DOCSLIB.ORG

Analysis of Inclusions in Submerged Arc Welds in Microalloyed Steels

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Analysis of Inclusions in Submerged Arc Welds in Microalloyed Steels Analysis of Inclusions in Submerged Arc Welds in Microalloyed Steels The level of weld bead acicular ferrite is found to be less in Ca-treated vs. Ca-free base metal of the same composition BY A. R. BHATTI, M. E. SAGGESE, D. N. HAWKINS, J. A. WHITEMAN, AND M. S. GOLDING Introduction ered the importance of inclusion crystal­ In this study, a range of weld beads lography. Others (Refs. 8, 9) do not share made on API 5LX65 base material have Toughness requirements for arctic this view and have instead concentrated been investigated to simulate the high grade line pipe have become increasingly on the indirect effect that inclusion chem­ dilution situation in practical pipe manu­ more stringent with the advent of tech­ istry may have on hardenability. ln their facture. Two base metals were selected nological demanding applications. This view, acicular ferrite is apparently devel­ with similar composition and low sulphur has led to developments in steel technol­ oped when the threshold value of 1.1 content, with one plate having under­ ogy giving increased through-thickness wt-% Mn is exceeded in the weld metal gone inclusion modification by calcium properties, with a move to low sulphur matrix. treatment. Three welding wires were steels and inclusion control by the use of selected; they were Oerlikon Welding rare earth treatments (e.g., Ca). Industries' S2, SD3Mo and Tibor 22 (con­ It has been shown (Ref. 1) that these taining microalloyed additions of Ti and B, Table 1—Base Metal Composition, wt-% types of steels provide excellent resis­ and identified as no. 22 elsewhere in this tance to hydrogen-induced cracking paper). The submerged arc fluxes cov- Ca-free Ca-treated (HIC) in sour gas environments. However, steel processing variables such as calcium C 0.052 0.060 treatment can have an indirect effect on Mn 1.37 1.45 the properties obtained in submerged arc Si 0.224 0.142 Table 2—Base Metal Microstructural Features weld metal in terms of generating a S 0.005 0.006 microstructural phase — acicular ferrite — P 0.018 0.024 which is known to optimize toughness Ni 0.003 0.003 Microstructural Base metal Cr 0.032 0.032 properties in unrefined weld metal. It is feature Ca-free Ca-treated Mo 0.012 0.007 known that the formation of acicular Nb 0.036 0.032 Ferrite, % 96 91 ferrite is favored in a particular range of Cu 0.34 0.32 Pearlite, % 4 9 oxygen content; however, there is some V 0.069 0.070 Ferrite grain 6.15 6.55 disagreement regarding the factors favor­ Sn 0.007 0.006 size, Mm ing the formation of this phase. Al(sol) 0.054 0.025 Pearlite colony 3.57 6.88 Many authors (Refs. 2-6) think that N 0.003 0.006 size, /am inclusions play an important role in nucle­ ation. In this case, the controlling factors, in determining the effectiveness of inclu­ sions as nucleants, are volume fraction Table 3—Welding Wire Composition, Wt-% and size distribution. More recently, a some workers (Ref. 7) have also consid- Element S2 SD3Mo No. 22< > C 0.10 0.10 0.10 Mn 1.06 1.60 1.19 Si 0.22 0.13 0.04 Based on a paper presented at the 64th Annual s 0.012 0.012 0.010 AWS Convention in Philadelphia, Pennsylva­ p 0.013 0.007 0.008 nia, on April 29, 1983. Ni 0.07 0.08 Cr 0.03 0.10 A. R. BHATTI is a Research Fellow and D. N. Mo 0.47 0.30 HAWKINS and J. A. WHITEMAN are Senior Cu 0.11 Lecturers, Sheffield University, England; M. E. Ti 0.043 SAGGESE is with CNEA Argentina, and M. S. B 0.004 GOLDING is Technical Services Manager, Oer­ likon Welding (Ireland) Limited, Dublin. (a) Marketed by Oerlikon Welding Industries Ltd.. Houston 224-s I JULY 1984 ered a range of basicities (Ref. 10) from Base Metal Effect acid to fully basic; these were flux A with Figure 2 shows the percentage of acic­ a basicity index (Bl) = 3.1, flux B with ular ferrite (AF) plotted against the basici­ Bl = 1.8, and flux C with Bl = 0.6. ty index (Bl) of the flux with both welding wire and base metal composition as inde­ pendent variables. Weld metal micro- Experimental structure in Ca-free base metal always had a larger proportion of acicular ferrite All the beads were deposited under than that in the Ca-treated base metal; identical conditions: process — sub­ however, the decrease in acicular ferrite merged arc welding, current —600 A, level is influenced by the flux-welding m voltage —32 V, speed —460 mm/min wire combination. With the microalloyed (18.1 ipm), and heat input (HI)-2.5 kj/ no. 22 welding wire, the reduction is mm (62.5 kj/in.). relatively small, regardless of the flux The base metals were 16 mm (0.63 in.) basicity index. For the other two welding thick, and details of their chemistry and wires, flux B with the basicity of 1.8 microstructure are given in Tables 1 and produces the greatest decrease. This flux, 2. The compositions of the filler metals when used with S2 welding wire, gives a and fluxes used are presented in Tables 3 low acicular ferrite content even when and 4, respectively. used on a Ca-free base metal. The acicular ferrite level in each weld metal was quantified by point counting Wire Effect using the schemes proposed by Abson and Dolby (Ref. 11) and Pargeter (Ref. For the whole range of welds exam­ Fig. 1 — Typical microstructural features ob­ 12). The types of inclusions were exam­ ined, use of the no. 22 welding wire always gave improved acicular ferrite served in the weld metal: A — Ca-free base ined by means of a Philips 400 electron metal; B — Ca-treated metal microscope, fitted with EDAX and STEM levels with little change resulting from changes in the flux type. This behavior is facilities, using carbon extraction repli­ large for an interstitial atom, boron readi­ in agreement with previously published cas. ly segregates to atomically strained literature (Refs. 13, 14, 15) on Ti- and The replica technique was best suited regions; very small quantities (typically B-containing consumables. for this work. This is because mean inclu­ <50 ppm in the deposit) will reduce the sion size was less than 0.5 nm, and any Additions of boron and titanium are energy of these sites and hence inhibit other technique using bulk specimens known to promote acicular ferrite forma­ grain boundary ferrite nucleation. would have been severely affected by tion. It is presumed that boron carries out the role of minimizing grain boundary interaction with the matrix. The inclusions Flux Basicity were further line-scanned along their ferrite nucleation, while titanium protects diameters to determine their internal vari­ boron from oxygen and nitrogen due to Referring to Fig. 2, it can be seen that ation in chemical composition. This tech­ its strong deoxidizing potential. In addi­ there is no relationship between the AF nique was also employed to analyze the tion, titanium (as TiO) is proposed to level and the basicity index of the flux. extraction replicas taken from the base enhance acicular ferrite nucleation (Refs. Although the best results are those given metals. Diffraction work was also under­ 16, 17). by fully basic flux A, the worst ones are taken to study any crystallographic The beneficial effect of boron results not given by the acid