• 61-pictures of common defects in strip steel

1 Irregular Shells

【Appearance characteristics】 The thin strips on the surface of the strip are folded. The defects often appear gray and white. They have different sizes and shapes and are irregularly distributed on the strip surface.
【Cause(s)] There are non-metallic inclusions on the surface or subsurface of the slab. These inclusions are broken or exposed during the rolling process to form a sandwich fold.
【Inspection】 Visual inspection, steel plate and strip must not have sandwich.

2 Seams

[Appearance characteristics] The inclusions on the strip surface of the strip are irregularly distributed along the rolling direction in the form of lines or strips, and sometimes disappear gradually in spots or tongues.
【Cause(s) of origin] The inclusions in the slab sub-surface are severely stretched and cracked during rolling.
【Inspection】 Visual inspection, steel plate and strip must not have sandwich.

3 Blisters

【Appearance characteristics】 There is gas in the convex surface of the strip steel, and there is no regular distribution, and there are points of closed bubbles and open bubbles.

[Causes] Slabs, due to the large amount of gas that cannot be released during the solidification process, are enclosed inside and form gas inclusions. During hot rolling, voids and holes are elongated, and as the thickness of the rolled material is reduced, it is brought to the surface or edge of the product. Ultimately, high gas pressure causes dome-shaped projections or extrudates on the surface or edges of the product.
[Examination] Visual inspection, steel plates and strips must not have bubbles.

4 Scabs

[Appearance characteristics] Irregular tongue, fish scale, strip or M-shaped metal flakes are distributed on the strip surface. One is connected with the strip steel matrix; the other is not connected with the strip steel matrix, but bonded to the surface, easy to fall off, after the fall off to form a relatively smooth pit.
【Cause(s)] Due to scabs and burrs on the surface of the slab, it remains on the surface of the strip after rolling. After the slab is cleaned by flame, it is left with residue and pressed into the surface during rolling.
[Examination] Visual inspection, steel plates and strips must not have scars.

5 Split layer

[Appearance characteristics] The unrepresented gaps appear on the section of the steel strip. Occasionally visible inclusions are found in the gaps on the strip. Severe stratification results in partial spalling of the steel sheet and the location of the delamination is irregular.
【Causes of Origin】 The local accumulation of excessive gas or non-metallic inclusions in the slab can not be welded during the rolling process; severe segregation of chemical components can also form delamination.
[Examination] In visual inspection, there must be no stratification of steel plates and strips.

6 Spills

【Appearance characteristics】 The skin often has tongue, line, layer or M-fold (discontinuous, thin material often appear tilted), often appear on the edge of the upper surface of the strip.
[Causes] Pinholes, bubbles, and inclusions near the inner surface of the billet are easily exposed at the edges (weak places) on the upper surface of the strip during the rolling process, and part of the surface during the rewinding process or coiling process. Tiered peeling caused by tilting defects.
[Examination] According to the standard and the use requirements, perform the [Check].

7 Spills

[Appearance characteristics] The arrow-shaped micro-folds of different sizes appear discontinuously on any of the upper and lower surfaces, often appearing on the edges of the strip.
[Causes to be Caused] Tears or cracks are caused by the oxidation of heat and hot rolling into the grain boundaries. It mainly occurs in stainless steel, acid-resistant steel, and heat-resistant steel, especially in non-stable austenitic steels.
[Examination and judgment] Plates and strips are generally allowed to have fins whose depth or height does not exceed half of the thickness tolerance.

8 Edge cracks

[Appearance characteristics] The edge of the strip is cracked along one or both sides of the length direction. There are obvious metal droppings and cracks, and serious ones are serrated.
[Causes to be Caused] Edge cracks are likely to occur in the slab rolling process. Due to poor roll adjustment, improper roll shape, or low edge temperatures, cracking may occur during rolling because of poor elongation and may also occur in the cooling process. A further reason for the formation of such defects is that local areas of the material edges are stressed beyond its strength limit.
【Inspection】 Visual inspection, steel plate and strip must not have edge cracks.

