Crack Arrest Toughness of a Heat-Affected Zone Containing Local Brittle Zones

1996 ◽  
Vol 118 (4) ◽  
pp. 292-299 ◽  
Author(s):  
L. Malik ◽  
L. N. Pussegoda ◽  
B. A. Graville ◽  
W. R. Tyson
Keyword(s):  
Crack Initiation ◽  
Base Metal ◽  
Heat Affected Zone ◽  
Weld Zone ◽  
Crack Arrest ◽  
Attractive Alternative ◽  
Initiation Toughness ◽  
Fusion Boundary ◽  
Arrest Toughness ◽  
Fast Fracture

The awareness of the presence of local brittle zones (LBZs) in the heat-affected zone (HAZ) of welds has led to the requirements for minimum initiation (CTOD) toughness for the HAZ for critical applications (API RP 2Z, CSA S473). Such an approach, however, is expensive to implement and limits the number of potential steel suppliers. A fracture control philosophy that is proposed to be an attractive alternative for heat-affected zones containing LBZs is the prevention of crack propagation rather than of crack initiation. Such an approach would be viable if it could be demonstrated that cracks initiated in the LBZs will be arrested without causing catastrophic failure, notwithstanding the low initiation (CTOD) toughness resulting from the presence of LBZs. Unstable propagation of a crack initiating from an LBZ requires the rupture of tougher microstructural regions surrounding the LBZ in HAZ, and therefore the CTOD value reflecting the presence of LBZ is unlikely to provide a true indication of the potential for fast fracture along the heat-affected zone. Base metal specifications (CSA S473) usually ensure that small unstable cracks propagating from the weld zone into the base metal would be arrested. Past work has also shown that unstable crack initiation resulting from interaction of surface semi-elliptical cracks parallel to the fusion boundary with the local brittle zones can get arrested once the crack has popped through the depth of the LBZ. However, the potential for arrest when a through-thickness HAZ crack runs parallel to the fusion boundary, and thus parallel to the LBZs, has not been examined previously. To investigate the likelihood of fast fracture within the HAZ, a test program has been carried out that involved performing compact plane strain (ASTM E1221) and plane stress crack arrest tests on a heataffected zone that contained LBZs, and thus exhibited unacceptable low CTOD toughness for resistance to brittle fracture initiation. The results indicated that in contrast to the initiation toughness (CTOD toughness), the crack arrest toughness was little influenced by the presence of local brittle zones. Instead, the superior toughness of the larger proportion of finer-grain HAZ surrounding the LBZ present along the crack path has a greater influence on the crack arrest toughness. It further seems that there may be potential to estimate the HAZ crack arrest toughness from more conventional smaller-scale laboratory tests, such as conventional or precracked instrumented Charpy impact tests.

The Interrelationships of KIa, KIc, and JIc, and the Implications of These Relationships on Use of Fracture Models Over the Ranges of Hardening Observed in Ferritic Steels

2006 ◽  
Author(s):  
Marjorie EricksonKirk ◽  
Mark EricksonKirk ◽  
Tim Williams
Keyword(s):  
Fracture Toughness ◽  
Crack Initiation ◽  
Master Curve ◽  
Crack Arrest ◽  
Nuclear Industry ◽  
Ferritic Steels ◽  
Initiation Toughness ◽  
Cleavage Crack ◽  
The Mean ◽  
Arrest Toughness

Models to predict the fracture and arrest behavior of ferritic steels, particularly those in use in the nuclear industry, have long been under development. The current, most widely accepted model of fracture toughness behavior is the ASTM E1921-02 “Master Curve” that is used to predict the variation of the mean cleavage fracture toughness with temperature in the transition temperature region as well as predicting the scatter of data about the mean at any given temperature. Recently, models describing the variation of arrest fracture toughness and of ductile initiation toughness with temperature have also been proposed. A study has been conducted with the goal of assessing how the scatter in cleavage initiation toughness may vary with temperature and level of irradiation embrittlement, which utilizes the crack arrest and ductile crack initiation models to redefine limits of applicability of the Master Curve-assumed Weibull distribution by developing empirically-derived interrelationships between the three models. These relationships are expected as all three parameters, KIc, KIa, and JIc, are controlled by the flow behavior of the material. There is a physical basis for viewing the crack arrest toughness as an absolute lower bound to the distribution of crack initiation toughness values for a fixed material condition and temperature. This physically based relationship, borne of the fact that both cleavage crack initiation toughness and cleavage crack arrest toughness are controlled by dislocation mobility, has brought about the suggestion that crack arrest toughness could be used to modify the lower tails of the crack initiation fracture toughness distribution. Using both empirical evidence and a hardening model proposed by Natishan and Wagenhofer, we investigate the relationship between initiation and arrest toughness and the implications on use of toughness models.

