Oxidation-reduction Reaction Of The Iron In The Tin Bath And Influence Of Iron On Tin Diffusion Into The Float Glass Surface

Float glass is widespread the tin content high and rainbow serious problem, which restrict the deep processing of glass products in China. In order to solve this problem to improve the market competitiveness of float glass in our country, we must study this problem, and then put forward to effective measures to reduce the tin content and glass rainbow. The study found that adding iron to the tin liquid can effectively reduce the tin content of the glass surface, and then reduce the probability that glass rainbow appeared.In this topic, we studied the influence of adding iron in the tin liquid to the tin diffusing of the glass surface by XRF, EPMA and XPS. The Research includes two aspects: One is directly analyzes the glass sample of the production line, the other is analyzes the glass sample which was prepared in a tin-bath simulator. The experiment also simple analyzed the causes of micro bubbles under the glass surface due to add iron in the tin bath.The study found that during the production adding appropriate iron to the tin liquid not only can effectively reduce the tin content of glass surface, the depth of the tin into the glass surface and the relative content of Sn2+on the glass surface, but also can effectively reduce glass rainbow. Adding iron to tin liquid can make more iron into the glass surface, and the iron under the glass surface is mainly Fe3+. The iron in tin liquid not only can react with O2in priority, but also can reduce tin oxide to tin, which has reduced the tin content of glass surface and the depth of the tin into the glass surface. At the same time, the produced Fe3+in the liquid can oxidized Sn2+to Sn4+, and the Fe3+under the glass surface can also oxidized Sn2+to Sn4+, thus the relative content of Sn4+on the glass surface increases. Analyzing the sample prepared in the laboratory found that with the increase of iron content in the tin liquid the tin content of the glass surface decreases firstly and then increases, and the relative content of Sn2+on the glass surface also decreases firstly and then increases, but the relative content of Sn4+on the glass surface increases firstly and then decreases. The minimum tin content is about17.30ug/cm2when iron content was0.40w.t.%, but the maximum relative content of Sn4+is about96.12%. The amount of infiltration of iron increases with the increasing of iron content in the liquid. With the same iron content of tin liquid, the tin content of the glass surface increases with increasing of the annealing time, while the amount of infiltration of iron reduces instead.Actual production found that the content of the iron added to the liquid to control the glass rainbow has an optimization range. The level of glass rainbow is low when the iron content in the liquid is about0.03w.t.%; However the level of glass rainbow is serious when the iron content in the liquid is excessively many too few. The production practice just to verify the results of the previous study:during the production adding appropriate iron to the tin liquid, not only can reduce the tin content of glass surface and the relative content of Sn2+on the glass surface, but also can reduce glass rainbow, but adding less or more can not help to reduce the tin content of glass surface.Practice also found that taking a frequent and smaller way to add iron to the liquid can greatly reduce the bubbles under the glass surface.