Ti c-based non-magnetic alloy, preparation and application

Abstract

This invention provides a TiC-based non-magnetic alloy, its preparation, and its application. The TiC-based non-magnetic alloy comprises, by weight percentage: Ni 25–40 wt%, Cr 5.5–8.6 wt%, Mo 2.5–4.0 wt%, C 0.8–1.3%, TiC 46–66 wt%, and other unavoidable trace impurities. The TiC-based non-magnetic alloy comprises TiC, Ni, Cr, Mo, and C, with appropriate proportions of each component, resulting in low magnetic properties, high hardness, high wear resistance, high-temperature performance, oxidation resistance, and corrosion resistance. Furthermore, the hard phase uses TiC, which has a low self-lubricating coefficient, and excludes WC. Therefore, the TiC-based non-magnetic alloy has a uniform grain size distribution, good internal stress consistency, and is less prone to cracking and deformation, extending its service life and demonstrating good product stability.

Description

Technical Field

[0001] This invention relates to the field of powder metallurgy, and more particularly to TiC-based nonmagnetic alloys, their preparation, and applications. Background Technology

[0002] Because the molding dies for producing magnetic materials require the use of non-magnetic materials, non-magnetic steels such as 1Cr18Ni9Ti, 70Mn, and 9Mn9 have traditionally been used as non-magnetic mold materials. However, non-magnetic steels have poor wear resistance, low hardness, and short service life. Moreover, after a period of use, the inner wall of the mold suffers severe scratches and deformation, which in turn affects the dimensional accuracy and surface quality of the magnetic materials.

[0003] Non-magnetic cemented carbides offer significant advantages in the powder metallurgy industry for molding dies and sealing rings used to form strongly magnetic powders. They possess high hardness and wear resistance, prevent powder sticking during molding, and improve the corrosion resistance of sealing rings. Most common non-magnetic cemented carbides are WC-Ni based, such as YN14, which is a specialized type. However, WC-Ni based non-magnetic cemented carbides are prone to cracking and deformation during use. Summary of the Invention

[0004] The main objective of this invention is to provide a TiC-based non-magnetic alloy, its preparation, and its application, in order to solve the technical problem that conventional non-magnetic hard alloys are prone to cracking and deformation.

[0005] To achieve the above objectives, the present invention provides a TiC-based nonmagnetic alloy comprising, by weight percentage: Ni 25-40 wt%, Cr 5.5-8.6 wt%, Mo 2.5-4.0 wt%, C 0.8-1.3%, TiC 46-66 wt%, and other unavoidable trace impurities.

[0006] According to the embodiments of this application, the composition by weight percentage includes: Ni 25-40 wt%, Cr 5.5-8.6 wt%, Mo 2.5-4.0 wt%, C 0.8-1.3%, other unavoidable trace impurities, and the balance being TiC.

[0007] According to an embodiment of this application, the metallographic structure of the TiC-based nonmagnetic alloy includes a two-phase region of TiC phase and Ni-Mo-Cr phase; wherein the proportion of TiC phase is 46-66% and the proportion of Ni-Mo-Cr phase is 35-40%.

[0008] According to embodiments of this application, the TiC-based nonmagnetic alloy has a hardness of 85–89 HRA and a density of 5.80–6.30 g / cm³. 3 .

[0009] This invention also provides a method for preparing a TiC-based nonmagnetic alloy, comprising the following steps:

[0010] The TiC, Ni, Cr, and Mo raw materials, corresponding to the weight percentages of the aforementioned TiC-based nonmagnetic alloy, are mixed and then wet-milled to obtain a wet-milled slurry.

[0011] The wet grinding slurry is granulated to obtain a raw material.

[0012] The blank is pressed into shape to obtain a preform.

[0013] The TiC-based nonmagnetic alloy is obtained by sintering the preform, wherein the vacuum degree is 3 Pa to 300 Pa and the sintering temperature is 1350 °C to 1450 °C during the sintering process.

