A cast ultra-fine grain structure alloy material and method and use thereof

Abstract

The application discloses a kind of casting ultrafine grain structure alloy material and method and application, belong to metal material casting technical field, the method steps are as follows: (1) smelting catalysis: alloy steel raw material smelting, synchronous application axial static magnetic field and electron beam array array bombardment, make charged particle in alloy steel liquid spiral motion trajectory;(2) casting cooperation: steel liquid is poured into mould under magnetic field agitation, plasma treatment, ultrasonic treatment and microseismic;(3) interval interval quenching: after casting, mould temperature reaches preset value time interval spray liquid nitrogen quenching cooling;(4) magnetic field heat treatment: casting is demoulded and carries out two-stage stress relief;First stage stress relief is no magnetic field heating, and second stage stress relief is under the action of magnetic field cooling;(5) natural air cooling to room temperature can be used.The application can obtain ultrafine grain directly in casting stage, need not subsequent mechanical deformation, grain size is above ASTM 13.5 level, and can be used for complex structure casting near net shape forming.

Description

Technical Field

[0001] This invention belongs to the field of metal material casting technology, specifically relating to a casting method and application of an ultrafine-grained alloy material. Background Technology

[0002] Near-net-shape forming is a modern manufacturing process that integrates new material research and development, computer simulation, precision mold design, and advanced mechanical manufacturing technology. Its core lies in precisely controlling various parameters during the material forming process to make the part closer to its "net size" after forming. This achieves near-finished product requirements in terms of geometric dimensions and surface accuracy, thereby significantly reducing or even completely eliminating subsequent machining processes, significantly improving material utilization, and lowering production costs. Currently, most ultrafine crystalline steel preparation technologies rely on post-processing deformation, which cannot meet the near-net-shape forming requirements of complex parts.

[0003] For example, CN100482839C discloses a method for manufacturing ultrafine-grained steel, the steps of which are as follows: smelting according to the following composition, by weight percentage: C 0.02%-0.20%, Nb 0.01%-0.10%, Si 0.80%, Mn 1.0%-2.0%, Ti The ferrite grains are 0.008%-0.025% and Als≤0.020%, etc.; casting, with a pouring temperature ≤Tm+20℃, adding nucleating agents during the casting process, and a steel cooling rate ≥180℃ / min, resulting in a billet grain size of less than 15μm; rolling, heating to above Ac3, then cooling at a rate ≥10℃ / s to near the Ar3 point temperature, performing continuous non-recrystallization controlled rolling, with a cumulative reduction rate ≥80% and a pass reduction rate ≥15%; cooling at a rate ≥10℃ / s to below 450℃, then naturally air-cooling to room temperature, achieving ultrafine ferrite grains and obtaining ferrite grains <3.0μm. This invention requires rolling deformation to induce strain-induced dynamic phase transformation in austenite.

[0004] CN106884116A discloses an ultrafine-grained black iron and its preparation method. By adding Mn and Cr elements to adjust the proportion of Y108 black iron composition, ultrafine Y108 black iron without coarse grain rings is obtained through steps such as melting and casting, hot extrusion molding, heat treatment, stretching and straightening, sawing, and testing. The average grain size of the ultrafine Y108 black iron is less than 30μm. However, this invention achieves fine grains through reverse extrusion, which is a mechanical deformation refinement and cannot be used for complex castings.

[0005] CN103388109A discloses a 500MPa grade ultrafine-grained engineering machinery steel and its manufacturing method, comprising the following composition by weight percentage: C: 0.04-0.08%; Si: 0.1-0.3%; Mn: 1.6-1.75%; P: ≤0.015%; S: ≤0.005%; Nb: 0.035-0.07%; Cr: 0.25-0.45%; Ti: 0.007-0.018%; N: ≤0.007%; O: ≤0.003%; the remainder being iron and impurities. The steel is manufactured by controlling the furnace exit temperature, the second-stage rolling temperature, the thickness, the final rolling temperature, and the final cooling temperature. This invention relies on Nb-Ti microalloying and controlled rolling and cooling, requiring rolling deformation.

