Super ferritic stainless steels are used in equipment such as heat exchangers and distillation to... more Super ferritic stainless steels are used in equipment such as heat exchangers and distillation towers operating under extreme temperature and pressure conditions and in environments containing high concentrations of chlorides, H2S and CO2 found in the new areas of oil and gas exploration on the Brazilian coast. A super ferritic alloy with composition based on commercial steels was developed for the present study, aiming to adapt the composition of super ferritic steels in order to improve them. The developed alloy contains 4.4 wt.% of nickel (Ni) to improve toughness, 25.7wt.% of chromium (Cr) so that the stability of the ferritic phase is maintained due to the addition of Ni, 4.6wt.% of Mo to increase the corrosion resistance. The differential for the study of this alloy was the addition of 0.07wt.% (700 ppm) of boron, aiming to increase hardenability, toughness and grain boundary stabilization. Thermodynamic calculations were performed using the Thermo-Calc software for the simula...
The VIDAS Immuno-concentration Salmonella (ICS) plus selective plate method (Hektoen enteric, xyl... more The VIDAS Immuno-concentration Salmonella (ICS) plus selective plate method (Hektoen enteric, xylose lysine desoxycholate, bismuth sulfite) method for the detection of Salmonella was compared to the Bacteriological Analytical Manual (BAM)/AOAC culture method in a collaborative study. Thirty-two laboratories participated in the evaluation. Each laboratory tested one or more of the 6 test products: milk chocolate, nonfat dry milk, dried whole egg, soy flour, ground black pepper, and ground raw turkey. The 2 methods were in agreement for 1297 of the 1455 samples. Of the 158 samples not in agreement, 82 were VIDAS ICS plus selective plate-positive and BAM/AOAC-negative, and 76 were VIDAS ICS plus selective plate-negative and BAM/AOAC-positive.
Portable apparatus presented in this paper is an x-ray equipment permitting to carry out traditio... more Portable apparatus presented in this paper is an x-ray equipment permitting to carry out traditional stress determination by x-ray diffraction method both in-laboratory and in-field conditions. The portability of apparatus is achieved by construction of compact and light high voltage source coupled with special x-ray tube and using of coordinate sensitive detector. Other distinctive characteristic of apparatus is an absence of a goniometer. Special collimator and simple meter of incidence angle permit to substitute the goniometer and to carry out the stress measurements of different industrial equipments such as pipelines, tanks. Software program executes a control of measurement procedure and carries out data processing experimental results.
Displacive transformations involve the disciplined motion of atoms. As a result, there are clearl... more Displacive transformations involve the disciplined motion of atoms. As a result, there are clearly defined relationships between all aspects of the parent and product lattices. The theory for this is well established but has not been exploited in the calculation of transformation textures. This paper is a critical assessment of the methods for the estimation of crystallographic textures during the displacive transformation of austenite into martensite, bainite or Widmanstätten ferrite in steels. The discussion is limited to the case where austenite is not in a plastically deformed state prior to its transformation.
Aços Cr-Mo são usados na indústria do petróleo em aplicações com óleos crus ricos em compostos su... more Aços Cr-Mo são usados na indústria do petróleo em aplicações com óleos crus ricos em compostos sulfurosos. Aços comerciais como 2.5Cr1Mo ou 9Cr1Mo têm se mostrado ineficientes em consequência de altos índices de corrosão naftênica. Uma estratégia para resolver este problema é o aumento do teor de molibdênio destes aços. Neste trabalho foi estudado o efeito do aumento do teor de molibdênio na microestrutura de ligas Fe-9Cr-xMo, solubilizadas e soldadas. Foram levantados os diagramas de fases com auxílio de um programa comercial para verificar as possíveis fases a serem formadas e identificar os problemas de soldagem. A microestrutura das ligas solubilizadas foi analisada por microscopia óptica e EBSD, além da medição da dureza. Foram realizadas soldagens autógenas para verificar o efeito do aporte térmico na microestrutura e na dureza das ligas. O aumento do teor de molibdênio resultou no aumento da dureza das ligas. A análise microestrutural das ligas soldadas apresentou uma particu...
Aging heat treatments in maraging steels are fundamental to achieve the excellent mechanical prop... more Aging heat treatments in maraging steels are fundamental to achieve the excellent mechanical properties required in several industries, i.e., nuclear, automotive, etc. In this research, samples of maraging 300 alloy were aged using a novel procedure that combines different steps with two atmospheres (nitrogen and water vapor) for several hours. The oxidized surface layer was chemical, microstructural and micromechanically characterized. Due to the thermodynamic and kinetic conditions, these gases reacted and change the surface chemistry of this steel producing a thin iron-based oxide layer of a homogeneous thickness of around 500 nm. Within the aforementioned information, porosity and other microstructural defects showed a non-homogeneous oxide, mainly constituted by magnetite, nickel ferrite, cobalt ferrite, and a small amount of hematite in the more external parts of the oxide layer. In this sense, from a chemical point of view, the heat treatment under specific atmosphere allows ...