9  Burnt edges

[Appearance characteristics] Cracks and cracks appearing along the edge of the strip, which may appear on the entire length of one or both sides of the strip.
[Cause] Inappropriate heating conditions such as excessive heating temperature, long heating time, and partial heating may cause such defects, and may also be related to excessive sulfur content.
[Examination] Inspected by naked eye, steel plates and strips must not be overheated.

10 Split strip edges

[Appearance characteristics] Longitudinal cracks along the strip edge.
[Causes] Due to cracks in the edge of the slab, sometimes from the flame cutting edge of the slab, it appears in the center segregation zone.
[Examination] Check the judgment according to the standard and the use requirements.

11 Pores

【Appearance characteristics】 It is a small gas inclusion near the surface of the billet. According to the degree of deformation, these small gas inclusions are elongated during the rolling process and expose the surface. In the hot strip, the pores are usually descaled. Appears in the form of light stripes.
[Causes to occur] Steel is formed during the casting and solidification process due to high gas content. Sometimes the pores can be oxidized and filled with iron oxide skin. According to different steel grades, a certain degree of decarburization may be caused when the billet is heated.
[Examination] Check the judgment according to the standard and the use requirements.

12 Rolled-inscale

【Appearance characteristics】It is a kind of defect that the iron oxide skin presses into the surface of the steel strip. Usually it is small spots, fish scales, strips, blocks irregularly distributed on the whole or part of the upper and lower surfaces of the steel strip, often accompanied by rough Hemp surface. Some loose and easy to fall off, and some pressed into the board surface, after pickling or sandblasting, there are different degrees of pits. According to the different defects generated by the process can be divided into a primary iron oxide press and secondary iron oxide press.
【Cause(s) The reason that the primary iron oxide skin is pressed in is due to the fact that the iron oxide skin of the slab itself is severe or that the slab is heated to generate a severe scale of iron oxide. It is not removed before the rough rolling and is pressed into the surface of the slab during rolling. The secondary iron oxide skin press is formed by pressing the secondary scale into the surface of the strip steel during finish rolling. Due to the large unit pressure, the hot rolled strip is more likely to have such defects.
[Examination and Judgment] The steel plate and the steel strip must not be pressed into the iron oxide skin. Generally, there is a thin layer of iron oxide skin that is slightly and locally not more than half of the thickness tolerance

13 Rolling dust

[Appearance characteristics] The powdered iron oxide skin is pressed into the surface of the strip steel, which is mainly generated on the upper surface of the strip steel, and may be irregularly distributed or may occur on the lower surface.
[Causes] The main cause is the rear part of the finish rolling, which is caused by the dispersed distribution on the surface of the strip or the intrusion of agglomerated powdered iron oxide skin.
[Examination and Judgment] The steel plate and the steel strip must not be pressed into the iron oxide skin. Generally, there is a thin layer of iron oxide skin that is slightly and locally not more than half of the thickness tolerance.

14 Pitting

[Appearance characteristics] The surface of the strip has a partial or continuous rough surface and is orange peel-like when severe. Both on the upper and lower surfaces, uneven density in the entire length of the strip can occur.
【Cause(s)] When the roll temperature is relatively high, the scale is adhered to the roll and the surface of the plate is punctured during rolling. Roller material is bad or the temperature is high and wear is serious. There may also be pitting on the board surface during rolling.
[Examination] Check the judgment according to the standard and the use requirements.

15 Roll marks

[Appearance characteristics] The surface of the steel sheet has a bit-like shape, and the periodic projections and pits of the sheet or strip are distributed over the entire length of the strip or a section thereof.
【Cause(s)] The periodic bulging is caused by the damage of the work roll or the tension roll; the periodic cratering is caused by the convex point formed by the work roll or the transfer roll stuck with the foreign matter. According to the defect cycle length, the cause and location of the defect can be determined. Depending on the degree and the reason, these defects may be flattened in the subsequent process, which may or may not entrain the scale.
[Inspection judgment] According to the standard and the use request different inspection judgments, it is generally allowed to have partial imperfections whose depth or height does not exceed half of the thickness tolerance.

