Academic literature on the topic 'Autogenous welding'
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Journal articles on the topic "Autogenous welding"
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Ahn, Young Nam, and Cheol Hee Kim. "Evaluation of Crack Sensitivity and Gap Bridging Ability during Laser Butt Welding of Aluminum 5J32 and 6K21 Alloys." Materials Science Forum 695 (July 2011): 247–50. http://dx.doi.org/10.4028/www.scientific.net/msf.695.247.
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Growing demand to reduce fuel consumption has accelerated the application of Al sheets to the body structure of automobiles. While recent studies on laser welding of Al 5xxx series and Al 6xxx series alloys have examined weldability, the laser autogenous welding usually results in low gap bridging capability and weld defects such as porosity, underfill, cracking, and so on. In this study, we evaluated the gap bridging capability and the crack sensitivity during laser autogenous welding, laser welding with filler wire, and laser-arc hybrid welding, respectively. Al 5J32 and 6K21 sheets were used as the base metal and Al 4xxx series and Al 5xxx series wires were used as the filler metal. Employing adequate welding conditions, the gap bridging capability during butt welding was investigated for each welding process. To clarify the solidification crack sensitivity, bead-on-plate welding was implemented for a tapered specimen as a self-restraint crack test. Compared with the laser autogenous welding, laser welding with filler wire and the laser-arc hybrid welding showed improved gap bridging capability and reduced crack sensitivity.
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Zhang, Shiwei, Junhao Sun, Minhao Zhu, Lin Zhang, Pulin Nie, and Zhuguo Li. "Fiber laser welding of HSLA steel by autogenous laser welding and autogenous laser welding with cold wire methods." Journal of Materials Processing Technology 275 (January 2020): 116353. http://dx.doi.org/10.1016/j.jmatprotec.2019.116353.
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Lisiecki, A. "Welding of Thermomechanically Rolled Steel by Yb:YAG Disk Laser / Spawanie Stali Walcowanej Termomechanicznie Laserem Dyskowym Yb:YAG." Archives of Metallurgy and Materials 60, no. 4 (2015): 2851–60. http://dx.doi.org/10.1515/amm-2015-0456.
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Autogenous laser welding of 5.0 mm thick butt joints of thermomechanically rolled steel S700MC was investigated. The Yb:YAG disk laser TruDisk 3302 emitted at 1.03 μm was used for the trials of autogenous welding. The effect of laser welding parameters and thus thermal conditions of welding on weld shape, microstructure of weld metal and heat affected zone (HAZ), tensile strength, bending angle, impact toughness and microhardness profile was determined. Studies have shown that it is advantageous to provide a high welding speed and low heat input. High cooling rate of weld metal and HAZ leads to the formation of a favorable structure characterized by a large proportion of fine-grained acicular ferrite and provides high mechanical properties of butt joints.
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Allen, C. M., G. Verhaeghe, P. A. Hilton, Chris P. Heason, and Philip B. Prangnell. "Laser and Hybrid Laser-MIG Welding of 6.35 and 12.7mm Thick Aluminium Aerospace Alloy." Materials Science Forum 519-521 (July 2006): 1139–44. http://dx.doi.org/10.4028/www.scientific.net/msf.519-521.1139.
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Fusion welding of 7xxx aluminium alloy plates has been investigated for aerospace applications using autogenous laser welding and hybrid laser-MIG welding. Nd:YAG and Yb-fibre lasers have been used, with two different focussed spot sizes in each case. Autogenous and hybrid welding of 12.7mm thick plate using the Yb-fibre laser with a 0.6mm diameter spot was selected for further development, on the basis of penetration and weld quality achieved. These welds were acceptable to the highest quality class B (stringent) of BS EN ISO 13919-2:2001, with a porosity of only 0.3% of the cross-sectional area of the weld, and close to class A of AWS D17.1. Transverse proof strengths of ~60% of parent material were achieved. Development of hybrid welding is ongoing with novel fillers to refine weld metal grain structure and improve weld properties.
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Adamiec, Janusz, and Robert Kocurek. "Effect of Autogenous Laser Weld on Microstructure and Mechanical Properties of Inconel 617 Nickel Alloy." Solid State Phenomena 226 (January 2015): 43–46. http://dx.doi.org/10.4028/www.scientific.net/ssp.226.43.
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One of the most advanced manufacturing technologies is laser welding. Due to the limited power of the beam, the difficulty of precise preparation of the joint and the possibility of hardening in a narrow heat affected zone laser welding is used only for basic low carbon and low alloy steels. In this work the effects of autogenous weld parameters on microstructure and properties of the Inconel 617 alloy were studied. For this purpose the technological test of laser autogenous weld was performed.
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D'amato, Clayton, Maurizio Fenech, Stephen Abela, John C. Betts, and Joseph Buhagiar. "Autogenous Laser Keyhole Welding of AISI 316LTi." Materials and Manufacturing Processes 25, no. 11 (2010): 1269–77. http://dx.doi.org/10.1080/10426914.2010.490862.