[0006] Therefore, developing a casting ultrafine-grained alloy material that achieves ultrafine grain refinement directly during the casting process is of great significance for near-net-shape forming of complex structural castings in aerospace, shipbuilding, rail transportation, road transportation, metallurgy, and engineering machinery. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a casting method for ultrafine-grained alloy materials and their applications.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for casting ultrafine-grained alloy steel materials, comprising the following steps: (1) Melting catalysis: Alloy steel raw materials are melted to 1550-1600℃, and an axial static magnetic field and an electron beam array are applied simultaneously to bombard the molten steel, so that the charged particles in the molten steel move in a spiral trajectory. (2) Casting coordination: Molten steel is poured into the mold under magnetic field agitation, plasma treatment, ultrasonic treatment and micro-vibration; (3) Intermittent rapid cooling: After casting is completed, when the mold temperature reaches the preset value, liquid nitrogen is sprayed intermittently to rapidly cool down to 270-330℃; (4) Magnetic field heat treatment: After the casting is demolded, it undergoes two-stage stress relief; The first stage of stress relief involves heating to 550-600℃ without a magnetic field and holding at that temperature for 2-4 hours, with the heating rate not exceeding 80℃ / h.

[0009] The second stage of stress relief involves cooling the temperature to 270-330℃ under the influence of a magnetic field; the strength of the magnetic field is 0.1-1.5T.

[0010] (5) Allow it to cool naturally to room temperature.

[0011] In some embodiments, the alloy steel raw material described in step (1) comprises the following components by mass percentage: C 0.04-0.6%, Si 0.2-4.0%, Mn 0.3-14%, Cr 0.2-28%, Mo 0.1-5%, V 0.05-1.5%, with the balance being Fe.

[0012] Preferably, the alloy steel raw material comprises the following components by mass percentage: C 0.04-0.6%, Si 0.2-1.5%, Mn 0.5-1.8%, Cr 0.2-1.5%, Mo 0.1-1.5%, V 0.05-0.5%, with the balance being Fe.

[0013] More preferably, the alloy steel raw material comprises the following components by mass percentage: C 0.04-0.25%, Si 0.2-0.5%, Mn 1.2-1.8%, Cr 0.8-1.5%, Mo 0.2-0.4%, V 0.05-0.15%, with the balance being Fe.

[0014] More preferably, the alloy steel raw material comprises the following components by mass percentage: C 0.22%, Si 0.25%, Mn 1.35%, Cr 1.05%, Mo 0.28%, V 0.12%, with the balance being Fe. The strong magnetic configuration of the present invention can suppress melt convection and reduce dendrite growth rate; in some embodiments, the strength of the axial static magnetic field in step (1) is 0.1-10T. Preferably, the strength of the axial static magnetic field is 1-8T; more preferably, it is 1-5T.

[0015] This invention uses electron beam bombardment to generate vacancy clusters, compared to conventional casting (10 6 / cm³), nucleation density (approximately 10) 9 The power density ( / cm³) is significantly improved. In some embodiments, the energy of the electron beam in step (1) is 50-300 keV, and the power density is 0.1-3 MW / m³. 2 Preferably, the energy of the electron beam is 120-180 keV and the power density is 1-2 MW / m². 2 .

[0016] In some embodiments, the magnetic field direction of the axial static magnetic field in step (1) is at a certain angle to the electron beam, and the angle is not parallel or antiparallel. Preferably, the angle is 80-100°, more preferably 85-95°; more preferably 90°.

[0017] This invention utilizes a magnetic field to break up nascent dendrite arms, thereby reducing grain size. In some embodiments, the magnetic field in step (2) is an alternating magnetic field; preferably, the strength of the magnetic field is 0.1-5T and the frequency is 5-100Hz; more preferably, the strength of the magnetic field is 0.5-1.5T and the frequency is 5-20Hz; even more preferably, the strength is 1-1.4T and the frequency is 12-18Hz.

[0018] In some implementations, the plasma treatment in step (2) is: setting up a plasma flow orthogonally along the casting flow direction, and using the coupling of plasma and magnetic field to increase the melt undercooling.

[0019] Preferably, the power density of the plasma is 0.05-2 MW / m²; more preferably 0.08-1.5 MW / m², and even more preferably 0.1-0.5 MW / m².

[0020] Preferably, the working gas of the plasma is a mixture of argon and hydrogen or helium, wherein the volume fraction of hydrogen in the mixture is 1%-7%; more preferably 4%-6%; and even more preferably 4.5%-5.5%.

