How are galvanized square tubes produced?
Galvanized square tubes is a hollow square cross-section steel pipe with a square cross-section shape and size made from hot-rolled or cold-rolled galvanized strip steel or galvanized coil plate, which is formed by cold bending and then high-frequency welding, or galvanized square rectangular pipes made by hot-dip galvanizing the pre-made cold-formed hollow steel pipes.
Galvanized Square Tubes production process
1. Material preparation: High-quality low-carbon steel coils are used as raw materials, and cut into square tube blanks of appropriate sizes according to specifications.
2. Cleaning treatment: Send the square tube blank into the cleaning tank for pickling treatment to remove grease, oxides and other impurities on the surface to ensure that the surface is clean.
3. Forming: After compression by the forming machine, the raw material is turned into a more regular square profile with straight side walls and seamless welding.
4. Hot-dip galvanizing: Place the square tube in a hot-dip galvanizing pool, and after a series of chemical reactions, a uniform zinc layer is formed. The production process of hot-dip galvanized square tubes is relatively simple and has high production efficiency, which is suitable for the production of small galvanized square tube manufacturers.
5. Cold galvanizing: Using the principle of cold galvanizing, the square tube has anti-corrosion properties. Unlike hot-dip galvanizing, cold-dip galvanizing coatings mainly perform anti-corrosion through electrochemical principles, so the surface treatment of steel is very important.
Due to different production processes, galvanized square tubes are divided into hot-dip galvanized square tubes and cold-dip galvanized square tubes. It is precisely because of the different addition amounts of these two galvanized square pipes that they have many different physical and chemical properties. Generally speaking, they are very different in strength, toughness and mechanical properties.
Hot-dip galvanized square tube: It is a kind of square tube welded by steel plate or steel strip crimped. On the basis of this square tube, after a series of chemical reactions, the square tube is placed in the hot-dip galvanized pool to form a square tube. Hot-dip galvanized square pipe has simple production process, high production efficiency and many specifications. Less equipment and capital, suitable for small galvanized square pipe production enterprises. However, in terms of strength, the strength of this steel pipe is much lower than that of seamless square steel pipe.
Cold-dip galvanized square tube: Cold-dip galvanized square tube uses the principle of cold galvanizing to make the square tube anti-corrosion. Different from hot-dip galvanizing, cold-dip galvanizing coating mainly uses electrochemical principles for anti-corrosion. Therefore, it is necessary to ensure full contact between zinc powder and steel to generate an electrode potential difference, so surface treatment of steel is very important.
The difference between hot and cold galvanizing
Galvanized square tubes are divided into two categories: hot-dip galvanized square tubes and electro-galvanized square tubes. Hot-dip galvanized square pipes include wet method, dry method, lead-zinc method, redox method, etc. The main difference between different hot-dip galvanizing methods is the method used to activate the surface of the pipe body to improve the galvanizing quality after acid leaching cleaning of the steel pipe. Dry method and redox method are mainly used in current production, and their characteristics are shown in the table. The surface of the zinc layer of electro-galvanizing is very smooth, dense and uniform in structure; it has good mechanical properties and corrosion resistance; the zinc consumption is 60% to 75% lower than that of hot-dip galvanizing. Electro-galvanizing is technically complex, but this method must be used for single-sided coatings, double-sided coatings with different coating thicknesses on the inner and outer surfaces, and thin-walled pipe galvanizing.
Galvanizing has stronger protective effect and strong corrosion resistance. The entire structure is made of zinc, forming a dense quaternary crystal. This crystal forms a barrier on the steel plate, thus effectively preventing corrosion factors from penetrating. Corrosion resistance comes from the strong protective barrier layer of zinc. When zinc provides sacrificial protection on trimmed edges, scratches, and scratched parts of the coating, the zinc forms an insoluble oxide layer and plays a barrier protective function.
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