Study On Crystallization Characteristics, Surface Tension And Fluidity Of Hot Dip Galvanizing Bath

The development is still the most effective method of steel protection that hot dip galvanizing technology has been invented for more than 300 years of history.The research on hot dip galvanizing has focused on the microstructure and corrosion resistance of the coating after the formation of the coating,but there is little research on the zinc bath which has important influence on the coating,in view of this,in this paper,based on the national fund project "the research on the pre-control of zinc bath characteristics and coating properties" the crystallization characteristics,surface tension and fluidity of zinc bath are studied,which provides the theoretical basis for the establishment of the pre judgment model.Cooling curve of zinc bath that Zn,Zn?0.05%Al,Zn?0.1%Al,Zn?0.2%Al,Zn?0.3%Al,Zn?0.5%Al,Zn?0.2%Al?0.2%RE,Zn?0.2%Al?0.3%RE was determined by thermal analysis technique in 430?450?,the cooling curve was measured by thermal analysis technique,and the differential curve was calculated by mathematical algorithm,undercooling was calculated according to the characteristic value of the cooling curve,the effects of temperature,aluminum and rare earth on the crystallization of zinc bath and the undercooling of zinc bath were analyzed;The surface tension of zinc bath was measured by detachment of a plate,the effects of temperature,aluminum and rare earth on the surface tension of zinc bath were analyzed;the fluidity of zinc bath was analyzed by metal casting mold casting method,the effects of temperature,aluminum and rare earth on the fluidity of zinc bath were analyzed.In this paper,the following conclusions are drawn:the effective nucleation undercooling degree of pure zinc bath is 16.1?at the temperature of 430?,which is far less than 83.9?of homogeneous nucleation of pure zinc,and the pure zinc bath is cooled by non homogeneous nucleation.At 430?520?,the undercooling of pure zinc bath is from 16.1 to 7.6?,and the higher the pouring temperature is,the smaller the undercooling is,the lower the actual crystallization temperature is.In the condition of the same pouring temperature,the aluminum content promoted the heterogeneous nucleation of the zinc bath,which can reduce the nucleation interfacial energy,zinc bath occurs crystallization nucleation in the smaller undercooling,undercooling turn lower with the increasing of aluminum content,rare earth can reduce the undercooling of zinc bath more than the same content the aluminum.The surface tension of the zinc bath decreases with increasing temperature,and the surface tension of the zinc bath under the same temperature is smaller than that in the vacuum state.Aluminum and rare earth can reduce the surface tension of the zinc bath.The fluidity of zinc bath decreases with the increase of temperature.Aluminum can reduce the flow performance of zinc bath,and the rare earth can improve the flow performance of zinc bath,the flow length is 36.9?49.lcm between 430?520?.