Effects of oxygen content on microstructure and impact toughness of high heat input flux-cored wire weld metals

2018 ◽  
Vol 115 (4) ◽  
pp. 410
Author(s):  
Fengyu Song ◽  
Yanmei Li ◽  
Ping Wang ◽  
Fuxian Zhu
Keyword(s):  
Grain Size ◽  
Impact Toughness ◽  
Weld Metal ◽  
Oxygen Content ◽  
Heat Input ◽  
High Heat ◽  
Cored Wire ◽  
Weld Metals ◽  
High Heat Input ◽  
The Impact

Three weld metals with different oxygen contents were developed. The influence of oxygen contents on the microstructure and impact toughness of weld metal was investigated through high heat input welding tests. The results showed that a large number of fine inclusions were formed and distributed randomly in the weld metal with oxygen content of 500 ppm under the heat input condition of 341 kJ/cm. Substantial cross interlocked acicular ferritic grains were induced to generate in the vicinity of the inclusions, primarily leading to the high impact toughness at low temperature for the weld metal. With the increase of oxygen content, the number of fine inclusions distributed in the weld metal increased and the grain size of intragranular acicular ferrites decreased, which enhanced the impact toughness of the weld metal. Nevertheless, a further increase of oxygen content would contribute to a great diminution of the austenitic grain size. Following that the fraction of grain boundary and the start temperature of transformation increased, which facilitated the abundant formation of pro-eutectoid ferrites and resulted in a deteriorative impact toughness of the weld metal.

Impact Toughness Characteristics of SM570-TMC Steel Joint Using Welding Wire Containing 0.4% Nickel at Different Level of Heat Input

2020 ◽  
Vol 867 ◽  
pp. 117-124
Author(s):  
Herry Oktadinata ◽  
Winarto Winarto ◽  
Dedi Priadi ◽  
Eddy S. Siradj ◽  
Ario S. Baskoro
Keyword(s):  
Impact Toughness ◽  
Heat Input ◽  
High Heat ◽  
Optical Microscope ◽  
Butt Joint ◽  
Welding Wire ◽  
Steel Joint ◽  
Microstructure Observation ◽  
High Heat Input ◽  
The Impact

The study was conducted to evaluate the impact toughness of flux-cored arc welded of SM570-TMC steel joint under different heat inputs, 0.9 kJ/mm (low heat input) and 1.6 kJ/mm (high heat input). Welding wire containing 0.4%Ni was selected on this experiment. Multi-pass welds were performed on SM570-TMC steel plate of 16 mm in thickness with a single V-groove butt joint on flat position (1G). The evaluation consists of observations on microstructure using an optical microscope and SEM-EDS, and mechanical properties including tensile, microhardness Vickers and Charpy V-notch (CVN) impact test at temperatures of 25, 0 and-20 °C. Results showed that the impact toughness of the base metal (BM) was higher than the weld metal (WM) at all test temperatures. Hardness and impact toughness of WM at low heat input was observed higher than when applied a high heat input. The welded samples at low and high heat inputs had high of tensile strength, and the fracture seemly occurs on the BM. Microstructure observation showed that at a high heat input, larger grains and microsegregation were observed. It might affect on decreasing their impact property.

Effect of Heat Input on Impact Toughness of Coarse-Grained Heat-Affected Zone of a Nb-Ti Microalloyed Pipeline Steel

2012 ◽  
Vol 538-541 ◽  
pp. 2026-2031 ◽  
Author(s):  
Zhou Gao ◽  
Ran Wei ◽  
Kai Ming Wu
Keyword(s):  
Impact Toughness ◽  
Heat Affected Zone ◽  
Heat Input ◽  
Pipeline Steel ◽  
High Heat ◽  
Coarse Grained ◽  
Bainitic Microstructure ◽  
Homogenous Distribution ◽  
High Heat Input ◽  
The Impact

The effect of varying heat inputs (20, 100, 200 kJ/cm) on the microstructures and toughness of the simulated coarse-grained heat-affected zone of a Nb-Ti microalloyed pipeline steel were investigated utilizing optical and electron microscope. Results showed that the impact toughness of the coarse-grained heat-affected zone maintained a higher level at the heat input of 20 and 100 kJ/cm, whereas it dropped to a much lower level at the heat input of 200 kJ/cm. The good toughness was attributed to the grain refinement and the homogenous distribution of fine and elongated martensite/austenite constituents. The deterioration of toughness for high heat input simulated welding was mainly caused by the coarse bainitic microstructure and massive martensite/austenite constituents.

