Where is the application range of titanium standard parts?

With the further development of the aerospace industry and the continuous exploration of the deep space field, the performance requirements of cryogenic materials for spacecraft structural parts have further increased.

On the one hand, the spacecraft structural materials must have sufficient strength and toughness and excellent thermal properties at low temperatures; on the other hand, considering the complexity of the shape of the spacecraft structural parts, the materials must have good machinability.

Compared with traditional low temperature materials, titanium alloy has a higher yield strength at low temperatures, which is more than 3 times that of stainless steel, and its density is only 1/4 to 1/2 of that of stainless steel. In addition, titanium alloy also has a series of advantages such as low thermal conductivity, small expansion coefficient, and non-magnetic, so it is very suitable as a new low-temperature material in the aerospace field.

At present, low-temperature titanium alloys have been initially used in the field of liquid rocket engines, mainly as structural materials such as hydrogen-oxygen engine hydrogen storage tanks, hydrogen pump impellers, etc., greatly improving the thrust-to-weight ratio, working life and reliability of liquid rocket engines. The problem with the application of low-temperature titanium alloys is that the elongation and fracture toughness of titanium alloys are greatly reduced in low-temperature environments, and they show obvious low-temperature brittleness. Therefore, how to reduce the low-temperature brittleness of titanium alloys and improve the toughness and plasticity of titanium alloys under low-temperature conditions becomes low Titanium alloy research is the top priority.

Scholars at home and abroad have conducted a lot of research to solve this problem, and found that two methods of reducing the content of interstitial elements such as C, H, O and reducing the content of aluminum element can effectively improve the low-temperature performance of titanium alloys. Through these two methods, a series of new low-temperature titanium alloys with excellent properties have been developed at home and abroad.

The former Soviet Union was committed to the development and application of low-temperature titanium alloys. By reducing the content of aluminum, the former Soviet Union has developed a series of low-aluminum low-temperature titanium alloys, of which OT4 and BT5-1 are widely used. OT4 alloy has been used in spacecraft orbital docking parts, liquid rocket pipes and combustion chamber structural parts; BT5-1 alloy has been used in the manufacture of liquid hydrogen containers. In order to further improve the impulse driving ratio of liquid rocket engines, a Russian research institute conducted research and development of high-strength, high-plasticity, low-temperature titanium alloys suitable for extremely low temperature environments at -253 ℃.

The research on low-temperature titanium alloys in the United States has mainly focused on the α-type titanium alloy TA7 ELI (Extra low interstitial) and the α+β-type titanium alloy TC4 ELI. By reducing the content of interstitial elements, the strength and toughness of the two titanium alloys at extremely low temperatures have been significantly improved. TA7 ELI, as a near-α-type titanium alloy, still has good toughness, low thermal conductivity and notch sensitivity at low temperatures of 20 K. It has been successfully used in cryogenic vessels, cryogenic pipelines, and liquid rocket engine impellers. structure. In the Apollo project, TC4 ELI has been widely used as the main material of liquid hydrogen containers and liquid hydrogen pipes and has achieved good results. In addition, American scholars have also carried out basic research on a series of problems such as the fracture mechanism of low-temperature titanium alloys and hydrogen embrittlement, and obtained the mechanical properties and fracture mechanism data of various low-temperature titanium alloys such as TA7 ELI and TC4 ELI. The further development and application of titanium alloy laid the foundation.
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