Fracture Behavior in West Jefferson Test Under Low-Temperature Condition for X65 Steel Pipe With High Charpy Energy: Current Activities in HLP Committee, Japan, Report 1

2016 ◽  
Author(s):  
Toshihiko Amano ◽  
Satoshi Igi ◽  
Takahiro Sakimoto ◽  
Takehiro Inoue ◽  
Shuji Aihara
Keyword(s):  
Transition Temperature ◽  
Low Temperature ◽  
Brittle Fracture ◽  
Pressure Vessel ◽  
Fracture Behavior ◽  
Line Pipe ◽  
Burst Test ◽  
Pipe Burst ◽  
Test Vessel ◽  
Fracture Appearance

This paper describes the results of pressure vessel fracture test which called West Jefferson and/or partial gas burst testing using Grade API X65 linepipe steel with high Charpy energy that exhibits inverse facture in the Drop Weight Tear Test (DWTT). A series of pressure vessel fracture tests which is as part of an ongoing effort by the High-strength Line Pipe committee (HLP) of the Iron and Steel Institute of Japan (ISIJ) was carried out at low temperature in order to investigate brittle-to-ductile transition behavior and to compare to DWTT fracture behavior. Two different materials on Fracture Appearance Transition Temperature (FATT) property were used in these tests. One is −60 degree C and the other is −25 to −30 degree C which is defined as 85 % shear area fraction (SA) in the standard pressed notch DWTT (PN-DWTT). The dimensions of the test pipes were 24inches (609.6 mm) in outside diameter (OD), 19.1 mm in wall thickness (WT). In each test, the test pipe is cooled by using liquid nitrogen in the cooling baths. Two cooling baths are set up separately on the two sides of the test vessel, making it possible to obtain fracture behaviors under two different test temperatures in one burst test. The test vessel was also instrumented with pressure transducers, thermocouples and timing wires to obtain the pressure at the fracture onset, temperature and crack propagation velocity, respectively. Some informative observations to discuss appropriate evaluation method for material resistance to brittle facture propagation for high toughness linepipe materials are obtained in the test. When the pipe burst test temperatures are higher than the PN-DWTT transition temperature, ductile cracks were initiated from the initial notch and propagated with short distance in ductile manner. When the pipe burst test temperatures were lower than the PN-DWTT transition temperature, brittle cracks were initiated from the initial notch and propagated through cooling bath. However, the initiated ductile crack at lower than the transition temperature was not changed to brittle manner. This means inverse facture occurred in the PN-DWTT is a particular problem caused by the API DWTT testing method. Furthermore, results for the pipes tested indicated that inverse facture occurred in PN-DWTT at the temperature above the 85 % FATT may not affect the arrestability against the brittle fracture propagation and it is closely related with the location of brittle fracture initiation origin in the fracture appearance of PN-DWTT.

Determination of Brittle-to-Ductile Transition Temperatures of Large-Diameter TMCP Linepipe Steel With High Charpy Energy by Use of Modified West Jefferson Testing

2016 ◽  
Author(s):  
Y. Hioe ◽  
G. Wilkowski ◽  
M. Fishman ◽  
M. Myers
Keyword(s):  
Transition Temperature ◽  
Brittle Fracture ◽  
Large Diameter ◽  
Pipe Steels ◽  
Line Pipe ◽  
Brittle To Ductile Transition ◽  
Pipe Burst ◽  
Drop Weight Tear Test ◽  
Fracture Appearance ◽  
Shear Area

In this paper the results will be presented for burst tests from a Joint Industry Project (JIP) on “Validation of Drop Weight Tear Test (DWTT) Methods for Brittle Fracture Control in Modern Line-Pipe Steels by Burst Testing”. The JIP members for this project were: JFE Steel as founding member, ArcelorMittal, CNPC, Dillinger, NSSMC, POSCO, Tenaris, and Tokyo Gas. Two modified West Jefferson (partial gas) pipe burst tests were conducted to assess the brittle-to-ductile transition temperature and brittle fracture arrestability of two 48-inch diameter by 24.6-mm thick X65 TMCP line-pipe steels. These steels had very high Charpy energy (350J and 400J) which is typical of many modern line-pipe steels. In standard pressed-notch DWTT specimen tests, these materials exhibited abnormal fracture appearance (ductile fracture from the pressed notch prior to brittle fracture starting) that occurs with many high Charpy energy steels. Such behavior makes the transition temperature difficult to determine. The shear area values versus temperature results for these two burst tests compared to various modified DWTT specimens are shown. Different rating methodologies; DNV, API, and a Best-Estimate of steady-state fracture propagation appearance were evaluated.

