Microstructure and Mechanical Properties of X80/X100 High Deformability Pipeline Steel

2011 ◽  
Vol 399-401 ◽  
pp. 139-143
Author(s):  
Dian Xiu Xia ◽  
De Liang Meng ◽  
Shou Yong An ◽  
Yong Lin Kang
Keyword(s):  
Pipeline Steel ◽  
Large Strain ◽  
High Strength ◽  
Longitudinal Direction ◽  
Granular Bainite ◽  
Dual Phase ◽  
Cooling Process ◽  
Bainite Structure ◽  
Lath Bainite ◽  
High Deformability

In the present study, X80 and X100 grade high deformability pipeline steels have been processed by using TMCP and followed two-stage cooling process. The microstructures of the X80HD (HD, high deformability) and X100HD steels were both characterized by ferrite-bainite dual phase. The grains sizes of ferrite were mostly less than 5μm and the volume fractions were about 20~25% in X80HD and 10~15% in X100HD steel. The bainite structure in X80HD steel was granular bainite (GB); while in X100HD steel large amounts of lath bainite (LB) were also formed besides GB, and bainite grains were much finer. Ferrite-bainite dual phase microstructure has large strain hardenability that resulting high strength and high deformability combination. Both the steels exhibit high strength/toughness in transverse direction and high deformability in longitudinal direction. The X100HD steel with more volume of LB and less volume of PF has higher strength but lower deformability than that of X80HD steel.

Development of Laminar Flow Cooling of Ultra-High Strength Ferrite-Bainite Dual Phase Steel

2012 ◽  
Vol 184-185 ◽  
pp. 940-943
Author(s):  
Wei Lv ◽  
Di Wu ◽  
Zhuang Li
Keyword(s):  
Tensile Strength ◽  
Ultimate Tensile Strength ◽  
Laminar Flow ◽  
Hot Rolling ◽  
Retained Austenite ◽  
High Strength ◽  
Total Elongation ◽  
Granular Bainite ◽  
Dual Phase ◽  
Dp Steel

In the present paper, controlled cooling in different ways was performed using a laboratory hot rolling mill in ultra-high strength hot rolled ferrite-bainite dual phase (DP) steel. The results have shown that the final microstructures of DP steel comprise ferrite, bainite and a small amount of retained austenite and martensite. DP steel has a tensile strength ranging from 1010 to 1130MPa and yet retains considerable total elongation in the range of 14–17%. The addition of Mn and Nb to DP steel leads to the maximum ultimate tensile strength, yield strength and the product of ultimate tensile strength and total elongation due to the formation of retained austenite and granular bainite structure. Laminar flow cooling after hot rolling results in a significant increase in the quantity of ferrite and bainite due to the suppression of pearlite transformation, and as a result, the present steel possesses high strengths and good toughness.

Control Final Cooling Temperature on High Strength of the Pipeline Radio Yield Influence

2011 ◽  
Vol 117-119 ◽  
pp. 310-314
Author(s):  
Yong Jie Ma ◽  
Xun He ◽  
Guang Liang Zhang
Keyword(s):  
Pipeline Steel ◽  
Steel Production ◽  
High Strength ◽  
Yield Ratio ◽  
X80 Pipeline Steel ◽  
Steel Rolling ◽  
Cooling Temperature ◽  
Lath Bainite ◽  
Bainite Microstructure ◽  
Rolling Technology

In high strength pipeline steel rolling technology, the control of final cooling temperature of different microstructure, different microstructure of pipeline steel tensile strength, yield strength and the effects of different, thus determine its yield ratio differences. The results show that with lath bainite microstructure of the pipeline steel than with acicular ferrite microstructure of the pipeline steel with lower yield ratio, at the same time lath bainite microstructure in small dispersed precipitates in pipeline steel X80 pipeline steel to reduce the yield ratio is beneficial, for high strength pipeline steel production technology to provide the theory basis.

Change of Mechanical Properties of High Strength Line Pipe by Thermal Coating Treatment

2005 ◽  
Author(s):  
Yasuhiro Shinohara ◽  
Takuya Hara ◽  
Eiji Tsuru ◽  
Hitoshi Asahi ◽  
Yoshio Terada ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Volume Fraction ◽  
Uniform Elongation ◽  
High Strength ◽  
Secondary Phase ◽  
Longitudinal Direction ◽  
Dual Phase ◽  
Line Pipe ◽  
Thermal Coating ◽  
Production Conditions

