Effect of prior creep cavitation on brittle fracture in heat affected zone of ferritic steel weldments

2002 ◽  
Vol 18 (11) ◽  
pp. 1329-1334 ◽  
Author(s):  
G. E. Smith ◽  
A. G. Crocker ◽  
P. E. J. Flewitt ◽  
R. Moskovic
Keyword(s):  
Brittle Fracture ◽  
Heat Affected Zone ◽  
Ferritic Steel ◽  
Creep Cavitation

Prediction of Brittle Fracture Under Generalised Elastic Plastic Loading

2008 ◽  
Author(s):  
S. J. Lewis ◽  
C. E. Truman ◽  
D. J. Smith
Keyword(s):  
Fracture Mechanics ◽  
Brittle Fracture ◽  
Ferritic Steel ◽  
Failure Prediction ◽  
J Integral ◽  
Local Approach ◽  
Elastic Plastic ◽  
Failure Data ◽  
Stress States ◽  
Plastic Loading

This article describes an investigation into the ability of a number of different fracture mechanics approaches to predict failure by brittle fracture under general elastic/plastic loading. Data obtained from C(T) specimens of A508 ferritic steel subjected to warm pre-stressing and side punching were chosen as such prior loadings produce considerably non-proportionality in the resulting stress states. In addition, failure data from a number of round notched bar specimens of A508 steel were considered for failure with and without prior loading. Failure prediction, based on calibration to specimens in the as received state, was undertaken using two methods based on the J integral and two based on local approach methodologies.

Prediction of the Absence of Brittle Failure Risk for Ferritic Steel Piping Components in the Brittle-Ductile Region

2011 ◽  
Author(s):  
S. Marie ◽  
J. Schwab ◽  
S. Vidard
Keyword(s):  
Brittle Fracture ◽  
Fracture Risk ◽  
Brittle Failure ◽  
Risk Evaluation ◽  
Critical Stress ◽  
Ferritic Steel ◽  
Loading Condition ◽  
Maximum Principal Stress ◽  
Fracture Transition ◽  
Secondary Loop

This paper deals with the brittle fracture risk evaluation for a C-Mn piping component in the upper shelf of the brittle to ductile fracture transition temperature range, with the main objective to validate a predictive criteria, able to demonstrate the complete absence of brittle fracture risk. The criteria is based one a critical stress and the volume around the crack were the maximum principal stress exceed this critical stress. The model is calibrated on notched tensile specimens and CT specimens. A four-points bending pipe test has then been designed using this criterion to insure that no brittle fracture will occurs at a temperature that all CT specimens failed by cleavage. The material is a French secondary loop Tu42C ferritic steel and the pipe dimensions for the test are the same than the size of the principal secondary loop pipes. The results of the pipe test confirm the prediction with the model and the interpretation lead to define an equivalence between the loading conditions (based on the J parameter) of the pipe and the loading condition of a CT specimen.

Characterisation of Microstructure and Properties of a Transition Weld

2016 ◽  
Author(s):  
W. J. Brayshaw ◽  
A. H. Sherry ◽  
M. G. Burke ◽  
P. James
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Heat Affected Zone ◽  
Ferritic Steel ◽  
Image Correlation ◽  
Micro Hardness ◽  
Flow Properties ◽  
Material Interfaces ◽  
Local Composition ◽  
Microstructure And Properties

Transition welds represent a challenge for the assessment of structural integrity of nuclear plant due to the complexity of the microstructure, properties and local stress state. This paper presents the initial findings of a study aimed at characterising the local microstructure and properties of a transition weld between SA508-4N ferritic steel and SS316LN austenitic stainless steel using a nickel-base filler of Alloy 82. The local microstructures and local composition of the material interfaces are characterised using backscattered electron imaging and Energy-dispersive X-ray spectroscopy. The ferritic steel shows significant grain refinement in the heat affected zone compared to the base metal. This refinement is also observed in the heat affected zone of the austenitic stainless steel although not as significant. Micro-hardness testing has also been incorporated to provide an indication of the influence of local microstructure on flow properties across the weld region. The results indicate a hardness range of between 180–340HV across the weld with the highest value in the heat affected zone of the ferritic steel and the lowest in the austenitic stainless steel. Yield and flow properties derived from flat transweld tensile tests incorporating digital image correlation are related to the micro-hardness results and microstructural characterisation, and an initial assessment of the fracture mechanism performed using fractography.

