Study of the Impact of Quenching Process Parameters in High Dimension Rings of Steel AISI 4140
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Study of the Impact of Quenching Process Parameters in High Dimension Rings of Steel AISI 4140 C. Márquez1,2, E. Martínez1,2, J. Cárdenas2, O. Saldívar2, J. Rodríguez2, F. Fernández2 and A. Pérez1. 1
Universidad Autónoma de Nuevo León, FIME, Ave. Universidad s/n, Cd. Universitaria, San Nicolás de los Garza, N.L. 66450 México. 2 Frisa Forjados, S.A. de C.V. P.O. Box 1273, Monterrey, N.L. 64000 México. Email: [email protected]
ABSTRACT Manufacturing of high dimension steel rings impose several technological challenges. The lack of understanding of the principles and practices of quenching can result in inadequate hardness, excessive distortion or scrapping of costly machined components. This paper presents the results of an analytical study of the parameters of the quenching operation, among them the fluid dynamics of the agitation in the quenching media. Velocity components of the fluid were measured using an anemometer inside the quenching tank. Uniformity of agitation is compared with a Computational Fluid Dynamics (CFD) simulation. The CFD results revealed the impact of quench tank design, configuration and operation of impellers. Keywords: Simulation; Fluid; Thermal conductivity; Forging; Metal. INTRODUCTION The rings are hot conformed by ring-rolling and then are heat treated to relieve stresses and to homogenize the microstructure. Further on, the rings are quenched in a solution of polymer. This operation is one that account for the adverse residual stresses which can turned on to distortion of the pieces. Tempering helps to reduce the level of residual stresses but it does not eliminate all of them. And, residual stresses appear to be inhomogeneous along the piece. One source of this inhomogeneous is the chemical segregation, which will be reported somewhere else [1]. Those rings are manufactured in structural steel 1% Cr, 0.20% Mo, and 0.40% C, similar to AISI 4140. To achieve optimum mechanical properties, these alloys are usually heat treated by quenching in an aqueous solution of polymer from the hardening temperature, then tempered. This produces a microstructure with high strength and excellent toughness, ideal for applications involving heavy loading and cyclic fatigue [2-6]. Heat transference capacity in a quenching process is affected by several parameters. One of those is the kind of quenching media and the agitation of the bath. For high dimensions pieces such as rings, the quenching pools are a complicated array of impellers. In this study, a pool will be considered with an array several impellers on the bottom. In such array, turbulence generated will strongly depend on the type, capacity and orientation of the impellers. With so many variables, the need for modeling of the quenching process is being more needed [7, 8].
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EXPERIMENTAL PROCEDURE This study started with the evaluation of the array of several impellers on the floor. First, information was generated for a single impeller working independently. The measures of flow were made with an anemometer which gave a measure of t
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