scholarly journals Effect of Welding Peak Temperature on Microstructure and Impact Toughness of Heat-Affected Zone of Q690 High Strength Bridge Steel

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2981
Author(s):  
Yue Zhang ◽  
Jun Xiao ◽  
Wei Liu ◽  
Aimin Zhao
Keyword(s):  
Impact Toughness ◽  
Heat Affected Zone ◽  
Lath Martensite ◽  
Testing Machine ◽  
High Strength ◽  
Peak Temperature ◽  
Granular Bainite ◽  
Fine Grain ◽  
Bridge Steel ◽  
The Impact

The effect of peak temperature (TP) on the microstructure and impact toughness of the welding heat-affected zone (HAZ) of Q690 high-strength bridge steel was studied using a Gleeble-3500 thermal simulation testing machine. The results show that the microstructure of the inter critical heat-affected zone (ICHAZ) was ferrite and bainite. The microstructure of fine grain heat-affected zone (FGHAZ) and coarse grain heat-affected zone (CGHAZ) was lath bainite (LB) LB, lath martensite (LM), and granular bainite (GB), but the microstructure of FGHAZ was finer. With the increase in peak temperature, the content of LB and GB decreased, the content of LM increased, and the lath bundles of LM and LB gradually became coarser. With the increase in peak temperature, the grain size of the original austenite increased significantly, and the impact toughness decreased significantly. When the peak temperature was 800 °C, the toughness was the best. For CGHAZ, the peak temperature should be less than 1200 °C to avoid excessive growth of grain and reduction of mechanical property.

Effect of Welding Processes with High Heat Input on the Microstructure and Toughness of Coarse-Grained Heat-Affected Zone of a High-Strength High-Toughness Steel

2018 ◽  
Vol 937 ◽  
pp. 61-67
Author(s):  
Yu Jie Li ◽  
Jin Wei Lei ◽  
Xuan Wei Lei ◽  
Oleksandr Hress ◽  
Kai Ming Wu
Keyword(s):  
Low Temperature ◽  
Impact Toughness ◽  
Heat Affected Zone ◽  
Heat Input ◽  
High Strength ◽  
High Heat ◽  
Coarse Grained ◽  
Low Temperature Impact Toughness ◽  
The Impact ◽  
Welding Processes

Utilizing submerged arc welding under heat input 50 kJ/cm on 60 mm thick marine engineering structure plate F550, the effect of preheating and post welding heat treatment on the microstructure and impact toughness of coarse-grained heat-affected zone (CGHAZ) has been investigated. The original microstructure of the steel plate is tempered martensite. The yield and tensile strength is 610 and 660 MPa, respectively. The impact absorbed energy at low temperature (-60 °C) at transverse direction reaches about 230~270 J. Welding results show that the preheating at 100 °C did not have obvious influence on the microstructure and toughness; whereas the tempering at 600 °C for 2.5 h after welding could significantly reduce the amount of M-A components in the coarse-grained heat-affected zone and thus improved the low temperature impact toughness.

scholarly journals Impact Toughness of Gas Metal Arc Welded HY-80 Steel Plate at Sub-zero Temperatures

2019 ◽  
Vol 269 ◽  
pp. 06003
Author(s):  
Herry Oktadinata ◽  
Winarto Winarto
Keyword(s):  
Impact Toughness ◽  
Weld Joint ◽  
Heat Affected Zone ◽  
High Strength Steel ◽  
Steel Plate ◽  
Gas Metal Arc Welding ◽  
High Strength ◽  
Coarse Grain ◽  
Fracture Appearance ◽  
The Impact

Various welding methods are widely applied in large fabrication of high strength steel. However, commonly the problem occurs where a coarse grain is formed near fusion zone causing reduce the impact toughness due to the weld joint become brittle. Ductility and toughness in a coarse grain heat affected zone (CGHAZ) is low due to the formation of coarsening grain size. The objective of this research is to investigate the microstructure evolution, impact toughness and fracture appearance at sub-zero temperatures of the high strength steel arc welded. The steel that used in this experiment is a HY-80 steel welded by gas metal arc welding (GMAW) with a mixture of argon and carbon dioxide (90%Ar and 10%CO2) and ER100S solid wire. Microstructure observation and Charpy V-notch (CVN) tests were performed on the weld joint which consist of base metal (BM), heat affected zone (HAZ), and weld metal (WM). The CVN tests on the HY-80 steel plate at various temperatures (20, -20, -60 and -80 °C) show impact toughness decrease when the test temperature decrease. The CVN tests on the HY-80 weld joint at a temperature of 80 °C show the lowest impact toughness was measured at WM (61 J) and followed fusion line-FL (101 J) with brittle fracture appearance.

