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This scientific paper aims to determine the optimal economic roughness of galvanized surfaces by studying the influence of turning surface roughness on the quality of galvanizing. The thickness of the zinc layer, its corrosion resistance, and the precision of the galvanized parts were also examined. S235J0 steel samples were processed using a turning operation to obtain different roughness values. Three galvanizing technologies, galvanic galvanizing, hot dip galvanizing, and hot dip galvanizing with centrifugation, were used in the experiments. The surface evolution from turning to zinc layer deposition was monitored, and parts were subjected to salt spray corrosion resistance testing. Statistical analysis confirmed the stability of the technologies used and the accuracy of the experimental data. Optimal roughness ranges for galvanizing were determined based on the quality of the surface before galvanizing and the galvanizing technology used. The findings show that avoiding small roughness values leads to savings in the machining phases. From the dimensional accuracy perspective, the parts have smaller dimensions after galvanizing, and the dimensional accuracy decreases. The study confirms that steel parts are protected from corrosion, and degradation of the zinc layer is more advanced in sections with less roughness. The optimal surface roughness values before galvanizing were determined to be Ra < 3.657 m in the case of HDG, Ra < 3.344 m in the case of HDG+C, and Ra > 2.928 μm in the case of ZP. The conclusions drawn from this study introduce new directions of research.

The nucleation and growth of oxides formed on Fe-Mn (1 wt.%) binary alloy during annealing were investigated. The recrystallized samples were heated to 800°C and kept at this temperature for 60 s in N2 / H2 (5 vol.%) with a dew point of-40°C. The heating process was also interrupted at different temperatures, namely 650, 700, 750 and 800°C. The annealed samples were then observed by scanning electron microscopy. Image analysis was performed to obtain the surface density and size of the oxides. The influence of the ferrite grain orientation on the oxides’ nucleation and growth was studied by Electron Back Scattered Diffraction. The annealed Fe-Mn surfaces were covered by oxide crystals whose shape, surface density and size strongly depended on the underlying ferrite grain orientation. The oxides’ nucleation occurred first on Fe {110} grain, their surface density was the largest on Fe {100}, and their size was the largest on Fe {110}.

International audience; Welding of high strength steels containing martensite is difficult due to the appearance of brittle grains after fast cooling. Galvanizing spot-welded specimens made of AISI410 solves this problem, and strongly improves the performances of spot welds. The mechanisms responsible for these achievements are presently analyzed. The changes of the mechanical strength and fatigue toughness of spot-welded samples made of AISI410 after galvanizing have been studied. AISI410 is a chromium-rich martensite. Tensile tests on normalized specimens indicate that the yield stress is close to 1010 MPa and the UTS at similar to 1270 MPa. The fatigue limit of raw AISI410 is at 690 MPa (Delta sigma(L) at R=0.1). Specimens were cut following the rolling direction and spot-welded. Metallography reveals that spot welding produces: - hard martensite at the center of the nugget; - a heat affected zone, which has been forged by the welding electrodes and recrystallized at high temperature; - and finally, a ring of grains tempered in a subcritical temperature range. Spot welds were tested in tensile-shear mode. Both overload failure and fatigue toughness were evaluated. Annealing and galvanizing post-treatment have been used to improve the mechanical properties of the spot-welded specimens. The improvement of the mechanical performances of spot-welded specimens after post-treatments are reported as follows. First, we observed significant changes in the modes of rupture both in overload failure and fatigue tests. The mechanical strength of untreated spot welds is controlled by the brittleness of the nugget and the forged heat affected zone. After post-treatment, the ultimate tensile strength is increased, and rupture results from fissures propagating exclusively into the zone recrystallized in the subcritical range of temperature. This mode is genuine to spot welds in martensite because of the high strength of the base metal. Second, three modes of rupture depending on the force range control the fatigue toughness. Annealing and galvanizing modify the ranges. Galvanizing increases the endurance, and the fatigue limit by a factor similar to 3.5. This effect is attributed to zinc brazing that strongly changes the distribution of stresses under tensile-shear solicitation. Hardness measurements and tensile test on specific samples clarify the mechanical behavior of the layers around the spot, and shed some light on the mechanisms of rupture. Lifetimes are controlled by the initiation of fatigue cracks.

