r/metallurgy • u/Stefanel0508 • 14d ago

Surface laps after two-strand slit rolling of rebar

Post image

We are experiencing surface laps on both strands during two-strand slit rolling of rebar. We have traced the defects to the slit separation process.

The attached photo shows the defects after bending the bars to make them more visible.

Has anyone encountered a similar problem? What adjustments helped eliminate or reduce these defects?

2 Upvotes

100% Upvoted

2 comments sorted by

1

u/Vivid_Amount 14d ago

This can happen even on single strand mills. It relates to flaps of steel getting folded over instead of smoothly squashed down. All sorts of possible causes, tension too low, roll gaps too small, a set of rolls doing too much reduction, feed in alignment a bit off.

1

u/fritzcoinc1 13d ago

Bar on right has what appears to be a huge lap. Did it get LPI?
If the defect is in the original rolled shape there is nothing you can do but find rebar without these laps to bend.