How To Deal With Surface Defects Of Titanium Rods？
The surface reaction layer of titanium plate and titanium rod is the main factor affecting the physical and chemical properties of titanium workpieces. Before processing, the surface contamination layer and defect layer must be completely removed. Physical and mechanical polishing of titanium plate and titanium rod surface polishing process:
1. Sandblasting:
Titanium wire castings generally choose white corundum for sandblasting. The pressure of sandblasting is lower than that of non-precious metals, and it is generally controlled below 0.45MPa. Because, when the spray pressure is too high, the sand particles impact the titanium surface to produce intense sparks, and the temperature rise can react with the titanium surface to form secondary pollution and affect the surface quality. The time is 15-30 seconds, and only the sticky sand, surface sintered layer and partial oxide layer on the surface of the casting can be removed. The remaining surface reaction layer structure should be quickly removed by chemical pickling.
2. Pickling:
Pickling can quickly and completely remove the surface reaction layer, and the surface will not be polluted by other elements. Both HF-HCL series and HF-HNO3 series pickling liquids can be used for pickling of titanium, but HF-HCL series pickling liquids have a larger hydrogen absorption capacity, while HF-HNO3 series pickling liquids have small hydrogen absorption and can control HNO3 The concentration of HNO3 reduces hydrogen absorption and can brighten the surface. Generally, the concentration of HF is about 3%-5%, and the concentration of HNO3 is about 15%-30%.
The surface reaction layer of titanium plate and titanium rod can be completely removed by the method of pickling after sandblasting.
In addition to physical and mechanical polishing, there are two types of reaction layers on the surface of titanium plates and titanium rods: 1. Chemical polishing and 2. Electrolytic polishing.
1. Chemical polishing:
The purpose of leveling and polishing is achieved through the oxidation-reduction reaction of metal in a chemical medium during chemical polishing. Its advantage is that chemical polishing has nothing to do with the hardness of the metal, the polishing area and the structure shape. All parts in contact with the polishing liquid are polished, no special complex equipment is required, and the operation is simple. It is more suitable for polishing complex structure titanium denture stents. However, the process 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. A better titanium chemical polishing liquid is prepared in a certain proportion of HF and HNO3. HF is a reducing agent, which can dissolve titanium metal and have a leveling effect. The concentration is less than 10%. HNO3 has an oxidizing effect to prevent excessive dissolution of titanium and hydrogen absorption. , At the same time can produce bright effect. Titanium polishing solution requires high concentration, low temperature and short polishing time (1～2min).
2. Electrolytic polishing:
It is also called electrochemical polishing or anodic dissolution polishing. Due to the low conductivity of the titanium alloy tube, the oxidation performance is very strong. The use of water-containing acid electrolyte such as HF-H3PO4, HF-H2SO4 electrolyte can hardly polish titanium. After the external voltage, the titanium anode is oxidized immediately, making the anode dissolution impossible. However, the use of anhydrous chloride electrolyte under low voltage has a good polishing effect on titanium. Small specimens can be mirror polished, but for complex restorations, it is still not possible to achieve complete polishing. Maybe you can change the shape of the cathode and add the cathode The method that can solve this problem needs further study.
