Titanium plate manufacturing process and characteristics

TC4 titanium alloy has good mechanical properties at room temperature and high temperature, and is widely used in the manufacture of aviation structural parts and aero-engine fans, drums, etc., and has accounted for more than 50% of the total aviation titanium alloys. Many load-bearing structural parts of aircraft, especially variable cross-section structural parts, require the raw material bars to have good notched stress fracture performance. The purpose is to ensure that the parts have a strong ability to inhibit the initiation and propagation of cracks in a state of high-stress concentration. Without breaking and failing. The upper limit of the specifications of this type of TC4 titanium alloy bar in the relevant domestic technical standards is Ф220mm. At present, there are no public reports on the preparation process of TC4 titanium alloy bars requiring notched stress fracture performance at home and abroad. It is generally believed that the high hydrogen content or poor uniformity of the TC4 titanium alloy will reduce its room temperature notch stress fracture performance.

In industrialized mass production, it is also common that the notch stress fracture performance of such bars is unqualified due to improper process. The raw material procurement contract of a special forging requires the provision of ~b350mmTC4 titanium alloy bars in the range of beyond specifications in accordance with current technical standards. Under the premise of ensuring the same mechanical properties, the ultrasonic flaw detection level is required to be changed from GB/T5193 of the original smaller specifications of bars. The grade B in the medium is raised to grade A, so the relevant process research on the preparation of large-size TC4 titanium alloy bars with special needs has been carried out.

Titanium rod manufacturers use sponge titanium and master alloys to prepare 5t consumable electrodes. The 6720mm TC4 titanium alloy ingots are obtained through 3 times vacuum waste smelting through the ALD vacuum waste electric arc furnace imported from Germany. Because the microscopic concentration of hydrogen under high stress reduces the notch stress fracture performance J, certain measures have been taken to control the hydrogen content of the ingot in the experiment on the raw material selection and smelting process of the ingot. Samples are taken from the surface of the head, middle and tail of the ingot to test its chemical composition.

(1) By adopting the forging process of phase zone blanking and two-phase zone upsetting + straight drawing, it is possible to prepare Φ350mm large-size TC4 titanium alloy bars whose structure, performance and flaw detection level meet the technical requirements of the supply.

(2) The structure with good primary equiaxialization is beneficial to improve the notch stress fracture performance at room temperature, and the short rod-like α-phase structure with strong direction consistency will reduce the notch stress fracture performance.
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