flux but by the nature of the inclusions. from its small atomic size. It is present as semi-basic flux B. These results are con­ an interstitial solute and is, therefore, trary to those reported in the literature relatively mobile. Since it is comparatively (Refs. 8, 16-17, 18); however, they would Results and Discussion Metallography Table 4-—Results of Flux Analyses The typical microstructural features (Fig. 1) observed in these welds were: Ra<;iritv Composition, wt-% 3 1. Acicular ferrite (AF). Flux index' ' Si02 + Ti02 CaO + MgO Al203 + MnO CaF2 2. Grain boundary ferrite (CF). 3. Polygonal ferrite (PF). A 3.1 15 35 20 25 4. Ferrite with aligned martensite, aus­ B 1.8 22 30 25 21 C 0.60 27 1 51 14 tenite or carbide (MAC). The percentage of acicular ferrite for - MgO + BaO + Na 0 + K 0 + ViMnO B, = Ca°^ 2 2 the welds studied are shown in Table 5. Si02 + Vi (Al203 + Ti02 + Zr02) Table 5—Percentages of Acicular Ferrite (AF) in Weld Microstructures FlNvnn»nd No. 22 welding wire SD3Mo welding , wire S2 welding wire basicity Ca-free Ca-treated Ca-free Ca-treated Ca-free Ca-treated index (Bl) base metal base metal base metal base metal base metal base metal 1 (Bl = 3.1) A-85% AF B-76% AF C-69% AF H-64% AF M-70% AF N-68% AF 2 (Bl = 1.8) C-70% AF D-65% AF 1-61% AF 1-17% AF 0-35% AF P-16% AF 3 (Bl = 0.6) E-78% AF F-65% AF K-73% AF L-61% AF WELDING RESEARCH SUPPLEMENT 1225-s seem to support the findings of Terashi­ ma and Hart (Ref. 19) where high levels of acicular ferrite were generated in a higher oxygen content. It is well known that there is a direct so correlation between basicity index of the flux and weld metal oxygen content. This relationship holds for the present series of welds examined as can be seen in Fig.
Load more

Recommended publications
  • A Study on the Acicular Ferrite Formation in Steel Weld Metals for Gas Metal Arc Welding*
    ［溶接学会論文集 第 38 巻 第 2 号 p. 6s-10s （2020）］ A study on the acicular ferrite formation in steel weld metals for gas metal arc welding* by Kyohei Uto**, Koyo Nakayama**, Yuji Kisaka***, Fumiaki Kimura***, Hidenori Terasaki**** Characteristics of oxide inclusions in steel weld metals with varying acicular ferrite (AF) fractions, which were produced by gas metal arc welding using controlled CO2 (10%, 30%, and 50%) and titanium contents (by placing ultra-fine Ti wire), were statistically investigated. The correlation between identified phases in the oxide inclusions and AF formation was discussed from the viewpoint of AF formation mechanism. For high AF fraction samples, we confirmed that all oxide inclusions include Mn-Si-Al-Ti-O amorphous phases. By contrast, an amorphous phase was never observed for low AF fraction samples. Additionally, we confirmed that a few of the amorphous oxides created a Mn-depleted zone (MDZ), which suggested that the MDZ formed by Mn-Si-Al-Ti-O amorphous phase stimulates AF formation. Key Words: acicular ferrite, gas metal arc welding, inclusion, amorphous, manganese depleted zone, spinel oxides 1. Introduction around inclusions are believed to enhance the transformation driving force to ferrite and promote AF nucleation. However, Acicular ferrite (AF) in low-carbon steel weld metals is contradictory findings have been reported, in which MDZs were regarded as the most desirable microstructure with respect to not observed around Ti2O3 and MnTi2O4 which are generally strength and toughness. Hence, research on the mechanism of AF believed to form MDZs.7, 8) Although Ti-containing oxides are formation is required to further improve the mechanical properties expected to play an important role in AF formation, discrepancies of steel weld metals.
