Baoji Lichuang Titanium Industry Co., Ltd. has established a strict and effective quality management system and has passed the ISO9001:2008 standard quality management system certification. Products can be produced according to GB, GJB and ASTM, AME, JIS, ASME and other standards, or according to the user's special,Special requirements for organizing production. Strictly control risks, strengthen processes, continuous improvement, improve quality and efficiency, and customer satisfaction.
|Ten characteristics of titanium|
|First, the ten characteristics of titanium|
◆ Low density and high specific strength: The density of metallic titanium is 4.51g/cm3, which is higher than aluminum and lower than steel, copper and nickel, but the specific strength is at the top of metal.
◆ Corrosion resistance: Titanium is a very active metal with a low equilibrium potential and a high degree of thermodynamic corrosion in the medium. In practice, however, titanium is very stable in many media, such as titanium, which is resistant to corrosion in media such as oxidizing, neutral, and weakly reducing.
◆ Good heat resistance: The new titanium alloy can be used for a long time at 600 °C or higher.
◆ Good low temperature resistance: Low temperature titanium alloys represented by titanium alloys such as TA7 (Ti-5Al-2.5Sn), TC4 (Ti-6Al-4V) and Ti-2.5Zr-1.5Mo, whose strength increases with decreasing temperature But the plasticity changes are not big. It maintains good ductility and toughness at low temperature of -196-253 °C, avoids cold and brittleness of metal, and is an ideal material for equipment such as cryogenic vessels and tanks.
◆ Strong anti-damping performance: After being subjected to mechanical vibration and electrical vibration, metal titanium has the longest vibration decay time compared with steel and copper metal.
◆ Tensile strength is close to its yield strength: This property of titanium indicates that its yield ratio (tensile strength/yield strength) is high, indicating that the metal titanium material has poor plastic deformation during forming. Since the ratio of the yield limit of titanium to the modulus of elasticity is large, the resilience of titanium during molding is large.
◆ Good heat transfer performance: Although the thermal conductivity of titanium is lower than that of carbon steel and copper, the wall thickness can be greatly reduced due to the excellent corrosion resistance of titanium, and the heat exchange between surface and steam is droplet condensation. In the heat group, the surface is not fouled and the thermal resistance can be reduced, so that the heat exchange performance of titanium is remarkably improved.
◆ Low modulus of elasticity: The modulus of elasticity of titanium is 106.4 GMPa at room temperature, which is 57% of steel.
◆ Suction performance: Titanium is a very chemically active metal that reacts with many elements and compounds at high temperatures. Titanium inhalation mainly refers to the reaction with carbon, hydrogen, nitrogen and oxygen at high temperature.
|Titanium surface treatment technology|
|Titanium easily reacts with elements such as O, H, N in the air and Si, Al, Mg, etc. in the air at high temperatures, forming a surface contamination layer on the surface of the casting, which deteriorates the excellent physical and chemical properties and hardness. Increase, plasticity, elasticity, and brittleness increase.|
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 the mold temperature difference (300 ° C) are large, the cooling is fast, the casting is carried out in a protective atmosphere, and defects such as pores are inevitable on the surface and inside of the titanium casting, which has a great influence on the quality of the casting.
Therefore, the surface treatment of titanium castings is more important than other dental alloys. Due to the unique physical and chemical properties of titanium, such as low thermal conductivity, low surface hardness and low modulus of elasticity, high viscosity, low electrical conductivity and easy oxidation. Etc. This brings great difficulty to the surface treatment of titanium, and 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, corrosion resistance and stress fatigue resistance.
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 sandblasting.
1. Sandblasting: The sandblasting treatment of titanium castings is generally better with white corundum coarse spraying. The pressure of sandblasting is smaller than that of non-precious metals, generally controlled below 0.45Mpa. Because, when the injection pressure is too large, the sand impacts the titanium surface to produce a fierce spark, and the temperature rise can react with the titanium surface to form secondary pollution, which affects the surface quality. 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.
2. Pickling: Pickling can quickly remove the surface reaction layer completely without contaminating the surface with other elements. Both HF-HCl and HF-HNO3 acid pickling solutions can be used for pickling of titanium, but HF-HCl acid pickling liquid absorbs a large amount of hydrogen, while HF-HNO3 pickling liquid has a small hydrogen absorption amount, which can control HNO3. The concentration of the hydrogen is reduced, and the surface can be brightly treated. Generally, the concentration of HF is about 3% to 5%, and the concentration of HNO3 is about 15% to 30%.
Second, the processing of casting defects
Internal air holes and shrinkage holes internal defects: can be removed by hot isostatic pressing, 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 pores, 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. Hard abrasives, such as diamond, cubic boron nitride, etc., the polishing line speed is generally 900~1800m/min. Otherwise, the titanium surface is prone to burn and microcracks.
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 polishing and polishing. This has the advantage that the grooves, sockets and stencils that are not ground by conventional rotary tools become easier, but the larger castings are 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 electrolyte is 0.9NaCl, the voltage is 5v, and the rotation speed is 3000rpm/min. This method can only grind the plane, and the grinding of the complex denture bracket is still in the research stage.