16 Crazing

【Appearance characteristics】 A discontinuous crack on the surface of the rolling piece, which is centered at a certain point and diverges outwards in a lightning-like manner. According to the degree of extension and broadening, the area affected is usually elliptical (initially circular). Cracks may also be present in very small microcracks or hairline forms.
[Causes to occur] When the grain boundary is weakened by a low-melting phase (such as hot brittleness), cracking occurs when deformed.
[Examination] Inspected by naked eye, the steel plate and strip must not be cracked.

17 M-defects

[Appearance characteristics] Similar to the M-shaped tongue-like defects in the sandwich, it appears in the form of ablation in the hot strip, which may appear on both the upper and lower surfaces.
【Cause(s)] Due to over-grinding of coarse slabs or due to the incomplete removal of the oxide scale formed during the heating of the billets, the grooves are abraded to form M-shaped defects of varying degrees. M-type defects mainly occur in molybdenum-containing stainless steels, acid-resistant steels, and heat-resistant steels, especially in stabilized austenitic steels.
[Examination] Check the judgment according to the standard and the use requirements.

18 Massive ruptures

【Appearance characteristics】 Through the local cracks on the upper and lower surfaces of the strip, there is no regular or discontinuous distribution on the strip surface.
[Cause] The plastic deformation is too large and the local stress of the material is too large. Excessive local stress on the material is usually caused by defects such as cracks, voids, slag inclusions or rough indentations. In addition, changes in the rolling geometry, surface mechanical damage, etc. can also lead to cracking.
[Examination] Inspected by naked eye, the steel plate and the strip must not be cracked.

19 Laps

[Appearance characteristics] Irregular surface materials overlap, may be linear, tongue or lamellar, or may be M-shaped, and may appear on different parts of the surface of the rolled material.
【Cause(s)] The initial defects such as slab surface cracks, scratches on the bottom surface of the slab caused by a push-type heating furnace, or damage to the surface caused by other causes may undergo overpressure during the subsequent rolling process and form a fold. . In addition, it is also possible that the edge material flows unevenly during rolling (possibly overlapping to the surface) or the slab edge is not properly deformed, the roll configuration is unreasonable, and the rolls lose meat.
[Examination] Visual inspection, steel plates and strips must not be folded.

 

20  Fold

【Appearance characteristics】 A wrinkle-like overlap, often occurring at the end of the strip.
[Causes] The strip tail flicks during rolling because of a change in the roll shape, an excessively large bend in the rolled boring bar entering the finish rolling, or an excessively long irregular tail portion.
[Inspection] Visual inspection, steel plates and strips must not have wrinkles, defects should be removed.

21 Scratches, grooves and gouges

[Appearance characteristics] The mechanical damage on the surface of rolling stock varies in length, width, and depth. Mainly in the rolling direction or perpendicular to the rolling direction, it may be slightly flattened, and may contain iron oxide skin or expose the inner metal. The scratches under high temperature have a thin layer of iron oxide skin and appear dark gray; the scratches at room temperature show metallic luster or grayish white.
[Cause] The friction occurs due to the relative motion of the rolling parts and mechanical equipment components. Longitudinal defects are produced when the strip is conveyed on the roller conveyor or when it is taken up and uncoiled; transverse defects are mainly generated when the steel plate moves laterally or when the coil is unwound from the coiler. Wiping scratches may also occur due to relative movement between layers of unwound rolls. If the rolling stock is damaged at high temperatures, a scale of iron oxide is created in the damaged area and pressed in subsequent processes, depending on where it is generated. Chips will be generated when scratched, or material buildup will occur near or at the end of the scratch.
[Inspection judgment] According to the standard and the use request inspection judgment, normally does not exceed half of the thickness tolerance.

22 Damaged strip edges

[Appearance characteristics] The sides of the tape roll are scratched to varying degrees, sometimes accompanied by curled flashes or fine chips.
[Causes to occur] The strip edge is generated due to the strong contact between the strip edge and the entrance guard.
[Inspection judgment] According to the standard and use requirements, it is judged that the general lateral depth does not exceed half of the width deviation.

