scholarly journals Influence of Effective Grain Size on Low Temperature Toughness of High-Strength Pipeline Steel

Materials ◽  
2019 ◽  
Vol 12 (22) ◽  
pp. 3672 ◽  
Author(s):  
Yanlong Niu ◽  
Shujun Jia ◽  
Qingyou Liu ◽  
Shuai Tong ◽  
Ba Li ◽  
...  
Keyword(s):  
Grain Size ◽  
Grain Boundaries ◽  
Pipeline Steel ◽  
Rolling Direction ◽  
Charpy Impact ◽  
High Strength ◽  
Cleavage Crack ◽  
Electron Backscattered Diffraction ◽  
Effective Grain Size ◽  
Misorientation Angles

In this study, the series temperature Charpy impact and drop-weight tear test (DWTT) were investigated, the misorientation angles among structural boundaries where the cleavage crack propagated were identified, and angles of {100} cleavage planes between adjacent grains along the cleavage crack propagated path were calculated in five directions (0°, 30°, 45°, 60°, and 90° to the rolling direction) of high-grade pipeline steel. Furthermore, the effective grain size (grain with misorientation angles greater than 15°) was redefined, and the quantitative influences of the redefined effective grain size on Charpy impact and DWTT is also discussed synthetically. The results showed that the microstructure presented a typical acicular ferrite characteristic with some polygonal ferrite and M-A islands (composed of martensite and retained austenite), and the distribution of the high-angle grain boundaries were mainly distributed in the range of 45°–65° in different directions. The Charpy impact energy and percent shear area of DWTT in the five directions increased with refinement of the redefined effective grain size, composed of grains with {100} cleavage planes less than 35° between grain boundaries. The ductile-to-brittle transition temperature also decreased with the refining of the redefined effective grain size. The redefined effective grain boundaries can strongly hinder fracture propagation through electron backscattered diffraction analysis of the cleavage crack path, and thus redefined effective grain can act as the effective microstructure unit for cleavage.

Study on Mechanical Properties Anisotropy of X80 Pipeline Steel

2013 ◽  
Vol 803 ◽  
pp. 413-418
Author(s):  
Qiang Duan ◽  
Jun Yan ◽  
Guo Hui Zhu ◽  
Qing Wu Cai
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Impact Toughness ◽  
Crack Propagation ◽  
Grain Boundaries ◽  
Pipeline Steel ◽  
Rolling Direction ◽  
High Angle ◽  
X80 Pipeline Steel ◽  
Effective Grain Size

The microstructure of X80 pipeline steel in different directions were observed by SEM technique and its effective grain size and misorientation were statistically analyzed by EBSD system. Based on these results, the mechanical properties at 0°, 45° and 90° to the rolling direction of X80 pipeline steel were studied. The results show that, owing to finer grain size and less low-angle grain boundaries, strengths and impact toughness of X80 pipeline steel at 90° direction are optimal. While the pipeline steel possesses finer grain size, more high-angle grain boundaries and less low-angle grain boundaries, the crack propagation is effectively suppressed, then its impact toughness is improved.

Effects of Low-Angle Grain Boundaries on the Yield-Strength Ratio of High Grade Pipeline Steels

2010 ◽  
Vol 168-170 ◽  
pp. 1581-1585 ◽  
Author(s):  
Dong Ying Xu ◽  
Hao Yu
Keyword(s):  
Grain Size ◽  
Tensile Strength ◽  
Yield Strength ◽  
Grain Boundaries ◽  
Pipeline Steel ◽  
High Grade ◽  
Strength Ratio ◽  
Pipeline Steels ◽  
Effective Grain Size ◽  
Electron Back Scattered Diffraction

Orientations distribution between grains of two high grade pipeline steels were investigated by electron back-scattered diffraction (EBSD). Then the percentage of low-angle grain boundaries was studied qualitatively to analyze the effect of low-angle grain boundaries on the yield-strength ratio of high grade pipeline steels. From the mode of coordinate deformation and the ability to resist deformation by the grain boundaries, the results show that when the effective grain size are almost the same, the pipeline steel which has the smaller percentage of low-angle grain boundaries, the larger difference between the yield strength and tensile strength, which makes the yield-strength ratio of pipeline steel lower.