Modified West Jefferson Burst Test for Assessment of Brittle Fracture Arrest in Thick-Wall TMCP Line-Pipe Steel With High Charpy Energy

2016 ◽  
Author(s):  
S. Igi ◽  
T. Sakimoto ◽  
J. Kondo ◽  
Y. Hioe ◽  
G. Wilkowski
Keyword(s):  
Transition Temperature ◽  
Brittle Fracture ◽  
Ductile Fracture ◽  
Base Metal ◽  
The Other ◽  
Line Pipe ◽  
Burst Test ◽  
Seam Weld ◽  
Shear Area ◽  
Fracture Arrest

Three partial gas pipe burst tests were conducted to assess the brittle-to-ductile transition temperature and brittle fracture arrestability of a heavy-walled TMCP line-pipe steel. This steel had a very high Charpy energy (400 J) which is typical of many modern line-pipe steels. In standard pressed-notch DWTT specimen tests this material exhibited abnormal fracture appearance (ductile fracture from the pressed notch prior to brittle fracture starting) that occurs with many high Charpy energy steels. Such behavior gives an invalid test by API RP 5L3, which makes the transition temperature difficult to determine. The first burst test was conducted in a manner that is typical of a traditional West Jefferson (partial gas vessel) burst tests. The crack was initiated in the center of the cooled vessel (with a partial air gap), but an unusual result occurred. In this test a ductile fracture just barely started from each crack tip, but one of the endcaps blew off. The pipe rocketed into the wall of a containment building. The opposite endcap impacted the wall of the building and brittle fractures started there with one coming back to the center of the vessel. The implication from this test was that perhaps initiation of the brittle fracture in the base metal gives different results than if the initial crack came from a brittle location. The second burst test used a modified West-Jefferson Burst Test procedure. The modification involved cutting a short length of pipe at the center of the vessel and rotating the seam weld to the line of crack propagation. The HAZ of the axial seam weld had a higher dynamic transition temperature. The initiation flaw was across one of the center girth welds so that one side of the initial through-wall crack had the crack tip in the base metal while the other side initiated in the seam weld HAZ. On the base metal side, the crack had about 220 mm of crack growth before reaching steady-state shear area, i.e., the shear area gradually decreased as the fracture speed was increasing. On the other side, a brittle fracture was started in the HAZ as expected, and once it crossed the other central girth weld into the base metal, the fracture immediately transformed to a lower shear area percent. These results along with those from the first burst test suggest that the DWTT specimen should have a brittle weld metal in the starter notch region to ensure the arrestability of the material. The final burst test was at a warmer temperature. There was a short length of crack propagation with higher shear area percent, which quickly turned to ductile fracture and arrested. In addition various modified DWTTs were conducted and results were analyzed using an alternative brittle fracture arrest criterion to predict pipe brittle fracture arrestability.

Conservative estimations of irradiation embrittlement of reactor pressure vessel steels for WWER-1000 lifetime prediction

2019 ◽  
Vol 15 (1) ◽  
pp. 246-257
Author(s):  
Nikolai Petrovich Anosov ◽  
Vladimir Nikolaevich Skorobogatykh ◽  
Lyubov’ Yur’yevna Gordyuk ◽  
Vasilii Anatol’evich Mikheev ◽  
Egor Vasil’yevich Pogorelov ◽  
...  
Keyword(s):  
Transition Temperature ◽  
Brittle Fracture ◽  
Pressure Vessel ◽  
Reactor Pressure Vessel ◽  
Lifetime Prediction ◽  
Critical Brittleness Temperature ◽  
Irradiation Embrittlement ◽  
Content Type ◽  
Brittleness Temperature ◽  
Reactor Pressure

