| 摘要 |
A billet of high purity niobium having a total content of oxygen, nitrogen and carbon of not greater than 60 ppm as impurities, a Vicker's hardness Hv of 50 or more and a relative residual resistance value RRP of 200 or more, and the billet is rolled to a sheet without hot forging. The resultant sheet has a high purity substantially equal to that of the billet and is therefore suitable for producing a super-conducting member, heat-resistant member, and so forth. A sheet of a high melting active metal having a high purity can be produced at a low cost with a high yield. It is possible to divide the rolling into a rough rolling and a precision rolling and to carry out heat-treatment between them. The sheet material may be produced by cold-pressing and rolling an ingot in place of the billet without hot-forging.
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