In strain-based design, the overmatch condition in the girth weld portion primarily must be maintained. The pipes may also be required to have a low yield to tensile (Y/T) ratio and a high uniform elongation (U.EL) in the longitudinal direction to achieve a high compressive buckling strain. However, change in the mechanical properties by heating during coating treatment has not been paid attention so much. Furthermore, how much the mechanical properties change is affected by production conditions is unclear. This study aims to clarify firstly the relation between the mechanical properties (Y/T ratio, U.EL etc.) and the microstructure and secondly the change in mechanical properties by thermal coating treatment. The Y/T ratio and U.EL are affected by the volume fraction of ferrite and the secondary phase, which are changed by thermomechanical control processing (TMCP) conditions. For example, use of dual phase microstructure is very effective for decreasing the Y/T ratio and increasing the U.EL as the pipe. On the other hand, yield strength (YS) rises and the U.EL does not change after coating. The increase in the YS after coating is influenced by the microstructure and TMCP conditions. Resultantly, dependence of the Y/T ratio on the microstructure and TMCP conditions is reduced for line pipes after thermal coating treatment.

Microstructure and Mechanical Properties of X70 Pipeline Steel with High H2S Resistance

2015 ◽  
Vol 816 ◽  
pp. 755-760 ◽  
Author(s):  
Jing Li ◽  
Xiu Hua Gao ◽  
Yong Lu ◽  
Lin Xiu Du
Keyword(s):  
Mechanical Properties ◽  
Pipeline Steel ◽  
High Strength ◽  
Granular Bainite ◽  
Second Phase ◽  
Precipitation Behavior ◽  
Experimental Steel ◽  
X70 Pipeline Steel ◽  
The Matrix ◽  
Sour Service

Anti-H2S X70 pipeline steel was developed. The microstructure of X70 pipeline steel was studied by the analysis of OM, SEM and TEM. The precipitation behavior was discussed. The comprehensive mechanical properties, HIC and SCC performance were systematically studied. The results indicated that the microstructure of the experimental steel was mainly acicular ferrite and granular bainite. The second phase precipitates dispersedly distributed in the matrix. The experimental steel possessed excellent strength, plasticity, low temperature toughness and low yield ratio. And therefore, the X70 pipeline steel in the study is suitable for sour service with the high strength, excellent toughness and low HIC&SSC susceptibility.

scholarly journals Morphology and Crystallography Analyses of HSLA Steels with Hardenability Enhanced by Tailored C–Ni Collocation

Metals ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 32
Author(s):  
Zhipeng Liu ◽  
Yishuang Yu ◽  
Jie Yang ◽  
Zhiquan Wang ◽  
Hui Guo ◽  
...  
Keyword(s):  
Driving Force ◽  
Nickel Content ◽  
High Strength ◽  
Transformation Strain ◽  
Steel Plates ◽  
Granular Bainite ◽  
Variant Selection ◽  
High Hardenability ◽  
Hsla Steels ◽  
Lath Bainite

High hardenability is of great importance to ultra-heavy steel plates and can be achieved by tailoring the composition of steel. In this study, the continuous cooling transformation (CCT) curves of two high-strength low-alloy (HSLA) steels (0.16C-0.92Ni steel and 0.12C-1.86Ni steel) were elucidated to reveal the significance of C–Ni collocation on hardenability from the perspective of morphology and crystallography. At a low cooling rate (0.5 °C/s), the 0.12C-1.86Ni steel showed higher microhardness than 0.16C-0.92Ni steel. The microstructure in 0.16C-0.92Ni steel was mainly granular bainite with block-shaped martensite/austenite islands (M/A islands), while that in 0.12C-1.86Ni steel was typically lath bainite with film-shaped M/A islands, denoting that the 0.12C-1.86Ni steel is of higher hardenability. Moreover, the 0.12C-1.86Ni steel exhibited a higher density of block boundaries, especially V1/V2 boundaries. The higher density of block boundaries resulted from the weakened variant selection due to the larger transformation driving force and more self-accommodation of transformation strain induced by the reduced carbon and increased nickel content.

Mechanical Properties and CO2 Corrosion Behavior of High Strength and Toughness X80 Pipeline Steel

2014 ◽  
Vol 1010-1012 ◽  
pp. 1709-1712
Author(s):  
Li Dong Wang ◽  
Feng Lei Liu ◽  
Hui Bin Wu
Keyword(s):  
Corrosion Rate ◽  
Corrosion Behavior ◽  
Acicular Ferrite ◽  
Pipeline Steel ◽  
High Strength ◽  
Strengthening Mechanism ◽  
Granular Bainite ◽  
X80 Pipeline Steel ◽  
Better Than ◽  
Strength And Toughness

A type of X80 grade high strength and toughness pipeline steel was designed and researched. The strengthening mechanism of the steel was analyzed by SEM, TEM and XRD, and the CO2corrosion behavior of the steel was simulated by high-temperature and high-pressure autoclave. The result shows that the microstructure of the base metal is mainly acicular ferrite with a small amount of granular bainite. Acicular ferrite consists of laths which occlude and interweave with each other, and there are many dislocation and carbonitrides distributing in acicular ferrite, which made the pipeline steel have good strength and toughness. Under the simulation of the actual working conditions, the activity of reactants is low at 30°C, so the corrosion rate is smaller at this temperature; the maximum of corrosion rate occurs at 60°C; when the temperature increases to 90°C, the corrosion rate is lower than that of 60°C, that is because hindering corrosion effect which take by the acceleration deposit of corrosion product is better than the acceleration corrosion reactions.

