TWO-PHASE STAINLESS STEEL AND MANUFACTURING METHOD THEREFOR

Title:

TWO-PHASE STAINLESS STEEL AND MANUFACTURING METHOD THEREFOR

Document Type and Number:

WIPO Patent Application WO/2018/181990

Kind Code:

A1

Abstract:

The purpose of the present invention is to expand application to steel types having corrosion resistance of SUS329J1 or greater. The present invention addresses the problem of obtaining a two-phase stainless steel that both exhibits excellent corrosion resistance in environments with high chloride-ion concentration close to that of brackish water or seawater, and is economically advantageous. The inventors found that the effect of improving critical pitting temperature (CPT) was likely to be achieved when a minute amount of Nb was added after reducing the amount of Mn to less than 2.0%, and N to no more than 0.25%. The steel augmented with the minute amount of Nb was subjected to a solid-solution heat treatment, and on determining how depositions of Cr nitride and Nb nitride were affected thereby, the inventors developed a two-phase stainless steel made of a base material having improved corrosion resistance. When the ratio between the Cr amount [Cr] and the Nb amount [Nb] in extraction residue is brought to 0.2 or greater by controlling the depositions of the chrome nitride and the niobium nitride through gradual cooling to 800°C followed by quick cooling to 600˚C, the corrosion resistance can be improved.

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Inventors:

TSUGE SHINJI (JP)
OIKAWA YUUSUKE (JP)

Application Number:

PCT/JP2018/013892

Publication Date:

October 04, 2018

Filing Date:

March 30, 2018

Export Citation:

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Assignee:

NIPPON STEEL & SUMIKIN SST (JP)

International Classes:

C22C38/00; C21D6/00; C22C38/58

Domestic Patent References:

WO2012102330A1	2012-08-02
WO2014148540A1	2014-09-25
WO2009119895A1	2009-10-01

Foreign References:

JP2016053213A	2016-04-14
JP2012197509A	2012-10-18
JP2016053213A	2016-04-14

Other References:

HARUHIKO KAJIMURA: "215 216th Nishiyama Memorial Seminars", 2013, pages: 17
See also references of EP 3604593A4

Attorney, Agent or Firm:

AOKI, Atsushi et al. (JP)

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