The use of Titanium

Currently, the production of titanium metal industry is to be Raul law, products of titanium sponge. Preparation is the traditional process of titanium sponge titanium by cast into ingots, and then processed titanium. Click the main steps to be made from titanium mining is the process:

Titanium -> Mining -> Beneficiation -> too concentrate -> enrichment -> Ti-rich material -> Chloride -> crude TiCl4-> Refined -> Pure TiCl4-> magnesium reduction -> titanium sponge -> Casting -> titanium ingots -> processing -> titanium or titanium parts if the above steps to get the rutile mining, enrichment is not necessary to go through, you can take direct chlorination of crude TiCI4. In addition, the casting operation should be a metallurgical process, but sometimes also included processes.

The above-described process refers to the process in terms of plastic working and casting. The plastic working method also includes forging, extruding, rolling, drawing and the like. It can be processed into a variety of sizes of titanium ingots cake timber, rings, plates, tubes, rods, profiles and other products, can also be made into various shapes casting parts, components.
Titanium and seamless titanium tube alloys have a large deformation resistance plastic processing; room temperature plasticity poor, yield strength and ultimate strength ratio is high, big rebound, notch sensitivity, deformation process easy and die bonding, heating time and easy adsorption of harmful gases and other characteristics, plastic working than steel, copper difficult.

Therefore, processing of titanium and titanium alloys thereof must consider these characteristics.

Titanium uses plastic processing, plus unlimited land size, but also to mass production, but a large amount of scrap lumber remnant low processing. Principles of titanium production process shown in Figure 1-1.

In response to these shortcomings medical titanium plastic processing, in recent years the development of titanium powder metallurgy process. Titanium powder metallurgy process and the same common powder metallurgy, the sintering must be carried out only under vacuum. It is suitable for the production of large quantities almost, small parts, especially for the production of complex parts. This method is almost no longer been processed, finished product rate, can make full use of titanium as raw material waste, and can reduce production costs, but can not produce large-size titanium member. Titanium powder metallurgy process: titanium powder (or titanium alloy powder) -> Screening -> Hybrid -> press forming -> Sintering -> Accessories -> titanium products.

titanium bars Production Process principles

In addition to titanium titanium, but the world has produced nearly 30 kinds of grades of titanium. The most widely used titanium alloy is Ti-6Al-4V, Ti-5Al-2.5Sn like. Our common titanium alloys and its components, as shown in Table 8-9.

Effect of heat titanium bar on β titanium organization

β stabilizing element are different degree of reduction of titanium a + β / β transformation point and sequentially tantalum, niobium, molybdenum, vanadium, silicon, copper , chromium, manganese, iron incremented.
β stabilizing element are reduced titanium martensitic transformation start temperature. β stabilizing element is gradually increased , the point M can be reduced to titanium room temperature , the β -phase titanium alloy when rapidly cooled to room temperature region can be retained to a high temperature β -phase temperature . At this point the content of titanium element is critical concentration . titanium standard part Clearly, the critical concentration is the ability of β -phase stability of a measure of alloying elements. Β -stabilizing element Ti alloy phase is based tantalum, niobium, vanadium, tungsten, copper , molybdenum , nickel, cobalt, chromium, manganese , iron in increasing order . Isomorphous β stabilizing element element is weak , the eutectoid type element is stronger .

Titanium Titanium elements on recrystallization temperatures. Except cobalt and niobium , the manganese, iron , titanium vanadium were increased recrystallization temperature.

With the increase of β stabilizing element content , when the alloy rapidly cooled from β -phase region will appear different organizational changes , β stabilizing elements will affect the decomposition of metastable β phase in the aging process , and to type "C" curve to the right goes .

Eutectoid binary β stabilizing element in the form of titanium , there are eutectoid transformation equilibrium phase at room temperature with compounds ( except for tungsten outside ) . With the lower eutectoid reaction temperature , its ability to stabilize β phase is larger, the worse the eutectoid transformation of the active compound of the more difficult the phase appeared . Iron, manganese , tittanium bar chromium and other elements in the analysis of β -phase component that has been retained to room temperature, and generally can not be eutectoid transformation occurs . But like silicon , copper, nickel and other fast -eutectoid elements are not, they are prone to change and generate eutectoid pearlite lamellar organization a + compounds.

Effects of interstitial titanium bar the microstructure and properties of heat-treated

Nitrogen, oxygen, carbon , boron, titanium have increased a + β / β phase transition temperature . Content within the predetermined range , an increase of 0.01% each of the a + β / β transformation point values ​​were increased 5.5 ℃, 2.0 ℃, 2.0 ℃ ( more than 0.15 % of the total content of 0.15 ℃), 1.0 ℃, press nitrogen, oxygen ,titanium wire carbon, boron descending order . In terms of the content of titanium and titanium alloys maximum allowable calculated ( N <0.05% , carbon < 0.10% ) , the impact on the phase transition temperature on by oxygen , nitrogen, carbon descending order . Oxygen, nitrogen, carbon , boron, titanium starts can increase the recrystallization temperature .
Oxygen and nitrogen will promote the decomposition of metastable β phase , so that "C" shaped curve to the right goes . In addition, oxygen can promote the ω phase volume percentage.

Nitrogen, oxygen , carbon, titanium have increased the tensile strength at room temperature . By its strengthening effect of nitrogen , oxygen, carbon descending order . They will have an impact on the annealed titanium iodide room temperature tensile properties . Oxygen , nitrogen exist, the highest reinforcing effect , a carbon , oxygen, while adding the weakest effect .

