Rotatable anode target for X-ray tube, X-ray tube, and X-ray inspection apparatus

1. A method of manufacturing a rotatable anode target for an X-ray tube, comprising:

molding a first raw material powder containing at least one metal selected from the group consisting of molybdenum, tungsten, tantalum, niobium, and iron, or an alloy containing the at least one metal to form a first compact, sintering the first compact to form a sintered compact, and processing the sintered compact into a disc shape to form a metallic disc;

forming an X-ray irradiator on the disc;

molding a second raw material powder containing at least one metal selected from the group consisting of molybdenum, tungsten, tantalum, niobium, and iron, or an alloy containing the at least one metal of the second raw material powder to form a second compact and processing the second compact into a cylindrical shape to form a metallic cylinder; and

joining the disc and the cylinder,

wherein the disc has a plurality of first crystal grains in a first region within 2 mm from an interface between the disc and the cylinder, and the cylinder has a plurality of second crystal grains in a second region within 2 mm from the interface, and

wherein a first average aspect ratio of the first crystal grains is 1.3 or more and 1.8 or less, and a second average aspect ratio of the second crystal grains is 2.4 or more and 6.5 or less.

2. The method according to claim 1 ,

wherein a directional shift of an axis direction of each of the second crystal grains of 80% or more and 100% or less in number ratio per a unit area of 1000 μm×1000 μm to a length direction of the cylinder is 25 degrees or more and 25 degrees or less.

3. The method according to claim 1 ,

wherein an average grain size of the first crystal grains is 20 μm or more and 500 μm or less.

4. The method according to claim 1 ,

wherein an average grain size of the second crystal grains is 20 μm or more and 800 μm or less.

5. The method according to claim 1 ,

wherein the cylinder is joined with the disc by a brazing material therebetween.

6. The method according to claim 5 ,

wherein the brazing material contains at least one element selected from the group consisting of Ti, Zr, Hf, Pt, Co, Cr, Ni, and V.

7. The method according to claim 1 , further comprising:

forming a metal oxide coating film on the disc.

8. The method according to claim 7 ,

wherein the film contains a mixture of a titanium oxide and an aluminum oxide.

9. The method according to claim 1 , further comprising:

joining a graphite member to the disc.

10. The method according to claim 1 ,

wherein a thickness of the disc is 10 mm or more and 60 mm or less.

11. The method according to claim 1 ,

wherein the X-ray irradiator contains an alloy of Re and W.

12. The method according to claim 1 , further comprising:

providing a fixed shaft through the cylinder; and

applying a liquid-metal lubricant between the cylinder and the fixed shaft.

13. A method of manufacturing an X-ray tube, comprising:

manufacturing a rotatable anode for an X-ray tube by the method according to claim 1 ; and

providing a vacuum vessel which holds the anode and a cathode to irradiate an electron beam on the X-ray irradiator.

14. A method of manufacturing an X-ray inspection apparatus, comprising:

manufacturing an X-ray tube by the method according to claim 13 ;

providing a detector to detect transmitted X-ray; and

providing an image generator to generate an image corresponding to detected data from the detector.

15. The method according to claim 1 ,

wherein a working ratio of the sintered compact by the processing is 10% or more and 60% or less, and

wherein a working ratio of the second compact by forming the cylinder is 10% or more and 90% or less.