Study On The Plating Property Of Hot - Dip Galvanizing Of Manganese - Ultra - High Strength Steel

The medium manganese steel with high RmxA (30-40GPa%) and low-cost is made as the third generation automotive steel and is currently the world’s R&D hot steel. The paper taked the third generation automotive steel based on medium manganese compositon as the research object, researched the galvanizability.The manganese content of the medium manganese third generation automotive steels is high, and manganese can have bad influence on the galvanizability. The effect of annealing atmosphere(dew point and H2content)with different oxygen potential and preoxidation-reduction process on the surface oxide morphologies and galvanizability of medium manganese alloyed steel were studied. The conclusions are as following:It would be adverse for the galvanisability of the medium manganese alloyed steel when the dew point was too high or too low. the-10℃dew point annealing atmosphere was the best, and there was no bare spot on the hot-dip galvanizing plate. High hydrogen content annealing atmosphere could make the manganese oxide on the steel surface reduce, and improve the galvanisibility;When the oxygen potential was low, the surface oxide morphologies revealed particle states. As the annealing atmosphere oxygen potential increased from low to high, the surface particle oxides gradually reduced, then changed to film-like iron oxides including certain oxide particles.As the oxygen potential increased from low to high, the galvanizability of the medium manganese alloyed steels showed a trend that become better firstly then worsen. Particle oxide surface could be wetted by bridging function within the zinc liquid and more advantageous than film-like oxide surface for the medium manganese alloyed steels;The surface oxide states revealed particles after preoxidation-reduction process,There were a great number of oxide particles on the surface after being annealed at DP-50℃, and the oxide states after being annealed at DP0℃was film-like oxide. The latter two oxide surface above were disadvantageous on the galvanizability of the medium manganese alloyed steels, The development of the inhibition layer particles of hot-dip galvanizing plate annealed after both atmosphere were not sufficient, and didn’t form a continuous inhibition layer.Inhibition layer particles of hot-dip galvanizing plate after preoxidation-reduction Iprocess connected closely to each other, and the inhibition layer was almost all continuous and compact. The preoxidation dew point+5℃was the most suitable to medium manganese alloyed steel for galvanizing.