Influencia del espesor y de las inoculaciones de aluminio sobre la autoalimentación, dureza y microestructura en piezas de latón 85Cu5Zn5Sn5Pb fundido y colado en moldes de arena en verde
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Date
2024-07
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Universidad Nacional de Trujillo
Abstract
Se estudió “influencia del espesor y de las inoculaciones de aluminio sobre la autoalimentación,
dureza y microestructura en piezas de latón 85Cu5Zn5Sn5Pb fundido y colado en moldes de
arena en verde”. Con diseño bifactorial, 13 niveles espesor (5; 7; 9; 11; 13; 15; 17; 19; 22; 25;
30; 35 y 40 mm), 5 niveles de aluminio inoculado (0; 1; 3; 5 y 7%), tres réplicas del experimento
y corridas experimentales aleatorizadas. Cada colada se hizo a 1140 °C, 48 horas después del
moldeo, la autoalimentación y rechupe se midieron en base a método de Arquímedes y
perdidas de peso. Se hicieron al menos 40 mediciones de dureza HB por probeta. Para la
autoalimentación y la intensidad de formar el rechupe el ANOVA de los datos indica gran influencia del
espesor, muy poca influencia de los porcentajes de aluminio inoculado y prácticamente no hay influencia
de la interacción de ambas variables. Para la dureza superficial HB, el ANOVA determinó lo contrario:
Gran influencia del aluminio inoculado, menor influencia del espesor y muy poca influencia de
la interacción de ambas variables sobre la dureza. La autoalimentación máxima (100%) se logra
para espesores máximos de 7 mm, disminuye hasta 4,02% -13,57% para los 25 mm y se hace
0% para 40 mm, independiente del aluminio inoculado, el déficit de volumen máximo estuvo
entre 2,3 y 2,6% en todos los casos. Los incrementos máximos de dureza debido al espesor para
aleaciones con 0; 1; 3; 5 y 7% Al inoculado, respecto a la dureza de partida, fueron: 50,06%;
15,54%; 24,41%; 22,62% y 26,61%, respectivamente. Los incrementos de dureza debido al
aluminio para cada espesor fue: 208,63%; 221,00%; 224,26%; 232,32%; 249,34%; 256,96%;
252,32%; 274,82%; 261,50%; 282,73; 259,06%; 243,98% y 265,78%. La interacción de las
variables de estudio tuvo poca influencia sobre incrementos de dureza. Sin inoculación de
aluminio las microestructuras muestran dendritas típicas de latón α con nódulos finos de Pb inter
dendríticos en medio de posible fase β´ bien distribuidos, dendritas finas a espesores pequeños
y gruesas para probetas espesores indica tamaño de grano coherente con las durezas medidas y
el zinc equivalente de 19,2% aprox. Las microestructuras para aleaciones con inoculaciones de
aluminio en varios porcentajes y post tratamiento térmico muestran granos y dendritas con
nódulos de Pb entre las fases α; β´; α +β´ y β´ + γ que aparecen según zinc equivalente
calculado y son coherentes con durezas medidas.
