Learn the benefits of hot-dip galvanizing method used

Guangdong galvanizing plant is relatively old hot-dip method evolved since the 1836 French used in industrial hot dip galvanizing, has 170 years of history. However, the hot-dip galvanizing industry is accompanied by the rapid development of the last three decades of cold rolled strip which has been large-scale development. The method now face a galvanized steel sheet is mainly used in hot-dip galvanizing.

 

Hot galvanized sheet production processes include: the original board ready → → → hot-dip coating process → finished product inspection after plating pre-treatment. By convention often depending on the plating pretreatment method of hot-dip galvanizing process is divided into the outer annealing line and in-line annealing two categories, namely wet (single galvanized steel sheet method), the line outside the annealing (hot-dipped steel leaflets zinc law), hot dip galvanized Wheeling (Wheeling) method (continuous hot-dip galvanizing method), in-line annealing Sendzimir (Sendzimir) method (protective gas law), modified Sendzimir US steel Union law (with Japan Kawasaki France), Silas (Selas) method and Sharon (Sharon) method.

 

Annealing line outside

 

Hot-rolled or cold-rolled steel is before entering the hot galvanizing line, the first pumping bottom type annealing furnace or hood-type annealing furnace recrystallization annealing, so galvanizing line does not exist the annealing process. Hot dip galvanized steel sheet before must be a non-oxide and other dirt active presence of clean iron surface. This method is for the pickling method of the annealed surface oxide skin clear, and then coated with a layer protected by a solvent consisting of zinc chloride or ammonium chloride and zinc chloride mixed composition, thus preventing further oxidation of the steel sheet .

 

(1) a single plate

 

 

Guangdong galvanizing plant this method is generally used as a raw material of hot-rolled plate Roll, first annealed steel sheets into the pickling plant, sulfuric acid or hydrochloric acid to remove heat oxygen steel surface galvanizing of metal. Steel pickling immediately after soaking into the tank waiting for zinc, which can prevent steel reoxidation. After pickling, water washing, squeezing, drying, into the zinc pot (temperature kept at 445-465 ??) hot dip galvanized and then coated with oil and chrome treatment. This method of production of hot dip galvanized sheet has improved significantly over the wet galvanized product quality, only a certain value to small-scale production. (3) The wheeling method hot continuous galvanizing line, including degreasing lye, hydrochloric acid, water washing, solvent coating and drying a series of pre-treatment process, and the original plate into the front galvanized galvanizing line also need to cover formula annealing furnace. This method of production of complex, high production costs, more important is the method of production of goods often with solvent defects affect the corrosion resistance of the coating. Zinc pot of AL and solvents often play a role in generating the steel surface aluminum trichloride and consume, coating adhesion deteriorates. Therefore, although this method has been available for nearly three decades, but in the world hot-dip galvanizing industry has not been developed.

 

(2) Wet galvanized

 

Solvent steel surface without drying (ie, the surface is still wet) hot-dip galvanizing proceeds from the surface is covered with molten zinc solvent liquid. The disadvantage of this method is:. A state can only be galvanized in lead-free, plating alloy layer is very thick and very bad adhesion. b. dross generated are accumulated at the interface between the liquid zinc and lead were not deposited pot (because gravity is greater than the liquid zinc dross and less than molten lead), because this steel zinc layer through contaminated surfaces. Therefore, this method has basically been eliminated.