The aim of the present work is to verify the microstructural behavior of a B 521 tantalum alloy UNS Grade R05200 after welding, in relation to the welding thermal cycle. The joint design was a 1.5 mm thickness circumferential butt welding, on a 32 mm outside diameter pipe, welded in 1 G position (horizontal, flat, and rotating). The chosen welding process was gas tungsten arc welding (GTAW). The microstructural analysis showed the presence of coarse, dendritic-columnar structures, as well as a hexagonal cell, with no cracks noted. Hardness tests showed an increase in hardness, from 120 HV to 425 HV, in the heat-affected zone. Through finite element methods, the behavior of the temperature field was estimated and compared.
En este artículo se hace una caracterización microestructural de las transformaciones que ocurren en una soldadura disímil, mediante el proceso de soldadura de gas y tungsteno, entre la aleación de tantalio B 521 y el acero inoxidable AISI 316. La costura se realizó a tope, en tuberías de 1,3 milímetros de espesor, con electrodo no consumible de tungsteno al 2 % de torio (WT20). Los parámetros del ciclo térmico considerados fueron la velocidad de soldadura, la energía lineal y entrante del proceso. En esta unión, por efecto de la transferencia de calor, se generó estructura del tipo columnas tosca, estructuras dendríticas, así como una estructura de una red de células hexagonales y ferrita-δ. En el barrido de dureza se determinó un incremento en la zona afectada por el calor de 200 HV en el primero (Tantalio) y de 285 HV para el segundo (acero inoxidable), con un valor de 525 HV en la zona fundida.
This work presents the techniques used in an experimental design leading to evaluating the behavior of an independent variable force (P), ranging from 500 up to 2500 N, 27 minimum revolution number (n), average 54 and maximum 110 rev/min and 0.075, 0, 125 and 0.25 mm/rev advance for determining the dependent hardness (H) pattern when AISI 1045 steel test tubes were subjected to surface rolling for creating a compressive state deforming and increasing its resistance to abrasive wear and fatigue. The variables involved in the process were statistically analysed, revealing increased hardness ranging from 220 up to 262 HV. Optical microscopy was used for analysing the effect of hardening caused by deformation, establishing a mechanism for hardening steel by the elements in the crystalline network sliding due to burnishing.
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