Experimental Determination of Heat Transfer Coefficients for Forming of Stainless Steel Sheets Considering Process Conditions and Deep-Drawing Film

Abstract:

Heat transfer coefficients are playing an important role in forming of metastable stainless steel sheets. Metastable austenitic stainless steels are highly influenced by heating of forming tools due to generation of latent heat during forming process. Strain-induced martensite formation and hence the TRIP-effect is directly coupled with the temperature development within forming tools as well as the temperature induced by heat controlled tools. Measurements of heat development in serial deep drawing processes are showing the need for an accurate determination of heat transfer coefficients considering actual process conditions. Heat transfer coefficients were determined with a simple and easy applicable measurement device for tool materials AMPCO 25 and cold work tool steel EN 1.2379 in combination with aluminum, austenitic EN 1.4301 and ferritic EN 1.4016 stainless steel grades. Special attention was paid to production-related individual influences such as surface conditions, lubrication and deep drawing film. Experiments were accomplished between 1-15 N/mm² showing high influence of intermediate media on heat transfer between forming tool and part and serve as boundary conditions for fully thermo-mechanical coupled forming simulations. A strong influence of deep drawing film, lubrication and surface pressure on heat exchange could be determined and this basic knowledge is seen as mandatory for dimensioning of heat controlled metal forming tools. Finally the experimental determined results are discussed and compared to common heat transfer models and similar experiments from literature.

• Periodical: Key Engineering Materials (Volumes 554-557)
• Pages: 1501-1508
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.554-557.1501
• Online since: June 2013
• Authors: Philipp Schmid, Mathias Liewald
• Keywords: Deep-Drawing Film, Stainless Steel (SS), Thermal Contact Conductance

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