Speaker
Juliana Porto Guimarães
(Usiminas)
Description
The steel surface condition after continuous annealing is extremely important to the quality of galvannealed coating (GA). The presence of oxides can affect the reactions at the coating/substrate interface and decrease the zinc wettability on the steel surface. To avoid oxidation, a protective atmosphere is used during the annealing. Despite this, it is possible the selective oxidation occurs and dew point is one of the leading factors in order to obtain a favorable surface to galvanizing. This study evaluated the effect of dew point on the quality of GA coatings applied to bake hardening steel. Continuous annealing under dew points from -60°C to 0°C, as well as galvanizing, was performed in a Hot Dip Process Simulator (HDPS). It was found that the dew point has a decisive influence on the amount, distribution and type of formed oxides, and the condition of -30°C provided the coatings with better quality.
Keywords
continuous annealing, dew point, bake hardening steel, galvannealed coating
Authors
Dr
Aldo Henrique de Almeida Barbosa
(Usiminas)
Dr
Berenice Mendonça Gonzalez
(UFMG)
Juliana Porto Guimarães
(Usiminas)
Mr
Ronaldo Rodrigues Vieira
(Unigal Usiminas)