Microstructure and Impact Toughness of Flux-Cored Arc Welded SM570-TMC Steel at Low and High Heat Input

2020 ◽  
Vol 991 ◽  
pp. 3-9
Author(s):  
Herry Oktadinata ◽  
Winarto Winarto ◽  
Eddy S. Siradj
Keyword(s):  
Low Temperature ◽  
Impact Toughness ◽  
Base Metal ◽  
Heat Input ◽  
Charpy Impact ◽  
Cored Wire ◽  
Average Heat ◽  
Weld Metals ◽  
Flux Cored Arc Welding ◽  
The Impact

This work investigated microstructure and impact toughness of multi-pass flux-cored arc welded SM570-TMC steel. A comparison was made between weldments fabricated with average heat input of 0.9 kJ/mm and 1.4 kJ/mm, respectively. SM570 steel plate with 16 mm nominal thickness and 1.2 mm diameter of E81-Ni1 flux-cored wire were selected in this experiment. Multi-pass flux-cored arc welding (FCAW) was performed using carbon dioxide shielding gas. Then the weldments were observed using optical microscopy, scanning electron microscope (SEM) and electron probe micro analyzer (EPMA). The steel joint strength was measured via tensile test, and Charpy impact test was performed at three different test temperatures. The microstructure observation exhibited the base metal mainly consist of ferrite and pearlite features, while the weld metal contained the acicular ferrites, polygonal ferrites and M-A constituent at both different heat inputs. The impact toughness of base metal is superior than weld metals. The weld metals fabricated at average heat input of 0.9 kJ/mm have a higher low temperature impact toughness than using heat input of 1.4 kJ/mm. The acicular ferrites amount that significant reduced at the higher heat input may degrade the toughness at low temperature.

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.

High Heat Input Welding of 12Cr-6Ni-2.5Mo Supermartensitic Stainless Steel

2003 ◽  
Author(s):  
Ragnhild Aune ◽  
Hans Fostervoll ◽  
Odd Magne Akselsen
Keyword(s):  
Weld Metal ◽  
Stainless Steels ◽  
Heat Affected Zone ◽  
Heat Input ◽  
High Heat ◽  
Maximum Heat ◽  
Final Microstructure ◽  
Girth Welding ◽  
High Heat Input ◽  
Longitudinal Seam

In conventional welding of 13% Cr supermartensitic stainless steels, the normal microstructure that forms on cooling is martensite. Although high heat input tends to give a certain coarsening of the final microstructure, the eventual accompanying loss in toughness is not known. The present study was initiated to examine the effect of heat input on weld metal and heat affected zone mechanical properties of a 12Cr-6Ni-2.5Mo grade. The results obtained showed that the notch toughness is low (25 J) and independent of heat input for the weld metal, while it is reduced with increasing heat input for fusion line and the heat affected zone locations. Subsequent post weld heat treatment gave a substantial increase in toughness for all notch locations. Based on these results, indications are that a specified maximum heat input is not applicable in welding of supermartensitic stainless steels, allowing more production efficient techniques to be used, both in longitudinal seam and girth welding.

Impact Toughness for PM HIP 316L at Cryogenic Temperatures

2016 ◽  
Author(s):  
Tomas Berglund ◽  
Martin Östlund
Keyword(s):  
Grain Size ◽  
Impact Toughness ◽  
Oxygen Content ◽  
Room Temperature ◽  
Hot Isostatic Pressing ◽  
Cryogenic Temperatures ◽  
Inclusion Content ◽  
Conventional Material ◽  
The Impact ◽  
Suggested Explanation