    [Show full text]
  • Advanced Welding Processes: Technologies and Process Control
    i Advanced welding processes ii Related titles: New developments in advanced welding (ISBN-13: 978-1 85573-970-3; ISBN-10: 1-85573-970-4) Recent developments in high-technology areas have significantly transformed the welding industry where automation, computers, process control, sophisticated scientific instruments and advanced processing methods are all common. Today’s engineers and technologists have to support complex systems and apply sophisticated welding technologies. This comprehensive book discusses the changes in advanced welding technologies, preparing the reader for the modern industry. MIG welding guide (ISBN-13: 978-1-85573-947-5; ISBN-10: 1-85573-947-X) Gas metal arc welding (GMAW), also referred to as MIG (metal inert gas) welding, is one of the key processes in industrial manufacturing. The MIG welding guide provides comprehensive, easy-to-understand coverage of this widely used process. The reader is presented with a variety of topics from the choice of shielding gases, filler materials, welding equipment and lots of practical advice. The book provides an overview of new developments in various processes such as: flux-cored arc welding; new high-productive methods; pulsed MIG welding; MIG-brazing; robotic welding applications and occupational health and safety. This will be essential reading for welding engineers, production engineers, designers and all those involved in industrial manufacturing. Cumulative damage of welded joints (ISBN-13: 978-85573-938-3; ISBN-10: 1-85573-938-0) Fatigue is a mechanism of failure that involves the formation of cracks under the action of different stresses. Fatigue cracks are exceedingly difficult to see, particularly in the early stages of crack growth.
    [Show full text]
  • Formation of Fine Microstructure in Weld Metal Containing Mn-Ti Based Oxides Hidenori NAKO＊1, Yoshitomi OKAZAKI＊1, Dr
    Formation of Fine Microstructure in Weld Metal Containing Mn-Ti based Oxides Hidenori NAKO＊1, Yoshitomi OKAZAKI＊1, Dr. Hitoshi HATANO＊1, Ken YAMASHITA＊2, Hideaki TAKAUCHI＊2 *1 Materials Research Laboratory, Technical Development Group *2 Welding Process Dept., Technical Center, Welding Business The formation of fine acicular ferrite microstructure and the inclusion. This is a concept focusing on the toughness improvement have been observed in a welding structural energy component of the interface energy metal in which inclusion particles containing Mn-Ti and has been studied for a long time.8), 11) In recent based oxide are dispersed. The inclusion particles are years, researches based on chemical energy have also 12) composed of MnTi2O4 , TiO2 , amorphous and MnS phases, been conducted. while the acicular ferrite has been nucleated from the (2) A compositional change of austenite phase MnTi2O4 phase. The Baker-Nutting crystal orientation around inclusions: This is the theory that the relationship has been found between MnTi2O4 phase and composition of the austenite phase around acicular ferrite, whereas the Kurdjumov-Sachs orientation inclusions changes before the AF is generated such relationship has been found between the prior austenite that the driving force for AF generation increases. phase and acicular ferrite. It has been discovered that The Mn-depleted zone is cited as an example.13) the favorable lattice matching at the interface between the It has been shown that, when Mn, an austenite prior austenite phase and acicular ferrite may possibly stabilizing element, is absorbed by inclusions, have promoted the nucleation and growth of acicular a Mn-depleted zone is formed in the vicinity of ferrite, as well as the lattice matching at the MnTi2O4 / the inclusions, raising the Ae3 temperature.
    [Show full text]
  • INVESTIGATION of LOW OXYGEN HSLA STEEL WELD METAL By
    INVESTIGATION OF LOW OXYGEN HSLA STEEL WELD METAL by Drew White A thesis submitted to the Faculty and the Board of Trustees of the Colorado School of Mines in partial fulfillment of the requirements for the degree of Master of Science (Metallurgical and Materials Engineering). Golden, Colorado Date: _____________ Signed: _______________________ Drew White Signed: _______________________ Dr. Stephen Liu Thesis Advisor Golden, Colorado Date: _____________ Signed: _______________________ Dr. Angus Rockett Professor and Head of George S. Ansell Department of Metallurgical and Materials Engineering ii ABSTRACT Hot-wire gas tungsten arc welding is a process gaining more popularity in industry today due to increased deposition rate, from the resistively heated filler metal introduced by an external wire feed system. A modified version of this system, which incorporates an oscillation mechanism to modify the frequency with which the filler metal enters the molten weld pool was utilized in this work and the effect of varying process parameters on microstructure, weld bead morphology, and inclusion size and distribution are characterized. Hot-wire amperage, wire feed speed, frequency of wire oscillation and heat input were varied on seven wire consumables to determine their effects on acicular ferrite. Optimal microstructural development in high strength low alloy steel weldments is mainly dependent on acicular ferrite, which nucleates on oxide inclusions. However, with the gas tungsten arc process, it is difficult to manipulate weld pool oxygen content to achieve the needed level for optimal acicular ferrite formation. The oxide inclusion population is investigated to determine the morphology, size and spatial distribution and whether they served as nucleation sites for ferrite formation.
