Toughness and Internal Friction of Weld Metal Welded by High-Current MAG Welding

2011 ◽  
Vol 328-330 ◽  
pp. 1077-1081
Author(s):  
An Xia Pan
Keyword(s):  
Internal Friction ◽  
Weld Metal ◽  
Acicular Ferrite ◽  
Impact Test ◽  
Optical Microscope ◽  
The Other ◽  
Mag Welding ◽  
Welding Parameters ◽  
High Current ◽  
Temperature Impact

Low-temperature impact test on four different kinds of weld metal welded by different technologies of high-current MAG welding was carried out in this paper. The results show that different materials and different welding parameters have different effect on impact energy. As the chemical analysis and observation from the optical microscope show that When welding material contains appropriate C, Si, Ti, fine acicular ferrite forms in it; on the contrary, crisp and thick bainite appears. Compares to acicular ferrite which has an Akv>27J at -27°C and better toughness, bainite has a poor toughness and an Akv<27J. The internal friction experiments show that there are two internal friction peaks - Snoek and SKK. The peak is clear when the microstructure is bainite, on the other side, the microstructure is acicular ferrite.

scholarly journals Influence of the Heat Input on the Dendritic Solidification Structure and the Mechanical Properties of 2.25Cr-1Mo-0.25V Submerged-Arc Weld Metal

2021 ◽  
Author(s):  
Hannah Schönmaier ◽  
Ronny Krein ◽  
Martin Schmitz-Niederau ◽  
Ronald Schnitzer
Keyword(s):  
Mechanical Properties ◽  
Weld Metal ◽  
Heat Input ◽  
Stress Rupture ◽  
Pressure Vessels ◽  
Rupture Time ◽  
Solidification Structure ◽  
Welding Parameters ◽  
Austenite Grain Size ◽  
Submerged Arc

AbstractThe alloy 2.25Cr-1Mo-0.25V is commonly used for heavy wall pressure vessels in the petrochemical industry, such as hydrogen reactors. As these reactors are operated at elevated temperatures and high pressures, the 2.25Cr-1Mo-0.25V welding consumables require a beneficial combination of strength and toughness as well as enhanced creep properties. The mechanical properties are known to be influenced by several welding parameters. This study deals with the influence of the heat input during submerged-arc welding (SAW) on the solidification structure and mechanical properties of 2.25Cr-1Mo-0.25V multilayer metal. The heat input was found to increase the primary and secondary dendrite spacing as well as the bainitic and prior austenite grain size of the weld metal. Furthermore, it was determined that a higher heat input during SAW causes an increase in the stress rupture time and a decrease in Charpy impact energy. This is assumed to be linked to a lower number of weld layers, and therefore, a decreased amount of fine grained reheated zone if the multilayer weld metal is fabricated with higher heat input. In contrast to the stress rupture time and the toughness, the weld metal’s strength, ductility and macro-hardness remain nearly unaffected by changes of the heat input.

The Influence of Oxide Inclusion on the Refinement of Bainite and Toughness in HAZ for Low Carbon Steels

2013 ◽  
Vol 651 ◽  
pp. 163-167
Author(s):  
Shu Rui Li ◽  
Xue Min Wang ◽  
Xin Lai He
Keyword(s):  
Mechanical Properties ◽  
Acicular Ferrite ◽  
Oxide Inclusion ◽  
Optical Microscope ◽  
Carbon Steels ◽  
Low Carbon ◽  
Low Carbon Steels ◽  
The Core ◽  
Ti Oxides ◽  
Bainitic Steels

The influence of Ti oxide on the toughness of heat affected zone for low carbon bainitic steels has been investigated. The optical microscope, SEM and TEM were used to analyze the composition, size and distribution of the inclusions, and the microstructure and mechanical properties after welding thermal simulation were also investigated. The effect of Ti oxide inclusion on the transformation of acicular ferrite has also been studied. The results show that after the melting with Ti dioxide technique the inclusion is complex, in the core is Ti oxides about 1-3 micron and around it is MnS. It has been found the acicular ferrite can nucleate at the inclusions and the Ti oxide inclusion will promote the nucleation of acicular ferrite, and the acicular ferrite will block the growth of bainite. Therefore by introducing the Ti oxide in the steels the microstructure of HAZ could be refined markedly therefore the toughness of HAZ can be improved evidently.