Purpose The purpose of this paper is to consider a procedure of water-water energetic reactor (WWER) reactor pressure vessel (RPV) lifetime prediction at the stages of design and lifetime extension using the standard irradiation embrittlement parameters as defined in regulatory documents. A comparison is made of the brittle fracture resistance (BFR) values evaluated using two criteria: shift in the critical brittleness temperature ΔTc or shift in the brittle-to-ductile transition temperature ΔTp and without shifts (Tc and Tp). Design/methodology/approach The radiation resistance was determined using the following three approaches: calculation based on standard values ΔTc and Tc0 or ΔTp and Tp0 (a level of excessive conservatism); calculation based on standard value ΔTc and actual value Tc0 or actual values ΔTp and Tp0 (the level of realistic conservatism); or calculation based on actual values of Tc and Tc0 or Tp and Tp0 (the level of actual conservatism). The BFR was evaluated based on the results of testing the specimens subjected to irradiation in research reactors as well as surveillance specimens subjected to irradiation immediately under operating conditions. Findings The excessive conservatism in determining the actual lifetime of nuclear reactor vessel materials can be eliminated by using the immediate values of critical brittleness temperature and ductile-to-brittle transition temperature. Originality/value Obtained results can be applied to extend WWER vessel operating time at the stages of designing and operation due to substantiated decrease in conservatism. And it will allow carrying out a statistical substantiated assessment of the resistance to brittle fracture of the RPV steels.

Brittle Fracture Arrest in High Charpy Energy Steels: Comparisons With Some Existing Data

2014 ◽  
Author(s):  
G. Wilkowski ◽  
D-J. Shim ◽  
Y. Hioe ◽  
S. Kalyanam ◽  
M. Uddin
Keyword(s):  
Brittle Fracture ◽  
Pipe Steels ◽  
Shelf Energy ◽  
Line Pipe ◽  
Pipe Burst ◽  
Sensitivity Studies ◽  
Shear Area ◽  
Fracture Arrest ◽  
Pipeline Design ◽  
Very High

Current line-pipe steels have significantly higher Charpy upper-shelf energy than older steels. Many newer line-pipe steels have Charpy upper-shelf energy in the 300 to 500J range, while older line-pipe steels (pre-1970) had values between 30 and 60J. With this increased Charpy energy comes two different and important aspects of how to predict the brittle fracture arrestability for these new line-pipe steels. The first aspect of concern is that the very high Charpy energy in modern line-pipe steels frequently produces invalid results in the standard pressed-notch DWTT specimen. Various modified DWTT specimens have been used in an attempt to address the deficiencies seen in the PN-DWTT procedure. In examining fracture surfaces of various modified DWTT samples, it has been found that using the steady-state fracture regions with similitude to pipe burst test (regions with constant shear lips) rather than the entire API fracture area, results collapse to one shear area versus temperature curve for all the various DWTT specimens tested. Results for several different materials will be shown. The difficulty with this fracture surface evaluation is that frequently the standard pressed-notch DWTT only gives valid transitional fracture data up to about 20-percent shear area, and then suddenly goes to 100-percent shear area. The second aspect is that with the much higher Charpy energy, the pipe does not need as much shear area to arrest a brittle fracture. Some analyses of past pipe burst tests have been recently shown and some additional cases will be presented. This new brittle fracture arrest criterion means that one does not necessarily have to specify 85-percent shear area in the DWTT all the time, but the shear area needed for brittle fracture arrest depends on the pipeline design conditions (diameter, hoop stress) and the Charpy upper-shelf energy of the steel. Sensitivity studies and examples will be shown.

