Embedding material impact on the physical and chemical properties of titanium tube casting quality

In recent years, with the introduction of National Laboratory " metal precision thermal processing ," a water-cooled copper crucible induction melting furnace , our group has invested major forces units alloy water-cooled copper crucible induction melting (IsM) thermodynamics and kinetics , and achieved some results. Now be summarized in order to communicate with readers , and jointly promote the development of titanium industry.
    The book is a national "Ninth Five " key books . This paper focuses on titanium melt composition, titanium foundry control of the main line , in theory, more in-depth analysis of the system ISM smelting process titanium alloy melt composition influence factors and the role of law in temperature, and several commonly used titanium alloy analyzed. The book is divided into eight chapters , of which the first chapter introduces the features and titanium smelting technology ; second, third and sixth chapters are discussed the impact of volatile behavior of titanium alloy melt titanium investment casting composition of alloying elements , interstitial elements in titanium melting body dissolved in class skull formation mechanism ; fourth and fifth chapters ISM titanium smelting process gives the temperature field numerical simulation model and process parameter optimization design ; Chapter VII of the smelting process ISM exists a theoretical risk analysis ; Chapter VIII describes some examples of titanium smelting .

The crystal structure of titanium

Titanium with two different allotropic forms, low (< 882.5 C) stable state for alpha and dense row of the six party system; high temperature stable state for beta type. Body centered cubic.

  The lattice parameter alpha -Ti, 25 DEG,Ca＝2.9503±0.0004Å，c＝4.6832
±0.0004Å，c / a=1.5873±0.0004. Because the ratio of c/a alpha -Ti less than ideal spherical 1.633 axle ratio, so ti is malleable metal. The impurities present alpha in -Ti have a significant impact on the lattice structure of trace oxygen, the presence of nitrogen makes lattice growth along the c axis, cause the increase of C value and a value, in fact almost does not change.

Clinical application hindering of pure titanium prosthesis

In the roasting temperature casting shrinkage crystal transition volume change larger material can compensate the pure titanium, but easy to molten titanium reacts, the fouling layer formation of thick, affect the physical and mechanical properties of titanium prosthesis.

  At present can not only solve the titanium restoration precision, but also can reduce the pollution of Titanium casting has not been reported buried materials package, so about titanium casting investment research and development work is still a hot spot.

  In addition, the current commercial better performance of several ti investments are expensive, the manufacturers instructions also require the use of casting system of the factory matching (Titanium alloy valve, titanium), this has to some extent increased titanium restoration cost, finally make titanium restorations be roughly the same price with the use of expensive metal material prices.

  This hinders widely used in clinical application of pure titanium prosthesis.

Precision casting of titanium denture

Titanium alloy valve resources in China ranks first in the world, for dental titanium denture to provide the most favorable conditions. Currently the most common titanium denture processing technology, is still using the method of precision casting, and PFM crown and bridge can be made into various bracket and titanium removable denture fixed denture base crown.

  However, molten titanium precision casting and oxygen, nitrogen, hydrogen and other elements, oxides, chlorides, fluorides are able to react strongly, resulting in Ti investments (mold material selection very difficult).

Titanium denture success

Gold titanium check valve is suitable for making dentures, but the price is expensive, difficult to widely used. Cobalt chromium, nickel chromium alloy although cheap, but because of containing Ni, Cr, Co and other harmful elements, so not ideal material for making dentures.

  Therefore, the developed countries from the 80's of the last century began to study the Titanium alloy valve restorations, both the processing technology of titanium teeth or with matching equipment, equipment, have made gratifying achievements.

Oral application of pure titanium and titanium alloys

With the progress of the society, more and more materials for oral shell making dentures, metal, plastic, composite resin, ceramic etc..

  The metal material used for making dentures are mainly co Cr alloy, Ni Cr alloy, near alloy, this year and the emergence of pure titanium and Titanium alloy valve.

How to maintain the accuracy of the castings

In order to avoid too fast reaction speed to make Titanium castings dissolved amount of difficult to control, not conducive to maintaining the precision of castings, and if the hydrogen permeation increases, also will make the mechanical properties of castings variation.

  In the practical application, the use of lower concentrations of HF and HNO3 mixed acid to remove surface contamination layer is Aerospace titanium castings suitable.

Complete removal of surface contamination layer of titanium castings

Experiments have confirmed the elevated HF concentration, the reaction is speeded up obviously, and the 0.6MPa pressure blasting test pieces in a concentration of 1mol:5mol mixed acid solution soak for 60sec can be completely remove surface contamination layer.

  Therefore, the use of high pressure blast Titanium castings soaked in low concentration of HF and HNO3 mixed acid solution in 60sec can achieve the purpose of complete removal of surface contamination layer.

The dissolved amount of titanium

The concentration of titanium alloy casting in HF and HNO3 in the mixed solution with HF and HNO3 dissolved quantity related, the former molar concentration is high, dissolving capacity of the latter molar concentration is low.

  Lower concentration of HF on the dissolution of Titanium  amount is small, but can get the surface is smooth, and easy to master the dissolved quantity.