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Caiazzo, Fabrizia, Vittorio Alfieri, and Vincenzo Sergi. "Investigation on Mechanical Properties of Disk Laser Welded Aerospace Alloys." Advanced Materials Research 702 (May 2013): 128–34. http://dx.doi.org/10.4028/www.scientific.net/amr.702.128.
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The original micro structure of the base metal is significantly affected by a welding thermal cycle, irrespective of the type of the heat source. Hence, new phases and different grain size result in the welding bead. The tensile strength of the overall structure is affected in turn. Tensile tests are normally conducted to eventually test a square butt joint configuration. In conjunction, micro hardness is thought to be a good indicator to predict where the fracture would occur in the welded structure. Referring to common metal alloys for aerospace and considering a diode-pumped disk-laser source, the response of the base metal to the laser beam is investigated in this paper. Autogenous welding of aluminum alloy 2024, autogenous welding of titanium alloy Ti-6Al-4V and dissimilar welding of Haynes 188 with Inconel 718 are discussed, with respect to micro structure changes in the fused zone and in the heat affected zone. The failure mode is examined.
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Abdolvand, Hamidreza, Mike Keavey, H. Dai, et al. "On the Stress Development in SA508 Autogenous Weld." Materials Science Forum 783-786 (May 2014): 2123–28. http://dx.doi.org/10.4028/www.scientific.net/msf.783-786.2123.
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Considering the significant role that residual stresses play in determining the lifetime-service of materials, it is mandatory to have a good understanding of and a means of predicting those that develop during welding processes. For this purpose, a User MATerial subroutine (UMAT) is developed to study the effects of various parameters that influence solid state phase transformations and residual stress evolution during welding of SA508 ferritic steel. The temperature dependent elastic and kinematic hardening parameters for each of the individual phases that can potentially develop during cooling from elevated temperatures are measured and are used for calculating stress development during low (75 mm/min) and high (300 mm/min) speed gas-tungsten arc welding (GTAW) on SA508 grade 3. These two speeds are selected to cover a wide range of cooling rates in the heat affected zone so that different phase proportions would be present. The results of the numerical simulations for residual stresses are compared against those measured by neutron diffraction. It is shown here that a low speed weld results in bainite formation whereas a high speed weld results in bainitic as well as subsequent martensitic phase transformations where each welding rate results in different residual stress development.
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Betini, Evandro Giuseppe, Maurilio Pereira Gomes, Cristiano Stefano Mucsi, Temístocles de Souza Luz, Marcos Tadeu D'azeredo Orlando, and Jesualdo Luiz Rossi. "Study of the Thermal Diffusivity Variation in Thin Duplex Steel Plates Welded by GTAW Process." Materials Science Forum 930 (September 2018): 460–65. http://dx.doi.org/10.4028/www.scientific.net/msf.930.460.
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This study describes the thermal diffusivity of thin duplex steel plates in the thickness direction measured using the laser-flash method after welding. The work reports the experimental efforts in recording temperature profiles of the grade UNS S32304 duplex steel during autogenous welding. The butt weld autogenous joints were carried out by the GTAW (gas tungsten arc welding) process with either argon or argon - 2% nitrogen atmospheres. The amount of nitrogen in the heat affected regions, after welding, was measured and correlated with the variation of the thermal diffusivity of the studied material. The temperature profiles were obtained using k-type thermocouples connected to a digital data acquisition system. Different thermal cycles and thermal diffusivity values were observed in the heat-affected zone (HAZ) for both samples. In the solidified zone (SZ) was observed similar increase of the thermal diffusivity values for the plates welded with pure argon and argon plus nitrogen atmosphere.
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Hu, B., and I. M. Richardson. "Autogenous laser keyhole welding of aluminum alloy 2024." Journal of Laser Applications 17, no. 2 (2005): 70–80. http://dx.doi.org/10.2351/1.1896964.
Full textDissertations / Theses on the topic "Autogenous welding"
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Sedy, Eugene B. "Validation of a computational model for autogenous arc welding." Thesis, Monterey, California. Naval Postgraduate School, 1990.
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Approved for public release, distribution is unlimitedA three dimensional transient computational model of heat transfer are welding is generalized, and then validated by comparison to Rosenthal's solution for moving point sources of heat. The current version of the code allows much greater flexibility in the specification of the thermal input from the arc. The resulting surface temperature profiles and fusion zone shapes are compared to those measured experimentally for several input power levels ofr autogenous gas tungsten arc welding. Arc efficiency is experimentally determined using change of phase of a liquid fluorocarbon. The model is shown to be useful for modeling autogenous welding of thick plates. Weld seam misalignment and surface flaw detection are shown to be possible ahead of hte arch with accurate surface temperature detection methods. The potential of the model are creating a database of fusion and heat zone sizes, temperature profiles, and coding rates for various materials, processes, and power levels is indicated.
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Ule, Robert L. "A study of the thermal profits during autogenous arc welding." Thesis, Monterey, California. Naval Postgraduate School, 1989. http://hdl.handle.net/10945/26277.
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Prins, Heinrich Johann. "The effect of autogenous gas tungsten arc welding parameters on the solidification structure of two ferritic stainless steels." Diss., University of Pretoria, 2019. http://hdl.handle.net/2263/79303.