[0021] This invention utilizes ultrasonic treatment until the liquid alloy steel completes crystallization, promoting optimized solidification structure during the solidification process. Ultrasonic treatment in an electromagnetic environment significantly increases the equiaxed crystal ratio of alloy steel and heat-resistant steel (from 20% to 60% or even higher), improving alloy element segregation, promoting more uniform distribution of alloy elements and grain refinement, and achieving ultra-uniformity. In some embodiments, the power of ultrasonic treatment in step (2) is 200-800W; more preferably 300-600W.

[0022] The present invention utilizes micro-vibrations to promote the orderly arrangement of crystal lattices. In some embodiments, the micro-vibrations in step (2) are: amplitude 5-50 μm, frequency 50-1000 Hz, preferably amplitude 10-50 μm, frequency 100-800 Hz; more preferably amplitude 20-40 μm, frequency 100-500 Hz.

[0023] In some implementations, the mold in step (2) needs to be preheated before casting, and the preheating temperature is 270-440°C; preferably 300-400°C.

[0024] The intermittent quenching crystallization of the present invention can trigger heterogeneous nucleation. In some embodiments, the preset value in step (3) is: solidus line + (15-40)℃, the duration of the spray is 0.1-0.5s / time, the interval of the spray does not exceed 5s, and the quenching cooling rate is ≥100℃ / s.

[0025] Preferably, the preset value is: solidus line + (15-30)℃.

[0026] More preferably, the preset values ​​are: solidus line + (15-20)℃, the spray duration is 0.2-0.4s / time, the spray interval is 3-5s, and the quenching rate is ≥100℃ / s.

[0027] This invention utilizes a combination of first-stage stress relief dislocation density recovery and second-stage stress relief magnetostriction to eliminate micro-stress, thereby more thoroughly reducing the internal stress of the material and improving its stability. In some embodiments, the first-stage stress relief in step (4) is: heating to 570-590℃ without a magnetic field and holding at that temperature for 2.5-3.5h, wherein the heating rate is 30-60℃ / h.

[0028] In some implementations, the magnetic field in step (4) is an alternating magnetic field with a strength of 0.1-1T, preferably 0.1-0.5T, and more preferably 0.1-0.3T.

[0029] In some implementations, the cooling rate in step (4) is 75%-85% of the first-stage stress-relief heating rate; preferably 80%.

[0030] Secondly, the present invention provides a cast ultrafine-grained alloy material prepared by the above method.

[0031] The grain size of the cast ultrafine-grained alloy material described in this invention is ≥ASTM 13.5 grade, and the tensile strength is ≥1200MPa.

[0032] Preferably, the grain size of the cast ultrafine-grained alloy material is ≥ ASTM 14 grade.

[0033] Thirdly, the present invention provides the application of the above method in near-net-shape forming of structural castings.

[0034] The structural castings described in this invention are used in at least one of the following fields: aerospace, shipbuilding, rail transportation, road transportation, metallurgy, and engineering machinery.

[0035] The structural casting is a standard part and / or a non-standard part. In some embodiments, the structural casting is a non-standard part with a wall thickness difference > 10:1.

[0036] The structural castings include turbine housings for aero engines and / or integral die-cast parts for automobiles (e.g., steering knuckles, control arms, body structural components, chassis components).

[0037] The beneficial effects of this invention are as follows: (1) This invention increases the melt undercooling through magnetic field-particle coupling and the spiral motion trajectory of electrons; simultaneously, it links strong magnetism, plasma, ultrasound, micro-vibration, and inter-zone rapid cooling, with strong magnetism adjusting grain arrangement, micro-vibration promoting solute diffusion, and inter-zone rapid cooling inhibiting grain growth, achieving a grain size of 2.6-3.1 μm (>ASTM 13.5 grade). Compared with the prior art, this invention can directly obtain ultrafine grains in the casting stage without subsequent mechanical deformation.

[0038] (2) This invention is a single-process casting process with a simple technology. The average grain size of the cast ultrafine-grained alloy material is 2.6-3.1 μm, the tensile strength is ≥1200 MPa, and the fatigue life reaches 6.8 × 10⁻⁶. 6 More than once.

