Influence factors on forging die wear of automotive connecting rods / Fatores de influencia no desgaste de matrizes de forjamento a quente de bielas automotivas

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

A significant part of forgings prices is due to costs from reworks of forging dies because of superficial failures on their surfaces. In quest of a higher competitiveness in terms of prices and production times, it is necessary to understand the mechanisms of die failure to increase its working life, avoiding risk situations and a possible total failure of the tools, and also decreasing costs of reworks, and maintenance and set-ups, achieving a higher productiveness. Besides known changes to increase forging die life such as forging temperature, stroke speed, lubrication (friction) and superficial metallurgical modification on dies surfaces, it is possible to increase die life trough geometrical changes of the die sketch. In this work it has been studied how the modification of the corner radius, flash land width, depth of cavity, radius of the upper stem, flash thickness and temperatures of forging dies and workpiece influence the wear of the forging of connecting rods in the stem region from the preform dies. Through numerical simulation and statistical analysis it was found that the parameters that most influence the process of die wear are the same that affect the die cavity volume which also influence directly the overall width of flash of the forged part. Therefore, the width of a flash is a comparative measure of abrasive wear. It was also analyzed the process of forging in the stem region from connecting rods and it could be verified four distinct stages in the evolution of the abrasive wear, normal stress and forging load. Through this validation it was found that the material flow during the process differs from the observed in available bibliographies and it could be also verified a process of upsetting in the rods stem or a radial flow of the rolled workpiece heads toward the rods stem, which tends to increase the diameter of the workpiece stem. Larger diameters increase the process of abrasive wear, therefore being an important factor to be considered in the design of connecting rods dies. From the analysis of the necessary load to forge the stem region of the rod it was verified that the loading pattern is different when the cavity is not completely filled. Finally through the construction of processing maps it can be determined optimized regions without filling defects, with lower values of wear and thereby increasing die life, keeping the product quality and possibly reducing raw material.

ASSUNTO(S)

mechanical wear utility life forjamento vida util desgaste mecanico forging

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