Summary of Common Defect Types
1. Slit——Line-shaped defects on the full length of the steel coil within 20mm of the hot-rolled edges on both sides of the steel coil. The upper surface of Nisshin raw material has a wider defect on
the upper surface and a narrower surface on the lower surface. Therefore, the bottom surface of Nissin serves as the base level for cold-rolled single-sided guaranteed products.
2. Oxidation line There are linear defects on the surface of the material due to the residual oxides from rolling, which are similar to inclusion defects;
3. Warped skin (dropping of oxide skin)-tongue-shaped or fish-scale-shaped, some closed and open. There are large and small parts connected to the body.
4. Inclusions-there are obvious points, blocks, and long willow leaves.
5. Scribing-during processing, it can be seen that there are single or multiple but no-hand scratches on the surface of the material board;
6. Scratches-during processing, it can be seen that there are single or multiple strip-shaped dots on the surface of the material and scratches with a touch;
7. Bumps Material board surface produces large material deformation under the action of external force;
8. Interlayer slippage (double-sided slippage)-the same shape, small and dense scars occur on the symmetrical positions on both sides of the steel coil. Due to the loose roll between the board.
9. During processing, the surface of the board will produce small material deformation under the action of external force;
10. Paper indentation material deformation caused by paper wrinkles on the board surface during processing;
11. Burr-plastic deformation formed at the lower part of the fracture surface of the material during processing (the flat plate has one end up and one end down);
12. Collapse (corner collapse)-plastic bending deformation formed in the upper part of the material shearing bright band during processing;
13. Linear scaly folds surface defects of the steel coils are in a linear peeling state, some are covered by the film, and some are not.
14. Edge scaly folding-linear or mountain-like scaly peeling within 50 mm of the rolling edge of the steel coil, parallel to the rolling direction, and occurs continuously or intermittently.
15. Mountain-shaped scaly folding surface of the steel coil is a mountain-shaped spalling defect, and the location of occurrence has no characteristic, and the mountain-shaped direction is parallel to the rolling direction.
16. Hot-rolled head slippage-There are slippage scars on both sides of the hot-rolled coil head about 5 meters.
17. Oxide scale defects occur more head and tail on the bottom surface of the hot-rolled, and the material in the inside of the oblong shape is concave.
18. Stop roll mark a dent perpendicular to the rolling direction that occurs on the surface of the steel strip.
19. Smoothing roll marks the rolling direction of the steel plate, and the uneven scars produced with the circumference of the SPM work roll as the spacing.
20. Roller along the length of the steel plate, the uneven scars appearing with the perimeter of the CRM work roll as the spacing; middle roller marks and support roller marks: uneven marks that occur in a straight line without periodicity in the length direction
21. Edge wave-wave deformation on one or both sides of the steel coil
22. Caused by the biting of irregular debris that often occurs during hot rolling, and the location is not fixed
23. Pyrometer cooling water spots-there are white spots on the surface of the strip, and the color of the hollow part is the same as that of the strip.
24. Oxygen residue-the oxide scale is not fully removed, there are residues on the surface, and the defects are black and irregular oxides
25. White spots-white spots on the surface of the strip occur irregularly
26. Holes-holes that penetrate both the front and back of the steel coil, which occur more frequently in ferritic single-phase steel
27. Edge waves-the extension of one or two sides of the steel plate is greater than the extension in the middle, and the edges are uneven.
28. Cloud-like patterns-cloud-like patterns that occur on NI steel-grades
29. Pickling pattern-partial whitening or brown pattern caused by incomplete pickling, washing, and brushing
30. Herringbone pattern-Herringbone wave patterns appear symmetrically on both sides of the centerline of the steel plate and form a certain angle with the rolling direction.
31. Oil pattern-spot-like irregular pattern similar to the pattern on the surface of galvanized sheet, or raindrop-like pattern.
32. Pickling pattern residue-there are white and brown pattern residues on part or all of the surface of the strip
33. Oil film rupture defects developed from slip or rain, which occur on the surface of the strip.
34. Oil stains-wavy and whitish patterns that occur on both sides of the steel belt.
35. Edge damage (folding) (edge bump)-when the edge of the steel coil is severely bent, the angle is greater than 90 degrees and is accompanied by edge cracks
36. Delamination-Delamination means that the internal cracks of the material are generally difficult to identify. After entering the rolling mill, the strip will break and crack.
37. Intermediate waves (belly waves)-The extension of the middle of the strip is larger than the two sides, and there is a middle bulge.
38. Folding-partial double-layer rolling in
39. Edge cracks-There are zigzag cracks on the edges of the strip.
40. With welds-strip steel with welds41. Rust spots-yellowish brown spots on the surface of the strip
42. Pockmarks-there are partial or continuous rough surfaces on the surface of the strip. Some are in the shape of a concave orange peel and appear as small shiny pits under the light.
43. Carbonized edges (snake tracks)-black can not be wiped off, the chemical reaction of carbon and substrate is not tolerant of acid.
44. Chromatic aberration-the brightness of a certain part of the strip surface is obviously different in other parts, and there are obvious boundaries.
45. Flat coil (collapsed coil)-the appearance of the steel coil is obviously not round and flat.
Cold-rolled stainless steel strip (plate) has a gorgeous, smooth surface and good processing performance, and is widely used in various fields. Due to the complex process, many procedures, and long units in the manufacturing process of cold-rolled stainless steel strips, there are many types of rolls in contact with the strip steel during processing, and the defects in the raw materials may cause various Defects affecting surface quality. In order to find defects as soon as possible in the manufacturing process of stainless steel strips, accurately determine defects, and prevent and reduce the occurrence of defects, we summarize some common defects through practice.
The surface defects of cold-rolled stainless steel are divided into five categories according to their shape.
Namely: linear defects; point defects; shape defects; surface defects; and edge defects.
1. The linear defect occurs in a linear shape, and the ratio of the width to the length is 1:10 or more, and the length is longer. It includes slits, scaly folds at the edges, slippage of the hot-rolled head, oxide scale defects, scratches, and residual grinding meshes.
2. The point defect occurs in the form of dots, and the ratio of the width to the length is 1:10 or less, and the shorter length is the object. It includes pits, pyrometer cooling water spots, oxygen bites, oxygen residues, etc.
3. Shape defects are defects caused by poor deformation of the strip steel, which has different degrees of deformation in length and width. Including edge waves and deepening of ribs.
4. Surface defects are defects such as roughness, patterns, and wrinkles produced during the surface processing of strip steel. Mainly include pickling patterns, herringbone patterns, oil patterns, pickling pattern residue, oil film cracking, etc.