[0039] (3) The present invention can directly form complex parts, and can produce irregular parts with a wall thickness difference of >10:1 (such as aircraft turbine housings), with a machining allowance of ≤5% (compared to 30% in traditional casting), and a material utilization rate of 95%. It is suitable for near-net-shape forming of complex structural parts such as aerospace turbine housings and integrated die-cast parts for new energy vehicles. Attached Figure Description

[0040] Figure 1 The image shows the grain size metallographic diagram of the cast ultrafine-grained alloy material of Example 2. Detailed Implementation

[0041] The following description of the embodiments is merely to aid in understanding the method and core ideas of the present invention. It should be noted that those skilled in the art can make various modifications and improvements to the present invention without departing from its principles, and these modifications and improvements also fall within the scope of the claims. The following description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not limited to the embodiments shown herein, but can be applied to a wider scope consistent with the principles and novel features disclosed herein. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains.

[0042] The following describes embodiments and comparative examples of the present invention to provide a more detailed explanation of the casting method of the present invention. However, the present invention is not limited thereto. Unless otherwise specified, all percentages in the present invention are mass percentages.

[0043] Melt undercooling refers to the phenomenon that the actual crystallization temperature is lower than the theoretical crystallization temperature during the crystallization process of a molten metal; the temperature difference between the two is called undercooling.

[0044] Nucleation rate refers to the number of crystal nuclei formed per unit time and per unit volume.

[0045] The ASTM rating is based on GB / T6394-2017, "Method for determination of average grain size of metals".

[0046] This invention does not limit the source of the raw materials used. Unless otherwise specified, all raw materials used in this invention are commercially available products commonly used in this technical field. For example, the working gas of the plasma is a mixture of argon and hydrogen, wherein the volume fraction of hydrogen is 5%.

[0047] Examples 1-3 and Comparative Examples 1-5 A method for casting an ultrafine-grained alloy material, comprising the following steps: (1) Melting Catalysis: The alloy steel raw material is melted to 1550-1600℃, and simultaneously bombarded by an axial static magnetic field and an electron beam array, causing the charged particles in the alloy steel molten steel to move in a helical trajectory. Alloy steel raw materials, by mass percentage, include the following components: C 0.22%, Si 0.25%, Mn 1.35%, Cr 1.05%, Mo 0.28%, V 0.12%, balance Fe; The magnetic field direction of the axial static magnetic field and the angle between the electron beam are between 85° and 95°. (2) Co-processing of casting: Molten steel is poured into the mold under magnetic field agitation, plasma treatment, ultrasonic treatment and micro-vibration; The magnetic field is an alternating magnetic field; the plasma treatment is: the plasma flow is set orthogonally along the casting flow direction; the power of the ultrasonic treatment is 100-1000W; the micro-vibration is: amplitude 5-50μm, frequency 10-100Hz.

[0048] (3) Adaptive intermittent rapid cooling crystallization: After casting is completed, when the mold temperature reaches the preset value, liquid nitrogen is sprayed intermittently to rapidly cool down to 300℃; The preset value is solidus + (15-40)℃, the spray duration is 0.1-0.5s, and the spray interval does not exceed 5s.

[0049] (4) Magnetic field heat treatment: After the casting is demolded, it undergoes two-stage stress relief; The first stage of stress relief is: heating to 550-600℃ without a magnetic field and holding for 2-4 hours, with a heating rate not exceeding 80℃ / h. The second stage of stress relief involves cooling the temperature to 300℃ under the influence of a magnetic field, with a cooling rate that is 75%-85% of the heating rate in the first stage of stress relief.

[0050] (5) Allow it to cool naturally to room temperature.

[0051] The specific process parameters for Examples 1-3 are shown in Table 1. The specific process parameters for Comparative Examples 1-4 are shown in Table 2.

[0052] Table 1

[0053] Table 2

[0054] The cast ultrafine-grained alloy materials prepared in Examples 1-3 and Comparative Examples 1-5 were tested.

[0055] Figure 1 The image shows the grain size metallographic diagram of the cast ultrafine-grained alloy material prepared in Example 2 of this invention. It indicates that the cast ultrafine-grained alloy material prepared in this invention can reach ASTM 14 grade, which belongs to ultrafine-grained alloy steel material. It has high strength and high toughness potential and can be used in scenarios with stringent mechanical performance requirements, such as high-end bearings and aerospace.

[0056] Table 3 shows the specific test results for each embodiment and comparative example.

[0057] Table 3

[0058] The results show that the grain size of the cast ultrafine-grained alloy material prepared by this invention is 2.6-3.1 μm, which meets or exceeds ASTM 13.5 grade; the tensile strength is >1200 MPa; the impact energy is >115 J; and the fatigue life reaches 6.8 × 10⁻⁶. 6 More than once.