23 Folded strip edges

【Appearance characteristics】 Some protruding bands have a defect in the form of thickening, curling, or mechanical damage.
【Cause(s)] Due to over-correction or improper winding of the side guides during stripping or transfer, some strip layers protrude, and are formed by contact damage during handling, transportation, and storage of the strip.
[Inspection judgment] According to the standard and use requirements, it is judged that the general lateral depth does not exceed half of the width deviation.

24 Sheared edge defects

[Appearance characteristics] The dart-shaped material that has been cut from the cutting edge, cutting flash edge, and shear crack is broken, and forms an angle of about 45 degrees with the plate.
【Cause(s)] Caused by incorrect setting of blade clearance, wear of the shear blade, and chipping or other damage. High-strength steels and wear-resistant steels are particularly prone to such defects.
[Checking judgment] Check the judgment according to the standard and usage requirements.

25 Rough edges

[Appearance characteristics] The roughness along the entire length of the strip or the edges of the upper and lower sides of the strip is increased to a certain degree, and it is clearly legible after pickling or sandblasting.
[Causes] Due to the high roll load in the edge region of the strip, the roughness of the roll increases and the edge of the strip is roughened. Such defects mainly appear in stainless steel and heat-resistant and acid-resistant steels.
[Checking judgment] Check the judgment according to the standard and usage requirements.

26 Strip folds

【Appearance characteristics】 A kind of wrinkle or bend, appearing on the entire width of the strip at right angles or oblique directions to the rolling direction.
【Cause(s)] During the strip rolling process, if excessive looping occurs in the finishing train, the looper will be rolled into overlapping when the strip passes through the next frame; if the strip forms a looper on the output roller path Or wrinkles, it will be followed by the belt in the coiler flattened and entrained into the coil.
[Examination and judgment] The steel strip must not overlap, and the local part should be removed.

27 Coil breaks

[Appearance characteristics] The transverse folds perpendicular to the rolling direction run across the strip at regular or irregular intervals, or at the edges of the strip.
[Cause] The result of local yielding of the strip in the direction of motion during the unwinding process. The geometric design of the reels, bending rolls, or guide rolls, as well as the thickness and temperature of the strip, have an important influence on the formation of the cross-stamping. High yield elongation, especially with low yield strength, tends to increase significantly. Since the yield and strain processes are time dependent, the tendency to produce horizontal folds at higher strip unwinding speeds decreases. This defect usually occurs when the tension is too high to exceed the material’s yield limit and is not equipped with a cross-printing system.
[Checking judgment] Check the judgment according to the standard and usage requirements.

28 Coil cone
【Appearance characteristics】The end of the coil is pagoda-shaped and bread-like.
[Causes] Improper adjustment of the rolling mill caused the rolled steel strip to be bent by a guillotine or improperly adjusted by the coiler.
[Examination] The tower height is measured and judged according to the standard.

29 Loose coils

[Appearance characteristics] The strip coil is not tight and there is a large gap or loosening between the coil and the ring.
[Cause] The coiling tension is small, the coiling temperature is low, and the bandage is broken or the hardness of the steel is high.
[Check judgment] Judging according to the standard and use requirements.

30 bright band (convex ribs)
[Appearance characteristics] The surface of the steel coil was linearly thickened locally. The bright band was observed with the naked eye, and the ribs were touched by hand.
[Causes] The work roll cooling water nozzle is blocked, causing local roll shape problems; due to unreasonable rolling schedules or unfavorable hardness of the finish rolling work rolls, the roll surface wears excessively; the local temperature of the strip steel is low.
[Checking judgment] Measurement with naked eye or micrometer, check and judge according to the standard and use requirements.

31 Seams

[Definition and Characteristics] After strip pickling, the surface of the steel plate shows irregular landscapes with clear boundaries.
【cause】
The effect of local phosphorus removal in the phosphorus removal section during hot rolling is not good.
[Prevention and Correction] During the hot rolling production process, the flow and pressure of phosphorus removal water are ensured, so that the surface of the iron oxide skin can be completely removed.
[Identification and judgment] Can be judged by the naked eye, not easily confused with other defects.

