Research of High Grade HIC-Resistant Pipeline Steel

2014 ◽  
Vol 900 ◽  
pp. 730-733 ◽  
Author(s):  
Xiu Hua Gao ◽  
Jing Li ◽  
Chuang Li ◽  
Yan Liang ◽  
Lin Xiu Du ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Grain Boundary ◽  
Pipeline Steel ◽  
Granular Bainite ◽  
High Grade ◽  
Good Resistance ◽  
Corrosion Resistant ◽  
Structures And Properties ◽  
Hydrogen Induced Cracking ◽  
Closed Formation

Carry out research on the processes, structures and properties of the X70 corrosion-resistant pipeline steel and analyze the mechanism of the hydrogen induced cracking. The results show that: the developed steel not only has excellent mechanical properties, but also has good resistance to H2S corrosion. Microstructure of the X70 corrosion-resistant pipeline is mainly the acicular ferrite and granular bainite, with well-closed formation and fine grains. Hydrogen Induced Cracking (HIC) begins with the appearance of the hydrogen blistering on the specimen surface, and cracks generated by the hydrogen blistering gradually extend inward from the surface along the grain boundary, diffuse inside the specimen gradually, and finally form hydrogen induced cracking.

The Micro Structural Characteristic Parameters of High Grade Pipeline Steel and its Mechanical Properties

2006 ◽  
Author(s):  
Xiaoli Zhang ◽  
Chuanjing Zhuang ◽  
Lingkang Ji ◽  
Yaorong Feng ◽  
Wenzhen Zhao ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Pipeline Steel ◽  
Structural Parameters ◽  
Large Angle ◽  
Lower Bainite ◽  
Granular Bainite ◽  
High Grade ◽  
Pipeline Steels

The microstructure of high grade pipeline steels, including X65, X70, X80, X100, were studied by SEM and EBSD, respectively. It was found that the microstructures of high grade pipeline steels were composed of lower bainite, granular bainite and acicular ferrite. The phases of kinds of pipeline steels were composed of Fe3C, retained austenite and ferrite. And their percentage content, grain size and its distribution were studied respectively also. These micro structural parameters were correlated to the mechanical properties of kinds of pipeline steels. Furthermore, all kinds of angles of grain boundaries were studied, and the relationship between the angles of grain boundaries and mechanical properties was obtained. It was shown that as the improving of the steel grade, the grain boundary including small angle and large angle increased. And only when grain boundary was greater than 15 degree, it was effective to the toughness behavior.

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.

Microstructure and Mechanical Properties of Joints of X100 Line Pipe by Submerged Arc Welding

2013 ◽  
Vol 310 ◽  
pp. 139-144 ◽  
Author(s):  
Min Zhang ◽  
Liang Yang
Keyword(s):  
Mechanical Properties ◽  
Electron Microscope ◽  
Shear Fracture ◽  
Pipeline Steel ◽  
Testing Machine ◽  
Fracture Morphology ◽  
Impact Testing ◽  
Granular Bainite ◽  
Line Pipe ◽  
The Impact

The microstructure, mechanical properties, fracture morphology and crystal texture of pipeline steel X100 welded joints were investigated using optical electron microscope, scanning electron microscope, tensile and impact testing machine. The results show that, the texture of X100 line pipe mainly consists of acicular ferrite and granular bainite in weld zones, the microstructure of HAZ is coarser, which lead to softening and embrittlement. The fusion line is clear between outer weld and inner weld. The tensile strength of welded joint gets to 803 MPa, which is about 94.81% of the base materials. The impact energy at -10°C is more than 120J, and the average of percent shear fracture appearance at -10°C is up to 85%, is ductile fractures.

Effect of Nanocalcium Oxide Addition on the Cast Microstructure of Pipeline Steel

2013 ◽  
Vol 380-384 ◽  
pp. 4241-4244
Author(s):  
Jian Ming Wang ◽  
Yan Liu ◽  
Long Xian Ding ◽  
Chun Lin He
Keyword(s):  
Thermal Stability ◽  
High Temperature ◽  
Grain Boundary ◽  
Pipeline Steel ◽  
Granular Bainite ◽  
Second Phase ◽  
X80 Pipeline Steel ◽  
Oxide Addition ◽  
Second Phase Particles ◽  
Cast Microstructure

This experiment takes the X80 pipeline steel as the research object, the thermal stability second phase particles which would not be dissolved or aggregated at high temperature will be expected by means of adding nanocalcium oxide into the steel with the method of carrier dispersion addition. The effect of nanocalcium oxide addition on the cast microstructure of X80 pipeline steel was analysed. The results show that the cast microstructure is consist of the ferrite and a small amount bainite. And the bainite is distributed at the boundary of the ferrite grains. When adding 0.02 wt% nanocalcium oxides, there is more bainite in the microstructure by contrast. The number of the acicular ferrite significantly increases in the cast microstructure, and the grains become more fine and uniform. Simultaneously, the granular bainite is uniformly distributed at the grain boundary and edge of the ferrite.

scholarly journals Effect of Hot Working Processes on Microstructure and Mechanical Properties of Pipeline Steel

Crystals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 860
Author(s):  
Huiling Ji ◽  
Yiwei Zhang ◽  
Wenzhao Lu ◽  
Bang Wei ◽  
Xiaomin Yuan
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Cooling Rate ◽  
Acicular Ferrite ◽  
Pipeline Steel ◽  
Granular Bainite ◽  
Isothermal Quenching ◽  
Electron Backscattered Diffraction ◽  
Quenching Temperature ◽  
Treatment Conditions

