High-nitrogen austenitic stainless steel

Abstract

A high-nitrogen austenitic stainless steel, containing 0.005 mass %≦C≦0.25 mass %; 15.0 mass %≦Cr≦35.0 mass %; 0.2 mass %<Mn<10.0 mass %; 0.05 mass %≦Mo≦8.0 mass %; 0.01 mass %≦Cu≦4.0 mass %; 0.01 mass %≦Ni<5.0 mass %; 0.8 mass %<N≦1.8 mass %; Si≦2.0 mass %; P≦0.03 mass %; S≦0.05 mass %; Al≦0.030 mass %; 0≦0.020 mass %, and the balance substantially including Fe and impurities, and having a PRE (=(Cr+3.3Mo+16N)/Mn (mass %)) of not less than 5 and a CRE (=Cr+1.5Mo+2N+Cu (mass %)) of not less than 27.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to high-nitrogen austenitic stainless steel and, more specifically, high-nitrogen austenitic stainless steel which is excellent in seawater corrosion resistance and strength, and nonmagnetic. [0003] 2.Description of the Related Art [0004] Austenitic stainless steel is generally excellent in corrosion resistance, but may cause corrosion depending on its using environment. For example, it is known that, when austenitic stainless steel is dipped in a halide aqueous solution, the passive film is broken by a halogen ion such as Cl- or Br-, causing local corrosion (pitting, crevice corrosion). For prevention of such a local corrosion, the following are known to be effective: [0005] (1) Strengthening of passive film by increasing the amount of Cr [0006] (2) Reduction of active dissolution by addition of Mo, increase in amount of Ni, or the like [0007] (3) Addition of N. [0008] Therefore, for a...

AI Technical Summary

Benefits of technology

[0046] When the content of each component element is optimized so that the PRE and the CRE are within predetermined ranges, high strength can be obtained in addition to improvement in seawater corrosion resistance. The optimization of the content of each component element enables dissolution of Cr nitrides with diameter of not less than 2 μm by the solution treatment of 1050 to 1250C. When the content of each com

Problems solved by technology

Austenitic stainless steel is generally excellent in corrosion resistance, but may cause corrosion depending on its using environment.

For example, it is known that, when austenitic stainless steel is dipped in a halide aqueous solution, the passive film is broken by a halogen ion such as Cl- or Br-, causing local corrosion (pitting, crevice corrosion).

The super stainless steel is excellent in seawater corrosion resistance, however, it is hard to say that it has sufficient strength.

On the other hand, the application of Ni-based alloy and Ti alloy has also been examined for a portion requiring strength and corrosion resistance, however, the Ni-based alloy and Ti alloy are expensive and of excessive quality.

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