En este trabajo de tesis se analiza la soldabilidad de aceros de alta resistencia y baja aleación utilizados en la construcción de cañerías para el transporte de hidrocarburos mediante procesos de soldadura por arco eléctrico. El objetivo fue determinar la influencia de los parámetros de soldadura en la aparición y posterior eliminación de constituyentes Martensita - Austenita que forman parte de regiones de la zona afectada por calor (ZAC) de la soldadura, denominada zonas frágiles locales. Para ello se aplicaron métodos de caracterización metalográfica para su observación por microscopia óptica y se implementaron técnicas de análisis posterior a los ensayos mecánicos para garantizar la evaluación de la ZAC. Se analizaron los parámetros de soldadura encontrandose que la temperatura de precalentamiento tiene una fuerte influencia en los cambios microestructurales de la ZAC y que las temperaturas de precalentamiento recomendadas por los códigos de diseño y fabricación de componentes soldados no resultaron suficiente para la disolución de los constituyentes M-A una vez formados. La presencia de regiones segregadas en el metal base favorecen la formación de los mismos. Esto fue corroborado con aceros más modernos en los que se encontró menor nivel de segregación y modificación en las técnicas de fabricación que evitan la formación de los constituyentes M-A.. Se evaluó además la soldadura con fluidos circulando con el fin de establecer si en la misma se generaban estos constituyentes. A través de la medición de la temperatura en la pared interna de la cañería se encontró que en los aceros en servicio el riesgo de falla más esperado es por fisuración en frío, mientras que en los aceros más nuevos el riesgo mayor es la perforación durante la soldadura de reparación. En función de los resultados se determinó un método analítico que permite obtener la dureza en la ZAC para este tipo de soldadura, una vez establecido el tiempo de enfriamiento en la misma. / In this thesis work, the weldability of high strength and low alloy steels used in the construction of pipes for the hydrocarbon transport by means of electric arc welding processes is analyzed. The objective was to determine the influence of welding parameters in the appearance and later elimination of components Martensite - Austenite that comprise regions of the heat affected zone (HAZ) of the weld denominated local brittle zones. For that, metallographic characterization methods for their observation by optical microscopy were obtained and techniques of analysis were implemented subsequent to mechanical tests to guarantee the HAZ evaluation. Welding parameters were analyzed and it was found that the pre heating temperature has a great influence on the HAZ micro structural changes and the temperatures recommended by design and construction codes for welded components were not enough to achieve dissolution of M-A constituents once they were formed. The presence of segregated regions in the base metal helps to their formation. This was corroborated in more modern steels in which was found a lower level of segregation and a modification in the fabrication techniques that avoid the formation of M-A constituents. It was also evaluated the welding with a fluid flowing in order to investigate whether these constituents were generated. By means of measuring the temperature on the internal wall of the pipe, it was found that, in steels already in service the risk of failure most expected is by cold cracking, whereas in newer steels the greater risk is to be perforated during the repair welding. Based on the results, a new analytical method was established which allows to obtain the hardness in the HAZ for this type of welds once the cooling time is given.

Cette thèse porte sur l'analyse des pratiques participatives des deux projets, la ZAC Paris Rive Gauche à Paris, l'aménagement du Gwanghwamun Square à Séoul. Alors que la « participation » dans le projet urbain est souvent annoncée comme l'objectif idéal, ce terme laisse une marge de traduction à chaque personne qui l'utilise. Cette thèse a pour objectif de comprendre le rôle de participation dans la fabrication de l'espace. Nous entamons d'abord l'étude du déroulement de ces deux projets urbains et de ses acteurs pour montrer leur place dans la démarche du projet. Ensuite, nous analysons la structure des dispositifs participatifs et leur fonctionnement. Il s'agit d'étudier la place des citoyens dans le projet urbain qui apparaissent à travers ces dispositifs et le lien qu'ils nouent éventuellement avec les acteurs. Qui sont-ils ? Pour répondre à cette question, nous analysons les figures des citoyens qui émergent lors de la participation. Nous avons retenu trois critères : 1) l'intensité de la participation, 2) l'intérêt qu'ils portent au projet et à l'espace, 3) la reconnaissance des savoirs citoyens. À partir de cette analyse sur la figure des citoyens, nous étudions comment des citoyens peuvent revendiquer leur présence dans la démarche du projet, et être reconnus par les acteurs ou non. Ce processus implique la mise en cause de la légitimité du projet et de l'autorité déléguée des acteurs. Si les acteurs du projet