It is well known throughout the PM HIP (Powder Metallurgy Hot Isostatic Pressing) industry that PM HIPed 316L material in general exhibit higher strength than conventional 316L. However, previous studies have shown an uncharacteristic behavior in impact toughness properties at cryogenic temperatures compared to conventional forged material. The uncharacteristic behavior consists of unexpectedly large drop in impact toughness at cryogenic temperatures which is not seen in the same extent in conventional material e.g. forged 316L. With the recent code case approval for PM HIPed 316L material, this behavior can be seen as an uncertainty regarding the performance of the material and its use in nuclear applications can therefore become limited. The behavior and underlying mechanisms is yet to be explained in detail. One possible explanation is that it is caused by oxides in the material, of which a large amount originates from oxygen picked up by the very large surface area of the powder during the manufacturing process. The correlation between impact toughness at room temperature and oxygen content is often referred to. In this study the non-metallic inclusion content is correlated to the impact properties at −196°C (−321°F), and a suggested explanation for the behavior of PM HIP 316L/316LN vs. conventional 316L is presented. The size and number of inclusions constitutes a major difference between the PM HIPed and conventional material. The results show that the size of the inclusions is significantly smaller in the PM materials compared to the conventional material and as a consequence they are present in larger numbers in the PM materials. Furthermore, the results clearly show the correlation between inclusion content and the impact toughness at cryogenic temperatures. The correlation is not as clear at room temperature where the different materials behave more similar. The suggested explanation is further supported by literature on cryogenic properties of 316L/316LN, 316L weld material and PM HIP 316LN with greatly reduced oxygen content. The impact toughness testing was performed using instrumented test equipment capable of recording load vs. displacement during testing. From this data the crack propagation and crack initiation energy can be estimated. Furthermore, it is known that grain size can influence mechanical properties. In this study no clear relationship between impact toughness and grain size could be observed. However, a correlation between the grain size and the amount of inclusions in the material was observed. It was found that larger amounts of inclusions in the PM HIPed material are correlated to a finer grain size. The results indicate that the inclusion particles inhibit grain growth during the HIP and heat treatment process by pinning of grain boundaries.

scholarly journals The influence of the oxygen equivalent in a gas-mixture on the structure and toughness of microalloyed steel weldments

2006 ◽  
Vol 71 (3) ◽  
pp. 313-321 ◽  
Author(s):  
Radica Prokic-Cvetkovic ◽  
Andjelka Milosavljevic ◽  
Aleksandar Sedmak ◽  
Olivera Popovic
Keyword(s):  
Impact Toughness ◽  
Crack Propagation ◽  
Weld Metal ◽  
Acicular Ferrite ◽  
Microalloyed Steel ◽  
Gas Mixtures ◽  
Gas Mixture ◽  
Weld Metals ◽  
Maximum Crack ◽  
The Impact

Testing were carried out on two steels. The first was microalloyed with Nb and second with Ti, Nb and V. The impact toughness of weld metals of these steels was evaluated using an instrumented Charpy pendulum. Five different gas mixtures (Ar, CO2, O2) were used to determine the optimal gas shielded metal arc process for both steels. The oxygen equivalent was used as a representative parameter of a mixture to follow, in particularly, its effect on the microstructure, toughness and crack propagation energy of the weld metal. For these investigated steels, the optimum gas mixture was established (5%CO2, 0.91%O2, balance Ar), which provided the maximum crack propagation energy, due to the microstructure which consisted dominantly of acicular ferrite.

scholarly journals Effect of Ferritic Morphology on Yield Strength of CGHAZ in a Low Carbon Mo-V-N-Ti-B Steel

Metals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1863
Author(s):  
Leping Wang ◽  
Huibing Fan ◽  
Genhao Shi ◽  
Qiuming Wang ◽  
Qingfeng Wang ◽  
...  
Keyword(s):  
Yield Strength ◽  
Heat Input ◽  
Low Carbon Steel ◽  
High Heat ◽  
Coarse Grained ◽  
Granular Bainite ◽  
Low Carbon ◽  
Fine Grained ◽  
High Heat Input ◽  
The Impact

For investigating the impact of ferritic morphology on yield strength (YS) of the high-heat-input welding induced coarse-grained heat-affected zone (CGHAZ) of a low carbon Mo-V-N-Ti-B steel, a group of particular welding heat inputs were designed to obtain different ferritic microstructures in CGHAZ. The tensile properties were estimated from typical samples with ferritic microstructures. The mixed microstructures dominated by the intragranular polygonal ferrite (IGPF), the intragranular acicular ferrite (IGAF), and the granular bainite (GB) were obtained at the heat inputs of 35, 65, 85 and 120 kJ/cm, respectively. When the main microstructure changed from IGPF to IGAF and GB, YS increased first and then decreased. The microstructure consisting mainly of IGAF possessed the maximum YS. As the main microstructure changed from IGPF to IGAF and GB, the contribution of grain refinement strengthening to YS was estimated to be elevated remarkably. This means the strength of CGHAZ in a low-carbon steel subjected to the high-heat-input welding could be enhanced by promoting the fine-grained AF and GB formation.

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