Numerical Simulation Of Sherardizing Process And Effect Of Copper Addition In Sherardizing Agent

Sherardizing is a process which involves heating the steel parts up to 400 celsius in a closed rotating drum and keep a certain period of time,zinc evaporates and diffuses into the steel substrate and forming alloy protective coating.It has a wide application prospect in the antisepsis with the advantage of uniform layer,high hardness,material saving,environment friendly and high bonding strength with the substrate.However,the long process and low production efficiency,and layer is mainly aimed at the corrosion in the atmospheric environment,and the limited effect in marine corrosion,which restricts its development.To solve these problems,simulated the zinc diffusion during sherardizing,discussed the influence of temperature and time on zinc layer for shorten the product cycle and reduced costs.The low carbon steel was carried out pack cementation process in different proportion of zinc and copper to improve the ability of steel in the seawater.Study the sherardizing process and established numerical model based on zinc diffusion.Used finite difference method,simulated the law of the zinc content and thickness of each phase with time and temperature.The sherardizing samples were incubated at 360,375,390 celsius for 2,6,8,10 hours,respectively.Phase thickness and zinc content of alloy layer in the samples were measured with scaning electron microscopy and energy dispersive spectrometer and SmileView software.The finite difference method simulation results are in good agreement with the experiment results.The results showed that the law of each phase of zinc layer more accurate than the simulation of zinc concentration field.Through orthogonal experimental design,the zinc agent?zinc,copper,rare earth nitrate,ammonium chloride?were studied.Among the four factors of zinc,copper,rare earth nitrate,and ammonium chloride,the results obtained by the orthogonal test,electrochemical test and salt spray corrosion two evaluation indicators show that among the four factors,the most important factor affecting the corrosion resistance of the infiltration layer is copper content,the order is copper?ammonium chloride?zinc powder and rare earth nitrate.With the addition of copper,formed a trace amount of Zn-Cu phase which changed the structure of the zinc layer;Improves the macroscopic appearance of the coating and reduces defects;The copper addition in the pack cementation,the Zn₅?OH?₈Cl₂H₂O and a small amount of Zn?OH?₂ and ZnO and FeOCI were found in the salt spray test.