No description available.

The intention with this thesis was to evaluate how much pickling that have been achieved on aluminium details in the pickling bath before the anodization in an anodization process. As there were no earlier studies to use around pickling before anodization, statistical experimental design was chosen as planning tool. Statistical experimental design was used to plan the experiments in an organized way and to evaluate how the pickling process works together with the main effects and the interaction effects. Detailed scientific studies were performed on how aluminium is prepared and how the anodization process works. The studies were performed in reference books. Three different methods were designed. The first method, method 1, was based on a fractional factorial design with four design variables, temperature, sodium hydroxide and aluminium concentrations and the time the details was submerged into the pickling bath. The aluminium details was made from a square profile pipe. There was nine experiments performed in method 1. The measurements on the pickling was performed in two ways, first with a dial indicator where the pickling was compared with a reference surface before and after, and another method also performed with a dial indicator, where the measurements was performed over the edge between the pickled surface and the reference surface. A statistical control calculation was done on the surface smoothness of the square profile pipes. The control showed that the standard deviation was 11 µm. Method 2 was based on a complete factorial design where the design variables was temperature and the time the details was submerged into the pickling bath. All aluminium details were homogenous. There were seven experiments performed in method 2. The measurements on the pickling was performed in two ways, first with a dial indicator where the pickling was compared with a reference surface before and after, and another method also performed with a dial indicator, where the measurements was performed over the edge between the pickled surface and the reference surface. A statistical control calculation was done on the surface smoothness of the homogenous details. The control showed that the standard deviation was 14 µm. Method 3 was designed in a different way than method 1 and 2. In method 3 one experiment was performed and the design variable which was changed was the time when the details was submerged into the pickling bath. The aluminium details had the form of homogenous cubes. The measurements on the pickling was performed by measuring the weight of the details on an analytical scale before and after the pickling, and then calculate the pickling in µm in two different ways. The first way was to use the atomic radius of aluminium and the second way was to use the size of the unit cell of aluminium. The two first methods gave very different results than the third method. The result for method 1 showed very random values with great dispersion which resulted in a non-detectable pickling. The result for method 2 was very similar to the result from method 1, very random values with great dispersion and no pickling was detectable with any confidence. The result from method 3 gave a theoretical calculated result for the pickling, when the aluminium details was submerged in the pickling bath for 1 minute, and based on the atomic radius of aluminium, of 1,52 µm and with the same conditions but using the unit cell of aluminium showed a pickling of 1,62 µm. When the aluminium details were submerged in the pickling bath for 3 minutes, the theoretical calculation with the atomic radius of aluminium gave that the pickling was 4,51 µm and with the same conditions but using the unit cell of aluminium showed a pickling of 4,79 µm.

The following paragraphs contain the conclusions drawn from this investigation. 1. The rate of attack on the bare metal increases with increasing temperature; particularly in the pickling of black stovepipes steel in 18.3 percent sulfuric acid solution where the rate of attack on the bare metal at 75°F is 0.097 milligrams per square inch per minute, while at 142°F the rate of attack is 0.51 milligrams per square inch per minute. 2. The time required to remove the surface oxide from the sample decreases with increasing temperature. 3. The 18.75 percent phosphoric acid solution removed the most surface oxide in the least amount of time at 165 and 177 °F. 4. The effect of Rodine 50 inhibitor on 20.5 percent hydrochloric acid pickling solution cannot be studied because the rate of attack on the bare metal of uninhibited pickling solution was too small, at 80 °F. 5. The addition of Rodine 82-A inhibitor to a pickling bath containing 18.5 percent sulfuric acid decreased the rate of attack on the bare metal from 0.0858 milligrams per square inch per minute to 0.0286, without appreciably affecting the time required to remove this scale, at 78 °F. 6 No valid conclusions can be made concerning the life of the Rodine 82-A inhibitor because of the erratic nature of the results. / M.S.

No description available.