    [Show full text]
  • Friction Stir Welding of EH46 Steel Grade at Dwell Stage: Microstructure Evolution
    Friction Stir Welding of EH46 Steel Grade at Dwell Stage: Microstructure Evolution M. Al-moussawi, J. Smith and M. Faraji Accepted author manuscript deposited in Coventry University Repository Original citation: Al-moussawi, M; Smith, J. and Faraji, M. (2017) Friction Stir Welding of EH46 Steel Grade at Dwell Stage: Microstructure Evolution Metallography, Microstructure, and Analysis (6) 6, 489-501. DOI: 10.1007/s13632-017-0390-5 http://dx.doi.org/10.1007/s13632-017-0390-5 Springer US This is a post-peer-review, pre-copyedit version of an article published in Metallography, Microstructure, and Analysis. The final authenticated version is available online at: http://dx.doi.org/10.1007/s13632-017-0390-5 Copyright © and Moral Rights are retained by the author(s) and/ or other copyright owners. A copy can be downloaded for personal non-commercial research or study, without prior permission or charge. This item cannot be reproduced or quoted extensively from without first obtaining permission in writing from the copyright holder(s). The content must not be changed in any way or sold commercially in any format or medium without the formal permission of the copyright holders. Friction Stir Welding of EH46 steel grade at Dwell Stage: Microstructure Evolution *1 M. Al-moussawi, *2 A.J Smith, 3M. Faraji *1,2Sheffield Hallam University/MERI/UK, 3Coventry University *[email protected] +447462954845 *2 [email protected] Abstract This work investigated the effect of changes in Friction Stir Welding (FSW) process parameters on the resulting microstructure. In particular the effect of the plunge depth and tool rotational speed, during the "dwell" period was investigated in this work.
    [Show full text]
  • Scott Maceachern, David A. Scott, Molly O'guinness Carlson & Jean
    IRON ARTEF A CTS FROM THE DGB-1 SI TE , NORTHERN CA MEROON : CONSERV A T I ON , MET A LLUR gi C A L AN A LYS I S A N D ETHNO A RCH A EOLO gi C A L AN A LO gi ES Scott MacEachern, David A. Scott, Molly O'Guinness Carlson & Jean-Marie Datouang Djoussou Abstract Résumé In 2008, a number of iron artefacts were recovered from En 2008, des objets en fer ont été mis au jour dans une an interior courtyard on the DGB-1 site during fieldwork cour intérieure de DGB-1, un très grand site multifon- in 2008. DGB-1 is a large multi-function site located in the ctionnel se trouvant dans le nord des monts Mandara northeastern Mandara Mountains of Cameroon, and dat- camerounais et datant du milieu du deuxième millénaire ing to the mid-second millennium AD. The iron artefacts après J-C. Ces objets comprenaient un ensemble de poin- recovered included a cache of spear/arrow points found tes de lance/flèche constituant un dépôt enterré sous un buried under a living floor, as well as a local hoe and a niveau d’occupation, ainsi qu’une chaîne à maillons et chain and a ‘barrette’ probably not of local provenance. une barrette, probablement allochtone ainsi qu’une houe This discovery has a number of points of interest: (1) de provenance locale. Cette découverte présente plu- ethnoarchaeological reenactments of iron smelts in the sieurs intérêts : (1) l’occasion rare de comparer, sur cinq 1980s in the same region provide a rare opportunity for siècles environ, des techniques sidérurgiques en Afrique comparison of iron-working techniques over about five sub-saharienne grâce aux réactivations de la réduction centuries in sub-Saharan Africa; (2) the variability in de fer réalisées en contexte ethnoarchéologique dans les different forms of iron (including eutectoid steel) used in années 1980 dans la même région, (2) la variabilité des these artefacts; and (3) the welding of different forms of différentes qualités de fer (y compris l’acier eutectoïde) iron to produce composite artefacts.
