Titanium Grinding and Polishing

1. Mechanical grinding: Titanium has high chemical reactivity, low thermal conductivity, high viscosity, low mechanical grinding and grinding ratio, and is easy to react with abrasives. Ordinary abrasives are not suitable for titanium grinding and polishing. Hard abrasives, such as diamond, cubic boron nitride, etc., the polishing linear speed is generally 900 ~ 1800m/min., otherwise, the titanium surface is prone to grinding burns and micro cracks.
2. Ultrasonic grinding: Through the action of ultrasonic vibration, the abrasive grains between the grinding head and the surface to be polished and the surface to be polished are moved relative to each other to achieve the purpose of grinding and polishing. The advantage is that the grooves, sockets and narrow parts that cannot be ground by conventional rotary tools become easier, but the grinding effect of larger castings is still not satisfactory.
3. Electrolytic mechanical compound grinding: A conductive abrasive tool is used to apply electrolyte and voltage between the abrasive tool and the grinding surface. Under the combined action of mechanical and electrochemical polishing, the surface roughness is reduced and the surface gloss is improved. The electrolyte is 0.9NaCl, the voltage is 5v, and the speed is 3000rpm/min. This method can only grind the plane, and the grinding of complex denture brackets is still in the research stage.
4. Barrel grinding: The centrifugal force generated by the revolution and rotation of the grinding barrel is used to make the dentures in the barrel and the abrasives move in relative friction to reduce the surface roughness. The grinding is automated and efficient, but it can only reduce the surface roughness and not improve the surface gloss. The grinding accuracy is poor, and it can be used for deburring and rough grinding before the precise polishing of the denture.
5. Chemical polishing: Chemical polishing is to achieve the purpose of leveling and polishing through the redox reaction of metals in chemical media. The advantage is that chemical polishing has nothing to do with the hardness of the metal, the polishing area and the shape of the structure. All parts in contact with the polishing liquid are polished without special complicated equipment, and the operation is simple. It is more suitable for the polishing of titanium denture brackets with complex structures. However, the technical parameters of chemical polishing are difficult to control, and it is required to have a good polishing effect on the denture without affecting the accuracy of the denture. The better titanium chemical polishing solution is HF and HNO3 prepared in a certain proportion. HF is a reducing agent, which can dissolve titanium metal and play a leveling role. The concentration is <10%, HNO3 plays an oxidizing role, preventing excessive dissolution of titanium and hydrogen absorption , At the same time can produce a bright effect. Titanium polishing solution requires high concentration, low temperature, and short polishing time (1~2min.).
6. Electrolytic polishing: also known as electrochemical polishing or anode dissolution polishing, due to the low conductivity of titanium and extremely strong oxidation performance, the use of aqueous acidic electrolytes such as HF-H3PO4 and HF-H2SO series electrolytes can hardly polish titanium. After the external voltage is applied, the titanium anode oxidizes immediately, and the anode dissolution cannot proceed. However, the use of anhydrous chloride electrolyte at a low voltage has a good polishing effect on titanium. Small specimens can be mirror-polished, but for complex restorations, the goal of complete polishing is still not achieved. Maybe change the shape of the cathode and add a cathode The method of solving this problem needs to be further studied.