Selection Guide: Stainless Steel Seamless Pipe vs Welded Pipe

Overview of stainless steel pipe

Stainless steel shines in level instrumentation and many industries with its excellent comprehensive performance and attractive appearance surface characteristics. Similarly, stainless steel pipes have also attracted much attention. Stainless steel pipes, as a hollow cross-section steel, are usually divided into two categories: stainless steel seamless pipes and welded pipes. But what is the difference between the two? How should we choose in specific applications?

Characteristics of stainless steel seamless pipes

Stainless steel seamless pipes, a hollow cross-section steel, are widely used in many fields with their excellent performance. In the level instrumentation industry, it has become the preferred material for key components. In industrial equipment such as drill pipes and octg pipes, seamless steel pipes are also popular for their strong pressure resistance and reliable connection.

Characteristics of stainless steel welded pipes

Stainless steel welded pipes are formed by curling steel plates or steel strips under the joint action of the unit and the mold, and then welded. There is usually a weld seam on the inner wall of the pipe, which is one of the main differences between it and seamless pipes. The seamless pipe is made of round pipe billet and is made through fine processes such as cold rolling, cold drawing or hot extrusion. There are no welding marks on the pipe.

Differences and selections

1. Differences in manufacturing process

Stainless steel welded pipes are made by bending steel plates into pipe shapes, and then fusing the edges into pipe bodies through welding technology.

Stainless steel seamless pipes are formed by multi-processing of solid round steel bars without gaps. The manufacturing process of stainless steel seamless pipes is more complicated, so the price is higher.

2. Differences in the appearance of steel pipes

Stainless steel welded pipes have uniform wall thickness and high brightness. They can be sized arbitrarily according to needs, and even thin-walled pipes can be produced.

In contrast, the steel pipe precision of stainless steel seamless pipes is relatively low, the wall thickness is unevenly distributed, and the brightness of the inner and outer surfaces of the pipes is also low.

In addition, the cost of sizing when producing seamless pipes is high, and the pitting and black spots that may exist on the inner and outer surfaces are difficult to remove. Therefore, the wall thickness of conventionally produced seamless pipes is often thicker. Applications with higher pressure requirements, such as boiler tubes and heat exchanger tubes, usually use higher strength seamless steel pipes.

3. Performance and price differences

The corrosion resistance, pressure resistance and high temperature resistance of seamless pipes are much higher than those of stainless steel welded pipes. With the improvement of the production process of stainless steel welded pipes, the mechanical properties and mechanical properties are gradually approaching those of seamless pipes, and welded pipes can replace seamless pipes in some aspects.

In general, the chemical composition of stainless steel welded pipes and seamless pipes is somewhat different. The steel composition of seamless pipes just meets the basic requirements, while stainless steel welded pipes contain chemical compositions suitable for welding, such as silicon, sulfur, manganese, oxygen and delta ferrite. If these elements are missing, the welding process will be very difficult.

The relatively high price of seamless pipes reflects their high quality and high cost. Due to their superior performance, seamless pipes are more suitable for extreme conditions such as high temperature and high pressure.

Selection points

Given the unique characteristics and differences between stainless steel seamless pipes and welded pipes, in practical applications, in order to achieve economical, beautiful and reliable results, we need to comprehensively consider the following key factors to make a reasonable choice:

1. In applications where good surface effects are required, such as decorative pipes, product pipes or prop pipes, stainless steel welded pipes are usually recommended.

2. For low-pressure fluid transportation, such as water, oil, gas, air, and heating hot water or steam, stainless steel welded pipes are a suitable choice.

3. If the fluid needs to be transported in industrial engineering or large equipment, or works in high temperature and high pressure environments such as power plants and nuclear power plant boilers, stainless steel seamless pipes should be selected to ensure durability and strength.

4. Stainless steel welded pipes are mainly suitable for liquid transportation below 0.8MPa, while seamless pipes can withstand higher pressures. In situations where pressure requirements are not high, welded pipes are usually more economical.

Read more: Seamless Steel Pipe Sizes or ERW vs seamless pipe in weight calculation