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Proceedings Paper

Thermal investigation of compound cast steel tools
Author(s): Mirko Schaper; Heinz Haferkamp; Matthias Niemeyer; Christoph Pelz; Roman Viets
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Paper Abstract

Tools for hot forging are exposed to complex stresses during their life-cycle. Therefore, forging dies should have a high wear resistance and toughness on the surface, combined with excellent thermal conductivity in the die body. Hot-work tool steel is appropriate for this application except from its thermal conductance. Hence, a tool consisting of hot-work tool steel in the area of contact and heat-treatable steel as die body is favorable. A smoothly graded microstructure in the joint zone between the two steel alloys is needed to match with the requirements. Fabrication of such functionally graded dies by sand casting exhibits high sensitivity to temperature and geometry dependent parameters. To melt on the inlay's surface must be ensured without destroying this region according to overheat coarsening and mixing of alloying elements. Instead of empirical methods to optimize the process parameters, a thermographic CCD-device is used for visualization of the heat flow while pouring the melt on the inlay. In fact the molten metal flow can be directed homogeneously across the bonding surface at adequate temperatures after evaluation of thermography data. The use of a silica-aerogel sheet as opaque window beneath the inlay in the mold enables systematic development of gating and risering, whereas undesirable scaling of the inlay due to the change of emissivity is retarded. Infrared image sequences clearly demonstrate the influence of different ring gating systems concerning the filling properties. Non-joined cavities may even be classified from image data. Compound cast steel tools have been manufactured and examined in forging trials validating life-cycle prolongation.

Paper Details

Date Published: 19 March 1999
PDF: 7 pages
Proc. SPIE 3700, Thermosense XXI, (19 March 1999); doi: 10.1117/12.342283
Show Author Affiliations
Mirko Schaper, Univ. of Hannover (Germany)
Heinz Haferkamp, Univ. of Hannover (Germany)
Matthias Niemeyer, Univ. of Hannover (Germany)
Christoph Pelz, Univ. of Hannover (Germany)
Roman Viets, Univ. of Hannover (Germany)

Published in SPIE Proceedings Vol. 3700:
Thermosense XXI
Dennis H. LeMieux; John R. Snell Jr., Editor(s)

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