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Galvanized Pipe -- Also known as galvanized steel pipe, it comes in two types: hot-dipped and electro-galvanized. Hot-dipped galvanized pipe features a thicker zinc coating, even distribution, strong adhesion, and a longer service life. Electro-galvanized pipe is more cost-effective but has a less smooth surface and is much less corrosion-resistant than hot-dipped galvanized pipe.
Square tubes, as the name implies, are tubes in a square shape. Many materials can be shaped into square tubes. Their use and application vary; most square tubes are made of steel, which is unpacked, flattened, coiled, and welded into round tubes, then rolled into squares and cut to the desired length. Typically, there are 50 tubes per package, with larger sizes being more common, ranging from 10*10*0.8-1.5 to 500*500*10-25. Square tubes are categorized by their use, such as structural, decorative, construction, and mechanical square tubes.
Universal Beam -- also known as steel beam, is a long strip steel with an I-shaped cross-section. There are three types of universal beams: standard, light, and H-beam, which are shaped like grooves.
Technical Requirements and Standards for Galvanized Pipe
1. Brand and Chemical Composition of Galvanized Pipe
The steel grade and chemical composition of galvanized steel pipes shall comply with the specifications for black pipe steel grade and chemical composition as stipulated in GB-3092.
2. Method of manufacturing galvanized pipes
The manufacturing method of galvanized pipes (either furnace welding or electric welding) is chosen by the manufacturer. Hot-dip galvanizing is commonly used for galvanizing.
3. Zinc-coated pipe threads and pipe fittings
Galvanized steel pipes with threaded delivery, the threads should be machined after galvanizing, and the threads should comply with YB-822 specifications.
(2) Steel pipe fittings should comply with YB-238 specifications, while ductile iron pipe fittings should adhere to YB-230 specifications.
4. Galvanized pipe specifications and sizes
Nominal Wall Thickness (mm): 2.0, 2.5, 2.8, 3.2, 3.5, 3.8, 4.0, 4.5
Weight Coefficient c: 1.064, 1.051, 1.045, 1.040, 1.036, 1.034, 1.032, 1.028
5. Galvanized Steel Pipe Mechanical Properties
The mechanical properties of galvanized steel pipes prior to zinc coating should comply with GB-3092 specifications. The mechanical properties of steel are crucial indicators for ensuring the final performance (mechanical properties) of the steel, which depend on the chemical composition and heat treatment process. In steel pipe standards, different usage requirements are specified, including tensile properties (tensile strength, yield strength or yield point, elongation), hardness, toughness, and high and low-temperature properties as required by users.
6. Uniformity of galvanized layer on galvanized pipe
Galvanized steel pipes should undergo a test for the uniformity of the galvanized layer. The galvanized steel pipe sample should not turn red (copper color) after being continuously immersed in copper solution five times.
7. Cold Bending Test for Galvanized Steel Pipes
Galvanized steel pipes with nominal diameters not exceeding 50mm should undergo cold bending tests. The bending angle is 90°, with a bending radius of 8 times the outer diameter. The test should be conducted without filling material, and the weld joint of the specimen should be positioned on the外侧 or upper side of the bending direction. After the test, there should be no cracks or zinc layer peeling on the specimen.
8. Zinc-coated pipe hydrostatic test
The hydrostatic test for galvanized steel pipes should be conducted on black pipes, and eddy current testing can be used as an alternative to the hydrostatic test. The test pressure or eddy current testing should comply with the GB-3092 specifications regarding sample dimensions.
Galvanized Pipe Manufacturer: Galvanized Pipe Knowledge Overview
One, Categories and Characteristics of Galvanized Steel Pipes: Galvanized steel pipes are divided into hot-dipped galvanized steel pipes and cold-dipped galvanized steel pipes, with the latter being gradually phased out.
1. Hot-Dip Galvanized Pipe / Hot-Dip Galvanized Steel Pipe
Hot-dip galvanizing involves the reaction of molten metal with the iron substrate to form an alloy layer, thereby bonding the substrate and the coating together. The production of hot-dip galvanized pipes starts with pickling the steel pipes to remove surface oxide iron, followed by washing in a solution or a mixture of water and solution. Then, they are sent to the hot-dip galvanizing tank.
Hot-dip galvanized steel pipes are formed by a complex physical and chemical reaction between the steel pipe substrate and molten galvanizing liquid, creating a corrosion-resistant, tightly structured zinc-iron alloy layer. This alloy layer merges with the pure zinc layer and the steel pipe substrate, resulting in the advantages of uniform coating, strong adhesion, and long service life.
2. Cold galvanized pipe / Cold galvanized steel pipe
Cold galvanized is also known as electroplated zinc, with a very thin coating of only 10-50g/m2, which has much lower corrosion resistance compared to hot-dipped zinc pipes. Reputable zinc-plated pipe manufacturers typically do not use electroplating (cold galvanized) due to this. Only small-scale, outdated equipment firms opt for electroplating, and naturally, their prices are relatively lower.
Galvanized Tube Production Process
The production process of galvanized steel pipes is a trade secret of each manufacturer, so only a general process flow can be provided: a. Round steel preparation; b. Heating; c. Hot rolling piercing; d. Cutting off heads; e. Acid washing; f. Grinding; g. Lubrication; h. Cold rolling processing; i. Degreasing; j. Solid solution heat treatment; k. Straightening; l. Cutting pipes; m. Acid washing; n. Final product inspection.
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