[0059] Comparative Examples 1-5 show that in the casting process, process parameters such as the cooling rate of the second stage of stress relief in magnetic field heat treatment, the intensity and frequency of plasma and magnetic field in casting synergy, the electron beam in melting catalysis, and ultrasonic treatment have a significant impact on the grain size and mechanical properties of cast ultrafine-grained alloy materials.

[0060] This invention increases melt undercooling through magnetic field-particle coupling and the spiral motion trajectory of electrons. Simultaneously, it employs a coordinated approach involving strong magnetism, plasma, ultrasound, micro-vibration, and inter-stage rapid cooling. Strong magnetism adjusts grain arrangement, micro-vibration promotes solute diffusion, and inter-stage rapid cooling inhibits grain growth, achieving a grain size of 2.6-3.1 μm (>ASTM 13.5 grade). Compared to existing technologies, this invention can directly obtain ultrafine grains during the casting stage without subsequent mechanical deformation, achieving unexpected technical benefits.

[0061] The above description, in conjunction with specific embodiments, further illustrates the present invention. However, these embodiments are merely exemplary and do not constitute any limitation on the scope of the present invention. Those skilled in the art should understand that modifications or substitutions to the details and form of the technical solutions of the present invention can be made without departing from the spirit and scope of the invention, and all such modifications and substitutions fall within the protection scope of the present invention.

Claims

1. A method for casting an ultrafine-grained alloy material, characterized in that, The steps are as follows: (1) Melting catalysis: Alloy steel raw materials are melted to 1550-1600℃, and an axial static magnetic field and an electron beam array are applied simultaneously to bombard the alloy steel liquid, so that the charged particles in the alloy steel liquid have a spiral motion trajectory. (2) Casting coordination: Molten steel is poured into the mold under magnetic field agitation, plasma treatment, ultrasonic treatment and micro-vibration; The magnetic field is an alternating magnetic field; the plasma treatment is: the plasma flow is set orthogonally along the casting flow direction; the ultrasonic treatment power is 100-1000W; the micro-vibration is: amplitude 5-50μm, frequency 50-1000Hz; (3) Intermittent rapid cooling: After casting is completed, when the mold temperature reaches the preset value, liquid nitrogen is sprayed intermittently to rapidly cool down to 270-330℃; The preset value is solidus + (15-40)℃, the spraying duration is 0.1-0.5s, and the spraying interval does not exceed 5s; (4) Magnetic field heat treatment: After the casting is demolded, it undergoes two-stage stress relief; The first stage of stress relief involves heating to 550-600℃ without a magnetic field and holding at that temperature for 2-4 hours, with the heating rate not exceeding 80℃ / h. The second stage of stress relief involves cooling the temperature to 270-330℃ under the influence of a magnetic field. (5) Allow it to cool naturally to room temperature.

2. The method according to claim 1, characterized in that, The alloy steel raw material mentioned in step (1) includes the following components by mass percentage: C 0.04-0.6%, Si 0.2-4.0%, Mn 0.3-14%, Cr 0.2-28%, Mo 0.1-5%, V 0.05-1.5%, and balance Fe.

3. The method according to claim 1, characterized in that, The strength of the axial static magnetic field in step (1) is 0.1-10T, the energy of the electron beam is 50-300keV, and the power density is 0.1-3MW / m². 2 .

4. The method according to claim 1, characterized in that, The magnetic field strength in step (2) is 0.5-5T and the frequency is 5-100Hz.

5. The method according to claim 1, characterized in that, The power density of the plasma in step (2) is 0.08-2MW / m², and the working gas of the plasma is a mixture of argon and hydrogen or helium.

6. The method according to claim 5, characterized in that, The power of the ultrasonic treatment in step (2) is 200-800W; And / or the hydrogen gas mentioned in step (2) is 1%-7% of the volume of the mixed gas; And / or the mold described in step (2) needs to be preheated before casting, and the preheating temperature is 270-440℃.

7. The method according to claim 1, characterized in that, The magnetic field in step (4) is an alternating magnetic field with a strength of 0.1-1T.

8. Cast ultrafine-grained alloy material prepared by the method according to any one of claims 1-7.

9. The cast ultrafine-grained alloy material according to claim 8, characterized in that, The grain size of the cast ultrafine-grained alloy material is ≥ASTM 13.5 grade, and the tensile strength is ≥1200MPa.

10. The application of the method according to any one of claims 1-7 in near-net-shape forming of structural castings.

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