Abstract

Large components, for instance in the energy industry, mining and heavy machinery, are produced from high weight cast as ingots followed by open-die forging. Besides achieving a certain final geometry and microstructure, one of the main objectives during the forging process is the elimination of casting defects, like voids from the solidification shrinkage. This process is divided in the two stages of void closure and void healing. During the healing of the closed void a solid bond is established at high temperature. In literature void closure in open die forging is thoroughly investigated. Concerning the healing by solid bond generation there are only few studies related to voids in open die forging but there is substantial literature related to bond formation in roll hot bonding and diffusion bonding. Most of this work however determines the bond strength after cooling to room temperature. Concerning future appropriate modelling of the closure and healing process in open die forging, it is important to decide, whether a bond, which was established in one forging stroke, would be strong enough to withstand the following strokes. As a first step in this direction, this paper experimentally examines the bond strength directly after bond formation under conditions typical for open die forging strokes. The results quantitatively confirm the expected influence of forming temperature, surface enlargement, holding time and oxide films.

中文翻译：

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开模锻造封闭的空洞的结合强度分析

摘要

大型零件，例如能源工业，采矿和重型机械中的零件，是由高重量铸锭制成，然后进行开模锻造。除了获得一定的最终几何形状和微观结构外，锻造过程中的主要目标之一是消除铸造缺陷，例如凝固收缩产生的空隙。该过程分为空隙闭合和空隙愈合两个阶段。在封闭的空隙愈合期间，在高温下建立了固体键。在文献中，彻底研究了开模锻造中的空隙闭合。关于通过固体结合剂产生的愈合，只有很少的与开模锻造中的空隙有关的研究，但是有大量的文献与辊式热结合和扩散结合中的结合形成有关。然而，大部分工作决定了冷却至室温后的粘结强度。关于未来在开模锻造中闭合和恢复过程的适当建模，重要的是确定在一个锻造行程中建立的结合力是否足以承受随后的行程。作为朝这个方向迈出的第一步，本文在典型的开模锻造行程条件下，通过实验检验了粘接强度。结果定量证实了成形温度，表面扩大，保持时间和氧化膜的预期影响。在一个锻造行程中确定的强度足以承受以下行程。作为朝这个方向迈出的第一步，本文在典型的开模锻造行程条件下，通过实验检验了粘接强度。结果定量证实了成形温度，表面扩大，保持时间和氧化膜的预期影响。在一个锻造行程中确定的强度足以承受以下行程。作为朝这个方向迈出的第一步，本文在典型的开模锻造行程条件下，通过实验检验了粘接强度。结果定量证实了成形温度，表面扩大，保持时间和氧化膜的预期影响。