Titanium tube has light weight, high strength and superior mechanical properties. It is widely used in heat exchange equipment, such as tubular heat exchanger, coil heat exchanger, coil heat exchanger, condenser, evaporator and transmission pipeline. Many nuclear power industries take titanium tubes as the standard tubes for their units.

Titanium pipes shall comply with two national standards: GB / t3624-2010, GB / t3625-2007, ASTM b337 338 according to different use requirements and properties

Supply brand: TA0, TA1, TA2, ta9, TA10, bt1-00, bt1-0, GR1, Gr2

Production standard

I. referenced standards

1. GB 228 metal tensile test method

2. GB 224 metal pipe hydraulic test method

3. GB 226 flattening test method of metal pipe

4. GB/T3620. 1 titanium and titanium alloy brand and chemical composition

5. GB/T3620. 2. Chemical composition and allowable deviation of titanium and titanium alloy processing products

II. Technical requirements

1. The chemical composition of titanium and titanium alloy pipes shall comply with GB / t3620 1, the allowable deviation of chemical composition of Mingkun titanium industry meets the requirements of GB / t3620 2.

2. The allowable deviation of pipe outer diameter shall comply with the provisions in table I.

3. The allowable deviation of pipe wall thickness shall not exceed ± 12.5% of its nominal wall thickness. The allowable deviation of pipe wall thickness is not applicable to the weld of titanium welded pipe.

4. The length of pipes shall comply with the provisions in Table 2.

5. The fixed length or double length of the pipe shall be within the range of its variable length, and the allowable deviation of the fixed length shall be + 10mm. The double length shall also be included in the cut amount when the pipe is cut, and each cut amount shall be 5mm.

Titanium alloy is an alloy composed of titanium and other elements. Titanium has two kinds of homogeneous and heterogeneous crystals: close packed hexagonal structure below 882 ℃ α Titanium, body centered cubic above 882 ℃ β Titanium.

Alloy elements can be divided into three categories according to their influence on phase transformation temperature:

① Steady α The elements that increase the phase transition temperature are α Stable elements include aluminum, carbon, oxygen and nitrogen. Aluminum is the main alloying element of titanium alloy. It has obvious effect on improving the strength at room temperature and high temperature, reducing the specific gravity and increasing the elastic modulus of the alloy.

② Steady β The elements that reduce the phase transition temperature are β Stable elements can be divided into isomorphic and eutectoid types. Products with titanium alloy.

The former includes molybdenum, niobium, vanadium, etc; The latter includes chromium, manganese, copper, iron, silicon, etc.

③ The elements that have little effect on the phase transition temperature are neutral elements, such as zirconium, tin and so on.

Oxygen, nitrogen, carbon and hydrogen are the main impurities in titanium alloys. Oxygen and nitrogen in α It has a large solubility in the phase, which has a significant strengthening effect on titanium alloy, but reduces the plasticity. It is generally stipulated that the contents of oxygen and nitrogen in titanium are less than 0.15 ~ 0.2% and 0.04 ~ 0.05% respectively. Hydrogen in α The solubility in the phase is very small. Too much hydrogen dissolved in titanium alloy will produce hydride and make the alloy brittle. Generally, the hydrogen content in titanium alloy is controlled below 0.015%. The dissolution of hydrogen in titanium is reversible and can be removed by vacuum annealing.

Titanium alloy element

Titanium alloy is an alloy based on titanium and added with other elements. Titanium has two kinds of homogeneous and heterogeneous crystals: close packed hexagonal structure below 882 ℃ α Titanium, body centered cubic above 882 ℃ β Titanium. Alloy elements can be divided into three categories according to their influence on phase transformation temperature: ① stable α The elements that increase the phase transition temperature are α Stable elements include aluminum, carbon, oxygen and nitrogen. Aluminum is the main alloying element of titanium alloy. It has obvious effect on improving the strength at room temperature and high temperature, reducing the specific gravity and increasing the elastic modulus of the alloy. ② Steady β The elements that reduce the phase transition temperature are β Stable elements can be divided into isomorphic and eutectoid types. The former includes molybdenum, niobium, vanadium, etc; The latter includes chromium, manganese, copper, iron, silicon, etc. ③ The elements that have little effect on the phase transition temperature are neutral elements, such as zirconium, tin and so on.

Oxygen, nitrogen, carbon and hydrogen are the main impurities in titanium alloys. Oxygen and nitrogen in α It has a large solubility in the phase, which has a significant strengthening effect on titanium alloy, but reduces the plasticity. The oxygen content is usually less than 2.0 ~ 0.05% and 0.04% of titanium, respectively. Hydrogen in α The solubility in the phase is very small. Too much hydrogen dissolved in titanium alloy will produce hydride and make the alloy brittle. Generally, the hydrogen content in titanium alloy is controlled below 0.015%. The dissolution of hydrogen in titanium is reversible and can be removed by vacuum annealing.

classification

Titanium is an isomer with a melting point of 1720 ℃ and a close packed hexagonal lattice structure below 882 ℃ α Titanium; It has a body centered cubic structure above 882 ℃, which is called β Titanium. Using the different characteristics of the above two structures of titanium, adding appropriate alloy elements to gradually change its phase transformation temperature and phase content to obtain titanium alloys with different structures. At room temperature, titanium alloys have three kinds of matrix structures, and titanium alloys are divided into the following three categories: α Alloy（ α+β) Alloy and β Alloy. China is represented by TA, TC and TB respectively.