“Influence of thickness and aluminum inoculations on self-feeding, hardness and microstructure in 85Cu5Zn5Sn5Pb brass pieces cast and cast in green sand molds” was studied. With twofactor design, 13 levels of thickness (5; 7; 9; 11; 13; 15; 17; 19; 22; 25; 30; 35 and 40 mm), 5 levels of inoculated aluminum (0; 1; 3; 5 and 7%), three replicates of the experiment and randomized experimental runs. Each casting was made at 1140 °C, 48 hours after molding, self-feeding and shrinkage were measured based on the Archimedes method and weight losses. At least 40 HB hardness measurements were made per specimen. For self-feeding and the intensity of forming the suck, the ANOVA of the data indicates great influence of the thickness, very little influence of the percentages of inoculated aluminum and practically no influence of the interaction of both variables. For HB surface hardness, the ANOVA determined the opposite: Great influence of the inoculated aluminum, less influence of the thickness and very little influence of the interaction of both variables on the hardness. The maximum self-feeding (100%) is achieved for maximum thicknesses of 7 mm, it decreases to 4.02% -13.57% for 25 mm and becomes 0% for 40 mm, independent of the inoculated aluminum, the maximum volume deficit It was between 2.3 and 2.6% in all cases. The maximum hardness increases due to thickness for alloys with 0; 1; 3; 5 and 7% Al inoculated, with respect to the starting hardness, were: 50.06%; 15.54%; 24.41%; 22.62% and 26.61%, respectively. The increases in hardness due to aluminum for each thickness were: 208.63%; 221.00%; 224.26%; 232.32%; 249.34%; 256.96%; 252.32%; 274.82%; 261.50%; 282.73; 259.06%; 243.98% and 265.78%. The interaction of the study variables had little influence on increases in hardness. Without aluminum inoculation, the microstructures show typical α-brass dendrites with fine inter-dendritic Pb nodules in the middle of a possible β' phase, well distributed, fine dendrites at small thicknesses and thick dendrites for specimens. Thickness indicates grain size consistent with the measured hardnesses and the zinc equivalent of approximately 19.2%. The microstructures for alloys with aluminum inoculations in various percentages and post heat treatment show grains and dendrites with Pb nodules between the α phases; β´; α +β´ and β´ + γ that appear according to calculated zinc equivalent and are consistent with measured hardnesses.
“Influence of thickness and aluminum inoculations on self-feeding, hardness and microstructure in 85Cu5Zn5Sn5Pb brass pieces cast and cast in green sand molds” was studied. With twofactor design, 13 levels of thickness (5; 7; 9; 11; 13; 15; 17; 19; 22; 25; 30; 35 and 40 mm), 5 levels of inoculated aluminum (0; 1; 3; 5 and 7%), three replicates of the experiment and randomized experimental runs. Each casting was made at 1140 °C, 48 hours after molding, self-feeding and shrinkage were measured based on the Archimedes method and weight losses. At least 40 HB hardness measurements were made per specimen. For self-feeding and the intensity of forming the suck, the ANOVA of the data indicates great influence of the thickness, very little influence of the percentages of inoculated aluminum and practically no influence of the interaction of both variables. For HB surface hardness, the ANOVA determined the opposite: Great influence of the inoculated aluminum, less influence of the thickness and very little influence of the interaction of both variables on the hardness. The maximum self-feeding (100%) is achieved for maximum thicknesses of 7 mm, it decreases to 4.02% -13.57% for 25 mm and becomes 0% for 40 mm, independent of the inoculated aluminum, the maximum volume deficit It was between 2.3 and 2.6% in all cases. The maximum hardness increases due to thickness for alloys with 0; 1; 3; 5 and 7% Al inoculated, with respect to the starting hardness, were: 50.06%; 15.54%; 24.41%; 22.62% and 26.61%, respectively. The increases in hardness due to aluminum for each thickness were: 208.63%; 221.00%; 224.26%; 232.32%; 249.34%; 256.96%; 252.32%; 274.82%; 261.50%; 282.73; 259.06%; 243.98% and 265.78%. The interaction of the study variables had little influence on increases in hardness. Without aluminum inoculation, the microstructures show typical α-brass dendrites with fine inter-dendritic Pb nodules in the middle of a possible β' phase, well distributed, fine dendrites at small thicknesses and thick dendrites for specimens. Thickness indicates grain size consistent with the measured hardnesses and the zinc equivalent of approximately 19.2%. The microstructures for alloys with aluminum inoculations in various percentages and post heat treatment show grains and dendrites with Pb nodules between the α phases; β´; α +β´ and β´ + γ that appear according to calculated zinc equivalent and are consistent with measured hardnesses.
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TECHNOLOGY::Chemical engineering::Metallurgical process and manufacturing engineering::Metallurgical process engineering