IP Library › Granted Patent US 6,918,967
Granted Patent B2
US 6,918,967 · App. 10/221,809 · Granted Jul 19, 2005

Corrosion resistant austenitic alloy

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Quick Facts
Patent No.
US 6,918,967
App. No.
10/221,809
Granted
Jul 19, 2005
Kind
B2
Abstract

An austenitic alloy having improved ductility/processability and improved pitting and crevice corrosion resistance comprising, in % by weight, about: 25-30% Ni; 19-23% Cr; 6-8% Mo; 0.3-0.5% N; 0.5% Mn; 0-1.5% Cu; 0-0.2% C; 0-1% Al; 0-0.01% S; 0-1% Ti; 0-1% Si; up to trace amounts of Mg, Ca, and Ce; and balance Fe plus incidental impurities.

Claims (74)

1. A corrosion resistant austenitic alloy consisting essentially of, in % by weight,

Ni: 26-30

Cr: 20-22

Mo: 6.5-7.5

N: 0.31-0.35

Mn: 0-5

Cu: 0-1.5

C: 0-0.2

Al: 0-1

S: 0-0.01

Ti: 0-1

Si: 0-1

Mg: up to trace amounts

Ca: up to trace amounts

Ce: up to trace amounts

Fe: balance including incidental impurities; and

wherein the alloy has a sigma solvus temperature of less than 2000° F. for improved processability and a pitting resistance equivalent number (PREN) of 50 or greater, wherein:

PREN=% Cr+3.3(% Mo)+30% N.

2. The alloy of claim 1 , including about 26-29% Ni; 20-22% Cr; 6.5-7.5% Mo and 0.33-0.35% N.

3. The alloy of claim 1 , including about 26-28% Ni; 20-21.5% Cr; 6.6-7.5% Mo and 0.33-0.35% N.

4. The alloy of claim 1 , including about 27% Ni; 21% Cr; 7.2% Mo; 0.33% N; 1.0 Mn and about 0.8 Cu.

5. A corrosion resistant austenitic alloy consisting essentially of, in % by weight,

Ni: 26-29

Cr: 20-22

Mo: 6.5-7.5

N: 0.31-0.35

Mn: 0-5

Cu: 0-1

C: 0-0.2

Al: 0-1

S: 0-0.01

Ti: 0-1

Si: 0-1

Mg: up to trace amounts

Ca: up to trace amounts

Ce: up to trace amounts

Fe: balance plus incidental impurities; and

wherein the alloy has a sigma solvus temperature of less than about 2000° F. for improved processability and has a pitting resistance equivalence number (PREN) of about 54 or greater, wherein:

PREN=% Cr+3.3(% Mo)+30(% N).

6. A corrosion resistant austenitic alloy consisting essentially of, in % by weight,

Ni: 26-28

Cr: 20-21.25

Mo: 6.6-7.5

N: 0.33-0.35

Mn: 0-5

Cu: 0-1

Al: 0-1

S: 0-0.01

Ti: 0-1

Si: 0-1

Mg: up to trace amounts

Ca: up to trace amounts

Ce: up to trace amounts

Fe: balance plus incidental impurities; and

wherein the alloy has a sigma solvus temperature of less than 2000° F. for improved processability and has a pitting resistance equivalence number (PREN) of about 54 or greater, wherein:

PREN=% Cr+3.3(% Mo)+30(% N).

7. A corrosion resistant austenitic alloy having a nominal composition consisting essentially of, in % by weight, about:

Ni: 27

Cr: 21

Mo: 7.2

N: 0.35

Mn: 0.5-1.5

Cu: 0.8

Al: 0-1

S: 0-0.01

Ti: 0-1

Si: 0-1

Mg: up to trace amounts

Ca: up to trace amounts

Ce: up to trace amounts

Fe: balance plus incidental impurities; and

wherein the alloy has a sigma solvus temperature of about 1900° F. for improved processability and has a pitting resistance equivalence number (PREN) of about 54 or greater, wherein:

PREN=% Cr+3.3(% Mo+30(% N).

8. The alloy of claim 7 , having a critical pitting temperature (CPT) of greater than 80° C. and a critical crevice corrosion temperature (CCT) of greater than 50° C.