At present, there are two kinds of processing methods for large-caliber niobium pipe: one is to use niobium sheet, through the sheet rolling machine or the hydraulic press molding, and then welded into a round tube, after calibration, straightening, making a seam pipe; The other is to make seamless pipe through the method of cross rolling perforation, stretching and expanding, rolling. At present, the large diameter niobium tube manufactured at home and abroad is mainly produced by the first method, and the specifications of the invention are φ114 ~ φ245×3.0 ~ 30×2000 ~ 6000mm niobium large diameter pipe.
The tensile strength, yield strength and elongation of the large diameter thick wall seamless niobium pipe are ≥125MPa, ≥73MPa, ≥ 20%, and the ratio of outer diameter to wall thickness of the large diameter thick wall seamless niobium pipe is 5-65.
In step A, the vacuum degree of electron beam melting reaches 10-2Pa.
The process of three-high skew rolling perforation in step C is as follows:
(1) The heating process means of induction furnace and electric furnace insulation are used to control the heating temperature of the electric furnace through optical temperature measuring instruments to determine the uniform heating of the bar, and the temperature is controlled at ±10℃;
(2) Adjust the center line of the push cylinder, the rolling center line and the thrust bearing center line of the push rod trolley in the same line of the three-roll diagonal rolling punch machine;
(3) The top position is 30-100mm roll compression belt, and the top cooling water pressure is controlled at 0.3-0.8Mpa to ensure that the top can cool quickly and prevent stuffy running and stuck rolling;
(4) Select the appropriate head size, adjust the head position at the same time, ensure the thickness of the tube billet wall, control the rolling speed, the speed is 0.30-0.55m/s.
