Titanium cutting force per unit area on the big: the main cutting force of about 20% smaller than when cutting steel, due to the length of the chip and the rake face contact is extremely short, the contact area on the cutting forces unit greatly increased, likely to cause chipping. Meanwhile, due to the small elastic modulus of the titanium plates, the processing in the radial force prone to bending deformation, causing vibration, increased tool wear and affects the accuracy of parts. Therefore, the required process system should have good rigidity.
(4) Chilled serious: Because the chemical activity of titanium is large, at high cutting temperature, is easy to absorb oxygen in the air and nitrogen to form a hard and brittle skin; while plastic deformation during the cutting process can also cause surface hardening . Chilled phenomenon will not only reduce the fatigue strength of the parts, but also increased tool wear, is a very important feature when cutting titanium.
HB350 hardness greater than titanium machining particularly difficult, less than HB300 is prone to stick a knife phenomenon, but also difficult to cut. However, only one aspect of the hardness of titanium sheet metal, the key is the combined effect of its machinability of chemical, physical and mechanical properties of titanium itself between. Cutting Titanium has the following characteristics:
(1) deformation coefficient is small: This is a significant feature of titanium machining, deformation coefficient is less than or close to one. Chip away the knife sliding friction surface greatly increases the previous accelerated tool wear.
(2) high cutting temperatures: As low thermal conductivity of titanium alloy (equivalent to only 1/5 ~ 1/7 45 steel), the contact length of the chip and the rake is very short, the heat generated when cutting difficult to pass out, concentrated in a smaller range of the cutting area and near the cutting edge, high cutting temperatures. Under the same cutting conditions, the cutting temperature higher than 45 steel cutting more than doubled.
Advanced technology and methods of powder metallurgy as a modern metallurgy and materials processing in the titanium metal supply industry has played an important role. Titanium powder metallurgy nearly molding technology, direct preparation of finished or nearly finished size of components, reducing the consumption of raw materials, shorten the processing cycle, cost savings of 20% to 50% compared with conventional processes. In the automotive industry, titanium powder metallurgy particular attention in recent molding technology in Japan, powder metallurgy parts are widely used in automobile engines and transmissions, which, connecting rods, valve seats, valve, the pulley, the synchronizer hub, synchronizing rings so are complex and demanding critical parts. Zhu titanium powder metallurgy current research is in the stage of rapid development, including a child, first, high-quality low-cost titanium powders were prepared by technology and its industrialization; the second is the preparation of titanium powder metallurgy technology even while in the automotive industry promotion applications.
One reason for the high price of titanium alloying elements is higher prices.
With the progress of titanium smelting technology, the rear titanium wire production process generated Scrap, scrap and other salvage treatment after the series as the charge added to achieve the production cycle, is an effective way to reduce the cost of raw materials. Practice shows that for every 1% of residual use of titanium, titanium ingot can reduce production costs by 0.8%. If the electron beam cooling bed furnace, plasma beam cooling bed furnace smelting, can not only improve the quality of titanium ingot metallurgy, while extensive use of recycled scrap, ingot reduce costs.
Reduce processing costs
More than 60% of the total cost of processing costs for countries to reduce the cost of key research. Titanium components in the production process of the production process is not only complex, but generated a lot of residual titanium in the production process, and a longer production cycle, resulting in parts production costs. Hinders its broader application.
Casting is a classic (nearly) net molding process. Production of parts without machining or machining rarely, thus saving a lot of metal. Casting can often produce a complex shape parts, and these parts are made of other conventional process for the manufacture of complex, high production costs, especially for the relatively high price of materials titanium. Currently, a large number of applications in the aerospace industry titanium castings. In the automotive industry, the production of parts by casting method has a valve, turbo pressure, etc. zo.
Titanium is an important structural metal in the 1950s developed, titanium because of its high strength, corrosion resistance, and high heat resistance and are widely used in various fields. Many countries recognize the importance of titanium metal materials, have their research and development, and has been applied.
Titanium is the first practical American successfully developed in 1954, because of its heat resistance, strength, ductility, toughness, formability, weldability, corrosion resistance and biocompatibility are good, and become titanium ace alloy alloy industry, which accounts for the use of an alloy of 75% to 85% of all titanium alloys. Many others can be seen as a modification of titanium alloy Ti-6Al-4V alloy.
1950s and 1960s, mainly in the developing high temperature titanium and titanium alloy airframe aviation engine, the 1970s developed a number of corrosion resistant alloys, since the 1980s, corrosion resistant and high-strength titanium alloy has been further development of. Temperature resistant titanium alloys 400 ℃ from the 1950s up to the 1990s 600 ~ 650 ℃.
Appears based alloy, the titanium being propelled by the cold end to the hot end of the engine in the direction of the engine using the engine parts. Titanium alloy development to high-strength, high plastic, high strength and high toughness, high modulus and high damage tolerance direction.
In addition, since the 1970s, there was memory alloys, and get increasingly widely used in engineering.
Titanium alloy is a titanium-based alloy by adding other elements. There are two isomeric titanium crystal:
Below 882 ℃ for α hcp titanium bars for sale, more than 882 ℃ for the body-centered cubic β titanium.
Alloying elements according to their impact on the phase transition temperature can be divided into three categories:
① stable α phase, increase the phase transition temperature of the elements of α stabilizing element, aluminum, carbon, oxygen and nitrogen. Which is the main alloying elements aluminum alloy, improve its normal and high temperature strength of the alloy, reduce the proportion of the elastic modulus increases obviously.
② stable β-phase, reducing the element of the phase transition temperature of β stabilizing element, and can be divided isomorphic and eutectoid two. The former has molybdenum, niobium, vanadium and the like; the latter are chromium, manganese, copper, iron, silicon and the like.
③ small element of the phase transition temperature is neutral elements, zirconium and tin. Oxygen, nitrogen, carbon and hydrogen are the major impurity titanium. Oxygen and nitrogen in the α phase has a greater solubility of titanium significant strengthening effect, but the plastic drop. Typically a predetermined content of oxygen and nitrogen in titanium 0.15 to 0.2% and 0.04% to 0.05% or less, respectively. The solubility of hydrogen in α phase is very small, titanium dissolved in excess hydride hydrogen will produce the alloy brittle. Titanium is usually hydrogen content control 0.015%. Hydrogen was dissolved in titanium is reversible, can be removed by vacuum annealing.
Titanium is allotrope, melting point 1668 ℃, showed a close-packed hexagonal lattice structure, called α titanium at temperatures below 882 ℃; body-centered cubic lattice structure at above 882 ℃ was called β titanium. The use of the different characteristics of the two titanium structures, adding appropriate alloying elements, so that the phase transition temperature and relative content of different tissues obtained by gradually changing the titanium (titanium alloys). At room temperature, there are three titanium matrix organization, titanium will be divided into the following three categories: α alloy, (α + β) alloys and β alloys.
α titanium
It is a single phase alloy consisting of α-phase solid solution, either at ambient temperatures or at higher temperatures the practical application, are the α phase, organizational stability, wear resistance higher than that of pure titanium, high resistance to oxidation. At a temperature of 500 ℃ ~ 600 ℃, and maintains its strength and creep resistance, but can not be heat strengthened, not high temperature strength.
β titanium screws
It is a single-phase alloy consisting of β-phase solid solution, that is not heat-treated after having a high strength, hardening, aging alloy has been further strengthened, the room temperature strength of up to 1372 ~ 1666 MPa; but poor thermal stability, and should not be used at high temperatures .
