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.
Citations
More filters
TL;DR: The more stable retained austenite was speculated to improve impact toughness in heat-affected zone (HAZ) and the possible Transformation Induced Plasticity (TRIP) effect at −60 °C test temperature may lower the impact toughness to some degree.
Abstract: Reversed austenite transformation behavior plays a significant role in determining the microstructure and mechanical properties of heat affected zones of steels, involving the nucleation and growth of reversed austenite. Confocal Laser Scanning Microscope (CLSM) was used in the present work to in situ observe the reversed austenite transformation by simulating welding thermal cycles for advance 5Mn steels. No thermal inertia was found on cooling process after temperature reached the peak temperature of 1320 °C. Therefore, too large grain was not generated in coarse-grained heat-affected zone (CGHAZ). The pre-existing film retained austenite in base metal and acted as additional favorable nucleation sites for reversed austenite during the thermal cycle. A much great nucleation number led to the finer grain in the fine-grained heat-affected zone (FGHAZ). The continuous cooling transformation for CGHAZ and FGHAZ revealed that the martensite was the main transformed product. Martensite transformation temperature (Tm) was higher in FGHAZ than in CGHAZ. Martensite transformation rate was higher in FGHAZ than in CGHAZ, which is due to the different grain size and assumed atom (Mn and C) segregation. Consequently, the softer martensite was measured in CGHAZ than in FGHAZ. Although 10~11% austenite retained in FGHAZ, the possible Transformation Induced Plasticity (TRIP) effect at −60 °C test temperature may lower the impact toughness to some degree. Therefore, the mean absorbed energy of 31, 39 and 42 J in CGHAZ and 56, 45 and 36 J in FGHAZ were exhibited at the same welding heat input. The more stable retained austenite was speculated to improve impact toughness in heat-affected zone (HAZ). For these 5Mn steels, reversed austenite plays a significant role in affecting impact toughness of heat-affected zones more than grain size.
6 citations
TL;DR: In this article, the results of metallographic examinations of melted areas and clad welds on the Inconel 713C nickel-based superalloy, made by TIG, plasma arc, and laser, were presented.
Abstract: Inconel 713C precision castings are used as aircraft engine components exposed to high temperatures and the aggressive exhaust gas environment. Industrial experience has shown that precision-cast components of such complexity contain casting defects like microshrinkage, porosity, and cracks. This necessitates the development of repair technologies for castings of this type. This paper presents the results of metallographic examinations of melted areas and clad welds on the Inconel 713C nickel-based superalloy, made by TIG, plasma arc, and laser. The cladding process was carried out on model test plates in order to determine the technological and materialrelated problems connected with the weldability of Inconel 713C. The studies included analyses of the macroand microstructure of the clad welds, the base materials, and the heat-affected zones. The results of the structural analyses of the clad welds indicate that Inconel 713C should be classified as a low-weldability material. In the clad welds made by laser, cracks were identified mainly in the heat-affected zone and at the melted zone interface, crystals were formed on partially-melted grains. Cracks of this type were not identified in the clad welds made using the plasma-arc method. It has been concluded that due to the possibility of manual cladding and the absence of welding imperfections, the technology having the greatest potential for application is plasma-arc cladding.
6 citations
TL;DR: In this paper, the effect of alloy elements such as niobium, titanium, and zirconium on the weld solidification cracking susceptibility in fully austenitic stainless steel was investigated.
Abstract: The effect of alloy elements such as niobium, titanium, and zirconium on the weld solidification cracking susceptibility in fully austenitic stainless steel was investigated. Niobium, titanium, or zirconium was added as an alloy element to Fe-24 mass%Cr-26 mass%Ni stainless steel. The cracking susceptibility was evaluated by crack length, number of cracks, and brittle temperature range (BTR) corresponding to results of the Trans-Varestraint test. Depending on the addition of the alloy element, the crack length increased; the length ordering tendencies between the total crack length (TCL) and the maximum crack length (MCL) differed with the alloy addition. The BTR was obtained by corresponding the MCL to the temperature range using the measured temperature history of the weld metal and was increased by the addition of the alloy element. The maximum BTR for the specimen with titanium was 266.9°C, which was three times that of the specimen without the alloy element. The MC carbide and the Laves phase formed at the dendrite cell boundaries as secondary phases. Solidification calculation based on the Scheil model was used to investigate the effect of the type of the alloy element on the solidification temperature range. Depending on the type of the alloy element, the solidification temperature range varied. A significant difference was found between the solidification temperature range and BTR in the case of the specimen with niobium.
