Preparation method of superfine titanium alloy spherical powder for injection molding

Abstract

The invention discloses a preparation method of superfine titanium alloy spherical powder for injection molding, which comprises the following steps of: 1, smelting titanium alloy to obtain a titanium alloy cast ingot; secondly, the titanium alloy cast ingot is subjected to hydrotreating, and a titanium hydride alloy material is obtained; thirdly, the titanium hydride alloy material is subjected to ball milling and crushing and then sieved, and titanium hydride alloy powder is obtained; fourthly, the titanium hydride alloy powder is subjected to dehydrogenation treatment, and hydrogenated and dehydrogenated titanium alloy powder is obtained; and fifthly, the hydrogenated and dehydrogenated titanium alloy powder is subjected to spheroidizing treatment, and the superfine titanium alloy spherical powder is obtained. According to the method, sufficient melting and uniform mixing of the raw materials are ensured through smelting, subsequent crushing is facilitated through hydrotreating, titanium hydride alloy powder is obtained through ball-milling crushing and sieving, hydrogen is removed through dehydrogenation treatment, spherical powder is formed through spheroidizing, the powder granularity is controllable, the fine powder yield is high, the material utilization rate is high, and the cost is low; the prepared titanium alloy powder is high in sphericity degree, good in fluidity and suitable for metal powder injection molding.

Description

Technical Field

[0001] The invention belongs to the technical field of powder metallurgy powder preparation, and in particular relates to a method for preparing ultrafine titanium alloy spherical powder for injection molding. Background Art

[0002] Titanium and titanium alloys, as a high-quality lightweight metal structural and functional material, have the advantages of low density, high specific strength, good biocompatibility, excellent corrosion resistance, non-magnetic, non-toxic, strong anti-damping performance, and good heat resistance. They have been widely used in aerospace, navigation, petroleum, chemical, metallurgy, automobile, power generation, biomedicine and other fields.

[0003] At present, the industrial product parts manufacturing industry is moving towards the goal of simplifying production processes, saving resources and reducing costs. In particular, in the design of key parts, it is more pursuing small (micro) size, high performance and multi-purpose structural functions. However, the high melting point and hardness of titanium and titanium alloys make their processing and cutting particularly difficult. Although traditional manufacturing processes such as machining, precision casting, die casting, stamping and powder metallurgy have their own characteristics, it is still difficult to fully achieve the design goals. With the advent and continuous development of metal injection molding technology, which is known as the "fifth generation metal forming process", it provides a new development direction for the mass production of complex structures, high precision, and miniature titanium alloy parts at a lower cost.

[0004] Titanium alloy powder particle size, sphericity, fluidity and other parameters play a key role in injection molding. Injection molding usually uses spherical fine powder with good fluidity (particle size less than 25μm). At present, the production methods of titanium alloy spherical powder at home and abroad mainly include atomization method (electrode induction melting gas atomization method, plasma rotating electrode atomization method, plasma torch atomization method) and radio frequency plasma spheroidization method. Among them, the titanium alloy spherical powder produced by atomization method has a fine powder yield of less than 20% of -25μm, and the material utilization rate is low; while the plasma spheroidization method has low production efficiency and high cost, and it is difficult to achieve large-scale production.

[0005] Therefore, a method for preparing ultrafine titanium alloy spherical powder for injection molding is needed. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a method for preparing ultrafine titanium alloy spherical powder for injection molding in view of the deficiencies of the above-mentioned prior art. The method ensures that the raw materials are fully melted and mixed evenly by smelting, facilitates subsequent crushing by hydrogenation treatment, obtains hydrogenated titanium alloy powder by ball milling and screening, removes hydrogen by dehydrogenation treatment, and forms spherical powder by spheroidization treatment. The powder particle size is controllable, the fine powder yield is high, the material utilization rate is high, the cost is low, the prepared titanium alloy powder has high sphericity and good fluidity, and is suitable for metal powder injection molding.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for preparing ultrafine titanium alloy spherical powder for injection molding, characterized in that the method comprises the following steps:

[0008] Step 1, titanium alloy smelting: the titanium alloy is batched, and then smelted in a vacuum induction suspension smelting furnace or a vacuum consumable arc furnace to obtain a titanium alloy ingot; the smelting temperature is 1700° C. to 1900° C., and the smelting is repeated 2 to 4 times, and the smelting time for each time is 2 hours to 4 hours;

[0009] Step 2: hydrogenation treatment: placing the titanium alloy ingot obtained in step 1 into a hydrogen furnace for hydrogenation treatment to obtain a hydrogenated titanium alloy material; the hydrogenation temperature is 600° C. to 700° C., and the time is 3 h to 6 h;