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Ferritic stainless steel is typically used in the automotive industry to fabricate welded tube that is plastically
deformed for flanging, bending and necking. The effect of welding parameters during autogenous gastungsten
arc welding (GTAW) of thin sheet on the weld metal structure and tensile properties were
determined. Two grades of ferritic stainless steels, a titanium-containing Grade 441 and a titanium-free
molybdenum-containing Grade 436, were used as base metal. Statistical analysis was used to determine the
influence of welding parameters on the microstructure of autogenous GTAW welds. The results of Grade 441
indicated that the welding speed and peak welding current had a statistically significant influence on the
amount of equiaxed grains that formed. For Grade 436, the same welding parameters (welding speed and
peak welding current) had a statistically significant influence on the grain size of the weld metal grains. The
ductility of a tensile test coupon machined parallel to the weld direction, for both base metal grades, was
unaffected by the welding parameters or the weld metal microstructure. The elongation was determined by
the amount of weld metal in the gauge area of a tensile coupon. The titanium content of the base material
seems to have the most significant effect on the formation of equiaxed grains.Dissertation (MEng)--University of Pretoria, 2019.
Metallurgical Engineering
MEng
Unrestricted
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GOMES, ANA PAULA SILVA. "EFFECT OF N2 ADDITION ON THE GAS PROTECTION FOR AUTOGENOUS AND NI-CONTAINING WELD METAL WELDING OF DUPLEX STAINLESS STEELS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2018. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=35991@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
PROGRAMA DE SUPORTE À PÓS-GRADUAÇÃO DE INSTS. DE ENSINO
PROGRAMA DE SUPORTE À PÓS-GRADUAÇÃO DE INSTITUIÇÕES COMUNITÁRIAS DE ENSINO PARTICULARES
Os aços inoxidáveis duplex (AID) são uma classe de aços que combinam a alta resistência mecânica da ferrita e a ductilidade da austenita possuindo alto limite de escoamento e resistência à corrosão, sendo empregados em meios corrosivos com solicitações mecânicas elevadas. As boas propriedades mecânicas e de resistência à corrosão se devem a microestrutura duplex (ferrita e austenita), com proporções volumétricas similares, e cujo balanço é controlado por meio da composição química e tratamentos térmicos durante a fabricação. No entanto, durante processos de fabricação e manutenção, como a soldagem por fusão, em função do processo utilizado e dos ciclos térmicos impostos, assim como pela presença de gases de proteção que induzem determinada atmosfera, as propriedades do metal de solda e da zona termicamente afetada (ZTA), podem ser alteradas. Deste modo, a composição química, a distribuição dos elementos de liga e balanço das fases destas regiões serão suscetíveis a transformações de fases como ferritização, precipitação de fases indesejáveis e perda de elementos de liga, como níquel e nitrogênio, resultando em redução da resistência à corrosão. A presença de nitrogênio nos aços duplex, tanto em conjunto ou como substituto para o níquel, influencia na formação da austenita e também no controle da cinética de transformação de fases durante o resfriamento. O presente trabalho teve como objetivo estudar os efeitos do nitrogênio e do níquel na transformação de fases de dois aços inoxidáveis duplex (SAF 2304 e 2507) durante dois processos de soldagem: autógena e com metal de adição contendo Ni. Ambas as soldagens foram realizadas com aporte térmico fixo e com um e dois passes, utilizando a técnica de cordão sobre chapa para a soldagem com metal de adição. Foram utilizados dois gases de proteção, Ar e Ar + N2. Foram avaliadas a dureza e a resistência à corrosão por cloreto. A microestrutura da ZTA e composição química final do metal de solda alteraram significativamente, comparados ao metal de base. A fração volumétrica da fase austenítica na ZTA reduziu em todas as situações avaliadas. A presença de nitrogênio no gás de proteção manteve o teor deste elemento constante ou mais elevado no metal de solda. Cada conjunto de condições de soldagem aplicada apresentou diferentes características de dureza e resistência à corrosão por pites, sendo que na soldagem autógena do SAF 2507 foram encontradas durezas mais altas e menores perdas de massa após ensaio de corrosão. Com a adição de N2 no gás de proteção o teor de nitrogênio final aumentou em relação ao teor de nitrogênio no metal base, porém a fração volumétrica de austenita não se elevou da mesma forma.
