Located on the inner surface of the steel pipe was vertical distribution, was raised helical, massive metal separation or break-like dissection.
Straight inner flap
Located on the inner surface of the steel pipe was vertical distribution, showing a symmetrical or a single line-shaped folded with through long, there are local.
Irregular hole
Located in the surface of the pipe was vertical distribution, ① has one or two walls 180 °out of thickening, or in the surface of the pipe and the wall thickness of the mandrel separation point has thickened shape, also known as the inner drum kit. ② steel inner garden was a hexagonal shaped uneven thickness, also called hexagon.
Wall contraction
Located on the inner surface of the steel pipe, steel transverse section thinnest steel pipe inner surface depressions, localized thinning of the wall thickness of the severe contraction almost tear.
Rolled scar
Longitudinal direction of the inner surface of steel nails like scarring, bumps or lumps folded inner pipe surface indentation.
Inside folding
Located at the inner surface of the end portion of the steel pipe, local or flaky longitudinal spiral or semi-spiral folding irregular distribution.
Rolling off
Located within the longitudinal surface of the pipe wall was a partial or full length in the outer concave or convex corrugations on the outer surface of the pipe through the long longitudinal grooves prescribe obvious symmetry, generally rectilinear, individual to slash shape.
Tear
Located on the tube longitudinal steel surface showed varying degrees of transverse rupture, diamond-shaped and oval-shaped hole through the tubular body.
Fold the double-slit
Located on the longitudinal surface of the pipe wall obliquely extending into a pair of longitudinal cracks, the cracks sometimes scattered distribution on the pipe circumference sometimes appear symmetrical.
Double centerfold
Located on the longitudinal surface of the pipe wall obliquely extending into a pair of longitudinal cracks, the cracks sometimes scattered distribution on the pipe circumference sometimes appear symmetrical.
Outer folding
① on the outer pipe presents regular folding triangle shaped, double-slit straight single slit straight or irregular sheet folded like.
② Presenting a generally continuous or intermittent stitch sewing machine-like or staggered 60 °, 120 °, 180 ° sewing stitch-shaped folded pipe in the longitudinal direction of the outer。
③ outer longitudinal folded on a spiral steel pipe.
④ a longitudinal direction of the pipe surface through long or short slash dot folded severe staggered two or three of 120 °.
