Two-phase stainless steel and manufacturing method therefor

A technology of duplex stainless steel and manufacturing method, applied in the direction of manufacturing tools, furnace types, furnaces, etc., can solve the problems of expensive stainless steel, and achieve the effect of excellent corrosion resistance

Active Publication Date: 2019-11-19
NIPPON STEEL STAINLESS STEEL CORP
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, these stainless steels are relatively expensive, and it is necessary to further imp

Method used

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  • Two-phase stainless steel and manufacturing method therefor
  • Two-phase stainless steel and manufacturing method therefor
  • Two-phase stainless steel and manufacturing method therefor

Examples

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Embodiment

[0105] Examples are described below. Table 1 shows the chemical compositions of the test steels. These steels are obtained by hot-rolling molten materials in a laboratory, or by cutting out a part of actual manufacturing materials. For the components shown in Table 1, the parts without content are indicated as unavoidable impurity levels. REM means lanthanide rare earth elements, and the content indicates the total of those elements. Various heat treatments were applied to steel plates (thickness×100 mm width×300 mm length) obtained from these steels. A thermocouple was placed in the center of the thickness of the steel sheet to measure the temperature during the heat treatment, and the surface temperature of the steel sheet after it was extracted from the heat treatment furnace was measured with a radiation thermometer. The cooling of the steel plate is mainly performed by immersing it in a water tank.

[0106] First, put the steel plate into a heat treatment furnace for ...

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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. Theinventors 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 Nto 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 affectedthereby, 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 degrees centigrade followed by quick cooling to 600 degrees centigrade, the corrosion resistance can be improved.

Description

technical field [0001] The present invention relates to a duplex stainless steel material exhibiting excellent corrosion resistance in an environment close to brackish water or seawater with a high chloride ion concentration, and a method for producing the same. Background technique [0002] Duplex stainless steel contains a large amount of Cr, Mo, Ni, and N, and intermetallic compounds and nitrides tend to precipitate, so solution heat treatment at 1000°C or higher is performed to solid-solve the precipitates. Recently, an alloy element-saving duplex stainless steel has been developed that saves Ni, Mo, etc., contains Mn, and greatly reduces the precipitation sensitivity of intermetallic compounds. [0003] In alloying element-sparing duplex stainless steels, the main influencing precipitates are chromium nitrides. Chromium nitride is a precipitate combined with Cr (chromium) and N (nitrogen). In duplex stainless steel, it is mostly cubic CrN or hexagonal Cr 2 N precipita...

Claims

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Application Information

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IPC IPC(8): C22C38/00C21D6/00C22C38/58
CPCC21D6/00C22C38/00C22C38/58C21D9/46C21D6/004C21D8/0205C21D8/0226C21D8/02C22C38/44C22C38/48C22C38/02C22C38/04C22C38/06C22C38/002C22C38/005C22C38/42C22C38/52C22C38/46C22C38/50C22C38/54Y02P10/20C21D6/002C21D6/008C21D6/04C22C38/001C22C38/16C22C38/12
Inventor 柘植信二及川雄介
Owner NIPPON STEEL STAINLESS STEEL CORP
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