Titanium easily reacts with elements such as O, H, N in the air and Si, Al. Mg in the embedded materials at high temperatures, forming a surface contamination layer on the surface of the casting, which deteriorates the excellent physical and chemical properties and hardness.
The density of titanium is small, so the inertia of the titanium liquid flows is small, and the fluidity of the molten titanium is poor, resulting in a low casting flow rate. The casting temperature and mold temperature difference (300°C) is large, cooling is fast, casting is carried out in a protective atmosphere, and defects such as Titanium Bar and internal voids are inevitable on the surface of titanium castings, which has a great influence on the quality of castings.
Therefore, the surface treatment of titanium castings is more important than other dental gold, due to the unique physical and chemical properties of titanium, such as low thermal conductivity, low surface hardness, low modulus of elasticity, high viscosity, low electrical conductivity, and easy Oxidation, etc., which brings great difficulty to the surface treatment of titanium, it is difficult to achieve the desired effect by conventional surface treatment methods. Special processing methods and means of operation must be used.
The later surface treatment of the casting is not only to obtain a smooth and bright surface, to reduce the accumulation and adhesion of food and plaque, to maintain the balance of the patient's normal oral micro-ecology, but also to increase the aesthetics of the denture; more importantly, These surface treatments and modification processes improve the surface properties and suitability of the castings, and improve the physical and chemical properties of the dentures such as abrasion resistance, turbidity resistance and stress fatigue resistance.
Titanium Tube Gr5
First, the removal of the surface reaction layer
The surface reaction layer is the main factor affecting the physical and chemical properties of titanium castings. Before the titanium castings are polished and polished, it is necessary to completely remove the surface contamination layer to achieve a satisfactory polishing effect. The surface reaction layer of titanium can be completely removed by pickling after sand blasting.
Sand blasting: The blasting treatment of titanium castings generally uses white corundum coarse spray, such as Titanium Tube Gr5, the pressure of sand blasting is smaller than that of non-precious metals, generally controlled below 0.45Mpa. Because, when the injection pressure is too large, the surface of the sand is violently sparked on the surface of the titanium, and the temperature rise can react with the surface of the titanium to form secondary pollution, which affects the surface mass. The time is 15 to 30 seconds, and only the sand, the surface sintered layer and the part and the oxide layer on the surface of the casting can be removed. The remaining surface reaction layer structure should be quickly removed by chemical pickling. Pickling removes the surface reaction layer quickly and completely without contaminating the surface with other elements.
Second, the buried defects of casting
Internal air holes and shrinkage holes internal defects: can be removed by thermostatic pressure technology, but the accuracy of the denture will be affected. It is best to use X-ray flaw detection, the surface is removed from the exposed air holes, and the laser is used for repair welding. Surface porosity defects can be directly repaired by laser local welding.
Third, grinding and polishing
1. Mechanical grinding: Titanium has high chemical reactivity, low thermal conductivity, high viscosity, low mechanical grinding ratio, and easy to react with abrasives. Ordinary abrasives are not suitable for grinding and polishing of titanium, preferably with good thermal conductivity. Superhard abrasives such as diamond, cubic boron nitride, etc.
2. Ultrasonic grinding: By ultrasonic vibration, the abrasive grains between the grinding head and the surface to be polished are moved relative to the surface to be polished to achieve the purpose of grinding and polishing. This has the advantage that the grooves, sockets and stencils that are not ground by conventional rotating tools are easy, but the grinding effect of larger castings is not satisfactory.
3. Electrolytic mechanical composite grinding: Electrolytic grinding tools are used to apply electrolyte and voltage between the grinding tool and the grinding surface. Under the joint action of mechanical and electrochemical polishing, the surface roughness is reduced to improve the surface gloss.
The above is the description of titanium surface treatment technology in Titanium Alloy Bar Factory, hoping to help everyone.