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Influence of welding parameters on microstructure of welded joints SMAW/GTAW steel X10 CrMoVNb 9-1 (P91) [Influenza dei parametri di saldatura sulla microstruttura di giunti saldati SMAW/GTAW di acciaio X 10 CrMoVNb 9-1 (P91)]
No full textThis paper presents weldability results of P91 creep resistant steels performed through two different welding technologies: The " fully mechanized (GTAW)", and the "Shielding Metal Arc Welding (SMAW)" It was evaluated the influence of welding parameters on the microstructure of the joint and on the consequent mechanical characteristics (Strength, toughness and ductility) of the fused zone (ZF). With reference to the P91 creep resistant steel (Tab.1), the RCC-MRx code for the design and production of components for nuclear power plants, have data sheet about the chemical and mechanical features of "Base Material" (BM) but does not have data sheet about filler materials, as qualified for welding nuclear components class 1. Scope of this work is to evaluate possible candidate filler material (Tab.2) and to suggest welding technologies and related operative welding conditions to ensure that N1 class could be produced with the same requirements as the Base Material, in compliance to the design code. The main objective of this study is to evaluate the candidate filler materials and suggest welding conditions optimized for PWTH, Heat Input (HI), and Deposition Mode/Ratio(DM/DR), to obtain an elongation of more than 20 % and a toughness of more than 60 J to 0°C (as evaluated by Charpy KV test)in the fused zone (ZF). For both processes, according to the literature data, it was decided to analyze the influence of four parameters: Speed of deposition (deposition ratio DR ); mode of deposition (DM); Heat input (HI); duration of PWHT . To varying DR/ DM were chosen two different bevel angles (60 ° and 75 °), two modes of deposition (" String Beads"," Weave Beads "), obtained through different welding speed Ws. Two different holding times (2h , 4h ) for PWHT were investigate to evaluate the influence of Time on the feature of FZ. The test was carried out in compliance within the RCC- Mr and the correlate ISO Standard: ( UNI EN ISO 15614-1 ; Transversal tensile test: ISO 4136-2011 & ISO 6892-1 ; Longitudinal tensile test: IS05178 - 2011 and ISO 6892-2 , ISO 9015). The Data about the performed test are reported in Tab. 6. In general for both the welding technology evaluate, the Fused Zone as welded have a fully martensitic microstructu- res, this is demonstrated by the high value of hardness. After the PWHT the hardness in FZ decreases from more of 400 to 230-250 HV5, typical values of tempering martensite. The comparison between the hardness profiles measured at different conditions and PWHT show that the duration of the holding time influences the hardness (Fig.1). If the hoi-ding time increases the hardness in FZ decreases. About SMAW, the toughness improves with increasing the holding time of the PWHT. However only for the condition of welding "weave beads" the value is in compliance with the RCC- MR (Tab. 6). In general, a little reduction of tensile strength was observed after the PWHT, and the differences increase with the increase in holding time. At the same way, the test on GTAW coupons, confirming that longer PWHT holding time induces a reduction in the hardness of fused zone. The micro hardness test highlighted the well know problem of softening in the interface between of HAZ and BM, where the material was subjected to an unavoidable over-tempering (Fig.3). The V notch Charpy tests on GTAW weld shown very high values (higher than SMAW ) in all the case in compliance , with the requirement of RCC-MR. The longitudinal tensile test at room temperature for GTAW ZF specimens (Tab.10), shows very high values of Rm than SMAW. However, this high values are not in compliance with the requirements of the RCC-MR (Max 760 MPa). At the same time the values of elongation, both for GTAW and SMAW processes, is more than 17%, which is promising for a filler material but less than the 20%, threshold required for the BM and the target for the welds. The influence of holding time of PWHT on the mechanical features is the same for the two processes analyzed. The strength is reduced and the elongation increased with augment of holding time of the PWHT. ' The longitudinal tensile test at 550°C were performed only for the GTAW coupons and shown values of Rp 0,2 more than required (260 MPa) and an elongation more than 20 (Tab.11). The SMAW and GTAW shown that the "weave beads" Deposition Mode allowed obtaining the best results in terms of toughness and ductility. The holding time of PWHT influenced the toughness, hardness and strength of the welds. The holding time of 4 h appear to allow the best results. The elongation in all tests for processes at room temperature were less than 20 %. The fully mechanized GTAW showed values of strength very high in association with very good toughness. In all the processes two main problem remain: The softening zone between HAZ and BM (Type IV Cracking zone); The elongation less than 20% , which is requested for the Base Material. Values of elongation of 17-18% are commonly achievable from a wide range of processes and welding parameters. To increase this value, the augment of the PWHT holding time seems to improve the elongation but a long time of PWHT ; means a higher over-tempering of the Type IV Cracking zone. So, in conclusion, the filler material used in this work is a good candidate to weld Nuclear component made of P91,; however the target in terms of ductility and maximum strength, required as BM of RCC-Mr, needs to be reviewed
Development and Renewal in the Strategies of Small Family-Owned Businesses: the Opportunities of Inter-Generational Transfer
No full textSviluppo e rinnovamento nelle strategie delle piccole imprese familiari: le opportunità del passaggio generazionale
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Rise and fall of a vegan food producer. What role for ethical values?
No full textThe idea of veganism was established in 1944 and is about following a plant-based diet that does not include
eggs, dairy, or any other animal-derived substances. The popularity of the "vegan lifestyle" has grown
considerably in recent years. This allowed for large retailers and small makers of vegan goods to work
together. We look at a small business owner who adopted a vegan lifestyle out of an ethical conviction.
Initially running a small venture, he attempted to expand to bigger markets but failed to do so. Our aim is to
analyse the reasons for this failure, with a focus on the role of ethical values. The impact of ethical principles
on business growth and the potential constraints to business expansion are addressed. In so doing, our
research contributes to the scarce literature on sustainable business failure by examining the influence of an
entrepreneur's values on his or her decision-making. Our study revealed that entrepreneurs face not only
ethical but also cognitive challenges. At times, their moral beliefs may hinder their understanding of the
needs of a market outside their own community
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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