Due to the low density of titanium alloy, the liquid flow inertia is also low, and the low fluidity of molten titanium causes a low casting flow rate. Titanium castings' surface and internal surfaces inherently contain pores and other flaws, having a significant negative impact on the quality of titanium castings. The following titanium forging surface treatment tips are arranged in the following order:
removing the surface reaction layer first
The primary element influencing the physical and chemical characteristics of titanium castings is the surface reactive layer. To produce an acceptable polishing effect, the surface contamination layer must be entirely removed prior to grinding and polishing titanium castings. Pickling can be used to thoroughly remove the titanium's surface reaction layer following sandblasting.
1. Sandblasting: White corundum coarse blasting works well for the sandblasting treatment of titanium castings, and the pressure used is lower than that used for non-precious metals, which is typically kept below 0.45Mpa. Because when the injection pressure is too high, the sand hitting the titanium surface creates intense sparks, and the temperature increase might react with the titanium surface, causing secondary pollution and degrading the surface quality. Only the sticky sand, surface sintered layer, and a portion of the oxide layer on the casting surface should be removed during the 15–30 second period. It is important to swiftly eliminate the remaining reactive layer structure on the surface using chemical pickling.
2. Pickling: Pickling can swiftly and fully remove the surface response layer while preventing additional materials from contaminating the surface. Both the HF-HCl system and the HF-HNO3 system can be used to pickle titanium, however the HF-HCl system absorbs more hydrogen than the HF-HNO3 system does. As a result, the concentration of HNO3 can be adjusted to lessen hydrogen absorption and brighten the surface. HF is often present in concentrations of between 3% and 5%. HNO3 should be present in concentrations of 15% to 30%.
two：Treatment of casting flaw
Hot isostatic pressing technology can eliminate internal holes and shrinkage flaws, but it affects the precision of dentures. Z will then undergo laser welding, surface polishing to remove any exposed pores, and an X-ray test. Laser local welding may immediately fix surface porosity flaws.
Three: polishing and grinding
1. Mechanical grinding: Due to titanium's high chemical reactivity, low thermal conductivity, high viscosity, and low mechanical grinding ratio, ordinary abrasives shouldn't be used for titanium grinding and polishing. Instead, superhard abrasives with good thermal conductivity, like diamond and cubic boron nitride, are best. Polishing linear speed is typically 900–1800 m/min. Otherwise, titanium's surface is prone to microcracks and grinding burns.
2. Chemical polishing: To achieve the goal of leveling polishing, the metal undergoes a REDOX reaction in a chemical medium. Its benefits include the fact that chemical polishing has nothing to do with the metal's hardness, polishing area, and structure shape, where the parts in contact with the polishing liquid are polished, the lack of specialized complex equipment needed, the simplicity of operation, and its suitability for complex titanium denture support structures. It is necessary to have a good polishing effect without compromising the precision of the denture since the process parameters of chemical polishing are challenging to control.
Four, coloring
Surface nitriding treatment, atmospheric oxidation, and anodic oxidation surface coloring treatment can be used to create a light yellow or golden yellow surface, improving the appearance of titanium dentures and preventing yellowing of titanium dentures under natural conditions. The anodizing process creates color naturally by using the titanium oxide film's interference with light. By altering the tank voltage, it may create vibrant colors on the titanium surface.
