Process characteristics and theoretical weight formula of galvanized pipes
1. Optimization of sulfate galvanizing
The biggest advantage of sulfate galvanizing is that the current efficiency is as high as 100% and the deposition rate is fast, which is unmatched by other galvanizing processes. Because the crystallization of the coating is not fine enough, the dispersion ability and deep plating ability are poor, so it is only suitable for electroplating of pipes and wires with simple geometric shapes.
The sulfate electroplating zinc-iron alloy process optimizes the traditional sulfate galvanizing process, retaining only the main salt zinc sulfate, and discarding the other components.
An appropriate amount of iron salt is added to the new process formula to form a zinc-iron alloy coating from the original single metal coating. The reorganization of the process not only carries forward the advantages of high current efficiency and fast deposition rate of the original process, but also greatly improves the dispersion ability and deep plating ability. In the past, complex parts could not be plated, but now both simple and complex parts can be plated, and the protective performance is 3 to 5 times higher than that of single metal.
Production practice has proved that the coating grains used for continuous electroplating of wires and pipes are finer and brighter than the original ones, and the deposition rate is fast. The coating thickness reaches the requirement within 2 to 3 minutes.
2. Conversion of sulfate zinc plating
Sulfate electroplating zinc-iron alloy only retains the main salt zinc sulfate of sulfate zinc plating. The remaining components such as aluminum sulfate and alum (potassium aluminum sulfate) can be removed by adding sodium hydroxide to generate insoluble hydroxide precipitation during the plating solution treatment; for organic additives, powdered activated carbon is added for adsorption removal.
Experiments show that aluminum sulfate and potassium aluminum sulfate are difficult to be completely removed at one time, which has an impact on the brightness of the coating, but it is not serious and can be consumed as it is taken out. At this time, the brightness of the coating can be restored. The solution is treated and can be supplemented according to the content of the components required by the new process, that is, the conversion is completed.
3. Fast deposition rate and excellent protective performance
The current efficiency of the sulfate electroplating zinc-iron alloy process is as high as 100%, and the fast deposition rate is unmatched by any galvanizing process. The running speed of the fine tube is 8 to 12 m/min, and the average coating thickness is 2m/min, which is difficult to achieve with continuous galvanizing.
The coating is bright, delicate and pleasing to the eye. According to the national standard GB/T10125 “Artificial atmosphere test-salt spray test” method, after 72 hours, the coating was intact and unchanged; after 96 hours, a small amount of white rust appeared on the surface of the coating.
4. Unique clean production
The galvanized pipe adopts the sulfate electroplating zinc-iron alloy process, which is that the production line slots are perforated directly without any solution carryover or overflow. Each process of the production process consists of a circulation system. The solutions of each tank, namely acid and alkali solution, electroplating solution, light and passivation solution, are only recycled and reused without leakage or discharge to the outside of the system. The production line has only 5 cleaning tanks, which are recycled and reused regularly, especially the production process without wastewater generation after passivation.
5. The particularity of electroplating equipment
The electroplating of galvanized pipes is the same as the electroplating of copper wire, which belongs to continuous electroplating, but the plating equipment is different. The plating tank is designed for the slender strip of iron wire, and the tank body is long, wide and shallow. During electroplating, the iron wire passes through the hole and spreads out in a straight line on the liquid surface, maintaining a distance from each other. However, galvanized pipes are different from iron wires. They have their own unique features and the tank equipment is relatively complex.
The tank body consists of two parts, the upper part is the plating tank, and the lower part is the solution circulation storage tank, forming a trapezoidal tank body that is narrow at the top and wide at the bottom. There is a channel for the electroplating of galvanized pipes in the plating tank. There are two through holes at the bottom of the tank that are connected to the storage tank at the bottom, and form a plating solution circulation and reuse system with the submersible pump.
Therefore, the plating of galvanized pipes is dynamic, just like the electroplating of iron wires. Unlike the electroplating of iron wires, the plating solution of electroplated galvanized pipes is also dynamic.
Theoretical weight formula of galvanized pipes:
(diameter-wall thickness) x wall thickness x 0.02466*1.0599 = weight per meter (kg/m). In the steel pipe standard, according to different use requirements, tensile properties (tensile strength, yield strength or yield point, elongation) and hardness, toughness indicators, as well as high and low temperature performance required by users are specified.
Nominal wall thickness (mm): 2.0, 2.5, 2.8, 3.2, 3.5, 3.8, 4.0, 4.5.
Coefficient parameter (c): 1.064, 1.051, 1.045, 1.040, 1.036, 1.034, 1.032, 1.028.
Note: The mechanical properties of steel are important indicators to ensure the final performance (mechanical properties) of steel, which depends on the chemical composition and heat treatment system of steel.
Steel grades: Q215A; Q215B; Q235A; Q235B.
Test pressure value/Mpa: D10.2-168.3mm is 3Mpa; D177.8-323.9mm is 5Mpa
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