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.

scholarly journals Effect of Cooling Rate on The Microstructure And Cryogenic Impact Toughness of HAZ in 9% Ni Steel

2021 ◽  
Vol 59 (11) ◽  
pp. 781-795
Author(s):  
Hae Won Eom ◽  
Joo Yeon Won ◽  
Sang Yong Shin
Keyword(s):  
Grain Size ◽  
Impact Toughness ◽  
Grain Boundaries ◽  
Cooling Rate ◽  
Volume Fraction ◽  
Lath Martensite ◽  
Coarse Grained ◽  
High Angle ◽  
Tempered Martensite ◽  
Effective Grain Size

The effects of cooling rate on the microstructure and cryogenic impact toughness of coarse-grained heat-affected zone (CGHAZ) and inter-critically reheated coarse-grained HAZ (IC CGHAZ) in 9% Ni steel were investigated. CGHAZ and IC CGHAZ specimens were prepared from 9% Ni steel by controlling the cooling rate of the simulated welding process. The microstructure of the CGHAZ specimens consisted of autotempered martensite and lath martensite. As the cooling rate increased, the volume fraction of the autotempered martensite and the effective grain size decreased. A large amount of fine carbides was distributed inside the auto-tempered martensite, the dislocation density was low, and high angle grain boundaries were not observed. The microstructure of the IC CGHAZ specimens consisted of tempered martensite and lath martensite. As the cooling rate increased, the volume fraction of the tempered martensite and effective grain size decreased. Finer carbides were distributed inside the tempered martensite than in the auto-tempered martensite, the dislocation density was low, and high angle grain boundaries were not observed. Cryogenic fracture revealed that ductile fracture occurred in the auto-tempered martensite and tempered martensite, and brittle fracture occurred in the lath martensite. The crack propagation path was zig-zag in the high angle grain boundaries of the lath martensite. The volume fraction of auto-tempered martensite and tempered martensite and the effective grain size in the HAZ specimens had a significant effect on cryogenic impact toughness. In the IC CGHAZ specimens, cryogenic impact toughness decreased and then became constant as the cooling rate increased, due to a decrease in the volume fraction of the tempered martensite and effective grain size.

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.

The Effect of Twice Thermal Cycle on the Microstructure and Mechanical Properties of Coarse Grain Region in X80 Pipeline Steel

2017 ◽  
Vol 898 ◽  
pp. 749-752
Author(s):  
Shuo Li ◽  
Xiao Jiang Guo ◽  
Ye Zheng Li ◽  
Yong Li Sui ◽  
Zong Bin You
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Impact Toughness ◽  
Thermal Cycle ◽  
Pipeline Steel ◽  
Bainitic Ferrite ◽  
Peak Temperature ◽  
Coarse Grain ◽  
X80 Pipeline Steel ◽  
Microstructure And Mechanical Properties

Based on the multi-pass welding characteristics of X80 pipeline steel, the influence of twice thermal cycle on the microstructure and mechanical properties of coarse grain region in X80 pipeline steel was investigated. The thermal cycles of weld coarse grain region with different peak temperature for the second thermal cycle were simulated with the Gleeble-3500 thermal/mechanical simulator. The Charpy impact absorbed energy for toughness was measured, and the corresponding optical micrographs and electron micrographs were systematically investigated to study the effect of the peak temperature on microstructure and impact toughness in the coarse grain region. The results of simulated experiment showed that the microstructure in heat affected zone of coarse grain region is granular bainitic and bainitic ferrite. When the peak temperature of the second thermal cycle is 800°C, the types of microstructure and the grain size of original austenite have no change. However, it forms network microstructure with chain structure in grain boundary and the reduction of toughness may be affected by the M–A constituents. With the peak temperature of 1000°C, the micro structure is composed of granular bainitic and a little bainitic ferrite. In this case, the grain size of austenite can be significantly fined, being helpful to increase the impact toughness.

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.

