Tungsten Alloy Counterweights Liquid-phase Sintering Preparation MethodⅡ
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- Category: Tungsten Information
- Published on Tuesday, 22 December 2015 16:55
- Written by yaqing
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The purpose of sintering is to turn the powdered materials into the bulk materials, and providing the specific properties to the bulk material. It can be divided into three stages when using the liquid-phase sintering method to prepare tungsten alloy counterweights: 1, the liquid phase generated and the particles rearrangement stage; 2, dissolution - precipitation stage; 3, the solid phase skeleton formation and grains growth stage. The density of the two-phase alloys, which sintered by liquid-phase sintering method is close to the theoretical density. This means that preparing tungsten alloy counterweights by liquid-phase sintering method may well keep their original high density characteristics, so that the tungsten alloy counterweights can exert great effectiveness and be better used in various fields.
1, The liquid phase generated and the particles rearrangement stage
This is the shortage stage which spent less time during tungsten alloy counterweight preparation process. At this stage, the nickel powders and iron powders will produce liquid phase as the temperature rises, and then produce the capillary force, which makes the powders to densify rapidly. Nickel is the essential element for the tungsten alloy counterweights preparation, the right amount of nickel (0.5% to 12%) can increase the viscosity between the powders and make it to a better densification. The degree of densification of the particles rearrangement stage depends on the liquid quantity, particle size, solubility of the solid in the liquid, etc., the compacts can be fully dense if the liquid number is sufficient(35%).
2, Dissolution - precipitation stage
The densification rate would be decreasded after the grains rearrangement stage, the dissolution and diffusion effect became the leader at this stage. The small powder particles would take precedence to be dissolved in the liquid phase, and the small particles precipitated on the surface of large particles with the particles size by diffusing and producing migrated substances, so that the particles can be coarsened and grew, while allowing the material to be further densified.
3, The solid phase skeleton formation and grains growth stage
The particles would be generated after liquid phase generated and the particles rearrangement stage and dissolution - precipitation stage, while producing the solid phase sintering on the particles contact surface and form a strong solid skeleton. But at this stage, it should not take too long time to sinter.
Tungsten alloy can achieve the fully dense between metals by liquid phase sintering preparation process, and then according to specific needs to create all kinds of different shapes counterweights, these counterweights have the excellent properties of high density, high thermal conductivity, corrosion resistance and anti-oxidation, etc., which makes it the best choice for many products in the field where needs counterweights.
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Tungsten Copper Electrode Metallographic Phase and Properties Analysis
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- Category: Tungsten Information
- Published on Tuesday, 22 December 2015 16:53
- Written by xiaobin
- Hits: 251
Tungsten copper powder sintered material morphology distribution of tungsten skeleton evenly distributed on the copper matrix. Due to the nature of tungsten (W) high melting point and high hardness, tungsten at 1000 ℃, its ultimate tensile strength is still 50kgf/mm2, low carbon intensity is even higher than room temperature, which makes tungsten copper material copper melting point below the temperature (about 1000 ℃), still has a very high wear resistance and heat hardness. The tungsten skeleton with copper as matrix stick as a whole, and constitutes the sintered material good heat conductor and pathways, so that the tungsten skeleton used in the process does not has partial overheating.
The strength at room temperature of common metal is determined by two essentials, which are Metal atomic binding force and resistance to dislocation motion. When tungsten copper used as electrode in welding resistance, it improves the strength by enhancing the resistance to dislocation motion, which includes cold hardening and the demolition. However, with the increasing temperature, the effect will remarkably decrease, even disappear. For instance, after cold hardening, the hardness at room temperature of red copper is HB100-110, when the temperature reaches 200-250℃, the hardening effect will disappear almost. In addition, most of strengthening copper alloy by precipitate phase will weaken owing to the phase integrates into the matrix again.
In contrast, the recrystallization and phase change of copper-tungsten powder sintered material does not occur at a high temperature. Some studies show that the data on tungsten copper materials, tungsten, copper W-30Cu hardness and conductivity higher than beryllium copper, the softening temperature was more than twice as beryllium copper. Therefore, tungsten copper material used as flash butt welding or arc welding electrodes, especially in continuous operation at high temperatures, which has high requirements of conductivity and high wear resistance requirements, it will better highlight the tungsten copper electrode material superiority.
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Tungsten Alloy Sword Hilt Counterweights
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- Category: Tungsten Information
- Published on Tuesday, 22 December 2015 16:46
- Written by yaqing
- Hits: 452
Early swords, whatever long swords or daggers, western swords or China swords are all the main weapons in cold weapons era. The medieval European knights were good at swords using, they generally added a counterweight ball in their own swords hilt. The main purpose is to adjust the center of gravity of the sword blade, in order to adjust the balance of power and flexibility based on the user's wrist force. If the center of gravity tend to sword blade, then the hacking or piercing power would be huge, but not good for the wrist to spin, if plus a counterweight ball or counterweights, then it would be easier to control the wrist spinning.
