CN1118584C - Process for preparing W-Ni-Fe alloy with superfine grains and high specific weight - Google Patents
Process for preparing W-Ni-Fe alloy with superfine grains and high specific weight Download PDFInfo
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- CN1118584C CN1118584C CN 01109075 CN01109075A CN1118584C CN 1118584 C CN1118584 C CN 1118584C CN 01109075 CN01109075 CN 01109075 CN 01109075 A CN01109075 A CN 01109075A CN 1118584 C CN1118584 C CN 1118584C
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Abstract
In the present invention, composite oxide powder of (WO3-NiO-FeO) or (WO3-NiO-CuO) prepared by a low-temperature ullrasonic-spraying thermal-conversion method is reduced by H2 for 30 to 80 minutes at a low temperature of 400 to 780 DEG C to prepare (W-Ni-Fe) or (W-Ni-Cu) alloy powder with ultrafine grains (average grain size is smaller than 120mm); then the (W-Ni-Fe) or (W-Ni-Cu) alloy powder is pulverized by a high-energy ball mill, pressed and formed, and sintered under the protection of H2 or in a vacuum or HIP (hot isostatic pressing) to prepare a (W-Ni-Fe) or (W-Ni-Cu) series high gravity alloy. The alloy has the advantages of high density (16 to 19.3 g/cm<3>) and fine grain (the average grain size of W grains in the alloy is smaller than or equal to 4 mum).
Description
Technical Field
The invention provides a preparation technology of ultra-fine grain (W-Ni-Fe) or W-Ni-Cu series high specific gravity alloy.
Background
Tungsten-based high specific gravity alloys are a special type of powder metallurgy material with special properties. The specific gravity of tungsten is highly predominant in all metallic materials, to which only radioactive depleted uranium can be compared. The characteristic determines that the tungsten-based high-specific gravity alloy is widely used as a high-kinetic energy armor piercing bullet core; flywheels in mechanical devices; an aircraft tail; a dynamic balance weight for a rotating machine; a BP machine vibration hammer; a high-speed grinding machine spindle; a gyroscope rotor; pendulum bob of automatic watch and sports equipment. The most widely used parts at present are armor piercing cores, including cannon cores, gun cores, grenade bundling rings, rebounding guided missile bundling rings and the like. The tungsten-based high specific gravity alloy has strong capturing and absorbing capacity for neutrons and other radioactive rays besides high specific gravity. Therefore, it is widely used as a radioactive shielding material. Mainly comprises nuclear material production, storage and shell structure materials, radioactive medical instruments, gamma-knife radioactive source shielding devices, measuring instrument parts and the like. In addition, the tungsten has the highest melting point, good high temperature resistance, small thermal expansion coefficient and high elastic modulus. Except for rocket nozzles, high-temperature sweating materials, ultrahigh-temperature electric heaters and the like. And can be combined with other materials to form a composite material with adjustable physical properties (such as expansion coefficient, elastic modulus and the like) in a wide range. This feature has been widely used in the field of mechanical and electrical materials in recent years. The material is mainly packaging material for assembling computer chips and power devices, tool material such as electric upsetting and pressure welding, electric contact material, electrode material and the like.
As is known from the research and analysis of the related documents in the last 15 years, in the production of the tungsten-based high specific gravity alloy, the original W powder with the average particle size of 2-6 μm and the Ni, Fe and Cu powder with the average particle size of 30-80 μm are adopted in all countries in the world. In recent years, tungsten powder of a relatively small size (0.5 to 2 μm) has been used. The alloy is prepared by mixing several kinds of metal powder by adopting a mechanical ball milling and mixing method. The alloy thus prepared, during sintering, is based on tungsten grains (N)And (i) dissolving and precipitating the liquid phase of Fe) or (Ni, Cu) until the original tungsten crystal grains grow from 2-6 mu m to 20-80 mu m. The tungsten crystal grain is about 10-13 times of the original tungsten crystal grain, and the mechanical property, the physical property, the pressure processing property and the cutting property of the high-specific gravity alloy are obviously reduced by the coarse tungsten crystal grain. Meanwhile, because the average grain diameter of the adopted original Ni, Fe and Cu powder is thick and is mechanically mixed, the components are not easy to be uniform, a large liquidpool in the liquid phase sintering process can lead to coarse second phase grains, and the residual porosity of the alloy is high. And also reduces the mechanical property, physical property, pressure processing and machining property of the tungsten-based high-specific gravity alloy. The Chinese patent specification with patent publication No. 1220926 provides a method for preparing nano-scale superfine powder by low-temperature ultrasonic spray thermal conversion (WO)3NiO-FeO) or (WO)3-NiO-CuO) composite oxide powder, which can be used as a raw material in the present invention.
