Title:
FORMATION OF OXIDIZED PASSIVE COATING ONTO FERRITIC STAINLESS STEEL
Document Type and Number:
Japanese Patent JP3446520
Kind Code:
B2
Abstract:
PROBLEM TO BE SOLVED: To prevent a stainless steel from being easily corroded in environments in which thick salt water, storing acid soln. and strong alkaline soln. are present by degreasing and washing a ferritifc stainless steel, removing moisture from the surface and executing heat treatment at a specified temp. in an atmosphere of a gaseous mixture having a specified compsn.
SOLUTION: A ferritic stainless steel in which the total content of Cr and Mo is regulated to ≥25wt.% by the compositional formula of Cr+4Mo is subjected to heat treatment. This ferritic stainless steel is subjected to heat treatment at 1000 to 1100°C in a gaseous mixture composed of, by volume, 80 to 88% nitrogen, 1 to 5% gaseous hydrogen, 1 to 5% carbon monoxide, 5 to 15% carbon dioxide and 0.05 to 0.2% gaseous oxygen. Cr oxide preferentially precipitates on the surface of the stainless steel to form oxidized passive coating high in durability. Gaseous hydrogen, carbon monoxide and carbon dioxide have reducing effect by which iron oxide is not formed on the surface of the stainless steel, but they have no reducing operation to chromium oxide.
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Inventors:
Kurumizawa Toshimitsu
Tadami Suzuki
Shuzo Tokuman
Tadami Suzuki
Shuzo Tokuman
Application Number:
JP4558397A
Publication Date:
September 16, 2003
Filing Date:
February 28, 1997
Export Citation:
Assignee:
Matsushita Electric Industrial Co., Ltd
International Classes:
C23C16/40; C23C8/14; C23C8/18; (IPC1-7): C23C8/14; C23C8/18
Domestic Patent References:
| JP6116632A | ||||
| JP60230962A | ||||
| JP105821A | ||||
| JP1018018A | ||||
| JP9176824A |
Attorney, Agent or Firm:
Fumio Iwahashi (2 others)