[0014] According to an embodiment of this application, in the wet milling step, the wet milling medium is anhydrous ethanol, and the molding agent is PEG. The ratio of anhydrous ethanol added is 0.4–0.5 L / kg. The wet milling time is 30–45 hours.

[0015] According to an embodiment of this application, the molding agent is added at a ratio of 2.5% to 3.0%. The PEG includes PEG4000 and PEG1500. The mass ratio of PEG4000 to PEG1500 is 2:1 to 3:1.

[0016] According to an embodiment of this application, the following step is further included between the wet milling step and the granulation step:

[0017] The wet grinding slurry was filtered through a 235-mesh filter.

[0018] According to an embodiment of this application, the granulation method of the granulation step is spray drying, wherein the drying outlet temperature is 90-95°C and the particle size of the preform is 0.40-0.43 mm.

[0019] The present invention also provides an application of the above-mentioned TiC-based non-magnetic alloy or the above-prepared TiC-based non-magnetic alloy in forming molds and hot press welding heads.

[0020] The aforementioned TiC-based non-magnetic alloy comprises TiC, Ni, Cr, Mo, and C, with a suitable ratio of each component. This results in the TiC-based non-magnetic alloy exhibiting low magnetism, high hardness, high wear resistance, high-temperature performance, oxidation resistance, and corrosion resistance. Furthermore, the hard phase uses TiC, which has a low self-lubricating coefficient, and excludes WC. Consequently, the TiC-based non-magnetic alloy exhibits uniform grain size distribution, good internal stress consistency, and is less prone to cracking and deformation, thus extending its service life and demonstrating good product stability. Attached Figure Description

[0021] 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 some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0022] Figure 1 This is a typical 100X metallographic photograph of the TiC-based nonmagnetic alloy of Example 3 of this application;

[0023] Figure 2 This is a typical 1500X metallographic photograph of the TiC-based nonmagnetic alloy of Example 3 of this application.

[0024] The realization of the objective, functional characteristics and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] It should be noted that all directional indicators (such as up, down, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0027] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature.

[0028] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0029] In response to the problem of cracking and deformation that easily occurs in WC-Ni series non-magnetic cemented carbides during use, the applicant has conducted extensive research.

[0030] For example, in the non-magnetic alloy manufacturing method proposed in the existing patent "Non-magnetic Hard Alloy and Preparation Method" CN201010261626.x, nickel is added: 8% to 15%; chromium carbide: 0.5% to 1.5%; tungsten carbide: balance.

[0031] The applicant's research revealed that in WC-Ni non-magnetic cemented carbides, the WC grains tend to grow and coarsen during the manufacturing process, resulting in uneven grain size distribution and poor internal stress consistency. Therefore, molds produced using this material are prone to cracking and deformation during use due to inconsistent internal stress.

[0032] Based on this, embodiments of this application provide a TiC-based nonmagnetic alloy comprising, by weight percentage: Ni 25–40 wt%, Cr 5.5–8.6 wt%, Mo 2.5–4.0 wt%, C 0.8–1.3%, TiC 46–66 wt%, and other unavoidable trace impurities.

[0033] Ni itself has a certain degree of corrosion resistance and can resist chloride ion stress corrosion.

[0034] Cr and Mo interact with nickel atoms, suppressing electron spin flipping and reducing the alloy's magnetism.

[0035] Carbon in the matrix can form carbides with Cr and Mo, which helps to improve sintering wettability.

[0036] The aforementioned TiC-based nonmagnetic alloy comprises TiC, Ni, Cr, Mo, and C, with appropriate proportions of each component. This results in a TiC-based nonmagnetic alloy exhibiting low magnetic properties, high hardness, high wear resistance, high-temperature performance, oxidation resistance, and corrosion resistance. Furthermore, the hard phase utilizes TiC, which has a low self-lubricating coefficient, and excludes WC grains. Compared to WC grains, TiC grains are less prone to growth during the preparation process. Therefore, the aforementioned TiC-based nonmagnetic alloy exhibits uniform grain size distribution, good internal stress consistency, and is less prone to cracking and deformation, thus extending its service life and demonstrating good product stability.