Stainless steels were first developed in the early 20th century and have since then emerged as a very diverse class of engineering materials. Along with steels having new combinations of properties, there is a continuous development of new technologies allowing the material to be produced in a faster and more energy effcient manner. A prerequisite for new technologies to be adapted quicklyis a fundamental understanding of the microstructure evolution throughout theprocess chain. The first part of this thesis has been dedicated to the annealing and pickling processes from a process-microstructure perspective. In the second part the concept of utilising crystallographic texture as a way to attain microstructures with new combinations of properties has been evaluated. In the first part, annealing can be regarded as a high temperature oxidation process, resulting in chromium depletion that necessitate subsequent chemical pickling. Chemical pickling, on the other hand, is basically a wet-corrosion process and hence more difficult for highly corrosion-resistant grades. The chromium depleted layer was found to be enriched in austenite in case of duplex stainless steel UNS S32205 (Paper I) and this may inuence the pickling process. Proper pretreatment like shot-blasting dramatically increases the pickling rate because it provides the pickling acid with access to the chromium depleted layer (Paper II). Oxidation kinetics for S30400 in conditions relevant to strip annealing do not seem to be affected by the choice of air/oxygen as oxidiser even though the latter results in substantially higher water content (Paper III). This gives new possibilities regarding both cost savings and increased throughput. In the second part, the effect of crystallographic texture on resistance towards corrosion of S31603 in a solution of FeCl3 and AlCl3 in ethanol/glycerol and in 30 vol% H2SO4 is investigated. In the former, high density surfaces {1111} and {100} are less prone for pit nucleation, however the effect is relativelysmall. In H2SO4 pronounced crystallographic anisotropy is observed inwhich the corrosion rate increase in the order {111} &lt; {110} ≤ {100} (Paper IV).For corrosion at high temperatures, chromium diffusion is governed by randomhigh angle boundaries with ~20—55° misorientation. The possibilities to alter the texture in austenitic stainless steels by means of warm-rolling and annealing has been evaluated for S30403 and S31603. During warm-rolling, both steels develop the copper-type texture in contrast to the brass-type texture observedat room temperature. However only S30403 is prone to recrytallise cube texture during subsequent annealing (Paper V). / <p>QC 20150121</p>

Works created within the engineering studies in collaboration with IDEAL-Trade service discusses the influence of pickling acids on steel material and on the same material with powder coated . Based on the literature study and consultations with employees of the company were designed each experiment, investigators removal and acid corrosion attack , another verify adhesiveness powder coatings for various periods of exposure pickled material. Experiments and tests were carried out in companies ECOS , ITS and faculty FSI.

The oxide scale created during manufacturing of stainless steel is often removed by a chemical pickling with mixed acid. Various pre-treatments to pickling are also applied to increase the efficiency of the oxide scale removal. Shot blasting is one such pre-treatment, which operates to remove a certain amount of oxide and also to generate cracks and openings for the subsequent pickling. In this work, three materials, AISI 2205, 430 and 304 have been blasted and later exposed to mixed acid. This was conducted to quantify the effect shot blasting has on the subsequent pickling of stainless steel. Three shot products and two blasting parameters were investigated and varied. Shot blasting significantly reduced the oxide scale but was unable to remove the chromium oxide layer closest to the steel surface. No significant difference was observed when comparing the result from the three shot products after blasting. Increasing the particle velocity or the coverage rate further enhanced the pickling but reduced the amount of oxide removed during blasting. These effects are however relative small, so in practise relatively mild conditions seems preferable for economic reasons. Oxide scale containing hematite was difficult to remove by both shot blasting and pickling.

Lors de l’élaboration des aciers plats inoxydables, un recuit haute température de courte durée (60 s environ), sous atmosphère oxydante (O2/H2O/CO2/N2) est mis en place après laminage à froid. Ce recuit entraîne la formation d’une couche d’oxyde de faible épaisseur qui est éliminée par un décapage. Ces étapes de recuit et décapage peuvent entraîner une perte de qualité du produit fini, se traduisant par une perte de brillance. L’acier bistabilisé Ti, Nb (AISI 441) est sensible à la dégradation de surface. L’objectif de la thèse est d’identifier les phénomènes à l’origine de la perte de brillance. Les travaux menés consistent à étudier les couches d’oxyde et le comportement de l’acier lors du décapage. Une morphologie originale de l’interface interne avec la présence de protrusions métalliques a été observée. L’étude des protrusions par la microscopie électronique à balayage couplée à une sonde ionique focalisée : MEB-FEG/FIB, a permis de proposer un mécanisme décrivant leur formation. Ce mécanisme s’appuie sur la précipitation de la silice qui semble également être un élément clé pour comprendre la dégradation de surface. Un lien entre perte de brillance et teneur en chrome dans le substrat a été établi. La déchromisation de l’acier liée au recuit est susceptible d’être facilitée par les protrusions. / During the industrial processing line of stainless steel flat products, a short annealing (60 s) at high temperature in a gas furnace-oxidizing atmosphere (O2/H2O/CO2/N2) takes place after cold rolling. This annealing leads to the formation of a thin oxide film which is then removed by a pickling step at the end of the process. The annealing and pickling stages may cause a loss of gloss, resulting in a loss of product quality. The steel bistabilizied Ti, Nb (AISI 441) is sensitive to this surface degradation. The aim of this thesis is to identify the phenomena leading to the loss of gloss. Our work consists in studying the oxide layers and the behavior of steel during pickling. A peculiar morphology of the internal interface with the presence of metallic protrusions was observed. The protrusions investigation using a scanning electron microscopy coupled with a focused ion beam: MEB-FEG/FIB, allowed us to propose a mechanism of their formation. This mechanism is based on the precipitation of silica which also appears to be a key point to understand the surface degradation. A link between the loss of gloss and the chromium content in the substrate was established and the chromium depletion related to the annealing is likely to be facilitated by protrusions.

