001 5页，Analysis of Casting Die Failures, Engineering Failure Analysis

Analysis of casting die failures B. Kosec a, *, L. Kosec a , J. KopacÏ b a University of Ljubljana, NTF, Department of Materials and Metallurgy, AsÏkere Áeva 12, 1001 Ljubljana, Slovenia b University of Ljubljana, Faculty of Mechanical Engineering, AsÏkere Ïeva 6, 1001 Ljubljana, Slovenia Received 11 May 2000; accepted 2 July 2000 Abstract Cracks in the surface of a ®xed die half resulting in imprints on AlSi9Cu3 alloy castings were analysed. The cracks were revealed and identi®ed by the use of penetrants. Some of them were clearly seen by the use of a magnifying glass or even by the naked eye. Non-destructive metallographic examination by SEM of polymeric replicas was applied. # 2001 Elsevier Science Ltd. All rights reserved. Keywords: Cracks; Die failures; Thermal fatigue; Non-destructive testing; Surface cracks 1. Introduction Cracks which appeared in sharp transitions between two planes of a ®xed die half (Fig. 1) after less than 1000 shots were revealed and identi®ed by the use of penetrants (Fig. 2). Some cracks were clearly seen by the use of a magnifying glass or even by the naked eye. The die was made from the well known BOEHLER W300 ISODISC hot work tool steel [1,2] which has frequently been used for similar tools. The chemical composition of the steel is given in Table 1. It can be seen that the steel corresponds to AISI H11 and DIN X40CrMoV5-1 [3]. It was manufactured in the Slo- venian Metal d.o.o. steelworks, Ravne na Koroskem under the trade name Utop Mo 1. 2. Experimental procedure Readily accessible convex parts of the die half were polished by ®ne grade (higher than 500) emery paper and diamond paste and examined by optical microscope. Polymeric foils were used to take imprints from the surface of the prepared spots. The replicas obtained were so sharp that even small details of the surface e.g. microstructure compounds could easily be observed with an optical as well as a scanning electron microscope. High depth of ®eld characteristic of SEM (scanning electron microscopy) resulted in a sharp three-dimensional image of the observed object. Naturally, concave parts of the die half surface, where the 1350-6307/01/$ - see front matter # 2001 Elsevier Science Ltd. All rights reserved. PII: S1350-6307(00)00032-7 Engineering Failure Analysis 8 (2001) 355±359 www.elsevier.com/locate/engfailanal * Corresponding author. Tel.: +386-1-20-00-410; fax: +386-1-417-04-560. E-mail address: [email protected] lj.si (B. Kosec).

001 5页，Analysis of Casting Die Failures, Engineering Failure Analysis

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