<p>A problem with cold pilgered tubes for OCTG applications is that they can get anisotropic properties with regard to yield strength. One source of anisotropy is texture that is developed during the cold deformation. EBSD measurements have been made on several austenitic stainless steels with different deformations to see what influence the composition has on the texture formation. The same measurements were used to study the influence of grain size on texture formation. The conclusion was that the composition can have an impact on the texture and hence has potential to also affect the anisotropy. The differences in texture cannot be associated with a specific alloying element, but is rather a synergetic effect. It was also concluded that grain structure has no strong influence on texture formation. An evaluation of three different tool designs used for cold pilgering was made. The designs evaluated are referred to as design A, B and C. EBSD measurements showed large deviations in texture in the middle of the wall compared to close to the surface of pilgered OCTG. However, the measurements showed no large differences between the three designs and the texture could not be coupled to the anisotropy.</p>

A problem with cold pilgered tubes for OCTG applications is that they can get anisotropic properties with regard to yield strength. One source of anisotropy is texture that is developed during the cold deformation. EBSD measurements have been made on several austenitic stainless steels with different deformations to see what influence the composition has on the texture formation. The same measurements were used to study the influence of grain size on texture formation. The conclusion was that the composition can have an impact on the texture and hence has potential to also affect the anisotropy. The differences in texture cannot be associated with a specific alloying element, but is rather a synergetic effect. It was also concluded that grain structure has no strong influence on texture formation. An evaluation of three different tool designs used for cold pilgering was made. The designs evaluated are referred to as design A, B and C. EBSD measurements showed large deviations in texture in the middle of the wall compared to close to the surface of pilgered OCTG. However, the measurements showed no large differences between the three designs and the texture could not be coupled to the anisotropy.

Les propriétés généralement demandées aux armatures pour béton armé doivent répondre à des exigences particulières précisées dans des normes nationales, européennes et internationales. Actuellement, dans la pratique de la production de l'acier à béton, on tend à substituer différentes nuances d'armature par une armature unifiée ayant une valeur de limite d'élasticité minimale de 500 MPa. Le remplacement des ronds à béton de nuance 400MPa par cette armature conduit à une économie de métal de l'ordre de 10-20 % d'après les estimations de différents spécialistes.Il existe, généralement, plusieurs techniques de fabrication des armatures, dont la déformation à chaud suivie d'un refroidissement accéléré sous flux d'eau (traitement thermomécanique ou Thermomechanical Control Process - TMCP), ainsi que la déformation à froid (tréfilage â travers une filière conique et une filière à rouleaux, microlaminage...), qui se heurte cependant â l'impossibilité de satisfaire aux exigences des Normes vis-à-vis des propriétés de résistance (Re > 500MPa) et de plasticité.Le présent travail a pour but le développement d'un procédé combiné de production d'acier à béton profitant des aspects positifs de deux types de déformation à chaud ainsi qu'à froid, sous forme du traitement combiné mécano-thermomécanique (post déformations à froid après le TMCP). et d'étudier la possibilité de production d'aciers à béton de qualité 500 MPa (B(A)500), de petits diamètres, en couronne, répondant aux exigences des Normes modernes. L'objectif scientifique de ce travail est d'étudier les mécanismes microstructuraux qui se produisent lors de la déformation à froid de l'acier préalablement traité thermomécaniquement et leurs conséquences sur l'évolution des propriétés mécaniques.Plusieurs nuances d'acier bas carbone de différents diamètres ont été étudiées. De nombreuses techniques de caractérisation macroscopique et microscopique de la structure de l'acier ont été utilisées: traction monotone, essais de microdureté, microscopie optique, microscopie électronique â balayage (MEB) et en transmission (MET), diffraction des rayons X. spectrométrie mécanique..Les résultats des essais montrent qu'il est possible d'obtenir avec assurance l’armature de qualité B(A)500, possédant des propriétés mécaniques qui dépassent les exigences des nonnes, à l'aide d’une déformation par torsion avec un cisaillement maximal de 22%, pour des aciers à 0.15 -0.2 % C(en poids), faiblement alliés en Mn et Si et traités themomécaniquement. La déformation par torsion provoque une augmentation de dureté en surface mais aussi au cœur de l'armature. Cette augmentation de dureté à cœur peut être amplifiée par le traitement thermique de vieillissement à 100°C correspondant à l'utilisation en Génie Civil. Cet effet, lié aux interactions dislocation-impuretés interstitielles, a été expliqué grâce â la MET et à l'étude du frottement intérieur. / Properties which are required from an armature for the reinforced concrete should satisfy the requirements of National, European and International standards. At the present time, in practice of armature production, there is a tendency of replacement of various classes of reinforcing steels by the unified armature with the minimum value of yield strength of 500 MPa. Replacement of the armature of the 400 MPa class by such reinforcing steel brings the economy of metal of an order of 10-20 % according to the estimations of various experts.In general, a set of production technologies of the armature exists, including hot deformation with the subsequent accelerated cooling in water - Thermomechanical