Standard and technical requirements for titanium pipe
Titanium tube has the advantages of 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 pipe 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
I. referenced standards
1. GB 228 metal tensile test method
2. GB 224 metal pipe hydraulic test method
3. GB 226 metal tube flattening test method
4. GB / t3620.1 grades and chemical composition of titanium and titanium alloys
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 the provisions of GB / t3620.1. During the re inspection by the demander, the allowable deviation of chemical composition of Mingkun titanium industry shall comply with the provisions 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 its variable length range, 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 an obvious effect on improving the strength at room and high temperature, reducing the specific gravity and increasing the elastic modulus.
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 specified 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.