COLD-ROLLED AND RECRYSTALLISATION ANNEALED FLAT STEEL PRODUCT, AND METHOD FOR THE PRODUCTION THEREOF.

摘要

The invention relates to a cold-rolled and recrystallisation annealed flat steel product with a ferritic micro-structure, having an optimised formability and suitability for painting. In addition, the flat steel product is formed by a steel having C: 0.0001-0.003 wt.%, Si: 0.001-0.025 wt.%, Mn: 0.05-0.20 wt.%, P: 0.001-0.015 wt.%, Al: 0.02-0.055 wt.%, Ti: 0.01-0.1 wt.%, as well as respectively optionally Cr: 0.001-0.05 wt.%, V: up to 0.005 wt.%, Mo: up to 0.015 wt.%, N: 0.001-0.004 wt.%. In addition, the flat steel product has the following mechanical characteristics: Rp0.2 = 180 MPa, Rm = 340 MPa, A80 = 40%, n-value = 0.23. Furthermore, on at least one of the surfaces thereof, the flat steel product has an arithmetic roughness average Ra of 0.8-1.6 µm and a peak value RPc of 75/cm. The production of the flat steel product involves, in a continuous process in a N2-H2- annealing atmosphere, the recrystallisation annealing thereof, and an overaging process. Subsequently, the flat steel product undergoes a skin-pass rolling by means of a working roller and with a skin-pass rate D of 0.4-0.7%, the circumferential surface of which working roller has a roughness average Ra of 1.0-2.5 µm and a peak value RPc ≥ 100/cm, wherein the peaks and depressions shaped into the surface of the skin-pass working roller are provided in a stochastically distributed manner.