Titanium tube is of light weight, high strength and excellent mechanical performance. It is widely used in heat exchange equipment, such as tube heat exchanger, coil heat exchanger, coil heat exchanger, condenser, evaporator and pipeline. Many nuclear power industries use titanium tubes as standard tubes for their units.

 

The technical requirements

 

1. The chemical composition of titanium and titanium alloy tubes shall conform to the requirements of GB/T3620.1, and the allowable deviation of the chemical composition of Ming kun industry shall conform to the provisions of GB/T3620.2 when required.

 

2. Allowable deviation of pipe diameter shall be in accordance with the table 1.

 

3. The allowable deviation of the pipe wall thickness shall not exceed 12.5% of the nominal wall thickness, and the allowable deviation of the pipe wall thickness shall not apply to the welding seam of the titanium welded pipe.

 

4. The length of pipe shall be in accordance with table 2.

 

Length of the pipe or times ruler length should be within the scope of the variable scale length, scale length of the allowable deviation of + 10 mm, double foot length should also be included in the pipe when cutting amount of incision, each incision quantity should be 5 mm.

 

Titanium alloy is a alloy of other elements based on titanium. Titanium has two homogenous different crystal: under 882 ℃ to close the six-party alpha titanium structure, above 882 ℃ for body centered cubic beta titanium.

 

The effects of alloy elements on the phase transition temperature can be divided into three categories:

 

The elements that stabilize alpha phase and improve phase transition temperature are alpha stable elements, including aluminum, carbon, oxygen and nitrogen. Aluminum is the main alloy element of titanium alloy. It has obvious effect on improving the normal temperature and high temperature strength, reducing the proportion and increasing the elastic modulus.

 

The elements that stabilize beta phase and decrease phase change temperature are beta stable elements, and can be divided into two types: crystal type and eutectic type. The former has molybdenum, niobium, vanadium, etc. The latter has chromium, manganese, copper, iron, silicon and so on.

 

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

 

Oxygen, nitrogen, carbon and hydrogen are the main impurities of titanium. The oxygen and nitrogen have a great solubility in the alpha phase, which has a significant effect on the titanium alloy, but the plasticity decreases. The content of oxygen and nitrogen in titanium is usually set at 0.15 ~ 0.2% and 0.04 ~ 0.05% respectively. Hydrogen is very small in the alpha phase, and the dissolved hydrogen in the titanium alloy produces hydrogen compounds that make the alloy brittle. The hydrogen content in titanium alloys is usually controlled below 0.015%. The dissolution of hydrogen in titanium is reversible and can be removed by vacuum annealing

 

Titanium alloys have high strength and low density, good mechanical properties, good toughness and corrosion resistance. In addition, the process performance of titanium alloy is poor, cutting processing is difficult, and in hot processing, it is very easy to absorb impurities such as hydrogen and oxygen nitrogen. There is also the resistance to wear, the production process is complex. The industrial production of titanium began in 1948. The need for aviation industry development has enabled the titanium industry to grow at an average annual rate of about 8 per cent. At present, the annual production of titanium alloy in the world has reached 40,000 tons and nearly 30 kinds of titanium alloy plate number. The most widely used titanium alloys are ti-6al-4v (TC4), ti-5al-2.5 Sn (TA7) and industrial pure titanium (TA1, TA2 and TA3).