Research And Control Of Spangle Uniformity Of Continuous Hot Dip Galvanizing

The technology of hot-dip galvanizing can solve the corrosion problem of metal materials economically and effectively.It is widely used and cost-effective for steel surface treatment.In the hot-dip coating,spangles produced in the form of dendrite can be used to judge the surface quality of hot-dip galvanizing.The existing research focuses on continuous hot-dip galvanizing process and coating properties.However,little attention has been paid to the size and uniformity of zinc coating for hot dip galvanizing.On the basis of Guofeng galvanizing line,this paper studies the factors affecting the size and uniformity of spangles,and then studies the effect of spangles on corrosion resistance and mechanical properties of hot-dip galvanized coating.The main contents of the study include:1)After studying the size,uniformity and morphology of spangles of galvanized sheet with different coating thickness and substrate roughness,it was found that zinc coating weight of 180g/m2 and the upper and lower surface'roughness of 0.80?m galvanized steel sheet were uniform and had metal gloss,but the and upper surface zinc was more incomplete than lower surface;the size of spangle on the upper surface of zinc coating weight of 180g/m2,the upper surface'roughness of 0.80?n and the lower surface'roughness of 0.60?m galvanized steel sheet was 5-10mm(normal spangle),and lower was 10?20mm(big spangle);zinc layer weight was 60g/m2,the upper and lower surface'roughness of 0.80?m galvanized steel plate on the lower and lower surface spangle was uniform silver gray,spangle size was 5-10mm(normal spangle).By comparing the substrate of different specifications,surface roughness and the size of spangle on the surface of the sample with different thickness of zinc layer,it was found that the main factor affecting the uneven size of the upper and lower surface of the spangle was the surface roughness of the substrate.2)After studying the microstructure of the hot-dip galvanized alloy layer was studied,it was found that the microstructure thickness of the upper and lower surface of the 180g/m2 sample was about 14.53?m and 20.34?m respectively.The ? phase,? phase and ? of the lower surface layer were clearer than the upper surface,and the thickness difference of the coating was 5.81?m,and the microstructure thickness of the upper and lower surface of the 80g/m2 sample was about 3.67?m and 3.89?m,the upper and lower surface coating formation,8 phase,?phase and ? phase compared with the fuzzy,little difference in the thickness of the coating.3)After studying the corrosion resistance of galvanized steel sheet with zinc coating weight of 60g/m2 by the salt spray method,the results showed that there was no surface pitting after the salt spray test on the upper surface of the spangle.The surface had slight pitting after the salt spray test on the lower surface of the spangle,and the corrosion resistance of the small spangle surface was better.4)After studying the effect of different Sb content and roughness on the size of spangles,the results showed that when the content of Sb is 0.068%+0.002,the size of spangle on the surface of galvanized sheet was about 3-5mm and the lower surface was 10-15mm When the content of Sb was about 0.15%,the size of spangle on the upper and lower surface increased about 3mm.The result showed that the content of antimony was related to the size of spangles,the greater the content,the less the number of nucleation was formed.The size difference of spangles size on the upper and lower surface of the galvanized steel sheet was larger when the difference of the roughness was equal to 0.1?m continuous hot-dip galvanizing.5)In order to carry out the research on the size and uniformity control of hot-dip galvanized spangles and through the adjustment and optimal control of the production process,it could produced the galvanized product with the size of spangles of 5mm?10mm and uniform spangles on the upper and lower surfaces...