résistent à la réduction de leur portée dans la démarche du projet, qu'apporte la présence des citoyens dans l'aménagement de l'espace et à l'action publique collective ? Notre recherche montre que la dynamique participative n'est pas totalement malléable, malgré les difficultés de la prise de place des citoyens dans le jeu d'acteurs et de la reconnaissance de celle-ci. Nous avons essayé d'identifier les conditions de participation comme la possibilité de modifier la configuration des échanges, le partage des savoirs et la formation pour la participation / This thesis focuses on the analysis of participatory practices of two urban projects - the ZAC Paris Rive gauche in Paris and the creation of Gwanghwamun Square in Seoul. “Participation” in the urban project is often announced as the ideal objective. Its signification is disputable. The object of this thesis is to understand the role of participation in the making of spaces. For this, we start by describing the progress of these two urban projects as well as their stakeholders, to clarify their position in the project process. Then, the structure of the participating organizations and their functions are analyzed. By doing so, the place of citizens in the urban project as it appears in their relations with these organizations and their relations themselves with the stakeholders will be examined. Who are they? We analyze the types of citizens who emerge through citizen participation. Three criteria are selected: 1) the intensity of participation, 2) participants' interests, 3) recognition of citizens' knowledge. From these criteria, we research how citizens can claim their presence in the project, and be recognized by the stakeholders or not. If the stakeholders of the project resist the weakening of their influence in the project process caused by participation, what can the presence of these citizens bring to the space and to the public collective action? Our research shows that the dynamics of participation are not totally malleable, in spite of the citizens' difficulties in taking their place among stakeholders, and the recognition of their place. This research identifies the conditions of participation as the possibility of modifying the discussion situation, the knowledge sharing, and the learning to participate

Notre recherche s'inscrit dans le cadre de la problématique générale du développement et de la ville durable. En partant de l’analyse de notre environnement construit et notamment des réponses architecturales et urbaines à apporter en vue de diminuer de façon significative les émissions des gaz CO2, limiter l'effet de serre et préserver la biodiversité, nous nous sommes attachés à l'étude d'un écoquartier situé dans une ville emblématique du point de vue écologique, celle de Grenoble, et dans l'un de ses espaces urbains : la caserne de Bonne. Nous sommes partis de l'hypothèse que c'est tout d’abord au plan local, puis régional et national que l’on devra élaborer et mettre en pratique des solutions adaptées pour lutter contre toutes les formes de pollution, créer et innover en matière d'énergie renouvelable, tout en diminuant de façon progressive l'usage des énergies fossiles. C'est en tant qu'architecte urbaniste praticien que nous avons voulu apporter notre contribution dans ce domaine, en optant pour une analyse approfondie de l’écoquartier de l'ancienne caserne de Bonne à Grenoble. / Our research addresses the general issue of urban development and how to design sustainable cities through architecture and town planning. Our analysis focused on a study of caserne de Bonne, an ecodistrict located in Grenoble, which is an emblematic city from an ecological viewpoint. Our task was to significantly reduce CO2 gas emissions, limit the greenhouse effect, and preserve biodiversity. We developed our hypothesis to devise satisfactory solutions to fight pollution, reduce the use of fossil fuels, and create innovative ways to employ renewable energy. Our program will start locally, then expand on a regional and national level. We observed that in residential districts, remedies such as reducing transportation generated pollution, conserving energy, treating household waste, and other parameters,can be scaled up and implemented regionally and nationally. As architect and urban planner, we wanted to contribute to this field by providing an analysis of Bonne ecodistrict.

In this study, I analyze Zac O´Yeah´s novel Tandooriälgen (2006) and discuss how it relates to postcolonial theory and terms like otherness and mimicry. The novel takes place in a not so distant future, where Sweden and Europe have joined the Asian Union which is governed by India. Herrman Barsk, a detective in his hometown of Gothenburg (now called Gautanpuri) has to solve a crime involving four murdered victims that have been grilled in a tandoori oven. The case leads Barsk to the criminal underworld of Gautanpuri, where asocial natives roam the streets and religious extremists plan to liberate the city by use of terrorism. Basing my analysis on postcolonial theorists like Homi K. Bhabha and Frantz Fanon, I examine Barsks role as a colonial subject to identify a critical intention in the novel.

