Welding Metallurgy of
01 Jan 1987-
About: The article was published on 1987-01-01 and is currently open access. It has received 991 citations till now. The article focuses on the topics: Welding.
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Dissertation•
15 Mar 2016
TL;DR: In this article, the effects of in-process weld tempering with secondary current pulse has on the weld toughness during resistance spot welding (RSW) of USIBOR steels, and the joint performance properties, micro-hardness map profiles, and failure modes of welds for both tempered and non-tempered
Abstract: Escalating environmental concerns have prompted
efforts to reduce vehicle weight and carbon emissions, resulting in
increased application of advanced high strength steels (AHSS).
22MnB5 hot stamping grade AHSS, namely USIBOR 1500P, provide high
strength to weight ratio allowing sheet thickness reduction to
decrease weight, while maintaining high safety characteristics.
Resistance spot welding (RSW) has been the predominant welding
process for automotive assemblies. Welding hot-stamping AHSS has
introduced new challenges for achieving acceptable welds. The added
alloying elements and high hardenability characteristics resulting
in low weldability and weld toughness complicates this initiative.
The current study examines the effects of in-process weld tempering
with secondary current pulse has on the weld toughness during RSW
of USIBOR steels. RSW and weld tempering were tested on USIBOR at
two different surface conditions; as-delivered and hot-stamped.
Joint performance properties, micro-hardness map profiles, and
failure modes of welds for both tempered and non-tempered
conditions are detailed. Furthermore, a relationship between
resulting joint performance and microstructural evolution is
produced.
The objective of this work is to optimize in-process
tempering parameters, analyze metallurgical evolution of the
weldments, and compare the effects on mechanical performance for
both tempered and non-tempered welds.
9 citations
Cites background from "Welding Metallurgy of"
...The initial solidification of the weld pool is that of epitaxial nucleation and growth, initializing at the liquid-solid interface, known as fusion boundary (FB) [44, 45, 46]....
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01 Jul 2011
TL;DR: In this paper, the porosity analysis of AA 6061-T6 with 6 mm thickness plate using two dissimilar filler metals in the gas metal arc welding (GMAW) process was investigated.
Abstract: Effect of porosity distribution in the weld metal of AA 6061-T6 with 6 mm thickness plate using two dissimilar filler metals in the gas metal arc welding (GMAW) process was investigated. This paper provides a characterization of the porosity in term of the distribution, location and size of the pores in the weldment region. The porosity characterization was made by using 3D X-Ray Computed Tomography and Scanning Electron microscope. The existing pores resulting from the cause of the filler metal in welded alloy used ER4043 (Al-5Si) was compared with the weldement used ER5356 (Al-5Mg). From this investigation, it is exhibited that the pores only distributed and located mainly at the edges and at the root of the weldment with ER5356 weld metal, however, for weldment with ER4043, the pores were mainly scattered in the centre region. The distribution and location of pores in weld metal is believed due to the effect of convections in the molten metal, solidification rate and also from the gases induced during the weld process. Apart from that, results of tensile test indicated the weldment has affected the strength and ductility of the two different fillers selected. AA6061 with ER5356 are dropped 50% in ultimate tensile strength (UTS) and 40 % in elongation; meanwhile AA6061 with ER 4043 was dropped 70% in UTS and 90% in elongation. The different principle alloying element of these two filler metals have play significant role in the distribution of porosity in AA6061 weldment and had influence the strength and ductility of the weld joint.
9 citations
TL;DR: In this article, the feasibility of using laser welding to construct a rectangular section to a flat plate was investigated in the context of spaceframe assembly, where the MIG welding solution would be adopted to manufacture such a joint.
Abstract: Automotive manufacturing is making significant strides towards producing lighter but stronger vehicles. Developments in high strength steels and lightweight materials, especially aluminium, have contributed to these advances. The body shell contributes nearly 25% of a car's weight. Current predictions estimate the contribution of aluminium in a car to be of the order of 10% of the total vehicle weight, whereas the use of aluminium alloys in car body manufacture could lead to potential weight savings of up to 43%. The use of aluminium is expected to grow in body in white and tailored welded blank applications within the automotive sector. Complex joint configurations are encountered in spaceframe assembly. One such joint structure, which involves the welding of a rectangular section to a flat plate, has been considered in the work reported. Traditionally, a MIG welding solution would be adopted to manufacture such a joint. Work was performed to establish the feasibility of using laser welding to ma...
9 citations
TL;DR: In this article, a double-sided welded S700MC steel is successfully welded using low power pulsed Nd:YAG laser and the microstructure and mechanical properties are investigated.