4. Barrel grinding: Using the centrifugal force generated by the revolution and rotation of the grinding barrel, the denture in the barrel and the abrasive are relatively frictionally moved to reduce the surface roughness. Grinding automation, high efficiency, but can only reduce the surface roughness and can not improve the surface gloss, the grinding accuracy is poor, can be used with deburring and rough grinding before denture polishing.
5. Chemical polishing: Chemical polishing is achieved by the redox reaction of metal in a chemical medium. The advantage is that the chemical polishing is independent of the hardness, polishing area and structural shape of the metal. Where the contact with the polishing liquid is polished, it does not require special complicated equipment, and is easy to operate, and is suitable for polishing the complex structure titanium denture bracket. 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. The best titanium chemical polishing liquid is prepared by HF and HNO3 in a certain proportion. HF is a reducing agent, which can dissolve titanium metal and play a leveling effect. The concentration is<10%. HNO3 acts as an oxidation to prevent excessive dissolution and hydrogen absorption of titanium. At the same time, it can produce a brightening effect. Titanium polishing fluid requires high concentration, low temperature and short polishing time (1~2min.).
6. Electrolytic polishing: also known as electrochemical polishing or anodic dissolution polishing. Due to the low conductivity of titanium, the oxidation performance is extremely strong. Alkaline electrolytes such as HF-H3PO4 and HF-H2SO electrolytes can hardly polish titanium. After the external voltage is applied, the titanium anode is immediately oxidized, and the dissolution of the anode cannot be performed. However, the use of anhydrous chloride electrolyte at low voltage, has a good polishing effect on titanium, small specimens can be mirror polished, but for complex restorations can not achieve the purpose of complete polishing, perhaps changing the shape of the cathode and additional cathode The method can solve this problem and needs further research.
Fourth, the surface modification of titanium
1. Nitriding: A chemical yellow heat treatment technique such as plasma nitriding, multi-arc ion plating, ion implantation and laser nitriding is used to form a gold-colored TiN coating on the surface of the titanium denture, thereby improving the wear resistance, corrosion resistance and resistance of the titanium. Fatigue. However, the technology is complicated and the equipment is expensive. It is difficult to achieve clinical application for surface modification of titanium dentures.
2. Anodizing: The anodizing technique of titanium is relatively easy. In some oxidizing media, the titanium anode can form a thick oxide film under the action of applied voltage, thereby improving its corrosion resistance, wear resistance and weather resistance. The anodized electrolyte generally uses H2SO4, H3PO4 and an aqueous organic acid solution.
3. Atmospheric oxidation: Titanium can form a thick and strong anhydrous oxide film in high temperature atmosphere, which is effective for comprehensive corrosion and crevice corrosion of titanium. The method is relatively simple.
In order to increase the aesthetics of the titanium denture and prevent the discoloration of the titanium denture under natural conditions, the surface nitriding treatment, atmospheric oxidation and anodizing surface treatment can be used to form a pale yellow or golden yellow surface to improve the titanium denture. Aesthetic. The anodizing method utilizes the interference effect of the oxide film of titanium on light, and naturally develops color, and can form a colorful color on the surface of titanium by changing the cell voltage.
Sixth, other surface treatment
1: Surface roughening: In order to improve the bonding performance between titanium and the facing resin, the surface of the titanium must be roughened to increase the bonding area. Clinically, sandblasting roughening treatment is often used, but sand blasting will cause aluminum oxide contamination on the titanium surface. We use oxalic acid etching method to obtain good roughening effect, and the surface roughness (Ra) can be up to 1.50 after etching for 1 hour. ±0.30μm, etching 2h Ra is 2.99±0.57μm, more than double the Ra (1.42±0.14μm) of sandblasting alone, and the bond strength is increased by 30%.
2: Surface treatment against high temperature oxidation: In order to prevent the rapid oxidation of titanium at high temperatures, titanium silicon compounds and titanium aluminum compounds are formed on the surface of titanium to prevent oxidation of titanium at temperatures above 700 °C. This surface treatment is very effective for the high temperature oxidation of titanium. Perhaps the coating of such compounds on the surface of titanium is beneficial to the combination of titanium and porcelain, and further research is needed.
|Application of titanium and titanium alloy|
|Titanium||Brand||Main characteristics||Use example|
|Iodine titanium||TAD||This is a high-purity titanium obtained by the iodide method, so it is called iodine titanium, or chemically pure titanium. However, there are still some interstitial impurity elements such as oxygen, nitrogen and carbon, which have a great influence on the mechanical properties of pure titanium. As the purity of titanium increases, the strength and hardness of titanium decrease significantly. The characteristic is that the chemical stability is very good, but the strength is very low.||Due to the low strength of high-purity titanium, it has little significance as a structural material and is rarely used in industry. Industrially pure titanium and titanium alloys are currently widely used in the industry.|
|Industrial pure titanium||TA1|
|Industrial pure titanium differs from chemically pure titanium in that it contains more oxygen, nitrogen, carbon and various other magazine elements (such as iron, silicon, etc.), which is essentially a low alloying titanium alloy. Compared with chemically pure titanium, its mechanical properties and chemical properties are similar to those of stainless steel due to its high content of magazine elements (but its strength is still low compared with titanium alloy).|
Industrial pure titanium is characterized by low strength, good plasticity, easy processing, good stamping, welding and cutting process; good in atmospheric, seawater, wet chlorine and oxidizing, neutral and weak reducing media. The corrosion resistance and oxidation resistance are superior to most of the stinky solid stainless steels but the heat resistance is poor and the use temperature is not too high.
