Tandem-MAG-welding of high strength steels for shipbuilding applications

Tämän työn tavoitteena oli hitsata tandem MAG –laitteistolla 25 mm paksua Ruukin E500 TMCP terästä. Työssä oli tarkoituksena vähentää railotilavuutta mahdollisimman paljon sekä suorittaa testihitsaukset 0.8 kJ/mm sekä 2.5 kJ/mm lämmöntuonneilla. Teoriaosuudessa käsiteltiin Tandem MAG-hitsaukseen, sen tuottavuuteen ja laatukysymyksiin liittyviä asioita sekä siinä perehdyttiin suurlujuusteräksien käyttöön hitsauksessa sekä laivanrakennuksessa. Kokeellisessa osuudessa perehdyttiin hitsauksessa huomattuihin etuihin, ongelmiin sekä ongelmien ratkaisumahdollisuuksiin. Hitsausliitoksen mekaaniset ominaisuudet tutkittiin rikkomattomin sekä rikkovin menetelmin. Alustavat hitsausohjeet luotiin kummallekin lämmöntuonnille. Testaukset aloitettiin 30 º railokulmalla pienentäen kulmaa mahdollisuuksien mukaan. Testauksissa ei saatu hitsattua onnistuneesti alle 30 º railokulmalla. Hitsaustestien aikana huomattiin magneettisen puhalluksen vaikutus hitsaustapahtumaan. Kaasunvirtausnopeuden tuli olla tietyn suuruinen jotta palkokerrokset onnistuivat ilman huokoisuusongelmaa. Pienemmällä lämmöntuonnilla hitsattaessa kaasunvirtausnopeudet olivat tärkeämpiä hitsatessa ylempiä palkokerroksia. Kääntämällä hitsauspoltinta sivuttaissuunnassa 7-10 astetta auttoi ehkäisemään reunahaavan syntymistä. Rikkovista menetelmistä testitulokset olivat hyväksyttyjä kaikkien muiden paitsi päittäishitsin sivutaivutuskokeen osalta.

Welding Equipment at the New York Trade School

Pictured is a P & H A.C. Arc Welder that would have been used to teach students in the Welding Department at the New York Trade School. Black and white photograph.

The Welding encyclopedia.

"Compiled and edited by": 1921-24, L.B. Mackenzie, H.S. Card; 1926-32, H.S. Card; 1938-41, "re-edited by" Stuart Plumley; 1943- "completely revised and re-edited by" T.B. Jefferson.

Effect of laser welding on the titanium composite tensile bond strength

The aim of this study was to analyze the shear bond strength between commercially pure titanium, with and without laser welding, after airbone-particle abrasion (Al2O3) and 2 indirect composites. Sixty-four specimens were cast and divided into 2 groups with and without laser welding. Each group was divided in 4 subgroups, related to Al2O3 grain size: A - 250 µm; B - 180 µm; C- 110 µm; and D - 50 µm. Composite rings were formed around the rods and light polymerized using UniXS unit. Specimens were invested and their shear bond strength at failure was measured with a universal testing machine at a crosshead speed of 2.0 mm/min. Statistical analysis was carried out with ANOVA and Tukey's test (α=0.05). The highest bond strength means were recorded in 250 µm group without laser welding. The lowest shear bond strength means were recorded in 50 µm group with laser welding. Statistically significant differences (p<0.05) were found between all groups. In conclusion, airborne particle abrasion yielded significantly lower bond strength as the Al2O3 particle size decreased. Shear bond strength decreased in the laser welded specimens.

Surface plasmon resonance of gold nanoparticles formed by cathodic arc plasma ion implantation into polymer

Shallow subsurface layers of gold nanoclusters were formed in polymethylmethacrylate (PMMA) polymer by very low energy (49 eV) gold ion implantation. The ion implantation process was modeled by computer simulation and accurately predicted the layer depth and width. Transmission electron microscopy (TEM) was used to image the buried layer and individual nanoclusters; the layer width was similar to 6-8 nm and the cluster diameter was similar to 5-6 nm. Surface plasmon resonance (SPR) absorption effects were observed by UV-visible spectroscopy. The TEM and SPR results were related to prior measurements of electrical conductivity of Au-doped PMMA, and excellent consistency was found with a model of electrical conductivity in which either at low implantation dose the individual nanoclusters are separated and do not physically touch each other, or at higher implantation dose the nanoclusters touch each other to form a random resistor network (percolation model). (C) 2009 American Vacuum Society. [DOI: 10.1116/1.3231449]