α titanium alloy

It is α The single-phase alloy composed of solid solution, whether at general temperature or at higher practical application temperature, is α Phase, stable structure, higher wear resistance than pure titanium and strong oxidation resistance. At the temperature of 500 ℃ ~ 600 ℃, it still maintains its strength and creep resistance, but it cannot be strengthened by heat treatment, and the strength at room temperature is not high.

β titanium alloy

It is β The single-phase alloy composed of phase solid solution has high strength without heat treatment. After quenching and aging, the alloy is further strengthened, and the strength at room temperature can reach 1372 ~ 1666mpa; However, the thermal stability is poor and should not be used at high temperature.

α+β titanium alloy

It is a two-phase alloy with good comprehensive properties, good structural stability, good toughness, plasticity and high-temperature deformation properties. It can better carry out hot pressure processing, quenching and aging to strengthen the alloy. The strength after heat treatment is about 50% ~ 100% higher than that in annealing state; High temperature strength, can work at 400 ℃ ~ 500 ℃ for a long time, and its thermal stability is inferior to α Titanium alloy.

The most commonly used of the three titanium alloys is α Titanium alloy and α+β Titanium alloy; α Titanium alloy has the best machinability, α+β Titanium alloy takes the second place, β Titanium alloy is the worst. α Titanium alloy code is Ta, β Titanium alloy code TB, α+β Titanium alloy code is TC.

Titanium alloys can be divided into heat-resistant alloys, high-strength alloys, corrosion-resistant alloys (titanium molybdenum, titanium palladium alloys, etc.), low-temperature alloys and special functional alloys (titanium iron hydrogen storage materials and titanium nickel memory alloys). The composition and properties of typical alloys are shown in the table.

Different phase compositions and microstructures of heat treated titanium alloys can be obtained by adjusting the heat treatment process. It is generally believed that fine equiaxed structure has good plasticity, thermal stability and fatigue strength; Acicular structure has high rupture strength, creep strength and fracture toughness; Equiaxed and acicular mixed structures have good comprehensive properties.

purpose

Titanium alloy has high strength, low density, good mechanical properties, good toughness and corrosion resistance. In addition, titanium alloy has poor process performance and difficult machining. In hot machining, it is very easy to absorb impurities such as hydrogen, oxygen, nitrogen and carbon. There is also poor wear resistance and complex production process. The industrial production of titanium began in 1948. The needs of the development of aviation industry make the titanium industry develop at an average annual growth rate of about 8%. At present, the annual output of titanium alloy processing materials in the world has reached more than 40000 tons, and there are nearly 30 titanium alloy brands. The most widely used titanium alloys are Ti-6Al-4V (TC4), ti-5al-2.5sn (TA7) and industrial pure titanium (TA1, TA2 and TA3).

Titanium alloy is mainly used to make compressor parts of aircraft engine, followed by structural parts of rocket, missile and high-speed aircraft. In the mid-1960s, titanium and its alloys have been applied in general industry, such as making electrodes in electrolytic industry, condensers in power stations, heaters for oil refining and seawater desalination, and environmental pollution control devices. Titanium and its alloys have become a kind of corrosion resistant structural materials. In addition, it is also used to produce hydrogen storage materials and shape memory alloys.

China began research on titanium and titanium alloys in 1956; In the mid-1960s, the industrial production of titanium materials began and TB2 alloy was developed.

Titanium alloy is a new important structural material used in aerospace industry. Its specific gravity, strength and service temperature are between aluminum and steel, but it has high specific strength and excellent seawater corrosion resistance and ultra-low temperature performance. In 1950, the United States first used F-84 fighter bomber as non load-bearing components such as rear fuselage heat shield, wind guide cover and tail cover. Since the 1960s, the use of titanium alloy has moved from the rear fuselage to the middle fuselage, partially replacing structural steel to manufacture important load-bearing components such as spacer frame, beam, flap slide rail and so on. The use of titanium alloy in military aircraft has increased rapidly, reaching 20% ~ 25% of the weight of aircraft structure. Since the 1970s, a large number of titanium alloys have been used in civil aircraft. For example, the amount of titanium used in Boeing 747 aircraft has reached more than 3640 kg. Titanium for aircraft with Mach number less than 2.5 is mainly used to replace steel to reduce structural weight. Another example is the US SR-71 high-altitude high-speed reconnaissance aircraft (flying Mach number is 3 and flying altitude is 26212 meters). Titanium accounts for 93% of the structural weight of the aircraft and is known as the "all titanium" aircraft. When the thrust weight ratio of aeroengine is increased from 4 ~ 6 to 8 ~ 10, and the outlet temperature of compressor is correspondingly increased from 200 ~ 300 ° C to 500 ~ 600 ° C, the low-pressure compressor disk and blade originally made of aluminum must be made of titanium alloy, or titanium alloy must be used to replace stainless steel to make high-pressure compressor disk and blade, so as to reduce the structural weight. In the 1970s, the amount of titanium alloy used in aeroengines generally accounted for 20% ~ 30% of the total weight of the structure. It was mainly used to manufacture compressor components, such as forged titanium fan, compressor disk and blade, cast titanium compressor casing, intermediate casing, bearing shell, etc. Spacecraft mainly use the high specific strength, corrosion resistance and low temperature resistance of titanium alloy to manufacture various pressure vessels, fuel tanks, fasteners, instrument straps, frames and rocket shells. Titanium alloy plate weldments are also used in artificial earth satellites, lunar modules, manned spacecraft and space shuttles.