Titanium is a new type of metal alloy is a single phase solid solution composed of β-phase

Titanium is a new type of metal alloy is a single phase solid solution composed of β-phase, i.e., no heat treatment has a high strength after quenching, aging the alloy has been further strengthened, the room temperature strength of up to 1372 ~ 1666 MPa; but poor thermal stability, should not be used at high temperatures.
α + β ruthenium titanium anode alloy
It is duplex alloys, has a good overall performance, good organizational stability, good toughness, ductility and high temperature deformation properties, can better thermal pressure processing, can be quenched, aging of the alloy strengthening. Strength after the heat treatment higher than the annealed state of about 50% to 100%; high temperature strength, long-term work at a temperature of 400 ℃ ~ 500 ℃, the thermal stability is inferior α titanium alloy.
The most commonly used three kinds of titanium alloy is α and α + β titanium alloy; α titanium alloy machinability best, α + β titanium followed, β titanium worst. α titanium iridium codenamed TA, β titanium codenamed TB, α + β titanium codenamed TC.
Titanium can be divided according to use heat-resistant alloys, high-strength alloys, corrosion resistant alloy (Ti - molybdenum, titanium - palladium alloys, etc.), low alloy and alloy special features. Table typical composition and performance of the alloy.

Titanium is a new type of metal, and the performance of the carbon-containing titanium impurity content of nitrogen

Titanium is a new type of metal, and the performance of the carbon-containing titanium impurity content of nitrogen, hydrogen, oxygen and so on, the most pure titanium iodide impurity content not exceeding 0.1%, but its low strength, high ductility. 99.5% of the performance of industrial pure titanium as: density ρ = 4.5g / cc, a melting point of 1725 ℃, thermal conductivity λ = 15.24W / (mK), the tensile strength σb = 539MPa, elongation δ = 25%, section shrinkage ψ = 25%, the elastic modulus E = 1.078 × 105MPa, the hardness HB195.
High strength
Density of titanium alloys is generally about 4.51g / cc,
Only 60% of steel, copper nickel hexagonal bar density was close to the density of ordinary steel, some high-strength titanium alloy over the strength of the many structural steel. Therefore, the ratio of titanium strength (strength / density) is much larger than other metal structural materials, see Table 7-1, the unit can be made out of high strength, rigidity and lightweight components. Aircraft engine components, skeleton, skin, so the use of titanium fasteners and landing gear.
High heat intensity

Titanium alloys at low and ultra-low temperature

Titanium alloys at low and ultra-low temperature, retains its mechanical properties. Low temperature performance, low interstitial elements of titanium, as TA7, at -253 ℃ still maintain a certain plasticity. Thus, low-temperature titanium alloy is also an important structural materials.
Large chemical activity
Chemical activity of titanium cap screws is large, a strong chemical reaction with atmospheric O, N, H, CO, CO2, water vapor, ammonia and the like. Carbon content greater than 0.2%, it will form a hard TiC in the titanium alloy; at higher temperatures, and also the role of N forms TiN hard surface; at above 600 ℃, the high hardness of hardened layer is formed of titanium absorbs oxygen ; hydrogen content increased, brittle layer will form. Absorbing gas produced brittle surface to a depth of 0.1 ~ 0.15 mm, the degree of hardening of 20% to 30%. Chemical affinity of titanium is also large, easy and sticking friction surface.
Small thermal elasticity
Thermal conductivity of titanium λ = 15.24W / (mK) approximately 1/4 of nickel, iron 1/5, 1/14 aluminum, while the thermal conductivity of various titanium alloys decreased by 50% than the thermal conductivity of copper nickel square bar. Elastic modulus was about 1/2 of the titanium alloy for steel, so the poor rigidity, deformation, and should not be made thin-walled elongated rod member, the machined surface when cutting a large amount of spring back, the stainless steel is about 2 to 3 times, causing severe tool flank friction, adhesion, adhesive wear.

Titanium is mainly used for the production of aircraft engine compressor components