Este trabalho tem como objetivo avaliar o efeito da variacao da corrente durante a soldagem de tr... more Este trabalho tem como objetivo avaliar o efeito da variacao da corrente durante a soldagem de tres diferentes ligas de aco Fe-Cr-Mo, empregando o processo TIG sem adicao de material, e identificar quais mudancas podem ocorrer na microestrutura dessas ligas quando submetidas a dois diferentes parâmetros de soldagem aqui estudados. Amostras das ligas foram utilizadas na condicao solubilizada para a realizacao da soldagem na posicao plana, com eletrodo toriado, corrente continua eletrodo negativo, em dois diferentes niveis de energia, variando os valores de corrente. Apos a soldagem as ligas foram submetidas a caracterizacao microestrutural atraves de microscopia otica e medicao de dureza Vickers para determinar qual das ligas apresentou maior dureza de acordo com os parâmetros estabelecidos. A analise das microestruturas revelou que uma das ligas apresentou a formacao de martensita. A energia de soldagem com menor corrente gerou uma zona fundida com menor area para as tres ligas. Con...
Journal of Materials Engineering and Performance, 2020
Cold-drawn pearlitic steel strips exhibit a great combination of strength and ductility and are w... more Cold-drawn pearlitic steel strips exhibit a great combination of strength and ductility and are widely used in many engineering applications. Some of these applications require further mechanical conformation for the final use. An analysis of the microstructure and the change in crystallographic texture when strips are subjected to torsion processes necessary for some applications was made in the current study. It was shown that the formation of the wavy pearlite morphology associated with the <110> fiber texture parallel to the drawing axis could improve fatigue damage. Extreme dislocation densities and crystallographic defects induced by torsion enhanced the formation of ultrafine ferritic grains accompanied by partial cementite decomposition. The relationship between ferrite and cementite interfaces successfully simulated using the Shackleton model.
Super ferritic stainless steels are used in equipment such as heat exchangers and distillation to... more Super ferritic stainless steels are used in equipment such as heat exchangers and distillation towers operating under extreme temperature and pressure conditions and in environments containing high concentrations of chlorides, H2S and CO2 found in the new areas of oil and gas exploration on the Brazilian coast. A super ferritic alloy with composition based on commercial steels was developed for the present study, aiming to adapt the composition of super ferritic steels in order to improve them. The developed alloy contains 4.4 wt.% of nickel (Ni) to improve toughness, 25.7wt.% of chromium (Cr) so that the stability of the ferritic phase is maintained due to the addition of Ni, 4.6wt.% of Mo to increase the corrosion resistance. The differential for the study of this alloy was the addition of 0.07wt.% (700 ppm) of boron, aiming to increase hardenability, toughness and grain boundary stabilization. Thermodynamic calculations were performed using the Thermo-Calc software for the simula...
The VIDAS Immuno-concentration Salmonella (ICS) plus selective plate method (Hektoen enteric, xyl... more The VIDAS Immuno-concentration Salmonella (ICS) plus selective plate method (Hektoen enteric, xylose lysine desoxycholate, bismuth sulfite) method for the detection of Salmonella was compared to the Bacteriological Analytical Manual (BAM)/AOAC culture method in a collaborative study. Thirty-two laboratories participated in the evaluation. Each laboratory tested one or more of the 6 test products: milk chocolate, nonfat dry milk, dried whole egg, soy flour, ground black pepper, and ground raw turkey. The 2 methods were in agreement for 1297 of the 1455 samples. Of the 158 samples not in agreement, 82 were VIDAS ICS plus selective plate-positive and BAM/AOAC-negative, and 76 were VIDAS ICS plus selective plate-negative and BAM/AOAC-positive.
Portable apparatus presented in this paper is an x-ray equipment permitting to carry out traditio... more Portable apparatus presented in this paper is an x-ray equipment permitting to carry out traditional stress determination by x-ray diffraction method both in-laboratory and in-field conditions. The portability of apparatus is achieved by construction of compact and light high voltage source coupled with special x-ray tube and using of coordinate sensitive detector. Other distinctive characteristic of apparatus is an absence of a goniometer. Special collimator and simple meter of incidence angle permit to substitute the goniometer and to carry out the stress measurements of different industrial equipments such as pipelines, tanks. Software program executes a control of measurement procedure and carries out data processing experimental results.
