Hot-dip galvanized sheet is hot-rolled galvanized sheet, cold-dip galvanized sheet is cold-rolled galvanized sheet. In terms of material, the composition of the two galvanized sheets is basically similar, the difference is that cold-galvanized sheet is better than hot-dip galvanized sheet The thickness is thinner, the surface source quality is better, the process is more complicated, and the price is higher.
From the technical point of view, the steel is sent from the billet to hot rolling and rolled into a plate of a certain thickness, such as a thickness of about 10mm.If the user does not have higher requirements on the surface, thickness and mechanical strength of the plate, the finished product can be processed. If it is galvanized or the like, it is directly sold as a hot plate. If there are higher requirements for the board, the hot-rolled board is sent to the cold-rolling line for reprocessing, after pickling, annealing, and rolling again, to obtain thinner, smoother surface, and better mechanical properties cold rolled plate.
1. Hot-dip galvanizing generally has a thick zinc layer, about 10um or more, and has a strong anti-corrosion ability, so it is a commonly used galvanizing process. The electroplated zinc is very thin, about 3-5um, the surface of the hot-dip plating is rough and bright, and the severe one has zinc flowers, and the electroplating is smooth and gray (fouling). The galvanized steel plate produced by the electroplating method has good processing performance but the coating is thin, and the corrosion resistance is not as good as the hot-dip galvanized steel plate.
2. Cold galvanized is electro-galvanized, and the amount of galvanizing is very small. Only the outer tube wall is galvanized (hot-plated-both internal and external), and its corrosion resistance is only 10-50g / m2. The galvanizing amount of hot-dip galvanizing cannot be too small, generally the minimum is 50 ~ 60g / m2 on both sides, the maximum can reach 600g / m2, the galvanized layer of the electrogalvanized sheet can be very thin, the minimum is 15g / m2, and the maximum is 100g / m2 or so. In addition, electro-galvanized zinc can be plated on only one side, or galvanized on both sides, hot galvanized must be galvanized on both sides.
3. Chemical industry generally has more electro-galvanized, suitable for small parts; hot-dip galvanized is generally used for power equipment and components, suitable for large parts and equipment.
4. Hot-dip galvanized sheet and electro-galvanized sheet are fundamentally different in plating structure. There is a slightly brittle compound layer between the pure zinc coating of the hot-dip galvanized sheet and the steel strip substrate. Most of the pure zinc coating forms zinc flower when crystallized, and the coating is uniform and non-porous. The zinc atoms of the electroplated zinc layer are only deposited on the surface of the steel strip, and they are attached to the surface of the steel strip by physical action. There are many holes to dry, which is easy to cause pitting corrosion due to corrosive media, so the hot-dip galvanized sheet is better than the electro-galvanized sheet More resistant to corrosion.
5.The heat treatment process of hot-dip galvanized and electro-galvanized sheets is also completely different. Hot-dip galvanized sheets generally use cold-hardened plates as raw materials, which are continuously annealed and hot-dip galvanized on the galvanizing line.After the steel belt is heated within a short time It is also cooled, so the strength and plasticity are affected to a certain extent, and its stamping performance is worse than that of the cold-rolled sheet after the same cold-hardened sheet is degreased and annealed by a professional production line. Electrogalvanized sheet uses cold-rolled sheet as the raw material, which basically guarantees the same processing performance of cold-rolled sheet, but its complicated technological process also increases production costs.
In short, the production cost of hot-dip galvanized sheet is lower, and the application range is wider, and it has also become the main variety in the galvanized sheet market.
6. Compared with electro-galvanized steel sheet, hot-dip galvanized sheet has the characteristics of thick zinc layer, good corrosion resistance and low production cost.
7.The surface quality of electro-galvanized sheet is more excellent, the coating layer is evenly distributed, and its weldability, paintability and stamping formability are better than hot-dip galvanized sheet; single-sided, double-sided or poor-thickness coating can be easily switched during production . However, in the electrogalvanizing process, zinc sends zinc ions in the electroplating solution to the steel plate by current. The thicker the coating, the more power is consumed and the cost is higher.
This post is also available in: Russian