32 Scar
[Definition and Characteristics] Gravure due to improper transport or storage, it can be penetrated by a few turns of steel, similar to the periodicity.
【cause】
Steel coils are in contact with hard objects in the environment during transport and storage.
[Prevention and Correction] Keep the environment clean during transportation and storage.
[Identification and judgment] Can be judged by the naked eye, if the cycle is easy to be confused with roller printing.

33 Outside tower

[Definition and Characteristics] Steel coil inner diameter or outer diameter multilayer or a layer of steel strip is coiled unevenly to one side.
【cause】
After stripping due to loss of tension, the strip rolled to the outer diameter of the coil due to pressure roller pressure is not tight; coil volume unloading core diameter pulling core or outer diameter and unloading roll cart due to sliding.
[Prevention and Correction] Before the production, confirm the compaction degree of the pressure roller and perform the production after meeting the requirements; strengthen the operation when unloading the volume and reduce the occurrence frequency of the core pulling core.
[Identification and judgment] Can be judged by the naked eye, not easily confused with other defects.

34 Rust

[Definition and Characteristics] The metal surface is damaged by oxidation in a specific environment such as air or water. Diffusion from the edge of the strip to the middle, red, showing a dot.
【Cause Analysis】
Steel coils will produce such corrosion in the case that the coils are stored over time or the humidity in the field is large.
[Prevention and Correction] Control the placement time of coils in the yard and ensure the temperature and humidity of the yard.
[Identification and judgment] It can be judged with the naked eye.

35 Support roller imprints

[Definition and Characteristics] It is an invisible mark on the surface of the steel plate that is visible after polishing.
【Cause Analysis】
Foreign objects stick to each roller surface or guide plate that is in contact with the strip. When the strip passes, an imprint is produced.
[Prevention and Correction] Periodically clean the roller system in contact with the surface of the steel plate.
[Identification and judgment] Visual inspection or whetstone grinding inspection is not easily confused with other defects. It is generally judged visually and polished.

36 Damage strip edges

[Definition and Characteristics] Damage to the edge of the strip causes a lack of meat on the edges.
【Cause Analysis】
During the production process, the edge of the strip steel collides with the equipment or causes damage during the lifting due to coiling or misalignment of the strip.
[Prevention and Correction] Tower-shaped and overflow sides are generated during controlled rolling to control the deviation of strip during production.
[Identification and judgment] It is generally judged visually.

37 Bad tension reel

[Definition and Characteristics] Is uneven on both sides of the coil
【Cause Analysis】
Winding failures or poor incoming plate shapes, as well as unsteady tension, can cause coiling towers.
[Prevention and Correction] Adjust the take-up tension while keeping the tension stable.
[Identification and judgment] The naked eye is easy to judge. Not easily confused with other defects.

38 Flat coil

[Definition and Characteristics] The shape of the coil is obviously not circular and elliptical.
【Cause Analysis】
When the take-up tension is small or the force is applied when it is placed, it will produce a flat roll, which occurs in a thin material.
[Prevention and Correction] Increase the take-up tension; when the coil is placed, the principle of narrow, light, thick and heavy is applied.
[Identification and judgment] It is generally judged visually.

39 Under pickled

[Definition and Characteristics] The surface of the steel strip is left with unwashed iron oxide skin, which is a horizontal black stripe (like a “black-and-white pattern” of “head-up lines”), and is formed in a strip or sheet on the surface of the steel plate. Touch it with black dirt on your hand.
【cause】
After the tropical surface of the iron oxide skin has been cleaned by the pickling tank, it is not cleaned and remains on the strip surface.
[Prevention and Correction] 1, to ensure that the head and tail picking speed.
2, to ensure that the acid temperature within the control range, the amount of acid injection of more than 60% of the set value.
3, pull straightening unit normal input.
[Identification and judgment] Can be judged by the naked eye, not easily confused with other defects.

40 Over pickled

[Definition and Characteristics] The surface of the steel strip is rougher than that of the normal pickled steel plate, and the color is not silver white, but appears dark black or brownish black.
【Cause Analysis】
In the pickling line, if the acid temperature is too high or the strip running speed is too low, the hot-rolled strip matrix reacts with the acid and overwash occurs.
[Prevention and Correction] 1, to prevent the pickling speed is too slow.
2. Reduce abnormal parking and parking time in the process section.
[Identification and judgment] Can be judged by the naked eye, not easily confused with other defects.