Displacive transformations involve the disciplined motion of atoms. As a result, there are clearl... more Displacive transformations involve the disciplined motion of atoms. As a result, there are clearly defined relationships between all aspects of the parent and product lattices. The theory for this is well established but has not been exploited in the calculation of transformation textures. This paper is a critical assessment of the methods for the estimation of crystallographic textures during the displacive transformation of austenite into martensite, bainite or Widmanstätten ferrite in steels. The discussion is limited to the case where austenite is not in a plastically deformed state prior to its transformation.
Aços Cr-Mo são usados na indústria do petróleo em aplicações com óleos crus ricos em compostos su... more Aços Cr-Mo são usados na indústria do petróleo em aplicações com óleos crus ricos em compostos sulfurosos. Aços comerciais como 2.5Cr1Mo ou 9Cr1Mo têm se mostrado ineficientes em consequência de altos índices de corrosão naftênica. Uma estratégia para resolver este problema é o aumento do teor de molibdênio destes aços. Neste trabalho foi estudado o efeito do aumento do teor de molibdênio na microestrutura de ligas Fe-9Cr-xMo, solubilizadas e soldadas. Foram levantados os diagramas de fases com auxílio de um programa comercial para verificar as possíveis fases a serem formadas e identificar os problemas de soldagem. A microestrutura das ligas solubilizadas foi analisada por microscopia óptica e EBSD, além da medição da dureza. Foram realizadas soldagens autógenas para verificar o efeito do aporte térmico na microestrutura e na dureza das ligas. O aumento do teor de molibdênio resultou no aumento da dureza das ligas. A análise microestrutural das ligas soldadas apresentou uma particu...
Aging heat treatments in maraging steels are fundamental to achieve the excellent mechanical prop... more Aging heat treatments in maraging steels are fundamental to achieve the excellent mechanical properties required in several industries, i.e., nuclear, automotive, etc. In this research, samples of maraging 300 alloy were aged using a novel procedure that combines different steps with two atmospheres (nitrogen and water vapor) for several hours. The oxidized surface layer was chemical, microstructural and micromechanically characterized. Due to the thermodynamic and kinetic conditions, these gases reacted and change the surface chemistry of this steel producing a thin iron-based oxide layer of a homogeneous thickness of around 500 nm. Within the aforementioned information, porosity and other microstructural defects showed a non-homogeneous oxide, mainly constituted by magnetite, nickel ferrite, cobalt ferrite, and a small amount of hematite in the more external parts of the oxide layer. In this sense, from a chemical point of view, the heat treatment under specific atmosphere allows ...
Este trabalho tem como objetivo avaliar o efeito da variacao da corrente durante a soldagem de tr... more Este trabalho tem como objetivo avaliar o efeito da variacao da corrente durante a soldagem de tres diferentes ligas de aco Fe-Cr-Mo, empregando o processo TIG sem adicao de material, e identificar quais mudancas podem ocorrer na microestrutura dessas ligas quando submetidas a dois diferentes parâmetros de soldagem aqui estudados. Amostras das ligas foram utilizadas na condicao solubilizada para a realizacao da soldagem na posicao plana, com eletrodo toriado, corrente continua eletrodo negativo, em dois diferentes niveis de energia, variando os valores de corrente. Apos a soldagem as ligas foram submetidas a caracterizacao microestrutural atraves de microscopia otica e medicao de dureza Vickers para determinar qual das ligas apresentou maior dureza de acordo com os parâmetros estabelecidos. A analise das microestruturas revelou que uma das ligas apresentou a formacao de martensita. A energia de soldagem com menor corrente gerou uma zona fundida com menor area para as tres ligas. Con...
Journal of Materials Engineering and Performance, 2020
Cold-drawn pearlitic steel strips exhibit a great combination of strength and ductility and are w... more Cold-drawn pearlitic steel strips exhibit a great combination of strength and ductility and are widely used in many engineering applications. Some of these applications require further mechanical conformation for the final use. An analysis of the microstructure and the change in crystallographic texture when strips are subjected to torsion processes necessary for some applications was made in the current study. It was shown that the formation of the wavy pearlite morphology associated with the <110> fiber texture parallel to the drawing axis could improve fatigue damage. Extreme dislocation densities and crystallographic defects induced by torsion enhanced the formation of ultrafine ferritic grains accompanied by partial cementite decomposition. The relationship between ferrite and cementite interfaces successfully simulated using the Shackleton model.
Uploads
Papers by Hamilton Ferreira Gomes de Abreu