 |
| Purchase Information |
| Use this form to request purchase information on API online subscriptions. |
|
|
Document API PUBL 959 is offered by IHS as part of an online subscription. This subscription contains many documents on the same topic.
You may also purchase this document alone from the IHS Standards Store.
API PUBL 959 Document Information:
Title
Characterization Study of Temper Embrittlement of Chromium-Molybdenum Steels
American Petroleum Institute
Publication Date:
Jan 1, 1982
Scope:
I. INTRODUCTION
In 1975 the API awarded a contract to Westinghouse R&D Center
(WRDC) to evaluate the temper
embrittlement characteristics of Cr-Mo pressure vessel steels. The
steels are designated A387 in
Part 4 of the ASTM Book of Standards. Most of the samples supplied
were of Grade 22)2-1/4Cr - 1Mo)
and a few samples of Grades 11 and 21 were also included (1-1/4Cr -
1/2Mo, 3Cr - 1Mo). The 64
samples received represented a large range of commercially produced
steel including qualification
welds in 1-in. and 6-in. plate, large nozzle cut-outs and randonly
shaped pieces of forging and
plate material. These materials had received heat treatment typical of
hydro-treater reactor
fabrication. The samples were typified by a simple code as follows:
FOR Forging
PLA Plate
SAW Submerged Arc Weld
ESW Electroslag Weld
SMA Shielded Metal Arc Weld
1 1-1/4Cr - 1/2Mo
2 2-1/4Cr - 1Mo
3 3Cr - 1Mo
The objective of this program was to characterize typical commercial
reactors steels and weldments
in terms of toughness due to long time service at elevated
temperature. It is important to note
that these materials were typical of commercial production and
fabrication up to about 1975, and
are not representative of the plate, forgings and weld metal, having
low temper embrittlement
susceptibility available today [1]. Phase I of the project included
the metallography and grain
size, the tensile properties and the Rockwell Hardnesses, the
analytical chemitries including the
tramp elements, the heat treatments and Charpy impact test data. The
latter yielded the Fracture
Appearance Transition Temperatures (FATT) and the 40 ft-lb Transition
Temperatures (40 ft-lb TT)
for the steels in the unembrittled and step-cooled embrittled
condition. The terms ΔFATT and
ΔT(40) refer to the change in FATT and the 40 ft-lb TT due to
temper embrittlement.
The main part of Phase II was the characterization of the isothermal
embrittlement of 25 steels
assessed in Phase I. Five isothermal embrittlement temperatures were
chosen at 75°F intervals
from 650° to 950°F. Tests to measure the amount of temper
embrittlement were carried out
after 1,000, 10,000 and 20,000 hours. A number of studies were also
performed in this time. These
were:
○ The effect of repeated de-embrittlement of the steel.
○ The effect of strength level and structure.
○ Auger analysis of grain boundaries of embrittled steels.
○ JIC measurements.
○ Effect of high pressure hydrogen on temper embrittlement.
○ Isothermal embrittlement of 1-1/4Cr and 3Cr steels.
By the end of 1976 the first phase of the program had been completed.
At this juncture in the
program a number of discrepancies, between the data generated at WRDC
and other laboratories, were
brought to light. These included the visual readings of the percentage
of brittle fracture on the
Charpy specimens, the conclusion that ΔFATT was not always equal
to ΔT(40), absolute
differences in the Charpy impact energy curves and the results of the
analytical chemistries. In
addition, it was found that in Phase I of the program WRDC had used a
Charpy specimen orientation
which was different than the one conventionally used by API.
As a consequence, a number of subsidiary experiments were intitiated
to clarify the various issues.
These included a comparative Charpy impact test study between Japan
Steel Works (JSW) and WRDC and
a comparative fracture surface evaluation study between Chicago Bridge
and Iron (CB&I) and WRDC
(see Appendix). At the same time, since the specimens for Phase II of
the program were machined in
the conventional API orientation, experiments designed to establish
the relationship between the
Phase I and Phase II orientations were carried out.
In addition, the API Task Group initiated a round robin comparative
analysis of samples and also
requested the National Bureau of Standards to establish a solid
2-1/4Cr - 1Mo Standard for
spectrographic analysis. As a direct result of the API Task Group
efforts, this standard designated
SRM 1270, is now available for public purchase from NBS. The
subsidiary experiments were carried
out during Phase II of the project which was concluded in 1980. This
paper reviews the primary
results of the programs.
About IHS
IHS (NYSE: IHS) is a leading global provider of critical technical information, decision-support tools and related services in a number of industries including aerospace and defense, automotive, construction, electronics, and energy. IHS serves customers ranging from large governments and multinational corporations to smaller companies and technical professionals in more than 100 countries. IHS been in business for more than 45 years and employ more than 2,300 people around the world.
