scholarly journals Microstructure and Strengthening/Toughening Mechanisms of Heavy Gauge Pipeline Steel Processed by Ultrafast Cooling

Metals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1323
Author(s):  
Xue-qiang Wang ◽  
Guo Yuan ◽  
Jin-hua Zhao ◽  
Guo-dong Wang
Keyword(s):  
Pipeline Steel ◽  
Bainitic Ferrite ◽  
Strengthening Mechanism ◽  
Grain Refining ◽  
Toughening Mechanisms ◽  
X80 Pipeline Steel ◽  
Pipeline Steels ◽  
X70 Pipeline Steel ◽  
Controlled Processing ◽  
Ultrafast Cooling

Heavy gauge pipeline steels experience a low qualification in drop-weight-tear test properties because of the low cooling capability of conventional thermomechanical controlled processing. To solve this problem, a new-generation thermomechanical-controlled processing technology based on ultrafast cooling was applied to prepare heavy gauge pipeline steels. The microstructure, strengthening and toughening mechanisms of 25.4 mm X70 and 22 mm X80 pipeline steels that were processed by ultrafast cooling were studied. The microstructures of the 25.4 mm X70 and 22 mm X80 pipeline steels consisted of bainitic ferrite, M-A island and acicular ferrite with a large fraction above 85%. The grain size and high-angle grain boundary fraction of X70 pipeline steel were 2.7 μm and 43%, respectively, whereas those of the X80 pipeline steel were 2.4 μm and 45%, respectively. The strengthening and toughening mechanisms were studied for the ultrafast cooling method. The main strengthening mechanism for 25.4 mm X70 pipeline steel was solution and grain-refining strengthening and precipitation strengthening with contributions of ~456 MPa and ~90.5 MPa, respectively. In the 22 mm X80 pipeline steel, the main strengthening mechanism was the solution and grain-refining strengthening, and dislocation strengthening with contributions of ~475 MPa and ~109.8 MPa, respectively.

Effects of Cooling Processes on Microstructure Evolution of X80 Pipeline Steel

2014 ◽  
Vol 788 ◽  
pp. 378-383 ◽  
Author(s):  
Feng Qin Ji ◽  
Guo Dong Wang
Keyword(s):  
Low Temperature ◽  
Pipeline Steel ◽  
Bainitic Ferrite ◽  
Development Trend ◽  
Optical Microscope ◽  
Granular Bainite ◽  
X80 Pipeline Steel ◽  
Pipeline Steels ◽  
Low Temperature Toughness ◽  
Strength And Plasticity

With the development of pipeline industry, the pipeline steels with higher strength and plasticity, better low-temperature toughness and weldability are the main development trend. For bainitic pipeline steels, M/A constituent is the main hard phase. Although the M/A constituent can enhance the strength, the larger block-form M/A constituent can deteriorate low-temperature toughness. Therefore, it is essential to further investigate how to refine the M/A constituent. In the present paper, X80 pipeline steel was cooled to room temperature with various cooling paths after hot compression deformation at the temperature of 800oC. The evolution of microstructure of X80 pipeline steel has been analyzed by optical microscope (OM) and scanning electron microscope (SEM). The experimental results show that increasing the cooling rate can significantly refine M/A constituent and promote the formation of granular bainite, and the bainitic ferrite can be also greatly refined. In addition, the effects of five final temperatures of fast cooling were also investigated.

Industrial Trial Production of X70 Pipeline Steel under Ultra Fast Cooling Conditions

2011 ◽  
Vol 121-126 ◽  
pp. 3340-3344
Author(s):  
Yong Tian ◽  
Shuai Tang ◽  
Guo Dong Wang ◽  
Pu Wang
Keyword(s):  
Pipeline Steel ◽  
Vanadium Content ◽  
X80 Pipeline Steel ◽  
Pipeline Steels ◽  
X70 Pipeline Steel ◽  
Ultra Fast Cooling ◽  
Plate Rolling ◽  
Rolling Production ◽  
Fast Cooling ◽  
The Impact

