Analysis of the Effect of Mechanical Oscillations Generated during Welding on the Structure of Ductile Constituent of Products Made of Steel 10G2FB

2021 ◽  
Vol 1038 ◽  
pp. 40-48
Author(s):  
Bohdan Tsymbal ◽  
Kyrylo Ziborov ◽  
Nataliia Rott ◽  
Sergey Fedoryachenko
Keyword(s):  
Weld Metal ◽  
Diffusion Processes ◽  
Mechanical Vibrations ◽  
Mechanical Oscillations ◽  
Welding Processes

Under open construction, the requirements to welding processes are very critical since reliable connections requires complex, costly and sometimes impossible processes that involve fixed machines and devices. Therefore, in such cases it is important to carry out welding work using mechanical vibrations. Elastic oscillations in the weld metal result in uniform crystallization of the melt and formation of a dispersed structure. This also results in enhancement of diffusion processes while promoting degassing process in weld metal.

Mechanical Approach for Prediction of Microcracking in Multipass Weld Metal of Ni-Base Alloy 690

2008 ◽  
Vol 580-582 ◽  
pp. 1-4 ◽  
Author(s):  
Kazuyoshi Saida ◽  
Masashi Sakamoto ◽  
Kazutoshi Nishimoto
Keyword(s):  
Plastic Strain ◽  
Weld Metal ◽  
Base Alloy ◽  
Multipass Welding ◽  
Cooling Stage ◽  
Alloy 690 ◽  
Mechanical Approach ◽  
Multipass Weld ◽  
Welding Processes ◽  
Reheating Process

The occurrence of microcracks, especially ductility-dip crack in multipass weld metal during GTAW and laser overlay welding processes of Ni-base alloy 690 was predicted by the mechanical approach. The stress/strain analysis in multipass welds was conducted using the thermo elasto-plastic finite element method. The brittle temperature range for ductility-dip cracking (DTR) of the reheated weld metal was determined by the Varestraint test. Plastic strain in the weld metal accumulated with applying the weld thermal cycle in multipass welding. The plastic strain-temperature curve in the La free weld metal did not cross the DTR in the cooling stage of GTAW process, however, it crossed the DTR in the cooling stage of reheating process by subsequent welding. On the other hand, the plastic strain-temperature curves of any weld passes in the La added weld metal did not cross the DTR. Ductility-dip cracks occurred in the La free weld metal except for the final layer, however, any ductility-dip cracks did not occur in the La added weld metal during multipass welding. It could be understood that ductility-dip crack would occur during not only single-pass welding but also multipass welding when plastic strain intersected the DTR.

scholarly journals Welding Soundness of a Thick-Walled 9Cr-1Mo Steel

2010 ◽  
Vol 654-656 ◽  
pp. 408-411
Author(s):  
Woo Seog Ryu ◽  
Sung Ho Kim ◽  
Dae Whan Kim
Keyword(s):  
Mechanical Properties ◽  
Weld Metal ◽  
Base Metal ◽  
Hardness Test ◽  
Ultimate Tensile Stress ◽  
Narrow Gap ◽  
Martensitic Steels ◽  
Narrow Gap Welding ◽  
Self Energy ◽  
Welding Processes

High Cr ferritic/martensitic steels are demanded to join using favorable welding processes with economical and metallurgical advantages in order to apply to the thick-walled reactor pressure vessel of a very high temperature gas cooled reactor. Narrow gap welding technology was adopted to weld a thick-walled 9Cr-1Mo-1W steel with thickness of 110mm. The welding integrity was checked by non-destructive examination, optical microscopy and hardness test, and the homogeneity through welding depth was checked by absorbed impact energy and tensile strength. The optimizing welding conditions resulted that a narrow U-grooved gap with almost parallel edges was sound in actual practice, and the coarse grain zone was minimized in the heat affected zone. The absorbed energy of 75±25 J through welding depth was acceptable in scatter band to check the uniformity through the welding depth. The ultimate tensile stress and yield stress were about the same through welding depth at 650±10 MPa and 500±10 MPa, indicating no difference through welding depth. Elongation was also almost same through depth, and the fracture surface was appeared as a normal. The weld metal had similar mechanical properties to base metal. The upper self energy of weld metal was 194J, and the ductile-brittle transition temperature was 30°C. The tensile behavior was the typical trend with temperature, and YS and UTS of weldment were slightly higher than base metal by nearly below 10%. Thus, it concluded that the soundness of the narrow gap welding of a thick-walled 9Cr-1Mo-1W steel was confirmed in terms of the welding uniformity through the depth and mechanical properties.

