The Development And Application Of The Alloy With Corrosion Resistance To Molten Zinc

According to the problem of the molten zinc-corrosion to materials in the hot-dip galvanizing industry, the research on the development and application of the alloy with corrosion resistance to molten zinc is making in this paper.By adding alloy elements to the metal and examining the corrosion resistance to molten zinc, we find that B element can enhance the performance of the alloy's corrosion resistance to molten zinc. The anti-corrosion ability of the alloy with 7% B is more 10 times than that of alloy before adding B, its corrosion rate is only 15.6 g/m2 ?h. The alloy is hardly corroded by molten zinc when its B content exceeding to 8.83%. At the same time, the brittleness of Fe-B alloy is increased. Basing on the micro analyzing of Fe-B alloy, we find lots of crisp-hard phases Fe2B or FeB exist in Fe-B alloy, which resist the corrosion of zinc. The form of Fe-B alloy corrosion in the molten zinc is intercrystalline corrosion, therefore we render a model of" short circuit corrosion ", In the course of molten zinc corroding, for the first corrosion to a -Fe existing in the intercrystal region, molten zinc will invade internal region along border of grain and get a " short circuit " behind Fe2B grains which results in the Fe2B grains' falling from matrix. As result, the Fe-B alloy is corroded.It is show that alloying Fe-B alloy with Mo, W can inhibit intercrystalline corrosion and enhance alloy's ability to resisting to molten zinc. The anti-corrosion ability of the alloy alloyed with Mo and W is more 10 times than that of alloy before alloying, its corrosion rate is only 1.42 g/m2 +1. Basing on the microanalyses of the alloy, we find lots of wadding phases Mo2FeB2 disperse in the intercrystalline area, which resist the intercrystalline corrosion by molten zinc. About the corrosion of this alloy, we render a model of" plug corrsion ". That is, the molten zinc will react with rudimental a -Fe crossing the phase Mo2FeB2, then, the great stress will be generated by the accumulation of reaction products in the intercrystal region, which make Fe2B grain disintegrate and fall from matrix. So, through composition meliorating and grain malleableizing by adding rare earth elements, the alloy corrosion rate can drop to 0.667g/m2 ?h.Besides, by testing the properties of the Fe-B alloyed with Mo, W, we established the proper casting technics, achieving the alloy cast molding.Applying the casing tube of immersion heater made of this alloy to the hot-dip galvanizing industry, the examination of the industry show the casing tubes usually rupture after running about 50 days. Basing on the analyses, we believe that the reason is alloy's creep at high temperature. So, we must think the high temperature properties of the material besides the corrosion resistance to molten zinc.