How to overcome the uniform mechanical grinding removal

Because the thickness of contaminated layer of pure titanium surface with Titanium casting system for casting is about 75 mu m, and uniform thickness, so the removal of pollution layer of pure titanium surface with uniform removal method when the surface layer microstructure is more suitable .

  The industry usually uses acid dissolving and removing contaminated metal surface layer(Suan Xi), its purpose is to make the metal surface and evenly dissolved, removal of oxide skin, can effectively uniform removal of pollution layer of cast pure titanium  surface, to overcome the mechanical grinding removal amount is not uniform.

Experimental study on pure titanium castings surface nitriding treatment

Surface modification of pure titanium castings for this study, in order to enhance its wear resistance and corrosion resistance, improve the surface color, so as to improve the performance and aesthetic effect of titanium prosthesis.

   Plasma nitriding of pure titanium casting experiment of puretitanium TA2 conventional  casting,

 mechanical polishing and then exposed to plasma nitriding furnace, glow plasma nitriding treatmentin ammonia atmosphere, glow voltage 700V, current of 13 ~ 15A, 150Pa vacuum nitriding furnace,temperature 700 C, permeability nitrogen time 1 ~ 4h, the study of plasma nitriding the pure titaniummicro hardness, wear resistance and corrosion resistance effect.

Pure titanium castings surface nitriding

Ti has good mechanical properties, chemical stability and biocompatibility, have been widely used in aerospace, marine, military and biomedical fields. Pure titanium in oral medicine is mainly used for making denture, crown and fixed bridge, orthodontic bracket,implant and titanium porcelain etc..

  Titanium  is self passivation of metal, a layer of stable and dense oxide film formed surface at room temperature, so it has good corrosion resistance. But pure titanium low hardness, wear resistance is poor, pure titanium prosthesis to function in oral BOC,titanium oxide films on the surface of friction force, shearing force under stress, prone to scratches and wear, dental caries preventive agents such as fluoride toothpaste, gel on the film also has a certain role in bad breaking.

Effects of fluoride on the corrosion resistance of pure titanium castings

Pure titanium due to good biocompatibility is widely applied in the field of oral medicine, such as titanium, titanium porcelain crown bridge bracket and titanium implant etc.. Its good biocompatibility because the pure titanium surface with a layer of compact oxide film, good chemical stability, so as to protect the pure titanium substrate from being corrosion preventing precipitation of titanium ion.

  But co existed in the fluoride ion and hydrogen ion condition, the surface of pure titanium oxide film is dissolved, the decrease of the corrosion resistance,resulted in the precipitation of titanium ion, likely to cause adverse effects on the surrounding tissue and human body.

Effects of titanium nitride coating on corrosion resistance of pure titanium castings

Pure titanium as a biological material, low density, good mechanical performance, strong corrosion resistance, good biology compatibility, so it is widely used in the field of oral medicine. However, pure titanium as the material of denture, poor wear resistance, color appearance, susceptible to fluoride corrosion.

  The academic topic related research has been conducted on the plasma nitriding / titanium nitride coating composite surface treatment, surface properties of titanium castings of biological safety, fungal adhesion properties and clinical application effect, experiment is mainly through the potentiodynamic polarization technique and ion release experiment was conducted to observe the effect of composite surface treatment of titanium castings in corrosion resistance of fluorine environment the application of dynamic.

The titanium alloy can also be used for artificial bone

In addition, because the titanium alloy also has good compatibility with the human body, so the Titanium Welded Tubes alloy can also be used for artificial bone. The corrosion resistance of titanium zirconium nitrate and hydrogen titanium zirconium oxide is a kind of application in the atomic energy industry and used as a corrosion resistant chemical materials under high temperature and pressure, but in the lively after sodium solution. Then, the titanium hydroxide solution added live wave zirconium nitrate solution, will find that to shut sb. titanium zirconium nitrate. As you can see, there are the obvious layered graph, the above is zirconium nitrate, below is the titanium hydroxide. We know, Titanium Welded Tube hydroxide is less than the density of zirconium nitrate, but can still maintain the obvious stratification, and zirconium nitrate stay in the upper, which proves that the corrosion resistance of titanium. According to the experiment, titanium into the ocean of annual 20~50 won't be corroded.

Heat treatment of titanium and titanium alloys have Aerospace titanium castings

Heat treatment of titanium alloys are: (1) stress relief annealing: the aim is to eliminate or reduce the residual Aerospace titanium castings stress generated during processing. Prevent chemical erosion and reduce distortion in some corrosive environments. (2) complete annealing: the purpose is to obtain a good toughness, improved workability, and is conducive to further processing and to improve the dimensional stability titanium precision casting of the organization. (3) solution treatment and aging: The purpose is to increase its strength, α β titanium and titanium alloys can not be stable strengthening heat treatment, carried out only in the production of annealing. α + β titanium alloy The metastable β titanium alloy containing a small amount of gold can be prepared by α-phase solid solution treatment aerospace castings and aging the alloy is further strengthened.