[0010] Step 3, crushing and screening: the titanium hydride alloy material obtained in step 2 is crushed by ball milling under the protection of inert gas, and then sieved to obtain titanium hydride alloy powder; the ball-to-material ratio in the ball milling is 4 to 6:1, and the ball milling time is 15h to 25h;

[0011] Step 4: Reduction and dehydrogenation: the hydrogenated titanium alloy powder obtained in step 3 is placed in a vacuum furnace for dehydrogenation treatment to obtain hydrogenated dehydrogenated titanium alloy powder; the dehydrogenation temperature is 550° C. to 650° C., and the time is 3 h to 6 h;

[0012] Step 5: Spheroidization treatment: The hydrogenated dehydrogenated titanium alloy powder obtained in step 4 is spheroidized in a selective laser sintering device to obtain ultrafine titanium alloy spherical powder; the parameters of the spheroidization treatment are: a reciprocating scanning strategy is adopted, the powder layer thickness is 20 μm to 40 μm, the laser power is 500 W to 700 W, and the scanning speed is 30 mm·s -1 ~60mm·s -1 , the pass spacing is 200μm~400μm.

[0013] The present invention ensures that the titanium alloy raw material is fully melted by controlling the smelting temperature, and ensures that the titanium alloy raw material is fully mixed and uniformly by controlling the number and time of smelting to obtain a titanium alloy ingot with uniform composition. By performing hydrogenation treatment, highly brittle titanium hydride is obtained, which is convenient for subsequent crushing. By performing ball milling crushing and screening, a titanium hydride alloy powder with a particle size of less than 25 μm is obtained, and preliminary crushing is achieved to provide conditions for subsequent spheroidization treatment. By performing dehydrogenation treatment, hydrogen in the titanium alloy is removed to obtain irregular titanium alloy fine powder. By performing spheroidization treatment in a selective laser sintering device, the irregular titanium alloy powder is melted under the action of a laser beam, and after the laser beam leaves, the molten droplet is rapidly cooled to form a spherical powder. In addition, by controlling the parameters of the spheroidization treatment, insufficient melting or excessive melting and bonding of the powder is prevented, and sufficient spheroidization of the powder is ensured to obtain an ultrafine titanium alloy spherical powder.

[0014] The above-mentioned method for preparing ultrafine titanium alloy spherical powder for injection molding is characterized in that the titanium alloy in step 1 is TC4, TA7 or Ti-Al-Mo-Zr series titanium alloy. The present invention is applicable to preparing ultrafine titanium alloy spherical powder for injection molding from titanium alloys of various components.

[0015] The above-mentioned method for preparing ultrafine titanium alloy spherical powder for injection molding is characterized in that the titanium alloy ingot is crushed into blocks with a particle size of less than 2 cm or turned into chips before the hydrogenation treatment in step 2. The present invention shortens the hydrogenation time and improves the hydrogenation effect by crushing into blocks or turning into chips before hydrogenation treatment.

[0016] The above-mentioned method for preparing ultrafine titanium alloy spherical powder for injection molding is characterized in that the particle size of the hydrogenated titanium alloy powder in step three satisfies: D90≤25μm; the coarse powder obtained by screening is subjected to secondary ball milling and then sieving. The present invention controls the particle size of the hydrogenated titanium alloy powder to ensure the subsequent successful acquisition of ultrafine titanium alloy spherical powder, and improves the utilization rate of the material and reduces the preparation cost by subjecting the coarse powder obtained by sieving to secondary ball milling and then sieving, and the parameters of the secondary ball milling are the same as those of the first ball milling.

[0017] The above-mentioned method for preparing ultrafine titanium alloy spherical powder for injection molding is characterized in that the vacuum degree in the dehydrogenation treatment in step 4 is less than 1 Pa. The present invention ensures the effect of the dehydrogenation treatment by controlling the vacuum degree of the dehydrogenation treatment, prevents the introduction of impurities, and ensures the purity of the ultrafine titanium alloy spherical powder.

[0018] The above-mentioned method for preparing ultrafine titanium alloy spherical powder for injection molding is characterized in that the spheroidization treatment in step 5 is carried out under argon protection, and the oxygen content in the working chamber of the selective laser sintering equipment is less than 600ppm. The present invention prevents oxidation of the material by carrying out the spheroidization treatment under argon protection and controlling the oxygen content in the working chamber of the selective laser sintering equipment, thereby ensuring the purity of the ultrafine titanium alloy spherical powder.