Mechanical Behaviour of Intercritically Reheated Coarse-Grained Heat Affected Zone in High Strength Line Pipe Steels

2018 ◽  
Author(s):  
Madhumanti Mandal ◽  
Warren J. Poole ◽  
Thomas Garcin ◽  
Matthias Militzer ◽  
Laurie Collins
Keyword(s):  
Impact Toughness ◽  
Heat Affected Zone ◽  
Welding Process ◽  
Charpy Impact ◽  
High Strength ◽  
Coarse Grained ◽  
Fracture Mechanisms ◽  
Line Pipe ◽  
Secondary Cracks ◽  
The Impact

Multipass welding of high strength steels used for fabrication and joining of transmission pipelines presents a number of metallurgical challenges. A key concern is both the strength and toughness of the heat affected zone (HAZ) adjacent to both seam and girth welds. In this work, a systematic study has been conducted on regions of the heat affected zone in the base metal where the first welding pass produces a thermal excursion which results in a coarse-grained heat affected zone (CGHAZ). The subsequent weld pass involves intercritical annealing of this region, i.e. a microstructure associated with intercritically reheated coarse grain heat affected zone (ICCGHAZ). The small ICCGHAZ region is often identified as being particularly susceptible to crack initiation. This work was undertaken to understand microstructure development in this zone and how the ICCGHAZ may affect the overall performance of the HAZ. Gleeble thermomechanical simulations have been conducted to produce bulk samples representative of different welding scenarios. Charpy impact tests and tensile tests have been performed over a range of temperatures. It was found that when a continuous necklace of martensite-austenite islands form on the prior austenite grain boundaries (i.e. for a M/A fraction of ≈10%), the Charpy impact toughness energy is dramatically decreased and the ductile brittle transition temperature is significantly raised. Detailed studies on the secondary cracks have been conducted to examine the fracture mechanisms in the different microstructures. The results show that the lower bainite microstructures obtained after the 1st thermal treatment, representative of CGHAZ have excellent impact properties. The impact toughness of the microstructures typical of ICCGHAZ is strongly dependent on the composition as well as morphology and spatial distribution of the resulting martensite-austenite (M/A) islands transformed from inter-critically formed austenite. This zone can play a significant role in fracture initiation and thus needs to be considered in alloy and welding process designs.

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.

The Basic Research and Application on Hot Forming of High Strength Steel

2013 ◽  
Vol 800 ◽  
pp. 280-283
Author(s):  
Fu Li Lu ◽  
Ji Shun Song ◽  
Jian Zhang ◽  
Xiu Ping Yan
Keyword(s):  
Process Parameters ◽  
High Strength Steel ◽  
Lath Martensite ◽  
Testing Machine ◽  
Basic Research ◽  
High Strength ◽  
Hot Forming ◽  
Tensile Testing Machine ◽  
Hardness Tester ◽  
The Impact

Taking the high-strength steel 22MnB5 as the research object, starting from the phase transformation and the performance of the sheet at high temperature, the impact of various process parameters on the part was studied, pressing the stringers with hot forming technology simultaneously. Using metallurgical microscope, hardness tester and universal tensile testing machine, the microstructure and mechanical properties of the parts were analysed. The result show that, under the selected process parameters, the microstructure of the workpiece is desired lath martensite, the hardness is above 450HV, the tensile strength is above 1450MPa, which meet the production requirements.

scholarly journals Low Temperature Deformation Induced Microstructure Refinement and Consequent Ultrahigh Toughness of a 20Mn2SiCrNi Bainitic Steel

Metals ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 19 ◽  
Author(s):  
Yu Tian ◽  
Zhunli Tan ◽  
Ji Li ◽  
Bo Gao ◽  
Min Zhang ◽  
...  
Keyword(s):  
Grain Size ◽  
Impact Toughness ◽  
High Strength Steel ◽  
High Strength ◽  
Granular Bainite ◽  
Temperature Deformation ◽  
Air Cooling ◽  
Degree Of Deformation ◽  
Lower Temperature ◽  
The Impact

In this paper, we have studied the influence of deformation on the microstructure and mechanical properties of 20Mn2SiCrNi bainitic high strength steel processed through a hot rolling route. Simulation of different temperatures and degrees of deformation was carried out via Gleeble-1500. The study suggested that grain size is refined when the deformation is carried out at lower temperature (> Ac3). When the degree of deformation was increased from 20% to 60%, grain size and microstructure were both refined and the size of retained austenite was reduced. The tensile strength increased from 1345 MPa to 1432 MPa. The impact toughness increased from 115 J/cm2 to 210 J/cm2 at room temperature, from 63 J/cm2 to 142 J/cm2 at −40 °C. Furthermore, it was observed that the microstructure after air cooling was composed of granular bainite (GB), lath bainite (LB) and martensite/austenite (MA) island for different deformation conditions. The study reveals that the impact toughness of 20Mn2SiCrNi bainitic high strength steel can be increased by increasing the degree of deformation.