Titanium is mainly used for the production of aircraft engine compressor components, followed by structure rockets, missiles and high-speed aircraft. The mid-1960s, titanium casting and its alloys have been in general industrial applications, electrodes for electrolysis industry production, power plant condensers, oil refining and desalination heater and environmental pollution control devices. Titanium and its alloys have become a corrosion resistant structural materials. In addition, for the production of hydrogen storage materials and shape memory alloys.
Titanium is an important new structural materials used in the aerospace industry, the proportion between the aluminum and steel, the strength and the use of temperature between, but higher than aluminum, steel strength and excellent corrosion resistance to sea water and ultra-low temperature performance. In 1950 the United States for the first time in the F-84 fighter-bombers later used as the fuselage insulation panels, wind shield, tail cover other non-load-bearing components. 1960s began using parts from titanium alloy fuselage toward the rear of the fuselage, in part, instead of structural steel bulkheads, beams, flap tracks and other important bearing components. The amount of titanium in military aircraft rapidly increased, reaching 20% to 25% by weight of the aircraft structure. Since the 1970s, civilian aircraft began extensive use of titanium alloys, such as the Boeing 747 with a capacity of 3640 kg or more of titanium. Aircraft Mach number greater than 2.5 was used in place of titanium rods to the steel, to reduce the structural weight. Again, American SR-71 high-altitude reconnaissance aircraft speed (Mach 3, altitude 26,212 meters), 93% titanium structural weight of the aircraft, known as "all-titanium" aircraft.

Commonly used methods of annealing heat treatment

Commonly used methods of annealing heat treatment, solution and aging treatment. Annealing is to eliminate stress, improve plasticity and organizational stability, in order to obtain a better overall performance. Typically α alloys and (α + β) alloy annealing temperature selected in the (α + β) ─ → β phase transition point below 120 ~ 200 ℃; solution and aging treatment is rapid cooling from high temperature zone to obtain martensite α 'phase and the metastable β phase, and then incubated in the temperature region of these metastable phase decomposition to obtain compound α phase or the dispersed second phase particles, achieve the purpose of strengthening the alloy. Typically (α + β) quenching the alloy in (α + β) ─ → β phase transition point of 40 ~ 100 ℃ were metastable β quenched alloy in the (α + β) ─ → β phase transition point above 40 ~ 80 ℃ get on. Aging treatment temperature is generally 450 ~ 550 ℃.
Summary, titanium heat exchanger alloy heat treatment process can be summarized as follows:
(1) stress relief annealing: The aim is to eliminate or reduce the residual stresses generated during machining. Prevent chemical erosion and reduce distortion in some corrosive environments.
(2) complete annealing: The purpose is to obtain good toughness, improve the processing performance, is conducive to further processing and to improve the stability of the size and organization.
(3) solution treatment and aging: The purpose is to increase its strength, α β titanium alloy and stability can not be strengthened heat treatment is carried out only in the production of annealing. α + β titanium and titanium alloys metastable β phase can contain small amounts of α by solution treatment and aging of the alloy further strengthened.
In addition, in order to meet the special requirements of the workpiece, the industry also uses double annealing, isothermal annealing, β heat treatment, deformation and heat treatment of metal heat treatment

Titanium is a new type of metal, alloy hardness greater than HB350 particularly difficult machining

Titanium is a new type of metal, alloy hardness greater than HB350 particularly difficult machining, less than HB300 is prone to stick a knife phenomenon, but also difficult to cut. However, only one aspect of the hardness of titanium machining difficult, the key is the combined effect of its machinability of chemical, physical and mechanical properties of titanium foil 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.
Cutting force (3) 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 alloy, 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.

Titanium is a new type of metal alloy in the process of cutting, the precautions are:

Titanium is a new type of metal alloy in the process of cutting, the precautions are:
(1) Due to the small elastic modulus of titanium sheet metal, the deformation of the workpiece clamped in the processing of large deformation and stress, will reduce the machining accuracy of the workpiece; workpiece clamping force installation should not be too large, increase aid support when necessary.
(2) If using liquid hydrogen cutting, the cutting process will decompose at high temperatures to release hydrogen embrittlement caused by absorption of titanium; it may cause high temperature titanium stress corrosion cracking.
(3) the use of cutting fluid chlorides are also likely to break down or volatile toxic gases, the use of security measures should be taken, otherwise it should not be used; after cutting should be timely and chlorine-free cleaning agent thoroughly cleaned parts, remove residual chlorine thereof.
(4) prohibits the use of lead or zinc-based alloy production workers, fixture and titanium contact, copper, tin, cadmium and its alloys are also prohibited.
(5) All workers, fixtures or other devices must be in contact with the titanium clean; titanium parts cleaned off, to prevent contamination of grease or fingerprints, or after the salt may cause stress corrosion.
(6) In general when machining titanium fasteners, no ignition hazard only when micro-cutting, small chips have cut ignition combustion phenomenon. To avoid fires, in addition to a large number of pouring coolant should prevent chips piled on the machine tool to be replaced immediately with a blunt or reduce cutting speed, feed rate increased to increase the chip thickness. If once the fire should be used talc, limestone powder, dry sand, fire fighting equipment were extinguished, prohibited the use of carbon tetrachloride, carbon dioxide fire extinguisher, nor watering, because water can accelerate the burning, and even lead to a hydrogen explosion.