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Roland Fischer - One of the best experts on this subject based on the ideXlab platform.

  • Fixation of manganese and iron in freshwater sediments through electrochemically initiated processes II: Process optimization
    Aquatic Sciences, 2006
    Co-Authors: Roland Fischer, Lothar Paul, Claudia Wolf, Thomas Deppe, Christian E. W. Steinberg, Axel Wobus
    Abstract:

    It has been shown that it is possible to electrochemically immobilize iron (Fe) and manganese (Mn) in sediments due to the formation of a redox- and pH-barrier. This paper describes the influences of important operational and technical parameters on the procedure’s effectiveness. Voltage, degree of electrode covering of the sediment, distance between anode and cathode, electrode material and positioning of the electrode system significantly affect the process and were optimized. Optimum operation was achieved using High-Grade Steel electrodes driven with a voltage of U = 3–4 V, or carbon fleece electrodes with a voltage of U = 4–5 V (current density per electrode area I/AE = 0.02–0.05 mA/cm^2). Fast and complete immobilization of Fe and Mn occurred at an electrode covering 12% of the sediment surface. No significant improvement was achieved at higher electrode- sediment area ratios. An optimum distance of about 10 cm between anode and cathode was determined. Temporary initial mobilization of Fe and Mn was found at greater electrode distances. The positioning of the electrode system relative to the sediment surface significantly affected the remobilization of Fe and Mn after the current was switched off. If the anode was placed in the sediment, a steep pH-gradient was formed between the aqueous phase and the anode region (ΔpH > 5), which considerably improved the immobilization of Fe and Mn. Low periodic turbulence at the sediment-water interface did not significantly influence the fixation of Fe and Mn.

  • Elimination of Heavy Metals from Leachates by Membrane Electrolysis
    Engineering in Life Sciences, 2004
    Co-Authors: Roland Fischer, H. Seidel, D. Rahner, P. Morgenstern, Christian Löser
    Abstract:

    The elimination of heavy metals from bioleaching process waters (leachates) by electrolysis was studied in the anode and cathode region of a membrane electrolysis cell at current densities of 5-20 mA/cm 2 using various electrode materials. The leaching waters containing a wide range of dissolved heavy metals, were high in sulfate, and had pH values of approx. 3. In preliminary tests using a rotating disc electrode the current density-potential curve (CPK) was recorded at a rotation velocity of 0, 1000 and 2000 rpm and a scan rate of 10 mV/s in order to collect information on the influence of transport processes on the electrochemical processes taking place at the electrodes. The electrochemical deposition-dissolution processes at the cathode are strongly dependent on the hydrodynamics. Detailed examination of the anodic oxidation of dissolved Mn(II) indicated that the manganese dioxide which formed adhered well to the electrode surface but in the cathodic return run it was again reduced. Electrode pairs of High-Grade Steel, lead and coal as well as material combinations were used to investigate heavy metal elimination in a membrane electrolysis cell. Using High-Grade Steel, lead and carbon electrode pairs, the reduction and deposition of Cu, Zn, Cr, Ni and some Cd in metallic or hydroxide form were observed in an order of 10-40 % in the cathode chamber. The dominant process in the anode chamber was the precipitation of manganese dioxide owing to the oxidation of dissolved Mn(II). Large amounts of heavy metals were co-precipitated by adsorption onto the insoluble MnO 2 . High-Grade Steel and to some extent lead anodes were dissolved and hence were proven unsuitable as an anode material. These findings were largely confirmed by experiments using combination electrodes of coal and platinized titanium as an anode material and Steel as a cathode material. With both electrode combinations and current densities of 5 or 10 mA/cm 2 , in the cathode region low depositions of 10-20% Cd, 2-10% Mn, 5-20 % Zn, 1-20 % Co and 5-15 % Ni were measured. By contrast, the elimination of other metals was substantially larger: Fe 40-60 %, Cu 20-40 %, and Cr 40-60 %. In the anode region the removal of heavy metals was in the order of 30-50%, with Mn being as high as 80 %. The anode materials exhibit good resistance at the current densities tested. The precipitates deposited in both electrode regions contained as main components Al with 10-20 %, Mg with approximately 10 %, and SO 4 with 5-20 %. The solid material in the cathode chamber consisted of relatively high proportions of Zn and Mn. Calcium in the solids indicated the co-precipitation of calcium sulfate. The main components in the solids of the anode chamber were Mn in the form of pyrolusite. Al as basic sulfate, and Mg. The results indicate that electrochemical metal separation in the membrane electrolysis cell can represent a practical alternative to the metal separation by alkalization. Regarding the main heavy metals Zn, Mn and Ni in the process water, combination electrodes using Steel as a cathode material and coal or platinized titanium as an anode material proved to be suitable for eliminating the heavy metals from the aqueous phase. However, for practical application, further work is necessary to improve the efficiency, applicability and costs of the process.

