Microstructure and Properties of Heat-Affected Zones in X100 Steel Grade Line Pipes

2009 ◽  
Author(s):  
Chuanjing Zhuang ◽  
Na Li ◽  
Shipeng Wang ◽  
Weiping Lin ◽  
Jicheng Ren
Keyword(s):  
Heat Affected Zone ◽  
Thermal Cycle ◽  
Deleterious Effect ◽  
Ferrite Matrix ◽  
Steel Grade ◽  
Peak Temperature ◽  
Coarse Grained ◽  
Microstructure And Properties ◽  
The Relationship ◽  
Second Peak

The relationship between microstructure and properties of weld heat-affected zones in X100 grade pipeline steels was studied. It was found that the intercritically reheated coarse-grained heat-affected zone (IRCGHAZ) of experimental steels has the lowest toughness values when the second peak temperature is at the intercritical (α + γ) region during multi-pass welding. The local embrittlement is attributed to the morphology, amount, and size of the M-A constituent. It is also found that the microstructural inheritance at IRCGHAZ has a deleterious effect on toughness. On the basis of the experimental results, it is suggested that the local embrittlement could be prevented by using pre-heating or post-heating thermal cycle. Pre-heating thermal cycle would eliminate the microstructural inheritance and meliorate M-A constituent. Furthermore, the use of a post-heating thermal cycle will improve the morphology, amount and size of the M-A constituent, and improve the conformation of ferrite matrix.

Microstructure and Properties of HAZ in Low-Carbon Bainite E550 Steel during Double-Pass Welding Thermal Cycle

2018 ◽  
Vol 913 ◽  
pp. 317-323 ◽  
Author(s):  
Yun Zong ◽  
Chun Ming Liu
Keyword(s):  
Impact Toughness ◽  
Heat Affected Zone ◽  
Thermal Cycle ◽  
Coarse Grained ◽  
Granular Bainite ◽  
Low Carbon ◽  
Microstructure And Properties ◽  
Welding Thermal Cycle ◽  
Low Carbon Bainite ◽  
The Impact

Investigations on the microstructure and properties of the Coarse-Grained Heat-Affected Zone (CGHAZ) and intercritical reheated Coarse-Grained Heat-Affected Zone (ICCGHAZ) of a low-carbon bainite E550 steel were carried out using thermal simulation technology in this paper.Double-pass welding thermal cycle were performed on Gleeble-3800 thermal simulator, tempering heat treatment of the critical coarse crystal zone carried out in a box resistance furnace, low impact energies at -40 °C and Vickers hardness determined, and the microstructure were observed. The experimental results show that the microstructure of CGHAZ (Tp1 is 1320 °C) was dominated by coarse granular bainite and Lath bainite Ferrite, the impact toughness of CGHAZ was poor. The toughness of the CGHAZ was improved after second welding heat cycle except intercritical two-phase heating. When the peak temperature of the second thermal cycle(Tp2) was 650 °C, martensite-austenite (M-A) constituent of original CGHAZ wasdecomposed and refined, impact toughness and hardness were all higher than that of CGHAZ; When Tp2 is 750 °C, there was a ” necklace” distribution of massive M-A constituent in this ICCGHAZ, the impact energy at -40 °C prominently decreased and Hardness went up; When Tp2 was in the temperature range of 850 °C ~1100 °C, the microstructure was mainly finer granular bainite, the toughness of CGHAZ could be effectively improved; When Tp2 was over 1100 °C, M-A constituents become coarse, the toughness declined slightly . The changing of hardness was the opposite of toughness but the hardness fluctuation was comparatively small. After tempering at different temperature (520 °C~640 °C) , the grain boundary "necklace" structure of ICCGHAZ was still obvious, some of the M-A constituent were decomposed, the hardness decreased, the lowest hardness was obtained in 610 °C.

