US2026028708A1PendingUtilityA1
Austenitic stainless alloy with superior corrosion resistance
Est. expiryAug 29, 2038(~12.1 yrs left)· nominal 20-yr term from priority
Inventors:HARDING GRANT
C21D 2211/001C22C 38/001C22C 30/00C21D 8/005C21D 6/005C21D 6/004C21D 1/26C21D 1/18C22C 38/58C21D 8/00C22F 1/11C22C 27/06C22F 1/16
68
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Claims
Abstract
Austenitic stainless alloys have been discovered that exhibit unexpectedly superior corrosion resistance, particularly to sulfuric acid solutions, when compared to that exhibited by conventional alloys with closely related compositions. These alloys advantageously are corrosion resistant to a relatively wide range of sulfuric acid concentration and temperature and are thus particularly suitable for use in the industrial production of sulfuric acid.
Claims
exact text as granted — not AI-modified1 - 5 . (canceled)
6 . A method for making an austenitic stainless alloy comprising the steps of:
obtaining sources of chromium, nickel, manganese, nitrogen, and iron in a selected ratio; vacuum induction melting the sources thereby forming a molten mixture; casting the molten mixture thereby creating a solid precursor alloy; hot working the solid precursor alloy; solution annealing and quenching the solid precursor alloy thereby creating a quenched alloy; and removing heavy oxide scale from the quenched alloy thereby creating the austenitic stainless alloy; wherein the austenitic stainless alloy comprises the following composition in weight %:
36
-
40
%
chromium
;
32.5
-
36
%
nickel
;
1.55
-
1.75
%
manganese
;
0.37
-
0.48
%
nitrogen
;
0.03
-
0.43
%
silicon
;
<
0.02
%
carbon
;
<
0.02
%
phosphorus
;
<
0.04
%
molybdenum
;
<
0.02
%
copper
;
<
0.005
%
sulfur
;
and
remainder consisting essentially of iron.
7 . The method of claim 6 wherein the casting step is performed in air.
8 . The method of claim 6 wherein the solution annealing step is done at greater than or equal to 1150° C.
9 . The method of claim 6 comprising cold working the solid precursor alloy.
10 . The method of claim 6 wherein the removing heavy oxide scale step comprises pickling the quenched alloy.
11 . A method comprising employing an austenitic stainless alloy in a component exposed to high temperature and a concentrated solution of sulfuric acid, wherein the temperature of the solution is greater than or equal to 175° C., wherein the average concentration of sulfuric acid in the solution is greater than or equal to 98%, and wherein the austenitic stainless alloy comprises the following composition in weight %:
36
-
40
%
chromium
;
32.5
-
36
%
nickel
;
1.55
-
1.75
%
manganese
;
0.37
-
0.48
%
nitrogen
;
0.03
-
0.43
%
silicon
;
<
0.02
%
carbon
;
<
0.02
%
phosphorus
;
<
0.04
%
molybdenum
;
<
0.02
%
copper
;
<
0.005
%
sulfur
;
and
remainder consisting essentially of iron.
12 . The method of claim 11 wherein the temperature of the solution is in the range from 175° C. to 265° C.
13 . The method of claim 11 wherein the concentration of sulfuric acid in the solution is in the range from 98% to 99.5%.
14 . The method of claim 11 wherein the component is part of an industrial sulfuric acid production plant.
15 . The method of claim 14 wherein the component is part of a steam generating system in an industrial sulfuric acid production plant.
16 . The method of claim 11 wherein the component is a wrought or a cast product of the austenitic stainless alloy.
17 . The method of claim 6 wherein the austenitic stainless alloy comprises the following composition in weight %:
36
-
37
%
chromium
;
32.5
-
34
%
nickel
;
1.65
-
1.75
%
manganese
;
and
0.37
-
0.47
%
nitrogen
.
18 . The method of claim 6 wherein the austenitic stainless alloy comprises the following composition in weight %:
38
-
40
%
chromium
;
34.5
-
36
%
nickel
;
1.55
-
1.65
%
manganese
;
and
0.38
-
0.48
%
nitrogen
.
19 . The method of claim 6 wherein the austenitic stainless alloy comprises the following composition in weight %
36
-
40
%
chromium
;
32.5
-
36
%
nickel
;
1.55
-
1.75
%
manganese
;
and
0.37
-
0.48
%
nitrogen
.
20 . A method for making an austenitic stainless alloy comprising the steps of:
obtaining sources of chromium, nickel, manganese, nitrogen, and iron in a selected ratio; vacuum induction melting the sources thereby forming a molten mixture; casting the molten mixture thereby creating a solid precursor alloy; hot working the solid precursor alloy; solution annealing and quenching the solid precursor alloy thereby creating a quenched alloy; and removing heavy oxide scale from the quenched alloy thereby creating the austenitic stainless alloy; wherein the austenitic stainless alloy comprises the following composition in weight %:
36.01
-
38.93
%
chromium
;
32.95
-
35.4
%
nickel
;
1.62
-
1.7
%
manganese
;
0.42
-
0.43
%
nitrogen
;
0.03
-
0.43
%
silicon
;
<
0.02
%
carbon
;
<
0.02
%
phosphorus
;
<
0.03
%
molybdenum
;
<
0.02
%
copper
;
<
0.005
%
sulfur
;
and
remainder consisting essentially of iron.Cited by (0)
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