Acoustic Emission Testing During a Burst Test of a Thick-Walled 2-1/4 Cr-1 Mo Steel Pressure Vessel

1980 ◽  
Vol 102 (4) ◽  
pp. 353-362 ◽  
Author(s):  
T. Tsukikawa ◽  
S. Yamamoto ◽  
Y. Ohshio ◽  
M. Nakano ◽  
H. Ueyama ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Fracture Mechanics ◽  
Pressure Vessel ◽  
Pressure Vessels ◽  
Burst Test ◽  
Test Vessel ◽  
Emission Testing ◽  
Acoustic Emission Testing ◽  
Extensive Program

The applicability of AET to pressure vessels made of 2 1/4 Cr-1 Mo steel was studied by an extensive program which included: 1) a hydrostatic test of a test vessel with weld discontinuities, 2) a burst test of a test vessel with precracks, and 3) an analysis of the results using a fracture mechanics approach. The results obtained clearly demonstrate that AET is a useful tool for shop and in-field inspections.

Control of %age Shear Area in DWTT at Low Temperature in Niobium Microalloyed Line Pipe Steel

2018 ◽  
Author(s):  
Sundaresa Subramanian ◽  
Xiaoping Ma ◽  
Xuelin Wang ◽  
Chengjia Shang ◽  
Xiaobing Zhang ◽  
...  
Keyword(s):  
Low Temperature ◽  
Brittle Fracture ◽  
Cube Texture ◽  
High Angle ◽  
Austenite Grain Size ◽  
Line Pipe ◽  
Nano Scale ◽  
Austenite Grain ◽  
The Matrix ◽  
Shear Area

Microstructural engineering to obtain 100% shear area in DWTT at low temperature requires target parameters to suppress brittle fracture. In-depth characterization of benchmarked steels has confirmed that %age shear area is decreased by high number density of ultra-fine precipitates (<10nm) that contribute to precipitation strengthening, high intensity of rotated cube texture and coarse brittle constituents like M/A or carbides. The control of these parameters by nano-scale precipitate engineering of TiN-NbC was covered in a previous presentation in IPC 2016 [1]. The present paper focuses on crystallographic variants selection that controls the density and dispersion of high angle boundaries, which arrest microcracks to suppress brittle fracture, thereby increasing %age shear area in DWTT at low temperature. Studies on crystallographic variants selection in single undeformed austenite grain have clarified crystallographic variants configuration which gives rise to high angle boundaries is influenced by hardenability parameters, i.e., alloying, cooling rate and austenite grain size. The profound effect of carbon and solute niobium on density and dispersion of high angle boundaries in CGHAZ is demonstrated by analyzing EBSD data to reconstruct the shear transformation of undeformed austenite using K-S relationship. Moreover, pancaking of austenite influences crystallographic variants through Sv factor and dislocation density. Experimental results on nano-scale TiN-NbC composite precipitate engineered steel confirm that adequate solute niobium (>0.03wt%) is retained in the matrix, which is aided by the suppression of delayed strain induced precipitation of ultra-fine precipitates of NbC. The hardenability from solute niobium is found to be adequate to give high density of high angle boundaries to give about 95% shear area in DWTT at −40°C in 32 mm gage K-60 plate and 100% shear area in 16.3 mm X-90 strip. Both steels were processed by nano-scale precipitate engineering of TiN-NbC composite to control size and uniformity of distribution of austenite grains before pancaking.

How New Vintage Line-Pipe Steel Fracture Properties Differ From Old Vintage Line-Pipe Steels

2012 ◽  
Author(s):  
G. Wilkowski ◽  
D.-J. Shim ◽  
Y. Hioe ◽  
S. Kalyanam ◽  
F. Brust
Keyword(s):  
Brittle Fracture ◽  
Fracture Behavior ◽  
Pipe Steel ◽  
Full Scale ◽  
Actual Behavior ◽  
Correction Factors ◽  
Pipe Steels ◽  
Line Pipe ◽  
Line Pipe Steel ◽  
Fracture Control

