Year1
- 材质：
- Q345B
refers to the expansion of the straight seam steel pipe through diameter expansion technology to achieve the purpose required by the customer. There are two processes for straight seam steel pipes: double-sided submerged arc welding and high-frequency welding. Double-sided submerged arc welding can produce straight seam steel pipes with diameters up to about
. The pipe expansion we are talking about now mainly refers to high-frequency welded pipes. There are two reasons
One is that the production diameter of high-frequency welded pipes is relatively small, so it needs to be expanded
The other is that the mechanical properties of high-frequency welded pipes in all aspects are better than those of submerged arc welding. , and its welding is mainly through the fusion of the fluid of the pipe body itself, rather than through the welding wire, so the possibility of cracking during the thermal expansion is small. Standard for thermally expanded straight seam steel pipe
.
Straight seam pipe refers to a steel pipe in which the weld seam is parallel to the longitudinal direction of the steel pipe. It is also generally called straight seam welded pipe or straight seam steel pipe. Straight seam pipes are made by rolling long strips of steel strips of a certain specification through high-frequency welding units and using straight seam welding. The specifications of straight-seam pipes are expressed in nominal diameter. According to the wall thickness, they can be divided into two types: thin-walled straight-seam pipes and thick-walled straight-seam pipes. According to the shape, it can be divided into round, square or special-shaped tubes.
Material
QB
Specifications
*m
Technical indicators
Welding
Straight seam pipes generally use high-frequency welding. High-frequency welding is a kind of induction welding (or pressure contact welding). It does not require weld filler, has no welding spatter, and has a narrow welding heat-affected zone. , beautiful welding shape, good welding mechanical properties and other advantages, so it is widely used in the production of steel pipes. According to the principle of electromagnetic induction and the skin effect, proximity effect and eddy current thermal effect of AC charges in the conductor, the steel at the edge of the weld is locally heated to a molten state. After being squeezed by the roller, the butt weld is inter-crystal bonded, thereby achieving The purpose of welding is to form a strong straight seam after cooling.
Weld seam gap
The strip steel is fed into the welded pipe unit, and after being rolled by multiple rollers, the strip steel is gradually rolled up to form a circular shape with an opening gap. Shape the tube blank and adjust the reduction of the extrusion roller to control the weld gap to
~m
and make both ends of the weld flush. If the gap is too large, the proximity effect will be reduced, the eddy current heat will be insufficient, and the inter-crystal bonding of the weld will be poor, resulting in lack of fusion or cracking. If the gap is too small, the proximity effect will increase and the welding heat will be too high, causing the weld to burn or form a deep pit after extrusion and rolling, affecting the surface quality of the weld.
Welding temperature
Made of low carbon steel, the welding temperature is controlled at
~
℃, which can meet the pipe wall thickness
~m
Welding penetration requirements. The welding temperature is mainly controlled by adjusting the high-frequency eddy current thermal power and welding speed. When the input heat is insufficient, the heated weld edge cannot reach the welding temperature, and the metal structure remains solid, resulting in incomplete fusion or incomplete welding. When the input heat is too large, the heated weld edge exceeds the welding temperature, resulting in excessive Burn or droplets will form a molten hole in the weld.
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