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.

Titanium casting Condensing shrinkage

Although Japan through years of research, introduced the Titanium 
 -vest, Titanium-vest-D (Ohara Co.), Selevest-DM, Selevest-D (Center for rotating, the United States has Noyes Vinh phuc) Tycast Mold (Pentron Co.), Germany Tancovest (Bego Co.), Rematitan plus (Dentaurum Co.) and other commercial products, although all have their own advantages, but also the existence of their own shortcomings, such as the pollution layer too thick and lack of precision castings.

  Theory and molten titanium oxide was blunt in calcination temperature shape variables are not large, can not be compensated completely condensed shrinkage Titanium casting process

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.

Acid pickling of pure titanium castings

The dissolved quantity of HF solution at room temperature for titanium is far greater than the HCL and H2SO4 solution, and low concentration of HF can be 1.5% or 2.5% make Titanium  bulk dissolved in a very short period of time, the rapid improvement of surface roughness, surface hardness is decreased.

  For the titanium and its alloys in HF solution at room temperature can be a lot of soluble H2 (analytic 6HF+2Ti=2TiF3+3H2 arrow), and a passivation reaction in HNO3 solution,the chemical properties of the surface of the passivation layer is extremely stable.

  Visiblly, the corrosion rate of HNO3 solution is added into the HF solution can not only control of titanium, but can be significantly reduced due to Titanium casting surface hydrogen permeation and lead to the risk of hydrogen embrittlement, acid wash so experiment using mixed acid solution of HF and HNO3 of pure titanium castings.

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.

The first domestic dental titanium casting machine

Although the The Fourth Military Medical University and Henan Luoyang Jianxi light industry general machinery factory jointly developed the first domestic dental Titanium alloy valve, and in the domestic sales of 23 units, and laid a solid foundation for Titanium  denture in China extensively,

   But due to the Department of Stomatology crowns and bridges of the high accuracy requirement, the internal (shaft wall) fit < 73µm, marginal fit < 100 µm, there is no domestic embedding material can meet this demand.

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.

Titanium and titanium alloy

Titanium and titanium alloy, light weight, high strength, high yield ratio, non magnetic, biologically inert, and has excellent corrosion resistance. In seawater environment, titanium and Titanium castings almost no corrosion, corrosion resistance is excellent in most chemical medium. At present, with the progress of science and technology and all walks of life to the application of new materials to increase the strength, the necessary products of Titanium castings valve as the medium of various special environment and special fluid delivery system has been used. However, the fluid medium and environmental conditions in different areas and industries are not the same, performance requirements of the material used on different titanium valve. At the same time, because of the different components of Titanium precision castings alloy valveperformance requirements are different, different process, and to reduce the cost of parts needed to use alternative materials and other factors, the material has become one of the technical problems of first consideration must be titanium valve design and manufacturing, and suffer the widespread concern and attention. Industrial pure titanium refers to non titanium alloys with different Fe, C, N, O and other impurities content.

Titanium and titanium alloy of high strength

Titanium and titanium alloy of high strength, low density and other properties make it widely used in aerospace engineering. Such as various pipeline aircraft on the extensive use of titanium tube alloy valve, Titanium castingstype relates to the cut-off valve, check valve, needle valve, plug valve, ball valve and butterfly valve. Titanium valve as the key system components conveying fluid control titanium alloy pipe, widely used in chemical engineering. Valve valve with fasteners as important component, is also very important in valve design, manufacture. Implemented in a large PTA project mass production and application. Titanium valve is widely used in chemical industry, but must pay attention to its not suitable for any chemical medium. The hydrofluoric acid, hydrochloric acid, sulfuric acid and phosphoric acid and oxalic acid, formic acid, hot concentrated three chloroacetic acid, three trifluoroacetic acid and strong corrosive aluminum chloride, have severe corrosion effect of Titanium casting and titanium alloy, titanium valve is not suitable for this kind of chemical medium, should pay attention to in use.

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.