Duplex stainless steels (DSS) combines high yield stress from ferrite and ductility from austenite, good mechanical and corrosion resistance. It has been used in corrosive environments associated with severe mechanical stress. The good mechanical strength and corrosive resistance properties are due to the duplex microstructure (ferrite and austenite), with the same volumetric fraction, whose balance is controlled by chemical composition and heat treatment during steel manufacturing. However, when welded by process such as fusion welding the high thermal cycles and the presence of shielding gases inducing a certain atmosphere, the properties of the weld metal (WM) and the heat affected zone (HAZ) can be significantly changed. Therefore, the chemical composition, element partioning and the phase balance in these regions (WM and HAZ) will be susceptible to phase transformations such as ferritization, precipitation of secondary phases and alloy element losses, such as nitrogen and nickel, resulting in the decrease of the corrosion resistance. The presence of nitrogen in the duplex steels, either together or as a substitute for nickel, influences the austenite formation and controls phase transformation kinetics during cooling as well. The objective of this work was to study the effect of nitrogen and nickel on the phase transformation of two duplex stainless steels (SAF 2304 and 2507) during two welding processes: autogenous and with Ni-containing filler metal, considering a fixed thermal input and welds with one and two passes, using the technique of bead on plate for the weld with filler metal. Two shielding gases were used, Ar and Ar + N2. Hardness and corrosion resistance in chloride environment were evaluated for each studied condition. Both HAZ microstructure and final chemical composition of the weld metal modified significantly, when compared to the base metal. The HAZ volume fraction of austenite was reduced, and the presence of nitrogen in the shielding gas helped to keep the nitrogen content the same or increased in the weld metal. Each set of weld parameters applied presented different characteristics of hardness and pitting resistance corrosion. The autogenous welding of the SAF 2507 presented higher hardness and low weight losses. In a general way, the addition of N2 in the shielding gas increased the nitrogen content of the weld metal for all conditions of lean duplex material, compared to the base metal, but the austenite volumetric phase did not increased in the HAZ.
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Barros, Isabel Ferreira de. "Dissimilar welding of ferritic stainless steel AISI 444 and AISI 316L austenitic stainless steel through the autogenous TIG process using pulsed current." Universidade Federal do CearÃ, 2014. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=14072.
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FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgicoThe use of stainless steels has intensified with the industrial demand growing, which extends its application for various sectors such as the oil and gas, desalination equipment in industry, sugar industry, among others. In that context, the use of ferritic stainless steels has grown in recent years on account of its excellent relationship between corrosion resistance and cost, and a great option in substitution of austenitic stainless steels. Intending to study the connection of dissimilar stainless steels by means of a welding process, this paper will lay the submit the ferritic stainless steel AISI 444 and AISI 316L austenitic stainless steel with TIG welding autogenous (without filler metal) with pulsed current. That union seeks to get a fused zone with better mechanical properties together with the correction of possible related to welding those steels problems, such as grain growth in ferritic steels, to which its refinement is possible through the use of pulsed current during the procedure. The choice of these two materials was based on the characteristics of each one separately for they possess closest properties, despite having different classifications, allowing the combined use of both, and thus ferritic act in order to partially replace the austenitic stainless steel in situations where the combination of high corrosion resistance and mechanical strength are not relevant. That action combined, and does not affect the characteristics of the set of negative way is to use lower cost benefit, because the presence of nickel austenitic stainless steels by more expensive finishes them. Thus, it is expected to provide, through this work, further deepening the respect of dissimilar welding between stainless steel AISI 444 ferritic and austenitic stainless steel AISI 316L, evaluating operational parameters such as the pulse of current and heat input on obtained microstructure and mechanical properties.
A utilizaÃÃo dos aÃos inoxidÃveis tem se intensificado juntamente com a crescente demanda industrial, em que sua aplicaÃÃo se estende pelos mais variados setores, como por exemplo, na indÃstria de petrÃleo e gÃs, em equipamentos de dessalinizaÃÃo, na indÃstria sucroalcooleira, entre outros. Neste contexto, o uso de aÃos inoxidÃveis ferrÃticos tem crescido nos Ãltimos anos devido a sua excelente relaÃÃo entre resistÃncia à corrosÃo e custo, sendo uma Ãtima opÃÃo em substituiÃÃo aos aÃos inoxidÃveis austenÃticos. Objetivando estudar a uniÃo de aÃos inoxidÃveis dissimilares por meio de um processo de soldagem, o presente trabalho submeterà o aÃo inoxidÃvel ferrÃtico AISI 444 e o aÃo inoxidÃvel austenÃtico AISI 316L à soldagem TIG autÃgeno (sem metal de adiÃÃo) com corrente pulsada. Essa uniÃo visa obter uma zona fundida com melhores propriedades mecÃnicas juntamente com a correÃÃo dos possÃveis problemas relacionado à soldagem desses aÃos, como por exemplo, o crescimento de grÃo nos aÃos inoxidÃveis ferrÃticos, em que seu refinamento se torna possÃvel atravÃs da utilizaÃÃo de corrente pulsada durante o procedimento. A escolha desses dois materiais baseou-se nas caracterÃsticas inerentes a cada um separadamente e tambÃm por possuÃrem propriedades muito prÃximas, apesar de possuÃrem classificaÃÃes diferentes, permitindo a utilizaÃÃo combinada de ambos e dessa forma o aÃo inoxidÃvel ferrÃtico atuarà de forma a substituir parcialmente o aÃo inoxidÃvel austenÃtico nas situaÃÃes em que a combinaÃÃo de elevada resistÃncia à corrosÃo e resistÃncia mecÃnica nÃo sÃo tÃo relevantes. Essa utilizaÃÃo combinada, alÃm de nÃo afetar as caracterÃsticas do conjunto de maneira negativa tem como benefÃcio reduzir custos, visto que a presenÃa de nÃquel nos aÃos inoxidÃveis austenÃticos acaba por encarecÃ-los. Dessa forma, espera-se fornecer atravÃs deste trabalho um maior aprofundamento a respeito da soldagem dissimilar entre o aÃo inoxidÃvel ferrÃtico AISI 444 e o aÃo inoxidÃvel austenÃtico AISI 316L, avaliando os parÃmetros operacionais, como a pulsaÃÃo da corrente e a energia de soldagem sobre a microestrutura obtida, bem como as propriedades mecÃnicas.