[0037] In some embodiments, by weight percentage, it includes: Ni 33-35 wt%, Cr 7.0-8.0 wt%, Mo 3.0-4.0 wt%, C 0.8-1.3%, TiC 53-55 wt%, and other unavoidable trace impurities.

[0038] Under these conditions, the TiC-based non-magnetic alloy exhibits a more uniform grain size distribution and better internal stress consistency, further reducing the probability of cracking and deformation. This can extend the service life of the TiC-based non-magnetic alloy and improve product stability.

[0039] In some embodiments, the metallographic structure of the TiC-based nonmagnetic alloy comprises a two-phase region of TiC phase and Ni-Mo-Cr phase; wherein the proportion of TiC phase is 46-66% and the proportion of Ni-Mo-Cr phase is 35-40%.

[0040] Carbon balance calculations show that the alloy has a two-phase structure with no free carbon and no third phase.

[0041] In some embodiments, the TiC-based nonmagnetic alloy has a hardness of 85–89 HRA and a density of 5.80–6.30 g / cm³. 3 Furthermore, the porosity of TiC-based nonmagnetic alloys is less than that of A04B02.

[0042] This TiC-based non-magnetic alloy has high hardness and high wear resistance, and can be used to make molds for forming magnetic materials or to process silicon steel sheets for transformers. Molds made from this non-magnetic alloy have improved performance and are less prone to problems such as scratches and deformation, thus effectively improving the size and surface quality of the products.

[0043] During the research process, the applicant also discovered that WC cemented carbide has a relatively high density (15.6 g / cm³). 3 Because TiC is not suitable for producing larger products, the TiC-based non-magnetic alloy of this application has the advantage of low individual weight due to the low density of TiC (4.92-4.93 g / cm3).

[0044] This invention also provides a method for preparing a TiC-based nonmagnetic alloy, comprising the following steps:

[0045] S100: The TiC raw materials, Ni raw materials, Cr raw materials and Mo raw materials corresponding to the weight percentage of the above-mentioned TiC-based non-magnetic alloy are mixed and wet-milled to obtain a wet-milled slurry.

[0046] In this step, since the elemental content of the TiC-based non-magnetic alloy does not vary significantly from the content of the raw materials used to prepare it, the proportions of TiC, Ni, Cr, and Mo raw materials can be prepared with reference to the composition of the TiC-based non-magnetic alloy, i.e., by weight percentage: Ni 25–40 wt%, Cr 5.5–8.6 wt%, Mo 2.5–4.0 wt%, C 0.8–1.3%, other unavoidable trace impurities, and the balance being TiC. The process of weighing and mixing the above-proportioned TiC, Ni, Cr, and Mo raw materials can be called batching.

[0047] TiC, Ni, Cr, and Mo raw materials are collectively referred to as preparation raw materials. Specific requirements do not need to be specified for the particle size of each preparation raw material, such as centimeter-level or micrometer-level.

[0048] Specifically, in order to facilitate subsequent wet milling to the required particle size, in some embodiments, the TiC, Ni, Cr, and Mo raw materials are in powder form.

[0049] To better ensure the quality of TiC-based nonmagnetic alloys, in some embodiments, the technical requirements for TiC, Ni, Cr, and Mo raw materials are as follows:

[0050] Technical requirements for TiC powder: Ti≥79%, combined carbon≥19.0%, Fisher particle size: 1μm-5μm.

[0051] Technical requirements for Ni powder: Ni ≥ 99.5%, O ≤ 0.5%, Fe ≤ 0.03%.