The Structure of Sycamore Callus Cells During Division in a Partially Synchronized Suspension Culture

1970 ◽  
Vol 6 (2) ◽  
pp. 299-321
Author(s):  
K. ROBERTS ◽  
D. H. NORTHCOTE
Keyword(s):  
Cell Wall ◽  
Electron Microscope ◽  
Cell Plate ◽  
Optical Microscope ◽  
The Other ◽  
Active Movement ◽  
Developmental Sequence ◽  
Golgi Bodies ◽  
Dividing Cells ◽  
Peripheral Cytoplasm

Sycamore suspension callus cells have been partially synchronized to give a culture with a mitotic index of 15%. Living dividing cells of the culture have been examined with Nomarski differential interference optics and a comparable study made on fixed cells with the electron microscope. An organized band of reticulate cytoplasm partially encircles the nucleus at mitosis. The cell divides by the formation of a phragmosome which grows across the large vacuole; this allows the organization of the cytoplasm which forms the cell plate to be examined separately from the more general cytoplasm of the cell. The cell plate grows from one side of the cell to the other and down its length a complete developmental sequence can be seen. The Golgi bodies and the endoplasmic reticulum are probably involved in the formation of material for the construction of the cell plate and young cell wall. Microfibrils are formed within the plate in the more mature regions, while material contained within vesicles is incorporated at the young growing edge. At the edge of the plate microtubules are found and these correspond to the fibrillar appearance of the phragmoplast seen with the optical microscope. In the living cell an active movement of organelles along the peripheral cytoplasm can be seen and with fixed cells viewed with the electron microscope microtubules are often found adjacent to the plasmalemma and lying close to mitochondria, crystal-containing bodies and plastids. The appearance of crystal-containing bodies and plastids containing phytoferritin is described.

Ground vibrations near dynamite blasts*

1939 ◽  
Vol 29 (3) ◽  
pp. 487-496
Author(s):  
L. Don Leet
Keyword(s):  
Internal Friction ◽  
Initial Energy ◽  
The Other ◽  
Ground Vibrations ◽  
Two Factors ◽  
Natural Decay

Summary In general, then, the concentrated energy at the source is actually divided among the principal wave types, which are there added together. Within very short distances, however, these wave types begin to separate because of their different velocities. There are thus two factors working to reduce the maximum shaking to which the ground is subjected. One is the natural decay of each wave with distance, as internal friction exhausts its original energy. The other, which is usually the dominating effect at short distances, is this stringing out of the wave types, each carrying its portion of the initial energy, until there is no longer any concentration where two or more types join forces to produce additive amplitudes.

scholarly journals Vertical and Horizontal Misfit Analysis of 3-unit FDP Fabricated with Different Techniques and CAD/CAM Systems

2018 ◽  
Vol 29 (4) ◽  
pp. 342-346
Author(s):  
Eduardo Piza Pellizzer1 ◽  
Caroline Cantieri de Mello ◽  
Jéssica Marcela de Luna Gomes ◽  
Joel Ferreira Santiago Júnior ◽  
Cleidiel Aparecido Araújo Lemos ◽  
...  
Keyword(s):  
Reference Model ◽  
Optical Microscope ◽  
The Other ◽  
Marginal Adaptation ◽  
Nicr Alloy ◽  
Partial Denture ◽  
Optical Scanning ◽  
Fixed Partial Denture ◽  
Cad Cam ◽  
Cam Systems

Abstract The aim of this is was evaluate the vertical and horizontal marginal adaptation of 3-unit fixed partial denture frameworks fabricated using different techniques and CAD/CAM systems. A total of 40 framework specimens were fabricated and divided into four groups as follows: lost-wax casting (G1); lost-wax casting with welding (G2); extraoral optical scanning of models (3S/DWOS) (G3); intraoral optical scanning (Cerec Bluecam/Sirona) (G4). A reference model was used to simulate a fixed partial denture with three elements (with a central pontic). The frameworks of G1 and G2 were cast in nickel-chromium (NiCr) alloy, whereas those of G3 and G4 were milled in zirconia. In all groups, vertical and horizontal marginal adaptation (over-contour and under-contour) was evaluated using a three-dimensional optical microscope (Quick Scope, Mitutoyo). The results showed higher vertical marginal misfit in G1 than in the other groups (p<0.001). Regarding horizontal marginal misfit, higher over-contour values occurred in G3 than in the other groups (p<0.001). G3 did not show under-contour at all, whereas the other groups did not differ from each other in this regard (p>0.05). Within the limitations of this study, it can be concluded that lost-wax casting with welding is a viable alternative to the use of CAD/CAM systems to fabricate frameworks of three-unit FPDs, since the techniques yielded similar vertical misfit values. Extra-oral CAD/CAM systems showed the highest horizontal misfit (over-contour) compared to other groups.

scholarly journals Influence of the resistive-pulse welding parameters of nickel super-alloys on selected properties of the connection