A successful ultra fast cooling (UFC) technology has been applied to the plate rolling production line in Shouqin Metal Materials Co.Ltd.. Industrial trials are reported for the production of X70 pipeline steels (about 70000 t) under UFC conditions. Pipeline steels with reasonably good properties have been produced on an industrial scale. UFC improves the temperature uniformity, the mechanical properties and the plate profile of X70 pipeline steel. The impact values of X70 pipeline steel at UFC mode exceed the standard requirements of X80 pipeline steel. The productivity is enhanced because cutting quantity of head and tail of the plate is reduced. The enhancement of control accuracy of the red back temperatures is favorable for industrial production of X70 pipeline steel. The reduced production of the steel-making has been industrialized achieved, since a new composition was designed by reducing the vanadium content to less than 0.045wt.%.

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.

Quantification of Splitting in X80 Pipeline Steel

2018 ◽  
Author(s):  
Alexey Gervasyev ◽  
Roumen Petrov ◽  
Igor Pyshmintsev ◽  
Chunyong Huo ◽  
Frank Barbaro
Keyword(s):  
Pipe Wall ◽  
Pipeline Steel ◽  
Test Results ◽  
X80 Pipeline Steel ◽  
Pipe Wall Thickness ◽  
Microstructural Parameters ◽  
Controlled Processing ◽  
Ebsd Data ◽  
Depth Analysis ◽  
Electron Back Scattered Diffraction

The results of in-depth analysis of microstructure and crystallographic texture of several industrial batches of line pipes with known full-scale burst test results are presented. Several microstructural features promoting splitting are highlighted and quantified using electron back-scattered diffraction (EBSD) data. The actual splitting intensity is evaluated by means of Charpy tests in the direction of pipe wall thickness (Z-direction) and correlates with the microstructural parameters determined by EBSD analysis. This knowledge can be used in the design of thermo-mechanical controlled processing (TMCP) dedicated to production of splitting-free steel.

Simulation of the Hydrogen Permeation Behavior of X80 Pipeline Steels in H2S Saturated Environment by Cathodic-Charging Method

2013 ◽  
Vol 650 ◽  
pp. 72-77
Author(s):  
Feng Huang ◽  
Wei Yuan ◽  
Qian Hu ◽  
Jing Liu ◽  
Yan Miao Qu
Keyword(s):  
Heat Treatment ◽  
Kinetic Parameters ◽  
Current Density ◽  
Hydrogen Permeation ◽  
Pipeline Steel ◽  
X80 Pipeline Steel ◽  
Pipeline Steels ◽  
Hydrogen Charging ◽  
Charging Current ◽  
Current Densities

Hydrogen-charging with various current densities was used to introduce hydrogen into X80 pipeline steel. The permeability (J∞L), the apparent diffusivity (Dapp) and the solubility of hydrogen (Capp)in X80 pipeline steels which were calculated by electrochemical hydrogen permeation curves were compared with those obtained from that of X80 pipeline steels in H2S saturated environment. Results show that in 0.5 mol/L H2SO4+ 3.1×10-3mol/L Na4P2O7(hydrogen evolution poison) solution, when hydrogen-charging current density is 30 mA/cm2, the kinetic parameters of hydrogen permeation of X80 pipeline steels agree with that of H2S saturated environment well. Another two heat-treatment specimens of X80 pipeline steel furthermore verified the reliability of the simulating results.

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.

STRESS CORROSION CRACK INITIATION BEHAVIOR FOR THE X70 PIPELINE STEEL BENEATH A DISBONDED COATING

2012 ◽  
Vol 48 (10) ◽  
pp. 1267 ◽  
Author(s):  
Zhiying WANG ◽  
Jianqiu WANG ◽  
En-hou HAN ◽  
Wei KE ◽  
Maocheng YAN ◽  
...  
Keyword(s):  
Crack Initiation ◽  
Stress Corrosion ◽  
Stress Corrosion Crack ◽  
Pipeline Steel ◽  
X70 Pipeline Steel ◽  
Disbonded Coating
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