[0052] Technical requirements for Cr powder: Cr ≥ 99.0%, Fe ≤ 0.02%.

[0053] Technical requirements for Mo powder: Mo ≥ 99.0%, O ≤ 0.5%, Fe ≤ 0.03%.

[0054] The raw materials are wet-milled, such as in a ball mill, to further refine the particle size of TiC, Ni, Cr and Mo raw materials and to mix them evenly, thus obtaining a wet-milled slurry.

[0055] S200: Granulate the wet slurry to obtain the raw material.

[0056] In this step, there are no specific requirements for the granulation method of the wet grinding slurry; it is sufficient to make the wet grinding slurry into fine particles.

[0057] S300: Press the blank into shape to obtain a preform.

[0058] In this step, the billet is weighed and placed in a mold of the target shape (e.g., for preparing a forming mold, the mold shape is a forming mold; for preparing a hot press welding head, the mold shape is a hot press welding head). A flat scraper can be used to scrape the material, ensuring that the billet is uniform in all parts, and the unit pressing pressure is not less than 1.5 t / cm. 2 .

[0059] S400: TiC-based nonmagnetic alloy is obtained by sintering a preform, wherein the vacuum degree is 3Pa~300Pa and the sintering temperature is 1350℃~1450℃ during the sintering process.

[0060] In this step, the preform is vacuum sintered, such as in a vacuum furnace. During the vacuum sintering process, the vacuum level in the vacuum furnace should be controlled between 3 Pa and 300 Pa. In some embodiments, the vacuum level in the vacuum furnace should be controlled between 3 Pa and 30 Pa.

[0061] The compact is placed in a boat and then sintered in a vacuum furnace. In some embodiments, the contact material between the boat and the compact is sprayed zirconium oxide or magnesium oxide particles. The specific sintering temperature is 1350℃~1450℃. In some embodiments, the optimal sintering temperature is 1360℃~1380℃. The heating rate during the dewaxing stage is ≤0.5℃ / min, and the heating rate during the sintering stage is ≤1.5℃ / min. The resulting TiC-based nonmagnetic alloy is used to prepare products such as forming molds or hot-press welding heads.

[0062] When the products prepared from TiC-based non-magnetic alloys have high requirements, they can be further processed. For example, in some embodiments, the surface is ground to achieve a flatness within 0.3 mm. For instance, after clamping the product with a fixture, the surface is ground to achieve a flatness within 0.3 mm.

[0063] The above-described method for preparing TiC-based non-magnetic alloys, due to the appropriate composition and proportions of the product, and through a suitable sintering process, yields TiC-based non-magnetic alloy products with low magnetism, high hardness, high wear resistance, high-temperature performance, oxidation resistance, and corrosion resistance. Furthermore, TiC-based non-magnetic alloy products are less prone to cracking and deformation, have a long service life, good product stability, and low individual weight.

[0064] In some embodiments, the wet milling medium is anhydrous ethanol. The molding agent is PEG. The ratio of anhydrous ethanol added is 0.4–0.5 L / kg. The wet milling time is 30–45 hours.

[0065] In the wet grinding process, anhydrous ethanol is added as the grinding medium, with an anhydrous ethanol content of ≥99.0% and a specific gravity ≤0.82 g / cm³. The amount of anhydrous ethanol added in the wet grinding process is 0.40–0.5 L / kg. PEG (polyethylene glycol) molding agent is used. The proportion of anhydrous ethanol added is calculated based on the total mass of TiC, Ni, Cr, and Mo raw materials. In some embodiments, Gr15 bearing steel rods are used as the grinding carrier. The hardness of the grinding balls in the ball mill is HRA87-89.

[0066] In some embodiments, the addition ratio of molding agent is 2.5-3.0%. PEG includes PEG4000 and PEG1500. When PEG4000 molding agent has a larger molecular number and is added in combination with PEG1500 at a mass ratio of 2:1 to 3:1, the best effect can be achieved, resulting in high compact strength.

