Opportunities and dangers of using residual elements ... - Jernkontoret

Sn, As, Cu, Ni, Cr and Mo have adverse effets on drawability, decreasing the r value and,to some extent, the ductility of ULC-IF and ELC grades (seeFigure 18 B). [2].Sn and As also have adverse effects on recristallization kinetics during the continuousannealing of cold rolled ELC steel grades (seeFigure 18 A). The temperature for full recrystallisation increases, which implies thatprocess conditions have to adapted to raise the annealing temperature. [16]The tensile properties however were only little affected for residual elements up to 0.03%.However, a marked increase in tensile and yield stress was observed for concentrations of0.08%. SeeFigure 19 for the effect of Sn and As.[2].According to reference [3], Cu, Ni, Cr and Sn decrease grain size and increase solidsolution hardening of thin steel sheet (IF Ti), thus decreasing anisotropy factor r andelongation (seeFigure 19 B).A) B)Figure 19 A) Impact of residual elements on the mechanical properties of annealed cold-rolledsheets (BA = batch annealing, CA = continuous annealing).B) relationship between atomic % and mechanical properties of Cu, Ni, Cr andSn-containing titanium bearing extra low-carbon steel sheets.In a study presented in reference [35 ], Cu and P bearing high strength cold rolled steelsheets with superior drawability have been developed. Cu and P contents are 0.6% and0.08% respectively. The tensile strength of these steels are 500-550Mpa and the r-valuesare as high as 1.5-1.7. The excellent r-values are obtained by precipitation treatment of31