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Sprengard, Benjamin A. "Effect of Nitrogen Concentration in Shielding Gas on Microstructure and Mechanical Properties of ATI 2003® Lean Duplex Stainless Steel Autogenous Plasma Arc Welding." University of Cincinnati / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1313773905.
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Hosseini, Vahid. "Influence of multiple welding cycles on microstructure and corrosion resistance of a super duplex stainless steel." Licentiate thesis, Högskolan Väst, Avdelningen för svetsteknologi (SV), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-10151.
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Super duplex stainless steel (SDSS) has found a wide use in demanding applications such as offshore, chemical and petrochemical industries thanks to its excellent combination of mechanical properties and corrosion resistance. Welding of SDSS, however, is associated with the risk of precipitation of secondary phases and formation of excessive amounts of ferrite in the weld metal and heat affected zone. The present study was therefore aimed at gaining knowledge about the effect of multiple welding thermal cycles on the microstructure and possible sensitization to corrosion of welds in SDSS.Controlled and repeatable thermal cycles were produced by robotic welding. Oneto four autogenous TIG-remelting passes were applied on 2507 type SDSS plates using low or high heat inputs with pure argon as shielding gas. Thermal cycles were recorded using several thermocouples attached to the plates. Thermodynamic calculations and temperature field modelling were performed in order to understand the microstructural development and to predict the pitting corrosion resistance. Etching revealed the formation of different zones with characteristic microstructures: the fused weld zone (WZ) and the heat affected zone composed of the fusion boundary zone (FBZ), next to the fusion boundary, and further out Zone 1 (Z1) and Zone 2 (Z2). The WZ had a high content of ferrite and often nitrides which increased with increasing number of passes and decreasing heati nput. Nitrogen content of the WZ decreased from 0.28 wt.% to 0.17 wt.% after four passes of low heat input and to 0.10 wt.% after four passes of high heatinput. The FBZ was reheated to high peak temperatures (near melting point) and contained equiaxed ferrite grains with austenite and nitrides. Zone 1 was free from precipitates and the ferrite content was similar to that of the unaffected base material. Sigma phase precipitated only in zone 2, which was heated to peak temperatures in the range of approximately 828°C to 1028°C. The content of sigma phase increased with the number of passes and increasing heat input. All locations, except Z1, were susceptible to local corrosion after multiplere heating. Thermodynamic calculations predicted that a post weld heat treatment could restore the corrosion resistance of the FBZ and Z2. However, the pitting resistance of the WZ cannot be improved significantly due to the nitrogen loss. Steady state and linear fitting approaches were therefore employed to predict nitrogen loss in autogenous TIG welding with argon as shielding gas. Two practical formulas were derived giving nitrogen loss as functions of initial nitrogen content and arc energy both predicting a larger loss for higher heat input and higher base material nitrogen content. A practical recommendation based on the present study is that it is beneficial to perform welding with a minimum number of passes even if this results in a higherheat input as multiple reheating strongly promotes formation of deleterious phases.
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Neto, Samuel Amora Alves. "Caracterização metalúrgica de juntas de aço inoxidável superduplex soldadas por processo TIG autógeno." Universidade do Estado do Rio de Janeiro, 2011. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=2758.
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Os aços inoxidáveis do tipo duplex possuem grande importância na indústria, principalmente na do petróleo e gás natural, por apresentarem elevada resistência mecânica e excelente resistência à corrosão. Caracterizam-se por apresentar estrutura bifásica, constituída de proporções praticamente iguais de ferrita e austenita. O presente trabalho caracterizou juntas soldadas por TIG autógeno de aço inoxidável duplex UNS S32760. Foram confeccionados quatro grupos de amostras, provenientes da variação da corrente de soldagem e consequentemente do aporte térmico (corrente de pico: 25A e 40A - aporte térmico: 0,12KJ/mm e 0,19KJ/mm) e da composição do gás de proteção (argônio puro ou argônio contendo 2,5% nitrogênio). Foram utilizadas técnicas de caracterização por metalografia colorida, análise e processamento digital de imagens, ensaios de microdureza Vickers. Para avaliar a resistência à corrosão foram realizados ensaios de potencial em circuito aberto com solução de cloreto férrico (FeCl3) e eletrodo de referência de calomelano saturado. A análise quantitativa das fases ferrita e austenita presentes nas juntas soldadas mostrou que a adição de nitrogênio no gás de proteção favoreceu a formação da fase austenita, variando de 11% (sem nitrogênio) para 26% (com nitrogênio) a quantidade desta fase. Em uma análise qualitativa a variação do aporte térmico: 0,12KJ/mm para 0,19KJ/mm resultou no aumento do tamanho de grãos da fase ferrita.The duplex stainless steels are of great importance in industry, mainly in oil and natural gas due to their high mechanical strength and excellent corrosion resistance. They are characterized by having biphasic structure, consisting of nearly equal proportions of ferrite and austenite. The present work characterized welded joints by autogenous TIG process of duplex stainless UNS S32760. Four groups of samples were prepared, from the variation of welding current and consequently of heat input (20A and 40A - heat input: 0.12KJ/mm and 0.19KJ/mm) and the composition of shielding gas (pure argon or argon containing 2.5% nitrogen). Techniques of characterization by colored metallography, analysis and digital image processing and Vickers microhardness tests techniques were used. To evaluate the corrosion resistance, tests were performed at open circuit potential with a solution of ferric chloride (FeCl3) and reference electrode of saturated calomel. The quantitative analysis of ferrite and austenite phases present in the welded joints showed that the addition of nitrogen in shielding gas favored the formation of austenite phase, ranging from 11% (without nitrogen) to 26% (with nitrogen) the amount of this phase In a qualitative analysis the variation of heat input (0.12KJ/mm and 0.19KJ/mm) resulted in an increase of the ferrite phases grain size.
