3 / 4 is DN20 Galvanized steel pipe and 1 / 2 is DN15 Galvanized steel pipe

Galvanized steel pipe is divided into cold galvanized steel pipe and hot-dip galvanized steel pipe. Cold galvanized steel pipe has been banned, and the latter is also advocated by the state to be used temporarily. Internationally, developed countries have begun to develop new galvanized steel pipe materials, and galvanized pipes have been banned in succession. Hot dip galvanized steel pipe is widely used in fire fighting, electric power and expressway.

3 / 4 inch diameter is equivalent to DN20 galvanized pipe (or ordinary welded pipe) with nominal inner diameter, that is, the outer diameter is 26.9mm and the pipe wall thickness is 2.45 ~ 2.8mm.

Because 1 inch = 25.4mm; Then 3 / 4 inch = 19.05mm.

The nominal outer diameter of 3 / 4 "water pipe is 26.8mm, with a tolerance of plus or minus 0.5mm. The wall thickness of ordinary pipe is 2.75mm, and that of thickened pipe is 3.5mm. The nominal diameter is 20mm.

As a new type of water pipe material, it can be used as both cold pipe and hot pipe. It is becoming a popular material because of its non-toxic, light weight, pressure resistance and corrosion resistance. It is also applicable to hot water pipelines and even pure drinking water pipelines.

We have a large inventory of a full range of galvanized steel pipes. If you need to purchase galvanized steel pipe, please contact us.

The expression of galvanized steel pipe diameter shall comply with the following provisions:

1) The pipe diameter of water gas transmission steel pipe (galvanized or non Galvanized), cast iron pipe and other pipes should be expressed by nominal diameter DN;

2) The diameter of seamless steel pipe, welded steel pipe (straight seam or spiral seam), copper pipe, stainless steel pipe and other pipes should be the outer diameter × Wall thickness representation;

3) The pipe diameter of reinforced concrete (or concrete) pipe, clay pipe, acid resistant ceramic pipe, cylinder tile pipe and other pipes should be expressed by inner diameter D;

4) For plastic pipes, the pipe diameter should be expressed according to the method of product standard;

5) When the nominal diameter DN is used to represent the pipe diameter of galvanized steel pipes, there shall be a comparison table between the nominal diameter DN and the corresponding product specifications.

Hot dip galvanized pipe, in order to improve the corrosion resistance of steel pipe, general steel pipe is galvanized. Galvanized steel pipes are divided into hot-dip galvanizing and electro galvanizing. The hot-dip galvanizing layer is thick, the cost of electro galvanizing is low, and the surface is not very smooth.

Nominal wall thickness: mm2 0、2.5、2.8、3.2、3.5、3.8、4.0、4.5；

Coefficient: C1 064、1.051、1.045、1.040、1.036、1.034、1.032、1.028。

Inner diameter ft: 1 / 2, 3 / 4, 1, 1.25, 1.5, 2, 2.5, 3, 4, 5, 6, 8 ,10, 12, 20

Note: the mechanical property of steel is an important index to ensure the final service performance (mechanical property) of steel, which depends on the chemical composition and heat treatment system of steel. In the steel pipe standard, according to different application requirements, the tensile properties (tensile strength, yield strength or yield point, elongation), hardness and toughness indexes, as well as the high and low temperature properties required by users are specified. Grade of galvanized pipe steel: q215a; Q215B； Q235A； Q235B

Test pressure value / MPA: D10 3Mpa for 2-168.3mm; D177. 8-323.9mm is 5MPa

Galvanized   steel pipe sizes and   specifications list

This is the size and specification comparison table of galvanized steel pipe. You should use this form when choosing galvanized steel pipe.

Galvanized steel pipe is divided into cold galvanized pipe and hot-dip galvanized pipe. 

The former has been banned, and the latter is also advocated by the state.

Hot dip galvanized pipe

Hot dip galvanized pipe is to make molten metal react with iron matrix to produce alloy layer, so as to combine the matrix and coating. Hot dip galvanizing is to pickle the steel pipe first. In order to remove iron oxide on the surface of the steel pipe, after pickling, it is cleaned in ammonium chloride or zinc chloride aqueous solution or ammonium chloride and zinc chloride mixed aqueous solution tank, and then sent to the hot dip galvanizing tank.

