Soldadura láser remota de aceros de alto límite elástico

En este artículo se presenta un estudio de soldabilidad del acero de alto límite elástico Usibor 1500 P revestido al Al-Si sin tratar térmicamente mediante soldadura láser remota. La soldadura de este material presenta dificultades debido a que el Al presente en el recubrimiento provoca inclusiones de compuestos íntermetálicos Al-Fe en la unión. Estos compuestos tienen baja ductilidad y fractura frágil a temperatura ambiente, produciendo estos efectos en la unión realizada.- This paper presents a weldability study of Usibor 1500 P high strength steel pre-coated of Al-Si in the non quenched state by remote laser welding. The pollution of the melt pool by Al-Fe intermetallic particles during laser welding results in low strength joints

Arc welding of Dissimilar Metals:FEA and Experiments

Assuming an elliptical disk heat source, several results of theoretical and experimental investigations on heat transfer in copper - low carbon steel welded joints are presented in the first part of the paper. Using thin sheets, temperature variation in the thickness direction is negligible and heat flow is considered two-dimensional. Convection and radiation influence, and thermo-physical properties depending on the temperature are considered in the model. Measurements and visualization of the temperatures distribution have been made during welding using infrared thermography. The proposed theoretical method using finite element analysis was validated for the temperatures prediction in the welded joint. In the second part of the paper, the influence of the welding process on the structural modifications and grains’ size in the heat affected zone (HAZ) of both base materials (BM) is described. Discussion on the graphs of temperatures variation vs. microstructural analysis enables conclusions on the potential undesired structural changes and related preventing measures. The asymmetric position of the heat source closer to the material having a higher thermal conductivity is an effective method for controlling the temperature field

New Approach on the Cold Welding of Metals: Application to Aluminium Bars

La soldadura por frío por presión es un proceso de fabricación de empalme en estado sólido con varios usos importantes, pero carente en sus fundamentales. Este papel presenta un nuevo acercamiento de la investigación en el campo, trayendo contribuciones originales teóricas y prácticas al conocimiento del principio de la soldadura en frío y creando las bases para el desarrollo de los nuevos procesos que tratan los materiales modernos. El acercamiento se basa en un FEM capaz para predecir el comportamiento material durante la deformación, considerando varias condiciones introducidos por el código usado: análisis estático no linear, tensión grande y desviación grande, dislocaciones prescritas. La correlación entre las tensiones y la deformación del material ha sido tratada luego. Las dimensiones y las características de la zona afectada mecánica - MAZ (desarrollado en el material debido al proceso de deformación) están también alcanzados.-Cold pressure welding is a solid state joining manufacturing process with several important applications, but with gaps in its fundamentals. This paper presents a new approach of the research in the field, bringing both theoretical and practical original contributions to the knowledge of the cold welding principle and creating the bases for the development of new processes addressing modern materials. The approach is based on a FEM capable to predict the material behaviour during the up-setting, considering several constrains introduced by the used FEA code: non-linear static analysis, large strain and large deflection, prescribed displacements. Correlation between stresses and material deformation is further addressed. The dimensions and characteristics of the Mechanical Affected Zone – MAZ (developed in the material due to the up-setting process) are identified

Strain-Hardness Correlation in Aluminium Butt Cold Welded Joints

Butt cold welding is a solid phase welding process where welding occurs by plastic deformation of the metals to be welded. It is obtained by cold pressing until the expansion of the contact zone of the two parts creates contaminant-free areas, allowing the contact and creation of a common lattice between the opposing clean surfaces. Consequently, butt cold pressure welding raises interesting theoretical and practical issues related to the material large plastic deformation, and its consequent hardening. The method used to determine the 99.5%Al hardness-strain correlation is based on Vickers micro-hardness HV0.5 test results on upset bars at different values of effective strain. Two approximations of the relationship between hardness and the effective strain were determined, namely as a rational function, and as a power function. These functions were used for validating an original FEM model of 99.5% Al bar butt cold welding

Development of Robotized Laser Welding Applications for Joining Thin Sheets

Laser Welding (LW) is more often used in manufacturing due to its advantages, such as accurate control, good repeatability, less heat input, opportunities for joining of special materials, high speed, capability to join small dimension parts etc. LW is dedicated to robotized manufacturing, and the fabrication cells are using various level of flexibility, from specialized robots to very flexible setups. This paper features several LW applications using two industrially-scaled manufacturing cells at UPM Laser Centre (CLUPM) of Polytechnical University of Madrid (Universidad Politécnica de Madrid). The one dedicated to Remote Laser Welding (RLW) of thin sheets for automotive and other sectors uses a CO2 laser of 3500 W. The second has a high flexibility, is based on a 6-axis ABB robot and a Nd:YAG laser of 3300 W, and is meant for various laser processing methods, including welding. After a short description of each cell, several LW applications experimented at CLUPM and recently implemented in industry are briefly presented: RLW of automotive coated sheets, LW of high strength automotive sheets, LW vs. laser hybrid welding (LHW) of Double Phase steel thin sheets, and LHW of thin sheets of stainless steel and carbon steel (dissimilar joints). The main technological issues overcame and the critical process parameters are pointed out. Conclusions about achievements and trends are provided

