Papers by Author: H. Shimahara

Abstract: The thixoforming processes join the advantages of conventional forming technologies as forging and casting in respect of the mechanical properties and the practicable geometries. Within the framework of the Collaborative Research Centre 289 at the RWTH Aachen University intensive investigations on semi-solid processing with some steel grades have been running. For this purpose an automated thixoforging plant (thixo-cell) has been developed in a closed cooperation with several industrial partners. With this equipment multi material demonstrator components have been successfully produced by thixojoining using semi-solid X210CrW12 tool steel.

Abstract: This paper describes the basic investigation on material behaviour of cold working steel X210CrW12 in semi-solid state concerning the semi-solid forging. It includes a study of flow behaviour and microstructure by means of a high temperature isothermal upsetting test applying a special cylinder sample with a shell, which is designed to avoid collapsing of samples during the compression. The flow curve of the semi-solid steel is determined by an inverse modelling via FEM using the obtained load curve of the samples and the separately obtained flow stress of the shell material. An extensive microstructure study of the compressed samples provides a comprehensive understanding on the flow mechanism of the semi-solid steel. At the end of the paper some general restrictions and remarks for the semi-solid forging process are given based on the gained results.

Abstract: The semi solid forming of steel has the potential of an innovative technology, which could open a new possibility of metal components production. Earlier research works in the 1990s have already shown the principal feasibility of the process but also revealed the various kinds of technical problems. Since then, research works on steel processing have been continuously made in several locations in Japan, USA and Europe. Currently, the focus of these research activities is the development of suitable tool material and the achievement of high part quality, which is the key point for the success of the process. This paper gives an overview of the previous research works and the current state of the research with an outlook on future tasks for this challenge.