The seamless steel pipe is made of perforated whole round steel, and the steel pipe without weld seam on the surface is called seamless steel pipe. According to the production method, seamless steel pipes can be divided into hot-rolled seamless steel pipes, cold-rolled seamless steel pipes, cold-drawn seamless steel pipes, extruded seamless steel 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 900mm and the minimum diameter is 4mm. According to different uses, there are thick-walled seamless steel pipes and thin-walled seamless steel pipes. 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.

1. Different nature
 
1. Seamless steel pipe: a steel pipe made of a single piece of metal without seams on the surface.
 
2. Welded steel pipe: a steel pipe with a seam on the surface that is formed by bending and deforming a steel strip or steel plate into a circular, square or other shape and then welded.
 
Second, the characteristics are different
 
1. Seamless steel pipe: the maximum diameter is 650mm, and the minimum diameter is 0.3mm. Depending on the application, there are thick-walled and thin-walled tubes.
 
2. Welded steel pipe: When the T-shaped welded steel pipe contains Ni, it has strong corrosion resistance in an acidic environment. In an environment containing sulfuric acid or hydrochloric acid, the higher the Ni content in the T-shaped welded steel pipe, the stronger the corrosion resistance. Under normal circumstances, only adding Cr to the T-shaped welded steel pipe can prevent the phenomenon of corrosion.
 
Three, the effect is different
 
1. Seamless steel pipe: Seamless steel pipe is mainly used as petroleum geological drilling pipe, cracking pipe for petrochemical industry, boiler pipe, bearing pipe and high-precision structural steel pipe for automobile, tractor and aviation.
 
2. Welded steel pipes: electric welded steel pipes are used in oil drilling and machinery manufacturing, etc.; furnace welded pipes can be used as water gas pipes, etc., large-diameter straight seam welded pipes are used for high-pressure oil and gas transportation, etc.; spiral welded pipes are used for oil and gas transportation, pipe piles, bridge piers, etc. .