Galvanized Seamless Steel Pipe

1.What is galvanized seamless steel pipe?

The most popular products on the market are welded pipes, galvanized pipes, square tubes, spiral pipes and seamless pipes. The circulation of galvanized seamless steel pipes is very small, and they are generally produced on order. So are you familiar with galvanized seamless steel pipes? Galvanized seamless steel pipe is a steel pipe product with superb manufacturing technology. It is made of high-quality carbon steel or alloy steel materials through a series of processing processes to make seamless steel pipes, and then galvanized on the surface. Galvanizing is an important method to protect the surface of steel. By covering the surface of the steel pipe with a zinc layer, the steel pipe can be effectively prevented from being damaged by oxidation, corrosion, and corrosion. Therefore, seamless galvanized steel pipes have the advantages of corrosion resistance, wear resistance, pressure resistance, and long service life.

2.What is the "galvanizing" in galvanized seamless pipes?

Hot-dip galvanizing is also called hot-dip galvanizing and hot-dip galvanizing: it is an effective way to prevent metal corrosion, mainly used in metal structural facilities in various industries. It is to immerse the rust-removed steel parts in a zinc solution melted at about 500℃, so that a zinc layer adheres to the surface of the steel components, thereby achieving the purpose of corrosion protection. Hot-dip galvanizing process: finished product pickling-water washing-adding auxiliary plating solution-drying-hanging plating-cooling-chemical-cleaning-polishing-hot-dip galvanizing is completed.

3.How to distinguish the authenticity of galvanized seamless pipes?

Now there is a so-called hot-dip galvanized fluid pipe on the market, also called de-galvanized seamless pipe, which is actually a processed high-frequency welded pipe. The original weld is planed or ground off with special equipment and then galvanized. Now I will share the identification method with you:

(1) Anything that is planed or ground off will leave traces, and some are very obvious;

(2) Hot-dip galvanized seamless steel pipes are all fixed in length of 6 meters, 9 meters or 12 meters. Genuine hot-dip galvanized seamless steel pipes are very rare because they have to be priced much higher when they are shipped out of the factory;

(3) Manufacturers of such pipes are afraid of taking responsibility, so their quality certificates are all fluid pipes and they dare not say they are seamless steel pipes;

(4) Check whether the wall thickness is uniform. Since seamless steel pipes are made of round steel hot-rolled and perforated, the wall thickness of seamless steel pipes will generally have deviations (with the continuous improvement of technology, the wall thickness deviation of seamless steel pipes is getting smaller and smaller, but there are still some). Although welded pipes have undergone welding rib treatment or heat expansion procedures, since their raw materials are strip steel, their wall thickness is very uniform.

The gray blocks of varying sizes on the surface of galvanized seamless steel pipes are galvanizing color differences, which is a problem in the current galvanizing industry. It is mainly related to the trace elements contained in the steel pipe itself and the components in the zinc tank. The color spots do not affect the anti-corrosion performance of the steel pipe, but are only aesthetic differences. There is a gradually obvious protruding mark on the surface of each galvanized seamless steel pipe, which is all zinc. After the galvanized seamless pipe is taken out of the zinc pot, the zinc liquid flows down the pipe wall and then cools and solidifies. Each galvanized seamless pipe has a trace of polishing and spraying near both ends. The seamless pipe must be fixed on a special steel frame during hot-dip galvanizing and immersed in zinc liquid together with the steel frame. After the galvanizing is completed, scars will be left at the fixing point.

For the sake of beauty, the area will be polished and zinc sprayed. Some customers will use grooved links to press grooves on seamless pipes when using galvanized seamless steel pipes. Since the zinc layer of hot-dip galvanized seamless pipes is thicker, under the action of destructive external forces, some of the galvanized layers will crack and peel off, which has nothing to do with the quality of the galvanized seamless steel pipes themselves. Some customers will report that there is yellow liquid on the galvanized seamless steel pipe (this liquid is called passivation liquid), which can make the metal surface passive. It is generally used for post-plating treatment of galvanizing, cadmium plating and other coatings. The purpose is to form a surface state on the surface of the coating that can prevent the normal reaction of the metal, improve its corrosion resistance, and increase the beauty of the product. It can effectively improve the corrosion resistance of the steel pipe and extend the service life of the workpiece.

4.Standards for galvanized seamless steel pipes:

The hot-dip galvanizing standard refers to GB/T13912-2002, technical requirements for hot-dip galvanized layers of steel parts and metal coverings.

Seamless pipe thickness

>1.5mm, the average thickness is not less than 45цm;

At 1.5-3mm, the average thickness is not less than 55цm;

At 3-6mm, the average thickness is not less than 70цm;

≥6mm, the average thickness is not less than 85цm;

Note: This table is a general requirement. Specific product standards may include various requirements including different thickness grades and classifications. In the absence of conflict with this standard, thicker coating requirements and other requirements can be added.

The main method for measuring coating thickness is a magnetic thickness gauge, which does not damage the surface of the product being measured, is easy to use, and is currently the most widely used method.

5.Application of galvanized seamless steel pipe

Galvanized seamless steel pipe is widely used in construction, bridges, petroleum, chemical industry, electric power, metallurgy and other fields, and is often used as a pipe for conveying fluids such as water, gas, and oil. Due to its high quality and durability, it has been favored by many industries. The manufacturing process of galvanized seamless steel pipe is very complicated and requires multiple processes, including hot rolling, cold drawing, pickling, cleaning, galvanizing and other links. Due to the characteristics of seamless steel pipe itself, it has high strength, high toughness and dimensional accuracy, and its galvanizing treatment is more perfect and uniform.

6.Summary

In short, the production process of galvanized seamless steel pipe is relatively complicated, and it needs to be strictly implemented in accordance with the process flow to produce reliable quality products. In the future, with the continuous upgrading and optimization of related technologies, the production process of galvanized seamless steel pipe will also be continuously optimized and improved to meet the continuous needs of the market.