Disclosure of Invention
The invention aims to: prepared by a low-temperature ultrasonic spray thermal conversion method (WO)3NiO-FeO) or (WO)3-NiO-CuO) as raw material, and low-temperature H is carried out by2Gas reduction is carried out to prepare superfine (W-Ni-Fe) or (W-Ni-Cu) alloy powder with average grain diameter less than or equal to 120nm, and the superfine (W-Ni-Fe) or (W-Ni-Cu) alloy powder is subjected to high-energy ball milling, crushing, forming and sintering processes to directly prepare the tungsten-based high-specific gravity alloy with average grain diameter less than or equal to 4 mu m.
The invention comprises the following components:
1. reduction of
Preparation of nanometer grade superfine (WO) by low temperature ultrasonic spray thermal conversion method3NiO-FeO) or (WO)3-NiO-CuO) composite oxide powder as raw material, using H2Directly reducing the mixture by gas, wherein the reduction temperature is 400-780 ℃, preserving the heat for 30-80 minutes,
the chemical reaction formula of the direct reduction method is as follows: it is also possible to use a two-stage reduction,the temperature of the first stage is 400-500 ℃, the temperature is kept for 30-50 minutes, and the temperature of the second stage is 600-740 ℃, and the temperature is kept for 30-50 minutes. The chemical reaction formula of the two-stage reduction method is as follows:
the reduction equipment can adopt a tubular reduction furnace, an airflow rotary furnace and a fluidized bed furnace. Can be prepared into (W-Ni-Fe) or (W-Ni-Cu) superfine alloy powder with uniform components and average grain diameter less than or equal to 120 nm.
When the direct reduction method is adopted, the reduction temperature is higher, but the first stage temperature in the two-stage reduction method is lower, and the method is mainly characterized in that WO is added3Reduction to blue tungsten WO2.90The second stage reduction temperature is also 740 ℃ lower. In order to remove the reaction product water vapor as quickly as possible during the actual reduction, regardless of the reduction method used, the H is actually introduced2The air flow is 2-3 times of the theoretical requirement. 1/2N may be used when a rotary kiln or fluidized bed is used2) The gas acts as a carrier working gas. The reduction temperature was 740 ℃. The average particle size of the (W-Ni-Fe) or (W-Ni-Cu) alloy powder produced by the gas flow back converter is finer than that of the powder in the tube furnace.
2. Crushing
And crushing the superfine alloy powder in a high-speed high-energy ball mill. The main purpose is to link the particle necks, i.e. "bridge" the agglomerates, generated by high temperature diffusion during the reduction process. Highly dispersed alloy powder with good compactibility is prepared. And then the alloy powder is formed by a conventional steel die, and is prepared into a pressed compact under the unit pressure of 200-800 MPa, or other forming methods such as injection forming, cold isostatic pressing, dry die pressing, soft die pressing and the like are used. Various required blanks are made.
The energy of the high-speed (780-2400 rpm) high-energy ball mill used is much higher than that of a common low-speed (less than 400 rpm) stirring ball mill or a vibration ball mill, and the 'bridging' aggregates of the ultrafine powder are easily crushed. Ultrafine powder crushed by a high-speed high-energy ball mill and having a loose specific gravityCan be from 0.5 to 0.7 g/cm3Increasing the concentration to 1.4-1.7 g/cm3The relative density of the pressed compact can be improved from 33% to 53-58%.