Biomass burning in Brazil`s Amazonian ""arc of deforestation"": Burning efficiency and charcoal formation in a fire after mechanized clearing at Feliz Natal, Mato Grosso

Estimates of greenhouse-gas emissions from deforestation are highly uncertain because of high variability in key parameters and because of the limited number of studies providing field measurements of these parameters. One such parameter is burning efficiency, which determines how much of the original forest`s aboveground carbon stock will be released in the burn, as well as how much will later be released by decay and how much will remain as charcoal. In this paper we examined the fate of biomass from a semideciduous tropical forest in the ""arc of deforestation,"" where clearing activity is concentrated along the southern edge of the Amazon forest. We estimated carbon content, charcoal formation and burning efficiency by direct measurements (cutting and weighing) and by line-intersect sampling (LIS) done along the axis of each plot before and after burning of felled vegetation. The total aboveground dry biomass found here (219.3 Mg ha(-1)) is lower than the values found in studies that have been done in other parts of the Amazon region. Values for burning efficiency (65%) and charcoal formation (6.0%, or 5.98 Mg C ha(-1)) were much higher than those found in past studies in tropical areas. The percentage of trunk biomass lost in burning (49%) was substantially higher than has been found in previous studies. This difference may be explained by the concentration of more stems in the smaller diameter classes and the low humidity of the fuel (the dry season was unusually long in 2007, the year of the burn). This study provides the first measurements of forest burning parameters for a group of forest types that is now undergoing rapid deforestation. The burning parameters estimated here indicate substantially higher burning efficiency than has been found in other Amazonian forest types. Quantification of burning efficiency is critical to estimates of trace-gas emissions from deforestation. (C) 2009 Elsevier B.V. All rights reserved.

Linoleic acid peroxidation and lignin degradation by enzymes produced by Ceriporiopsis subvermispora grown on wood or in submerged liquid cultures

Ceriporiopsis subvermispora is a white-rot fungus used in biopulping processes and seems to use the fatty acid peroxidation reactions initiated by manganese-peroxidase (MnP) to start lignin degradation. The present work shows that C. subvermispora was able to peroxidize unsaturated fatty acids during wood biotreatment under biopulping conditions. In vitro assays showed that the extent of linoleic acid peroxidation was positively correlated with the level of MnP recovered from the biotreated wood chips. Milled wood was treated in vitro by partially purified MnP and linoleic acid. UV spectroscopy and size exclusion chromatography (SEC) showed that soluble compounds similar to lignin were released from the milled wood. SEC data showed a broad elution profile compatible with low molar mass lignin fractions. MnP-treated milled wood was analyzed by thioacidolysis. The yield of thioacidolysis monomers recovered from guaiacyl and syringyl units decreased by 33% and 20% in MnP-treated milled wood, respectively. This has suggested that lignin depolymerization reactions have occurred during the MnP/linoleic acid treatment. (C) 2009 Elsevier Inc. All rights reserved.

Sigma phase morphologies in cast and aged super duplex stainless steel

Solution annealed and water quenched duplex and super duplex stainless steels are thermodynamically metastable systems at room temperature. These systems do not migrate spontaneously to a thermodynamically stable condition because an energy barrier separates the metastable and stable states. However, any heat input they receive, for example through isothermal treatment or through prolonged exposure to a voltaic arc in the welding process, cause them to reach a condition of stable equilibrium which, for super duplex stainless steels, means precipitation of intermetallic and carbide phases. These phases include the sigma phase, which is easily identified from its morphology, and its influence on the material`s impact strength. The purpose of this work was to ascertain how 2-hour isothermal heat treatments at 920 degrees C and 980 degrees C affect the microstructure of ASTM A890/A890M GR 6A super duplex stainless steel. The sigma phase morphologies were found to be influenced by these two aging temperatures, with the material showing a predominantly lacy microstructure when heat treated at 920 degrees C and block-shaped when heat treated at 980 degrees C. (C) 2009 Elsevier Inc. All rights reserved.