Microstructure - Texture Related Toughness Anisotropy of API-X80 Pipeline Steel Characterized by Means of 3D-EBSD Technique

2007 ◽  
Vol 558-559 ◽  
pp. 1429-1434 ◽  
Author(s):  
Roumen H. Petrov ◽  
Orlando León García ◽  
Nuria Sánchez Mouriño ◽  
Leo Kestens ◽  
Jin Ho Bae ◽  
...  
Keyword(s):  
Grain Shape ◽  
Pipeline Steel ◽  
Rolling Direction ◽  
Charpy Impact ◽  
Shape Reconstruction ◽  
Rolled Plate ◽  
X80 Pipeline Steel ◽  
Standard Size ◽  
Industrial Grade ◽  
Ebsd Technique

The variations of in plane Charpy toughness anisotropy as a function of the microstructure and texture of an industrial grade of API –X80 pipeline steel was studied. Standard size Charpy samples with a long axis orientated at 0, 22.5, 45, 67.5 and 90° with respect to the rolling direction of the plate were tested at different temperatures varying from -196°C to 20°C. Microstructure and texture of the plates were investigated by means of electron backscattering diffraction (EBSD), XRD and the recently developed 3D EBSD technique. The spatial grain shape orientation distribution was examined on samples which were cut from the middle thickness of an industrial rolled plate by means of 3D EBSD and following grain shape reconstruction and approximation of the grain shape with ellipsoids. It was found that the experimentally observed 3D microstructures could well be correlated to the anisotropy of the measured Charpy impact toughness of the steel for the Charpy samples. The Charpy toughness anisotropy of the plates in the transition region where both ductile and brittle fractures take place can be related to the microstructural anisotropy characterized by the grain shape orientation and the spatial distribution of the 2nd phase.

scholarly journals A Unified Model for Plasticity in Ferritic, Martensitic and Dual-Phase Steels

Metals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 764
Author(s):  
Shuntaro Matsuyama ◽  
Enrique I. Galindo-Nava
Keyword(s):  
Grain Size ◽  
Dislocation Density ◽  
Carbon Content ◽  
Grain Boundaries ◽  
Uniform Elongation ◽  
High Strength Steels ◽  
High Strength ◽  
Dual Phase ◽  
Dual Phase Steels ◽  
Dislocation Generation

Unified equations for the relationships among dislocation density, carbon content and grain size in ferritic, martensitic and dual-phase steels are presented. Advanced high-strength steels have been developed to meet targets of improved strength and formability in the automotive industry, where combined properties are achieved by tailoring complex microstructures. Specifically, in dual-phase (DP) steels, martensite with high strength and poor ductility reinforces steel, whereas ferrite with high ductility and low strength maintains steel’s formability. To further optimise DP steel’s performance, detailed understanding is required of how carbon content and initial microstructure affect deformation and damage in multi-phase alloys. Therefore, we derive modified versions of the Kocks–Mecking model describing the evolution of the dislocation density. The coefficient controlling dislocation generation is obtained by estimating the strain increments produced by dislocations pinning at other dislocations, solute atoms and grain boundaries; such increments are obtained by comparing the energy required to form dislocation dipoles, Cottrell atmospheres and pile-ups at grain boundaries, respectively, against the energy required for a dislocation to form and glide. Further analysis is made on how thermal activation affects the efficiency of different obstacles to pin dislocations to obtain the dislocation recovery rate. The results are validated against ferritic, martensitic and dual-phase steels showing good accuracy. The outputs are then employed to suggest optimal carbon and grain size combinations in ferrite and martensite to achieve highest uniform elongation in single- and dual-phase steels. The models are also combined with finite-element simulations to understand the effect of microstructure and composition on plastic localisation at the ferrite/martensite interface to design microstructures in dual-phase steels for improved ductility.

Fracture and Crack Propagation Behavior of 560 MPa Microalloyed Pipeline Steel under Different Cooling Schedules

2017 ◽  
Vol 898 ◽  
pp. 1094-1102 ◽  
Author(s):  
Jin Hua Zhao ◽  
Dong Fang Li ◽  
Guo Yuan ◽  
Xue Qiang Wang ◽  
Rui Hao Li ◽  
...  
Keyword(s):  
Grain Size ◽  
Low Temperature ◽  
Crack Propagation ◽  
Pipeline Steel ◽  
Crack Arrest ◽  
Dominant Factor ◽  
Cooling Schedules ◽  
Effective Grain Size ◽  
Mixed Microstructure ◽  
Low Temperature Toughness

Three kinds of pipeline steel with different microstructures were fabricated by varying cooling schedules during thermo-mechanical controlled processing (TMCP). Charpy impact property of the pipeline steels were obtained, and the fracture and crack-arrest mechanisms were further studied. The results indicated that the steels were classified into two kinds according to their microstructures, the mixture of acicular ferrite (AF), quasi-polygonal ferrite (QF), granular bainite (GB) and small fraction of degenerate pearlite (DP), and the mixed microstructure of AF and GB, respectively. The processed steel with microstructure of AF and GB exhibited more excellent low-temperature toughness and crack-arrest properties with upper shelf energy of ~281 J and energy transition temperature of ~-76°C. The mixed microstructure (AF + GB) possessing smaller effective grain size hindered the propagating of crack and consumed large amount of energy during fracture. The effective grain size of microstructure was the dominant factor controlling low-temperature toughness and crack-arrest properties of pipeline steel, which increased the high-angle boundary length per unit area and further increased the crack propagation energy during fracture.

