Evaluating the Bauschinger Effect in Heavily Cold Worked 301 Austenitic Stainless Steel used in Multi-Layer Head Gaskets

Microhardness distributions gave an indication of Bauschinger phenomena in the forming of heavily cold rolled and tempered 301 austenitic stainless steel sheet. Stainless steel sheet samples from different lots were cut longitudinal and transverse to the cold rolling direction in the as-received and tempered conditions, bent to varying radii, and microhardness distribution obtained throughout the thickness in the principal section of the bend. Microhardness differences between the sections of the bend that underwent tensile and compressive strains were significantly different, indicative of a strong Bauschinger effect, defined in the general sense of “strain softening”. The degree of softening due to the Bauschinger effect (BE) varied with bend radius, direction of rolling, and tempering conditions. Correlations were made of the Bauschinger effect with microstructure and texture of the sheet. The microhardness distribution method was useful in ascertaining the variation in the Bauschinger effect between two lots of steel and potential problems noted in dimensional control during the manufacture of precision formed automotive head gaskets.