Duplex stainless steel, duplex stainless steel slab, and duplex stainless steel material

Abstract

One aspect of this duplex stainless steel contains, in mass %, C: 0.03% or less, Si: 0.05% to 1.0%, Mn: 0.1% to 7.0%, P: 0.05% or less, S: 0.0001% to 0.0010%, Ni: 0.5% to 5.0%, Cr: 18.0% to 25.0%, N: 0.10% to 0.30%, Al: 0.05% or less, Ca: 0.0010% to 0.0040%, and Sn: 0.01% to 0.2%, with the remainder being Fe and inevitable impurities, wherein a ratio Ca / O of the amounts of Ca and O is in a range of 0.3 to 1.0, and a pitting index PI shown by formula (1) is in a range of less than 30,PI=Cr+3.3Mo+16N  (1).

Description

TECHNICAL FIELD[0001]The present invention relates to an inexpensive Sn-containing duplex stainless steel. In addition, the present invention relates to an inexpensive duplex stainless steel which contains a combination of Cu and Sn and which is excellent in corrosion resistance. In detail, the present invention relates to a duplex stainless steel, a duplex stainless steel slab (a cast steel of a duplex stainless steel), and a duplex stainless steel material which are able to be used in a seawater desalination unit, tanks for a transport ship, various types of containers, or the like.[0002]This application is a national stage application of International Application No. PCT / JP2012 / 076821, filed on Oct. 17, 2012, which claims priority to Japanese Patent Application No. 2011-231352 filed on Oct. 21, 2011 in Japan, and Japanese Patent Application No. 2011-266351 filed on Dec. 6, 2011 in Japan, the contents of which are incorporated herein by reference.BACKGROUND ART[0003]A general-purp...

AI Technical Summary

Benefits of technology

The Sn-containing duplex stainless steels achieve improved corrosion resistance and manufacturability, making them suitable for applications in seawater desalination units, transport ship tanks, and containers while maintaining cost-effectiveness.

Problems solved by technology

However, as a result of containing Mo and Ni, which are expensive, the alloy cost is high and the manufacturability is not favorable.

As a result, the price of steel material is not cheap and the duplex stainless steel is not widely used in place of 316 grade stainless steel or 317 grade stainless steel.

In these steels where the amounts of alloy elements which are effective for pitting resistance and acid resistance are reduced, it is difficult to obtain the same level of corrosion resistance as that of the general-purpose duplex stainless steel.

However, it was learned that the hot manufacturability decreased in duplex stainless steels which contained a large amount of Sn.

For this reason, the frequency of decreases in the yield of the steel material will increase and a significant cost increase is predicted.

However, it was learned that the hot manufacturability decreased in duplex stainless steels which contained a large amount of Sn and Cu.

For this reason, the frequency of decreases in the yield of the steel material will increase and a significant cost increase is predicted.

As a result, it was found that there was little knowledge with regard to the relationship between the temperature range where hot embrittlement occurs due to Sn which is included in the duplex stainless steel and the amount of Sn and the relationship with the amounts of other elements.

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