Specifični pokazatelji obradivosti limova povišene čvrstoće namenjenih automobilskoj industriji

Abstract

Presented in the paper are the results of investigations of high strength steel sheet metal (HSS), especially 'bake hardening" sheets which have the yield strength increased to a high value in the course pf baked paint treatment. For the assesment of deflection tendency we employed YOSHIDA buckling test, and the indicators obtained relate to the HSS capabilities toward shape fixability and fittability. The other formability tests (biaxial stretching) was made in the conditions of realization of a very intensive aging accompanied by hardening, thus simulating the final phase of car body painting (paint baking in accordance with a prescribed thermal regime). In addition to the standard formability characteristics (Rp, Rm, A80, n-value) the hardening intensity was also investigated by determining stress and strain fields in biaxial stretching in different experimental conditions: temperature, depth of draw, contact states etc. Special attention was paid to the determination of stress field in aging specimens from known strain field in nonaging specimens and strengthening curves of aging sheet metal. Determined also were strain fields in nonaging specimens from known stress fields of aging specimens and strengthening curves of nonaging material.