Terms of Steel Defect

In general, the most commonly encountered defects from semi-finished (billets, blooms, and slabs) and final (round bar and plate) steel products are network cracks, porosity, gas holes, shrinkage, shell, slivers, casting powder entrapment, ladle slag entrapment, other non-metallic inclusions, low hot ductility

Roundness: mainly for the circular cross-section rolled products, such as the cross section round and round steel pipe, unequal diameters in all directions. Terms of Steel

Defect (1)

Incorrect shapes: skew and uneven geometry of rolled cross-sectional. Such as the unequal-leg six-sided steel, large apex angle steel and section steel torsion.

Uneven thickness: steel (or strip) is not the same as the thickness of the various parts, some thick on both sides and thin in the middle, and some thick in the middle and thin at the edges, and some head and tail difference exceeds requirements.

Bending: rolling is not straight in length or width direction, showing curved.

Camber: steel plate (or steel) bent to one side in the longitudinal direction in the horizontal plane.

Scoop curvature: steel (or steel) undulating wave phenomenon occurs simultaneously in length and width directions, making it a "scoop-shaped" or "boat."

Reverse: strip rolled into a spiral twist along the longitudinal axis.

Off square, off rectangle: unequal opposite sides and cross-sectional diagonal line of square, rectangular section material. Terms of Steel Defect (2)

Scored(drawing stamp): shown linear gully, can be seen in the partial or full-length of the steel.

Cracks: general shown as linear shape, and sometimes Y-shaped, more consistent with the pulling direction, but there are other directions, the general opening as an acute angle.

Scarring: the surface is shown as curled tongue or scale piece of sheet: one is linked with the body of steel, and pressed to the surface and not easy to fall off; another is not linked with the body of steel, but stick close to the surface and is easy to fall off.

Folding: steel surface partially overlapping, with a clear fold lines.

Rust: rust formed on the surface, its color ranging from yellow to dark red, after the process of rust removal, there are serious corrosion pitting.

Hairline: the surface hairline is with shallow depth, small width, and tiny hair-like fine lines, generally extending along the rolling direction of the pattern and forming tiny thread.

Layering: a steel cross-section with a clear partial separation of the metal structure, is even divided into 2 to 3 layers, have visible inclusions between the layers. Terms of Steel

Defect (3)

Bubbles: Surface irregularly distributed large and small rounded convex hull, with relatively smooth outer edge. Most is plumped up, some do not muster and the surface shiny and smooth after pickling.

Pittings: surface showing partial or continuous pieces rough surface, distributing different shapes, different sizes of the pits, a similar serious orange peel-like, large and deep pitting spots.

Oxidation Color: steel plate (or steel strip) on the surface after annealing showing pale yellow, dark brown, light blue, dark blue or light gray and so on.

Roll printing:surface with strip or sheet periodically roll printing, which is lighter in the embossed parts, and there is no obvious bumping.

Loosening: the performance of no density steel. After the slices through the acid erosion, expanded into many caves which can be divided according to their distribution: general porosity, center porosity.

Segregation: the uneven distribution of chemical composition and non-metallic inclusions in the steel. According to its manifestations can be divided into: dendritic, box-shaped, point-like segregation and anti-segregation.
Residual shrinkage: in the center of the transverse acid leaching test pieces, showing irregular voids or cracks. Voids or cracks are often left with foreign impurities. Terms of

Steel Defect (4)

Nonmetallic inclusions: see some non-metallic luster gray, beige and dark gray and other colors in the transverse acid leaching test piece, which are oxides, sulfides, silicates remaining in the steel.

Metallic inclusions: see some metal salt with a metallic luster and is clearly different from the base metal in the low magnification transverse test piece.

Over burnt: when observing the microstructure eroded, the decarburization organizations can be often seen around the network-like base metal oxides, other metals such as copper and its alloys with copper oxide extending to the internal sample along the grain boundary or the network-like point .

White point: it is an internal rupture of steel. In the longitudinal fracture, steel parts are shown round or oval-shaped silver-white spots; in the horizontal slice through the polished and etched, shown as the thin hair crack, sometimes radially distributed, sometimes parallel to the deformation direction or randomly distributed.

Coarse grains: a strong metallic luster on the acid leaching test piece mouth.

Decarbonization: the phenomenon of sub-surface carbon content is lower than the inner layer is called decarbonization. Total decarburized layer refers to the ferrite structure portion due to the steel surface decarburization; part decarburization refers to after the total decarburization layer the area the carbon content of the steel does not decrease.

Weled steel pipe specification, Standard and identification

Welded steel pipe (steel pipe manufactured with a weld) is a tubular product made out of flat plates, known as skelp, that are formed, bent and prepared for welding.



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