The use of creep strength enhanced ferritic alloys, such as Grade 91, in fossil power plants has become popular for high temperature applications. Since Grade 91 has higher stress allowables than Grade 22, a designer can specify thinner component wall thicknesses, resulting in lower throughwall thermal stresses during transient events and lower material and pipe support costs. During the past two decades, Grade 91 has been used successfully in fossil power plants. However, this alloy has had some incidents of premature failures. Case histories discuss such factors as excessively hard material, extremely soft material, overheating failures, and improper mill processing. This compilation also discusses likely root causes and solutions to avoid these potential Grade 91 problems.

Issue Section:
Research Papers
Keywords:
martensitic steel, high-temperature effects, thermal stresses, creep fracture, fracture toughness, pipes
Topics:
Creep, Pipes, Rupture, Stress, Temperature, Manufacturing, Failure, Fossil fuels, Wall thickness
1.
Beres
,
L.
,
Balogh
,
A.
, and
Irmer
,
W.
, 2001, “
Welding of Martensitic Creep-Resistant Steels
,”
Weld. J. (Miami, FL, U. S.)
0043-2296,
80
, pp.
191
-s–195-
s
.
2.
Santella
,
M. L.
,
Swindeman
,
R. W.
,
Reed
,
R. W.
, and
Tanzosh
,
J. M.
, 2001, “
Martensite Formation in 9Cr-1Mo Steel Weld Metal and its Effect On Creep Behavior
,”
EPRI Conference on 9Cr Materials Fabrication and Joining Technologies
, Myrtle Beach, SC.
3.
ASME
, 2001, “
2001 ASME Boiler and Pressure Vessel Code, Section 2, Part A, Ferrous Material Specifications
,”
Specification for Seamless Ferritic and Austenitic Alloy-Steel Boiler, Superheater, and Heat Exchanger Tubes SA-213∕SA-213M
,
The American Society of Mechanical Engineers
, New York.
4.
ASME
, 2001, “
2001 ASME Boiler and Pressure Vessel Code, Section 2, Part A, Ferrous Material Specifications
,”
Standard Specification for Seamless Ferritic Alloy-Steel Pipe for High Temperature Service, SA-335∕SA-335M
,
The American Society of Mechanical Engineers
, New York.
5.
ASME
, 2001, “
ASME B31.1-2001, Power Piping
,”
ASME Code for Pressure Piping, B31, An American National Standard
,
The American Society of Mechanical Engineers
, New York.
6.
Cohn
,
M.
, 2004, “
Fitness For Service, Life Extension, Remediation, Repair, and Erosion/Corrosion Issues For Pressure Vessel Components
,”
ASME Pressure Vessels and Piping Conference
, PVP
471
, pp.
93
–
103
.
7.
NRIM
, 1991, “
Data Sheets on the Elevated-Temperature Properties of Quenched and Tempered 214Cr-1Mo Steel Plates for Pressure Vessels (ASTM A542)
,” NRIM Creep Data Sheet No. 36A, National Research Institute for Metals, Tokyo, Japan.
8.
NRIM
, 1997, “
Data Sheets on the Elevated-Temperature Properties of Normalized and Tempered 214Cr-1Mo Steel Plates for Boilers and Pressure Vessels (SCMV 4 NT)
,” NRIM Creep Data Sheet No. 11B, National Research Institute for Metals, Japan.
9.
NRIM
, 1986, “
Data Sheets on the Elevated-Temperature Properties of 214Cr-1Mo Steel for Boiler and Heat Exchanger Seamless Tubes (STBA 24)
,” NRIM Creep Data Sheet No. 3B, National Research Institute for Metals, Tokyo, Japan.
10.
NRIM
, 1996, “
Data Sheets on the Elevated-Temperature Properties of 9Cr-1Mo-V-Nb Steel Tubes for Boilers and Heat Exchangers (ASME SA-213∕SA-213M Grade T91) and 9Cr-1Mo-V-Nb Steel Plates for Boilers and Pressure Vessels (ASME SA-387∕SA-387M Grade 91)
,” NRIM Creep Data Sheet No. 43, National Research Institute for Metals, Japan.
11.
Ellis
,
F. V.
,
Henry
,
J. F.
, and
Roberts
,
B. W.
, 1990, “
Welding, Fabrication, and Service Experience with Modified 9Cr-1Mo Steel
,”
New Alloys for Pressure Vessels and Piping, ASME Pressure Vessels and Piping Conference, PVP
201
, pp.
55
–
63)
.
Copyright © 2005
 by American Society of Mechanical Engineers
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