O trabalho é uma análise comparada de cinco mecanismos de política urbana praticados em quatro países diferentes: EUA, França, Colômbia e Brasil. Esses mecanismos têm como característica principal o financiamento de melhorias na infraestrutura urbana, com recursos gerados por parte da valorização imobiliária, e apropriados por meio desses mecanismos. São eles: Transfer of Development Rights (TDR) nos EUA, Leyes de la Plusvalia na Colômbia, Zones d´Aménagement Concertée (ZAC) na França, CEPACs e Outorga Onerosa em São Paulo, Brasil. O objetivo do trabalho é identificar princípios e regras comuns entre eles, e analisar suas diferenças mais significativas, e as razões para isso. Os mecanismos são apresentados individualmente e, em seguida, comparados quanto a suas características principais: histórico e objetivos de sua implantação, estrutura legal, método de formação do preço ou valor a ser pago, momento do pagamento e eficácia na geração de benefícios urbanísticos. / This work is a comparative analysis of five different mechanisms or urban policy as they are practiced in four different countries: the USA, France, Colombia and Brazil. The main characteristic these mechanisms have in common is the financing of improvements in the urban infrastructure with resources generated by the increase in value or real estate, and the corresponding capture part of that increase in value. The mechanisms analyzed are: Transfer of Development Rights (TDR) in the USA, Leyes de la Plusvalia, in Colombia, Zones d\'Aménagement Concertée (ZAC) in France, Certificados de Potencial Adicional de Construção (CEPACs) and Outorga Onerosa do Direito de Construir, São Paulo, Brazil. The objective of this work is to identify the principles and rules that they share, analyze the most relevant differences and the reasons for those differences. Each of the mechanisms is presented individually, followed by a comparison of their main characteristics: its objective and history, legal structure, price or value formation, moment of payment, and its effectiveness in generating urban improvement.

O trabalho é uma análise comparada de cinco mecanismos de política urbana praticados em quatro países diferentes: EUA, França, Colômbia e Brasil. Esses mecanismos têm como característica principal o financiamento de melhorias na infraestrutura urbana, com recursos gerados por parte da valorização imobiliária, e apropriados por meio desses mecanismos. São eles: Transfer of Development Rights (TDR) nos EUA, Leyes de la Plusvalia na Colômbia, Zones d´Aménagement Concertée (ZAC) na França, CEPACs e Outorga Onerosa em São Paulo, Brasil. O objetivo do trabalho é identificar princípios e regras comuns entre eles, e analisar suas diferenças mais significativas, e as razões para isso. Os mecanismos são apresentados individualmente e, em seguida, comparados quanto a suas características principais: histórico e objetivos de sua implantação, estrutura legal, método de formação do preço ou valor a ser pago, momento do pagamento e eficácia na geração de benefícios urbanísticos. / This work is a comparative analysis of five different mechanisms or urban policy as they are practiced in four different countries: the USA, France, Colombia and Brazil. The main characteristic these mechanisms have in common is the financing of improvements in the urban infrastructure with resources generated by the increase in value or real estate, and the corresponding capture part of that increase in value. The mechanisms analyzed are: Transfer of Development Rights (TDR) in the USA, Leyes de la Plusvalia, in Colombia, Zones d\'Aménagement Concertée (ZAC) in France, Certificados de Potencial Adicional de Construção (CEPACs) and Outorga Onerosa do Direito de Construir, São Paulo, Brazil. The objective of this work is to identify the principles and rules that they share, analyze the most relevant differences and the reasons for those differences. Each of the mechanisms is presented individually, followed by a comparison of their main characteristics: its objective and history, legal structure, price or value formation, moment of payment, and its effectiveness in generating urban improvement.