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Du, Toit Madeleine. "The behaviour of nitrogen during the autogenous ARC welding of stainless steel." Diss., 2001. http://hdl.handle.net/2263/27913.
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Nitrogen-alloyed austenitic stainless steels are becoming increasingly popular, mainly due to their excellent combination of strength and toughness. Nitrogen desorption to the atmosphere during the autogenous welding of these steels is often a major problem, resulting in porosity and nitrogen losses from the weld. In order to counteract this problem, the addition of nitrogen to the shielding gas has been proposed. This study deals with the absorption and desorption of nitrogen during the autogenous arc welding of a number of experimental stainless steels. These steels are similar in composition to type 310 stainless steel, but with varying levels of nitrogen and sulphur. The project investigated the influence of the base metal nitrogen content, the nitrogen partial pressure in the shielding gas and the weld surface active element concentration on the nitrogen content of autogenous welds. The results confirm that Sievert's law is not obeyed during welding. The weld nitrogen content increases with an increase in the shielding gas nitrogen content at low nitrogen partial pressures, but at higher partial pressures a dynamic equilibrium is created where the amount of nitrogen absorbed by the weld metal is balanced by the amount of nitrogen evolved from the weld pool. In alloys with low sulphur contents, this steady-state nitrogen content is not influenced to any significant extent by the base metal nitrogen content, but in high sulphur alloys, an increase in the initial nitrogen concentration results in higher weld nitrogen contents over the entire range of nitrogen partial pressures evaluated. A kinetic model can be used to describe nitrogen absorption and desorption during welding. The nitrogen desorption rate constant decreases with an increase in the sulphur concentration. This is consistent with a site blockage model, where surface active elements occupy a fraction of the available surface sites. The absorption rate constant is, however, not a strong function of the surface active element concentration. Alloys with higher base metal nitrogen contents require increased levels of supersaturation prior to the onset of nitrogen evolution as bubbles. These increased levels of supersaturation for the higher-nitrogen alloys is probably related to the higher rate of nitrogen removal as N2 the onset of bubble formation. Given that nitrogen bubble formation and detachment require nucleation and growth, it is assumed that a higher nitrogen removal rate would require a higher degree of supersaturation. Nitrogen losses from nitrogen-alloyed stainless steels can be expected during welding in pure argon shielding gas. Small amounts of nitrogen can be added to the shielding gas to counteract this effect, but this should be done with care to avoid bubble formation. Supersaturation before bubble formation does, however, extend the range of shielding gas compositions which can be used. Due to the lower desorption rates associated with higher surface active element concentrations, these elements have a beneficial influence during the welding of high nitrogen stainless steels. Although higher sulphur contents may not be viable in practice, small amounts of oxygen added to the shielding gas during welding will have a similar effect.Dissertation (PHD)--University of Pretoria, 2004.
Materials Science and Metallurgical Engineering
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Books on the topic "Autogenous welding"
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Ule, Robert L. A study of the thermal profits during autogenous arc welding. Naval Postgraduate School, 1989.
Book chapters on the topic "Autogenous welding"
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Tandel, Keyurkumar D., and Jyoti V. Menghani. "Autogenous TIG Welding of Al-5083-H111 Butt Joint." In Lecture Notes in Mechanical Engineering. Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-9117-4_16.
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Kane, S. F., and A. L. Farland. "Techniques for Automatic Autogenous Welding of Low Sulfur 316LN Beam Tube." In Advances in Cryogenic Engineering Materials. Springer US, 1998. http://dx.doi.org/10.1007/978-1-4757-9056-6_14.
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Jayanthi, A., K. Venkataramanan, and K. Suresh Kumar. "Physical Characteristics of Keyhole in 316L Stainless Steel Joint During an Autogenous Pulsed Laser Beam Welding." In Springer Proceedings in Materials. Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-6267-9_59.
