Precision Forging of Cast Preforms

在模锻实践中，复杂形状的零件是从截面面积恒定的简单半成品开始，分多步逐步锻造的。这就提出了设计具有适当预成形几何形状的工艺序列的挑战，这主要取决于零件几何形状、可用的成形设备和某些工艺参数。所有这些方面都对工艺的设计灵活性提出了衡量标准。受限的工艺设计可能会产生许多后果，包括但不限于材料利用率低、产品有缺陷、启动时间更长、工装成本增加和多余劳动力。锻造铸造预制件(铸件/锻件)技术是解决这些问题的一种简单而有效的方法，是传统模锻法的一种很有前途的替代方法。尽管有一些铝加工的铸造/锻造例子，但在钢加工方面存在技术差距。此外，精密(净形状或近净形状)锻造原理从未被纳入此类工艺技术。这项研究的主要目的是了解铸造预制件在变形加工过程中的力学和组织性能的演变，并确定合适的加工条件。为此，计划了一个两阶段工作方案。在第一阶段中，将深入研究变形处理对铸件组织的影响，采用缸体镦粗工艺。通过广泛的表征试验，将显微组织处理和变形历史联系起来。在第二阶段，将根据第一阶段的研究结果，对复杂形状的演示器进行铸造/网状锻造加工。将对铸造/锻造技术有一个基本的了解，并将丰富目前缺乏信息的文献，特别是在钢的加工方面。预计研究结果还将产生新的创新概念。

In die forging practice, intricate shaped components are progressively forged in multiple steps starting from simple semi-finished workpieces that are constant in cross sectional area. This presents the challenge of designing a process sequence with appropriate preform geometries which mainly depends on the part geometry, the available forming equipment and certain process parameters. All these aspects set measures to the design flexibility of the process. A restricted process design may have many consequences including but not limited to low material utilisation, defective products, longer run-up times, increased tooling costs and redundant labour. The technology of forging cast preforms (casting/forging) appears as a promising alternative to the conventional die forging to handle such problems in a simple but effective manner. Despite a few casting/forging examples for aluminium processing, a technological gap exists in terms of steel processing. Moreover, precision (net or near-net shape) forging principles have never been incorporated into such process technology. The main objective of this research proposal is to gain basic insights into the evolution of the mechanical and microstructural properties of the cast preforms under deformation processing and to identify the proper processing conditions. To this end, a two phase work programme is planned. In the first phase, the influence of deformation processing on the cast structure will be studied thoroughly utilizing cylinder upsetting process. The microstructural treatment and the deformation history will be related by means of extensive characterisation tests. In the second phase, processing of an intricate shaped demonstrator by casting/net-shape forging will be implemented relying on the findings of the first phase. A basic understanding of the casting/forging technology will be gained and the literature will be enriched which at its current state lacks information especially on steel processing. It is expected that the research findings will also give rise to new innovative concepts.