[0019] The above-mentioned method for preparing ultrafine titanium alloy spherical powder for injection molding is characterized in that the ultrafine titanium alloy spherical powder in step 5 is used for metal powder injection molding. The ultrafine titanium alloy spherical powder prepared by the present invention has a small particle size and is suitable for metal powder injection molding, and is suitable for producing titanium alloy parts with complex structure, high precision and miniature size.

[0020] The above-mentioned method for preparing ultrafine titanium alloy spherical powder for injection molding is characterized in that the particle size of the ultrafine titanium alloy spherical powder in step 5 satisfies: D90≤30μm. The ultrafine titanium alloy spherical powder prepared by the present invention meets the ultrafine particle size requirement.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] 1. The present invention ensures that the titanium alloy raw material is fully melted by controlling the smelting temperature, and ensures that the titanium alloy raw material is fully mixed by controlling the number and time of smelting. Highly brittle titanium hydride is obtained by hydrogenation treatment, which is convenient for subsequent crushing. Hydrogenated titanium alloy powder with a particle size of less than 25 μm is obtained by ball milling and screening to achieve preliminary crushing. Hydrogen is removed by dehydrogenation treatment to obtain irregular titanium alloy fine powder. Spheroidization treatment is performed in a selective laser sintering device, and the irregular titanium alloy powder is formed into ultrafine titanium alloy spherical powder under the action of a laser beam. The powder particle size is controllable, the yield of fine powder of -30 μm is high, the material utilization rate is high, and the cost is low.

[0023] 2. The present invention combines hydrogenation, dehydrogenation and laser spheroidization to achieve ultrafine titanium alloy spherical powder with uniform composition, controllable particle size, good sphericity and high spheroidization rate. The cost of this method is lower than the current mainstream titanium alloy spherical powder production method, and solves the problems of low fine powder yield, low material utilization, complex equipment, low production efficiency and excessively high cost in the existing titanium alloy spherical powder preparation technology.

[0024] 3. The present invention adopts a vacuum induction suspension melting furnace or a vacuum consumable arc furnace for melting, the alloy composition is controllable, the applicability is strong, and various grades of titanium alloy powders can be prepared. After hydrogenation, crushing and dehydrogenation, titanium alloy powder with uniform composition and no segregation can be obtained.

[0025] 4. The present invention performs spheroidization treatment on irregular hydrogenated dehydrogenated titanium alloy powder in a selective laser sintering device, with a spheroidization rate of up to 80%, to obtain ultrafine titanium alloy spherical powder with high sphericity, high bulk density and good fluidity, which is suitable for titanium alloy powder injection molding.

[0026] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a morphology picture of the hydrogenated dehydrogenated titanium alloy powder obtained in step 4 of Example 1 of the present invention.

[0028] Figure 2 This is a morphology picture of the ultrafine titanium alloy spherical powder obtained in step five of Example 1 of the present invention. DETAILED DESCRIPTION

[0029] Example 1

[0030] This embodiment includes the following steps:

[0031] Step 1, titanium alloy smelting: the titanium alloy is prepared according to Ti-6Al-4V, and then smelted in a vacuum induction suspension smelting furnace at a smelting temperature of 1800°C, and the smelting is repeated 4 times, each smelting time is 2 hours, to obtain a titanium alloy ingot;

[0032] Step 2, hydrogenation treatment: the titanium alloy ingot obtained in step 1 is turned into chips, and then placed in a hydrogen furnace for hydrogenation treatment at a temperature of 600° C. for 6 hours to obtain a hydrogenated titanium alloy material;

[0033] Step 3, crushing and screening: the titanium hydride alloy material obtained in step 2 is ball-milled under inert gas protection, the ball-to-material ratio is 5:1, the ball-milling time is 20 hours, and then sieved, the coarse powder obtained by sieving is ball-milled for the second time and then sieved to obtain 600-mesh titanium hydride alloy powder;

[0034] Step 4, reduction dehydrogenation: the hydrogenated titanium alloy powder obtained in step 3 is placed in a vacuum furnace with a vacuum degree of less than 1 Pa for dehydrogenation treatment at a temperature of 550° C. for 6 hours to obtain hydrogenated dehydrogenated titanium alloy powder;

[0035] Step 5: Spheroidization: The hydrogenated dehydrogenated titanium alloy powder obtained in step 4 is spheroidized in a selective laser sintering device under argon protection, using a reciprocating scanning strategy, a powder layer thickness of 20 μm, a laser power of 700 W, and a scanning speed of 60 mm·s. -1 , the pass spacing is 200μm, and the oxygen content in the working chamber of the selective laser sintering equipment is lower than 600ppm, and ultrafine titanium alloy spherical powder is obtained.