Newer vintage line-pipe steels, even for lower grades (i.e., X60 to X70) have much different fracture behavior than older line-pipe steels. These differences significantly affect the fracture control aspects for both brittle fracture and ductile fracture of new pipelines. Perhaps one of the most significant effects is with brittle fracture control for new line-pipe steels. From past work brittle fracture control was achieved through the specification of the drop-weight-tear test (DWTT) in API 5L3. With the very high Charpy energy materials that are being made today, brittle fracture will not easily initiate from the pressed notch of the standard DWTT specimen, whereas for older line-pipe steels that was the normal behavior. This behavior is now referred to as “Abnormal Fracture Appearance” (AFA). More recent work shows a more disturbing trend that one can get 100-percent shear area in the standard pressed-notch DWTT specimen, but the material is really susceptible to brittle fracture. This is a related phenomenon due to the high fracture initiation energy in the standard DWTT specimen that we call “Abnormal Fracture Behavior” (AFB). This paper discusses modified DWTT procedures and some full-scale results. The differences in the actual behavior versus the standard DWTT can be significant. Modifications to the API 5L3 test procedure are needed. The second aspect deals with empirical fracture control for unstable ductile fractures based on older line-pipe steel tests initially from tests 30-years ago. As higher-grade line-pipe steels have been developed, a few additional full-scale burst tests have shown that correction factors on the Charpy energy values are needed as the grade increases. Those correction factors from the newer burst tests were subsequently found to be related to relationship of the Charpy energy values to the DWTT energy values, where the DWTT has better similitude than the Charpy test for fracture behavior (other than the transition temperature issue noted above). Once on the upper-shelf, recent data suggest that what was once thought to be a grade correction factor may really be due to steel manufacturing process changes with time that affect even new low-grade steels. Correction factors comparable to that for X100 steels have been indicated to be needed for even X65 grade steels. Hence the past empirical equations in Codes and Standards like B31.8 will significantly under-predict the actual values needed for most new line-pipe steels.

Full Gas Burst Test for HFW Linepipe at Low Temperature

2014 ◽  
Author(s):  
Satoshi Igi ◽  
Satoru Yabumoto ◽  
Masaki Mitsuya ◽  
Yuya Sumikura ◽  
Mikihiro Takeuchi
Keyword(s):  
Residual Stress ◽  
Low Temperature ◽  
Fracture Behavior ◽  
Weld Seam ◽  
Base Material ◽  
Welding Process ◽  
Manufacturing Method ◽  
Burst Test ◽  
Drop Weight Tear Test ◽  
The Difference

A full gas burst test at low temperature below −40°C was performed using a high frequency welded (HFW) linepipe with high-quality weld seam, “MightySeam®,” [1–4] in order to verify the applicability of the Drop Weight Tear Test (DWTT). Residual stress exists in the pipe body of HFW linepipe because the manufacturing method includes a sizing process. Therefore, it is necessary to clarify the difference between the arrestability in the DWTT without residual stress in the specimen and that in the full gas burst test with residual stress in the pipe body. The full gas burst test is performed using a test pipe specimen in which a notch is introduced into the base material by an explosive cutter. In addition, a test pipe specimen with a notch introduced into the weld seam was used in this study because the developed HFW linepipe, “MightySeam®,” has excellent low-temperature toughness as a result of control of the morphology and distribution of oxides generated in the welding process by temperature and deformation distribution control. The Charpy transition temperature of “Mighty Seam®” was much lower than −45 °C. Ductile cracks were initiated from the initial explosive notch, and these cracks were arrested after ductile crack propagation of about 1 m in base material on both sides. The fracture behavior was similar in appearance in the DWTT without residual stress and the full gas burst test with residual stress.

scholarly journals EFFECT OF QUENCHING AND TEMPERING PROCESS ON A MEDIUM C STEEL WITH LOW CHROMIUM AND MOLYBENUM ADDITION FOR FORGED COMPONENTS

2018 ◽  
Vol 24 (2) ◽  
pp. 112 ◽  
Author(s):  
Giusepe Napoli ◽  
Giulia Fabrizi ◽  
Riccardo Rufini ◽  
Sabrina Mengaroni ◽  
Andrea Di Schino
Keyword(s):  
Mechanical Properties ◽  
Transition Temperature ◽  
Thermal Treatment ◽  
Low Temperature ◽  
Impact Test ◽  
Fracture Appearance Transition Temperature ◽  
Fracture Appearance ◽  
Temperature Application ◽  
Mn Steel ◽  
Quenching And Tempering

