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Summary Of Common Problems In Hot Rolled Steel

Hot-rolled steel includes hot-rolled steel coils, hot-rolled steel sheets, and hot-rolled steel strips. Hot rolled steel refers to undergoing a hot rolling process at a high temperature. Hot-rolled steel supplies you with high strength, and good weldability, easy to process. Hot-rolled steel is widely used in construction, machinery, automobile, shipbuilding, petrochemical, and other industries.

Hot Rolled Steel Coils

Hot Rolled Steel Coils

Hot Rolled Steel Strip

Hot Rolled Steel Strip

Hot Rolled Steel Sheet

Hot Rolled Steel Sheet

Common Problems In Hot Rolled Steel

1. Roller printing defects

Defect characteristics: It is a group of concave and convex defects with periodic, basically the same size and shape, and the appearance and shape are irregular.

Cause:

  • On the one hand, due to the fatigue of the roller or the hardness is not enough, a part of the roller surface is concave, and on the other hand, there may be foreign bodies on the surface of the roller, so that the surface part is convex.
  • When rolling or finishing, press into the surface of the steel plate to form concave and convex defects.

2. Surface inclusion

Defect characteristics: There are irregular spot-like, block-like, or strip-like nonmetallic inclusions on the surface of the steel plate, and its color is generally reddish-brown, yellow-brown, grayish-white, or grayish-black.

Cause:

  • The slab is exposed after subcutaneous inclusion rolling, or the original surface of the slab remains on the surface of the steel plate after inclusion rolling.
  • Non-metallic materials such as refractory materials and sediment in the heating furnace fall on the slab surface and are pressed into the slab surface during rolling.
HR Steel Surface Inclusion

HR Steel Surface Inclusion

3. Iron oxide

Defect characteristics: The oxide sheet is generally adhered to the surface of the steel plate, distributed on the surface of the local or all, black or reddish-brown; Some iron sheets lose off, and some pressed into the plate surface do not easily fall off; According to the appearance of different shapes: red iron sheet, block iron sheet, strip iron sheet, line iron sheet, wood grain iron sheet, meteor iron sheet, spindle iron sheet, drag iron sheet and loose iron sheet, its pressing depth is deep and shallow.

Cause:

  • The generation of the pressed iron sheet depends on the heating conditions of the slab, the longer the heating time, the higher the heating temperature, the stronger the oxidation atmosphere, the more oxidized iron sheet is generated, and it is not easy to fall off, the production of a single iron sheet is difficult to remove, and it is pressed into the surface of the steel plate during rolling.
  • The large vertical roller setting is not reasonable, the iron sheet is not squeezed loose, and it is difficult to remove.
  • Due to the low water pressure of the high-pressure descaling pipe, the blockage of the water, the wrong Angle of the water, and the improper use of the reasons, the iron sheet on the surface of the steel plate is not removed, and it is pressed into the surface of the steel plate after rolling.
  • Oxidized iron sheet occurs more in boiling steel, and red iron sheet is easily produced in steel with higher silicon content.
Iron Oxide

Iron Oxide

4. Uneven thickness

Defect characteristics: the thickness of each part of the steel plate is inconsistent, the thickness of the steel plate is uneven, the deviation is generally too large, and the thickness of the local steel plate exceeds the allowable deviation.

Cause:

  • Improper adjustment of roll gap and configuration of roll profile.
  • The wear of the roller and the bearing bush on both sides of the roll is different.
  • Uneven heating temperature of slab.

5. Pockmarks

Defect characteristics: The surface of the steel plate has local or continuous pits called pitting points, which are different in size and depth.

Reason: In the heating process, the slab oxidation is serious, and the iron sheet is pressed into the surface during rolling, and small pits are formed after falling off.

Hot Rolled Steel Pockmarks

Hot Rolled Steel Pockmarks

6. Flat roll

Defect characteristics: the end of the steel coil is oval and flat. Tends to occur in softer or thinner steel coils.

Cause:

  • In the process of lifting, the steel coil withstands great impact.
  • The steel coil is too tight, the temperature is high, and the steel coil is placed flat on the ground or stacked above it.

Conclusion

Hot-rolled steel is a widely used metal material, that plays a key role in construction, machinery, automobile, shipbuilding, petrochemical, and other industries, but it is inevitable to encounter some problems in the actual operation process. The above are the common problems of hot-rolled steel summarized by our company according to years of production and sales experience. If you have any questions, please feel free to contact us.

 

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