“Slivers are elongated pieces of metal attached to the base metal at one end only. They normally have been hot worked into the surface and are common to low strength grades which are easily torn, especially grades with high sulfur, lead and copper.”- AISI Technical Committee on Rod and Bar Mills, Detection, Classification, and Elimination of Rod and Bar Surface Defects
Slivers may be caused by bar shearing against a guide or collar, incorrect entry into a closed pass, or a tear due to other mechanical causes. Slivers may also be the result of a billet defect that carries through the hot rolling process.
Slivers often originate from short rolled out point defects or defects which were not removed by conditioning.
Billet conditioning that results in fins or deep ridges have also been found to cause slivers and should be avoided. Feathering of of deep conditioning edges can help to alleviate their occurrence.
Slivers often appeared on mills operating at higher rolling speeds.
When the frequency and severity of sliver occurrence varies between heats, grades, or orders, that is a clue that the slivers probably did not originate in the mill.
Slivers are often mistaken for shearing, scabs, and laps. We will post about these other defects in the future.
Does dearburization suggest that the defect source was present on the billet during heating?
The more complete the decarb of the material under the sliver the more likely it was in billet.
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[…] scabs can be confused with slivers, shearing or rolled in scale, their ductility eliminates them as rolled in scale. Scabs are […]
What would be the acceptance tolerance be for items found to be having sliver defects
Great question, basically subject to your supply agreement/ spec. I have argued that the ya re rejectable undr ASTM A 108 spec under several criteria. However recent market developments suggest that the criteria are not that clear.
I have understood your opinions.