METHOD FOR PRODUCING HARDENED PARTS FROM SHEET STEEL

摘要

The steel plate component comprises a cathodic corrosion-protection layer, where the component is coldly formed to a molded part and is made of a steel plate provided with cathodic corrosion-protection. Before, during or after the cold formation of the molded part, an end trimming of the molded part and required stampings or the production of a hole pattern are carried out. The cold formation and the trimming and the stamping and arrangement of the hole pattern are carried out on the component, so that the molded part is 0.5-2% smaller than the finally hardened component. The steel plate component comprises a cathodic corrosion-protection layer, where the component is coldly formed to a molded part and is made of a steel plate provided with cathodic corrosion-protection. Before, during or after the cold formation of the molded part, an end trimming of the molded part and required stampings or the production of a hole pattern are carried out. The cold formation and the trimming and the stamping and arrangement of the hole pattern are carried out on the component, so that the molded part is 0.5-2% smaller than the finally hardened component. The cold-formed molded part is subsequently heated in partial areas with the admission of atmospheric oxygen to a temperature that enables an austenitizing of the steel material. The heated component is then transferred into a shape hardening tool and a shape hardening is carried out inside the shape hardening tool, during which the component is cooled and hardened by setting and pressing the component through the shape hardening tool. The corrosion protective layer is applied by a melt immersion process and the coating consists of a mixture made of zinc and a mixture with the de-oxygenated elements in a total quantity of 0.1-15 wt.% related to the total mixture. The corrosion protective layer superficially possesses an oxide film made of oxides of de-oxygenated elements and the coating has two phases, where one phase is zinc-rich and other phase is iron-rich. The steel plate forming the component has a strength of 800-2000 MPa. The corrosion protective layer has a cathodic protection effect of 4J/cm 2> with a thickness of 15 mu m. The iron-rich phase has a ratio of zinc to iron of 30:70 and the zinc-rich phase has a ratio of zinc to iron of 80:20. The steel plate component contains individual areas with zinc portion of >= 90 wt.% of zinc. The component is made of hot- or cold-rolled steel strip with a thickness of >= 0.15 mm and with a concentration area of alloy elements.