Examination of the forming stability of steels in the

a -Fe+g -Fe transformation phase

Prof. habil. József Gulyás, Assoc. Prof. Gyula Reisz

Department of Metals Technology, Institute of Materials Technology, Faculty of Metallurgy, University of Miskolc, Hungary

At plastic shaping of metals the forming stability is of great importance as - together with the geometry of the forming zone and friction of the tool surface - determines the tension distribution and the nessesary force and power requirement. This is an explanation why the examination of such material properties beyond pure experiments and further theoretical studies are needed.

Traditionally hot shaping is performed at the austenitic (g -Fe) state at 800-1300° C depending on the carbon content. Cold shaping is performed at perlitic, or ferritic+perlitic
(a -Fe) state. The temperature is higher than the environment due to the shaping work and it is usually around 80-300° C. Forming stability of steels at hot and cold shaping was examined by several researchers using different methods.

When thermomechanical methods are used to form steels the transformation is usually taking place in the g -Fe® a -Fe zone between A1 and A3 temperature. Using literature data the result of our own experiments and the Sellars-McTegart analysis we elaborated an approximate calculation method that can yield values for the forming stability of steels in this state.

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