Assessing the Effect of Intrinsic Microscale Heterogeneity on Brittle Fracture of a Ferritic Steel

2007 ◽  
Author(s):  
Xinglong Zhao ◽  
David Lidbury ◽  
Joa˜o Quinta da Fonseca ◽  
Andrew Sherry
Keyword(s):  
Fracture Mechanics ◽  
Brittle Fracture ◽  
Cleavage Fracture ◽  
Ferritic Steel ◽  
Plastic Anisotropy ◽  
Fracture Probability ◽  
Local Approach ◽  
Transition Range ◽  
Micro Scale ◽  
Scale Heterogeneity

Brittle fracture can have potentially catastrophic consequences on the safety and integrity of engineering components. For this reason, the accurate prediction of cleavage failure probability is of importance in assessing the defect tolerance of high-integrity ferritic steel components, given the possibility of operation in the presence of significant loads at temperatures in the ductile-brittle transition range. In current safety assessments, fracture mechanics treats polycrystalline steels as homogeneous continua. In reality, deformation is heterogeneous, due to the elastic and plastic anisotropy of their constituent (often randomly orientated) grains. Heterogeneity at the micro (grain) scale is currently not considered by conventional fracture mechanics. This paper describes the initial results of a programme of work on a 22NiMoCr37 steel forging to assess the effect of micro-scale heterogeneity on cleavage fracture probability using an adaptation of the Beremin local approach model. The results of cleavage fracture modelling allowing for the effects of micro-scale heterogeneity are compared with the results of modelling based on the assumption of homogeneous materials behaviour. Application of the micro-scale heterogeneity model is providing some new insights into the prediction of cleavage fracture probability.

Quantification of Creep Cavitation in Welded Joint and Evaluation of Material Characteristics of Simulated Heat-Affected Zone in X 20 CrMoV 12 1 Steel

2000 ◽  
Vol 123 (1) ◽  
pp. 112-117 ◽  
Author(s):  
Yong-Keun Chung ◽  
Cheol-Hong Joo ◽  
Jong-Jin Park ◽  
Ik-Man Park ◽  
Hyo-Jin Kim
Keyword(s):  
Base Metal ◽  
Heat Affected Zone ◽  
Power Plants ◽  
Welded Joint ◽  
Charpy Impact ◽  
Creep Damage ◽  
Average Diameter ◽  
Damage Mechanism ◽  
Creep Rupture ◽  
Creep Cavitation

X 20 CrMoV 12 1(DIN 17 175) steel has been used for components subjected to high temperature in power plants and chemical and petroleum industries. Therefore, extensive studies have been made on this steel. However, these studies focused mainly on the base metal, and few studies on the welded joint have been reported. Actually, a large number of failures have occurred at the welded joint, so there is increasing need to investigate the characteristics of X 20 CrMoV 12 1 weldment. In this study, the interrupted and creep rupture tests were carried out and quantification of the creep damage was attempted for the X 20 CrMoV 12 1 welded joint. The interrupted and creep rupture tests were performed at four conditions\M650-60, 600-100, 600-120, and 575-150(|SDC-MPa)\Mon the X 20 CrMoV 12 1 welded joint specimens, respectively. It was revealed from the experimental results that creep damage mechanism of a welded joint was mainly creep cavitation, and that the intensively damaged area by creep cavitations was the transition region from fine-grained heat-affected zone (HAZ) to unaffected base metal, namely intercritical HAZ. For both the interrupted and ruptured specimens, quantification of creep damage was attempted by evaluating cavitated area fraction, average diameter, and the number of cavities with creep life fraction. In addition, on the basis of the heat input during the welding, microstructure, microhardness, and grain size of the actual intercritical HAZ, simulated HAZ was made in order to evaluate its material properties. For the simulated HAZ specimens, tensile, charpy impact, and creep rupture tests were carried out. As a result, yield, tensile strength, and elongation of simulated HAZ were similar to those of base metal, respectively, and impact property of simulated HAZ was slightly above base metal. Also, it was found that creep strength of simulated HAZ was inferior to that of the base metal.

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