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Brittle Fracture Behaviors of Large Die Holders Used in Hot Die Forging

School of Reliability and Systems Engineering, Beihang University, Beijing 100191, China
Author to whom correspondence should be addressed.
Academic Editors: Ricardo Branco, Filippo Berto and Daolun Chen
Metals 2017, 7(6), 198;
Received: 4 March 2017 / Revised: 4 May 2017 / Accepted: 25 May 2017 / Published: 30 May 2017
(This article belongs to the Special Issue Mechanical Behavior of High-Strength Low-Alloy Steels)
PDF [28582 KB, uploaded 30 May 2017]


Brittle fracture of large forging equipment usually leads to catastrophic consequences. To avoid this kind of accident, the brittle fracture behaviors of a large die holder were studied by simulating the practical application. The die holder is used on the large die forging press, and it is made of 55NiCrMoV7 hot-work tool steel. Detailed investigations including mechanical properties analysis, metallographic observation, fractography, transmission electron microscope (TEM) analysis and selected area electron diffraction (SAED) were conducted. The results reveal that the material generated a large quantity of large size polyhedral M23C6 (M: Fe and Cr mainly) and elongated M3C (M: Fe mainly) carbides along the martensitic lath boundaries when the die holder was recurrently tempered and water-cooled at 250 °C during the service. The large size carbides lead to the material embrittlement and impact toughness degradation, and further resulted in the brittle fracture of the die holder. Therefore, the operation specification must be emphasized to avoid the die holder being cooled by using water, which is aimed at accelerating the cooling. View Full-Text
Keywords: brittle fracture; property degradation; mechanical properties; failure analysis; 55NiCrMoV7 brittle fracture; property degradation; mechanical properties; failure analysis; 55NiCrMoV7

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Zhang, W.; Wang, H.; Zhang, J.; Dai, W.; Huang, Y. Brittle Fracture Behaviors of Large Die Holders Used in Hot Die Forging. Metals 2017, 7, 198.

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