Crack-initiation toughness and crack-arrest toughness in advanced 9 pct Ni steel welds containing local brittle zones

2002 ◽  
Vol 33 (8) ◽  
pp. 2615-2622 ◽  
Author(s):  
Jae-Il Jang ◽  
Baik-Woo Lee ◽  
Jang-Bog Ju ◽  
Dongil Kwon ◽  
Woo-Sik Kim
Keyword(s):  
Crack Initiation ◽  
Crack Arrest ◽  
Initiation Toughness ◽  
Steel Welds ◽  
Arrest Toughness

scholarly journals Weld Formation in Laser Hot-Wire Welding of 7075 Aluminum Alloy

Metals ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 909 ◽  
Author(s):  
Shichun Li ◽  
Wei Xu ◽  
Gang Xiao ◽  
Bing Chen
Keyword(s):  
Aluminum Alloy ◽  
Base Metal ◽  
Heat Affected Zone ◽  
Weld Zone ◽  
Welding Process ◽  
Tensile Fracture ◽  
Hot Wire ◽  
Columnar Crystal ◽  
Weld Formation ◽  
Hot Wire Welding

The laser hot-wire welding process was adopted to weld 7075 high-strength aluminum alloy. The influence laws of parameters on the weld formation were analyzed during laser hot-wire welding, and the microstructure characteristics and mechanical properties of welds were analyzed. The results showed that the parameters whose significance of influence on weld formation as ranked from high to low were laser power, current, gap width, welding speed and wire feeding rate. With the increase of wire temperature, the weld formation quality became better initially and then worse. Under the condition of optimized parameters, good weld formation could be obtained. The weld zone had a fine grain microstructure, and was in casting state consisted of dendritic crystal and equiaxed crystal. The heat affected zone mainly consisted of columnar crystal. The microhardness decreased gradually from base metal to heat affected zone then to weld zone. The tensile fracture of weld specimen occurred at the weld zone, and was in the ductile fracture state. The tensile strength of weld joint was 206 MPa and was 64.2% of base metal strength.

Characterization of the Microstructure and Toughness of DSAW and ERW Seam Welds of Older Linepipe Steels

2002 ◽  
Author(s):  
J. A. Gianetto ◽  
D. K. Mak ◽  
R. Bouchard ◽  
S. Xu ◽  
W. R. Tyson
Keyword(s):  
Weld Metal ◽  
Base Metal ◽  
Heat Affected Zone ◽  
Electrical Resistance ◽  
Crack Tip ◽  
Charpy Impact ◽  
Initiation Toughness ◽  
J Integral ◽  
Crack Tip Opening Displacement ◽  
Linepipe Steel

The aim of the present work is to quantify the seam weld properties, including both weld metal and heat affected zone regions, for a series of double-submerged-arc welded pipe, and the base metal and bondline regions for an electrical resistance welded linepipe steel. The chemical composition, microstructure, microhardness, tensile properties, Charpy impact toughness and J-integral/crack-tip opening displacement fracture resistance were characterized for linepipe produced between 1953 and 1981. The toughness results of the base metal, heat affected zone and weld metal regions of the older (higher carbon) linepipes were significantly poorer than those obtained for a more modern low-C microalloyed linepipe steel. In the latter case the base metal, HAZ and weld metal regions failed by ductile fracture at room temperature in both fracture toughness (quasi-static) and Charpy impact tests. It was possible to show that there is a linear correlation between the J-integral at 0.2 mm crack growth and the upper shelf Charpy energy. It is, however, important to note that the Charpy transition temperatures of the older pipes are considerably higher than for the modern pipe. In the case of the electrical resistance weld, very poor toughness was observed for the bondline. Fracture occurred along the bondline in a brittle mode (cleavage) that was attributed to the formation of a coarse, relatively hard microstructure and the presence of inclusions along the bondline region. In addition, it was shown using base-metal BxB and Bx2B samples that initiation toughness is a function of the remaining uncracked ligament. This emphasizes the necessity of ensuring that the crack-tip constraint in the test specimens is similar to the constraint in the crack geometry being assessed.

