Is A Seamless Steel Pipe Stronger Than Welded?

In the fields of industry and construction, seamless steel pipe and welded steel pipe are two common pipes. They have significant differences in manufacturing process, strength, corrosion resistance and application scenarios. So, which is stronger, seamless or welded?

Strength of seamless steel pipes

Seamless steel pipes are tubular products made from a whole piece of metal material through processes such as perforation, rolling or drawing. Since there is no weld, the material of seamless steel pipes is more uniform, which makes them perform well when subjected to high pressure, high temperature and complex stress environments. The tensile strength of seamless steel pipes is usually more than 8-10 times that of ordinary steel, so they are widely used in industries with high strength requirements such as oil, natural gas, and chemicals.

Strength of welded steel pipes

Welded pipes are tubular products made by welding steel plates or strips after curling and forming. Although modern welding technology has been able to ensure that the quality of welds reaches a high standard, under extreme conditions, the welds are still the weak link of welded pipes. The national standard yield strength of welded steel pipes is between 370MPa and 500MPa. Although this value is lower than the tensile strength of seamless steel pipes, it is still sufficient for use in many application scenarios.

Strength comparison and practical application

Since seamless steel pipes do not have defects such as welds and heat-affected zones during the manufacturing process, their strength is generally higher than that of welded steel pipes.

1. Seamless steel pipes

The experimental results show that the bearing capacity of seamless steel pipes of the same size is 20% to 25% higher than that of welded steel pipes. This makes seamless steel pipes have a wider range of applications under working conditions of high pressure, high temperature and harsh environments. For example, in industries such as petroleum, chemical, and electric power, key components such as boiler tube often uses seamless steel pipe, which are favored for their high strength and good corrosion resistance.

2. Welded steel pipes

In contrast, although welded steel pipes have lower strength, their manufacturing cost is relatively low, and they still have certain application value in some occasions where strength requirements are not high. For example, in the construction field, welded steel pipes are often used to build bridges and high-rise buildings; in the mechanical field, they can be used to manufacture machinery and equipment, conveyor belts, etc.

Reasons for strength differences

This strength difference mainly stems from the manufacturing process and material structure of the two.

1. Seamless steel pipe

Seamless steel pipe is a tubular metal material made by hot rolling, cold drawing or cold rolling of solid round bars. Its inner and outer walls are smooth and bright, without obvious short cracks, ripples and other defects. This manufacturing process makes the material structure of seamless steel pipes more compact and has higher safety and reliability.

2. Welded steel pipe

Welded steel pipe is made by arc welding, high-frequency welding and other welding methods after the steel plate is curled into a tube. During the welding process, defects such as welds, heat-affected zones and internal stress may occur, which will affect its strength to a certain extent.

Summary and selection suggestions

In summary, there are obvious differences in strength between seamless steel pipes and welded steel pipes. Seamless steel pipes have a wider range of applications in harsh environments such as high pressure and high temperature due to their high strength and good corrosion resistance; while welded steel pipes are used in some occasions where strength requirements are not high due to their economic advantages. When selecting pipes, the advantages and disadvantages of both should be considered comprehensively based on actual needs and the use environment.

Read more: Seamless Steel Pipe Sizes