Industrial Gr1 titanium rods have excellent corrosion resistance, good mechanical properties and welding properties. They can be used as important corrosion-resistant structural materials and are widely used in chemical equipment, coastal power generation equipment, seawater desalination devices, and ship parts. One of the titanium materials. Cold rolling can obtain pure titanium sheet and strip with good surface quality and small thickness tolerance, but because industrial pure titanium is a close-packed hexagonal metal with less slip system and poor symmetry, after cold deformation of titanium, its The lattice is distorted, and the internal lattice produces a large number of defects and dislocations, which increases the internal energy of the titanium material, and the titanium material is in a metastable state. Through the annealing treatment, the internal stress of the cold-rolled titanium plate can be eliminated, the undistorted grain structure can be obtained, and the properties of the titanium plate can be improved.
At present, it mainly focuses on the influence of the annealing process on the microstructure and properties of a certain specification of titanium or titanium alloy. However, in the actual production process, when the same annealing process is used to treat cold-rolled titanium sheets of different specifications, the microstructure and properties of the products are quite different, and even some Can not meet user requirements. Therefore, researchers annealed cold-rolled titanium sheets of different specifications and compared the microstructure and properties of cold-rolled titanium sheets at different annealing temperatures.
The experimental materials are 3.5mm hot-rolled pure titanium coils that are cold-rolled into GR1 pure titanium cold-rolled coils with a thickness of 0.5mm and 1.0mm, respectively. The samples are cut from the coils and processed into several mechanical tensile standard samples. . Before heat treatment, the sample was in a chilled state without yielding, the elongation after fracture was only 6%, and the structure was a streamlined fiber structure. The grain boundaries can be seen, because the deformation of the 1.0mm titanium plate is not as large as that of the 0.5mm cold-rolled titanium plate, and the original grain structure is not sufficiently broken during the cold rolling process.
Use a box-type resistance furnace to heat the sample, heat up with the furnace to each set temperature (550, 570, 590, 610, 630, 650, 670, 690, 710 ℃), hold for 1 hour, and then cool down to below 100 ℃ with the furnace, and then release the furnace. cool down. After the annealing treatment, the mechanical properties of the samples were tested, the corrosion structure of the samples was intercepted, and the grain size was rated. The results showed that:
(1) After heat treatment of 0.5mm cold-rolled titanium plate for 1h, recrystallization has occurred below 570℃, and the grains have been basically equiaxed at 670℃, and the grains grow rapidly above 690°C. However, under this condition, no obvious recrystallized grains were observed for the 1.0mm cold-rolled titanium plate, but the grains were fine and uniformly distributed at 610-650℃.
(2) With the increase in annealing temperature, the yield strength and tensile strength of 0.5 and 0.1 mm cold-rolled titanium plate samples gradually decreased, and the rate of decrease of yield strength was faster than that of tensile strength. The change in elongation is not obvious in the experimental temperature range, but the increase in elongation in the cold-hard state is very large.
(3) Comprehensive structure and performance, the suitable annealing temperature of 0.5mm and 1.0mm cold-rolled titanium plates should be controlled at 630-670℃ and 610-650℃ respectively.
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