Characterisation of Microstructure, Mechanical Properties and Corrosion Behaviour on GTA Welded AISI 310 and Inconel 800

2011 ◽  
Vol 383-390 ◽  
pp. 5863-5868 ◽  
Author(s):  
B.K. Yeshwanth ◽  
S. Senthil Kumar ◽  
B. Hafeez Sharief ◽  
K. Devendranath Ramkumar ◽  
S. Narayanan ◽  
...  
Keyword(s):  
Molten Salt ◽  
Base Metal ◽  
Heat Affected Zone ◽  
Corrosion Behaviour ◽  
Weld Zone ◽  
Gta Welding ◽  
Weld Interface ◽  
Considerable Change ◽  
Inconel 600 ◽  
Inconel 800

The current work was carried out to characterize the welding of austenitic stainless steel AISI 310 steel to Inconel 800 alloys by Gas Tungsten Arc (GTA) welding using Inconel 600 filler wire. Tensile test shows that failure has occurred in heat affected zone of AISI 310 and its strength was lower as compared to the base metal. In addition the SEM fractographs showed the micro void with some dimple structure which ensures the fracture is ductile in nature. Furthermore the maximum hardness value was found at the weld interface of AISI310 due to the formation of chromium-carbide. The microstructure revealed a considerable change in the grain size and orientation of the Heat Affected Zone (HAZ) in both sides of the weldment than that of the parent metal. Moreover the corrosion test was also carried out in the welded samples both in air and molten salt of Na2SO4 – 50%NaCl at 700 °C. The weld zone corroded less readily in the air and molten salt than that of the base metal. It can be concluded that these joints could be used effectively at aggressive environments without compromising the strength.

Correlation Between Steel Microstructural Characteristics and the Initiation and Arrest Toughness Determined From Small-Scale Mechanical Testing

2019 ◽  
Author(s):  
Jessica Taylor ◽  
Philippa Moore ◽  
Ali Mehmanparast ◽  
Rob Kulka
Keyword(s):  
Fracture Toughness ◽  
Mechanical Test ◽  
Pipeline Steel ◽  
Crack Arrest ◽  
Carbon Steels ◽  
Small Scale ◽  
Initiation Toughness ◽  
Microstructural Characteristics ◽  
Average Grain Size ◽  
Arrest Toughness

Abstract Modern high Charpy toughness steels can nonetheless show low crack arrest toughness[1]. In this paper, the relationship between initiation and arrest toughness is investigated in five different carbon steels, including S355 structural steels, X65 pipeline steel, and high strength reactor pressure vessel, RPV, steels. The results from small-scale mechanical tests, including instrumented Charpy, drop weight Pellini, fracture toughness, and tensile testing (including STRA in the through-thickness direction) were used to determine the behaviour of the different steels in terms of initiation fracture toughness and crack arrest toughness parameters. There was no correlation between the upper shelf initiation toughness and the arrest toughness when the results from the five steels were collated. The mechanical test results were then correlated to the steels’ microstructural characteristics, including parent metal microstructure, average grain size and grain aspect ratio to identify the relative roles of microstructure and texture in the fracture initiation and arrest performance of carbon steels.

A Crack Arrest Test Using a Toughness Gradient Steel Plate

1995 ◽  
Vol 117 (4) ◽  
pp. 330-334 ◽  
Author(s):  
H. Okamura ◽  
G. Yagawa ◽  
T. Hidaka ◽  
Y. Urabe ◽  
M. Satoh ◽  
...  
Keyword(s):  
Crack Initiation ◽  
Steel Plate ◽  
Crack Arrest ◽  
Steel Plates ◽  
Brittle Crack ◽  
Four Point Bending ◽  
Heavy Section ◽  
Bending Load ◽  
Plate Specimen ◽  
Arrest Toughness

A crack arrest test was carried out using a toughness gradient steel plate with three layers to study the concept of crack arrest toughness. Four-point bending load with thermal shock was applied to the large flat plate specimen with a surface crack. Five crack initiations and arrests were observed during the test and the propagated crack bifurcated. Finally, cracks were arrested at the boundary of the first and the second layer, except for a small segment of the crack. The first crack initiation took place slightly higher than the lower bound of KIc data obtained by ITCT specimens. That is, the KIC concept for brittle crack initiation was verified for heavy section steel plates. The first crack arrest took place within the scatter band of KIa and KId data for the first layer. That is, the KIa concept appears applicable for crack arrest of a short crack jump.

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