  • Elimination of heavy metals from process waters of the bioleaching process by electrolysis
    Journal of Soils and Sediments, 2002
    Co-Authors: Roland Fischer, H. Seidel, D. Rahner, P. Morgenstern, Christian Löser
    Abstract:

    The investigations into the membrane electrolysis cell show that electrochemical metal separation from bioleaching process waters can represent a practical alternative for metal separation by alcalization, Coal and platinized titanium material exhibit good anodic resistance at the current densities tested. By contrast, High-Grade Steel and to some extent lead anodes were dissolved and are hence unsuitable for this purpose. However, for practical application, suitable ways are required to discharge the precipitates containing heavy metals deposited on the electrodes from the electrolysis cell and to prevent membrane clogging. Regarding the main components zinc, manganese, and nickel, the combination electrodes proved to be suitable for eliminating the heavy metals from the aqueous phase.

  • Elimination of heavy metals from process waters of the bioleaching process by electrolysis
    Journal of Soils and Sediments, 2002
    Co-Authors: Roland Fischer, H. Seidel, D. Rahner, P. Morgenstern, Christian Löser
    Abstract:

    The investigations into the membrane electrolysis cell show that electrochemical metal separation from bioleaching process waters can represent a practical alternative for metal separation by alcalization, Coal and platinized titanium material exhibit good anodic resistance at the current densities tested. By contrast, High-Grade Steel and to some extent lead anodes were dissolved and are hence unsuitable for this purpose. However, for practical application, suitable ways are required to discharge the precipitates containing heavy metals deposited on the electrodes from the electrolysis cell and to prevent membrane clogging. Regarding the main components zinc, manganese, and nickel, the combination electrodes proved to be suitable for eliminating the heavy metals from the aqueous phase. Another way of treating diluted process waters containing sulphuric acidic and heavy metals is to concentrate the sulphuric acid in the anode region and to precipitate the heavy metals in the cathode region. The sulphuric acid recovered could then be returned to the leaching process, hence avoiding wastewater.

Christian Löser - One of the best experts on this subject based on the ideXlab platform.

  • Elimination of Heavy Metals from Leachates by Membrane Electrolysis
    Engineering in Life Sciences, 2004
    Co-Authors: Roland Fischer, H. Seidel, D. Rahner, P. Morgenstern, Christian Löser
    Abstract:

    The elimination of heavy metals from bioleaching process waters (leachates) by electrolysis was studied in the anode and cathode region of a membrane electrolysis cell at current densities of 5-20 mA/cm 2 using various electrode materials. The leaching waters containing a wide range of dissolved heavy metals, were high in sulfate, and had pH values of approx. 3. In preliminary tests using a rotating disc electrode the current density-potential curve (CPK) was recorded at a rotation velocity of 0, 1000 and 2000 rpm and a scan rate of 10 mV/s in order to collect information on the influence of transport processes on the electrochemical processes taking place at the electrodes. The electrochemical deposition-dissolution processes at the cathode are strongly dependent on the hydrodynamics. Detailed examination of the anodic oxidation of dissolved Mn(II) indicated that the manganese dioxide which formed adhered well to the electrode surface but in the cathodic return run it was again reduced. Electrode pairs of High-Grade Steel, lead and coal as well as material combinations were used to investigate heavy metal elimination in a membrane electrolysis cell. Using High-Grade Steel, lead and carbon electrode pairs, the reduction and deposition of Cu, Zn, Cr, Ni and some Cd in metallic or hydroxide form were observed in an order of 10-40 % in the cathode chamber. The dominant process in the anode chamber was the precipitation of manganese dioxide owing to the oxidation of dissolved Mn(II). Large amounts of heavy metals were co-precipitated by adsorption onto the insoluble MnO 2 . High-Grade Steel and to some extent lead anodes were dissolved and hence were proven unsuitable as an anode material. These findings were largely confirmed by experiments using combination electrodes of coal and platinized titanium as an anode material and Steel as a cathode material. With both electrode combinations and current densities of 5 or 10 mA/cm 2 , in the cathode region low depositions of 10-20% Cd, 2-10% Mn, 5-20 % Zn, 1-20 % Co and 5-15 % Ni were measured. By contrast, the elimination of other metals was substantially larger: Fe 40-60 %, Cu 20-40 %, and Cr 40-60 %. In the anode region the removal of heavy metals was in the order of 30-50%, with Mn being as high as 80 %. The anode materials exhibit good resistance at the current densities tested. The precipitates deposited in both electrode regions contained as main components Al with 10-20 %, Mg with approximately 10 %, and SO 4 with 5-20 %. The solid material in the cathode chamber consisted of relatively high proportions of Zn and Mn. Calcium in the solids indicated the co-precipitation of calcium sulfate. The main components in the solids of the anode chamber were Mn in the form of pyrolusite. Al as basic sulfate, and Mg. The results indicate that electrochemical metal separation in the membrane electrolysis cell can represent a practical alternative to the metal separation by alkalization. Regarding the main heavy metals Zn, Mn and Ni in the process water, combination electrodes using Steel as a cathode material and coal or platinized titanium as an anode material proved to be suitable for eliminating the heavy metals from the aqueous phase. However, for practical application, further work is necessary to improve the efficiency, applicability and costs of the process.

  • Elimination of heavy metals from process waters of the bioleaching process by electrolysis
    Journal of Soils and Sediments, 2002
    Co-Authors: Roland Fischer, H. Seidel, D. Rahner, P. Morgenstern, Christian Löser
    Abstract:

    The investigations into the membrane electrolysis cell show that electrochemical metal separation from bioleaching process waters can represent a practical alternative for metal separation by alcalization, Coal and platinized titanium material exhibit good anodic resistance at the current densities tested. By contrast, High-Grade Steel and to some extent lead anodes were dissolved and are hence unsuitable for this purpose. However, for practical application, suitable ways are required to discharge the precipitates containing heavy metals deposited on the electrodes from the electrolysis cell and to prevent membrane clogging. Regarding the main components zinc, manganese, and nickel, the combination electrodes proved to be suitable for eliminating the heavy metals from the aqueous phase.

  • Elimination of heavy metals from process waters of the bioleaching process by electrolysis
    Journal of Soils and Sediments, 2002
    Co-Authors: Roland Fischer, H. Seidel, D. Rahner, P. Morgenstern, Christian Löser
    Abstract:

    The investigations into the membrane electrolysis cell show that electrochemical metal separation from bioleaching process waters can represent a practical alternative for metal separation by alcalization, Coal and platinized titanium material exhibit good anodic resistance at the current densities tested. By contrast, High-Grade Steel and to some extent lead anodes were dissolved and are hence unsuitable for this purpose. However, for practical application, suitable ways are required to discharge the precipitates containing heavy metals deposited on the electrodes from the electrolysis cell and to prevent membrane clogging. Regarding the main components zinc, manganese, and nickel, the combination electrodes proved to be suitable for eliminating the heavy metals from the aqueous phase. Another way of treating diluted process waters containing sulphuric acidic and heavy metals is to concentrate the sulphuric acid in the anode region and to precipitate the heavy metals in the cathode region. The sulphuric acid recovered could then be returned to the leaching process, hence avoiding wastewater.

G. Demofonti - One of the best experts on this subject based on the ideXlab platform.

  • Fatigue Behavior of Girth Welded Joints of High Grade Steel Risers
    2020
    Co-Authors: E. Mecozzi, G. Demofonti, Hector Quintanilla, Alfonso Izquierdo, G. Cumino
    Abstract:

    Despite in the offshore area the use of high strength Steels is increasing, in fatigue design codes for welded joints no distinction between low, medium and high strength Steels is made; besides limited results are available about fatigue behavior of high strength Steels welded joints. To contribute to cover this lack of information the fatigue behavior of TENARIS X70 Steel welded risers was experimentally investigated and the results are hereby presented. Main finding was that the S-N curves and the cumulative damage limit generally recommended in the Standards could be too strict when high grade Steel welded joints are involved.

