Study Of Surface Selective Oxidation And Galvanizability Of TWIP Steel

AHSS can meet the requirement of improving driving safety factor and reducing vehicle's weight in automotive industry.Hot-dip galvanizing is the most efficient method to enhance the anti-corrosion capability of steel plates.Alloying elements of AHSS readily give rise to surface selective oxides.The surface of selective oxides have bad wetting behaviors with zinc bath that can cause severe coating defects.Therefore,understanding selective oxidation behavior of alloying elements is essential and fundamental work to improve galvanizability of AHSS.The present study discusses the effects of annealing process parameters on selective oxidation of alloying elements of high manganese steel(23-wt%Mn)by theoretical calculation and experimental work and finally gets some rules of the effect of dew point,temperature,hydrogen component,oxygen-potential on selective oxidation of alloying elements,which provides theoretical basis for design annealing process parameters of hot-dip galvanizing.Thermodynamic simulations show that low dew point,high temperature,high H2 component can reduce the oxide on the steel surface.Dew point has the most impact in oxide,followed by temperature and H2 component.We can reduce the oxide and improve zinc coating quality of hot-dip galvanizing by adjusting dew point,temperature,H2 component at the same time.It would be best for the galvanisability of TWIP steel if both of dew point and temperature are too low or too high.H2 component also can affect the galvanisability of TWIP steel,but the effect was not obvious.It would be best for the galvanisability of TWIP steel when both of dew point and temperature was too low or too high.H2 component also can affect the galvanisability of TWIP steel,but the effect was not obvious.Oxide on TWIP steel surface after annealing,inhibition layer particles and element distribution along the thickness direction was investigated by SEM,EPMA,Combined with oxygen-potential,we found the following results:oxygen-potential is the key influence factors of galvanisability of TWIP steel.High oxygen-potential could make Mn is oxidized inside of the steel which makes oxide be reduced on the steel surface.Less oxide on the steel surface can make the inhibition layer particles of hot-dip galvanizing plate become more continuous and compact and can improve the quality of Zn coating.Low oxygen-potential can reduce the presence of on the surface of steel,as not enough oxygen gets to the surface.It also could make the inhibition layer particles of hot-dip galvanizing plate become more continuous and compact and also can improve the quality of Zn coating.Medium oxygen-potential make manganese oxidized outside of the steel increasing oxide on the steel surface.More oxide on the steel surface could make the inhibition layer particles of hot-dip galvanizing plate become sparser and can reduce the quality of Zn coating.