The preparation method of Ti-3Al-2.5V (Grade 9) titanium alloy thick-wall tube includes the process of ingot casting, forging, tube blank preparation, surface treatment, rolling and straightening. The characteristics are as follows: the rolling adopts the two-roll cold rolling method. (1) By adopting the production mode of two-high cold rolling, the tube billet is directly produced by 1-2 times of two-high cold rolling; (2) The surface quality can be improved by the way of inner surface boring and outer surface polishing; (3) The straightness of the product is guaranteed by the way of thermal straightening. The invention can greatly shorten the production cycle of the product, improve the surface quality of the product and ensure the straightness of the product.
The invention belongs to the special pipe for petroleum exploration in the technical field of petroleum exploration equipment. It is made of titanium alloy made of aluminum and vanadium added to titanium. The titanium alloy is made into titanium alloy pipes according to the following steps: (1) rolling: first, the original billet is extruded by an extruder or diagonal rolling perforated into a tube billet, then the burr crack on the surface is trimmed by a grinding wheel, the crack in the inner hole is removed by a deep-hole lathe, and the rolling is made by more than two times; (2) Annealing in step (1) when the deformation is greater than 10%, grinding, annealing temperature 560-640 degrees, heat preservation 2-4 hours, room temperature out of the oven. The invention has the advantages of non-magnetic titanium alloy pipe, corrosion resistance, high pressure resistance and high strength, prolongs the service life, and the titanium alloy pipe processed by the invention can achieve higher design requirements. The patent does not specify the specific rolling process and hot straightening technology.
(1) Ingot preparation: Sponge titanium and aluminum-vanadium alloy were used to mix and press electrode blocks according to the ratio of 2.0≤Al≤3.5%, 1.5≤V≤3.0%, C≤0.08%, N≤0.05%, H≤0.015%, O≤0.12%, Fe≤0.25%, and the electrode blocks were combined to prepare primary electrodes. The ingot is then prepared by two or three cycles of vacuum consumable arc melting.
(2) Forging: φ600mm ingot obtained by (1) is forged to φ220mm or φ180mm bar blank after three rounds (880 ~ 1100℃/2 ~ 6h).
(3) Preparation of tube billet: the tube billet is prepared by extrusion method or diagonal rolling perforation method. Before extruding, the bar billet should be skinned and drilled and coated with copper (1mm thick copper coil welding on the outer surface and 1.5mm thick copper tube on the inner surface). The extruding temperature is 700 ~ 850℃, and the heat is kept for 1 ~ 3 hours. In the cross rolling method, the intermediate frequency heating temperature of the tube billet is 750 ~ 950℃, and the heat preservation is 10 ~ 30 minutes.
(4) Surface treatment: pickling and washing or alkali washing, pickling and washing shall be carried out to remove the surface coating or surface oxide skin (in HF: H2SO4: HNO3: H2O=1.5 ~ 2.5:20:34 ~ 39: After soaking in 100 (volume ratio) mixed liquid for 1 ~ 3 hours, surface peeling (mechanical peeling or manual scraping) was carried out. The inner surface was treated by boring, and the amount of boring was 0.2 ~ 1.5mm. The outer surface of finished product was polished by mechanical polishing, and the amount of polishing was 0.1 ~ 0.3mm.
(5) Rolling: before rolling, vacuum heat treatment (annealing temperature 600 ~ 750℃, holding time 1 hour, not less than 1×10-1Pa) and (4) directly rolling after treatment, using two roller cold rolling billet one to three times of direct rolling finished products. Tube billet or semi-finished product inside the surface of the use of chlorinated paraffin, the outer surface of the use of oil and paraffin mixture for lubrication, rolling speed of 10 ~ 60 times/minute, rolling feed amount of 2 ~ 8mm, each time the deformation of 20 ~ 50%, the total processing rate of 30 ~ 70%.