Neste trabalho foram estudadas as microestruturas, dureza, e resistência ao impacto em aço alta resistência e baixa liga (ARBL) na ZAC. O processo de soldagem foi por arco submerso, utilizando corrente de 600A, tensão de 25V, velocidade de soldagem de 25,5; 24; 20,94; e 19,5 cm/min. Utilizou-se chapa de aço USI-SAC-50. Os quatro aportes de calor produzidos 3,53; 3,75; 4,24; 4,61 kJ/mm, permitiram variações microestruturais na região de granulação grosseira da ZAC, promovendo variações nas medidas de durezas e nos resultados do ensaio de impacto medido à -25ºC e -10ºC. Quando realizado o tratamento térmico de alívio de tensões a 580ºC por 1 hora, as morfologias das microestruturas e medidas de dureza na região grosseira da ZAC, praticamente foram iguais, independente do aporte de calor. Os resultados do ensaio de impacto realizado à -25ºC, com e sem tratamento térmico, não sofreram alterações significativas para os valores das energias absorvidas na ZAC. Já a -10ºC a mudança foi mais significativa. O aspecto da morfologia da fratura na região de granulação grosseira da ZAC, após o ensaio de impacto, foi coerente para os quatro aportes de calor utilizados na soldagem. / It was studied in this report the microstructure, hardness and impact resistance in High Strength Low Alloyed (HSLA) steel in HAZ. The submerged are weld metals were made, using corrent of 600A, are voltage of 25V and travel speed of 25,5; 20,9; 24; and 19,5 cm/min. The USI-SAC-50 steel was used in present report. Four different heat input 3,53; 3,75; 4,24 and 4,61 kJ/mm were used to weld, produced significant changes in the coarse heat affected zone (HAZ) microstructure morphology, and this effect promoted changes on the hardness and the impact results at -25°C and -10°C. Using stress reliev treatment at 580°C for one hour, has changed the microstructure morphology in the coarse heat affected zone and the hardness measurements becames quite similar, therefore independent of the heat input. At -25°C the impact results has shown no variations with the stress reliev heat treatment. However, there were significant changes in the impact results at -10°C. After the impact test, the aspect of morphology facture in the coarse heat affected zone (HAZ), was coherent for the four different heat input, were used to weld.

Neste trabalho foram estudadas as microestruturas, dureza, e resistência ao impacto em aço alta resistência e baixa liga (ARBL) na ZAC. O processo de soldagem foi por arco submerso, utilizando corrente de 600A, tensão de 25V, velocidade de soldagem de 25,5; 24; 20,94; e 19,5 cm/min. Utilizou-se chapa de aço USI-SAC-50. Os quatro aportes de calor produzidos 3,53; 3,75; 4,24; 4,61 kJ/mm, permitiram variações microestruturais na região de granulação grosseira da ZAC, promovendo variações nas medidas de durezas e nos resultados do ensaio de impacto medido à -25ºC e -10ºC. Quando realizado o tratamento térmico de alívio de tensões a 580ºC por 1 hora, as morfologias das microestruturas e medidas de dureza na região grosseira da ZAC, praticamente foram iguais, independente do aporte de calor. Os resultados do ensaio de impacto realizado à -25ºC, com e sem tratamento térmico, não sofreram alterações significativas para os valores das energias absorvidas na ZAC. Já a -10ºC a mudança foi mais significativa. O aspecto da morfologia da fratura na região de granulação grosseira da ZAC, após o ensaio de impacto, foi coerente para os quatro aportes de calor utilizados na soldagem. / It was studied in this report the microstructure, hardness and impact resistance in High Strength Low Alloyed (HSLA) steel in HAZ. The submerged are weld metals were made, using corrent of 600A, are voltage of 25V and travel speed of 25,5; 20,9; 24; and 19,5 cm/min. The USI-SAC-50 steel was used in present report. Four different heat input 3,53; 3,75; 4,24 and 4,61 kJ/mm were used to weld, produced significant changes in the coarse heat affected zone (HAZ) microstructure morphology, and this effect promoted changes on the hardness and the impact results at -25°C and -10°C. Using stress reliev treatment at 580°C for one hour, has changed the microstructure morphology in the coarse heat affected zone and the hardness measurements becames quite similar, therefore independent of the heat input. At -25°C the impact results has shown no variations with the stress reliev heat treatment. However, there were significant changes in the impact results at -10°C. After the impact test, the aspect of morphology facture in the coarse heat affected zone (HAZ), was coherent for the four different heat input, were used to weld.

