Undercure (Blocking)
If the initial cure is carried out below that necessary for full polymerization undercure may result in subsequent "blocking" or sticking of coated sheets.

Underfill
A cross-section which has not filled up the roll pass, so that it is inaccurate in both shape and dimensions.

Underpickling
Results when the steel has not had sufficient time in the pickling tanks to become free of adherent scale and occurs when acid concentration, solution temperatures and the line speed are not balance properly.

Unitemper Mill
It is used as one means for temper rolling or skin rolling of finished cold-reduced strip. The mill consists of two stands of two-high mills, but with the second stand above the first in the same mill housing, to provide closer spacing between the two stands. Here, the strip can be elongated a controlled amount between passes with only a very slight reduction in each stand due to rolling.

Universal Mill
A combination of horizontal and vertical rolls, usually mounted in the same roll stand. The mill is made up of two-high (and occasionally three-high) horizontal rolls, with vertical roll sets on either or both sides of the horizontal stand. The direction of the piece is reversed after each pass in the mill.

Universal Rolling
Rolling in an universal mill provided with edging rolls for obtaining width tolerance and better edges in plates and slabs.

Ultrasonic Test (Supersonic Test)
A versatile and highly-reliable non-destructive test for detecting and locating internal defects such as cracks, cavities and unsoundness due to discontinuities, by the application of high frequency sound waves. The detecting instrument transmits such waves through the prepared surface of the material under test and these waves are reflected back by internal flaws.

Upend Forging
A forging produced in a closed dies so that the direction of the grain flow is largely at right angles to the die faces.