Full textConference papers on the topic "Autogenous welding"
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Gopinathan, Santosh, Jayant Murthy, T. Dwayne McCay, Mary Helen McCay, and Lyle Spiegel. "The autogenous laser welding of Al2219 to Al6061." In ICALEO® ‘93: Proceedings of the Laser Materials Processing Conference. Laser Institute of America, 1993. http://dx.doi.org/10.2351/1.5058645.
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Sekhar, N. C., J. D. Russell, and N. A. McPherson. "Autogenous Nd:YAG laser welding of 6mm thick dissimilar steels." In ICALEO® 2001: Proceedings of the Laser Materials Processing Conference and Laser Microfabrication Conference. Laser Institute of America, 2001. http://dx.doi.org/10.2351/1.5059887.
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Meinert, K. C., E. W. Reutzel, R. P. Martukanitz, and J. F. Tressler. "Design of weld joints for non-autogenous laser welding of thick sections." In ICALEO® 2000: Proceedings of the Laser Materials Processing Conference. Laser Institute of America, 2000. http://dx.doi.org/10.2351/1.5059426.
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Rocha, Tarcila, Douglas Silva Marques Serrati, Douglas Araujo, and Louriel Vilarinho. "Residual Stresses During and After Welding Autogenous Processes and With Material Deposition." In 25th International Congress of Mechanical Engineering. ABCM, 2019. http://dx.doi.org/10.26678/abcm.cobem2019.cob2019-1353.
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Francis, J. A., M. Turski, and P. J. Withers. "Residual Stress Measurements in Autogenous SA508 Steel Welds." In ASME 2008 Pressure Vessels and Piping Conference. ASMEDC, 2008. http://dx.doi.org/10.1115/pvp2008-61469.
Full textAbstract:
Engineering integrity assessments for power plant components need to account for the primary loads that arise during service as well as any residual stresses that may be associated with materials processing or fabrication. Welding operations come under particular scrutiny because they introduce substantial residual stresses. These stresses, however, are often either difficult or impractical to measure, so a heavy reliance is placed on obtaining estimates from numerical models. In ferritic steels, the prediction of weld residual stresses is particularly challenging, owing to the solid-state phase transformations that occur upon heating and cooling. Thus there is a great need to validate modeling strategies by comparing predicted stresses with those that are measured on well-defined test cases. In this article, we present the results of neutron diffraction measurements for two configurations that may serve as suitable test cases for weld models; an autogenous edge-welded beam and an autogenous bead on a plate.
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Salminen, Antti, Elin Westin, Esa Lappalainen, and Anna Unt. "Effect of gas shielding and heat input on autogenous welding of duplex stainless steel." In ICALEO® 2012: 31st International Congress on Laser Materials Processing, Laser Microprocessing and Nanomanufacturing. Laser Institute of America, 2012. http://dx.doi.org/10.2351/1.5062503.
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Hamelin, Cory J., Ondrej Mura´nsky, Vladimir Luzin, Philip Bendeich, and Lyndon Edwards. "Accounting for Phase Transformations During Welding of Ferritic Steels." In ASME 2011 Pressure Vessels and Piping Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/pvp2011-57426.
Full textAbstract:
The numerical application of solid-state phase transformation kinetics relating to conventional welding of ferritic steels is presented. The inclusion of such kinetics in weld models is shown to be necessary for capturing the post-weld residual stress field. To this end, a comparison of two approaches is outlined: a semi-empirical approach that uses thermodynamic transformation kinetics to predict phase morphology; and a fully empirical approach that directly links local material temperature to the present constituent phase(s). The semi-empirical analysis begins with prediction of TTT diagrams using thermodynamic principles for ferritic steels. The data is then converted to CCT diagrams using the Scheil-Avrami additive rule, including austenite grain growth kinetics. This information is used to predict the phases present under varying peak temperatures and cooling rates. In the fully empirical approach, dilatometric experiments of steel samples are performed during heating to simulate expected welding conditions. The constitutive response of the sample is then used as input for the subsequent numerical weld analyses. Input derived from each technique is transferred into weld models developed using the Abaqus finite element package. Model validation is carried out by direct comparison with neutron diffraction residual stress measurements on two beams of SA508 Gr.3 Cl.1 steel subjected to autogenous beam TIG welds under varying torch speeds, heat input and preheat conditions.
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Wildash, Clint, and Steve Webster. "Dual Process Welding of Steel Plate." In ASME 2002 21st International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2002. http://dx.doi.org/10.1115/omae2002-28587.