Nitrogen, oxygen, carbon , boron, titanium can improve the elastic modulus , the maximum impact of carbon and boron . In addition to boron addition , oxygen , nitrogen, carbon impurity elements are titanium and titanium alloys . Therefore , all the provisions of their highest levels . For titanium alloy for low temperature applications due to oxygen , nitrogen and carbon in the titanium alloy can be improved plastic - brittle transition temperature , their contents should be minimized , especially the oxygen content . "ELI" grade titanium abroad for low temperatures ,titanium pipe meaning that the gap element content is lower .

Boron as alloying elements can not only improve the elastic modulus , and can refine the grain , usually in order to trace the use of titanium alloys .

Select titanium standard annealing process

In order to select a reasonable annealing process , we first observe the effect of heating temperature and cooling method on microstructure and mechanical properties of TC4 Titanium Alloy .

Test material 920 ℃ TC4 titanium alloy hot rolled bar , hot-rolled total deformation rate of about 80%, a + β / β phase transition point of 980 ~ 990 ℃. The sample at 1000 ℃, 950 ℃, 930 ℃, 830 ℃ , respectively, air cooled heat insulation , water and furnace cooling after 1 hour . Different ways of annealing on microstructure and mechanical properties are affected .

Which greatly affect the cooling rate on microstructure and mechanical properties of the four temperature microscopy . When water-cooled , 1000 ℃, 950 ℃ and 930 ℃ in equilibrium β -phase component were to happen martensitic transformation , β phase transformation to martensite a ` needle. At 1000 ℃ showed significant Wilcoxon organization whose mechanical properties of air-cooled 1000 ℃ data fairly . And water-cooled sample at 950 ℃ and 930 ℃, when the microstructure and characteristics are similar to air-cooled , but isometric is a ` needle β + martensite phase between a newborn titanium standard parts. At this point corresponds to the highest overall performance , and better creep resistance than air cooling organization . 830 ℃ thermal equilibrium β phase when the ingredients have not touch the M line , but the water-cooled intergranular β phase also found a very small needle transformation products , can only be distinguished by electron microscopy . But the structure of the product has not yet been measured needle . At this point the tensile strength and reduction rates are low. As furnace cooling , the sample was cooled slowly , long residence time at high temperature , sufficient for the polymorphic transformation , are all a phase become coarse . After cooling the furnace 1000 ℃ , a bulky sheet and a photo β phase grain boundaries in the original β -phase formed in a well strip thickness β grains within the original network , commonly known basket -like tissue . 950 ℃, 930 ℃ and 830 ℃ after furnace cooling , as a phase tends to a phase boundary in the original raw nucleation, growth , a microstructure are isometric and intergranular β phase . Tensile strength after 1000 ℃ lower than the furnace cooling air-cooled and water-cooled , higher tensile ductility . Overall performance in the other temperature furnace cooling are also lower than those in water and air .

In summary , in order to get the best TC4 titanium alloy strength and ductility performance, while there are good creep resistance and fracture toughness , can be incubated for 1 hour at 950 ℃ after air-cooled ( or water ) in the annealing process. In order to facilitate subsequent processing, metallurgical factory when the factory , TC4 titanium alloys are used in the 700 ~ 800 ℃ for 1 hour and air cooling technology medical titanium plate. For some large forgings , to ensure uniformity of performance , sometimes used by furnace cooling process .

Chemical and physical properties of titanium plate

A4 is a Ti - Al binary alloy. Its tensile strength is slightly higher than the commercially pure titanium, do moderate-intensity range structural materials. Domestic mainly used wire. TA4 chemical composition of titanium, aluminum: 2.0 ~ 3.3, Fe 0.30, Si 0.15 C 0.10, N 0.05,surgical implant titanium 0.015 hydrogen, oxygen 0.15.

TA5 is a full a titanium alloy containing 4% aluminum and 0.005% boron. Its tensile strength than pure titanium high, but somewhat less plasticity, good weldability and corrosion resistance. The titanium alloy in the annealed state of delivery, can be used as structural materials seawater corrosion environments, has been successfully used in the shipbuilding industry. The chemical composition of titanium TA5, aluminum 3.3 to 4.3, boron 0.005, Fe 0.30 Si 0.15 C 0.10, N 0.04, 0.015 hydrogen, oxygen 0.15.

TA6 is a full a titanium alloy, containing 5% aluminum and silicon 0.015. Its high tensile strength than TA6, but the plastic than TA5 poor, good weldability and corrosion resistance. TA6 chemical composition of titanium, aluminum, 4.0 to 5.5, Fe 0.30, Si 0.15 C 0.10, N 0.05, 0.015 hydrogen, oxygen 0.15. TA6 main physical properties of titanium, density: 4.4 g / cm, a + β / β transformation point: 1000 to 1020 ° C, resistivity: 1.08 ohm mm2 / m.

TA7 is a titanium - aluminum - a whole tin ternary alloys, containing 5% aluminum and 2.5% tin. With moderate strength (80 kg / mm or so) in the annealed condition and sufficient ductility, good weldability. The material can be used as body temperatures below 500 ℃, short-term use temperature up to 900 ℃. When the titanium content is very low interstitial elements in the ultra-low temperature (-253 ℃) also has good toughness and overall performance, is an excellent ultra-low temperature titanium alloy. TA7 chemical composition of titanium: 4.0 to 5.5% aluminum, titanium standard part 2.0 to 3.0% tin, 0.3% iron, 0.15% silicon, 0.1% carbon, 0.05% nitrogen, 0.015% hydrogen, 0.2% oxygen.