[0036] After testing, the particle size of the ultrafine titanium alloy spherical powder prepared in this embodiment satisfies: D90≤28.4μm, the fine powder yield is greater than 60%, the powder particle size is stable, and the spheroidization degree is greater than 85%. The ultrafine titanium alloy spherical powder prepared in this example is used for metal powder injection molding, and the prepared feed has good fluidity, the density of the material after sintering is greater than 97.0%, and the surface finish is high.

[0037] Figure 1 The morphology of the hydrogenated dehydrogenated titanium alloy powder obtained in step 4 of this embodiment is shown in FIG. Figure 1 It can be seen that the hydrogenated dehydrogenated titanium alloy powder presents an irregular shape.

[0038] Figure 2 The morphology of the ultrafine titanium alloy spherical powder obtained in step 5 of this embodiment is shown in FIG. Figure 2 It can be seen that after laser spheroidization treatment, the ultrafine titanium alloy spherical powder is spherical as a whole, and only a small amount of powder has satellite balls or irregular shapes.

[0039] Example 2

[0040] This embodiment includes the following steps:

[0041] Step 1, titanium alloy smelting: the titanium alloy is prepared according to Ti-5Al-2.5Sn, and then smelted in a vacuum induction suspension smelting furnace at a smelting temperature of 1700°C, and the smelting is repeated twice, each smelting time is 4 hours, to obtain a titanium alloy ingot;

[0042] Step 2: hydrogenation treatment: the titanium alloy ingot obtained in step 1 is crushed into blocks, and then placed in a hydrogen furnace for hydrogenation treatment at a temperature of 700° C. for 3 hours to obtain a hydrogenated titanium alloy material;

[0043] Step 3, crushing and screening: the titanium hydride alloy material obtained in step 2 is ball-milled under inert gas protection, the ball-to-material ratio is 6:1, the ball-milling time is 15 hours, and then sieved, the coarse powder obtained by sieving is ball-milled for the second time and then sieved to obtain 600-mesh titanium hydride alloy powder;

[0044] Step 4, reduction dehydrogenation: the hydrogenated titanium alloy powder obtained in step 3 is placed in a vacuum furnace with a vacuum degree of less than 1 Pa for dehydrogenation treatment at a temperature of 650° C. for 3 hours to obtain hydrogenated dehydrogenated titanium alloy powder;

[0045] Step 5: Spheroidization: The hydrogenated dehydrogenated titanium alloy powder obtained in step 4 is spheroidized in a selective laser sintering device under argon protection, using a reciprocating scanning strategy, a powder layer thickness of 30 μm, a laser power of 600 W, and a scanning speed of 30 mm·s. -1, the pass spacing is 300μm, and the oxygen content in the working chamber of the selective laser sintering equipment is lower than 600ppm, obtaining ultrafine titanium alloy spherical powder.

[0046] After testing, the particle size of the ultrafine titanium alloy spherical powder prepared in this embodiment satisfies: D90≤29.8μm, the fine powder yield is greater than 65%, the powder particle size is stable, and the spheroidization degree is greater than 80%. The ultrafine titanium alloy spherical powder prepared in this example is used for metal powder injection molding, and the prepared feed has good fluidity, the density of the material after sintering is greater than 96.5%, and the surface finish is high.

[0047] Example 3

[0048] This embodiment includes the following steps:

[0049] Step 1, titanium alloy smelting: the titanium alloy is prepared according to Ti-3Al-3Mo-3Zr, pressed into blocks and welded into electrodes, and then smelted in a vacuum consumable arc furnace at a smelting temperature of 1900°C. The smelting is repeated 3 times, each smelting time is 3 hours, and a titanium alloy ingot is obtained;

[0050] Step 2, hydrogenation treatment: the titanium alloy ingot obtained in step 1 is crushed into blocks, and then placed in a hydrogen furnace for hydrogenation treatment at a temperature of 650° C. for 4 hours to obtain a hydrogenated titanium alloy material;

[0051] Step 3, crushing and screening: the titanium hydride alloy material obtained in step 2 is ball-milled under inert gas protection, the ball-to-material ratio is 4:1, the ball-milling time is 25 hours, and then sieved, the coarse powder obtained by sieving is ball-milled for the second time and then sieved to obtain 600-mesh titanium hydride alloy powder;

[0052] Step 4, reduction dehydrogenation: the hydride titanium alloy powder obtained in step 3 is placed in a vacuum furnace with a vacuum degree of less than 1 Pa for dehydrogenation treatment at a temperature of 600° C. for 5 hours to obtain hydride dehydrogenated titanium alloy powder;

[0053] Step 5: Spheroidization: The hydrogenated dehydrogenated titanium alloy powder obtained in step 4 is spheroidized in a selective laser sintering device under argon protection, using a reciprocating scanning strategy, a powder layer thickness of 40 μm, a laser power of 500 W, and a scanning speed of 40 mm·s. -1 , the pass spacing is 400μm, and the oxygen content in the working chamber of the selective laser sintering equipment is lower than 600ppm, obtaining ultrafine titanium alloy spherical powder.

