Nippon Steel Corporation

Taketomo Yamazaki

Mikio Yamanaka

Satoshi Kado

Kotaro Yoshida

Katsuhiko Yabe

Tetsu Sakamoto

An austenitic heat-resistant steel which forms an oxide film mainly composed of Al.sub.2 O.sub.3 in a high-temperature oxidizing atmosphere, consisting essentially of not more than 0.2% of C, not more than 1.0% of Si, not more than 2.0% of Mn, 12 to 37% of Ni, 9 to 25% of Cr, more than 4.5 but not more than 6% of Al, and at least one member selected from the group consisting of Ti, Nb and Zr in a total amount of not more than 0.8%, with the balance being Fe; the .delta.-ferrite value of this steel, calculated from the formula set forth below, is from 0 to 7.9; this steel is removed of an internal oxide layer which has been formed just below the steel surface during hot working. ##EQU1## where Wi and Mi represent, respectively, the percent by weight and the atomic weight of Ti, Nb and Zr, and when the term ##EQU2## is negative this term is regarded as zero. This steel composition may contain one or more rare earth elements such as Y, Ce and La in a total amount of not more than 0.08%.

Austenitic heat-resistant steel which forms Al.sub.2 O.sub.3 film in

A ferritic stainless steel having high toughness both in the weld zone and the base metal comprising:

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Fujisawa, Japan

Taketomo Yamazaki