    [Show full text]
  • On the Formation Potential of Acicular Ferrite Microstructure in Different Steel Grades Focusing on the Influence of Carbon Content
    On the Formation Potential of Acicular Ferrite Microstructure in Different Steel Grades Focusing on the Influence of Carbon Content Denise Loder1, Alexander Mayerhofer2, Susanne Katharina Michelic3 1Montanuniversitaet Leoben Franz-Josef-Strasse 18, 8700 Leoben, Austria Phone: +43 3842 402-2205 Email: [email protected] 1Montanuniversitaet Leoben Franz-Josef-Strasse 18, 8700 Leoben, Austria Phone: +43 3842 402-2228 Email: [email protected] 1Montanuniversitaet Leoben Franz-Josef-Strasse 18, 8700 Leoben, Austria Phone: +43 3842 402-2214 Email: [email protected] Keywords: Acicular ferrite, Microstructure, Non-metallic inclusions, Carbon content, High temperature laser scanning confocal microscopy (HT-LSCM) INTRODUCTION Since the 1970s comprehensive effort was spent on the explanation of the acicular ferrite formation. Acicular ferrite (AF) nucleates intragranularly on non-metallic inclusions. The needle or lenticular shaped plates radiate in various directions and create a chaotic, interlocking microstructure. The growth of acicular ferrite grains is diffusionless, but excess carbon is rejected to the remaining austenite shortly after transition. The carbon enriched austenite transforms during the ongoing cooling process to perlite, bainite or martensite, or remains as retained austenite in the final structure. The created multiphase microstructure provides excellent mechanical properties, most notably toughness, so that acicular ferrite steels are of increasing interest for steel producers. In literature four main nucleation mechanisms are described: destruction of the crystal structure, creation of dislocation arrays, reduction of lattice mismatch and chemical changes in the local matrix. Literature suggests that a combination of at least two effects is responsible for the nucleation of acicular ferrite, but the exact impact of the mechanisms is not completely understood yet.1–8 Acicular ferrite formation is mainly influenced by the steel composition, cooling rate, non-metallic inclusions and austenite grain size.
    [Show full text]
  • Effect of Welding Heat Input on Microstructures and Toughness in Simulated CGHAZ of V–N High Strength Steel
    Materials Science & Engineering A 577 (2013) 161–168 Contents lists available at SciVerse ScienceDirect Materials Science & Engineering A journal homepage: www.elsevier.com/locate/msea Effect of welding heat input on microstructures and toughness in simulated CGHAZ of V–N high strength steel Jun Hu a,n, Lin-Xiu Du a, Jian-Jun Wang b, Cai-Ru Gao a a The State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang 110819, China b Institute of Materials Research, School of Material and Metallurgy, Northeastern university, Shenyang 110819, China article info abstract Article history: For the purpose of obtaining the appropriate heat input in the simulated weld CGHAZ of the hot-rolled Received 23 December 2012 V–N microalloyed high strength S-lean steel, the microstructural evolution, hardness, and toughness Received in revised form subjected to four different heat inputs were investigated. The results indicate that the hardness decreases 9 April 2013 with increase in the heat input, while the toughness first increases and then decreases. Moderate heat Accepted 11 April 2013 input is optimum, and the microstructure is fine polygonal ferrite, granular bainite, and acicular ferrite Available online 19 April 2013 with dispersive nano-scale V(C,N) precipitates. The hardness is well-matched with that of the base metal. Keywords: Moreover, the occurrence of energy dissipating micromechanisms (ductile dimples, tear ridges) Simulated weld CGHAZ contributes to the maximum total impact energy. The detrimental effect of the free N atoms on the Heat input toughness can be partly remedied by optimizing the microstructural type, fraction, morphologies, and Misorientation grain boundary crystallographic characteristics.