[0054] After testing, the particle size of the ultrafine titanium alloy spherical powder prepared in this embodiment meets the following conditions: D90≤27.0μm, the fine powder yield is greater than 60%, the powder particle size is stable, and the spheroidization degree is greater than 80%. The ultrafine titanium alloy spherical powder prepared in this embodiment is used for metal powder injection molding, and the prepared feed has good fluidity, and the material has high density and surface finish after sintering.

[0055] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent change made to the above embodiment according to the technical essence of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing ultrafine titanium alloy spherical powder for injection molding, characterized in that: The method comprises the following steps: Step 1, titanium alloy smelting: the titanium alloy is batched, and then smelted in a vacuum induction suspension smelting furnace or a vacuum consumable arc furnace to obtain a titanium alloy ingot; the smelting temperature is 1700° C. to 1900° C., and the smelting is repeated 2 to 4 times, and the smelting time for each time is 2 hours to 4 hours; Step 2: hydrogenation treatment: placing the titanium alloy ingot obtained in step 1 into a hydrogen furnace for hydrogenation treatment to obtain a hydrogenated titanium alloy material; the hydrogenation temperature is 600° C. to 700° C., and the time is 3 h to 6 h; Step 3, crushing and screening: the titanium hydride alloy material obtained in step 2 is crushed by ball milling under the protection of inert gas, and then sieved to obtain titanium hydride alloy powder; the ball-to-material ratio in the ball milling is 4 to 6:1, and the ball milling time is 15h to 25h; Step 4: Reduction and dehydrogenation: the hydrogenated titanium alloy powder obtained in step 3 is placed in a vacuum furnace for dehydrogenation treatment to obtain hydrogenated dehydrogenated titanium alloy powder; the dehydrogenation temperature is 550° C. to 650° C., and the time is 3 h to 6 h; Step 5: Spheroidization treatment: The hydrogenated dehydrogenated titanium alloy powder obtained in step 4 is spheroidized in a selective laser sintering device to obtain ultrafine titanium alloy spherical powder; the parameters of the spheroidization treatment are: a reciprocating scanning strategy is adopted, the powder layer thickness is 20 μm to 40 μm, the laser power is 500 W to 700 W, and the scanning speed is 30 mm·s -1 ~60mm·s -1 , the pass spacing is 200μm~400μm.

2. The method for preparing ultrafine titanium alloy spherical powder for injection molding according to claim 1, characterized in that: The titanium alloy described in step 1 is TC4, TA7 or Ti-Al-Mo-Zr series titanium alloy.

3. The method for preparing ultrafine titanium alloy spherical powder for injection molding according to claim 1, characterized in that: Before the hydrogenation treatment in step 2, the titanium alloy ingot is crushed into blocks with a particle size less than 2 cm or turned into chips.

4. The method for preparing ultrafine titanium alloy spherical powder for injection molding according to claim 1, characterized in that: The particle size of the titanium hydride alloy powder in step 3 satisfies: D90≤25 μm; the coarse powder obtained by sieving is subjected to secondary ball milling and then sieving.

5. The method for preparing ultrafine titanium alloy spherical powder for injection molding according to claim 1, characterized in that: The vacuum degree in the dehydrogenation treatment in step 4 is less than 1Pa.

6. The method for preparing ultrafine titanium alloy spherical powder for injection molding according to claim 1, characterized in that: The spheroidization treatment in step five is carried out under argon protection, and the oxygen content in the working chamber of the selective laser sintering equipment is less than 600 ppm.

7. The method for preparing ultrafine titanium alloy spherical powder for injection molding according to claim 1, characterized in that: The ultrafine titanium alloy spherical powder described in step 5 is used for metal powder injection molding.

8. The method for preparing ultrafine titanium alloy spherical powder for injection molding according to claim 1, characterized in that: The particle size of the ultrafine titanium alloy spherical powder in step 5 satisfies: D90≤30μm.

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