Firstly, the concentricity varies. The manufacturing process of seamless pipes involves forming holes in stainless steel billets below 2200 degrees Celsius through pressing. Under this high-temperature effect, tool steel becomes soft and then spirals out from the holes. The wall thickness of these pipes is simple and uneven, with a relatively high degree of distortion. Seamless pipes are made from precision cold-rolled sheets. The wall thickness variation of these sheets is generally around 0.002 inches, resulting in minimal wall thickness variation and a very uniform wall thickness throughout the pipe.
The differences between 304 stainless steel seamless and welded pipes also include welding properties. Generally, the chemical composition of welded pipes and seamless pipes varies. The steel used to produce seamless pipes just meets the basic requirements, whereas welded pipes contain chemical components suitable for welding, such as silicon, sulfur, manganese, oxygen, and martensite. If these elements are missing, simple welding integrity may form during the welding process.
The size of metal particles is related to the temperature and duration of heat treatment. After annealing, the particle size of both seamless and welded pipes is the same. If cold-treated seamless pipes are chosen, the particle size after welding is significantly smaller than that of the welding metal, otherwise, the sizes are identical.
The difference between seamless and welded stainless steel tubes also includes corrosion resistance. Corrosion resistance also depends on the composition of the alloy. Tubes with the same chemical composition, whether seamless or hot-rolled welded, have equal corrosion resistance. Welded steel tubes that have not been fully heat-treated will simply corrode.
Both are priced differently; generally, the price of welded steel pipes is even less than half that of seamless steel pipes, making them quite affordable.
In fact, when both are compared, welded steel pipes are gaining more and more advantages over seamless steel pipes. Since welded steel pipes have passed a series of inspections and are made from cold-rolled sheets, all their drawbacks are limited to the welding site. Seamless steel pipes are formed by stamping stainless steel billets, which can lead to wall tearing during the extrusion process. Moreover, tests show that in most cases, the pass rate of defective products in welded steel pipes will be lower than that in seamless steel pipes. Additionally, under ultrasonic testing, the background noise of seamless steel pipes is relatively high, making it difficult to detect defects, whereas the opposite is true for welded steel pipes.