Control Process (TMCP), and also cold deformation (drawing in conic die block, drawing in roller die block, microrolling) which nevertheless face the impossibility to provide the required strength (yield strength > 500MPa) and plastic properties.The technological purpose of the given work is:- development of the combined mechano-thermomechanical processing of armature's production which would combine positive aspects of hot and cold deformations (post deformation processing after TMCP);- examination of possibilty to manufacture the reinforcing steel of the class of 500MPa (B(A)500) of the small diameter, in coils, meeting the requirements of modem standards.The scientific objective of the work is the analysis of change of the microstructure of reinforcing steels after the cold deformation which is preliminary subjected to thermomechanical processing, and, also, the examination of the influence of microstructural effect on change of mechanical properties of steels.In the present study, a significant quantity of grades of low-carbon steels of various diameters has been investigated. Also, different techniques for macroscopical and microscopical characterization of the steel structures have been applied: tensile tests, micro-hardness test, optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray analysis and mechanical spectroscopy.Results of tests show that it is possible to obtain, with assurance, the reinforcing steel of the strength class B(A)500, with a complex of the mechanical properties surpassing the requirements of standards. For this purpose it is proposed to use the deformation by cold torsion with the maximum relative shear of 22 %, after thermomechanical processing, for steels with carbon content of 0,15...0,25% and alloyed with Mn and Si. Deformation by torsion provides an increase of hardness not only on the surface, but also in the core of armature. The effect of hardness increase can be strengthened by means of thermal ageing at 100°C corresponding to the use in Civil Engineering. This effect, related to the dislocations- interstitial impurities interactions, was explained thanks to MET and internal friction effect.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Titanium alloys are used for several applications of greater responsibility, for example in the biomedical, aeronautical, energy, security, among others sectors. Several studies have shown that TiNbSn alloys have advantages compared to other titanium alloys with respect to mechanical properties. Studies indicate a possibility of obtaining a tensile strength value as high as that of alloys traditionally used as Ti6Al4V, through cold deformation and aging. In addition, cold deformed TiNbSn alloys may have modulus of elasticity less than half the modulus presented by traditional alloys. These indications point to the possibility of intensifying the production and commercialization of TiNbSn alloys for the manufacture of highly responsible components. Therefore, for these applications, studies on the crack propagation behavior are important and even mandatory in certain circumstances, for example for the manufacture of components that may suffer catastrophic failures. The purpose of this study was to evaluate the fatigue crack propagation behavior of TiNbSn alloys system cold deformed and aged. In this study, the cold-rolled Ti35Nb2Sn, Ti42Nb2Sn and Ti42Nb alloys were produced with 80% true deformation and aged at 400 ° C for 48 hours. da/dN x ΔK tests were carried out and it was observed that the Ti422 and Ti420 alloys, both aged, had the best results of crack propagation resistance in the Paris regime and in the crack propagation threshold. That is, the increase of Niobium and the aging treatment produces alloy of greater crack propagation resistance. These results were attributed to the great cracks tortuosity. This tortuosity leads to a greater roughness induced crack closure effect. The threshold values increased with the aging process due to the increase in the modulus of elasticity values. / Ligas de titânio são utilizadas para várias aplicações de maior responsabilidade, como por exemplo, nos setores biomédico, aeronáutico, energia, segurança, entre outros. Diversos estudos vem demonstrando que as ligas TiNbSn apresentam vantagens se comparadas a outras ligas de titânio com respeito a propriedades mecânicas. Estudos indicam a possibilidade de obter valor de resistência a tração tão elevado quanto de ligas tradicionalmente usadas como Ti6Al4V, através de deformação a frio e envelhecimento. Além disso, as ligas TiNbSn deformadas a frio podem apresentar módulo de elasticidade inferior a metade do módulo apresentado por ligas tradicionais. Esses indícios apontam para a possibilidade de intensificar a produção e comercialização de ligas TiNbSn para a fabricação de componentes de alta responsabilidade. Portanto, para essas aplicações, estudos sobre o comportamento de propagação de trincas são importantes e até mandatórios em certas circunstâncias, como por exemplo para a fabricação de componenetes que possam sofrer falhas catastróficas. O objetivo do presente estudo foi avaliar o comportamento de propagação de trincas por fadiga das ligas do sistema TiNbSn deformadas a frio e envelhecidas. Neste estudo, foram produzidas as ligas Ti35Nb2Sn, Ti42Nb2Sn e Ti42Nb laminadas a frio com 80% de deformação verdadeira e envelhecidas a 400 °C por 48 horas. Ensaios da/dN x ΔK foram realizados e foi visto que as ligas Ti422 e Ti420, ambas envelhecidas, apresentaram os melhores resultados de resistência à propagação de trincas no regime de Paris e no limiar de propogação de trinca. Ou seja, o aumento de Nióbio e o tratamento de envelhecimento produzem liga de maior resitência a propagação de trinca. Esses resultados foram atribuídos à grande tortuosidade das trincas. Essa tortuosidade leva a um maior efeito de fechamento de trinca induzido pela rugosidade da fratura. Os valores de limiar aumentaram com o processo de envelhecimento devido ao aumento dos valores de módulo de elasticidade.