1. Different outer surfaces
It can be seen from the outer surface of the seamless steel pipe that there is no gap in the whole body; the welded steel pipe has a welding gap.
2. Different molding process
Seamless steel pipes
are perforated from a whole round steel, and the steel pipes without welds on the surface are called seamless steel pipes.
Welded steel pipes are steel pipes made of steel plates or strips that are crimped and welded. The length is generally 6 meters and there are welds on the surface. Welded steel pipes have simple production process, high production efficiency, many varieties and specifications, and low equipment investment, but their general strength is lower than seamless steel pipes.
3. Different categories
Seamless steel pipes: According to different production methods, they are divided into hot-rolled pipes, cold-rolled pipes, cold-drawn pipes, extruded pipes, and jacking pipes, all with their own process regulations.
Welded pipes: Divided into general welded pipes, galvanized welded pipes, oxygen-blowing welded pipes, wire casings, metric welded pipes, roller pipes, deep well pump pipes, automotive pipes, transformer pipes, electric welded thin-walled pipes, electric welded special-shaped pipes, scaffolding pipes and spirals Welded pipe.
4. Different physical properties
Seamless steel pipes are often used in high-pressure equipment because of their better carrying capacity than ordinary steel pipes. Such as hydraulic equipment, pipe connections, etc. The welding position of ordinary steel pipe is the weak link, and the quality of the weld is the main factor affecting its comprehensive performance. The physical properties of seamless steel pipes are better than those of welded pipes, and their compression resistance is higher. The welded pipes are generally about 10 MPa. Now welded pipes are seamlessly treated.
5. Different prices
The price of seamless steel pipes is generally higher than that of welded steel pipes.
6. Different uses
Seamless steel pipes are generally used in factories; welded steel pipes are generally used in construction.
Seamless steel pipes are widely used. General-purpose seamless steel pipes are rolled by ordinary carbon structural steel, low-alloy structural steel or alloy structural steel, and have the largest output. They are mainly used as pipelines or structural parts for conveying fluids, such as petroleum geological drilling pipes and cracking for petrochemicals. Tubes, boiler tubes, bearing tubes and high-precision structural steel tubes for automobiles, tractors, and aviation.
Welded pipes are widely used in water supply engineering, petrochemical industry, chemical industry, power industry, agricultural irrigation, and urban construction.
Welded pipes are used for liquid transportation: water supply and drainage. Used for gas transportation: coal gas, steam, liquefied petroleum gas; used for structure: used as piling pipes, pipes for bridges, piers, roads, building structures, etc.
Development history: Since the 1930s, with the rapid development of high-quality strip continuous rolling production and the advancement of welding and inspection technology, the quality of welds has been continuously improved, and the variety and specifications of welded steel pipes have increased day by day. Instead of seamless steel pipes.
Welded steel pipes are divided into straight seam welded pipes
and spiral welded pipes
according to the form of welds. Longitudinal welded pipe has simple production process, high production efficiency, low cost, and rapid development; spiral welded pipe generally has higher strength than longitudinal welded pipe, and can produce welded pipes with larger diameters from narrower blanks, and also can use blanks with the same width We produce welded pipes with different pipe diameters.
Compared with the straight seam pipe of the same length, the weld length is increased by 30~100%, and the production speed is lower. Therefore, most of the smaller diameter welded pipes adopt straight seam welding, and the large diameter welded pipes mostly adopt spiral welding.