Method of polishing titanium bars and titanium alloy
(1) Fine grinding
Regular emery rubber wheels are used to grind the surface of titanium castings and titanium alloy castings. Heat production and damages to the surface of castings should be avoided; the whole surface should be flat and smooth.
(2) Barrel grinding
Barrel grinding is to place processed castings, abrasives, water and additives into the grinding barrel. When the grinding barrel rotates and vibrates, abrasives and castings abrade with each other, making castings’ surface smooth and flat. It won’t cause dust pollution and requires low labor intensity; unlike regular grinding process, it won’t produce heat. For now, commercial barrel grinders and abrasives are available in Japan to grind titanium castings and titanium alloy castings, other metal castings and plastics and so on. Tests have shown that PK series of abrasives have highest grinding efficiency but highest surface roughness. SA series and B series of abrasives have lower abrasion efficiency than PK series, but they lead to castings’ surface with highest smoothness. For now, the Fourth Military Medical University has successfully developed the first barrel grinder in China for dentistry.
(3) Mechanical polishing
Dip soft cloth wheels or black brushes with different sizes in the polishing paste that is exclusively used for titanium and titanium alloy to polish the surface of titanium and titanium alloy. When polishing titanium castings, contaminated surface has to be cleaned up completely and new hardened layer should not be formed. Otherwise, desired result of polishing could not be achieved. Polishing with high rotate speed and low pressure is still adopted. The author once had tests by using green polishing paste to polish titanium and titanium alloy castings, which achieved relatively ideal results. Polished titanium and titanium alloy castingscould not be washed by water immediately. They could only be washed after the surface oxidation film takes shape completely. Otherwise, the surface will darken.