    [Show full text]
  • Acicular Ferrite Formation and Its Influencing Factors - a Review
    Journal of Materials Science Research; Vol. 6, No. 1; 2017 ISSN 1927-0585 E-ISSN 1927-0593 Published by Canadian Center of Science and Education Acicular Ferrite Formation and Its Influencing Factors - A Review Denise Loder1, Susanne K. Michelic1 & Christian Bernhard1 1 Chair of Ferrous Metallurgy, Montanuniversitaet Leoben, 8700 Leoben, Austria Correspondence: Susanne K. Michelic, Chair of Ferrous Metallurgy, Montanuniversitaet Leoben, 8700 Leoben, Austria. Tel: 0043-384-2402-2214. E-mail: [email protected] Received: November 10, 2016 Accepted: November 19, 2016 Online Published: December 31, 2016 doi:10.5539/jmsr.v6n1p24 URL: http://dx.doi.org/10.5539/jmsr.v6n1p24 Abstract Acicular ferrite is a microstructure nucleating intergranularly on non-metallic inclusions and forming an arrangement of fine, interlocking grains. This structure is known to improve steel properties, especially steel toughness, essentially. The formation of acicular ferrite is mainly affected by steel composition, cooling rate, inclusion landscape and austenite grain size. In recent decades, extensive research has been conducted to investigate these factors. The present paper provides an overview of the impact of published results and the state of knowledge regarding acicular ferrite formation. Special attention is paid to the effect of carbon, manganese and titanium addition to steel, as well as the optimum size, number and composition of non-metallic inclusions. In addition, the reactions during the nucleation and growth of acicular ferrite needles are briefly addressed. Further, characteristics of acicular ferrite and bainite are summarized, which should help to distinguish these similar structures. Keywords: acicular ferrite, cooling rate, non-metallic inclusion, steel 1. Introduction At the beginning of the 1990s, Takamura and Mizoguchi (1990) introduced the concept of Oxides Metallurgy, which focuses on the use of oxidic inclusions to improve the quality of the final product and stabilize the production process.
    [Show full text]
  • Control of Weldability Per Hansson
    Control of weldability Research leading to the development of two new quenched and tempered tool steels. Per Hansson Dissertation TRITA-IIP-04-12 ISSN 1650-1888 Chair of Welding Technology Department of Production Engineering Royal Institute of Technology Stockholm 2004 Preface After obtaining the MSc Met engr the present author worked with projects on weldability research at the Swedish Institute of Metals Research (SIMR) in Stockholm. At the same time Dr´s courses and classes were taken at KTH on welding technology. After five years of basic welding technological research at the SIMR the field of product development in the steel industry tempted and the author came to work with product development of quenched and tempered steels with rather high hardnesses/strength levels such as abrasion resistant steels, armour plate and the like. The similarity between the work regarding HAZ hardenability and the hardenability of quenched and tempered steels may at a glance not be obvious, but the HAZ in a weldment is indeed a quencher in miniature and the principles of materials behaviour in the HAZ in a weldment and the behaviour of a plate being quenched in a quencher are basically the same. What was gained in knowledge during the early years was to be the leading star for the product development of the quenched and tempered steels. Finally, two new tool steels have been developed with low carbon contents for being tool steels although high in carbon for weldable steels. Here the principles for hardenability have been used both in the sense of producing a quench and tempered steel according to rules formalised by Grossman and his colleagues and with use of the hardenability equations set up first by Dearden and O´Neill.