scholarly journals The State of the Art of Underwater Wet Welding Practice: Part 1

2021 ◽  
Vol 100 (4) ◽  
pp. 132-141
Author(s):  
EZEQUIEL CAIRES PEREIRA PESSOA ◽  
◽  
STEPHEN LIU
Keyword(s):  
Research And Development ◽  
Weld Metal ◽  
Arc Welding ◽  
Structural Steels ◽  
Friction Stir ◽  
Underwater Wet Welding ◽  
Class A ◽  
Metal Arc Welding ◽  
Flux Cored Arc Welding ◽  
Welding Processes

Developments in underwater wet welding (UWW) over the past four decades are reviewed, with an emphasis on the research that has been conducted in the last ten years. Shielded metal arc welding with rutile-based coated electrodes was established as the most applied process in the practice of wet welding of structural steels in shallow water. The advancements achieved in previous decades had already led to control of the chemical com-position and microstructure of weld metals. Research and development in consumables formulation have led to control of the amount of hydrogen content and the level of weld porosity in the weld metal. The main focus of research and development in the last decade was on weldability of naval and offshore structural steels and acceptance of welding procedures for Class A weld classification according to American Welding Society D3.6, Under-water Welding Code. Applications of strictly controlled welding techniques, including new postweld heat treatment procedures, allowed for the welding of steels with carbon equivalent values greater than 0.40. Classification societies are meticulously scrutinizing wet welding procedures and wet weld properties in structural steels at depths smaller than 30 m prior to qualifying them as Class A capable. Alternate wet welding processes that have been tested in previous decades — such as friction stir welding, dry local habitat, and gas metal arc welding —have not achieved great success as originally claimed. Al-most all of the new UWW process developments in the last decade have focused on the flux cored arc welding (FCAW) process. Part 1 of this paper covers developments in microstructural optimization and weld metal porosity control for UWW. Part 2 discusses the hydrogen pickup mechanism, weld cooling rate control, design, and qualification of consumables. It ends with a description of the advancements in FCAW applications for UWW.

Decisive impact of Filler-free joining processes on the Microstructural evolution, tensile and impact properties of 9Cr-1Mo-V-Nb to 316 L(N) dissimilar joints

2021 ◽  
pp. 095440622110293
Author(s):  
A Venkatakrishna ◽  
AK Lakshminarayanan ◽  
P Vasantharaja ◽  
M Vasudevan
Keyword(s):  
Weld Metal ◽  
Laser Beam Welding ◽  
Carbon Diffusion ◽  
Comparative Investigation ◽  
Impact Testing ◽  
Dissimilar Joints ◽  
Friction Stir ◽  
Dissimilar Weld ◽  
Transverse Tensile ◽  
Welding Processes

Filler-free (FF) welding processes namely, Activated Tungsten Inert Gas welding (ATIG), Laser Beam Welding (LBW), and Friction Stir Welding (FSW) were utilized for joining the nuclear grade 9Cr-1Mo-V-Nb ferritic-martensitic steel and 316 L(N) austenitic stainless steel. A comparative investigation was made by assessing the weld geometries, metallurgical features, material mixing proportions, carbon diffusion behaviour, and mechanical properties of the post-weld heat-treated (PWHT) dissimilar weld joints. Geometries of the weld zones were observed with the transverse and longitudinal macrographs. Metallurgical features were examined by optical microscopy (OM) and Scanning electron microscopy (SEM). Three-phase microstructures were identified in the dissimilar weld zones (DWZ). The elemental distributions were identified by Energy-dispersive X-ray spectroscopy (EDAX). The mixing proportions of the dissimilar alloys and the formation of δ-ferrite in the dissimilar heat-affected zones (HAZ) and DWZ were analytically quantified. Moreover, the diffusion activity of carbides/interstitial carbon atoms was examined by Secondary ion mass spectroscopy (SIMS). In the FSW joints, the intermingled microstructures are recorded with high and stabilized hardness values as compared to the DWZ of the ATIG and LBW joints. In the transverse tensile test, all FF joints were failed at the 316 L(N) base metal (BM) region. Tensile and impact testing of all weld metal indicated that, the weld metal region of the LBW joint exhibited higher strength and lower toughness as compared to the ATIG and FSW joints. The presence of untransformed, recrystallized fine equiaxed austenite along and refined martensitic structure arranged in an alternate layers within the weld metal region of FSW joint caused the higher toughness property than the ATIG and LBW joints.