  • Crack arrestor design by finite element analysis for X100 gas transportation pipeline
    2020
    Co-Authors: Gianluca Mannucci, G. Demofonti, M. Di Biagio, Andrea Fonzo, Pietro Salvini, A Edwards
    Abstract:

    The interest of gas companies in the use of high grade Steel pipes, equivalent to X100 and higher, for the construction of long distance gas pipelines has become a consolidated trend in the world; in response to this market demand, Steel makers have successfully developed new classes of high grade Steel for large diameter pipelines, but some limitations might occur to their application if important aspects related to their structural reliability, such as the resistance to ductile fracture propagation, are not completely clarified. Recent efforts spent in investigating this aspect, that is the ductile fracture propagation control, have demonstrated that the class of X100 large-diameter Steel pipes being considered, when operated under severe operating conditions (high usage factor, rich gas, low temperature), may lie on the fracture propagation/arrest border line. In this case external mechanical devices, i.e. crack arrestors, may be required to ensure arrest of a propagating fracture This paper presents a crack arrestor design approach by finite element analysis for a X100, largediameter gas transportation line operating under severe conditions, such as those mentioned above. A CSM finite element model specifically developed for simulating dynamic ductile fracture propagation (PICPRO) has been used and implemented to consider the effect of crack arrestor constraint on the running fracture. Several types of crack arrestor have been considered, including a Steel sleeve with or without grout, thickerwalled pipe and types of composite crack arrestor, and relevant design criteria have been obtained. Numerical predictions were also compared with the results of recent experimental full-scale burst tests carried out on X100 large diameter pipelines, demonstrating the capability of the model developed to correctly predict the crack arrestor performance.

  • Onshore Pipeline High-Grade Steel for Challenge Utilization
    International Journal of Offshore and Polar Engineering, 2015
    Co-Authors: Jan Ferino, G. Demofonti, Andrea Fonzo, Massimo Di Biagio, Carlo Maria Spinelli, Spyros A. Karamanos
    Abstract:

    High-pressure pipeline transportation is one of the key technologies to connect remote gas fields and deliver gas at competitive prices to consumer markets. Arctic regions will become more attractive in the near future as large gas resources are located there. Long onshore pipeline systems, characterized by high-strength Steels (above API 5L grade X80, i.e., exceeding 555 MPa yield strength) operated at high internal gas pressure (more than 10–12 MPa) in many cases appear to be the most convenient transportation option. This paper highlights the latest follow-up from a long-lasting R&D program launched by Eni, together with industrial/technical partners, on the exploitation of commercially available options with High-Grade Steels for onshore applications even in harsh environments. The results obtained in this R&D program can be useful even for applications in Arctic onshore or offshore scenarios.

  • Development of a Reliable Model for Evaluating the Ductile Fracture Propagation Resistance for High Grade Steel Pipelines
    Volume 3: Materials and Joining, 2012
    Co-Authors: M. Di Biagio, G. Demofonti, Gianluca Mannucci, Carlo Spinelli, T. Schmidt
    Abstract:

    The recent experience on ductile fracture propagation control on gas pipelines has shown that the applicability of the Battelle Two Curve Method (based on Charpy-V energy) to high grade Steel pipes from API5L-X80 to X120 (ISO3183-L555M to L830M) operated at very high hoop stress values (≥500 MPa) is highly questionable.The reduced geometry of the specimen, the intrinsic low value of ductility of very high strength Steels, as low work-hardening and low value of the strain at maximum load are pointed out as the main causes of the mismatch.Starting from these assumptions a new EPRG (European Pipeline Research Group) project has been launched with the aim to develop, with reference to the ductile fracture propagation resistance, a suitable fracture parameter(s) with an associated laboratory methodology based on a simple sample which would be able to take into account the role of the ductility of the material on this specific fracture event.The present paper shows the approach adopted in this EPRG Project: an innovative approach based on “plastic damage model” which allows to describe the stable ductile crack propagation by means of stress-state parameters (named triaxiality and deviatoric parameters).Moreover the proposed “damage model” has been implemented inside a commercial finite element code and used to predict the fracture crack propagation behaviour of Single Edge Notch Bend (SENB) tests in terms of load-displacement diagram and residual plastic deformation.One of the main topics of this project was the application of this method to six selected grade Steels (with grades in the range of API X65 – X100) many of them coming from experimental full scale burst tests. The comparisons between experimental results and numerical simulations are substantially good; besides the results confirm that Charpy-V specimens, during the fracture propagation, work in different “constraint” conditions with respect to pipe and that DWTT specimen is in the middle between the two. Finally the “damage model approach” seems also able to discriminate between low and high grade Steels in terms of failure deformation at rupture. So it resulted very promising to quantify the role of both ductile of the Steel and geometrical constraint of the specimen in the ductile fracture propagation event.Copyright © 2012 by ASME