Microstructure and Toughness Properties of Subcritically, Intercritically and Supercritically Heat Affected Zones in X80 Microalloyed Pipeline Steel

2011 ◽  
Vol 383-390 ◽  
pp. 5886-5893
Author(s):  
Sadegh Moeinifar
Keyword(s):  
Heat Affected Zone ◽  
Prior Austenite ◽  
Charpy Impact ◽  
Impact Testing ◽  
Peak Temperature ◽  
Coarse Grained ◽  
Secondary Peak ◽  
Thermal Cycles ◽  
Austenite Grain ◽  
Prior Austenite Grain

The influence of the real and simulated thermal cycles with different secondary peak temperatures on the properties of the reheated coarse grained heat affected zone (CGHAZ) in the X80 microalloyed steel has been investigated. The four wires tandem submerged arc welding process with different heat input values was used to generate real double passes thermal cycles. The simulated thermal cycles involved heating to the first peak temperature (TP1) of 1400 °C and then reheating to different secondary peak temperatures (TP2) of 700, 800 and 900 °C with cooling rates of 3.75 and 2 °C/s. The toughness of the simulated reheated CGHAZ with different peak temperature was assessed using Charpy impact testing at 0 °C and -50 °C. It is clear that the reheated CGHAZ thermal cycles with different second peak temperatures have a significant effect on morphology of the martensite/austenite (M/A) constituent. The blocky and connected M/A constituent along the prior-austenite grain boundaries as a brittle phase for crack initiation. The Charpy impact results indicated that intercritically reheated coarse grained heat affected zone had less absorbed energy with higher transition temperature and hardness. In the same prior-austenite grain size, cycles 2 and 4 with lower cooling rate (2 °C/s) have larger size of M/A constituents. The M/A constituent size such as mean diameter and length are important factors influencing Charpy impact properties of the simulated reheated CGHAZ.

Microstructure and Toughness Properties of Subcritically, Intercritically and Supercritically Heat Affected Zones in X80 Pipeline Steel

2010 ◽  
Vol 154-155 ◽  
pp. 1850-1854 ◽  
Author(s):  
Sadegh Moeinifar
Keyword(s):  
Pipeline Steel ◽  
Charpy Impact ◽  
Initiation Site ◽  
Impact Testing ◽  
Peak Temperature ◽  
Coarse Grained ◽  
X80 Pipeline Steel ◽  
Brittle Phase ◽  
Charpy Impact Testing ◽  
Second Peak

The objective of this paper is to study the influence of second peak temperature during simulated welding on properties of the subcritically (S), intercritically (IC) and supercritically (SC) reheated coarse grained heat affected (CGHAZ) zones. This involved heating to a first peak temperature (TP1) of 1400 °C, then reheating to different second peak temperatures (TP2) of 700, 800 and 900 °C with a constant cooling rate of 3.75 °C/s. Toughness of the simulated reheated CGHAZ regions were assessed using Charpy impact testing at 0 and -50 °C. The blocky and connected M/A particles, along prior-austenite grain boundaries, act as a brittle phase for the initiation site of the brittle fracture. Charpy impact results indicated that IC CGHAZ had less absorbed energy with higher transition temperature and hardness.

scholarly journals Study on Hydrogen Diffusion and Sulfide Stress Cracking Behaviors of Simulated Heat-Affected Zone of A516-65 Grade Pressure Vessel Carbon Steel

2020 ◽  
Vol 58 (9) ◽  
pp. 599-609
Author(s):  
Dong Min Cho ◽  
Jin-seong Park ◽  
Jin Woo Lee ◽  
Sung Jin Kim
Keyword(s):  
Heat Affected Zone ◽  
Heat Input ◽  
Thermal Cycle ◽  
Hydrogen Diffusion ◽  
Tensile Load ◽  
Localized Corrosion ◽  
Coarse Grained ◽  
Stress Cracking ◽  
Sulfide Stress ◽  
Sulfide Stress Cracking