Characterization of Zinalco Alloy Superplastically Deformed Using Orientation Imaging Microscopy

2009 ◽  
Vol 1242 ◽  
Author(s):  
Ramos A. Mitsuo ◽  
Martínez F. Elizabeth ◽  
Negrete S. Jesús ◽  
Torres-Villaseñor G.
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Superplastic Deformation ◽  
Orientation Imaging Microscopy ◽  
Grain Boundary Sliding ◽  
Boundary Misorientation ◽  
Average Grain Size ◽  
Grain Boundary Misorientation ◽  
Misorientation Angles

ABSTRACTZinalco alloy (Zn-21mass%Al-2mass%Cu) specimens were deformed superplastically with a strain rate (ε) of 1×10-3 s-1 at homologous temperature (TH) of 0.68 (5 ). It was observed neck formation that indicate nonhomegeneus deformation. Grain size and grain boundaries misorientation changes, due superplastic deformation, were characterized by Orientation Imagining Microscopy (OIM) technique. It was studied three regions in deformed specimens and the results were compared with the results for a specimen without deformation. Average grain size of 1 mm was observed in non-deformed specimen and a fraction of 82% for grain boundary misorientation angles with a grain boundaries angles between 15° and 55° was found. For deformed specimen, the fraction of angles between 15° and 55° was decreced to average value of 75% and fractions of low angle (<5°) and high angle (>55°) misorientations were 10% and 15% respectively. The grain size and high fraction of grain boundary misorientation angles between 15° and 55° observed in the alloy without deformation, are favorable for grain rotation and grain boundary sliding (GBS) procces. The changes observed in the fraction of favorable grain boundary angles during superplastic deformation, shown that the superplastic capacity of Zinalco was reduced with the deformation.

scholarly journals Effective grain size and charpy impact properties of high-toughness X70 pipeline steels

2005 ◽  
Vol 36 (8) ◽  
pp. 2107-2114 ◽  
Author(s):  
Byoungchul Hwang ◽  
Yang Gon Kim ◽  
Sunghak Lee ◽  
Young Min Kim ◽  
Nack J. Kim ◽  
...  
Keyword(s):  
Grain Size ◽  
Charpy Impact ◽  
Pipeline Steels ◽  
Impact Properties ◽  
High Toughness ◽  
Effective Grain Size

scholarly journals Toughness and Effective Grain Size in Heat-Treated Low-Alloy High Strength Steels

1972 ◽  
Vol 12 (5) ◽  
pp. 325-333 ◽  
Author(s):  
Shōichi MATSUDA ◽  
Tohru INOUE ◽  
Hiroshi MIMURA ◽  
Yoshihiro OKAMURA
Keyword(s):  
Grain Size ◽  
High Strength Steels ◽  
High Strength ◽  
Heat Treated ◽  
Effective Grain Size

Role of Delamination Fracture for Enhanced Impact Toughness in 0.05 %P Doped High Strength Steel with Ultrafine Elongated Grain Structure

2011 ◽  
Vol 409 ◽  
pp. 231-236 ◽  
Author(s):  
Meysam Jafari ◽  
Yuuji Kimura ◽  
Kaneaki Tsuzaki
Keyword(s):  
Rolling Direction ◽  
Charpy Impact ◽  
High Strength ◽  
Ferrite Matrix ◽  
Deformation Texture ◽  
Grain Structure ◽  
Shelf Energy ◽  
Temperature Range ◽  
Delamination Fracture ◽  
Fiber Deformation

Ultrafine elongated grain (UFEG) structures with strong <110>// rolling direction (RD) fiber deformation texture were produced by warm caliber-rolling at 773 K, namely tempforming in the 1200 MPa-class medium-carbon low-alloy steel with phosphorous (P) contents of 0.001 and 0.053 mass%. Charpy impact tests were performed at temperature range of-196 to 150 °C on the UFEG structure. Regardless of P content, high upper shelf energy about 145 J and a very low ductile to brittle transition temperature (DBTT) of around-175 °C were obtained. P segregation embrittlement completely disappeared in the 0.053 %P steel and both steels showed ductile fracture on the planes normal to RD at temperature range of-150 to 150 °C. The main reason for the high upper shelf energy and very low DBTT in the 0.053 %P steel would be delamination fracture along RD when both 0.001 and 0.053 %P steels showed quite similar microstructures including texture. Since the occurrence of delamination requires relatively weak interfaces or planes, P segregated to the ferrite grain boundaries and interfaces of cementite particles-ferrite matrix and made them feasible paths for crack branching and consequently delamination occurred. We showed in this work the advantage of delamination (crack arrester-type) on the high absorbed energy obtained by 0.053 %P steel in comparison with 0.001 %P steel.

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