Abstract: 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.

Abstract: 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.

Abstract: An inexpensive, highly corrosion-resistant duplex stainless steel suitable for use in constructing piping systems, heat exchangers and the like to be installed in plants of oil refining industries, chemical industries and such. The highly corrosion-resistant duplex stainless steel has a chemical composition, in weight percent: 0.05 to 2.0% Si, 0.1 to 4.0% Mn, 1.0 to 4.0% Ni, 20.0 to 26.0% Cr, over 1.0 to 3.0% Cu, 0.002 to 0.05% Al, 0.10 to 0.40% N, 0.05 to 0.50% the sum of at least one of V, Ti and Nb, when necessary, 0.50% or less Mo, 0.50% or less W and 0.0030 or less B, 0.0030% or less Ca, and the balance of Fe and unavoidable impurities. Impurity contents are 0.05% or less C, 0.03% or less P and 0.005% or less S. The duplex stainless steel has Ni.sub.bal value expressed by the following Equation (1) in the range of -11.0 to -8.0:Ni.sub.bal =Ni.sub.eq -1.1.times.Cr.sub.eq +8.2 (1)whereNi.sub.eq =Ni(%)+0.5.times.Cu(%)+30.times.{C(%)+N(%)} (2)Cr.sub.eq =Cr(%)+1.5.times.Si(%)+Mo(%)+W(%) (3).

Abstract: 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.

Abstract: 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:-1.5.ltoreq.PBI.ltoreq.1.5 (1)where PBI=14.times.(Ni.sub.eq -0.61.times.CR.sub.eq +2.8)/(Cr.sub.eq -6)Ni.sub.eq (%)=Ni+0.5.times.Mn+30.times.(C+N){+Cu}Cr.sub.eq (%)=Cr+1.5.times.Si+Mo{+0.5.times.W}.