<p class="AMSmaintext"><span lang="EN-GB">In this paper the effect of quenching and tempering (Q&amp;T) thermal treatment on mechanical properties of a C-Mn steel with 0.22% Cr for forged components is studied. Due to the lack od any micro-alloying elements (such as vanadium or niobium) such steel can just reach mechanical target allowed by its intrinsic hardenability. Aim of this work is to evaluate the mechanical properties dependence as a function of different quenching and tempering treatments. Results show that, after Q&amp;T, steel can reach a yield strength of 330 MPa combined with a -20°C </span><span lang="EN-GB">fracture appearance transition temperature (50% FATT) measured with a Charpy-V impact test making this steel suitable for low temperature application.</span></p>

Analysis of Full-Scale Burst Test Data by Examining Effects of Insulation and Using Fully-Instrumented Standard Pressed-Notch and Modified Backslot DWTT Specimens

2018 ◽  
Author(s):  
M. Uddin ◽  
G. Wilkowski ◽  
C. Guan
Keyword(s):  
Ductile Fracture ◽  
Fracture Behavior ◽  
Large Diameter ◽  
Test Site ◽  
Radial Clearance ◽  
High Water Content ◽  
Burst Test ◽  
Pipe Burst ◽  
Service Conditions ◽  
Arrest Toughness

An intensive effort was undertaken to understand the fracture behavior in a recent TCPL pipe burst test. The 48-inch diameter X80 pipe was buried in soil at the Spadeadam Test Site, but since it was desired to have the gas and pipe cooled to the minimum service conditions of −5°C, a 50-mm thick polyurethane foam (PUF) insulation was sprayed on the entire pipe test section. This was a reasonable precaution since freezing of a high water content soil around a large-diameter pipe burst test can require significant cooling capacity or a much longer duration to get to the burst test conditions. In this burst test, the crack propagated much farther than anticipated by traditional predictive approaches such as using Charpy energy to predict the minimum ductile fracture arrest toughness, assuming that soil backfill conditions existed. To explore this burst test behavior, two aspects were examined. The first was an assessment of the properties of the PUF insulation relative to the soil properties, and the second was the toughness evaluated by instrumented DWTT testing. The 50-mm thickness of the PUF insulation corresponded to about 8.3% of the pipe radius. In past loose-fitting steel sleeve crack arrestor burst tests, if the radial clearance was greater than 5.5% of the pipe, then a ductile fracture propagated under the arrestor regardless of its length with no change in speed. Hence if the PUF could be easily compressed, then the pipe in this burst test would behave as if it was in a non-backfilled condition. Non-backfilled pipe requires much higher toughness to arrest a ductile fracture. So perhaps the pipe in this burst test condition acted somewhere between non-backfilled and backfilled conditions — an aspect that might need a much more comprehensive computational model to better assess. Additionally to assess how material toughness played a role in this burst test, detailed instrumented toughness testing was conducted on material taken from several of the pipe lengths in the burst test. The evaluations of the Charpy energy to the DWTT energy suggested that one of the pipe materials may have behaved more like an X100 steel than an X80 steel. Correction factors on the predicted arrest toughness are well known to be needed for the Battelle Two Curve method (BTCM) when applied to X80 and X100 pipes. However, even with these corrections on the Charpy energy, arrest was predicted with soil backfill in several cases where in the actual test, the crack propagated through the pipes. Hence toughness corrections by themselves did not explain the test results. Additional calculations were then done assuming a non-backfilled condition (as suggested from the PUF property evaluation) along with the appropriate grade effect correction from the DWTT testing, and propagation was properly predicted in each case consistently with the burst test. So the fracture behavior in this burst test was somewhere between those of backfilled and non-backfilled pipe. As a result of this investigation it appears that the PUF insulation played an important role in crack arrest behavior, and because of its presence may have required much higher toughness than was actually needed for the actual service conditions of pipe buried in actual soil backfill.

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