The microstructure and microhardness of X70 pipeline steel were investigated after conducting different processing routes. The microstructure was characterized using optical and electron microscopy. Scanning electron microscopy equipped with electron backscattered diffraction (EBSD) and transmission electron microscopy techniques were applied for investigation of different thermal processing treatment conditions. Mechanical properties were characterized by a microhardness tester. The results show that the microstructure mainly consists of granular bainite, acicular ferrite and a small amount of M/A constituents under hot rolling states. There are many dislocations inside the acicular ferrite. The thermal simulation experiments show that the microstructure becomes homogeneous with the increase in cooling rate. The acicular ferrite morphology becomes fine and uniform, and the content of M/A constituents increases at the same compression amount. The compression gives rise to the accumulated strain and stored energy, which accelerate the transformation of acicular ferrite and refine the microstructure of the pipeline steel. The microhardness rises with the increase in deformation ratio and cooling rate. The microstructure of the pipeline steel subjected to the isothermal quenching process is ultrafine ferrite and M/A islands. When the isothermal quenching temperature reaches 550 °C, a small amount of upper bainite appears in the microstructure. With the increase in isothermal quenching temperature, the microhardness decreases. Acicular ferrite is a better candidate microstructure than ultrafine ferrite for the pipeline steels.

Effect of M/A Constituents on Mechanical Properties of High Grade Pipeline Steel

2011 ◽  
Vol 284-286 ◽  
pp. 1271-1274 ◽  
Author(s):  
Li Xia Zhu ◽  
Xiao Dong He ◽  
Xin Li Han ◽  
Ting Ting Qu
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Impact Toughness ◽  
Room Temperature ◽  
Welded Joint ◽  
Pipeline Steel ◽  
Morphological Changes ◽  
High Impact ◽  
High Grade ◽  
High Tensile Strength

The morphological changes, dimension and distribution of M/A constituent in different region of X80 acicular ferrite pipeline steel were investigated; the effect of M/A constituents of X80 on Charpy V-impact and room temperature tensile properties were also discussed by OM and SEM. The results show that: the distribution and morphosis of the M/A constituents have strongly effect on the mechanical properties. The uniformly distributed massive M/A constituents with chord less than 2 μm observed in grains of base metal, presents high impact toughness and high tensile strength, and the strip M/A constituents with chord more than 2 μm observed in welded joint samples exhibits low impact toughness and high tensile strength. It is seems that the changes of the morphosis and distribution of M/A constituents induce the hardening effect during the deformation which is the main reason to the different mechanical property.

Microstructure and Mechanical Properties Analysis of X70 Pipeline Steel with Polygonal Ferrite Plus Granular Bainite Microstructure

2012 ◽  
Vol 161 ◽  
pp. 67-71 ◽  
Author(s):  
Zhan Zhan Zhang ◽  
Xiu Rong Zuo ◽  
Yue Yue Hu ◽  
Ru Tao Li ◽  
Zhi Ming Zhang
Keyword(s):  
Mechanical Properties ◽  
Pipeline Steel ◽  
High Strength ◽  
Polygonal Ferrite ◽  
Granular Bainite ◽  
X70 Pipeline Steel ◽  
Microstructure And Mechanical Properties ◽  
Drop Weight ◽  
Bainite Microstructure ◽  
Strength And Toughness

Microstructure and mechanical properties of X70 pipeline steel with polygonal ferrite plus granular bainite were characterized using tensile tests, Charpy V-notch impact tests, drop weight tear tests, hardness tests and scanning electron microscopy. The results of experiment indicated that X70 pipeline steel with polygonal ferrite plus granular bainite showed an excellent combination of high strength and toughness. The base metal with polygonal ferrite plus granular bainite microstructure exhibited perfect mechanical properties in terms of the transverse yield ratio of 0.81, elongation of 46%, an impact energy of 335 J at -10 °C and a shear area of 90% at 0 °C in the drop weight tear test. The heat affected zone contained coarse grain zone and fine grain zone, which exhibited good low temperature toughness of 216 J at -10 °C. The weld metal primarily consisted of intragranularly nucleated acicular ferrites which led to the high strength and toughness.

Effect of Slag-Metal Reaction on Transformation of Al2O3 inclusions in Pipeline Steel

2011 ◽  
Vol 284-286 ◽  
pp. 1143-1147
Author(s):  
Qiang Li ◽  
Xin Hua Wang ◽  
Hai Bo Li
Keyword(s):  
Molten Steel ◽  
Pipeline Steel ◽  
Refining Process ◽  
High Grade ◽  
Secondary Refining ◽  
Calcium Aluminates ◽  
Hydrogen Induced Cracking ◽  
Liquid Calcium ◽  
Calcium And Magnesium ◽  
Refining Time

For high grade pipeline steel, elimination of Al2O3 inclusions can improve the susceptibility of hydrogen-induced cracking (HIC) and stress corrosion cracking (SCC). In the present work, the transformation of Al2O3 inclusions with slag-metal reaction was studied by controlling ladle slag and relative technologies in LF-RH refining process. It is found that Al2O3 inclusions decrease with increasing refining time, and no pure Al2O3 inclusions exist in molten steel at the end of secondary refining; the remained inclusions in molten steel are liquid calcium aluminates and semi-liquid CaO-MgO-Al2O3 complex inclusions. The analysis of thermodynamic equilibrium proves that CaO and MgO in slag can be reduced by aluminum in molten steel, which is the source of calcium and magnesium in molten steel.

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