Análisis de la Influencia de los Parámetros Operacionales en Recubrimientos Superficiales Asistidos por Láser de Acero AISI 431 sobre Acero al Carbono

En el presente artículo se muestran los resultados obtenidos de un estudio basado en una serie de recubrimientos de acero inoxidable martensítico AISI 431 sobre acero al carbono. El objetivo principal de este trabajo es valorar la influencia de los principales parámetros operacionales que intervienen en el proceso. This paper presents the main results of a study based on laser cladding of AISI 431 stainless steel powder on low carbon steel experiments. The objective of this work is to show the influence of the processing parameters in the clad

Diseño y desarrollo de un laboratorio virtual de aplicaciones industriales con láser

El objetivo de este trabajo es el diseño y desarrollo de un laboratorio virtual de aplicaciones industriales de los láseres de potencia. La posibilidad de utilizar modelos de simulación con una determinada gestión del conocimiento para facilitar la realización de experimentos prácticos en asignaturas relacionadas con las aplicaciones industriales del láser, así como para el adiestramiento del cuadro técnico de estos sistemas puede ser muy ventajoso con vistas a la reducción del tiempo, recursos y coste del entrenamiento. Si estos modelos son accesibles a través de internet la ventaja se multiplica, ya que esta característica flexibiliza el procedimiento de aprendizaje al eliminar las restricciones espacio-temporales del proceso de instrucción haciendo posible y facilitando su uso tanto en asignaturas de titulaciones oficiales de impartidas en la ETSII-UPM como en la colaboración en la formación técnica entre organizaciones punteras del área de la tecnología láser de diferentes países

Diseño de un Sistema de Monitorización y Control de Procesos de Tratamiento Térmico Superficial de Materiales con Láser Mediante Realimentación de Estados

En el presente artículo se propone el empleo de un innovador Controlador Lineal Mínimo Cuadrático para Procesos de Tratamiento Térmico Superficial de Materiales con Láser, el cual mediante realimentación del vector de estados permite incrementar considerablemente la calidad y uniformidad de los tratamientos realizados, reduciendo de forma significativa la tasa de rechazos y mejorando significativamente la productividad y eficiencia del proceso. De un modo complementario, además de analizar las prestaciones del sistema de control propuesto en base a los criterios típicos de validación, tales como la sobreoscilación y el tiempo de asentamiento, se analizan también otros parámetros de interés, tales como el tiempo y el conocimiento necesario para su diseño e implementación. This paper presents an innovative Linear Quadratic Gaussian Control System for Laser Surface Heat Treatments, which allows to increase significantly the uniformity and final quality of the obtained products, reducing the rejection rate and increasing considerably the productivity and efficiency of the treatment. Besides to analyze the main characteristics and advantages of the developed control system, using the typical validation criteria, such as the overshooting and the settling time, in a complementary way, it is analyzed other unusual parameters of great practical interest, as the design and tuning time, as well as the experience and knowledge necessary for its design and implementation

Induction of Engineered Residual Stresses Fields and Associate Surface Properties Modification by Short Pulse Laser Shock Processing

Laser shock processing (LSP) is consolidating as an effective technology for the improvement of metallic materials surface properties involving their fatigue life. The main acknowledged advantage of the LSP technique consists on its capability of inducing a relatively deep compression residual stresses field into metallic alloy pieces allowing an improved mechanical behaviour, explicitly the life improvement of the treated specimens against wear, crack growth and stress corrosion cracking. Progress accomplished by the authors in the line of practical development of the LSP technique at an experimental level, aiming its integral assessment from an interrelated theoretical and experimental point of view, is presented in this paper. Concretely, experimental results on the residual stress profiles and associated surface properties modification successfully reached in typical materials (especially Al and Ti alloys) under different LSP irradiation conditions are presented, a correlated analysis of the residual stress profiles obtained under different irradiation strategies and the evaluation of the corresponding induced surface properties as roughness and wear resistance being also presented. Through a coupled theoretical- experimental analysis the real possibilities of the LSP technique as a possible substitutive of related traditional surface modification techniques as, for example, shot peening