, ≤0.02% P by mass, ≤0.003% S by mass, and ≤0.0025% O by mass.

[0032] This invention employs a protective atmosphere electroslag remelting method for high-nitrogen plastic mold steel, which improves the overall characteristics of the plastic mold steel while ensuring the nitrogen content in the high-nitrogen plastic mold.

[0033] To better understand this solution, the following provides a detailed explanation of high-nitrogen plastic mold steel.

[0034] A high-nitrogen plastic mold steel, comprising the following components by mass percentage: 0.28-0.33% C, 0.25-0.38% Si, 0.4-0.8% Mn, 14.5-15.5% Cr, 0.9-1% Mo, 0.095-0.115% N, ≤0.02% P, ≤0.003% S, and ≤0.0025% O.

[0035] Preferably, the mass percentage of P is 0.013%, the mass percentage of S is 0.002%, and the mass percentage of O is 0.0016%.

[0036] The size of non-metallic inclusions in the high-nitrogen plastic mold steel is ≤10µm, preferably 1-3µm.

[0037] This invention also provides a method for preparing high-nitrogen plastic mold steel, which is described below in conjunction with... Figure 1 This paper provides a detailed introduction to the preparation method of high-nitrogen plastic mold steel.

[0038] A method for preparing high-nitrogen plastic mold steel, the method comprising: obtaining a refined electrode rod; remelting the refined electrode rod in a protective atmosphere electroslag furnace to obtain an electroslag ingot; and subjecting the electroslag ingot to demolding, annealing, and forging treatments to obtain high-nitrogen plastic mold steel.

[0039] To more clearly describe the process, the following will use the final high-nitrogen plastic mold steel as an example. The example of round steel is used for illustration.

[0040] 1. Refined electrode rod controlled nitrogen method

[0041] (1) Electrode rods were smelted using an electric arc furnace + LF + VOD process. After VOD reduction, N-Cr was added to adjust the N content, ensuring stable control of the N content while reducing the content of harmful elements P, S, and O. The components of N-Cr are shown in Table 1.

[0042] Table 1. Composition and content of N-Cr

[0043]

[0044] (2) Casting The composition control range of the electrode rod is shown in Table 2.

[0045] Table 2 Electrode rod composition content table

[0046]

[0047] 2. Protective atmosphere electroslag furnace remelting of electroslag ingots

[0048] (1) Electrode rod preparation

[0049] Annealing, grinding, sawing the riser, welding, and then keeping it ready for use.

[0050] (2) Slag preparation

[0051] Slag system: CaF2:Al2O3 = 70:30 (%) pre-melted slag; slag amount 105±5kg; mixed slag with 43-48g of Al particles and 170-220g of Ca-Si powder to ensure slag system stability.

[0052] (3) Electroslag remelting

[0053] Refining Electrode rod remelting For electroslag ingots, it is necessary to ensure stable control of the nitrogen content during the remelting process. Specific methods include:

[0054] Before powering on, the electroslag furnace is first charged with nitrogen for 12-15 minutes to purge the air inside the furnace. The nitrogen purity requirement is 97%, and the flow rate is 55-70 L / min. Nitrogen is used for the entire smelting process. Other remelting parameters are set as shown in Table 3.

[0055] Table 3 Remelting Parameters

[0056]

[0057] (4) After demolding, the electroslag ingot is sent for red annealing.

[0058] (5) After annealing, the electroslag ingot is transferred to the forging workshop for further processing. round steel

[0059] 3. Performance inspection of finished round steel bars

[0060] The N content in the feed portion of the electroslag ingot forged finished round steel is uniform and the purity is high.

[0061] (1) Uniformity of N content, with a control target of 0.095 to 0.115, as shown in Table 4.

[0062] Table 4. Ni content in the feed section of round steel.

[0063]

[0064] (2) Purity control, such as Figure 2 As shown. Since smaller sizes of non-metallic inclusions are better, therefore, according to Figure 2 It can be seen that the size of the non-metallic inclusions is already very small, meeting the standard.

[0065] (3) Content of harmful elements: P content 0.013, S content 0.002, O content 0.0016.

[0066] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing high-nitrogen plastic mold steel, characterized in that, The method includes: The refined electrode rods were obtained, including: The initial electrode rod was prepared using an electric arc furnace + LF + VOD process; The N content of the initial electrode rod is adjusted by adding N-Cr to obtain a refined electrode rod. The components of the N-Cr include: N with a mass percentage of 8.5-9%, P with a mass percentage of 0.02-0.025%, S with a mass percentage of 0.015-0.02%, C with a mass percentage of 0.02-0.025%, and Si with a mass percentage of 0.8-0.9%. Electroslag ingots are obtained by remelting the refined electrode rods in a protective atmosphere electroslag furnace. The conditions for electroslag furnace remelting include: purging the electroslag furnace with nitrogen for 12-15 minutes before power supply, wherein the purity of the nitrogen is 97% and the flow rate of the nitrogen is 55-70 L / min; the pressure swing setting range is 4.0-1.0 V; the melting rate setting range is 7.0-5.5 kg / min; the filling time is 50-70 min; and the furnace cooling time is 50-60 min. The electroslag ingot is subjected to demolding, annealing and forging treatment to obtain high-nitrogen plastic mold steel; The high-nitrogen plastic mold steel comprises the following components by mass percentage: 0.28-0.33% C, 0.25-0.38% Si, 0.4-0.8% Mn, 14.5-15.5% Cr, 0.9-1% Mo, 0.095-0.115% N, ≤0.02% P, ≤0.003% S, and ≤0.0025% O. The size of the non-metallic inclusions in the high-nitrogen plastic mold steel is 1-3 μm.

2. The method for preparing high-nitrogen plastic mold steel according to claim 1, characterized in that, The slag material in the electroslag remelting furnace includes: a pre-melted slag system with a CaF2:Al2O3 mass ratio of 7:3; and Al particles and Ca-Si powder added to the mixed slag.

3. The method for preparing high-nitrogen plastic mold steel according to claim 2, characterized in that, The refined electrode rod is a φ400mm electrode rod, and the high-nitrogen plastic mold steel is a φ140-φ202mm round steel; Correspondingly, the slag volume is 105±5kg; 43-48g of Al particles and 170-220g of Ca-Si powder are added to the mixed slag.

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