Mechanik ◽  
2017 ◽  
Vol 90 (11) ◽  
pp. 1060-1062
Author(s):  
Sławomir Spadło ◽  
Wojciech Depczyński ◽  
Piotr Młynarczyk ◽  
Tadeusz Gajewski ◽  
Jarosław Dąbrowa
Keyword(s):  
Optical Microscope ◽  
Mechanical Tests ◽  
Welding Parameters ◽  
Thin Sheets ◽  
Micro Hardness ◽  
Hastelloy X ◽  
Haynes 230 ◽  
Hardness Tester ◽  
Resistive Pulse ◽  
Pulse Welding

Microstructure and mechanical tests of welds of thin sheets made from nickel-based super-alloys (Haynes 230 and Hastelloy X) were presented. The welds were made using the resistive-pulse micro-welding method using the WS 7000S device. The micro-hardness of the joints was measured with a Matsuzawa Vickers MX 100 hardness tester at 100 G (0.98 N). Metallographic observations of the prepared micro-sections were performed using the Nikon Eclipse MA200 optical microscope at various magnifications. The metallographic microstructure studies were supplemented by linear analysis of the chemical composition, for which the OXFORD X-MAX electron microscope was applied.

scholarly journals Comparative HAZ softening analysis of three different automotive aluminium alloys by physical simulation

2021 ◽  
Vol 66 (1) ◽  
pp. 23-38
Author(s):  
Singh Pratap ◽  
Judit Kovácsb
Keyword(s):  
Aluminium Alloy ◽  
Heat Affected Zone ◽  
Heat Input ◽  
Aluminium Alloys ◽  
Physical Simulation ◽  
Hardness Test ◽  
Optical Microscope ◽  
Automotive Application ◽  
Welding Parameters ◽  
Gleeble 3500

The development of high strength aluminium alloy has revolutionized the automotive industry with innovative manufacturing and technological process to provide high-performance components, weight reduction and also diversified the application field and design consideration for the automotive parts that work under severe conditions, but the selection of proper production parameters is most challenging task to get excellent results. Growing industrial demand of aluminium alloys led to the development of new welding technologies, processes and studies of various parameters effects for its intended purposes. The microstructural changes lead to loss of hardening and thereby mechanical strength in the HAZ welded joint even though the base materials are heat treatable and precipitation hardened. So, our goal is to analyse HAZ softening and analyse the sub-zones as a function of the parameter. In this paper, the influence of weld heat cycle on the heat-affected zone (HAZ) is physically simulated for Tungsten Inert Gas Welding (TIG) using Gleeble 3500 thermomechanical simulator for three different automotive aluminium alloy (AA5754-H22, AA6082-T6 & AA7075-T6) plate of 1 mm thickness. In order to simulate the sub-zones of the heat-affected zone, samples were heated to four different HAZ peak temperatures (550 °C, 440 °C, 380 °C and 280 °C), two linear heat input (100 J/mm and 200 J/mm) by the application of Rykalin 2D model. A series of experiments were performed to understand the behaviour, which make it possible to measure the objective data on the basis of the obtained image of the aluminium alloys tested with heat-affected zone tests in a Gleeble 3500 physical simulator. The main objective is to achieve the weldability of three different automotive aluminium alloys and their comparison based on the welding parameters like heat input. Further, the investigation of HAZ softening and microstructure of the specimens were tested and analysed using Vicker's hardness test and optical microscope respectively. The paper focuses on HAZ softening analysis of different grades of aluminium alloys for automotive application.

scholarly journals The Use of Compressed Air for Micro-Jet Cooling After MIG Welding

2016 ◽  
Vol 61 (3) ◽  
pp. 1405-1408
Author(s):  
D. Hadryś ◽  
T. Węgrzyn ◽  
J. Piwnik ◽  
Z. Stanik ◽  
W. Tarasiuk
Keyword(s):  
Weld Metal ◽  
Acicular Ferrite ◽  
Compressed Air ◽  
Steel Weld ◽  
Low Alloy Steel ◽  
Mig Welding ◽  
Jet Cooling ◽  
Metal Deposit ◽  
Steel Weld Metal ◽  
First Time

AbstractThe material selected for this investigation was low alloy steel weld metal deposit (WMD) after MIG welding with micro-jet cooling. The present investigation was aimed as the following tasks: obtained WMD with various amount of acicular ferrite and further analyze impact toughness of WMD in terms of acicular ferrite amount in it. Weld metal deposit (WMD) was first time carried out for MIG welding with micro-jet cooling of compressed air and gas mixture of argon and air. Until that moment only argon, helium and nitrogen were tested as micro-jet gases for MIG/MAG processes. An important role in the interpretation of the results can give methods of artificial intelligence.

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