Oil industry TA18 titanium alloy thick-walled pipe technology
At present, my country mainly uses two-roll cold rolling and three-roll cold rolling to produce TA18 titanium alloy pipes. The main problems encountered in the production of TA18 titanium alloy thick-walled pipes used in the petroleum industry are: ①The use of multi-roll mills to roll thick-walled pipes with a diameter-to-thickness ratio of less than 10 has many rolling passes, and is prone to cracking and internal surface sticking Defects such as connection; ② The cold straightening method cannot guarantee the straightness of the finished pipe to meet the requirements of 0.3~1mm/m. In view of the above problems, the feasibility of producing TA18 titanium alloy thick-walled tubes by two different cold rolling processes was compared, the effect of annealing temperature on the structure and performance of the tubes, and the subsequent processing of the tubes were studied, aiming to produce oil for industrialization. Use high-quality TA18 titanium alloy thick-walled tubing to provide guidance.
The experimental TA18 titanium alloy is a Φ600mm×2400mm ingot obtained by smelting twice using a 3t vacuum consumable arc furnace. The ingot is then forged into a bar billet by a 16MN fast forging machine, and then drilled and bored by a deep hole drilling and boring machine, covered with a copper sheet, and extruded into a Φ70mm×8㎜ tube billet on a 3500t extruder. The tube blank adopts the following two cold rolling processes to roll Φ48mm×5mm finished pipe.
Process 1: Φ70mm×8㎜ tube billet, two-roll cold rolled blank→Φ54mm×6㎜, annealing, finishing→Φ54mm×6㎜, three-roll cold rolled→Φ51mm×5.5㎜, three-roll cold rolled→Φ48mm×5 ㎜Finished tube.
Process 2: Φ70mm×8㎜ tube billet, two-roll cold rolled blank→Φ54mm×6㎜, annealing, finishing→Φ54mm×6㎜, two-roll cold rolled→Φ48mm×5㎜ finished tube.
Vacuum annealing treatment of Φ48mm×5㎜ pipes produced by processes 1 and 2 according to 600℃×1h, 650℃×1h, 700℃×1h and 750℃×1h respectively, after heat treatment in RX-600 box resistance furnace Heat to 500~600℃ for 30min, straighten it, and use 150A14 feeler gauge to check its straightness. Then, through the methods of boring and mechanical polishing, the oxidation pollution layer on the inner and outer surfaces of the pipe is eliminated, and the finished pipe is finally obtained. The results showed that:
(1) Compared with process 1, the use of process 2 can more easily obtain TA18 thick-walled pipes that meet the requirements of the standard, and the rolling process is relatively stable, which not only shortens the production cycle, improves production efficiency, and its overall performance is also better than Pipe produced by process 1.
(2) 700℃×1h vacuum annealing, the room temperature mechanical properties of the pipe can be optimally matched, and the equiaxed grains are more uniform and fine.
(3) After heat straightening, the straightness of TA18 thick-walled pipe can reach about 0.75mm/m, and the inner surface roughness after boring is 0.864μm on average.