Isostatic Pressing for Round Tungsten Bar

Tungsten round bars formed by isostatic pressing can improve the uniformity of the tungsten material structure that can avoid the problem of brittle fracture on tungsten wire to some extent, thereby improving its wire-wounded performance, and improve the uniformity of wire diameter and improve the finished product rate, which has good reproducibility. When use square bar molds for making tungsten bars, the binder should be added to the doped tungsten powder, so that the internal forming tungsten is easily to cause stratification and likely to cause uneven density, cracks and other phenomena. Especially during the processing of tungsten square bars, the amount of deformation the four corners of tungsten bars is large, on the other hand, its center deformation is small, so its deformation is very unevenly at a high temperature, it is easy to produce localized cracking and final affecting the quality of tungsten wire and the finished product rate.

In order to solve the problems of tungsten square bars, developing isostatic pressing way to form round tungsten bars. Hot isopressing (HIP) is a manufacturing process, theorized in the 1970s, used to reduce the porosity of metals and increase the density of many ceramic materials. This improves the material's mechanical properties and workability. During isostatic pressing, it is preferable to make certain provisions of the metal powder. Different shapes, particle size and distribution of particle size of metal powders have a significant impact on manufacturing process of tungsten bars. Therefore, average particle size of doped tungsten powder should be 2.5 ~ 5.0μm, the oxygen content is lower than 2500 × 10-6. At the time of preparation of tungsten powder, it is important to control the humidity. When the tungsten powder to be filled into a soft film sets, be sure to place the powder uniformly and intimately, do not leave any gaps, in order to ensure the quality of the final product. After the preparation is completed, the speed of the release should be slowly. But there are some problems in the process. In the high pressure liquid when pressed, the size and shape of the final product cannot be controlled. Therefore, it is better to use a metal powder automatic loading machine, so we can guarantee that the final tungsten bars are flat, smooth and uniform.

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