Microstructure and Properties of TA18 Titanium Alloy Tube
TA18 (Ti-3Al-2.5V) not only has good mechanical properties at room temperature and high temperature, corrosion resistance, but also has excellent hot and cold processing technology, formability and weldability, heat treatment can achieve superior strength and plastic matching. The alloy is not sensitive to the gap, in many media have excellent corrosion resistance, so in the aerospace pipeline system and the petrochemical industry has been a large number of applications.
Oblique rolling perforation method is the use of longitudinal and transverse along the rolling billet tensile stress, the central axis of the round billet metal micro-cracks, and then expanded into a loose area, the final formation of the cavity of the physical phenomenon, while the axial area When the metal is loose, the plug finishes the plastic processing in time and the rolling process of the solid round billet (forging billet or rolled billet) is directly rolled into a capillary tube. Because of the law with less equipment investment, without wrapping and lubrication, mold less consumption, high yield, low processing costs, etc., in the production of pure titanium and other tubes have been extensively used.
At present, domestic production of TA18 titanium alloy seamless pipe commonly used extrusion billet - rolling production methods. If the use of cross-piercing perforation prepared TA18 titanium alloy tube, tube can simplify the manufacturing process and improve the tube forming rate, so as to increase the overall rate of pipe material, reduce costs. Researchers used three-roll oblique hole rolling process for trial production of TA18 titanium alloy tube, and the ensuing cold workability of the slab tube was studied in order to provide a reference for the industrial production of TA18 titanium alloy seamless tube.
The experimental material is TA18 titanium alloy ingot twice melted by 3t vacuum consumable electric arc furnace. The ingot is forged in the β and α + β phase region, and machined to make Φ85mm 850mm bar.
The use of three-roll oblique piercing machine for the preparation of the tube, piercing the head of the molybdenum head. Billet perforated before using medium frequency induction furnace heating, heating temperature of 970, heating time of 5min. Φ85mm 850mm billet fire made Φ94mm 12mm L tube, the deformation of ε is 46%, the extension coefficient λ is 1.8.
The tube bank was cut longitudinally by a wire cutting method and annealed in a vacuum heat treatment furnace at annealing temperatures of 650 C 1h / FC, 700 C 1h / FC and 750 C 1h / FC. The microstructure of the as-machined (R) and annealed (M) as well as the oxide layers of the R-state bank were observed with a Leica MM-6 microscope. Shimadzu microhardness tester was utilized to test test the microhardness of the substrate region and the contaminated layer of the R-state blank tube, and at the same time, the tensile properties at room temperature were tested.
Φ94mm 12mm tube in the LG120 two-roll cold rolling machine with different deformation (34%, 44%, 55%, 65%) of the open-billet rolling, rolling pipe specifications Φ70mm 7mm. The pipe degreasing, pickling, and then 700 1h vacuum annealing. Comply with the surface morphology of the pipe, observe its microstructure, and choose the appropriate cold-rolled billet deformation.
LG60 / LD60 mill, the Φ 7mm Φ 70mm pipe cold-rolled into Φ48mm 5mm finished pipe. Finished pipe degreasing, pickling, and then at different temperatures (600,650,670,680,700,750) vacuum annealing, annealing time was 1h. Observe the microstructure of the finished pipe and test its tensile properties at room temperature. The results showed that:
(1) The TA18 titanium alloy tube processed by the cross-piercing perforation method has a deformed state of Weisenbau and a small amount of massive α-structure. After 700 1h / FC annealing, the room temperature mechanical properties are good, System requirements.
(2) TA18 titanium alloy cross-rolling perforation billet in the two-roll billet rolling, the deformation amount should be checked within 55%. Finished tube vacuum annealing system (650 ~ 670) 1h.
(3) Φ48mm 5mm finished pipe produced by using TA18 titanium alloy oblique-rolling tube bank whose mechanical properties fully meet the requirements of national military standard GJB3423-98 and American standard ASTM B338-2010.
