SURFACE DEFECT IN HOT ROLLED PLATES

[Mehdi Vafakhah]

Dear experts

Could you help me to identify the these defect. ( attached pictures )

or refer a guide document that provide me more information about hot rolling defects.

best regards.

 

[Bob D]

Knowing the steel grade and plate condition (hot rolled, normalized, et cetera) will help in being more accurate in describing the conditions. Conditions in first 2 photos (10-47-54 and 10-48-04) look like remants from scale patches, where the relatively light mill scale was rolled into the surface and then came off, leaving the mottled surface appearance. The last photo (22222) looks like rolled in scale, where heavier mill scale has been rolled into the plate surface leaving the surface imperfections, with some of the scale having  "popped out" leaving depressions in the plate surface.

[Mehdi Vafakhah]

Thank you Mr. Bob D.

Material grade is 235 J0 and first 2 photos are blasted to sa3 .

Best regards.

[george....@gr.bureauveritas.com]

Check para. 7.5.2 of EN 10025-2

best regards

Dr. Georgios Dilintas

Authorized Nuclear Inspector
Authorized Inspector Supervisor

I&F REGIONAL TECHNICAL MANAGER
BUREAU VERITAS PIRAEUS - GREECE

Tel: +30 210 40 63 113 /4 /5
Fax: +30 210 40 63 118
Cell: +30 69 44 64 62 04


Mehdi Vafakhah ---15/09/2015 15:01:47---Thank you Mr. Bob D. Material grade is 235 J0 and first 2 photos are blasted to sa3 .

 

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[Mattia Degli Esposti]

Dear Mehdi Vafakhah,

I try to response to your question with a low number of informations. So I can make an assumption: the material has no defects, like segregation and wrong chemical composition.

In this point of view, the reason of these defects is searchable in hot rolling parameters. Especially analyzing the photo 22222.jpg, it's clear that the metal couldn't follow the plastic deformation imposed by the process. So in my opinion defects are due to:

-  temperature too low

-  strain rate too high (attributable to an angular velocity of rolling cylinders too high)

So, unless then problems related to the material, with a correction of these parameters (increase of T and/or decrease of angular velocity of cylinders), it gives to possibility to the steel to follow the imposed plastic deformation, in order to decrease the defects.

Regards

Mattia DE

[Harish Kannepalli]

I think these plates are stacked one over the other in open yard, probably in sea port. During night, the moisture condenses on the edges and slowly flows inside. Causing this type of surface corrosion.

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Regards,

Mr. Harish.