Hydrogen diffusion and sulfide stress cracking of simulated heat-affected zone (HAZ) of A516- 65 grade steel were examined using an electrochemical permeation technique, glycerin volumetric method, and constant loading method. HAZ samples were fabricated using a metal thermal cycle simulator with a welding heat input of 20, 35, and 50 kJ/cm. The fractions of bainite and martensite-austenite (M-A) constituent in coarse-grained HAZ (CGHAZ) and intercritical HAZ (ICHAZ) obtained by a simulated thermal cycle with a low heat input (20 kJ/cm) were higher than those with a higher heat input. These fractions contributed to the increase in the reversible hydrogen trap density (N<sub>[H]rev</sub>) and reversibly trapped hydrogen concentrations (C<sub>rev</sub>). Although CGHAZ had higher N<sub>[H]rev</sub> and C<sub>rev</sub> meaning that it is more likely to be vulnerable to brittle failure by hydrogen, actual fracture by sulfide stress cracking (SSC) occurred in ICHAZ composed of a mixture of soft ferrite/pearlite, and hard bainite and M-A. The hydrogen diffusion/trapping parameters, which were obtained from the electrochemical permeation or glycerin method, cannot be directly indicative of the resistance to SSC of the steel in a H<sub>2</sub>S environment. The susceptibility to SSC was more influenced by the level of M-A-localization and localized corrosion attack, acting as a stress intensifier under a tensile load.

Effect of Welding Heat Cycle Peak Temperature and Heat Input on HAZ Grain Size of SMA490BW Corrosion Resistance Steel

2012 ◽  
Vol 602-604 ◽  
pp. 415-420 ◽  
Author(s):  
Ming Yue Zhang ◽  
Yuan Nie ◽  
Qing Ying Wang ◽  
Hui Chen
Keyword(s):  
Grain Size ◽  
Corrosion Resistance ◽  
Heat Affected Zone ◽  
Thermal Cycle ◽  
Great Influence ◽  
Peak Temperature ◽  
Line Energy ◽  
Heat Cycle ◽  
Welding Thermal Cycle ◽  
Gleeble 3500

Welding thermal cycle of SMA490BW corrosion resistance steel with different heat inputs were simulated by using Gleeble-3500 thermo-mechanical simulator to investigate the grain size of the heat affected zone (HAZ). Results show that welding heat cycle peak temperature has great influence on the grain size with the same other conditions, the higher peak temperature is the bigger grain size is; in different welding thermal cycling conditions, line energy affects grain size differently; specimens which experienced two thermal cycle have smaller grain size than which experienced just one thermal cycle.

scholarly journals Characterization of Microstructures and Fatigue Properties for Dual-Phase Pipeline Steels by Gleeble Simulation of Heat-Affected Zone

Materials ◽  
2019 ◽  
Vol 12 (12) ◽  
pp. 1989 ◽  
Author(s):  
Zuopeng Zhao ◽  
Pengfei Xu ◽  
Hongxia Cheng ◽  
Jili Miao ◽  
Furen Xiao
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Crack Propagation ◽  
Grain Boundaries ◽  
Crack Growth ◽  
Fatigue Crack Propagation ◽  
Heat Affected Zone ◽  
Peak Temperature ◽  
Coarse Grained ◽  
Dual Phase

To increase transmission efficiency and reduce operation cost, dual-phase (DP) steels have been considered for pipeline applications. Welding has to be involved in such applications, which would cause a localized alteration of materials and cause many potential fatigue issues to arise under cyclic loading. In this work, the fatigue crack propagation and fatigue life of simulated heat-affected zone (HAZ) were examined. Results indicate that when the maximum stress is at the same magnitude, the fatigue life at a peak temperature of 1050 °C is very close to that of a peak temperature of 850 °C, and both of them are higher than that of a peak temperature of 1350 °C. The changes in da/dN with ΔK for HAZ subregions are attributed to the variation of crack path and fracture mode during the crack propagation. The fatigue cracks may propagate along the bainite lath preferentially in coarse-grained HAZ (CGHAZ), and the prior austenite grain boundaries can change the crack growth direction. A considerable amount of highly misoriented grain boundaries in fine-grained HAZ (FGHAZ) and intercritical-grained HAZ (ICHAZ) increase the crack growth resistance. The difference of fatigue crack propagation behavior in HAZ subregions between actual and simulated welded joints was also discussed.

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