Hot dip galvanizing has the advantages of uniform coating, strong adhesion and long service life. Complex physical and chemical reactions take place between the steel pipe matrix and the molten plating solution to form a corrosion-resistant zinc ferroalloy layer with compact structure. The alloy layer is integrated with the pure zinc layer and the steel pipe matrix. Therefore, it has strong corrosion resistance.

1. Uniformity of zinc coating: the steel pipe sample shall be immersed in copper sulfate solution for 5 times without turning red (copper plating color)

2. Surface quality: the surface of galvanized steel pipe shall have a complete galvanized layer, without black spots and bubbles, and small rough surfaces and local zinc nodules are allowed.

3. Weight of galvanized layer: according to the requirements of the demander, the weight of galvanized steel pipe can be measured, and its average value shall not be less than 500g / m2, and any sample shall not be less than 480g / m2.

Cold galvanized pipe

Cold galvanizing is electro galvanizing. The amount of galvanizing is very small, only 10-50g / m2. Its corrosion resistance is much different from that of hot-dip galvanized pipe. In order to ensure the quality, most regular galvanized pipe manufacturers do not use electro galvanizing (cold plating).

Only those small enterprises with small scale and outdated equipment adopt electro galvanizing, and of course, their price is relatively cheap. At present, the Ministry of construction has officially eliminated cold galvanized pipes with backward technology, and it is not allowed to use cold galvanized pipes as water and gas pipes in the future.

The zinc layer is an electroplating layer, which is separated from the steel pipe matrix. The zinc layer is thin, and the zinc layer is simply attached to the steel pipe matrix, which is easy to fall off. Its corrosion resistance is poor. In newly-built houses, it is forbidden to use cold galvanized steel pipes as water supply pipes.

Precautions for purchasing galvanized steel pipe

1 Burrs on galvanized steel pipe wall

A. Burrs appear before galvanizing.

Prevention: when the goods arrive at the factory, the quality department must be present for inspection and indicate that there is no burr on the self inspection sheet. In addition, negotiate with the quality department to determine the proportion within which goods can be received if there are burrs.

B. The steel pipe has burrs after pickling or galvanizing.

Treatment measures: after finding the burr of galvanized steel pipe, pull the same batch of materials to the galvanizing plant designated by the supplier for pickling and galvanizing. During this period, the management and processing department and the quality department must accompany them. If they do not go, it is deemed that there is no problem in the processing process and no objection to the processing results. If there is no problem in the second treatment, it indicates that it is not a pipe quality problem. Our department will send a letter to suggest the production department to assess the galvanizing process of the original galvanizing plant.

2 Wrinkles occur when the galvanized steel pipe bends.

First of all, the operation process should be agreed with the galvanized steel pipe processing workshop. What kind of galvanized pipe must be cold bent, what kind of pipe must be hot bent, what galvanized steel pipe must be filled with sand, and what size of mandrel corresponds to what size of pipe. The operation must be standardized. For example, the wrinkles caused by non-standard operation will not be solved by our department.

Secondly, the wrinkle of one pipe cannot be used to prove that the whole batch of pipes have quality problems. Several more pipes must be tested according to the operation specifications to obtain the results. If the proportion of problem materials is very low (within%), no quality objection will be raised.

3 Galvanized steel pipe wall is too thick or too thin

At present, steel pipe procurement is adjusted. As long as the lower difference is controlled within the scope of the national standard, there should be no phenomenon of too thick or too thin wall thickness. When receiving the goods, let the quality inspection department spot check with a caliper to prevent it.

4 Galvanized steel pipe rusted.

Spot pipes inevitably have rust, but they must be polished before use. If there is no burr or depression beyond the scope of the national standard after polishing, it does not belong to the quality objection.

five Procurement scope and qualification of galvanized steel pipe factory.

It is necessary to confirm that the galvanized steel pipe manufacturer has this qualification before signing the contract.