Hot dip galvanising and galvannealing of P and Mn strengthened TiNb IF steels

Abstract

Phosphorus, Mn, or Si solid solution strengthened sheet steels stabilised with Ti and Nb are known to have poor galvanising and galvannealing properties. When these steels are continuously annealed in higher dewpoint atmospheres, selective oxidation processes can occur in the subsurface region of the sheet. A laboratory simulated continuous galvannealing process was therefore used to study this effect in P and PzMn solid solution strengthened sheet steels stabilised with Ti and Nb, by making a detailed analysis of the fundamental surface and interface processes that control the wetting of the surface by the liquid Zn, the inhibition layer formation, and the Fe -Zn reaction.MST/4917

Influence of phosphorous and boron on dynamic recrystallization and microstructures of hot-rolled interstitial free steel

“…Considering that increasing the P and B components has a negative influence on the surface quality of the hot-dip galvannealed IF steel [5][6][7] and addition of P and B to the IF steel leads to decrease its elongation considerably, it might be beneficial for steelmakers to manufacture the IF steel with no P and B if the priority of the products is not strictly fixed on its tensile strength.…”

“…For this reason, B is generally added with P to prevent the embrittlement. Besides, adding P and B components to IF steels may give a negative influence on the surface quality of the IF steel when its final form is hot-dip galvannealed state [5][6][7]. Therefore, examining a combined effect of P and B on IF steel during hot deformation is highly desirable.…”

Design of Composition in (Al/Si)-alloyed TRIP Steels

“…Phosphorus is useful for solid solution strengthening 12,13) and P-TRIP steels have shown interesting microstructural characteristics and mechanical properties. 9,14) However, it has been shown that P additions slow galvannealing kinetics 15) and can lead to cold work embrittlement 16) for low C contents. According to some authors, Al as a solute element does not segregate to the surface during intercritical annealing before galvanizing, 17) so Al additions are not expected to influence the coatability adversely.…”

Numerical Simulation of Flow, Temperature and Composition Variations in a Galvanizing Bath

“…The air knives control the coating thickness by a variation of air pressure and gap width from the strip. The amount of Al in the inhibition layer increases with the Al content in the bath up to 0.20% as was shown by Hertveldt et al [3] as well as with steel composition and temperatures of the steel strip and the zinc bath [4]. Galvanized products for exposed applications are frequently produced in baths containing 0.25% and higher aluminum contents.…”