Microstructures and Toughness in Simulated Coarse Grain Heat-Affected Zones of Copper-Bearing Steel

2008 ◽  
Vol 575-578 ◽  
pp. 910-914
Author(s):  
Wen Yan Liu ◽  
Lai Wang ◽  
Ji Bin Liu ◽  
Ping He Li ◽  
Kai Miao ◽  
...  
Keyword(s):  
Impact Toughness ◽  
Heat Affected Zone ◽  
Physical Simulation ◽  
Bearing Steel ◽  
Granular Bainite ◽  
Coarse Grain ◽  
Factors Influencing ◽  
Visible Effect ◽  
Main Factors ◽  
The Impact

Microstructures and toughness of simulated coarse grain heat-affected zone of hot continuously rolled copper-bearing steel were investigated using physical simulation. The results showed that brittlement is easy to happen in the region of CGHAZ with slower thermal cycles (t8/5≥45s). Granular bainite transformed from austenite led to brittlement. The dimensions of granular martensite and austenite (M-A) constituents are main factors influencing the impact toughness. There is no visible effect on the toughness when the dimensions of M-A constituents are less than 1μ m. However, the toughness decreases greatly once the dimensions exceed 1μ m. Therefore, decreasing the dimensions of M-A constituents by controlling weld heat input will do good to improve the impact toughness of copper-bearing steel.

scholarly journals Effect of Welding Thermal Cycles on Microstructure and Mechanical Properties of Simulated Heat Affected Zone for a Weldox 1300 Ultra-High Strength Alloy Steel

2016 ◽  
Vol 61 (1) ◽  
pp. 127-132 ◽  
Author(s):  
M. St. Węglowski ◽  
M. Zeman ◽  
A. Grocholewski
Keyword(s):  
Mechanical Properties ◽  
Impact Toughness ◽  
Heat Affected Zone ◽  
High Strength Steel ◽  
High Strength ◽  
Parent Material ◽  
Cooling Time ◽  
Microstructure And Mechanical Properties ◽  
Ultra High Strength Steel ◽  
The Impact

In the present study, the investigation of weldability of ultra-high strength steel has been presented. The thermal simulated samples were used to investigate the effect of welding cooling time t8/5 on microstructure and mechanical properties of heat affected zone (HAZ) for a Weldox 1300 ultra-high strength steel. In the frame of these investigation the microstructure was studied by light and transmission electron microscopies. Mechanical properties of parent material were analysed by tensile, impact and hardness tests. In details the influence of cooling time in the range of 2,5 ÷ 300 sec. on hardness, impact toughness and microstructure of simulated HAZ was studied by using welding thermal simulation test. The microstructure of ultra-high strength steel is mainly composed of tempered martensite. The results show that the impact toughness and hardness decrease with increase of t8/5 under condition of a single thermal cycle in simulated HAZ. The increase of cooling time to 300 s causes that the microstructure consists of ferrite and bainite mixture. Lower hardness, for t8/5 ≥ 60 s indicated that low risk of cold cracking in HAZ for longer cooling time, exists.

scholarly journals Effects of Small Ni Addition on the Microstructure and Toughness of Coarse-Grained Heat-Affected Zone of High-Strength Low-Alloy Steel

Metals ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 718 ◽  
Author(s):  
Gang Huang ◽  
Xiangliang Wan ◽  
Kaiming Wu ◽  
Huazhong Zhao ◽  
Raja Misra
Keyword(s):  
Impact Toughness ◽  
Alloy Steel ◽  
Heat Affected Zone ◽  
High Strength ◽  
Coarse Grained ◽  
Low Alloy Steel ◽  
Ni Content ◽  
Ni Addition ◽  
Bainitic Microstructure ◽  
The Impact

The objective of the present study is to investigate the effects of nickel (Ni) on the microstructure and impact toughness of coarse-grained heat-affected zone (CGHAZ) of high-strength low-alloy steel. It was observed that the microstructure of CGHAZ predominantly consisted of bainite and a small proportion of martensite-austenite (M-A) constituents and acicular ferrite (AF). With increased Ni content, the percentage of M-A constituent decreased and AF increased; consequently, the impact toughness of CGHAZ increased. The study revealed that a small addition of nickel significantly affected the formation of M-A constituents and AF; however, no obvious influence was observed on the bainitic microstructure of high-strength low-alloy steel.

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