Effect of Heat Imput on Microstructure and Toughness of High Strength Bridge Steel

2011 ◽  
Vol 194-196 ◽  
pp. 255-258
Author(s):  
Kun Ning Jia
Keyword(s):  
Grain Size ◽  
Crack Propagation ◽  
Heat Affected Zone ◽  
High Strength ◽  
Thermal Simulation ◽  
Granular Bainite ◽  
Coarse Grain ◽  
Bridge Steel ◽  
Lath Bainite

The coarse grain heat affected zone(CGHAZ) at different parameters t8/5 of high-strength bridge steel Q460q were simulated with thermal simulation machine. the microstructure of CGHAZ and the effect of granular bainite on the toughness were analyzed in this paper.The results show that: When t8/5<60s, lath bainite and granular bainite intertwine, and the quantity of strip M-A constituents in granular bainite decreased, so toughness is higher.When t8/5>60s, the quantity of eutectoid ferrite and granular bainite increased, coarse M-A constituent resulting in the grain size of effective crack propagation becoming coarser and toughness decreased significantly.

scholarly journals Effect of Bainite Volume Fraction on Deformability of Mesostructures for Ferrite/Bainite Dual-Phase Steel

2020 ◽  
Vol 2020 ◽  
pp. 1-17
Author(s):  
Gui-ying Qiao ◽  
Zhong-tao Zhao ◽  
Xian-bo Shi ◽  
Jun-si Wang ◽  
Fu-ren Xiao
Keyword(s):  
Dual Phase Steel ◽  
Stress Ratio ◽  
Volume Fraction ◽  
Pipeline Steel ◽  
High Strength ◽  
Strain Ratio ◽  
Stress And Strain ◽  
Dual Phase ◽  
Volume Fractions ◽  
Deformation Compatibility

To obtain high strength and excellent deformability for ferrite/bainite dual-phase (F/B DP) pipeline steel for gas pipelines based on strain-based design, the volume fractions of ferrite and bainite should be considered first. In this work, abstract representative volume elements (RVE) of finite element models (FEMs) of mesostructure for F/B DP pipeline steel with volume fractions of bainite between 30% and 58% were established, and the effects of volume fraction of bainite on the tensile properties and deformation compatibility were studied. Results show that the stress and strain in the mesostructure were primarily distributed in the bainite and ferrite, respectively, and strain concentration occurs at the ferrite/bainite interface. With increasing volume fractions of bainite, the strain localization factor (SLF) and strain ratio of ferrite with bainite ( ε F / ε B ) decrease, which can improve the deformation compatibility of the F/B DP pipeline steel. However, the stress ratio of bainite with ferrite ( σ B / σ F ) and the contributions of bainite to stress and strain sequentially increase, and, as a result, the strength increases and the ductility decreases. Therefore, a balance of strength and deformability can be obtained when the optimal volume fraction of bainite is in the range of 40% to 48%.

Microstructure and Deformation Characteristics of X80 High Deformability Pipeline Steel

2011 ◽  
Vol 299-300 ◽  
pp. 323-327 ◽  
Author(s):  
De Liang Meng ◽  
Yong Lin Kang ◽  
Shou Yong An ◽  
Dian Xiu Xia
Keyword(s):  
Pipeline Steel ◽  
Uniform Elongation ◽  
Polygonal Ferrite ◽  
Granular Bainite ◽  
Lower Yield ◽  
On Line ◽  
Line Process ◽  
Three Stages ◽  
Two Stages ◽  
High Deformability

Two kinds of X80 high deformability pipeline steels have been processed by applying two-stage cooling process (TSC) and heat treatment on-line process (HOP). The microstructure of TSC steel and HOP steel are polygonal ferrite (PF) + quasi-polygonal ferrite (QF) + granular bainite (GB) multiphase and QF + GB+ martensite-austenite (M/A) multiphase respectively. In HOP steel, the volume of M/A is much more and the size is much larger than that in TSC steel. Some degenerated M/A constituents are also observed in HOP steel. The HOP steel has shown higher tensile strength, lower yield ratio and lower uniform elongation than TSC steel. The strain-nI (instantaneous n-value) curve of HOP steel could be divided into two stages and the TSC’s could be separated to three stages.

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