41 Emulsionmarks

[Definition and Characteristics] It is a cracked emulsion that remains on the surface of the strip and is randomly distributed on the surface of the strip. The shape is irregular and the color is dark. After a long time, the color turns yellow and the color becomes black after annealing.
【Cause Analysis】
Emulsion cracking occurs because the residual emulsion in the annealing process is not completely evaporated. That is, the excess emulsion on the strip is not blown.
[Prevention and Correction] 1. Reduce 5 blowouts.
2. The 5 outlet rack pipes are wrapped with cloth to prevent dripping of condensation emulsion onto the steel plate.
[Identification and judgment] Can be judged by the naked eye, not easily confused with other defects.

 

42 More flesh and lack of meat on the edges
[Definition and Characteristics] After cutting the steel strip through the disc, the edges of the strip show a lack of flesh and meat due to poor cutting.
【cause】
Disc cutter shear edge aging or shear edge collapse due to.
[Prevention and Correction] The state of the shear edge of the disc shear is ensured during the production process.
[Identification and judgment] Can be judged by the naked eye, not easily confused with other defects.

43 Freckles on the surface
[Definition and Characteristics] The surface of the strip shows a patch or a large area of traces. In some cases there is evidence of outward radiation at a certain angle.
【cause】
The temperature of the pickling section and the rinsing section is too high and the strip running speed is too slow.
[Prevention and Correction] The temperature and speed of the process section are well matched to avoid slow speed and high temperature.

44 Waves

[Definition and Characteristics] It is a steel plate that is not straight and has a wavy curve with high and low undulations along the rolling direction. According to the distribution of different parts, can be divided into unilateral waves, bilateral waves, waves and two waves.
【Cause Analysis】
Along the width direction of the strip, the extension of the middle and the extension of the edge are inconsistent, resulting in wave-shaped defects.
[Prevention and Correction] 1. Correctly select the original crown of the work roll.
2, the correct use of positive and negative bending roller.
3, the correct use of roller coolant.
4, control the incoming board shape and board convexity.

45 Shearededge defect

[Definition and Characteristics] The strip is cut through a disc and shows a small saw-tooth-type slit at the edge of the strip.
【Cause Analysis】
The blunt or notch of the disc shearing blade or the clearance of the shearing blade and the amount of overlap were not adjusted well, and a burr occurred after the shearing.
[Prevention and Correction] 1. Ensure that the cutting edge is of good quality.
2, to prevent cutting edge clearance, reconciliation error.

46 Stoppagemarks

[Definition and Characteristics] The parking spot is when the pickling line is stopped, and large spots of chemical stains form on the surface of the strip. Can be distributed anywhere in the strip.
【Cause Analysis】
In the pickling line, the stop marks may occur because the parking time causes the strip to stay in the pickling tank and the processing tank for too long.
[Prevention and Correction] Reducing the stoppage of the pickling section and eliminating it by starting the car after the stoppage.

47 Chatter marks

[Definition and Characteristics] It is irregularly corrugated and can be distributed along the entire width of the strip along the rolling direction. The strip thickness changes in the rolling direction.
【Cause Analysis】
The tremors are characterized by thickness fluctuations which are generated by resonance of the gantry.
[Prevention and Correction] It is forbidden for the unit to use eccentric and heavily worn support rollers to prevent frame vibration; when the frame vibration is large, the rolling speed is reduced.
[Identification and judgment] Judging by naked eyes or after grinding, it is not easy to be confused with other defects.

48 grinding mark

[Definition and Characteristics] They are regular strips and can be distributed across the width of the strip along the rolling direction, parallel to the rolling direction.
【Cause Analysis】
In the case of roll grinding, the infeed marks are generated in the circumferential direction of the roll. Under the action of the rolling force, longitudinal stripes are formed on the surface of the strip.
[Prevention and Correction] Uniform roller grinding procedure, fixing the Z-axis speed of each grinding machine, controlling the roughness of light roller, avoiding lap printing and diagonal printing on the roller surface after grinding, and grinding and checking the edge of the roller.
[Identification and judgment] Judging by naked eyes or after grinding, it is not easy to be confused with other defects.