The strength of titanium

Titanium tensile strength up to 180kg/mm2. Some of the strength of the steel is higher than that of titanium alloy, but the titanium alloy than strength (tensile strength and density ratio) was more than the high quality steel. Titanium alloy with heat resistant strength, low temperature toughness and fracture toughness is good, so it is much used for aircraft engine parts and rocket, missile structure. Titanium alloy can also be used as a fuel and oxidizer tank and high pressure vessel. Now has a titanium alloy for manufacturing automatic rifle, the launch tube of mortar base plate and recoilless gun. In the oil industry mainly for various vessel, reactor, heat exchanger, distillation tower, pipe, pump and valve etc.. Titanium can be used as electrode and a power station condenser and environmental pollution control device. titanium alloy coils  nickel shape memory alloy has been widely used in instruments. In the medical treatment, titanium can be used as artificial bones and various utensils. Titanium or steelmaking deoxidizer and stainless steel and alloy steel components. Titanium dioxide pigment and paint is a good raw material. Titanium carbide, carbon (hydrogen) is a new type of titanium alloy sheets carbide materials. Titanium nitride color close to gold, widely used in decoration. Titanium and titanium alloys used in large quantities for the aviation industry, "space metal" known; in addition, is widely used in the shipbuilding industry, chemical industry, machinery parts manufacturing, telecommunications equipment, hard alloy, etc..

Titanium development

Through research, the author thinks that the development direction of titanium alloy is mainly: (1) standard evaluation of fire retardant properties of titanium alloy and method. Flame retardant performance evaluation of titanium alloy right is one of the key techniques of flame retardant titanium alloys, including the simulation methods and detection technology of combustion of titanium alloy. At present, the flame retardant titanium sheets performance evaluation method has no uniform standards, countries have adopted different methods to test. Flame retardant performance evaluation method of titanium alloy and therefore the formulation of a unified standard will effectively promote the national Titanium alloy valves exchange. (2) increase the mechanical aerospace titanium castings properties of titanium alloy. Compared with the titanium alloy, titanium alloy is poor mechanical properties, low working titanium alloy plates temperature. Research on how to improve the mechanical properties of this alloy for deeper. (3) reduce the cost of titanium alloy. Titanium alloy containing large amount of noble metal elements of V, resulting in higher costs, limiting its application. The domestic scholars have studied to replace V with Mo part of low price.

Titanium alloy plate prices

Titanium alloy plate at the current price trend is not particularly good, the recent domestic titanium plate market demand are relatively sluggish, prices remain low stage, the short term, the market price will be difficult to recover, the current 2mm pure titanium plates plate price in the 105-115 yuan / kg (15.51-16.99 dollars / kg). Titanium is a metallic element, grey, atomic number 22, relative atomic mass 47.87. Combustion in nitrogen, high melting point. Blunt titanium and titanium based alloy is a structure with new materials, mainly for the aerospace industry and marine industry.
Titanium density of 4.506-4.516 g / cubic centimeters (20 DEG C), higher than that of aluminum and iron, copper, nickel below. But in the first than the strength of the metal, is 3 times of stainless steel, is the aluminum alloy [colored business: 1.3 times of the aluminum alloy plate]. The melting point of 1668 - 4 DEG C, the latent heat of fusion of 3.7-5.0 kcal / atom, the boiling point of 3260 plus or minus 20 DEG C, the latent heat of vaporization of 102.5-112.5 kcal / atom, the critical temperature of 4350 DEG C, the critical pressure of 1130 atm. Poor thermal conductivity and conductive properties of Sunrui titanium coils , similar to or slightly lower than stainless steel, titanium superconductor, superconducting critical temperature of pure titanium 0.38-0.4K. At 25 DEG C, titanium heat capacity is 0.126 cards / atom and degree, 1149 card / molecular enthalpy, entropy is 7.33 cards / atom and degree, metal titanium is paramagnetic material, permeability is 1.00004. Titanium has plasticity, extending high pure titanium rate can reach 50-60%, section shrinkage rate of 70-80%, but low strength, not as structure material. Titanium in the presence of impurities, a great influence on the mechanical properties, especially the interstitial impurities (oxygen, nitrogen, carbon) can greatly improve the strength of titanium, significantly reduced its plastic. Good mechanical properties with titanium as a structural material, through strict control of the impurity content is appropriate and adding alloy elements and to achieve.

Titanium alloy

Titanium alloy is with titanium alloy added other elements. There are two kinds of different titanium crystal: 882 DEG C for close packed six party structure titanium, 882 DEG C beta titanium as the body centered cubic. Alloy elements according to their influence on the phase transition Titanium Ingot temperature can be divided into three categories:
A stable alpha phase, increase the phase transition temperature of the element as the alpha stable elements, aluminum, carbon, oxygen and nitrogen. The aluminum is the main alloy titanium alloy elements, it is to reduce the quality of the alloy at room temperature and high titanium alloy temperature strength, elastic modulus, increase proportion has obvious effect.
The stability of beta phase, reduce the transition temperature element for beta stable elements, can divide again isomorphous and eutectoid type two. The application of titanium alloy products, the former are molybdenum, niobium, vanadium; the latter with chromium, manganese, copper, iron, silicon, etc..