Papers by Keyword: Low Melting Point

Abstract: In order to study the preparation of low-melting alloy powder in phase change materials, three sets of control experiments were set up in this paper. To explore the effects of ultrasonic oscillation, ultrasonic atomization technology and rapid cooling had an effect on the particle size, surface morphology and powder shape of ultrasonic powder making. In the experiment, ultrasonic atomization, rapidly cooling ultrasonic atomization, and ultrasonic vibration generated powder were tested. The results showed that the surface of fog droplets generated by ultrasonic atomization was smooth, with distinct particles. The powder diameter was large, ranging from 20-60 μm. The surface of the powder obtained by ultrasonic shock existed an aggregation phenomenon. The powder diameter was small ranging from 5-10 μm. The ultrasonic atomized powder obtained by rapid cooling was mostly spherical with a smooth surface. After the screening, spherical powder with a diameter of 15-25 μm and the smooth surface could be obtained. The results showed that the particle diameter is small and uniform, while the uneven surface was difficult to eliminate. The experimental conditions of rapid cooling were favorable for the smoothness of the particle surface and the roundness of powder shape. Spherical powder with a diameter of 15-25 μm can be obtained by screening the rapidly cooled powder after ultrasonic atomization. Different experimental conditions and technological approach can produce high-performance low melting point alloy powder.

Abstract: Oxide free Tin nanoparticles were synthesized from a chemical reduction method. Their morphological and thermal characterizations were studied in this paper. The X-ray diffraction (XRD) study showed that no oxides of Tin nanoparticles were formed. The thermal characterization by differential scanning calorimetry (DSC) exhibited the size dependency of the melting points. The melting point was as low as 202.16°C.

Abstract: Cemented carbides have been widely used for cutting tools because of their high hardness and abrasion resistance. Since the cemented carbides are so expensive, it is desirable to reuse a tool shank made of cemented carbides. For the reason, so far, a new blade of a tool has been brazed to used shanks. However, when cemented carbides are heated for brazing, heating inevitably causes the deterioration in the mechanical properties. This study was carried out to braze the cemented carbides at lower temperatures for reducing the deterioration of the shank. First of all, authors developed a new Ag-based brazing filler metal with a low melting point of about 605°C, and investigated the effects of the new Ag filler metal on the properties of a brazed joint. Moreover, Co element or Ni element was added into the Ag filler metal to make the bending strength of a brazed joint improved. The addition of Co element increased the bending strength of a joint and the strength was equivalent to that of a joint brazed at 750°C using a conventional Ag filler metal, but the addition of Ni element decreased the bending strength of a brazed joint.

Abstract: The adhesion between diamond grits and the bond strongly influence the properties of diamond tools. Since diamond is covalent crystal, the high interfacial energy leads to the poor interface bonding between diamond grits and the bond. Furthermore, the sintering temperature of traditional vitrified bond is also very high because of the high refractoriness of alkalis containing in the bond, resulting in serious thermal damage to diamond grits. In this paper, a low melting point and high strength vitrified bond has been prepared mainly from borate glass, clay and lead glass. The bond is completely glassy above 850°C and the bending strength of the bond sintered at 850°C for 7 minutes is 125.7MPa with a 6.5:3.5 corundum/bond ratio. Moreover, this bond possesses good wettability with diamond abrasive from 600°C to 850°C.