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Manufacture of Alloy Powder

Manufacture of Alloy Powder. Lathe-cut (Irregular) powder Atomized (Spherical) powder Particle size v.s. Properties. Endanus Harijanto. Lathe-cut (Irregular) Powder. Metal ingredients heated poured into a mold  ingot (Ag 3 Sn ( g ) + some b, e, h ) Ingot  homogenizing anneal

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Manufacture of Alloy Powder

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  1. Manufacture of Alloy Powder Lathe-cut (Irregular) powder Atomized (Spherical) powder Particle size v.s. Properties Endanus Harijanto

  2. Lathe-cut (Irregular) Powder • Metal ingredients heated poured into a mold  ingot (Ag3Sn (g) + some b, e, h) • Ingot  homogenizing anneal • An annealed ingot of alloy is place in a machine and is fed into a cutting tool. • 60-120 µm in length, 10-70 µm in width

  3. Atomized (Spherical) Powder • Made by melting the desired elements together • The liquid metal is atomized into fine spherical droplets of metal by being sprayed under high pressure of an inert gas. •  “Spherical powders” 2- 43 µm • Also have heat treatment and are usually washed with acid.

  4. Homogenizing Anneal • The ingot is placed in an oven and heated at a temperature below the solidus (at 400°C) for sufficient time (6-8 hours) to allow diffusion of the atoms to occur and the phases to reach equilibrium.

  5. Particle Treatments • Acid-washed amalgam powders • tend to be more reactive. • Stress-relief process after particle cutting • annealing cycle at ~ 100°C for several hours • “aging process”

  6. Lathe-cut v.s. Atomized alloys • Lathe-cut or admixed powders resist condensation better than spherical powders. • Spherical alloys require less mercury than typical lathe-cut alloys because of the smaller surface area per volume. • Amalgams with a low mercury content generally have better properties.

  7. Particle Size • A powder containing tiny particles requires a greater amount of mercury to form an acceptable amalgam. • A small-to-average particle size  a more rapid hardening and a greater early strength • Particle size distribution can affect the character of the finished surface. • The larger particles may be pulled out during carving  a rough surface  corrosion

  8. Amalgam Alloy Composition • ANSI/ADA Spec. #1 (ISO 1559) requires that amalgam alloys be predominantly silver (Ag) and tin (Sn). • containing Zn > 0.01%  “Zinc Containing” • containing Zn < 0.01%  “nonzinc”

  9. Classification • Low-copper (Conventional) amalgam alloy (at least 65 wt% Ag, 29 wt% Sn, < 6 wt% Cu) • lathe-cut (irregular) powder or spherical particles or mixed • Ag-Sn • High-copper amalgam alloy (6-60 wt% Cu) • (1) Admixed (Ag-Sn + Ag-Cu) • A mixture of irregular and spherical particles of different or same composition • (2) Unicomposition or Single composition (Ag-Sn-Cu) • All spherical particles  90% of the dental amalgams currently placed

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