Characterisation of electric arc furnace dust generated during plain carbon steel production

Electric arc furnace (EAF) dust is a waste generated in the EAF during the steel production process. Among different wastes, EAF dust represents one of the most hazardous, since it contains heavy metals such as Zn, Fe, Cr, Cd and Pb. The goal of the present work is to characterise the waste through chemical analysis, particle size distribution, X-ray diffraction (XRD), scanning electron microscopy coupled with energy dispersive spectroscopy detection and thermal analysis. The waste sample is composed essentially of spherical particles and has a very small particle size and the majority of the identified elements were Fe, Zn, Ca, Cr, Mn, K and Si. The XRD has presented compounds such as ZnO, ZnFe2O4, Fe2O3, MnO, SiO2, FeFe2O4 and MnAl2O4. According to the thermal analysis results, up to 1000 degrees C the total weight loss was similar to 5%. The results of waste characterisation are very important to these further investigations.

Carotenoids production from a newly isolated Sporidiobolus pararoseus strain by submerged fermentation

This work aimed at evaluating the total carotenoids production by a newly isolated Sporidiobolus pararoseus. Bioproduction was carried out in an orbital shaker, using 10% (w/v) of inoculum (25 A degrees C, 180 rpm for 35 h), incubated for 120 h in a dark room. Liquid N(2) and dimethylsulphoxide (DMSO) were used for cell rupture, and carotenoids were extracted with a solution of acetone/methanol (7:3, v/v). Optimization of carotenoids bioproduction was achieved by experimental design technique. Initially, a Plackett-Burman design was used for the screening of the most important factors, after the statistical analysis, a complete second-order design was carried out to optimize the concentration of total carotenoids in a conventional medium. Maximum concentration of 856 mu g/L of total carotenoids was obtained in a medium containing 60 g/L of glucose, 15 g/L of peptone, and 15 g/L of malt extract, 25 A degrees C, initial pH 4.0 and 180 rpm. Fermentation kinetics showed that the maximum concentration of total carotenoids was reached after 102 h of fermentation and that carotenoids bioproduction was associated with cell growth.

Welding and rheomorphism of phonolitic fallout deposits from the Las Canadas caldera, Tenerife, Canary Islands

The Las Canadas caldera is a nested collapse caldera formed by the successive migration and collapse of shallow magmatic chambers. Among the pyroclastic products of this caldera are phonolitic fallout deposits that crop out in the caldera wall and on the extracaldera slopes. These deposits exhibit an uninterrupted facies gradation from nonwelded to lava-like and record continuous volcanic deposition. Densely welded and lava-like facies result from the extreme attenuation and complete homogenization of juvenile clasts that destroy original clast outlines and any evidence of fallout deposition. Agglutination contributes significantly to the final degree of flattening observed in the welded facies. After deposition, rheomorphic flowage occurs. Emplacement temperatures for one of the welding sequences are calculated from magmatic temperatures and a model of tephra cooling during fallout. Results are 486 degreesC for the nonwelded facies and 740 degreesC for the moderately welded facies. For the same welding sequence, a cooling time between 25 and 54 days is estimated from published experimental and computational data as the possible duration of welding and rheomorphism. Following deposition and agglutination, the lava-like pyroclastic facies had the rheological properties of viscous lavas and flowed down the outer slopes away from the caldera. Some lava-like masses detached from proximal areas to more distal regions. During deposition, the eruptive style evolved from Plinian fallout to fountain-fed spatter deposition. This evolution was accompanied by a decrease in explosive power and a lower height of the eruptive column, which produce higher emplacement temperatures and more effective heat retention of pyroclasts.

Comparison of deposited surface area of airborne ultrafine particles generated from two welding processes

This article describes work performed on the assessment of the levels of airborne ultrafine particles emitted in two welding processes metal-active gas (MAG) of carbon steel and friction-stir welding (FSW) of aluminium in terms of deposited area in alveolar tract of the lung using a nanoparticle surface area monitor analyser. The obtained results showed the dependence from process parameters on emitted ultrafine particles and clearly demonstrated the presence of ultrafine particles, when compared with background levels. The obtained results showed that the process that results on the lower levels of alveolar-deposited surface area is FSW, unlike MAG. Nevertheless, all the tested processes resulted in important doses of ultrafine particles that are to be deposited in the human lung of exposed workers.