Orientador: Itamar Ferreira / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-18T17:02:04Z (GMT). No. of bitstreams: 1 Uehara_AndreYugou_M.pdf: 4445631 bytes, checksum: ba69e40eee3a8de5233ab826f19564d7 (MD5) Previous issue date: 2011 / Resumo: Este trabalho tem por objetivo investigar a etapa de decapagem ácida e os processos de desidrogenação e retrabalho realizados durante a zincagem de parafusos quanto à fragilização por hidrogênio. Parafusos fabricados conforme a norma JIS B 1127 (1995), cementados, de 6 mm de diâmetro e 16 mm de comprimento de rosca foram organizados em 39 diferentes grupos. A decapagem foi avaliada quanto ao volume de ácido clorídrico (700 ml, 900 ml e 1000 ml) e presença, ou ausência, de inibidor para este ácido, utilizando tempos de decapagem de 15, 30, 45 e 60 minutos para cada condição de volume de ácido e inibidor utilizados. A desidrogenação foi avaliada utilizando parafusos decapados (solução: 1000 ml de ácido, ausência de inibidor e decapados por 15, 30, 45 e 60 minutos) e desidrogenados a uma temperatura de 1000C e tempo total de processo de 1, 2 e 3,5 horas. O retrabalho foi avaliado utilizando parafusos de 8 ?m de espessura de camada zincada, retrabalhados por 4 minutos em 700 ml de ácido, ausência de inibidor e 300 ml de água, avaliando as hipóteses do retrabalho único e duplo sem desidrogenação e do retrabalho único seguido de desidrogenação (1000C - 2 horas). Ensaios de pré-carregamento para a detecção da fragilização por hidrogênio foram realizados em parafusos que sofreram as preparações citadas, sendo o torque de ruptura avaliado nestes parafusos, assim como naqueles obtidos após o tratamento térmico. Análises química e metalográfica e ensaios de microdureza Vickers e tração, além de análise fratográfica por microscopia eletrônica de varredura (MEV) também foram realizados. A análise metalográfica revelou uma matriz ferrítica composta por grãos equiaxiais com carbonetos esferoidizados para o fio máquina, enquanto que o parafuso possui estrutura ferrítico-perlítica no núcleo e martensita revenida na camada cementada. Os ensaios de microdureza e de tração revelaram que o fio máquina e o parafuso possuem níveis de resistência mecânica dentro do esperado conforme as condições utilizadas, enquanto que não houve diferenças significativas entre os valores de torque de ruptura obtidos em ambas as situações analisadas. A etapa de decapagem ácida revelou que, nos grupos que não utilizaram inibidor, o número de falhas aumenta num primeiro momento com o aumento do tempo de decapagem, reduzindo após um determinado tempo de decapagem relacionado ao volume de ácido utilizado. O número de falhas sofre grande redução com a utilização do inibidor, porém mesmo a baixas concentrações de ferro, a utilização de maiores volumes de ácido associado a maiores tempos de decapagem aumentam o risco de fragilização. Apenas houve falha para a desidrogenação realizada a 1000C, por 1 hora, revelando a importância de adequados controles de temperatura, procedimentos de homogeneização e parâmetros de temperatura e tempo. Não houve falhas para o retrabalho revelando a importância de adequados procedimentos de retrabalho (tempo e solução) e de desidrogenação, enquanto que a análise da superfície de fratura revelou apenas os micromecanismos de fratura intergranular e dimples, sendo este último mais freqüentemente associado a regiões mais próximas ao núcleo, além da presença de trincas secundárias / Abstract: The main aim of this work is to investigate the effects on hydrogen embrittlement of bolts due to acid pickling, baking, and strip processes performed during zinc plating. Carburized bolts type "hexagon flange head tapping screws", with 6 mm of diameter and 16 mm of thread length were organized into 39 different groups. Acid pickling was evaluated using volumes of hydrochloric acid of 700 ml, 900 ml, and 1000 ml, presence, or absence, of acid inhibitor, and pickling periods of 15, 30, 45, and 60 minutes for each condition of acid volume and inhibitor used. Baking was evaluated using 1000C, and periods of 1, 2, and 3.5 hours for bolts that were subjected to acid pickling with a solution of 1000 ml of acid, absence of inhibitor, and pickling periods of 15, 30, 45, and 60 minutes. Strip was evaluated using bolts with zinc layer thickness of 8 ?m, stripped for 4 minutes in a solution of 700 ml of acid, absence of inhibitor, and 300 ml of water, performing the hypotheses of single and double strip without baking, and single strip followed by baking (1000C - 2 hours). Preloading tests for the detection of hydrogen embrittlement were conducted in bolts that were subjected to the preparations mentioned, while torsional tests were also conducted at these bolts, as well as in those obtained after heat treatment. Chemical and metallographic analysis, Vickers microhardness and tensile tests, and fractographic analysis using scanning electron microscopy (SEM) were also conducted. Metallographic analysis revealed a ferritic matrix composed of equiaxed grains with spheroidized carbides for the wire, while the bolts showed a ferritic-pearlitic microstructure at the center and tempered martensite at the hardened layer. Microhardness and tensile tests revealed that wire and bolts have strength levels as expected according to the conditions used, while no significant differences between the breaking torque values were obtained in both situations analyzed. Acid pickling revealed that in the groups, which did not use inhibitor, the number of failures increases at a first stage with increasing pickling periods, however it starts to decrease after a certain pickling period related to the volume of acid used. The number of failures is greatly reduced with the use of the inhibitor, but even at low concentrations of iron, the use of larger amounts of acid associated with longer pickling periods increases the risk of hydrogen embrittlement. Failures were observed only at 1000C - 1 hour as baking parameters, showing the importance of proper temperature controls, homogenization procedures, and temperature and time parameters. There were no failures related to strip, revealing the importance of adequate procedures for strip (period and solution used) and baking procedures as observed. The fracture surface analysis revealed only intergranular and dimples micromechanisms of fracture, where the latter being more often associated with regions closer to the core of the bolts, also showing the presence of secondary cracks / Mestrado / Materiais e Processos de Fabricação / Mestre em Engenharia Mecânica