And (3) grinding the superfine alloy powder ((W.Ni.Fe) or (W.Ni.Cu)) prepared by low-temperature reduction for 30-80 minutes in a horizontal high-speed high-energy ball mill. Can eliminate 'bridging' aggregates in the superfine powder and improve the loose packing density and the compressibility of the powder. The relative density of the pressed compact can be more than or equal to 56% under the pressure of 400-600 MPa. The size of the product is convenient to control during sintering.
3. Shaping by
When the powder is formed in a steel die, the particle size of the powder is smaller than 120nm and enters a nanometer superfine range, and the internal friction of the powder particles is increased sharply duringforming, so that the unit pressing pressure is obviously increased, and the layering pressure of a pressed compact is reduced. Therefore, higher unit pressing pressure is generally adopted when the steel die is formed. Sometimes a suitable amount of lubricant is added to the powder. Or the green compact with uniform density and higher strength can be prepared by adopting methods such as high-pressure soft die forming or cold isostatic pressing forming and the like.
4. Sintering
And sintering the pressed compact in an H2 gas-shielded sintering furnace, and preserving heat at 1100-1500 ℃ for 30-80 minutes to obtain the tungsten-based high-specific gravity alloy with the average particle size of less than or equal to 4 microns. The sintering equipment and sintering process can also be selected from vacuum sintering, vacuum-medium pressure sintering, HIP (hot isostatic pressing) sintering, hollow cathode plasma furnace sintering and the like
The sintering equipment and the sintering process can be selected according to the performance requirements of the sintered product. For products with low density and strength, H can be used2(hydrogen) gas sintering furnaces and lower sintering temperatures. On the contrary, vacuum sintering, or vacuum-medium pressure sintering, HIP (hot isostatic pressing) sintering method is adopted. The experiment proves the comprehensive mechanical property of the superfine tungsten-based high-specific gravity alloy sintered by the HIP method; physical properties; the processability is best.
The obtained green compact is processed in H2And (3) performing low-temperature short-time (30-40 min) rapid sintering in a gas-shielded sintering furnace at the temperature below (or close to) 1260-1500 ℃ of the liquidus temperature of the alloy. Or in a vacuum-medium pressure furnace or HIP (hot isostatic pressing) (argonGas or nitrogen pressurization) and the low-temperature rapid sintering method is also adopted to prepare the high-specific gravity alloy with extremely low residual porosity (0.05-0.15%).
The invention has the advantages that:
1. provides a new technology for producing nanometer-level superfine (W-Ni-Fe) or (W-Ni-Cu) alloy powder with the average grain diameter of less than 120nm from the production technology.
2. The produced nanometer grade superfine alloy powder has the grain size less than 120nm and the alloy components are very uniform. The grain size of the alloy powder is far smaller than that of the alloy powder adopted in various countries at present by about 1/20-1/50.
3. The mixing process of the alloy powder can be omitted in the production process.
4. The sintering temperature of the alloy is low, the alloy can be carried out below the liquidus temperature (solid phase sintering), and tungsten crystal grains are not easy to grow up
5. In the alloy structure, tungsten grains are polygonal. The spherical characteristics are completely disappeared, the grain boundary area is obviously increased, and the mechanical and physical properties of the alloy are favorably and comprehensively improved
6. The average grain diameter of tungsten crystal grains in the alloy is less than or equal to 4 mu m. While the submicron structures within the grains are finer.
