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​ Factors influencing the size of zinc flowers

- Aug 06, 2018 -

 Hot dip galvanizing line Factors influencing the size of zinc flowers

    The traditional hot-dip galvanized steel plate has a series of zinc crystal patterns on the surface of the zinc flowers. At present, the common zinc plate is still the most productive basic variety of hot galvanized sheet and all hot plated sheet.From the user's point of view, some users want the zinc flowers to be bigger, and some users want the zinc flowers to be smaller. From the Angle of production, degree says, sometimes the size of the zinc flower in production has changed, need to restore the original zinc flower size. In order to meet the needs of users and keep the surface structure of products normal, we must understand what factors influence the size of zinc flowers.The first factor that affects the size of zinc-flower, as mentioned above, is the composition of zinc-liquid, that is, whether the zinc-liquid contains sharp, lead or bismuth and its content is high or low. If the content is low, zinc-flower is small; if the content is high, zinc-flower is large. But zinc flowers are not infinitely large. For example, the sharp content gradually increases from 0.20% to 0.50%, and the zinc-flower will increase gradually and gradually. After the sharp content exceeds 0.50%, the zinc-flower will not increase.

 

  Hot dip galvanizing line Factors influencing the size of zinc flowers

    After the steel takes out the zinc pot, it usually enters the air cooling section after a long period of air cooling in the condensing cooling section. In the air cooling section, the zinc layer has been solidified. In this regard alone, the air cooling condition is relatively fixed, and it seems that the cooling rate does not change much and will not affect the size of zinc flowers. On the other hand, the cooling rate is affected not only from the outside of the steel belt, but also from the inside of the steel belt.

  

  In December 2005, the company fengnan factory a hot galvanizing unit production of normal zinc plate, suddenly the zinc flower significantly smaller, large zinc plate into small zinc plate, customers refused to accept. And in the production of this batch of products, zinc liquid composition, zinc liquid temperature, unit speed, after - plating blower cooling conditions are the same as usual. Why? After careful investigation by the cadre workers, it was found that all six fans in the cooling section of the continuous annealing furnace were on when the thinner galvanized steel belts were produced, which may have caused the steel belts to cool too much. Later, a large part of the fan in the cooling section of the furnace was stopped, and the size of the zinc flowers was restored to normal. This case shows that the strip was too much of a cooling in furnace cooling section, the zinc pot before the strip temperature is far lower than the zinc liquid temperature, the zinc pot, the temperature of the substrate is still significantly lower than the temperature of the liquid zinc layer board face, substrate absorption board and liquid zinc layer heat quickly, greatly accelerate the zinc layer in the process of solidification cooling rate, and thus generate small zinc flower.In addition, there is a third factor that cannot be ignored that affects the size of zinc-flowers, that is, the cleanliness of the plate. A roll of cold rolled coil weighing from 15 to 181 tons usually produces three hot galvanized rolls. Fengnan factory of the company found that the first and second rolls of zinc flowers were usually of normal size, and the third rolls of zinc flowers were significantly smaller, sometimes accompanied by leakage plating point and bad adhesion of zinc layer. The reason is that: first, the surface of cold rolled coil provided by the previous process is quite dirty, and there are a lot of sundries such as oil and iron powder.

    Hot dip galvanizing line Factors influencing the size of zinc flowers Secondly, a cold rolled coil running big, about two-thirds, entered the late run, in preparation for the volume when the capuchin and rolls under the welding head need to loop capacity, looping entrance filling a set, which makes the length of the cold rolled coil at the back of the third quick by degreasing treatment period, the Duan Gang belt degreasing time greatly shortened, causing them to wash to reduce greatly. PZH steel belt table and sundry more, failed to remove all inside the furnace, not divided clutter its severity is uneven, some serious stuff cause plating leakage phenomenon, due to severe clutter coating adhesion is unqualified, the more serious stuff not although not cause leakage defect plating and coating adhesion, but, after zinc pot, substrate and liquid zinc layer between the numerous fragments as crystallization center, generates numerous small zinc flower.Later, the front-line cadre workers used the method of preloading and slower charging, so that the steel belt passed through the degreasing section of the steel belt during the filling period of the steel belt will not be too short, which alleviates this problem, but has not been fundamentally solved.To the dry plate, the size of the zinc flower is not uniform, the middle zinc flower is large, and the two sides of the zinc flower is small, which is caused by the uneven temperature of the steel belt A, high temperature in the middle, low temperature on both sides.

   Hot dip galvanizing line Factors influencing the size of zinc flowers After the first hot-dip galvanizing unit of steel belt of a steel company in east China is put into production, the annoying phenomenon of large zinc flowers in the middle and small zinc flowers on both sides of the steel belt appears. Analysis of the causes: in the heating section and the heating section of the gas radiation tube, the horizontal temperature distribution is not uniform, the middle temperature is high, and the two sides are low, resulting in high temperature in the middle of the steel belt and low temperature in the side. After the cooling section and the zinc pot, the temperature in the middle of the strip is still higher than that in the side. In this way, the side of the steel belt absorbs the heat of the surface liquid zinc layer, and the liquid zinc layer cools faster. The middle part seldom absorbs or does not absorb the heat of the liquid zinc layer on the surface. The liquid zinc layer cools slowly, and the zinc flower only solidifies when it is fully grown. This phenomenon is relatively easy to occur on the production line of gas heating radiant tube, because it is difficult for gas radiant tube to make the middle and side of steel belt heat evenly.

    In the heating production line of the electric heat radiation tube, the horizontal temperature uniformity of the electric heat radiation tube is generally better than that of the gas radiation tube.