I’m not a metallurgist, but I am good at educated guesses.
knowing how those sheets are made, they are cast poured into an ingot and then sent thru a series of progressive rollers at a high temp. Basically the cross section of the ingot simply gets smashed and stretched into a sheet of X thickness.
I’ll bet there was a discontinuity in the ingot pour (possibly a stop-start due to a short run, or machine/human error, accidental splash of water, etc) that resulted in an contaminated layer of the pour. Then when it was rolled out that discontinuity is maintained at the same point in the cross section.
I’m not a metallurgist, but I am good at educated guesses.
knowing how those sheets are made, they are cast poured into an ingot and then sent thru a series of progressive rollers at a high temp. Basically the cross section of the ingot simply gets smashed and stretched into a sheet of X thickness. I’ll bet there was a discontinuity in the ingot pour (possibly a stop-start due to a short run, or machine/human error, accidental splash of water, etc) that resulted in an contaminated layer of the pour. Then when it was rolled out that discontinuity is maintained at the same point in the cross section.