Análisis de falla de una válvula de escape del motor de un remolcador de la empresa COLTUG S.A.S
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Fecha
2022
Autores
Hernández Estrada, Sebastián
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Ediciones Universidad Simón Bolívar
Facultad de Ingenierías
Facultad de Ingenierías
Resumen
Las válvulas de motor son elementos esenciales para el funcionamiento de uno de estos, estas permiten la entrada y salida de los gases que entran al cilindro. Estas válvulas durante su funcionamiento están expuestas a extremas condiciones de trabajo, sobre todo las válvulas de escape, que deben soportar las altas temperaturas que transmite el gas quemado lo que puede provocar fallas térmicas y mecánicas al existir una incorrecta elección de material. En este artículo se realizó un análisis de falla de una válvula de escape de un motor de remolcador de la empresa COLTUG, el cual presento fracturas en la zona de unión del vástago con la cabeza. Para darle solución a la empresa se añadió al análisis otra válvula de escape que no se fracturo, pero si se jorobo mostrando indicios a fracturarse, esta válvula sirvió como guía para encontrar el mecanismo de la falla, de tal manera que se hicieron análisis fractográfico, químico, microestructural y de dureza, con el objetivo de comparar el material con otros aceros más usados en válvulas de motor. Se encontró que el acero presentaba una mala elección del material debido a bajas propiedades mecánicas y químicas en su estructura como por ejemplo la falta de molibdeno e inclusiones no metálicas que contribuyen al crecimiento de grano indeseado generando concentradores de tensiones facilitando las fallas por fatigas e inicios de grieta. Finalmente se propuso la elección de un nuevo acero más económico y adaptado para la aplicación además de cambiar el diseño de válvula bimetálica a monometálicas.
Engine valves are essential elements for the operation of an engine, they allow the entry and exit of gases entering the cylinder. During their operation, these valves are exposed to extreme working conditions, especially the exhaust valves, which must withstand the high temperatures transmitted by the burnt gas, which can cause thermal and mechanical failures due to an incorrect choice of material. In this article, a failure analysis of an exhaust valve of a tugboat engine of COLTUG company was carried out, which presented fractures in the union area of the stem with the head. In order to provide a solution to the company, another exhaust valve was added to the analysis, which was not fractured, but was humped showing signs of fracture. This valve served as a guide to find the failure mechanism, so that fractographic, chemical, microstructural and hardness analyses were carried out, with the purpose of comparing the material with other steels more commonly used in engine valves. It was found that the steel presented a poor choice of material due to low mechanical and chemical properties in its structure, such as lack of molybdenum and non-metallic inclusions that contribute to undesired grain growth, generating stress concentrators, facilitating fatigue failures and crack initiation. Finally, it was proposed to choose a new steel, more economical and adapted to the application, as well as to change the bimetallic valve design to monometallic.
Engine valves are essential elements for the operation of an engine, they allow the entry and exit of gases entering the cylinder. During their operation, these valves are exposed to extreme working conditions, especially the exhaust valves, which must withstand the high temperatures transmitted by the burnt gas, which can cause thermal and mechanical failures due to an incorrect choice of material. In this article, a failure analysis of an exhaust valve of a tugboat engine of COLTUG company was carried out, which presented fractures in the union area of the stem with the head. In order to provide a solution to the company, another exhaust valve was added to the analysis, which was not fractured, but was humped showing signs of fracture. This valve served as a guide to find the failure mechanism, so that fractographic, chemical, microstructural and hardness analyses were carried out, with the purpose of comparing the material with other steels more commonly used in engine valves. It was found that the steel presented a poor choice of material due to low mechanical and chemical properties in its structure, such as lack of molybdenum and non-metallic inclusions that contribute to undesired grain growth, generating stress concentrators, facilitating fatigue failures and crack initiation. Finally, it was proposed to choose a new steel, more economical and adapted to the application, as well as to change the bimetallic valve design to monometallic.
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Palabras clave
Válvula, Fractura, Fatiga, Propiedades mecánicas, Crecimiento de grano, Valve, Fracture, Fatigue, Mechanical properties, Grain growth
