Patent ID: 9689051
Date: 2017-06-27
CPC Classifications: C21D,C22C,Y10T

Claim:
1. A hollow seamless pipe, comprising: a steel material comprising 0.2 to 0.7 mass % of C, 0.5 to 3 mass % of Si, 0.1 to 2 mass % of Mn, more than 0 mass % and 0.1 mass % or less of Al, more than 0 mass % and 0.02 mass % or less of P, more than 0 mass % and 0.02 mass % or less of S, more than 0 mass % and 0.02 mass % or less of N, and Fe, wherein a C content in an inner peripheral surface and an outer peripheral surface of the hollow seamless pipe is 0.10 mass % or more, a thickness of a whole decarburized layer in each of the inner peripheral surface and the outer peripheral surface of the hollow seamless pipe is 200 μm or less, and an average grain size of ferrite in an inner surface layer part of the hollow seamless pipe is 11.7 μm or less.