TA18 (Ti-3Al-2.5V) not only has good mechanical properties at room temperature and high temperature, corrosion resistance, but also has excellent hot and cold processing technology, formability and weldability, heat treatment can achieve superior strength and plastic matching. The alloy is not sensitive to the gap, in many media have excellent corrosion resistance, so in the aerospace pipeline system and the petrochemical industry has been a large number of applications.
Oblique rolling perforation method is the use of longitudinal and transverse along the rolling billet tensile stress, the central axis of the round billet metal micro-cracks, and then expanded into a loose area, the final formation of the cavity of the physical phenomenon, while the axial area When the metal is loose, the plug finishes the plastic processing in time and the rolling process of the solid round billet (forging billet or rolled billet) is directly rolled into a capillary tube. Because of the law with less equipment investment, without wrapping and lubrication, mold less consumption, high yield, low processing costs, etc., in the production of pure titanium and other tubes have been extensively used.
At present, domestic production of TA18 titanium alloy seamless pipe commonly used extrusion billet - rolling production methods. If the use of cross-piercing perforation prepared TA18 titanium alloy tube, tube can simplify the manufacturing process and improve the tube forming rate, so as to increase the overall rate of pipe material, reduce costs. Researchers used three-roll oblique hole rolling process for trial production of TA18 titanium alloy tube, and the ensuing cold workability of the slab tube was studied in order to provide a reference for the industrial production of TA18 titanium alloy seamless tube.
The experimental material is TA18 titanium alloy ingot twice melted by 3t vacuum consumable electric arc furnace. The ingot is forged in the β and α + β phase region, and machined to make Φ85mm 850mm bar.
The use of three-roll oblique piercing machine for the preparation of the tube, piercing the head of the molybdenum head. Billet perforated before using medium frequency induction furnace heating, heating temperature of 970, heating time of 5min. Φ85mm 850mm billet fire made Φ94mm 12mm L tube, the deformation of ε is 46%, the extension coefficient λ is 1.8.
The tube bank was cut longitudinally by a wire cutting method and annealed in a vacuum heat treatment furnace at annealing temperatures of 650 C 1h / FC, 700 C 1h / FC and 750 C 1h / FC. The microstructure of the as-machined (R) and annealed (M) as well as the oxide layers of the R-state bank were observed with a Leica MM-6 microscope. Shimadzu microhardness tester was utilized to test test the microhardness of the substrate region and the contaminated layer of the R-state blank tube, and at the same time, the tensile properties at room temperature were tested.
Φ94mm 12mm tube in the LG120 two-roll cold rolling machine with different deformation (34%, 44%, 55%, 65%) of the open-billet rolling, rolling pipe specifications Φ70mm 7mm. The pipe degreasing, pickling, and then 700 1h vacuum annealing. Comply with the surface morphology of the pipe, observe its microstructure, and choose the appropriate cold-rolled billet deformation.
LG60 / LD60 mill, the Φ 7mm Φ 70mm pipe cold-rolled into Φ48mm 5mm finished pipe. Finished pipe degreasing, pickling, and then at different temperatures (600,650,670,680,700,750) vacuum annealing, annealing time was 1h. Observe the microstructure of the finished pipe and test its tensile properties at room temperature. The results showed that:
(1) The TA18 titanium alloy tube processed by the cross-piercing perforation method has a deformed state of Weisenbau and a small amount of massive α-structure. After 700 1h / FC annealing, the room temperature mechanical properties are good, System requirements.
(2) TA18 titanium alloy cross-rolling perforation billet in the two-roll billet rolling, the deformation amount should be checked within 55%. Finished tube vacuum annealing system (650 ~ 670) 1h.
(3) Φ48mm 5mm finished pipe produced by using TA18 titanium alloy oblique-rolling tube bank whose mechanical properties fully meet the requirements of national military standard GJB3423-98 and American standard ASTM B338-2010.