6 citations
TL;DR: In this article, the internal cracking observed in a 6-thick carbon-manganese steel plate after welding is discussed with respect to the presence of material impurities, and the morphology and location of the cracks detected during fabrication of a heavy structure are typical of hydrogen-induced cracking usually associated to hard untempered martensite.
Abstract: The internal cracking observed in a 6″-thick carbon-manganese steel plate after welding is discussed with respect to the presence of material impurities. The morphology and location of the cracks detected during fabrication of a heavy structure are typical of hydrogen-induced cracking (HIC) usually associated to hard untempered martensite. However, typically martensitic microstructures would not be expected for low carbon low alloy steels joints when a suitable welding procedure specification is adopted, which includes preheating and high heat input. This paper illustrates the morphology of the original cracks, which are unrelated to hard microstructures, and presents the results of the welding experiments conducted in samples cut from segregated regions of the 6″-thick plate. Through hydrogenation of thin slices containing impure regions and autogenous gas tungsten arc welding bead, it was possible to reproduce the same cracking characteristics formed during submerged arc welding, indicating that HIC may also be associated to softer phases. Hydrogen entrapment at the weld fusion line can be related to high impurities level due to the expected lower melting points at grain boundaries, explaining the HIC phenomenon. The present paper proposes a model for hydrogen cracking of bainitic structures at the welding heat affected zone that typically is not susceptible to crack.
6 citations
Cites background from "Welding Metallurgy of"
...Little attention has been paid, however, to the contribution of impurities, such as sulfur, in hydrogen-assisted cracking [3]....
[...]
TL;DR: In this article , a novel maraging steel with vanadium supplement called Specialis® has been developed for additive manufacturing by powder bed fusion using a laser beam, and an intensive process optimization was carried out by means of a single track melt pool analysis to investigate optimal parameter sets for manufacturing of dense parts.
Abstract: A novel maraging steel with vanadium supplement called Specialis® has been developed for additive manufacturing by powder bed fusion using a laser beam. This study characterized this material after processing and post-processing. An intensive process optimization was carried out by means of a single track melt pool analysis to investigate optimal parameter sets for manufacturing of dense parts. Furthermore, the development of post heat treatment strategies and their influence on mechanical and microstructural characteristics of the material was evaluated. Two main concepts of direct aging treatment (AT) and solution treatment followed by aging treatment (ST+AT) were tested by dilatometry, to analyse the material behaviour with different initial microstructures: as-built and recrystallized. Both heat treatments resulted in a considerable improvement of hardness after only 2 h of aging, increasing to approximately 700 HV and 760 HV respectively, which exceeded the peak hardness of commonly known maraging steel 18Ni300 (660 HV after 6 h). These results were confirmed by tensile tests, where a tensile strength of more than 2300 MPa was achieved. Alongside the precipitation hardening known for maraging steels, the increased hardness was a result of grain refinement due to the addition of vanadium.
6 citations
References
More filters
TL;DR: In this article, the state of the art in selective laser sintering/melting (SLS/SLM) processing of aluminium powders is reviewed from different perspectives, including powder metallurgy (P/M), pulsed electric current (PECS), and laser welding of aluminium alloys.
1,172 citations
TL;DR: In this article, the authors show that the pre-existing dislocation network, which maintains its configuration during the entire plastic deformation, is an ideal modulator that is able to slow down but not entirely block the dislocation motion.
557 citations
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.
Abstract: Spot welding, particularly resistance spot welding (RSW), is a critical joining process in automotive industry. The development of advanced high strength steels for applications in automotive industry is accompanied with a challenge to better understand the physical and mechanical metallurgy of these materials during RSW. The present paper critically reviews the fundamental understanding of structure–properties relationship in automotive steels resistance spot welds. The focus is on the metallurgical characteristics, hardness–microstructure correlation, interfacial to pullout failure mode transition and mechanical performance of steel resistance spot welds under quasi-static, fatigue and impact loading conditions. A brief review of friction stir spot welding, as an alternative to RSW, is also included.
369 citations
TL;DR: In this article, a unified equation to compute the energy density is proposed to compare works performed with distinct equipment and experimental conditions, covering the major process parameters: power, travel speed, heat source dimension, hatch distance, deposited layer thickness and material grain size.
369 citations
TL;DR: This study attempted to predict solidification defects by DNN regression with a small dataset that contains 487 data points and found that a pre-trained and fine-tuned DNN shows better generalization performance over shallow neural network, support vector machine, and DNN trained by conventional methods.
314 citations