  • Circumferential welding of gas pipeline pipes using hybrid technology with fibre-delivered LASER beamPaper presented at the 4th National Welding Day, Workshop: “New frontiers in LASER beam welding, friction stir welding and electron beam welding proc
    Welding International, 2009
    Co-Authors: M. Fersini, G. Demofonti, S. Sorrentino, E. Mecozzi
    Abstract:

    In reducing the costs associated with the fabrication of new pipelines for transporting hydrocarbons (pipelines), circumferential joint welding activities have a significant impact on total cost per km. LASER–MIG hybrid welding (LB–GMAW), with fibre-optic LASER beam delivery, offers the opportunity for reducing fabrication costs, thanks to increased productivity, despite the higher initial investment. The aim of this work is to demonstrate the feasibility of pipeline fabrication using LB–GMAW hybrid welding technology for the circumferential welding of large diameter pipes (36″) for gas pipelines, on X100 High-Grade Steel with nominal thickness of 16 mm. Solid-state LASER systems with fibre-delivered LASER beam (Nd:YAG and Yb:SiO2) have been used in this study. The hybrid welding system has been shown to be of potential interest since, by guaranteeing adequate mechanical properties, it ensures increased productivity (reduced number of passes and increased welding speed).

W. Biegel - One of the best experts on this subject based on the ideXlab platform.

  • Correlation between structural, ferroelectric and dielectric properties of laser ablated (Pb0.92La0.08)(Zr0.65Ti0.35)O3 - thin-films on High-Grade Steel hastelloy
    Ferroelectrics, 2000
    Co-Authors: Ralph Klarmann, W. Biegel, Joachim Hemberger, Bernd Stritzker
    Abstract:

    Abstract High-Grade Steel Hastelloy was covered with (Pb0.92La0.08)(Zr0.65Ti0.35)O3 (PLZT) by Pulsed Laser Deposition (PLD). The direct deposition of the ferroelectric thin film on the substrate material - without additional buffer layers or bottom electrodes beneath the PZT - leads to a simple bicomponental system. The deposited films were characterized with respect to their structural properties (XRD, AFM) and showed excellent ferroelectric behavior [P(E) hysteresis]. Furthermore the fatigue, retention and ageing behavior of PLZT on Hastelloy was investigated and showed strong correlations to the structural measurements. Dielectric spectroscopy was used to investigate the frequency and temperature dependence of the permittivity e. These measurements were discussed with respect to the above mentioned points.

  • Deposition of Pb(Zr, Ti)O3-Films on High-Grade Steel Hastelloy and Modification by Ion Implantation
    MRS Proceedings, 1998
    Co-Authors: Ralph Klarmann, W. Biegel, B. Wörz, Joachim Hemberger, Bernd Stritzker
    Abstract:

    AbstractPulsed Laser Deposition (PLD) was used to deposit Pb(Zr,Ti)O3 thin films on High-Grade Steel Hastelloy. This material is suitable as substrate and electrode material as well. The deposited films were characterized with respect to their structural (XRD, RBS), topological (AFM) and their ferroelectric properties (P(E) hysteresis, retain and fatigue) which were found to be excellent. The ferroelectric properties in general, are sensitive to structural modifications and chemical doping and could therefore be influenced by ion implantation. Several species of ions (Ca+, O+) show different influence on the ferroelectric behavior and on the structural defects of the films. A subsequent annealing process can partially restore these modifications. The implanted Ca+ films were characterized by dielectric spectroscopy dependend on frequency and temperature to get information about ferroelectric domains.