49 Emulsion marks

[Definition and Characteristics] It is a cracked emulsion that remains on the surface of steel strips and is randomly distributed on the surface of the steel strip. The shape is irregular and the color is dark.
【Cause Analysis】
Emulsion marks are the emulsions that remain on the surface of the steel strip. The residual emulsion is completely evaporated during the annealing process. That is, the excess emulsion on the strip is not blown.
[Prevention and Correction] Ensure the outlet angle and pressure at the exit of the mill and avoid the condensation of the emulsion at the exit of the mill.
[Identification and judgment] Can be judged by the naked eye, not easily confused with other defects.

50 Black band

[Definition and Characteristics] The black film on the surface of the steel sheet is longitudinally distributed in strips or sheets, with different strip widths and different shades of color.
【Cause Analysis】
After rolling, residual emulsion on the strip surface, at the same time, the coiling tension of the rolling mill is too large, and the emulsion residue in the center portion of the coil is not easily volatilized, and oxidation or carburization occurs during the placement.
[Prevention and Correction] Control the emulsion concentration, the viscosity of the emulsifiable concentrate, ensure the blowing angle and pressure at the outlet of the mill, and avoid excessive rolling tension in the rolling mill.
[Identification and judgment] Can be judged by the naked eye, not easily confused with other defects.

51 Emulsion marks

[Definition and Characteristics] There are black or brown marks of varying sizes on the surface of the strip, and there are generally obvious contours.
【Cause Analysis】
The oil spot is the residual oil content in the emulsified liquid on the strip surface. During the placing process, a small amount of oil is volatilized and taken away by the air. A large amount of oil penetrates into the surface of the strip to form iron oxide and causes scars.
[Prevention and Correction] Control equipment leakage between racks, timely and accurate adjustment after oil leakage; ensure the rack is clean and prevent emulsion smoke from dripping.
[Identification and judgment] Can be judged by the naked eye, easily confused with rust.

52 Clean emulsion marks

[Definition and Characteristics] After washing the unit, the cleaning liquid remaining on the surface of the steel strip is in a sheet or line state. It is not obvious before annealing and appears white or black traces after annealing.
【Cause Analysis】
1, brush roller or squeeze roller failure.
2. The conductivity of the rinsing section is high.
3, the dryer temperature is low.
[Prevention and Correction] 1, when the brush roller can not meet the requirements of the regulations, timely replacement.
2, when the squeeze roller roll surface appears serious wear or peeling when replaced.
3. Guarantee the conductivity of brushing tank and rinsing tank.
4, to ensure that the dryer temperature reaches the regulatory requirements.
[Identification and judgment] Can be judged by the naked eye, not easily confused with other defects.

53 Anneal-stained edges

[Definition and Characteristics] The yellow or blue traces appearing on the surface of the steel strip after annealing of the cold-rolled strip are S-shaped at the edge of the strip after annealing in the bell-type furnace.
【cause】
Gas leakage or water in the protective cover, or early release.
[Prevention and Correction] 1, before the spot furnace inner cover test leak before heating.
2, the process checks prevent early release.
3, the emergence of emergency cleaning after the reduction process.
[Identification and judgment] Can be judged by the naked eye, not easily confused with other defects.

54 Color aberration

[Definition and Characteristics] The brightness of the surface of the strip along the longitudinal direction is obviously different from that of other parts, and there is a clear boundary.
【cause】
The chemical composition of raw materials, rolling emulsion residue, annealing process, furnace atmosphere and other factors all cause the surface color of the steel strip to be uneven.
[Prevention and Correction] 1, reduce the steel surface residue.
2, improve the grinding process.
[Identification and judgment] Can be judged by the naked eye, not easily confused with other defects.

