The thermal neutron absorption cross section of titanium is 56×10-28m2, which is about 30 times that of zirconium and 1/2 of that of hafnium. The nuclear properties of titanium alloys are also relatively stable. Under the irradiation of 3~20×10-19 slow neutron currents, the Brinell hardness and yield strength increase slightly, and the elongation and resistivity decrease slightly, but the impact toughness does not change. The density of the product and the size and shape of the product have not changed. This stable nuclear performance and other excellent properties enable Ti31 alloy to be used in high temperature and high pressure, normal temperature and normal pressure parts in nuclear power plants.
Ti31 alloy is a new type of Ti-Al-Zr-Mo-Ni titanium alloy designed and developed by the Northwest Nonferrous Metal Research Institute during the "Seventh Five-Year Plan" and "Eighth Five-Year Plan" period. Applied research on alloys. The alloy concentrates the advantages of a variety of titanium alloys. Compared with other titanium alloys of the same strength, it has high plasticity and toughness, medium temperature thermal strength, high temperature durability, good corrosion resistance and weldability; conventional Forging, extrusion, rolling, cold forming and other methods are processed into various products such as plates, bars, forgings, tubes and cakes. The alloy can be used in a high temperature environment of 300 ℃ ~ 400 ℃.
The properties of Ti31 alloy are shown in Table 1. The typical mechanical properties of alloy plates, forgings and pipes are: Rm>590 MPa, Rp0.2>490 MPa, A>16%, Z>35%, ak≥59 J/cm2. The strength of Ti31 is about 1.5 times that of pure titanium, but the process plasticity is equivalent to that of pure titanium, and it has good bending, flattening and flaring properties. Using 2d (d: pipe diameter) and 2 t (t: pipe wall thickness) bending cores, the pipe and sheet can be bent up to 180°; with a 60° taper head, the pipe flare is greater than 50%; the minimum flattening plate spacing can be No cracks appear up to 4.5 t. The alloy does not undergo cyclic softening under repeated plastic strain. Excellent seawater corrosion resistance: the corrosion rate of full immersion in natural seawater in Yulin Port is 0 mm/a, and there is no crevice corrosion in natural seawater medium below 180±5 °C, and the corrosion rate of dynamic seawater corrosion (flow rate is 3 m/s) is 0 mm/a, and the galvanic corrosion effect with the hull steel is 1.25. Good welding performance, welding joint Rm>590 MPa, ak≥58.8 J/cm2, welding coefficient greater than 0.9. The applied products include plates, rods, cakes and pipes and machined parts with various functions, such as flanges, reducing tee pipes, pipe bases, etc. The alloy is used to manufacture various heat exchangers, pipelines, pump bodies, valves, etc., and has been successfully applied. After the "Ninth Five-Year Plan", the industrial production of the alloy was carried out. Ti31 alloy has been successfully used in the waste heat discharge cooler. It is the first all-titanium alloy welded structure tubular heat exchanger in my country, and it is the main equipment of the primary circuit waste heat discharge system.
