Study On Phase Equilibrium Of Zn–Al–V–Sb Quaternary System And The Effect Of V And Sb On The Microstructure Of Galvanized Coating

Steel is one of the most important metal materials in industrial production,but the corrosion resistance of steel is very low.In many steel anti-corrosion technology,economic and effective method is hot-dip galvanizing process.Up to now,Hot-dip galvanizing technology has been very suitable,and its products have high corrosion resistance and good appearance,consequently,the technology has been applied in many fields,such as electricity,marine machinery and automobiles,etc.Usually,in the actual production process,adding adequate alloy elements into the melt zinc bath usually can effectively improve the structure and the property of the coating.Aluminum(Al)can be a very important additive,to a great extent,to restrain the reaction between iron and zinc,and can also increase the brightness of the coating.The addition of V can be significantly weakened Sandelin effect.Studies have shown that adding moderate Sb to zinc bath can contribute to form a beautiful flower in the coating of the workpiece,reduce the surface tension of liquid zinc and enhance the mobility of zinc bath.In order to have a better understanding of the influence of three elements on the quality of galvanized products,it is necessary to investigate the phase equilibrium of the Zn–Al–V–Sb quaternary system.This experiment adopts the method of study is balanced alloy method,combining with the methods of the scanning electron microscopy,X-ray power diffraction(XRD)and energy dispersive spectroscopy to determine the phase relations in the Zn-rich corner of the 450°C and 600°C isothermal section of Zn–Al–V–Sb quaternary system with Zn being fixed at 93 at.%.On the base of the experimental research,the Zn-rich corner of the 450°C isothermal section of the Zn–Al–V–Sb quaternary system contains four four-phase regions,i.e.,L + VZnSb + AlSb + Sb2Zn3,L + VZnSb + AlSb + Al3 V,L + VZnSb + VZn3 + Al3 V,L + VZnSb + V3 Sb + VZn3,a nd eight three-phase regions,i.e.,L + VZnSb + Sb2Zn3,L + V3 Sb + VZn3,L + VZnSb + Al Sb,L + VZnSb + Al3 V,L + VZnSb + VZn3,L + VZnSb + V3 Sb,L + VZn3 + Al3 V,L + Sb2Zn3 + AlSb.The solubilities of V in the AlSb and Sb2Zn3 phase are only 0.1 at.%.The Sb solubility in the Al3 V phase is very limited.The Zn-rich corner of the 600°C isothermal section of the Zn–Al–V–Sb quaternary system contains two four-phase regions,i.e.,L + Al3 V + AlSb + V3Sb?L + Al3 V + VZn3+ V3 Sb,and five three-phase regions,i.e.,L + AlSb + V3 Sb,L + AlSb + Al3 V,L + VZn3 + Al3 V,L + VZn3 + V3 Sb,L + Al3 V + V3 Sb.The solubilities of Al in the V3 Sb phase are 2.2 at.%.In addition,no new ternary compound or quaternary compound was found in the study.In this paper,the effect of different V and Sb content and the hot dipping time on the thickness and quality of the alloy layer were studied with Q235 steel as the base material(silicon content of 0.202 wt.%),Final results show: The addition of V and Sb elements into the zinc bath can effectively inhibit the Fe–Zn reaction rate,which can inhibit the growth of intermetallic compounds such as FeZn13;When the substrate material is Q235 steel,the ideal coating can be obtained by adding 0.12 wt.%V and 0.1 wt.% Sb to zinc bath,and the dipping time is three minutes.