Sumitomo Metal Industries, Inc.

Hiroyuki Senba

Yoshiatsu Sawaragi

Masaaki Igarashi

Kaori Miyata

A heat resistant austenitic stainless steel having high strength at elevated temperatures. The steel consists of 0.05 to 0.15% carbon, not more than 0.5% silicon, 0.05 to 0.50% manganese, 17 to 25% chromium, 7 to 20% nickel, 2.0 to 4.5% copper, 0.10 to 0.80% niobium, 0.001 to 0.010% boron, 0.05 to 0.25% nitrogen, 0.003 to 0.030% sol.aluminum, 0 to 0.015% magnesium and the balance being iron and incidental impurities. The steel may contain 0.3 to 2.0% molybdenum and/or 0.5-4.0% tungsten. The steel exhibits high creep rupture strength at elevated temperatures for long periods of time, and can be produced at low cost. The steel is suitable for use in the structural members for boilers, chemical plants and other installations operated in a high temperature environment.

Austenitic heat resistant steel excellent in elevated temperature

The present invention discloses high chromium ferritic heat-resistant steel which has remarkable properties that the base metal and welded joints of the steel both exhibit excellent long term creep strength at elevated temperatures over 600.degree. C. excellent resistance to steam oxidation, and excellent toughness at room temperatures. The chemical composition of main elements of the steel of the invention is as follows:

High chromium ferritic heat-resistant steel

A high Cr austenitic heat resistant alloy excellent in high temperature strength which essentially consists of, in weight percent, from more than 0.02% to 0.10% C, not more than 1.0% Si, not more than 2.0% Mn, 28 to 38% Cr, 35 to 60% Ni, from more than 0.5% to 1.5% Ti, not more than 0.05% N, 0.01 to 0.3% Al, 0.001 to 0.01% B, 0 to 0.1% Zr, 0 to 1.0% Nb, one or both of 0.5 to 3.0% Mo and 1.0 to 6.0% W, and the balance being Fe and incidental impurities. The alloy may further contain one or both of 0.001 to 0.05% Mg and 0.001 to 0.05% Ca. This alloy is suitable for producing a single layered tube which is less expensive and more reliable than the conventional double layered tube.

Growing community of inventors

Nishinomiya, Japan

Hiroyuki Senba