For the Europe swords, it is generally longer and heavy, if we do not increase the counterweight balls in the sword hilt, it will be very difficult to handle this sword. In other words, the purpose of increasing the counterweights is to make the overall weight of the sword reaches the balance level of people’s wont, so that the users will be more comfortable when using the swords. There are many kinds of materials that can be used to prepare sword hilt counterweights, but tungsten alloy counterweight material became the most important material because of its great density which can have a larger proportion in the case of smaller volume.
The main ways to increase the tungsten alloy counterweights to the sword hilt hilt are by adding the tungsten alloy counterweights to the top of sword hilt and adding the tungsten alloy counterweights in the sword handle. The reason why to increase the tungsten alloy counterweights is that to remove the center of gravity away from sword top as can as possible. So this is an effective method to reduce the balance point and increase the weight of swords. Because the weight in the sword blade will be heavier, so it needs to be heavier than the weights in sword hilt at the same balance point. So increasing tungsten alloy counterweight to the sword hilt can make the diameter of sword hilt to be longer thus be easier to prepare.
The property of high density makes tungsten alloy easy to achieve the requirements of sword hilt counterweights without increasing the materials volume. The corrosion resistance and anti-oxidation characteristics then makes the swords hilt to avoid the corrosion and decay by user's hand sweats. The drug-free environment characteristics also make it become the most popular material among many environmentalists. Using Tungsten alloy sword hilt counterweights will make it more comfortable to be used.
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Tungsten Alloy Counterweights Liquid-phase Sintering Preparation MethodⅠ
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- Category: Tungsten Information
- Published on Tuesday, 22 December 2015 16:51
- Written by yaqing
- Hits: 322
Tungsten alloy is a kind of two-phase composite alloy material that were composed with the tungsten substrate and a small amount of Cr, Mo, Ni, Cu, Fe, Co and other elements, i.e., the high melting point of tungsten phase and the low melting point of the γ phase (Ni-Fe, Ni- Cu, etc.), it can be divided into two categories, namely, W-Ni-Cu alloys and W-Ni-Fe alloys, they both have a series of excellent physical and mechanical properties. But the plasticity of W-Ni-Cu alloys would be lower compared to W-Ni-Fe alloys, which makes its application more extensive. The applications of tungsten alloy counterweights can be described as extensive, it can be used in the sophisticated science technology such as aerospace, and the the gyrorotors, screw counterweights, trim tabs etc. of the navigator in military industry. Besides, the tungsten alloy counterweights also can be used as the balance counterweight elements in the machinery manufacturing and pressure casting industry and so on.
Tungsten alloy counterweights were mainly mixed, pressed and sintered with tungsten powders, nickel powders and iron powders. Wherein the amount of tungsten is up to 80% to 97%, while the nickel powders and iron powders are mainly acted as bonding agents. Due to the huge different melting points between the two-phase, so it is a typical liquid-phase sintered alloy, and it is also the main preparation method of tungsten alloy counterweights.
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Effects of Ammonium Paratungstate Calcination Temperature on Properties of Tungsten Powder
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- Category: Tungsten Information
- Published on Tuesday, 22 December 2015 14:32
- Written by xinyi
- Hits: 285
Authorities differ on the meaning of Calcination (also referred to as calcining). The IUPAC defines it as 'Heating to high temperatures in air or oxygen'. However calcination is also used to mean a thermal treatment process in the absence or limited supply of air or oxygen applied to ores and other solid materials to bring about a thermal decomposition, phase transition, or removal of a volatile fraction. The calcination process normally takes place at temperatures below the melting point of the product materials. Calcination is not the same process as roasting. In roasting, more complex gas–solid reactions take place between the furnace atmosphere and the solids. Calcination takes place inside equipment called calciners. A calciner is a steel cylinder that rotates inside a heated furnace and performs indirect high-temperature processing (1000-2100 °F) within a controlled atmosphere.
The calcined products were obtained by calcining ammonium paratungstate(APT) at different phase transition temperatures and then reduced to tungsten powder under hydrogen atmosphere in reducing furnace. The micro-morphology and particle size distribution of the reduced tungsten powder were analyzed by scanning electron microscope(SEM) and laser granulometer,respectively.The results show that the calcination temperature for APT has a great effect on the tungsten powder properties.The tungsten powder with uniform particle size and good dispersity can be obtained at the calcination temperature of 425 ℃.
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