[0067] The PEG addition ratio is calculated based on the total mass of TiC, Ni, Cr, and Mo raw materials, i.e., the PEG addition mass is 2.5% to 3.0% of the total mass. The specific wet milling time is 30 to 45 hours.

[0068] In order to remove oversized particles from the wet milling slurry, in some embodiments, the wet milling slurry is further filtered through a 235-mesh screen between the wet milling step and the granulation step.

[0069] In some embodiments, the granulation step is performed by spray drying, wherein the drying outlet temperature is 90–95°C and the particle size of the preform is 0.40–0.43 mm.

[0070] Spray drying has high granulation efficiency, and the spray-formed preforms are spherical with regular shape and good particle size uniformity.

[0071] The present invention also provides an application of the above-mentioned TiC-based non-magnetic alloy or the above-prepared TiC-based non-magnetic alloy in forming molds and hot press welding heads.

[0072] The technical solution of this application will be described below with reference to specific embodiments.

[0073] Example

[0074] Several powders, including TiC raw material (TiC powder), Ni raw material (Ni powder), Mo raw material (Mo powder), Cr raw material (Cr powder), and C raw material (C black), were prepared according to the requirements in Table 1 at a certain weight percentage (i.e., wt%, the same in the following examples). A Gr15 steel rod was used as the grinding media, and a PEG forming agent was used, with PEG4000 accounting for 75% and PEG1500 accounting for 25% of the PEG forming agent composition. Wet grinding was performed using anhydrous alcohol as the medium, followed by spray drying granulation. The spray outlet temperature was controlled at 90-95℃. After drying, the particle size of the mixture was 100-150μm, and the particle flowability was 30-42S / 25cm. 3 Loose packing density: 1.5 ± 0.5 g / cm³ 3 Then, the material is pressed and shaped, and finally sintered and processed in one piece to obtain a TiC-based cemented carbide with a smooth surface and no deformation. The wet grinding process parameters for each embodiment are shown in Table 2, the sintering parameters are shown in Table 3, and the properties of the obtained TiC-based non-magnetic alloy are shown in Table 4, which are compared with 50Mn18Cr4WN.

[0075] The typical metallographic structure of Example 3 is as follows: Figure 1 , Figure 2 .

[0076] Table 1. Raw material ratios (wt%) for each example

[0077] TiC Mo Ni Cr C Black Example 1 66 2.6 25 5.5 margin Example 2 60 3.0 30 6.5 margin Example 3 54 3.4 34 7.4 margin Example 4 46 4.1 40 8.6 margin Example 5 54 3.4 34 7.4 margin Example 6 54 3.4 34 7.4 margin Comparative Example 1 54 3.4 34 7.4 margin Comparative Example 2 54 3.4 34 7.4 margin Comparative Example 3 - - 11 Chromium carbide 0.75 WC balance

[0078] Table 2 Sintering parameters for each embodiment

[0079] Sintering temperature (°C) Insulation time (h) Contact materials Example 1 1450 2 Zirconia Example 2 1410 2 Zirconia Example 3 1380 2 Magnesium oxide particles Example 4 1360 2 Magnesium oxide particles Example 5 1350 2 Magnesium oxide particles Example 6 1370 2 Magnesium oxide particles Comparative Example 1 1470 2 Magnesium oxide particles Comparative Example 2 1300 2 Magnesium oxide particles Comparative Example 3 1470 1 -

[0080] Table 3 Wet milling process parameters for each embodiment

[0081]

[0082] Table 4. Properties of TiC-based nonmagnetic alloys prepared in each embodiment.

[0083]

[0084] As shown in Table 4, the TiC-based nonmagnetic alloys prepared using this application exhibit high dimensional accuracy and a density of 6.0–6.20 g / cm³. 3 Rockwell hardness HRA 87.2, flexural strength 1500MPa, and tested magnetic permeability ≤1.33×10⁻⁶. -6 H / m. Generally, the permeability requirement for non-magnetic steel is ≤1.3×10⁻⁶. -6 The permeability of the TiC-based non-magnetic alloy produced by this invention (H / m) meets the permeability requirements of non-magnetic steel.