Abstract: Thermomechanically controlled processed steels have gained attention increasingly by many industries. In this research S700MC steel is successfully welded using low power pulsed Nd:YAG laser and the microstructure and mechanical properties are investigated. It is shown that the average power and overlapping factor both affect the weld geometry. Full penetration with double-sided welding achieved on 2 mm thick plates autogenously. Optical metallographic methods and SEM/EDS were used to evaluate the resulting microstructures. The evaluations revealed that the weld metal microstructure contains different morphologies of ferrite such as acicular, allotriomorphic and Widmanstatten as well as bainaite and martensite structure in the weld zone. Also, no noticeable heat affected zone was detected near the fusion zone of the weldments. In addition to microstructures investigation, micro hardness and tensile tests were performed to evaluate mechanical properties. Hardness measurement results exhibit higher hardness values in weld zone than that of in the base metal. The tensile test revealed a ductile fracture behavior which happened in the base metal, due to proper weld zone microstructure. The strength and elongation of the prepared joints were 774 ± 14 MPa and 26.5 ± 2.5%, respectively.
9 citations
Dissertation•
01 Jan 2019
TL;DR: Hytönen et al. as discussed by the authors investigated the effect of microstructure on brittle fracture initiation in a Reactor Pressure Vessel Weld Metal and concluded that the weld is a high-quality weld throughout the wall thickness.
Abstract: Noora Hytönen: Effect of Microstructure on Brittle Fracture Initiation in a Reactor Pressure Vessel Weld Metal Master of Science Thesis Tampere University Materials Science November 2019 The weld can be the most life-limiting part in a reactor pressure vessel (RPV). During operation, the pressure vessel components are subjected to high temperature and neutron irradiation induced ageing, which cause embrittlement. The RPV head is only subjected to thermal ageing. Submerged arc welding method is commonly used in the construction of reactor pressure vessels. Welding is a complex process that often introduces inclusions and other second-phase particles in the weld, which play a role in brittle fracture. Non-metallic inclusions, such as oxides, are brittle particles that may initiate a cleavage fracture when the loading stress exceeds the critical stress at the crack front. Knowledge on ductile-to-brittle transition and all factors affecting that are a critical safety matter, and therefore understanding the fracture mechanics of an RPV is important. A ferritic steel weld experiences a ductile-to-brittle transition, causing the metal to act brittle at low temperatures and ductile at elevated temperatures. Severe ageing is known to shift the transition temperature towards higher temperatures due to embrittlement. The brittle fracture must be avoided by securing that the weld metal remains ductile in all situations. Factors affecting the brittle fracture in RPVs have been researched, but more detailed knowledge on weld embrittlement in needed in order to increase the understanding of affecting parameters, and eventually increase the RPV life time and prevent the formation of brittle fracture. This thesis is part of the BRUTE (Barsebäck RPV material used for true evaluation of embrittlement) project at VTT Technical Research Centre of Finland Ltd. The project belongs to the SAFIR2022 programme (The Finnish Research Programme on Nuclear Power Plant Safety 20192022). The aim of the thesis is to increase the understanding of factors affecting brittle fracture initiation in the RPV weld metal. The investigated material is from a decommissioned Swedish nuclear power plant reactor pressure vessel, Barsebäck Unit 2, which had been in effective operation for 23 years. The base material consists of standard bainitic pressure vessel steel and the weld metal is high in Ni and Mn. All the experiments were performed at VTT Centre for Nuclear Safety (CNS), pioneering the new laboratory facilities. The experiments in this thesis concentrated on two main subjects, i.e., weld microstructure characterisation and brittle fracture mechanics. The general microstructural characterisation concluded that the weld is a high-quality weld throughout the wall thickness. The heat-affected zone (HAZ) consisted of fine-grained and coarse-grained regions. The solidification structure consisted of a typical multipass weld with as-welded and reheated regions. Acicular ferrite dominated the as-welded microstructure with some grain boundary ferrite between the columnar grains. Polygonal ferrite dominated the reheated microstructure with some grain boundary ferrite and acicular ferrite. The macroand microhardness measurements of the weld showed homogeneous weld and the macrohardness profiles were plotted from the base material to the HAZ and to the weld metal. The transition temperature and ageing effect were determined by Charpy V-notch impact toughness test. The testing gave a transition temperature of -75 ◦C. In this thesis, the investigated fracture specimens were tested at low temperatures, i.e., in the brittle fracture regime. On all investigated brittle specimens the cleavage fracture initiated at a particle rich in Mn, Al, Si, and O, and the particle was always the largest at the area of a maximum crack driving force. No severe thermal ageing effect has been observed.
9 citations
Cites background from "Welding Metallurgy of"
...387] During cooling in the temperature range from 800 to 500 ◦C, several factors affect the microstructure development such as the cooling time (∆t8−5), steel alloying, oxygen content, and austenite grain size [10]....
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...[10] The process can be fully automatised with typical usage of direct-current electrode positive and the flux can be reused after removal....
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...work hardening or precipitation hardening can be affected significantly during welding, as the high temperature in the heat-affected region reduces the strength by microstructure changes [10]....
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...A continuous filler metal wire electrode is fed through the blanket of the granular flux to generate the arc to form the molten pool that is a mixture of the slag and the weld metal [10]....
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...[6, 10] The solidification of an alloy is not homogeneous nor under equilibrium conditions....
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References
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TL;DR: In this article, the fundamental understanding of structure-properties relationship in automotive steels resistance spot welds is discussed. And a brief review of friction stir spot welding, as an alternative to RSW, is also included.
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