Metal titanium and titanium alloys prepared by powder metallurgy method have large chemical activity, easy to polluted by gas and crucible material, thus high quality titanium powder primarily in high vacuum or high purity inert gas protect, use centrifugal atomization process to produce.
Products forming are generally not adding binder, the blank must be sintered in vacuum. Late 1940s, it was the first to carry out the pressing and sintering technology research about sponge titanium powder as raw material. However, the product performance produced by this process can not meet the requirements of the aviation sector, mainly for the corrosion, filter and other parts of manufacturing chemical industry, light industry, metallurgy, marine development and other departments needed. Of which the first product won industrial application is titanium porous filter material.
In mid-1960s, began to develop rotating electrode process taking titanium alloy powder and hot isostatic densification process. With this technology, the static mechanical properties of products are equivalent with melting processing products, but significantly reduced machining, improved material utilization, started using for the aviation industry. To the late 1970s, titanium powder metallurgy products in corrosion resistance and aviation applications receive rapid development. In the early 1970s, Chinese metal powder supplier began the research of titanium powder metallurgy process and products, titanium valves, bushings, perforated tubes and plates, titanium-titanium carbide wear-resistant materials and corrosion resistant alloys such as titanium-molybdenum have industrial production. In the late 1970s, launched a research about centrifugal atomization prepare high quality titanium powder and hot isostatic pressing technology.
Milling process to produce titanium and titanium alloy powders have the following four methods: ` sodium reduce sponge titanium powder. This powder large yield, cheap, powder plasticity is good, suitable for cold forming, is the main raw material to produce general corrosion products. Because of its high content sodium and chloride ions, it is easily to contaminated apparatus and deteriorated the material welding performance while sintering. a electrolytic titanium powder. High purity, but the moldability of the electrolytic titanium powder is poor than sponge titanium powder. b dehydrogenation hydrogenated titanium powder. Through hydrogenation dehydrogenation process can obtain good quality, fine grain size titanium powder and alloy powder; but the volume is small, the price is more expensive. c centrifugal atomization titanium powder. In 1960 U.S. was first use titanium arc rotating electrode process to prepare titanium pre-alloy powder, the powder is spherical. This alloy powder with high purity, uniformity composition, good fluidity, filling density is 65% of the theoretical value. Such powder should only use hot forming, can use hot isostatic pressing process made complex shape parts. Rotating electrode arc milling process, since there is a tungsten electrode rod, so it prone to produce tungsten contamination (tungsten-containing in powder is 400ppm), will reduce the fatigue properties of materials. To eliminate tungsten contamination, it also developing an electron beam or plasma to heat the rotating electrode and arc rotating crucible and a variety of electron beam rotating disk centrifugal atomization process. This powder is the main raw material of manufacturing titanium powder metallurgy aviation components.
Densification process depending on the powder materials’ requirements of the products, can use different densification processes. Mainly have: ` bulk or low pressure forming powder sintered, sintered porosity is 25 to 70%. a pressing and sintering. Pressing can be used mechanical or isostatic pressing, pressing pressure at 2000 ~ 4000kgf/cm, the sintering temperature is 1000-1400. The relative density of the sintered body can be up to 92 to 95%. b thermoforming. Make the powder or powder billet pressure molding during the heating process. Hot forming processes are mainly the hot isostatic pressing and vacuum hot pressing and so on. c the powder compact rolling of titanium powder and powder. These processes can obtain high density and good performance titanium powder materials or parts. Of which the powder rolling is the effective and economical process of producing porous titanium and dense titanium.
Source:http://www.mhcmp.com
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