ASTM A53 Thick Wall Seamless Steel Pipe Crack

1. ASTM A53 thick-walled seamless steel pipe hot rolling position were from the steel head 38,118m, mainly in the middle of the strip. 
2. It is speculated that the gap starts at the middle of the width of the strip, because the rolling force and shear force in the rolling process cause the gap to be stretched to form a macroscopic macropore.
3. Seamless carbon steel pipe in the cold rolling production process interrupted with the fracture surface smooth, no obvious before and after fracture surface defects. 
The microstructure of the fracture was observed, and the typical ductile ductile fracture morphology was observed. At the same time, the fracture was layered, the central dimple was larger, the dimple was narrowed near the surface, and the crack appeared the center fracture And the depth of fracture at the center is deep, and it is presumed that the stratified topography is closely related to the central segregation.

ASTM A53 thick-walled seamless steel pipe analysis:
1. Under the scanning electron microscope, the surface morphology of the hot-rolled and cold-rolled steel pipe was observed, and the crack was observed in the middle of the fracture.
2. The results show that there are obvious oxidized particles in the vicinity of the crack, and there is a complete polygonal ferrite morphology near the crack in the crack and near the crack. 
3. The characteristics of the oxidized particles in the 30um near the crack are closely related to the original defects of the continuous casting billet. The continuous casting slab is heated in the heating furnace for a long time to cause the elements near the crack to be oxidized to form a thicker oxide layer. Inherited to the last volume.
4. The results show that there are obvious cracks and oxidation zones of structural steel pipe in the center of thickness and 1/4, and there are also oxidized particles near the crack.