    [Show full text]
  • Achieving Ultrafine-Grained Ferrite Structure in Friction Stir Processed
    Materials Letters 162 (2016) 161–164 Contents lists available at ScienceDirect Materials Letters journal homepage: www.elsevier.com/locate/matlet Achieving ultrafine-grained ferrite structure in friction stir processed weld metal P. Xue a,n, Z.Y. Ma a, Y. Komizo b, H. Fujii b a Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016, China b Joining and Welding Research Institute, Osaka University, 11-1 Mihogaoka, Ibaraki, Osaka 567 0047, Japan article info abstract Article history: Ultrafine-grained (UFG) ferrite phase was the desired structure in the weld metal of high strength low Received 7 June 2015 alloy (HSLA) steel joints. In this study, submerged arc weld metal of a HSLA steel was subjected to friction Received in revised form stir processing (FSP) under a very low rotation rate of 80 rpm. The original coarse bainite structure was 21 September 2015 changed into UFG ferrite structure after FSP, and the grain sizes were refined to about 500 and 300 nm in Accepted 27 September 2015 the upper and lower parts of the processed zone, respectively. This study provides an effective strategy to Available online 30 September 2015 preparing UFG ferrite structure in the weld metal of HSLA steel joints, and also a potential welding Keywords: method. Friction stir processing & 2015 Elsevier B.V. All rights reserved. Ultrafine-grained structure Weld metal Microstructure Recrystallization 1. Introduction Friction stir processing (FSP) is a new thermo-mechanical processing technology based on the principles of friction stir In the fabrication of high strength low alloy (HSLA) steel welding (FSW) [6].
    [Show full text]
  • Metallurgical and Mechanical Characterization of Low Carbon Steel—Stainless Steel Dissimilar Joints Made by Laser Autogenous Welding
    metals Article Metallurgical and Mechanical Characterization of Low Carbon Steel—Stainless Steel Dissimilar Joints Made by Laser Autogenous Welding Elena Scutelnicu 1 , Mihaela Iordachescu 2 , Carmen Catalina Rusu 1,* , Danut Mihailescu 1 and José Luis Ocaña 3 1 Manufacturing Engineering Department, Faculty of Engineering, “Dunarea de Jos” University of Galati, 800008 Galati, Romania; [email protected] (E.S.); [email protected] (D.M.) 2 Materials Science Department, E.T.S. de Ingenieros de Caminos, Canales y Puertos, Universidad Politécnica de Madrid, 28040 Madrid, Spain; [email protected] 3 Laser Centre, Universidad Politécnica de Madrid, 28031 Madrid, Spain; [email protected] * Correspondence: [email protected]; Tel.: +40-336-130-208 Abstract: This paper addresses the metallurgical and mechanical characterization of dissimilar joints made by laser autogenous welding between thin sheets of low-carbon steel (CS) and austenitic stain- less steel (SS). The welding technology applied, previously optimized to produce sound dissimilar joints, is based on the heat source displacement from the weld gap centerline towards CS, in order to reduce the SS overheating. The research includes optical microscopy observations, energy dispersive X-ray analysis (EDX) to assess the wt% of Cr, Ni, and Fe in all regions of the dissimilar welded joint, hardness measurements, and tensile tests of transverse-welded flat specimens. In comparison with classical determination of the joint overall mechanical characteristics, the novelty of this research Citation: Scutelnicu, E.; Iordachescu, consists of experimental assessment of the local mechanical behavior of the fusion and heat affected M.; Rusu, C.C.; Mihailescu, D.; Ocaña, zones by using a digital image correlation technique (VIC-2D).
    [Show full text]