▎ 摘　　要

NOVELTY - Preparing titanium alloy large-diameter square thin-walled pipe comprises e.g. (a.i) heating the mold to 300-320 degrees C, insulating for 2 hours and preheating, fixing the preheated punch press rod on the upper mold of the press, and(a.ii) brushing the surface of the titanium alloy round tube billet with anti-oxidation paint and heating to 800 degrees C, placing the heated titanium alloy round tube into the mold, pushing the left punch and the right punch for moving to both sides respectively, expanding the round tube into a square tube. The anti-oxidation coating is prepared by (i) adding 10-15 pts. wt. silicon dioxide, 5-6 pts. wt. magnesium oxide, 5-8 pts. wt. silicon carbide, 2-3 pts. wt. zirconium dioxide, 1-3 pts. wt. calcium oxide and 5-6 pts. wt. ceramic powder, (ii) uniformly mixing silicon dioxide, magnesium oxide, silicon carbide, zirconium dioxide, calcium oxide, and ceramic powder, then grinding, and filtering with a 200-300 meshes filter. USE - The method is useful for preparing titanium alloy large-diameter square thin-walled pipe. ADVANTAGE - The method: has considerable production capacity; and simple equipment requirements and operation requirements; achieves the effect of increasing the yield rate; and reduces energy consumption. DETAILED DESCRIPTION - Preparing titanium alloy large-diameter square thin-walled pipe comprises (a.i) heating the mold to 300-320 degrees C, insulating for 2 hours and preheating, fixing the preheated punch press rod on the upper mold of the press, assembling and fixing base, female mold, left male mold, and the right male mold to the lower mold of the press, and applying lubricant on the surface of the fixed mold, and(a.ii) brushing the surface of the titanium alloy round tube billet with anti-oxidation paint and heating to 800 degrees C, placing the heated titanium alloy round tube into the mold obtained in the step (a.i), where the press presses down into the punch press rod, pushing the left punch and the right punch for moving to both sides respectively, expanding the round tube into a square tube to obtain titanium alloy large-diameter square thin-walled pipe. The anti-oxidation coating is prepared by (i) adding 10-15 pts. wt. silicon dioxide, 5-6 pts. wt. magnesium oxide, 5-8 pts. wt. silicon carbide, 2-3 pts. wt. zirconium dioxide, 1-3 pts. wt. calcium oxide and 5-6 pts. wt. ceramic powder, (ii) uniformly mixing silicon dioxide, magnesium oxide, silicon carbide, zirconium dioxide, calcium oxide, and ceramic powder, then grinding, and filtering with a 200-300 meshes filter to obtain base material, (iii) uniformly mixing graphite powder, potassium persulfate, phosphorus pentoxide, and 98% concentrated sulfuric acid, and reacting in a water bath at 80 degrees C for 4.5 hours, cooling to room temperature, diluting with deionized water, washing with deionized water for 3 times, placing in an oven at 70-80 degrees C and drying for 3-4 hours to obtain pre-oxidized graphite powder, (iv) adding pre-oxidized graphite powder to 98% concentrated sulfuric acid, adding 0.5 mol/l potassium permanganate solution dropwise, reacting in a water bath at 35 degrees C for 2 hours, then adding deionized water and stirring for 2 hours, then adding 30 wt.% hydrogen peroxide solution, washing for 3 times with 10 wt.% dilute hydrochloric acid solution, and suction filtering to obtain graphite oxide, dialyzing graphite oxide with water twice for a week to obtain 1 g/l aqueous solution, and carrying out ultrasonic treatment for 30 minutes to obtain a graphene oxide solution, (v) uniformly mixing the sodium metaaluminate and graphene oxide solution, adding hydrazine hydrate, transferring to the reaction kettle, hydrothermally reacting at 160 degrees C for 6 hours, freeze-drying at -50 degrees C to obtain aluminum oxide doped grapheme, and(vi) adding silicate and deionized water to the mixer, adding the base material and graphene doped with aluminum oxide, and uniformly stirring to obtain anti-oxidation coating.