[0085] Application Examples

[0086] Copper materials were processed using molds made from the materials listed in Table 5. The number of times each mold was used, the number of times it was repaired, and the usage status were recorded.

[0087] Table 5 Comparison of copper processing lifespan in an electronics processing plant

[0088] Product Name Number of times used Number of mold repairs 50Mn18Cr4WN 1000～1500 2 KD20 non-magnetic alloy Approximately 10,000 times 1 Implementation Example 3 Approximately 9000 times 0

[0089] As shown in Table 5, the service life of the TiC-based non-magnetic alloy of this application is nearly 6 times that of non-magnetic steel, which is significantly improved and comparable to that of imported material KD20. This is because this patent contains about 50-55% TiC. Since the round TiC forms non-metallic contact with the friction surface during operation, it has an extremely low coefficient of friction, thereby eliminating cold welding, avoiding adhesive wear and abrasive wear, and ensuring a smooth finish without the need for mold repair.

[0090] In summary, the TiC-based non-magnetic alloy of this application has low density, good wear resistance, and its magnetic permeability meets the requirements of non-magnetic steel.

[0091] The above technical solutions of the present invention are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made under the technical concept of the present invention using the contents of the present invention specification and drawings, or direct / indirect applications in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A TiC-based nonmagnetic alloy, characterized in that, By weight percentage: Ni 33~35 wt%, Cr 7.0~8.0 wt%, Mo 3.0~4.0 wt%, C 0.8~1.3%, TiC 53%~55 wt%, and other unavoidable trace impurities; The microstructure of the TiC-based nonmagnetic alloy comprises a two-phase region of TiC phase and Ni-Mo-Cr phase; wherein the TiC phase accounts for 46-66% and the Ni-Mo-Cr phase accounts for 35-40%; The TiC-based nonmagnetic alloy has a hardness of 85-89 HRA and a density of 5.80-6.30 g / cm³. 3 .

2. A method for preparing a TiC-based nonmagnetic alloy, characterized in that, Includes the following steps: The TiC raw materials, Ni raw materials, Cr raw materials and Mo raw materials, corresponding to the weight percentage of the TiC-based nonmagnetic alloy described in claim 1, are mixed and wet-milled to obtain a wet-milled slurry; The wet grinding slurry is granulated to obtain a raw material; The blank is pressed into a shape to obtain a preform; The TiC-based nonmagnetic alloy is obtained by sintering the preform, wherein the vacuum degree is 3 Pa to 300 Pa and the sintering temperature is 1350 °C to 1450 °C during the sintering process.

3. The preparation method according to claim 2, characterized in that, In the wet milling step, the wet milling medium is anhydrous alcohol and the molding agent is PEG; wherein, the proportion of anhydrous alcohol added is 0.4~0.5L / kg; and the wet milling time is 30~45 hours.

4. The preparation method according to claim 3, characterized in that, The molding agent is added at a ratio of 2.5-3.0%; the PEG includes PEG4000 and PEG1500; the mass ratio of PEG4000 to PEG1500 is 2:1-3:

1.

5. The preparation method according to claim 2, characterized in that, Between the wet milling step and the granulation step, the following is also included: The wet grinding slurry was filtered through a 235-mesh filter.

6. The preparation method according to any one of claims 2 to 5, characterized in that, The granulation method in the granulation step is spray drying, wherein the drying outlet temperature is 90~95℃ and the particle size of the preform is 0.40~0.43mm.

7. The application of a TiC-based nonmagnetic alloy according to claim 1 or a TiC-based nonmagnetic alloy prepared according to any one of claims 2 to 5 in forming molds and hot press welding heads.

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