Titanium alloy has a small density, high specific strength, high temperature resistance, corrosion resistance, non-magnetic, sound transmission, shock vibration resistance and other good comprehensive performance, for titanium alloy in various fields opens up a wide range of application prospects. In recent years, titanium alloy wire is increasingly used in chemical machinery, ships, automobiles, oil and gas, food, medical equipment and other fields. Different industries on the mechanical properties of titanium alloy wire (hardness, elongation, tensile strength, etc.) requirements are not the same, the author study of titanium alloy wire production process on its hardness and tensile strength of the impact of titanium alloy wire, the purpose is to produce qualified titanium alloy wire to formulate a suitable production process.
The test was carried out using ø6.50 mm TC4 (Ti-6Al-4V) titanium alloy coil, and the chemical composition of TC4 titanium alloy coil was in accordance with the provisions of GB/T 3620.1-2007.
The main equipment used for the test are: 1/700 wire drawing machine, HV1000 hardness tester, WDL-10 microcomputer-controlled universal testing machine.
Titanium alloy wire drawing process: unwinding → heating → drawing → closing. Will ø6.50 mm drawing to ø2.70 mm, in the same wire drawing machine for 13 passes and 9 passes drawing, 13 passes drawing process: ø6.50-6.10-5.70-5.40-5.10 -4.80-4.50-4.20-3.90-3.60-3.30-3.10 -2.90-2.70 mm, 9 drawing passes: ø6.50-6.10-5.70-5.20-4.70 -4.20-3.80-3.40-3.00-2.70 mm, ensure that the heating process parameters remain unchanged during the drawing process, and then sample each specification of titanium alloy wire drawn by the two processes, respectively. The hardness and tensile strength of the titanium alloy wire were tested.
As can be seen from Tables 1 and 2, the hardness of the 13-pass and 9-pass drawn titanium alloy wires is in the range of 317-344 HV, and the tensile strength is in the range of 1,066-1,091 MPa, which does not follow the empirical formula of Tulinkov.
The difference between the highest hardness and the lowest hardness of titanium was 24 HV when 13 passes were used for drawing, and the difference between the highest hardness and the lowest hardness of titanium alloy wire was 27 HV when 9 passes were used for drawing, whereas there was little difference in the hardness of the ø2.70 mm alloy wire under the 2 drawing processes; the difference between the highest tensile strength and the lowest tensile strength of titanium alloy wire was 25 MPa when 13 passes were used, and the difference between the highest tensile strength and the lowest tensile strength of titanium alloy wire was 23 MPa when 9 passes were used for drawing, whereas there was little difference in the tensile strength under the 2 drawing processes. The difference between the highest tensile strength and the lowest tensile strength of the titanium alloy wire is 23 MPa when using 13 drawing passes, and the difference between the tensile strengths of the titanium alloy wire and the lowest tensile strength when using 9 drawing passes is not significant under the two drawing processes.
The small difference in hardness and tensile strength between the 1st pass and the finished titanium alloy wire is the result of grain refinement during production. After several tests with different passes, the results do not differ much. Different drawing passes have little effect on the hardness and tensile strength of ø2.70 mm titanium alloy wire.
In the high-quality carbon structural steel wire drawing, part of the compression rate increases will make the wire tensile strength increases, toughness decreases.
As seen from the titanium alloy wire production process, due to the titanium alloy wire in the drawing, work hardening speed, cold drawing is difficult, in order to achieve smooth drawing, titanium alloy needs to be drawn in a heated state, which is equivalent to the titanium alloy wire annealing treatment. Annealing is to eliminate internal stress, improve plasticity, in order to obtain a better overall performance. Usually TC4 titanium alloy annealing temperature is selected in (α + β) -→ β phase transition point below 120 ~ 200 ℃. After heating, the last sub-drawing produced in the work hardening is completely or partially eliminated, the raw material organisation can be stabilized and maintained, which is the reason why the hardness and tensile strength of titanium alloy wire is not affected by the production process, so it can not be used to improve the strength and toughness of high-quality carbon structural steel wires in order to improve the tensile strength and hardness of titanium alloy wire.
Due to the fast hardening of titanium alloy wire cold drawing, in order to achieve smooth drawing, each drawing a specification, need to be in the recrystallisation temperature, while heating and drawing, which makes each drawing, the hardness and tensile strength of the finished titanium alloy wire is not affected by the drawing process, so the production of hardness and tensile strength of the titanium alloy wire with special requirements, need to go to explore other processes to solve.
