scholarly journals Improvement of stress-relief cracking resistance in coarse-grained heat-affected zone of T23 steel by refining sub-structure through second thermal cycle

2020 ◽  
Vol 9 (4) ◽  
pp. 8568-8579
Author(s):  
Yong Li ◽  
Jiaqing Wang ◽  
Xue Wang
Keyword(s):  
Heat Affected Zone ◽  
Thermal Cycle ◽  
Stress Relief ◽  
Coarse Grained ◽  
Cracking Resistance

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.

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.

scholarly journals Role of Reversed Austenite Behavior in Determining Microstructure and Toughness of Advanced Medium Mn Steel by Welding Thermal Cycle

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2127 ◽  
Author(s):  
Yunxia Chen ◽  
Honghong Wang ◽  
Huan Cai ◽  
Junhui Li ◽  
Yongqing Chen
Keyword(s):  
Grain Size ◽  
Impact Toughness ◽  
Significant Role ◽  
Heat Affected Zone ◽  
Martensite Transformation ◽  
Thermal Cycle ◽  
Retained Austenite ◽  
Coarse Grained ◽  
Reversed Austenite ◽  
Austenite Transformation

Reversed austenite transformation behavior plays a significant role in determining the microstructure and mechanical properties of heat affected zones of steels, involving the nucleation and growth of reversed austenite. Confocal Laser Scanning Microscope (CLSM) was used in the present work to in situ observe the reversed austenite transformation by simulating welding thermal cycles for advance 5Mn steels. No thermal inertia was found on cooling process after temperature reached the peak temperature of 1320 °C. Therefore, too large grain was not generated in coarse-grained heat-affected zone (CGHAZ). The pre-existing film retained austenite in base metal and acted as additional favorable nucleation sites for reversed austenite during the thermal cycle. A much great nucleation number led to the finer grain in the fine-grained heat-affected zone (FGHAZ). The continuous cooling transformation for CGHAZ and FGHAZ revealed that the martensite was the main transformed product. Martensite transformation temperature (Tm) was higher in FGHAZ than in CGHAZ. Martensite transformation rate was higher in FGHAZ than in CGHAZ, which is due to the different grain size and assumed atom (Mn and C) segregation. Consequently, the softer martensite was measured in CGHAZ than in FGHAZ. Although 10~11% austenite retained in FGHAZ, the possible Transformation Induced Plasticity (TRIP) effect at −60 °C test temperature may lower the impact toughness to some degree. Therefore, the mean absorbed energy of 31, 39 and 42 J in CGHAZ and 56, 45 and 36 J in FGHAZ were exhibited at the same welding heat input. The more stable retained austenite was speculated to improve impact toughness in heat-affected zone (HAZ). For these 5Mn steels, reversed austenite plays a significant role in affecting impact toughness of heat-affected zones more than grain size.

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.

Correlation between dislocation, grain boundary and interface of duplex SS in stress corrosion cracking(SCC)

1990 ◽  
Vol 48 (4) ◽  
pp. 928-929
Author(s):  
Wang Zheng-fang ◽  
Z.F. Wang
Keyword(s):  
Stainless Steel ◽  
Thermal Cycle ◽  
Secondary Phase ◽  
Corrosion Cracking ◽  
Coarse Grained ◽  
Test Environment ◽  
Fine Grained ◽  
Evaluation Test ◽  
Welding Thermal Cycle ◽  
Micro Analysis

The main purpose of this study highlights on the evaluation of chloride SCC resistance of the material,duplex stainless steel,OOCr18Ni5Mo3Si2 (18-5Mo) and its welded coarse grained zone(CGZ).18-5Mo is a dual phases (A+F) stainless steel with yield strength:512N/mm2 .The proportion of secondary Phase(A phase) accounts for 30-35% of the total with fine grained and homogeneously distributed A and F phases(Fig.1).After being welded by a specific welding thermal cycle to the material,i.e. Tmax=1350°C and t8/5=20s,microstructure may change from fine grained morphology to coarse grained morphology and from homogeneously distributed of A phase to a concentration of A phase(Fig.2).Meanwhile,the proportion of A phase reduced from 35% to 5-10°o.For this reason it is known as welded coarse grained zone(CGZ).In association with difference of microstructure between base metal and welded CGZ,so chloride SCC resistance also differ from each other.Test procedures:Constant load tensile test(CLTT) were performed for recording Esce-t curve by which corrosion cracking growth can be described, tf,fractured time,can also be recorded by the test which is taken as a electrochemical behavior and mechanical property for SCC resistance evaluation. Test environment:143°C boiling 42%MgCl2 solution is used.Besides, micro analysis were conducted with light microscopy(LM),SEM,TEM,and Auger energy spectrum(AES) so as to reveal the correlation between the data generated by the CLTT results and micro analysis.

scholarly journals Effect of Intermetallic Compound Bridging on the Cracking Resistance of Sn2.3Ag Microbumps with Different UBM Structures under Thermal Cycling

Metals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1065
Author(s):  
Chun-Chieh Mo ◽  
Dinh-Phuc Tran ◽  
Jing-Ye Juang ◽  
Chih Chen
Keyword(s):  
Electron Microscope ◽  
Intermetallic Compound ◽  
Thermal Cycling ◽  
Thermal Cycle ◽  
Crack Formation ◽  
Thermal Cycling Test ◽  
Under Bump Metallization ◽  
Reflow Time ◽  
Cracking Resistance ◽  
Scanning Electron

In this study, the effect of intermetallic compound (IMC) bridging on the cracking resistance of microbumps with two different under bump metallization (UBM) systems, Cu/solder/Cu and Cu/solder/Ni, under a thermal cycling test (TCT) is investigated. The height of the Sn2.3Ag solders was ~10 µm, which resembles that of the most commonly used microbumps. We adjusted the reflow time to control the IMC bridging level. The samples with different bridging levels were tested under a TCT (−55–125 °C). After 1000 and 2000 TCT cycles (30 min/cycle), the samples were then polished and characterized using a scanning electron microscope (SEM). Before IMC bridging, various cracks in both systems were observed at the IMC/solder interfaces after the 1000-cycle tests. The cracks propagated as cyclic shapes from the sides to the center and became more severe as the thermal cycle was increased. With IMC bridging, we could not observe any further failure in all the samples even when the thermal cycle was up to 2000. We discovered that IMC bridging effectively suppressed crack formation in microbumps under TCTs.

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