Application of titanium and its alloys Aerospace titanium castings

Because of the dense titanium light weight, high strength than aluminum, can be maintained at a high temperature Aerospace titanium castings than aluminum and high-strength aerospace industry are highly valued. Given the density of 57% of titanium steel, Its (strength / weight ratio or strength / density ratio of them registering intensity) than high strength, corrosion resistance, anti-oxidation, anti-fatigue capabilities are strong, 3/4 titanium alloys used in aerospace structures for the generation of alloys Structural materials table, 1/4 is mainly used as corrosion resistant alloys. Titanium has a low strength and high plasticity, medium and high strength of the strong points for the 200 (low intensity) to 1300 (high strength) MPa, but in general can be seen as a high-strength titanium alloy. They are considered to be more than Strong strength aluminum alloy for high strength titanium precision casting has been completely on some models can replace steel. And the strength of the aluminum alloy at a temperature above 150 ℃ decreased rapidly compared certain titanium Gold at 600 ℃ still maintain good strength. In addition to strength, according to purpose can be divided into heat and corrosion resistance, low temperature and special features (such as TiNi shape memory alloy, TiFe hydrogen storage alloys) and other alloys, the phase composition can be divided by α, α + β and β and near-α, and several types of metastable. Alloy production so far has more than 100 species, only about 10 species widely used in industry. Which make the structure of Ti alloy -6Al-4V titanium alloy accounted for in the whole sale market of 60%, ranking the leading position, followed by Ti-5Al-2.5Sn, its long-term working temperature up to 500 ℃ (780 ~ 980 MPa strength) . However, there are two major factors that make titanium resource-rich elements can not become commonly used metals. The first is cost. According to the U.S. market price per pound (1 pound = 0.45 kg) of titanium ingot 8 ~ $ 12, aluminum ingots at $ 1.00 ~ 1.30 / lb, carbon steel is $ 0.20 ~ 0.40 / lb. But the main factor is the active titanium itself extremely difficult to deal with. Furnace atmosphere must Strict control, welding must be carried out in an inert atmosphere. Titanium high activity, low thermal conductivity, large deformation resistance, poor temperature plasticity, deformation process is not only easy to bond with the mold, especially When there is not the tool and the machining is bonded to the abrasive surface tends to thermal processing, the manufacturing lot of the standard structure of titanium scrap debris generated, so-called residual titanium. General forged titanium ingot processing can be Produce 70% of the residual titanium, sometimes up to 90% of this figure. To reduce the burden caused by the high cost, while the development of the residual titanium processing technology, on the other hand the development of near net shape, super plastic forming, precision casting and powder metallurgy and hot isostatic pressing And other high-tech diffusion bonding. Such as processed by milling, shaping, sintering or hot isostatic pressing method of consolidation near net shape powder metallurgy products as parts, material utilization up to 80 %, Both to reduce the material consumption, but also significantly reduces the amount of machining. Another example is the aerospace castings large-scale thin-wall casting technology in titanium alloy, titanium castings performance close to titanium forgings made The reduced by about 50%. The main areas of consumption titanium and titanium alloy is first aviation industry. 1980s, American aviation industry accounts for 74.8% of the titanium with a titanium total amount, Russia, the United Kingdom, also mainly for Aviation Industry, Japan 90% of titanium used in civilian industry. In recent years, titanium used in the aerospace industry in a non-growing aerospace continued to hold the "flagship" status.

Porcelain teeth are made of pure titanium What are the benefits Aerospace titanium castings

For titanium porcelain teeth how much you have to know it, is a titanium metal implant into the body of modern medicine most widely used metals, accounting for more than 80%; due to Aerospace titanium castings titanium with no human contact sensitization, carcinogenicity , The distortion caused by the phenomenon, with bone tissue, epithelium, connective tissue good combination, so it is best biocompatible metallic materials; same titanium taken in the field of production of dental prosthesis Got great results: titanium porcelain teeth, titanium steel care In addition to titanium dental porcelain affinity with excellent organization, it also has the following advantages: 1, light weight titanium porcelain teeth: a small proportion of titanium, titanium porcelain teeth proportion of its gold 1/4, 1/2 cobalt-chromium alloy, titanium thus making porcelain teeth will be much titanium precision casting lighter weight can To reduce the burden on the remaining tissue in the mouth, titanium porcelain teeth also has a better comfort. 2, low thermal conductivity: crowns made with titanium, titanium porcelain teeth can better isolate hot and cold stimulation, help protect the pulp, titanium porcelain teeth eating hot or cold foods when not There will be a sense of pain. 3, no taste disturbance: Titanium has good stability, not titanium metal porcelain teeth in the mouth feel of the taste, the taste does not cause interference. 4, the transmission X-ray: titanium titanium porcelain teeth on a semi-transmissive X-ray, wearing crowns made of pure titanium, the X-line, you can check whether the decay inside the crown, so early detection , Early treatment, which is aerospace castings the other metal materials for the production of titanium porcelain denture teeth do not have advantages.