PRODUCTION OF SUPERPLASTIC UHC LIGHTWEIGHT STRUCTURAL STEELS HAVING ALUMINUM CONTENT AND THE PROCESSING THEREOF BY HOT FORMING

摘要

The invention relates to a method for producing the superplastic microstructure of semifinished goods made of UHC lightweight structural steels having an alloy composition C from 0.8 to 1.6 weight %, Al from 5 to 10 weight %, Cr from 0.5 to 3 weight %, SI from 0.01 to 2.8 weight %, and the remainder iron, and typical impurities associated with steel, comprising the steps a) heating the steel to a homogenizing temperature in a range of up to 200°C above the austenization temperature (Acm), b) hot forming at a degree of deformation 1.2 under continuous cooling to a temperature in the range of up to 200°C below A1 (A1 temperature), c) hot forming at a temperature in an upper temperature range from A1 to A1+ 200°C, and d) slow cooling at a cooling rate below 20°C/min to a temperature below A1, wherein the hot forming takes place quasi-isothermally at a degree of deformation 0.5 and with a holding time of the steel at the hot forming temperature of less than 2 min.