Industrial pure titanium is divided into three grades TA1.TA2 and TA3 according to its impurity content. The interstitial impurity elements of these three industrial pure titanium are gradually increased, so the mechanical strength and hardness thereof are also gradually increased, but the plasticity and toughness are correspondingly decreased. The pure titanium commonly used in the industry is TA2 because of its moderate corrosion resistance and comprehensive mechanical properties. TA3 can be used when the corrosion resistance and strength are high. TA1 can be used for better forming properties.
|(1) It is mainly used as stamping parts and corrosion-resistant structural parts with a working temperature of less than 360 degrees, but which is not strong but requires high plasticity, such as: skeleton of aircraft, engine accessories, seawater corrosion resistant pipes, valves, pumps for ships And water belts. Desalination system components, chemical heat exchangers. Pumps, distillation towers, coolers, mixers, tees, impellers, solid parts, ion pumps, compressor valves and diesel engine pistons, even Rod, leaf spring, etc.|
(2) TA1.TA2 has an iron content of 0.095%, an oxygen content of 0.08%, a hydrogen content of 0.0009%, a nitrogen content of 0.0062%, a good low temperature toughness and a high low temperature strength, which can be used as -259 °C. The following low temperature structural materials.
|α titanium alloy||TA4||These alloys have an α-type single-phase state at room temperature and use temperature, and cannot be heat-treated (follow-up is the only treatment), and mainly rely on solid solution strengthening. The room temperature strength is generally lower than that of β-type and α+β-type titanium alloys (but higher than industrial pure titanium), while the strength and enthalpy change at high temperature (500 ° C 600 ° C) is the highest among the three types of titanium alloys, and The structure is stable, the oxidation resistance and the welding performance are good, the corrosion resistance and the machinability are also good, but the plasticity is low (the thermoplastic is still good) and the room temperature punching performance is poor. Among them, TA7 is the most widely used, which has medium strength and sufficient plasticity in the annealed state. It has good welding performance and can be used below 500 ° C. When the content of interstitial impurities (oxygen, hydrogen, nitrogen, etc.) is extremely low, It also has good toughness and comprehensive mechanical properties when it is ultra-low temperature. It is one of the excellent ultra-low temperature alloys.||The tensile strength is slightly higher than that of industrial pure titanium, and it can be used as a structural material of medium strength range. It is mainly used as a welding wire in China.|
|For parts and weldments working in corrosive media below 400 °C, such as aircraft skins, skeleton parts, compressor casings, blades, ship parts, etc.|
|TA7||Long-term working structural parts and various die forgings below 500 °C can be used up to 900 °C for short periods of time. It can also be used as an ultra-low temperature (-233 ° C) component (such as a container for ultra-low temperature).|
|TA8||Long-duration parts at 500°C can be used to make engine compressor discs and blades. However, the structural stability of the alloy is poor. There are certain restrictions on the use.|
|βTitanium alloy||TB2||The main alloying elements of these alloys are β-stabilizing elements such as molybdenum, chromium and vanadium. It is easy to keep the high-temperature β phase to room temperature during normalizing or grading, and obtain a stable β single-phase structure, so it is called β. Type titanium alloy. The β-type titanium alloy can be heat-treated and strengthened, has high strength, and has good welding performance and pressure processing performance; but the performance is not stable enough, and the smelting process is complicated, so the application is not as extensive as the α-type, α+β-type titanium alloy.|| |
Parts working below 350 °C are mainly used to manufacture all kinds of sheet metal stampings and weldments for overall heat treatment (solidification and aging); heavy-duty rotating parts such as compressor blades, wheels, shafts, etc., and components of aircraft Wait. The alloy of TB2 is generally delivered under the condition of solid solution treatment, and then used for solidification and aging.
|Such alloys are α+β-type two-phase structures at high temperatures, hence the name α+β-type titanium alloys. It has good comprehensive mechanical properties, most of which can be heat-treated and strengthened (but TC1, TC2, TC7 can not be heat-treated and strengthened), with good forging, stamping and welding properties, machinable processing and high room temperature strength. Below 150500 degrees and has good heat resistance, and some (such as TC1, TC2, TC3, TC4) have good low temperature toughness and good resistance to seawater stress corrosion and resistance to hot salt stress corrosion.|