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Large scale fabrication and welding industries, such as those involved in offshore construction, are continuously striving to improve productivity, while maintaining quality levels required by the applicable design codes and standards. To achieve this, new improved welding technologies are regularly being evaluated. One area of development is to combine different welding processes to produce a welded joint exhibiting properties and productivity benefits that neither process could achieve individually. One promising combination is the use of both arc and laser beam welding for products such as pipeline. The welding procedure development work described, was carried out in two stages. Stage 1 (discrete dual processing) investigated the production of a welded joint using both arc and laser welding at separate times. The welds produced for this work, demonstrate that significant increases in welding speed are achievable in comparison to using either process individually. Stage 2 (simultaneous dual processing) investigated arc and laser welding of the joint at the same time from opposing plate faces, with the laser weld pool trailing the arc weld pool so that the former was positioned in the area of highest preheat temperature. The use of arc preheat significantly reduced the hardness of the laser welds to more acceptable levels. The main disadvantage identified for both stages of work was that fit up of the laser welded part of the joint needed to be good to accommodate the autogenous laser weld. Both Stages were shown to be capable of producing full penetration welds at higher productivity than using either process individually. It has been demonstrated that for 19 mm thick plate, an overall doubling of welding speed could be achieved using dual process as opposed to submerged arc welding, which is currently widely used to weld fabricated products such as pipeline. Future work to be carried will include extensive destructive testing on the welds to assess the benefits of Stage 1 and 2, which will be reported in another paper.
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O’Donnell, Dave, Nicole Karlen, and Carl Kettermann. "Performance Implications of High Energy Density Welding of Corrosion Resistant Alloy Heat Exchanger Tubing." In ASME 2010 Pressure Vessels and Piping Division/K-PVP Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/pvp2010-25165.
Full textAbstract:
The advent of Laser Beam Welding (LBW) has had a significant impact on resultant metallurgical performance of stainless steel welded heat exchanger tubing. While productivity enhancements are well recognized the metallurgical benefits are not. The low total heat input combined with the very high energy density results in ultra-fast quenching of molten metal, super-cooling past normal primary ferrite solidification in common 304/304L and 316/316L grades directly to austenite resulting in weldments with no retained delta ferrite and some inherent corrosion advantages. The same low total heat input and high energy density generates dramatically smaller dendrite spacing making subsequent homogenization by the combined efforts of cold work and solution annealing dramatically more effective. It should be recognized that this paper deals with issues relating to tube production where welds are autogenous or made without filler metal addition and are subsequently cold worked and solution annealed. Resulting benefits of laser welding include a seamless metallographic appearance, and improved field performance. The benefits and limitations of these enhancements are explored relative to other common stainless steel grades, as are alloy characteristics affecting performance.
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Pe´rez-Guerrero, Faustino, and Stephen Liu. "Explaining Porosity Formation in Underwater Wet Welds." In ASME 2007 26th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2007. http://dx.doi.org/10.1115/omae2007-29696.
Full textAbstract:
Macroscopic porosity in underwater wet welds is one of the main defects that deteriorate the mechanical properties of the wet welded joints. It is well established that weld metal porosity is a function of pressure, thus water depth. However, the mechanism of porosity formation is not well understood, therefore the problem is not yet mitigated to acceptable levels, particularly at water depths close to and beyond 100 m. To purposely produce porous welds similar to those obtained in wet welding, bead-on-plate (BOP) welds were deposited in air with gas metal arc welding (GMAW) with no shielding gas, with autogenous gas tungsten arc welding (GTAW) and GTAW with cold wire feed using insufficient shielding gas (8 CFH). During welding with both processes, oxygen from the atmosphere readily reacts with the alloying elements in the molten tip of the wire and in the weld pool. Under these conditions, droplets that detach from the wire electrode will generally contain a gas bubble, which is transported into the weld metal. These two welding processes were selected because there is no slag produced in the process. Slag slows down the cooling while giving enough time for degassing to occur, as in the case of shielded metal arc welding (SMAW) in air. Even with insufficient shielding gas, the autogenous GTAW welds did not exhibit porosity because there was no metal addition in the form of droplets. However, when a wire was fed into the arc, droplets detached from the wire in the oxidizing atmosphere transported gas into the weld pool, manifested as external and internal weld metal porosity. Similarly, the GMAW BOP welds exhibited internal porosity. When quenched in water, the droplets that detached from the electrode in these oxidizing conditions exhibited internal voids. Metal transfer analysis performed on the GMAW BOP welds associated short circuiting mode with large droplets and high porosity contents (10 pct.). Conversely, small droplets are expected to transport less gas and produce less porosity. Proof of concept welds using the pulsed current GMAW (GMAW-P) process resulted in higher droplet detachment frequency, smaller droplets and a low number of short circuiting droplets. Even though a few short circuiting events were still present, the GMAW-P process drastically reduced porosity to only 0.2 pct. Chemical reaction between oxygen and carbon generates CO gas at the bottom surface of the droplets in flat welding position, this gas ascends and is partially trapped inside the droplet. However, when the welding torch and base metal are rotated 90 degrees or in horizontal welding position, the CO gas generated escapes. Consequently there is no CO bubble in the pendant droplet or porosity in the weld metal. Wet welds were made with pulsed current using AWS E6010 electrode at a pressure equivalent to 50 m water depth. Porosity was reduced from 3.9 with constant current to 2.5 pct with pulsed current. Even when porosity was reduced with pulsed current, higher pulse frequency needs to be tested along with different peak and background current values to further reduce porosity. Flux covered electrodes with ferro-manganese, ferro-titanium and boron additions were extruded for wet welding. These electrodes produced wet welds with an average porosity of 1.2 pct., which could be further reduced to 0.85 pct. by better control of the arc at the beginning side of the weld.