Incoloy 27-7MO

INCOLOY alloy 27-7MO 
Sheet and Plate 
UNS S31277

Fe Base, Ni 27, Cr 22, Mo 7, Cu 1

High Performance Alloys stocks and produces this grade in the following forms: sheet, plate, coil. Request quote on this grade.

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INCOLOY® alloy 27-7MO (UNS S31277) is an advanced 7% molybdenum super-austenitic stainless steel offering corrosion resistance in most environments superior to 6% molybdenum super-austenitic stainless steels. In many environments alloy 27-7MO offers resistance approaching that of much more highly alloyed materials such as INCONEL alloys 625, 22, and C-276. Alloy 27-7MO products typically contain 27% nickel, 22% chromium, 7.2% molybdenum, and 0.34% nitrogen. Its limiting chemical composition is presented in Table 1. The alloy's content of nickel and nitrogen produce a stable austenitic structure. By virtue of its content of molybdenum, chromium, and nitrogen, alloy 27-7MO offers excellent resistance to pitting and crevice corrosion. The nickel, nitrogen, and molybdenum provide resistance to reducing media while a high content of chromium offers resistance to oxidizing media. Alloy 27-7MO performs well in mixed acid environments, especially those containing oxidizing and reducing acids. The alloy's contents of nickel and nitrogen result in resistance to stress corrosion cracking and attack by caustic media. Alloy 27-7MO offers excellent resistance to corrosion in seawater and brine. It also resists stress corrosion cracking in all concentrations of sodium chloride up to saturation at the boiling point. It is resistant to the aggressive media encountered in air pollution control systems such as flue gas desulfurization equipment for high-sulfur coal-fired electric power utilities. Applications for INCOLOY alloy 27-7MO are found in the pollution control, power, marine, chemical processing, pulp and paper and oil and gas industries. The alloy offers a unique combination of corrosion resistance, high strength and ease of fabrication at an economical price. Alloy 27-7MO is available in standard product forms including plate, sheet, rod, bar, wire rod, pipe, tube, and forging stock.

Corrosion Resistance

Pitting Resistance Equivalency Number - A means of comparing the corrosion resistance of alloys is by their Pitting Resistance Equivalency Number or 'PREN'. Alloys exhibiting higher PREN values are generally found to be more resistant to localized corrosion than those with lower PREN values. The PREN can be calculated by several different equations based upon the chemical composition of the alloys. Some equations are applicable to stainless steels while others are better applied to nickel-based alloys. The equation used here is generally accepted as being applicable to a wide range of alloy compositions. When comparing alloys by their PREN it is absolutely necessary that the same equation be used for all materials to be compared. Comparing alloys by PRENs generated from different equations will give erroneous results. For more information on the use of PRENs to compare the corrosion resistance of materials, refer to the Special Metals publication, “High Performance Alloys for Resistance to Aqueous Corrosion” or visit the Special Metals website, www.specialmetals.com. PRENs for alloy 27-7MO and similar materials are seen in Table 5. Based on these values of PREN, alloy 27-7MO would be predicted to offer significantly better corrosion resistance than alloy 25-6MO (and similar grades of super-austenitic

Resistance to Corrosion by SeawaterNickel-chromium alloys and austenitic and super-austenitic stainless steels containing molybdenum are well known for their resistance to corrosion in seawater and marine environments. A test program conducted at the LaQue Center for Corrosion Technology in Wrightsville Beach, North Carolina (a laboratory well known for marine corrosion testing) produced data showing that INCOLOY alloy 27-7MO offers corrosion-resistance superior to many of the corrosion-resistant alloys commonly used in marine service. Samples of sheet to which Teflon crevice devices were attached were exposed to flowing natural seawater at

Applications

Applications for INCOLOY alloy 27-7MO are found in the pollution control, power, marine, chemical processing, pulp and paper and oil and gas industries. The alloy offers a unique combination of corrosion resistance, high strength and ease of fabrication at an economical price. Alloy 27-7MO is available in standard product forms including plate, sheet, rod, bar,

Chemical Requirements

Ni

Cr

Mo

Mn

C

Si

Cu

Fe

Max

26.0

20.5

6.5

3.00

0.02

0.5

1.5

Bal.

Min

28.0

23.0

8.00

0.5

Mechanical Property Requirements

Ultimate Tensile

Yield Strength (0.2% OS)

Elong.

R/A

Hardness

Min

120 KSi

60 KSi

50

Rb 95

Max

Min

827 MPa

414 MPa

Max

Specifications

Form

Standard

Metal Type

UNS S31277

Bar

ASTM A 479/ASME SA 479

Wire

ASTM A 479/ASME SA 479

Sheet

ASTM A 240/ASME SA 240

Plate

ASTM A 240/ASME SA 240

Tube
ASTM A 213/ASME SA 213 (Tube), ASTM A 249/ASME SA 249
Pipe
ASTM A 312/ASME SA 312

Fitting

ASTM A182

Forging

ASTM A 479/ASME SA 479, ASTM A182

Weld Wire

Weld Electrode

ASME CODE

Allowable design stresses for ASME Boiler and Pressure Vessel Code construction are defined in ASME Code Case 2458.

Din

Machinability RATING: 27% of B-1112

TYPICAL STOCK REMOVAL RATE: 45 surface feet/minute with high speed tools, 125 surface feet/minute with carbide.

Machining Guide

Operation

Tool
Type

Speed
SFPM

Feed
Inch Per Rev.

Depth in Cut
Inch

Cut Type

Turning

 

WC

68
88

.009-.016
.006-.009

.050-.100
.011-.015

Rough
Finish

HSS

18
21

.007-.011
.003-.008

.025-.045
.008-.011

Rough
Finish

Facing

 

WC

68
88

.009-.016
.006-.009

.040-.075
.011-.015

Rough
Finish

HSS

18
21

.007-.011
.003-.008

.025-.045
.008-.011

Rough
Finish

Boring

WC

42
53

.009-.016
.006-.009

.043-.060
.012-.015

Rough
Finish

Drilling

HSS

18
25

.003-.007
.002-.004

---
---

Rough
Finish

Reaming

HSS

25
35

.006-.010
---

---
.012-.015

Rough
Finish

Shaping

 

WC

20
30

---
.005-.010

.060-.090
.018-.025

Rough
Finish

HSS

13
15

---
.005-.010

.050-.080
.018-.025

Rough
Finish

Milling

HSS

15
25

1/2-1 IPM

.100-.200 in. cut

Rough
Finish

INCOLOY® is a registered trademark of Special Metals Corporation

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