Drawings
FIG. 1 is a flow chart of the preparation process of the present invention, wherein the ultrasonic spray thermal conversion method is used for preparation (WO)3NiO-FeO) or (WO)3-NiO-CuO) composite oxide powder 1, low temperature (H) in a tube furnace2Gas) reduction to prepare (W-Ni-Fe) or (W-Ni-Cu) ultrafine alloy powder 2. The reduced alloy powder is crushed by a high-speed high-energy ball mill 3. Vacuum drying to remove alcohol 4, adding lubricant 5, forming 6, sintering 7, tungsten-based high specific gravity alloy 8 and detecting 9. Wherein lubricants or plasticizers are generally used in steel die press forming, especially in injection molding. Common lubricants or plasticizers are polyethylene glycol (PEG), paraffin, sodium butadiene rubber, etc., which must be removed prior to sintering when added, or else the product will be substantially carburised. The forming process of the alloy adopts any forming method according to the volume of the product,the complexity of the shape, the density requirement and the like. Products with simple shapes and small volumes are generally formed by steel dies. Products with small volume but complex shape are mostly produced by injection molding. Products with larger volume or large and complex shape are generally prepared into pressed blanks by matching with forming methods such as cold isostatic pressing, dry die pressing, soft die pressing and the like with machining. When the latter three methods are used for forming, no lubricant is added to the alloy powder. In the sintering process, when the sintering temperature and the sintering time are determined, the sintering temperature of the superfine alloy powder is fully considered to be 100-250 ℃ lower than that of the alloy powder with coarse granularity. In addition, when sintering equipment having a positive pressure is used, such as a vacuum-medium pressure furnace, hot pressing, and Hot Isostatic Pressing (HIP), the sintering temperature still needs to be further reduced.
Detailed Description
Example 1:
the preparation of a high specific gravity alloy having W (93 wt%) and Ni (4.9 wt%) and Fe (2.1 wt%) was carried out in the following manner.
1. Prepared by weighing spray heat conversion method (WO)3NiO.FeO) composite oxide powder 10Kg, the weight percentage of the W.Ni.Fe three elements in the composite oxide powder is: (W: Ni: Fe: 93: 4.9: 2.1).
2. The composite oxide powder was placed in a stainless boat of a tube furnace, the thickness of the material layer was generally 25mm, the amount of boat loading was determined depending on the sectional size of the furnace chamber of the tube furnace and the size of the boat, and generally 300 g/boat, and the boat after loading was pushed into the tube furnace. Pushing the boat in front into the high temperature area in the furnace every time loading one boat later, and performing tube type (H) operation2Gas) reduction furnace, reverse flow H2H in the furnace tube2The gas cross section flow is controlled to be (60 ml/cm)2Min). The reduction temperature in direct reduction was 750 ℃ and 50 minutes. And (4) cooling the boat by a cooling belt and discharging the boat from the furnace. The superfine alloy powder with the components (W: Ni: Fe: 93: 4.9: 2.1) can be obtained.
3. Adding 2.5kg of industrial alcohol into the alloy powder, putting the alloy powder into a 10L horizontal high-speed high-energy ball mill, crushing for 60 minutes, screening the slurry through a 44-micron sieve after stopping the mill, and transferring the slurry into a vacuum dryer.
4. Removing alcohol (recovering) from the slurry under vacuum, introducing steam of 100 deg.C into the interlayer of the dryer to dry the alloy powder, cooling, and discharging to obtain alloy powder with average particle diameter less than or equal to 120nm
5. 1Kg of alloy powder was weighed and added to a gasoline solution of polyethylene glycol in a proportion of (2% by weight of polyethylene glycol), and mixed in a blender with stirring (or by hand). When paraffin-gasoline solution or sodium butadiene rubber-gasoline solution is used, the proportion and the operation method are also adopted. The alloy powder added with the lubricant is put into a steel die for forming after being air-dried or dried at low temperature (less than 60 ℃).
6. The alloy powder is filled into a steel die (the size of the die is phi 12), and the die is pressed into a (phi 12 multiplied by 12) pressed compact under the unit pressing pressure (500MPa)
7. In a vacuum furnace 1350 ℃; cooling and discharging after 60 minutes of sintering to obtain the product with the density of more than 17.2g/cm3The tungsten-based high specific gravity alloy of (1). The average grain diameter of tungsten crystal grains is less than or equal to 4 mu m
Example 2
The preparation of a high gravity alloy containing W (93 wt%), Ni (4.9 wt%) and Cu (2.1 wt%) was accomplished by the following procedure
1. Prepared by weighing spray heat conversion method (WO)3Nio.cuo) 10kg of a composite oxide powder containing w.ni.cu in a mass ratio of 93: 4.9: 2.1
2. The composite oxide powder was reduced by the same method and procedure and the same reduction process parameters as in the second example 1, to obtain an ultrafine alloy powder having W, Ni and Cu in a ratio of 93: 4.9: 2.1.