  • Ferroelectric properties of Pb(Zr,Ti)O/sub 3/-films on technical substrates
    ISAF 1998. Proceedings of the Eleventh IEEE International Symposium on Applications of Ferroelectrics (Cat. No.98CH36245), 1998
    Co-Authors: R. Klarmann, W. Biegel, B. Stritzker
    Abstract:

    Pulsed laser deposition (PLD) was used to deposit Pb(Zr,Ti)O/sub 3/ (PZT) based oxide ceramics on various technical substrates (polycrystalline Al/sub 2/O/sub 3/, High-Grade Steel Hastelloy). Most work in the ferroelectric field up to now has been directed towards single crystalline substrates. For the purpose of a ferroelectric print-process application our research presently concentrates on technical and low-cost substrates.

  • Influence of ion implantation on the ferroelectric properties of Pb(Zr,Ti)O/sub 3/ films
    ISAF 1998. Proceedings of the Eleventh IEEE International Symposium on Applications of Ferroelectrics (Cat. No.98CH36245), 1998
    Co-Authors: W. Biegel, B. Wörz, R. Klarmann, M. Hanika, M. Kuhn, B. Schey, B. Stritzker
    Abstract:

    Pulsed laser deposition (PLD) was used to deposit Pb(Zr,Ti)O/sub 3/ (PZT) and (Pb,La)(Zr,Ti)O/sub 3/ (PLZT) thin films on YBa/sub 2/Cu/sub 3/O/sub 7-x/ (YBCO)//MgO and on technical substrates (High-Grade Steel Hastelloy). As a typical characterization of ferroelectric materials the P(E) hysteresis loop reflects the mobility of ferroelectric domain walls. We investigate the influence of ion implantation on the ferroelectric behaviour of thin PZT-films produced by PLD. The species of implanted ions (O/sup +/,Ca/sup +/) and the doses (10/sup 14/-10/sup 16/ cm/sup -2/, 180 keV) were varied to study the influence of the introduced atoms and defects on the ferroelectric properties. The films were investigated by XRD, RBS/Channeling and a RT-66A ferroelectric tester. The influence of thermal treatment of the implanted PZT-films on their ferroelectric properties will be discussed above the background of the induced structural defects and the implanted ions itself.

Trond Rogne - One of the best experts on this subject based on the ideXlab platform.

  • Carbide precipitation in HAZ of multipass welds in titanium containing and titanium free supermartensitic stainless Steels. Part 2 - Weld simulation studies
    Corrosion Engineering Science and Technology, 2020
    Co-Authors: E. Ladanova, Jan Ketil Solberg, Trond Rogne
    Abstract:

    AbstractTwo pass weld simulation has been used to investigate the precipitation mechanism of carbides in the coarse grained heat affected zones (HAZ) of two supermartensitic stainless Steels, one high grade Steel containing titanium and the other medium grade alloy without titanium. Recently, a model for such carbide precipitation has been proposed. According to this model, reheating of the HAZ in the martensitic stage is needed to provoke strong carbide formation. In the present work, the peak temperatures of the first and the second heating passes, the holding time during the second (reheating) pass and the holding temperature between the two passes have been varied in order to find the most favourable conditions for carbide precipitation in the two Steels. In addition, measurements of the chromium content across prior austenite grain boundaries have been made for the titanium free Steel.

  • Carbide precipitation in HAZ of multipass welds in titanium containing and titanium free supermartensitic stainless Steels Part 1 – Proposed precipitation mechanisms
    Corrosion Engineering Science and Technology, 2020
    Co-Authors: E. Ladanova, Jan Ketil Solberg, Trond Rogne
    Abstract:

    AbstractPrecipitation reactions in the coarse grained heat affected zone of high grade (0·1%Ti) and medium grade (Ti free) 13%Cr supermartensitic stainless Steels have been studied. During multipass welding, a high density of (Ti,Cr)C and (Cr,Fe,Mo,Si)23C6 particles formed at prior austenite grain boundaries in high and medium grade Steels respectively. Chromium depleted zones along prior austenite grain boundaries were found in the medium grade Steel, and these zones are assumed to be the reason for the well known sensitivity to intergranular corrosion of these Steels. After post-weld heat treatment the depletion was eliminated, explaining the improved corrosion resistance generally observed after such a treatment. The replacement of chromium carbides with titanium carbides in the high grade Steel explains the enhanced resistance to grain boundary corrosion generally observed in this type of Steel. A possible precipitation mechanism based on repeated heating during multipass welding is advanced for both ...