Sumitomo Metal Industries, Inc.

Shigeki Azuma

Kazuhiro Ogawa

Yoshitaka Nishiyama

Hideo Yamamoto

Haruhiko Kajimura

Masayuki Sagara

Takeo Kudo

Kiyoko Takeda

Yoshio Tarutani

Yoshiaki Kusaba

Tadashi Fukuda

Hideaki Miyuki

Yasushi Matsuda

An austenitic stainless steel of the present invention has the following chemical composition based on percent by weight: C: 0.05% or less, Si: 1.0% or less, Mn: 2.0% or less, P: 0.04% or less, S: 0.01% or less, Ni: from 12 to 27%, Cr: from 15 to 26%, Cu: over 3.0 to 8.0%, Mo: over 2.0 to 5.0%, Nb: 1.0% or less, Ti: 0.5% or less, W: 5.0% or less, Zr: 1.0% or less, Al: 0.5% or less, N: under 0.05%, Ca: 0.01% or less, B: 0.01% or less, rare earth elements: 0.01% or less in total, and the balance Fe and unavoidable impurities. The austenitic stainless steel has excellent sulfuric acid corrosion resistance and excellent workability.

Austenitic stainless steel having excellent sulfuric acid corrosion resistance and excellent workability

A stainless steel having excellent corrosion resistance to ozone added water, such as ozone added ultrapure water used in semiconductor manufacturing processes and the like, as well as a manufacturing method. The stainless steel comprises a base metal and an oxide film formed on the surface of the base metal, the base metal being a stainless steel which contains 12 to 30% of Cr, 0 to 35% of Ni, and 1 to 6% of Al and Si while the contents of the other alloying elements are limited to as low a level as possible, the oxide film mainly comprising Al oxide or a Si oxide or both. The oxide film may be formed on the base metal surface through the dry oxidation process or the wet oxidation process. In the stainless steel, metallic ions are rarely dissolved from the base metal into the ozone added water. Also, since the contents of alloying elements, other than Cr, Ni, Al, Si, and like necessary elements, are limited to a low level, the stainless steel exhibits excellent corrosion resistance and reduced particle emission.

Stainless steel for ozone added water and manufacturing method thereof

Duplex stainless steel excellent in corrosion resistance

A method for improving the resistance to surface roughening of tungsten-containing metallic articles such as cutting tools and hot mill rolls made of a cemented carbide or high-speed steel and extending the lifetime thereof. The method comprises treating a metallic article with an aqueous alkaline solution containing calcium ions and optionally tungstate ions having a pH greater than 8 so as to form a coating of calcium tungstate on the surface of the metallic article. In hot rolling with tungsten-containing rolls, the aqueous solution can be used as at least part of a cooling water to cool the rolls, thereby extending the period before roll replacement becomes necessary due to surface roughening and decreasing the frequency of roll dressing required during hot rolling.

Method for minimizing surface roughening of tungsten-containing rolls

A high-Cr, high-Mo duplex stainless steel having excellent corrosion resistance as well as improved toughness and workability has a chemical composition which consists essentially, on a weight basis, of C: 0.03% or less, Si: 0.4% or less, Mn: 2.0% or less, Cr: 26.0-30.0%, Ni: 5.0-9.0%, Mo: 3.0 -4.5%, N: 0.10-0.35%, Al: 0.01-0.04%, optionally one or both of Cu and W in a total amount of 0.05-3.0% and/or one or more elements selected from Ca, B and Ce in a total amount of 0.001-0.01%, and a balance of Fe and incidental impurities, wherein the following inequality (1) is satisfied:

Duplex stainless steel having improved corrosion resistance

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Kobe, Japan

Shigeki Azuma