An electrochemical reactor was developed to recover zinc from the spent pickling solutions coming from the hot dip galvanizing industry. These solutions mainly contain ZnCl2 and FeCl2 in aqueous HCl media. The effect of the applied potential on the figures of merit (fractional conversion, current efficiency, space-time yield and specific energy consumption) of the electrochemical reactor was analysed. Voltammetric experiments were performed previously in order to select the optimum conditions to be applied in the electrolysis experiments. From the I-V curves it was inferred that bulk zinc deposition started from potential values more cathodic than -0.99 V. The hydrogen evolution reaction (HER) appeared from -0.45 V and masked the zinc cathodic peak C1, related to bulk zinc deposition, at high HCl concentrations. The presence of HCl inhibited iron deposition in synthetic samples. The additives present in the real baths, which diminish the massive hydrogen generation, allowed the observation of peak C1. The potential values to be applied in the electrolysis experiments were chosen from the voltammetric experiments and ranged between -1 V and -1.75 V. In the absence of iron in solution, as the electrode potential was shifted towards more negative values, the space-time yield of zinc and its fractional conversion increased because of the increase in the electrode roughness and the hydrogen turbulence-promoting action. Simultaneously, the specific energy consumption decreased initially due to the increase in the zinc conversion rate but decreased for the most cathodic potential value due to HER. The presence of iron in synthetic solutions led to a decrease in current efficiency associated with the reverse redox Fe 2+/Fe3+ system and to the enhancement of the HER, which also induced increments in the local pH and the subsequent zinc redissolution for the most cathodic potential values. On the contrary, the additives present in the real spent pickling baths avoided the adverse effects of iron, and zinc electrodeposition was possible even at high cathodic potential values. In fact, a potential value of -1.75 V was selected as the optimum since the conversion, the current efficiency and the space time yield obtained in the real baths were relatively high., Authors want to express their gratitude to the Universidad Politecnica de Valencia for the economical support in the project reference PAID-06-08, and to the Generalitat Valenciana for the financing of the project reference GV/2010/029.

International audience; Protecting the modern high strength steels against corrosion is a challenge because the coating technology must be compatible with forming and must preserve the mechanical performances. Batch galvanizing after hot stamping could provide a simple solution to this complex problem. A commercial high strength martensitic steel containing 13 wt. % Cr, 0.35 wt. % Si, 0.3 wt. % Mn and 0.15 wt. % carbon has been galvanized with a commercial zinc alloy. Galvanizing produces a ~15 µm thick coating that is bright, continuous and metallurgically bonded. The intermetallic layer is made of ς crystals, which forms an open 3-dimensional structure. Tin, nickel and aluminium are found able to moderate the Sandelin effect. Comparison with other steels galvanized the same way indicates that chromium slows down the kinetics of the metallurgical reaction. Chromium distributes both in the ς and η phases, and follows a diffusion-like profile in the coating. The nickel from the alloy concentrates in the Fe-Zn intermetallic compound. Aluminium segregates at the surface and interface. It also provides a gettering effect that fixes silicon in sub-micron particles dispersed in the ς and η phases. Tensile experiments and fatigue tests demonstrate that the mechanical performances of the martensitic steel are preserved after coating. Comparison with similar experiments performed on a TRIP800 steel indicates that using galvanized martensitic steel is best worth in static applications.; La protection des nouveaux aciers à haute résistance mécanique contre la corrosion est un défi parce que la technologie de dépôt doit être compatible avec la mise en forme par emboutissage et elle doit préserver les propriétés mécanique du substrat. La galvanisation à façon après mise en forme et construction est une solution simple et élégante. Nous avons galvanisé un acier martensitique contenant 13 % de chrome dans un alliage de galvanisation commercial. La galvanisation produit un revêtement de ~15 µm, continu, adhérent et brillant. La couche d'intermétallique contient essentiellement la phase ς ; elle forme dans le revêtement une microstructure à 3D. Le chrome se distribue à la fois dans la couche intermétallique et dans la couche de zinc superficielle. Le nickel contenu dans l'alliage de galvanisation se concentre dans le composé intermétallique à l'interface. L'aluminium ségrège à la fois à l'interface et à la surface du revêtement; La corrélation entre les distributions de concentration de l'aluminium et du silicium suggère que l'aluminium produit un effet getter qui fixe le silicium dans des petites particules dispersées à la fois dans la phase intermétallique et dans le zinc. Les essais de traction et de fatigue indique que la galvanisation a préservé les propriétés mécaniques de l'acier, et en particulier celles de la martensite. L'acier galvanisé pourrait être avantageusement utilisé pour les applications statiques.

Galvanized hot rolled steel sheets are inferior to cold rolled sheets because of the segregation of carbides at the surface/sub-surface region. In order to change the distribution of the carbides at the surface/sub-surface region, continuous annealing/reheating operation is carried out at different temperatures prior to the galvanizing operation. The reheating temperature maintained in continuous annealing line is the main factor which redistributes the carbides at the surface/sub-surface region. At intercritical annealing temperature all the carbides get dissolved into the matrix and the surface became suitable for galvanizing reaction. The reducing atmosphere also plays an important role to remove all the room temperature oxides present at the surface. Thus, a combination of proper temperature and reducing atmosphere leads to the proper galvanizing on the hot rolled steel surface. � 2009 Elsevier B.V. All rights reserved.

The zinc coated steel sheet has been mostly used for automobile and other industries because of its high corrosion resistance. This paper deals with the development of new ceramics support roll used for a continuous galvanizing pot to manufacture stable galvanizing steel sheet. Usually stainless steel rolls coated by tungsten carbide are used to support and stabilize the strip in a continuous galvanizing pot, which is filled with molten zinc. However, corrosion and abrasion arise on the roll surface only in a few weeks, and causing the deterioration of quality of plating. Although developing all-ceramics rolls is most desirable, risk of fracture has to be reduced when the ceramic roll dips into molten metal. In this paper, therefore, how to reduce the thermal stress is considered when the ceramic rolls are installed in molten metal using finite volume method and finite element method. The usefulness of silicon nitride having extremely high conductivity is also discussed.