A tecnologia dos aços microligados para transporte de gás natural e petróleo tem sido pressionada pelo descobrimento das novas jazidas e o aumento da demanda no mundo. As solicitações ambientais e de resistência mecânica são os parâmetros para o desenvolvimento de aços de alta resistência baixa liga para o transporte de gás e petróleo a menor custo e de forma segura. Neste contexto esta pesquisa investiga, em um aço microligado para tubos API 5L X80, o efeito das transformações de fase obtidas por resfriamentos controlados na fratura induzida por hidrogênio Hydrogen Induced Cracking-(HIC) e nas propriedades mecânicas. Os testes de HIC foram realizados no material como recebido, na espessura da chapa submetida a resfriamentos contínuos e em amostras do material tratadas de forma a simular as regiões de grão grosso da zona afetada pelo calor (GGZAC). Segundo o ciclo de resfriamento, os aços microligados têm microestruturas complexas, como é caso do aço microligado em estudo, onde sua microestrutura, estudada em trabalhos anteriores, é formada principalmente por ferrita, bainita, perlita e microconstituinte austenita/martensita (AM). A morfologia, tamanho, quantidade e distribuição dos produtos de transformação na chapa mudam as propriedades do aço. Esses fenômenos são de grande interesse tecnológico em aços microligados para a fabricação de tubos soldados para o transporte de gás e petróleo, tanto quando a solda é realizada em campo como também durante o encurvamento por indução; aqui as propriedades mecânicas do tubo decorrentes do processo de fabricação termomecânico podem ser degradadas pela ação do aquecimento e dos resfriamentos experimentados na zona afetada pelo calor (ZAC), principalmente na região de GGZAC. A simulação dos ciclos térmicos para o estudo da HIC na espessura da chapa foram realizados em CP austenitizados a 900ºC e submetidos a resfriamentos contínuos no dilatômetro de têmpera. Para simular os ciclos térmicos com resfriamentos controlados focados na GGZAC e a seguir obter CP de tamanho adequado para testes de tração e Charpy, foi necessário fazer os tratamentos térmicos a 1300ºC e resfriamentos contínuos em um simulador termomecânico e dilatômetro Gleeble. O maior tamanho da amostra tratada termicamente neste último equipamento permitiu extrair amostras para avaliar as propriedades mecânicas e a HIC do material, pois as diferentes regiões da ZAC em uma solda real são restritas e não permitem este tipo de ensaios em uma região específica da ZAC. Os resultados permitiram identificar a suscetibilidade de cada microestrutura produto da transformação da austenita na espessura da chapa, sendo a região central da chapa a mais sensível ao hidrogênio no aço como recebido e quando tratado a baixas taxas de resfriamento de 0,5°C/s após austenitizado a 900°C. As bandas grosseiras formadas por estruturas de maior dureza que a matriz na região central diminuíram a resistência à HIC. Da mesma forma nos corpos de prova que simulam a região GGZAC, a fratura induzida pelo hidrogênio foi localizada na região central da espessura embora apresente bainita e ferrita acicular. A falha possivelmente se deve aos elementos remanescentes segregados nesta região central e partição de carbono para os sub contornos de grão da bainita e ferrita que cresceram a partir a austenita primária. As inclusões e precipitados, segundo seu tipo, forma e localização na microestrutura, participam ou não da nucleação e propagação da trinca, sendo a posição mais crítica quando localizadas dentro das estruturas bandeadas. Não foi observada a nucleação de trincas na presença de hidrogênio em precipitados de Nb e Ti. / The technology of microalloyed steels for the transportation of natural gas and oil has been pressed by the discovery of new deposits and the increased demand in the world. Environmental requests for safety and ever increasing mechanical strength are the parameters for the development of high strength low alloy steels for transporting gas and oil at lower cost and safely. In this context, this research investigates, in a microalloyed steel pipe API 5L X80, the effect of phase transformations obtained by controlled cooling on the behavior when loaded with hydrogen - Hydrogen Induced Cracking - (HIC) and in the mechanical properties. HIC tests were performed on as-received material, on samples extracted from the thickness of the plate and subjected to continuous cooling and on samples of the material treated to simulate the coarse-grained regions of heat affected zone (CGHAZ). According to the cooling cycle, the microalloyed steels have complex microstructures: in the steel under evaluation its microstructure, studied in a previous work, consists mainly of ferrite, bainite, pearlite and austenite/martensite constituent (AM). The morphology, size, quantity and distribution of the products of transformation change the properties of plate steel. These phenomena are of great technological interest in microalloyed steels for the fabrication of welded tubes for the transport of gas and oil, when the welding is performed in the field as well as during hot bending; here the mechanical properties of the tube from the process of thermomechanical fabrication can be degraded by the action of heating and cooling