During the production of steel, an oxide scale is formed on the surface and to achieve anadequate quality of the surface the scale needs to be removed. Acid pickling is a surfacetreatment where the oxide scale is removed by acid. Over time the amount of dissolved metals in the acid solution increases leading to a decrease in the pickling efficiency, hence the acid solution needs to be renewed. The renewing can be performed by an operation process called acid retardation. In this process, the spent pickling solution passes through a column packed with an ion exchange material, resin. The absorption of strong acids is preferred by the resin, hence the movement of the acids in the resin bed will be retarded relative to the movement of the metal ions. Regeneration of the resin occurs when water is passing through the resin bed counter current to the flow of the spent pickling solution. This generates a by-product with low acid and high metal content, and a product containing high acid and low metal. The aim of this thesis was to investigate the acid retardation with regards to separation efficiency and the behaviour of acid and metal in the column. The results can further be used as the groundwork for a deeper understanding of the acid retardation and how to optimize the process. Experiments were performed in lab-scale columns with synthetic spent pickling solutions containing sulfuric, nitric and hydrofluoric acid and iron in different mixtures. During the experimental work, variation of the acid and metal concentration, the type of resin and the height of the column were performed. The results from the experimental work show that a concentration dependence between the concentration of acid and metal exists and the performance of different resin types varies depending on the acid and metal solution tested. The height might also affect the separation, but it is recommended that this is further investigated. Other recommendations for further work with a focus on understanding the acid retardation for optimization include variations of the volume of solution added to the column, variation in flow rate and slurry packing of the resin.