55 Chattermarks

[Definition and Characteristics] It is irregularly corrugated and can be distributed along the entire width of the strip along the rolling direction. The strip thickness changes in the rolling direction.
【cause】
The tremors are characterized by thickness fluctuations which are generated by resonance of the gantry.
[Prevention and Correction] 1. Strictly implement the roll change system.
2. Reduce rack clearance and reduce rack vibration.
3, improve the rolling precision, reduce the thickness fluctuations.
4, improve the quality of roller grinding.
[Identification and judgment] Judging by naked eyes or after grinding, it is not easy to be confused with other defects.

56 Feather after SPM

[Definition and Characteristics] Feather patterns produced during the leveling process are distributed locally or throughout the strip.
【cause】
Due to the uneven extension of the strip in the roll gap.
[Prevention and Correction] 1, increase the tension before and after.
2, improve the incoming plate shape.
3, increase bending or roll curve.
4, increase the height of anti-crease roller.
[Identification and judgment] Judging by naked eyes, it is not easy to be confused with other defects.

57 Rustafter SPM

[Definition and Characteristics] The metal surface is damaged by oxidation in a specific environment such as air or water. In the edge of a continuous strip or intermittent lumpy rust, yellow, with a touch, there is a clear black border after wiping.
【cause】
The leveling agent does not have a uniform concentration or there is excessive residual leveling fluid at the edge.
[Prevention and Correction] 1. Improve storage conditions in the reservoir area.
2. Increase the concentration of the leveling fluid to maintain it within the process standards; check the quality of the purge equipment and compressed air to keep it in good condition.
3. Always check the nozzle of the oiler to keep it open.
4, improve the quality of packaging.
[Identification and judgment] Can be judged by the naked eye, not easily confused with other defects.

58 Feather

[Definition and Characteristics] Feather patterns produced during the leveling process are distributed locally or throughout the strip.
【cause】
Due to the uneven extension of the strip in the roll gap.
[Prevention and Correction] 1. Reasonably adjust the pressure and adjust the waves on one side in time.
2. Put the anti-crease roll into work in time to ensure that there is tension behind it.
3, a reasonable choice of roller crown, and the correct use of positive and negative bending roller.
[Identification and judgment] Judging by naked eyes, it is not easy to be confused with other defects.

59 Coilbreaks

[Definition and Characteristics] In the edge of the strip (a small number also occurs in a certain part of the middle of the steel sheet), a line of equal signs appears continuously. On the edge of the steel plate, the lengths of the lines are different, vertical or at an angle of 45 degrees to the plate rolling direction.
【cause】
Local yield occurs in the unwinding direction when unwinding. Reel and strip thickness have a great influence on the creation of cross folds. Cross-stamping occurs most easily in the case of high elongation and low yield strength. Because the stress-strain process is time-dependent, high decoiling speeds can reduce the occurrence of cross-stamping.
[Prevention and Correction] 1, appropriate to reduce the tension.
2. Reduce the original crown of the work roll.
3, the correct use of positive and negative bending roller.
4, adjust the plate type.
[Identification and judgment] The naked eye can determine that it is not easy to be confused with other defects.

60 Oilcoating odd

[Definition and Characteristics] The surface of the steel sheet is partially coated with anti-embroidered oil in a ribbon shape, which is consistent with the rolling direction.
【cause】
Partial blockage of jet knife beam of oiler
[Prevention and Correction] 1. Clean the oiler.
2, cleaning knife.
3, ensure the voltage.
4, to ensure the oil temperature.
5, anti-rust oil cleanliness level 8 or more.
[Identification and judgment] Can be judged by the naked eye, not easily confused with other defects…

61 the back up roll mark

[Definition and Characteristics] The regular light and dark stripes along the rolling direction of the steel plate are generally visually invisible to the hand and have a severe feel.
[cause] Due to the residual dirt on the surface of the steel plate, it sticks to the work roll when passing through the straightening machine; it has mechanical residual oil when disassembling the straightening machine; when the straightening and rolling amount is large, the dirt or oil stain on the work roll is printed. To the steel plate.
[Prevention and Correction] 1. Ensure that the surface of the steel plate is clean with less residue.
2. Add the appropriate mechanical oil to the mechanical assembly.
3. Clean the straightener work rolls frequently.
4, reasonable pressure.
[Identification and judgment] Normally judged by naked eye, slight inspection can be combined with polishing.