The metal powder high velocity compaction machines achieve the suppression speed of 2 to 10m s-1. Its suppressing speed is 2 to 3 orders higher than magnitude than conventional repression.
It is more than 2 times of the speed of free forging hammer. In the study of high velocity compaction of iron powder, copper powder (FCu), soft magnetic materials in different processes and different companies, scientists get the expected regular patterns of density changes. With the increase of suppression and suppress pressure, the density is improved. The study found that the density increases rapidly with the suppression rate increase. When the density is more than 7.9m • s-1, the sl growing speed becomes slower.
Compacting pressure by the static pressure into dynamic pressure, high velocity compaction powder body by the static pressure P and the role of the momentum mv, short duration of action, instantaneous impact force F = mv / t great, so that the density of compacts relative increase. Conducted experiments on the different components of the iron-based parts and materials, the green density of the master alloy mixture of powder and water atomized prealloyed powder 0.3g • cm in-3. The green density of high velocity compaction compared with other powder metallurgy process, the advantage is obvious, the HVC technology can not only access to high-density parts, and the density is uniform, the parts in different parts of the density difference be minimized. Compacts in the high velocity compaction along the axial density distribution than the static pressure evenly for the aspect ratio of 6.7 of cylindrical parts, sintered density difference of 0.2g • cm-3.
Under conventional conditions of repression, the density of compacts depends on the compaction pressure, high velocity compaction pressure the green density depends on the suppression of energy, a very short time a number of high-speed suppress the suppression of energy able to accumulate, so that the density of the powder to the 4000J the impact of energy to reach the green density can be done with 2000J of energy shocks, which provides the possibility to use small and medium-sized equipment to produce large size parts.
The elastic aftereffect of compacts in the high velocity compaction below the conventional repression. Water atomized metal powder forming a diameter of 31mm cylinder, the elastic aftereffect was 40% lower than conventional repression. The low elastic aftereffect reduces mold release pressure. The high velocity compaction of the coefficient of lateral pressure was significantly lower than the static repression. Materials and density of the compacts under the conditions of high velocity compaction mold release pressure 1.5 ~ 2.5 times lower than the static repression.
Material density and uniformity of the effective measures to improve the performance of powder metallurgy products. The HVC make significantly improve the performance of powder metallurgy materials. Study found that the hardness and tensile strength of metal materials with density increases in proportion to improve the powder the maximum density value close to 7.6g/cm3 hardness 3400MPa yield strength and tensile strength of 800MPa and 1150MPa, the fatigue limit of 380MPa . If the processing of high-temperature sinters and sinter hardening process, the alloy yield strength greater than 1200MPa tensile strength close to 1400MPa. For maximum suppression of density of the metal powder are 717g/cm3 carburizing + quenching process, the bending fatigue limit is greater than 550MPa.
In pressing process of metal powder high velocity compaction technology, it achieves fully automation and greatly improves production efficiency for metal powder exporter. Because high density of compaction can shorten sintering time, it further controls grain size and thus enhancing performances of the products or reducing costs. Comparing to powder forging process, the high velocity compaction has a cost advantage. Therefore it has broad application prospects. It can be applied in preparation of simple gears, valve guide sleeve, main bearing caps, wheel hubs, gears, flanges, bushings, bearing ring and cam lobe organizations products.Source:http://www.mhcmp.com
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