A Study of Die Failure Mechanisms in Aluminium Extrusion

A study of die failure mechanisms in aluminum extrusion A.F.M. Arif * , A.K. Sheikh, S.Z. Qamar Mechanical Engineering Department, King Fahd University of Petroleum and Minerals, Box 1467, Dhahran 31261, Saudi Arabia Received 27 November 2001; received in revised form 27 November 2001; accepted 12 November 2002 Abstract A very important factor contributing to the performance and economics (ef®ciency and quality) of any hot metal-forming process is the service life of tooling. Product rework and rejects can be traced back to various defects spread over the die life-cycle: die design, die manufacture, heat treatment and die service. Initiation and propagation of die damage can be caused by a number of mechanisms. Analysis of tool and die failure thus plays an important role in the prediction and prevention of die failure, and subsequently in improving process economics. This depends to a large extent on the knowledge of the manufacturing and service history of the failed tool and die. Such information is generally not very easily available, and especially not for a large number of die failures and a large spectrum of die pro®les. Very few articles are available in literature that present failure analysis based on a substantial sample size of real die breakdowns. The three most commonly reported modes of die failure are fatigue-based fracture, wear, and plastic deformation/de¯ection. Shape complexity of the die pro®le plays an important role in hot extrusion of aluminum alloys. The paper presents results of an ongoing study about the relationship between die pro®le and modes of die failure. A total of 616 die failures involving 17 different die pro®les were studied, in collaboration with a local industrial setup. All dies were made of H-13 steel, while the billet material was Al-6063 in all the cases. The analysis presented here re¯ects three different perspectives: (a) overall and class-wise break-up of failure modes, (b) failure analysis for dies of different complexities, and (c) shape-wise breakdown of each failure mode. # 2002 Elsevier Science B.V. All rights reserved. Keywords: Die failure; Aluminum extrusion; Metal-forming process 1. Introduction The bulk of structural aluminum pro®les used in the construction industry is produced through hot extrusion. Preheated and properly sized billets of Al-6063 are forced, by the action of a ram, through a die set (separately preheated) placed in the extrusion press container (maintained at a compatible temperature). The die may be round or rectangular or pro®led, and may vary in shape from simple to quite complicated. 1.1. Extrusion die failure Productivity, cost, and quality of the extruded pro®les are of course the overriding commercial factors. And all the three are directly related to the performance of the die, apart from other factors such as billet material, extrusion press and ancillary equipment capability, and latter operations such as age hardening, anodizing and painting. Due to its high cost, based on special material and processing, very ®ne toler- ances, and high demands on repeated thermo-mechanical performance, the most critical extrusion component is per- haps the die. How often a die has to be scrapped and replaced with a new one directly contributes to the commercial viability of producing a certain pro®le. It is therefore of considerable interest to investigate the various factors that contribute to catastrophic or progressive die failure. This paper reports some interesting observations from an ongoing study aimed at identifying and analyzing different mechanisms that lead to extrusion die failure. 1.2. Extrusion die and tooling Flat-face dies are generally used in the hot extrusion of aluminum alloys. The die and tooling arrangement employed in the direct extrusion of soft and medium grade aluminum alloys (1100, 3000 and 6000 series, obviously including Al-6063) is shown in Fig. 1. Functions of the various components shown are listed in Table 1. Con®guration of a solid ¯at-face die is shown schemati- cally in Fig. 2 [1]. The most crucial part of any die is the Journal of Materials Processing Technology 134 (2003) 318±328 * Corresponding author. Tel.: 966-3-860-2579; fax: 966-3-860-2949. E-mail address: [email protected] (A.F.M. Arif). 0924-0136/02/$ ± see front matter # 2002 Elsevier Science B.V. All rights reserved. doi:10.1016/S0924-0136(02)01116-0

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A Study of Die Failure Mechanisms in Aluminium Extrusion