Cr-Ni system austenitic heat-resisting steel exhibiting higher heat resistance than that of well-known austenitic stainless steels by means of which an atomic ratio of C being 0.05 to 0.30% to Ti being 0.01 to 0.8% and/or Nb (Ta) being 0.01 to 1.6% is within the range of 1.3 to 7, preferably 3 to 6 and the grain size is within the range of ASTM No. 3 to 8.
Method for direct heat treating austenitic stainless steel wire rod wherein a hot rolled austenitic stainless steel wire rod is rendered to finish the final finishing stand of a hot rolling mill at a temperature zone in the range of solution heat treatment, then the temperature zone of said solution heat treatment is so maintained that the austenitic crystal grain size is to be less than 7.0, and subsequently said wire rod is quenched to a temperature where no chromium carbide is precipitated at a cooling rate where no chromium carbide is precipitated.
The austenite alloy tube has a composition of 15.about.26% of Cr, 8.about.35% of Ni, 1.0% or less of Si, 2.0% or less of Mn and less than 0.25% of N and the balance of iron and impurities. The nitrogen content on the inner surface of the tube is at least 0.25%. If desired, one or more of 0.6% or less of Ti, 0.6% or less of Al, 3.0% or less of Mo and 1.0% or less of Nb may be incorporated.
The present invention is based on the discovery that radiation-induced voids which occur during fast neutron irradiation can be controlled by small but effective additions of titanium and silicon. The void-suppressing effect of these metals in combination is demonstrated and particularly apparent in austenitic stainless steels.
