Seamless vs Welded Stainless Steel Pipe

What is a Seamless Stainless Steel Pipe?

A seamless stainless steel pipe is manufactured without any welding seam. It is produced by extruding a solid billet of steel into a hollow cylinder, typically using hot rolling or cold drawing methods.
Key Characteristics:
No weld seam
Uniform structure and strength throughout

Often preferred for high-pressure or high-temperature applications

Welded Stainless Steel Pipe

A welded stainless steel pipe is manufactured by rolling stainless steel strips or plates into a cylindrical shape and welding the edges together using techniques such as Electric Resistance Welding (ERW), Tungsten Inert Gas (TIG) welding, or laser welding. Depending on the finishing process, the weld seam may be visible or ground smooth for a more uniform appearance. Welded pipes are generally more cost-effective than seamless ones and are widely used in applications where extreme pressure or stress is not a concern. Their affordability and availability make them a popular choice for structural, decorative, and low-pressure systems.

The difference between seamless stainless steel pipe and welded stainless steel pipe

Stainless steel pipe is an economical cross-section steel material and an important product in the steel industry. It can be widely used in life decoration and industry. Many people on the market use it to make stair handrails, window guards, railings, furniture, etc. There are two common materials: 201 and 304. It accounts for about 8% to 16% of the total steel volume, and its application range in the national economy is extremely wide. Stainless steel is divided into two categories according to the production method: seamless pipe and welded pipe. So what is the difference between the two?

1. The difference in appearance

The most direct difference between seamless stainless steel pipe and welded stainless steel pipe is the appearance. The length of seamless pipe is basically inconsistent, while the length of stainless steel welded pipe is basically fixed. The surface of stainless steel welded pipe is basically mirror-like, while the surface of stainless steel seamless pipe is gray-white.

2. The difference in process

Stainless steel seamless pipe is a long steel strip with a hollow cross-section and no seams around it. The thicker the wall thickness of the product, the more economical and practical it is. The thinner the wall thickness, the higher the processing cost will be. The process of the product determines its limited performance. It uses round tube billets as raw materials for perforation and is made by cold rolling, cold drawing or hot extrusion. There are no welding points on the tube. Generally, seamless steel pipes have low precision: uneven wall thickness, low brightness of the inner and outer surfaces of the tube, high cost of fixed length, and pitting and black spots on the inner and outer surfaces are not easy to remove; its detection and shaping must be processed offline. Therefore, it has demonstrated its superiority in high pressure, high strength, and mechanical structural materials.

Welded steel pipes are referred to as welded pipes. They are usually made of steel or steel strips that are welded after being curled and formed by units and molds. The production process of welded steel pipes is simple, the production efficiency is high, there are many varieties and specifications, and the equipment investment is small, but the general strength is lower than that of seamless steel pipes. Since the 1930s, with the rapid development of high-quality strip steel continuous rolling production 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 increased, and they have replaced seamless steel pipes in more and more fields, especially in heat exchange spare pipes, decorative pipes, medium and low pressure fluid pipes, etc.

3. Differences in performance and price

Seamless pipes are much higher than welded pipes in corrosion resistance and pressure and high temperature resistance. With the improvement of welded pipe manufacturing technology, the mechanical properties and mechanical properties are gradually approaching seamless pipes. Seamless pipes are more complicated in manufacturing technology, and their prices are more expensive than welded pipes.

Based on the characteristics and differences between seamless stainless steel pipes and welded pipes, reasonable selection should be made when applying them to achieve economic, beautiful and reliable effects:

(1) When used as decorative pipes, product pipes, and prop pipes, good surface effects are generally required, and stainless steel welded pipes are usually selected;

(2) For generally low-pressure fluid transportation, such as water, oil, gas, air, and low-pressure systems such as heating hot water or steam, stainless steel welded pipes are usually selected;

(3) For pipelines used to transport fluids in industrial engineering and large equipment, as well as pipelines for transporting fluids in power plants and nuclear power plant boilers that require high temperature, high pressure, and high strength, stainless steel seamless pipes should be selected;

(4) Stainless steel welded pipes are generally used for liquid transportation below 0.8MPa, and seamless pipes can be used to withstand liquid transportation above 0.8MPa. If the pressure requirement is not high, it will be more economical to use welded pipes.