experienced in the heat affected zone (HAZ), mainly in the region of CGHAZ. Simulations of thermal cycles for the study of HIC on sheet thickness were performed in coupons subjected to austenitization at 900ºC followed by continuous cooling in the dilatometer. To simulate the thermal cycles with controlled cooling, focused in the CGHAZ, and getting suitable sample sizes for tensile testing and Charpy, it was necessary to austenitize at 1300ºC followed by continuous cooling using the thermal and thermomechanical simulator in a Gleeble dilatometer. Samples heat treated in this equipment were suitable to evaluate the mechanical properties and the HIC of the material for different regions of HAZ, while a real weld would not have enough material to allow this type of testing on a specific region of HAZ. The results showed the susceptibility of each microstructure product of austenite transformation and of the position on the plate thickness. The central region of the plate was more sensitive to hydrogen in the steel as-received and when treated at low cooling rates of 0.5°C/s after austenitization at 900°C. The bands formed by coarse structures of greater hardness than the matrix in the central region decreased the resistance to HIC. Likewise in coupons that simulate the CGHAZ region, the fracture induced by hydrogen was located in the central thickness line, even when the microstructure were bainite and acicular ferrite. Failure there was possibly due to remnants of segregated elements in this central region and carbon partition to the subboundaries of the bainite and ferrite grain that grew from the primary austenite. Inclusions and precipitates, according to their type, shape and location in the microstructure, participating or not in the nucleation and propagation of the crack, were more critical when located within the banded structures; crack nucleation in the presence of hydrogen was not observed at Nb and Ti precipitates.

Os aços inoxidáveis duplex (AIDs) são materiais com um excelente desempenho tanto mecânico como à corrosão. Inúmeras pesquisas tem sido desenvolvidas para aprimorar a soldabilidade destas ligas. Algumas transformações de fase, que são passíveis de ocorrer durante o processo de soldagem, podem prejudicar seriamente o desempenho das juntas. Foram simuladas microestruturas da região da zona afetada pelo calor submetida a temperaturas elevadas (ZACTE), utilizando um modelo proposto de fluxo de calor. Abordaram-se aspectos fundamentais da precipitação de austenita secundária, de nitreto de cromo e as suas interações na ZACTE de soldas multipasse. Finalmente, foram realizados testes de tenacidade e de resistência à corrosão para avaliar o efeito das transformações de fase estudadas no desempenho das juntas soldadas. Os tratamento térmicos e simulações da ZACTE foram realizadas num equipamento GleebleÒ. As microestruturas foram analisadas mediante microscopia ótica e eletrônica de varredura e de transmissão. Junto com a microscopia eletrônica foram realizadas microanálises químicas das fases estudadas. Baseando-se nos resultados obtidos, verificou-se que nem todos os AIDs são susceptíveis de ferritizar. Este fato tem uma grande influência no comportamento metalúrgico e na soldabilidade destes aços. Quanto aos aspectos fundamentais da metalurgia destes aços, observou-se uma estreita interação entre a precipitação da austenita secundária e os nitretos de cromo, chegando-se a propor um mecanismo de nucleação da austenita secundária intragranular a partir dos nitretos. Por último, foi constatado que o efeito deletério da austenita secundária intragranular na resistência à corrosão pode ser evitado mediante a adequada elaboração do procedimento de soldagem. / Duplex stainless steels (DSS) have excellent mechanical and corrosion properties. Many researches have been developed regarding the weldability of these alloys. There are some phase transformations that take place during the welding process, which may impair the welded joint behavior. High temperature heat-affected zone (HTHAZ) microstructures were simulated using a proposed heat flow model. Fundamental aspects of the secondary austenite and chromium nitride precipitation, and its interactions in the HTHAZ of multipass welds, were studied. In addition, toughness and corrosion tests were done to evaluate the influence of the studied phase transformations on the weld behavior. A GleebleÒ system was used to do the heat treatments and HTHAZ simulations. The microstructures were analyzed by means of optic and electron microscopy. Along with the electron microscopy it was done chemical microanalysis of the studied phases. Based on results, it was verified that not all DSSs can be ferritized. This fact has a strong influence on metallurgical behavior and weldability of these alloys. Regarding to the metallurgical fundamental aspects of these steels, it was observed a remarkable interaction between secondary austenite and chromium nitride precipitation. Thus, it was proposed a mechanism of intragranular secondary austenite precipitation from chromium nitrides. It was also verified, how the deleterious effect of intragranular secondary austenite in the corrosion resistance can be avoided by means of appropriate welding procedures.