What is the difference between seamless pipe and welded pipe?

Xino Steel
Nov/21/2022

Steel pipe is a relatively common pipe material. It can be divided into different types such as seamless pipe and welded pipe. So what is the difference between seamless pipe and welded pipe? Next, I will briefly introduce to you.


Seamless steel pipe

A steel pipe made of a single piece of metal without seams on the surface is called a seamless steel pipe. According to the production method, seamless pipes are divided into hot-rolled pipes, cold-rolled pipes, cold-drawn pipes, extruded pipes, and pipe jacking. According to the cross-sectional shape, the seamless steel pipe is divided into two types: round and special-shaped. The maximum diameter is 650mm and the minimum diameter is 0.3mm. Depending on the application, there are thick-walled and thin-walled tubes. Seamless steel pipes are mainly used as petroleum geological drilling pipes, cracking pipes for petrochemicals, boiler pipes, bearing pipes and high-precision structural steel pipes for automobiles, tractors and aviation.

Welded steel pipe

Welded pipe, also known as welded steel pipe, is basically a steel pipe made of steel plate or strip steel after crimping and welding. Welded steel pipe has a simple production process, high production efficiency, many varieties and specifications, and less equipment, but its general strength is lower than that of seamless steel pipes. Since the 1930s, with the rapid development of continuous rolling production of high-quality strip steel and the advancement of welding and inspection technology, the quality of welds has been continuously improved, the varieties and specifications of welded steel pipes have been increasing, and more and more fields have replaced non-ferrous steel.

Welded steel pipes are divided into straight seam welded pipes and spiral welded pipes according to the form of the weld. The production process of the straight seam welded pipe is simple, the production efficiency is high, the cost is low, and the development is fast; the strength of the spiral welded pipe is generally higher than that of the straight seam welded pipe. Production of welded pipes with different diameters.

Compared with the same length of straight seam pipe, the length of the weld is increased by 30~100%, and the production speed is lower. Therefore, most of the welded pipes with smaller diameters use straight seam welding, and most of the welded pipes with large diameters use spiral welding.

What is the difference between seamless pipe and welded pipe?

1. Different process

Welded pipes are made by bending steel plates or strips through cold rolling and high frequency welding. Generally, there are spiral welding and straight welding. Seamless tubes are made by perforating billets or solid tube blanks, hot-rolled or cold-rolled. Seamless steel pipes are formed in one pass during rolling.

Ordinary welded steel pipes, such as water pipes, are generally welded by bending flat plates, and you can find a weld on it; the thicker diameter is generally a spiral weld. The seamless steel pipe is generally formed by pressing the molten steel in the molten state through the annular slit and then forming it by stretching and other processing processes, so that there is no weld.

2. Different appearances

The seamless steel pipe is rolled once and formed, the surface has no seams, and the performance is good. The inner wall of the welded pipe has welding ribs, and the surface generally has welding seams. Note: Now the welded pipe is seamless, and the traces can be seen by careful observation.

3. Different wall thickness

The precision of seamless steel pipe is low, and the wall thickness is relatively thick. The steel pipe of the welded pipe has high precision, and the wall thickness is usually relatively thin.

4. Different pressures

The welded pipe is generally about 10 MPa, and the pressure of the seamless pipe is higher.

5. Different raw materials

The seamless steel pipe uses steel billets or solid tube blanks. The seamless steel pipes are made of ordinary and high-quality carbon structural steel (Q215-A~Q275-A and 10~50 steel), low alloy steel (09MnV, 16Mn, etc.), Alloy steel, stainless acid-resistant steel, etc.; the welded pipe uses steel plate or strip steel.

6. Different performances

In terms of corrosion resistance, pressure bearing, high temperature resistance and other properties, seamless steel pipes are better than welded pipes.

7. Different prices 

In the case of the same specification, seamless steel pipes are more expensive than welded pipes because the production process of seamless steel pipes is more complicated and its cost is higher.

8. Different functions

Seamless steel pipes are generally used as fluid pipelines that require special environments such as high pressure resistance and high temperature resistance. Welded pipes are usually used as low pressure fluid delivery pipes.

9. Different application scenarios

Seamless steel pipes are mainly used as petroleum geological drilling pipes, cracking pipes for petrochemical industries, boiler pipes, bearing pipes and high-precision structural steel pipes for automobiles, tractors and aviation.

Welded pipes are widely used in tap water engineering, petrochemical industry, chemical industry, electric power industry, agricultural irrigation, and urban construction.

Welded pipes are used for liquid transportation: water supply and drainage. For gas transportation: gas, steam, liquefied petroleum gas; for structure: for piling pipe, for bridge; for wharf, road, building structure, etc.

Conclusion

What is the difference between seamless pipe and welded pipe, I will briefly introduce it to you today. I hope that after reading this article, I can provide you with reference and help. For more information, you can continue to pay attention to our website.


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