3.4.5.6. The procedure was identical to 3.4.5.6 in example 1, procedure method and technical parameters.
7. 1320 ℃ in a vacuum furnace; cooling and discharging after 60 minutes of sintering to obtain the product with the density of more than 17.3g/cm3The tungsten-based high specific gravity alloy of (1). The average grain diameter of the tungsten crystal grains is less than or equal to 4 mu m
Claims (4)
1. A technology for preparing W-Ni-Fe or W-Ni-Cu series high-specific gravity alloy with superfine crystal grains and WO used3NiO.FeO or WO3NiO.CuO composite oxide powder is nano-scale superfine oxide powder prepared by adopting an ultralow temperature spray thermal conversion method at 50-70 ℃, and is characterized in that: WO prepared by low-temperature spray heat transfer method3NiO.FeO or WO3NiO, CuO composite oxide powder having an average particle diameter of not more than 100nm and containing 30 to 80 minutes of H at 400 to 780 DEG C2Gas reduction is carried out to prepare alloy powder with W.Ni.Fe or W.Ni.Cu superfine crystal grains and average grain diameter less than 120nm, high-energy ball milling and die pressing forming are carried out, unit pressure is 400-800 MPa, H is carried out2Gas-shielded sintering at 1000-1480 deg.c for 30-80 min to obtain W-Ni-Fe or W-Ni-Cu high specific gravity alloy with average grain size not greater than 4 micron.
2. The technique for producing an ultra-fine grain W-Ni-Fe or W-Ni-Cu based high specific gravity alloy according to claim 1, wherein: the elements contained in the composite oxide powder are mixed with each other in an ionic state in a solution, and the sintering may be performed by vacuum or HIP sintering,
3. the technique for producing an ultra-fine grain W-Ni-Fe or W-Ni-Cu based high specific gravity alloy according to claim 1 or 2, wherein: grinding the superfine alloy powder W.Ni.Fe or W.Ni.Cu prepared by low-temperature reduction in a horizontal high-speed high-energy ball mill for 30-80 minutes; pressing the mixture into a blank under the pressure of 400-600 MPa.
4. The technique for producing an ultra-fine grain W-Ni-Fe or W-Ni-Cu based high specific gravity alloy according to claim 1 or 2, wherein: placing the obtained green compact in H2And (3) rapidly sintering the alloy in a gas-shielded sintering furnace at 1260-1500 ℃ below the liquidus temperature of the alloy for 30-40 minutes, or pressurizing the alloy in a vacuum-medium pressure furnace or HIP hot isostatic pressing by argon or nitrogen, and similarly adopting the low-temperature rapid sintering method.
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| CN100338251C (en) * | 2004-05-11 | 2007-09-19 | 高殿斌 | Method for producing products of tungsten, molybdenum and alloy |
| JP4916450B2 (en) * | 2005-11-28 | 2012-04-11 | 株式会社アライドマテリアル | Tungsten alloy grain, processing method using the same, and manufacturing method thereof |
| CN102828059B (en) * | 2012-09-27 | 2013-11-06 | 北京科技大学 | Preparation method of contact alloy for nano particle filled tungsten skeleton special structure |
| CN108723380A (en) * | 2018-06-07 | 2018-11-02 | 江西离子型稀土工程技术研究有限公司 | A kind of preparation method of rare earth-iron base pre-alloyed powder |
| CN113426997B (en) * | 2021-06-11 | 2023-04-18 | 西安交通大学 | High-specific-gravity tungsten-nickel-iron alloy and laser additive manufacturing method thereof |
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