Mechanical properties and microstructural characteristics of rotating arc-gas metal arc welded carbon steel joints

2021 ◽  
Vol 30 (1) ◽  
pp. 49-58
Author(s):  
Nallasamy Sankar ◽  
Sudersanan Malarvizhi ◽  
Visvalingam Balasubramanian
Keyword(s):  
Mechanical Properties ◽  
Carbon Steel ◽  
Weld Metal ◽  
Gas Metal Arc Welding ◽  
Ferrite Matrix ◽  
Metal Arc Welding ◽  
Rotating Arc ◽  
Steel Joints ◽  
Welding Processes ◽  
Lamellar Pearlite

Abstract The main problem associated with high thickness carbon steel plate's narrow range or “V” groove welding in conventional welding processes is the sagging of the molten pool due to gravity, which in turn leads to defects formation and deteriorates mechanical properties. This problem could be overcome by the rotating arc gas metal arc welding (RA-GMAW) technique. This investigation aims to evaluate mechanical properties and metallurgical characteristics of high thickness IS2062 Gr-B carbon steel joints welded by RA-GMAW technique. The experimental results show that RA-GMAW joint exhibited higher (598 MPa) tensile strength, higher hardness (220 HV) at weld metal region, and lower impact toughness (137 J) than the unwelded base metal. This is due to the presence of fine acicular ferrite and widmanstatten ferrite matrix mixed with fine lamellar pearlite microstructure in the weld metal region.

Effect of Small Amount of Bismuth on Corrosion Resistibility of Austenitic Stainless Steel Weld Metals

2002 ◽  
Author(s):  
Yasuhiro Hara ◽  
Keisuke Shiga ◽  
Nobuo Nakazawa
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Weld Metal ◽  
Corrosion Behavior ◽  
Arc Welding ◽  
Steel Weld ◽  
Weld Metals ◽  
Stainless Steel Weld ◽  
Austenitic Stainless Steel Weld ◽  
Welding Processes

Flux-cored are welding (FCAW) has increased recently because of high welding efficiency. However, a small amount of bismuth in the weld metals was a residue from the flux component that was added for improving slag detachability. The effect of small amount of bismuth in austenitic stainless steel weld metal on corrosion behavior in wet corrosion environment is not adequately clear because there is little reported to date. In the present research, the effect of bismuth which remained in the weld metal on the corrosion behavior of 308-type weld metal in wet corrosive solution was examined by using different bismuth containing weld metal. Measurement of the anodic polarization curve in a sulfuric acid solution, determination of pitting potential and conducting stress corrosion cracking (SCC) tests in a chloride solution, and implementation of boiling nitric add solution tests were conducted. In addition, the corrosion behavior of the FCAW weld metal was compared with that of Bi-free weld metals by shielded metal arc welding (SMAW) and gas tungsten arc welding (GTAW) to clarify how the corrosion behavior varies between the welding processes. In this research, no noticeable adverse effect of bismuth remained in the 308-type austenitic FCAW weld metals was observed in corrosion test.

Microstructural Design for High Strength Steel Welds: The Concept of Duplex Microstructure

2005 ◽  
Author(s):  
Stephen Liu
Keyword(s):  
Weld Metal ◽  
High Strength Steel ◽  
Lath Martensite ◽  
High Strength ◽  
Low Carbon ◽  
Duplex Microstructure ◽  
Weld Metal Microstructure ◽  
Steel Welds ◽  
Metal Microstructure ◽  
Welding Processes

In the past three decades, Colorado School of Mines researchers have investigated flux-related welding processes for pipeline applications and systematically characterized the fundamental behavior of welding fluxes. They also established the relationships between flux ingredients, weld metal microstructure, and weld joint mechanical properties. These studies clarified for high strength steel welds the importance of the bimodal nature of weld metal inclusions, related to weld metal transformations. As strength and toughness levels of the steels continue to increase, new generations of consumables must be developed. Two novel consumables design concepts are being investigated at the CSM. The first one is based on a duplex microstructure consisted of lath martensite and ferrite, and the second is based on low carbon, high alloy martensite.

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