The main purpose of employing pre-coated steel sheets is to minimize corrosion of steel. However, coatings can be severely affected by forming processes. In the forming processes, due to the different modes of deformation, the strain levels are different and so can affect the properties of the coatings to a varying degree. Special attention has to be paid to the influence of deformation conditions on the performance of the coating, as regards protection against corrosion. The adhesion of the coating must remain good, and the surface should not be damaged during forming. Therefore, it is necessary to study the behavior of its corrosion resistance against the deformation. In this work, effect of strain path on the corrosion behavior of hot-dip galvanized steel sheets has been studied. Corrosion behavior of hot-dip galvanized steel sheets at various strain levels has been evaluated under four different strain paths namely, biaxial, plane strain, uniaxial (drawing) and tensile modes. The sheets were deformed by a limiting dome height test (LDH) set-up. A correlation between the degree of deformation and the loss in extent of corrosion protection offered by the coating has been established by carrying out electrochemical studies such as potentiodynamic polarization and impedance spectroscopy (EIS) in 3.5% NaCl solution. The present study shows that increase in deformation increases the extent of delamination of the coating for all the modes of deformation. The severity of deformation on delamination, however, has been found to vary in the order of, tensile < uniaxial < plane < biaxial., © Elsevier

This thesis investigates the wall pressure distributions of the single-slot impinging jet and multiple-slot impinging jet as a function of various parameters and compares the results obtained with the computational study of Tamadonfar [2010]. The process of gas wiping is used in many industrial applications such as tempering of the plate glass, the chemical mixing process, and turbine blade cooling. One of the most important industrial applications of gas jet wiping is the production of galvanized steel strip in a continuous hot-dip galvanizing line. In this process, an impinging jet is used to remove the excess zinc alloy from the steel strip and control the final coating weight by applying wall pressure and shear stress on the moving substrate emerging from the bath of molten zinc. Changing the various operating parameters such as jet Reynolds number (Re), the jet to strip distance (z), the jet slot width (d), and jet inclination angles (α) allows manufacturers manipulate the final coating weight on the substrate. Production of high quality sheet steels, which have a very thin coating weight and high uniformity quality, is one of the goals of the automotive industry. In order to obtain thinner and more uniform coating weight, a new model of impinging jet which is comprised of one main jet with two auxiliary jets, one on each side of the main jet, called a multiple-slot impinging jet, is of considerable interest. For the current study, a multiple-slot impinging jet was designed and manufactured and measurements were performed for both the single-slot impinging jets, the current model used in continuous hot-dip galvanizing lines, and the multiple-slot impinging jet subjected to a wide range of gas wiping parameters which include the main jet Reynolds number (Rem), the auxiliary jet Reynolds number (Rea), and the plate-to-nozzle ratio (z/d). A comparison between the measured results obtained for the two impinging jet configurations and the numerical results by Tamadonfar [2010] has been provided. The similarities and differences between the experimental and numerical results are presented and discussed. Master of Science in Mechanical Engineering (MSME)

Este trabajo pretende desarrollar la complejidad de iniciar un nuevo proyecto en una empresa, analizando los resultados y buscando soluciones óptimas en caso de que no se cumplan los objetivos fijados. El proyecto consiste en poner en marcha una nueva línea de galvanizar en continuo, consiguiendo un nuevo producto final para la empresa. Para llegar a esta meta, se ha seguido la normativa europea UNE-EN10244 [1], que se debe cumplir para la comercialización del producto, teniendo en cuenta los recursos y posibilidades de los que dispone la empresa. También se ha tenido que adaptar la línea a las condiciones actuales que presenta el funcionamiento interno de la empresa, como el uso de productos específicos, adaptarse el espacio disponible o controlar parámetros de producción requeridos.

Aquest Projecte Final de Carrera s’ha realitzat a partir d’un projecte d’autorització ambiental fet durant el primer semestre de 2011 a una consultoria ambiental, especialitzada en empreses de tractament i revestiment de metalls. Amb el present projecte es vol desenvolupar tot el procediment necessari per adquirir l’autorització ambiental de l’empresa PROFICA SL, emmarcada dins de l’annex I de la Llei 20/2009, del 4 de desembre, de prevenció i control ambiental de les activitats (DOGC nº 5524, 11.12.2009). Es presenten els diferents requeriments que s’ha de presentar davant l’administració competent, la Generalitat de Catalunya, per tal que l’empresa PROFICA SL obtingui la resolució de la autorització ambiental, i poder així exercir la seva activitat. Aquests requeriments són: sol·licitud, formulari tècnic, estudi d’impacte ambiental, projecte bàsic, documentació preceptiva sobre accidents greus, informe urbanístic i informe de les característiques del sòl. Per altra banda, també està inclòs en aquest projecte final de carrera el projecte de protecció contra incendis de l’empresa doncs tot i que no és un requisit per obtenir l’autorització, s’ha de presentar conjuntament.