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.

scholarly journals Incremental ECAP as a Method to Produce Ultrafine Grained Aluminium Plates

2016 ◽  
Vol 710 ◽  
pp. 59-64 ◽  
Author(s):  
Malgorzata Lewandowska ◽  
Witold Chrominski ◽  
Marta Lipinska ◽  
Lech Olejnik ◽  
Andrzej Rosochowski
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Rolling Direction ◽  
Microstructure Development ◽  
High Angle ◽  
New Approach ◽  
Rectangular Shape ◽  
Incremental Processing ◽  
Ultrafine Grained ◽  
Accumulated Strain

In this work, we propose a new approach to producing ultrafine grained plates using a modified ECAP method, namely incremental ECAP. Unlike conventional ECAP, incremental ECAP works step by step whereby deformation and feeding are performed with two different tools acting asynchronously. Incremental processing reduces forces and allows to process relatively large billets. The major advantage of this technique is that the specimens are in the form of plates with a rectangular shape, which makes them suitable for further processing, e.g. via deep drawing. This paper reports a study on microstructure development, mechanical properties and their anisotropy in aluminium plates processed by means of incremental ECAP. Eight passes applied (with the accumulated strain of 9.2) with the rotation about the Z axis brought about the reduction in the grain size down to 600 nm with the 80% fraction of high angle grain boundaries and a very homogenous equiaxial microstructure. This, in turn, resulted in a significant increase in mechanical strength with the ultimate tensile strength reaching 200 MPa and, more importantly, very low anisotropy with respect to the rolling direction.

Effect of Ferrite Volume Fraction on Mechanical Properties of X80 Pipeline Steel

2014 ◽  
Vol 989-994 ◽  
pp. 212-215
Author(s):  
J. Liu ◽  
G. Zhu ◽  
W. Mao
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Work Hardening ◽  
Single Phase ◽  
Volume Fraction ◽  
Pipeline Steel ◽  
X80 Pipeline Steel ◽  
Hardening Behavior ◽  
Two Phases ◽  
Better Than

The effect of volume fraction of ferrite on the mechanical properties including strength, plasticity and wok hardening was systematically investigated in X80 pipeline steel in order to improve the plasticity. The microstructures with different volume fraction of ferrite and bainite were obtained by heat-treatment processing and the mechanical properties were tested. The work hardening behavior was analyzed by C-J method. The results show that the small amount of ferrite could effectively improve the plasticity. The work hardening ability and the ratio of yield/tensile strength with two phases of ferrite/bainite would be obviously better than that with single phase of bainite. The improvement of plasticity could be attributed to the ferrite in which more plastic deformation was afforded.

Effect of Li on Mechanical Properties and Electrical Conductivity of the Al–Zn–Cu–Mg Based Alloys

2021 ◽  
Vol 21 (9) ◽  
pp. 4897-4901
Author(s):  
Hyo-Sang Yoo ◽  
Yong-Ho Kim ◽  
Hyeon-Taek Son
Keyword(s):  
Mechanical Properties ◽  
Electrical Conductivity ◽  
Grain Size ◽  
Tensile Strength ◽  
Spherical Particles ◽  
Al Alloy ◽  
High Angle ◽  
Average Grain Size ◽  
Strength Improvement ◽  
Li Content

In this study, changes in the microstructure, mechanical properties, and electrical conductivity of cast and extruded Al–Zn–Cu–Mg based alloys with the addition of Li (0, 0.5 and 1.0 wt.%) were investigated. The Al–Zn–Cu–Mg–xLi alloys were cast and homogenized at 570 °C for 4 hours. The billets were hot extruded into rod that were 12 mm in diameter with a reduction ratio of 38:1 at 550 °C. As the amount of Li added increased from 0 to 1.0 wt.%, the average grain size of the extruded Al alloy increased from 259.2 to 383.0 µm, and the high-angle grain boundaries (HGBs) fraction decreased from 64.0 to 52.1%. As the Li content increased from 0 to 1.0 wt.%, the elongation was not significantly different from 27.8 to 27.4% and the ultimate tensile strength (UTS) was improved from 146.7 to 160.6 MPa. As Li was added, spherical particles bonded to each other, forming an irregular particles. It is thought that these irregular particles contribute to the strength improvement.

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