English to Spanish Tech/Engineering Engineering: Industrial Cold finished bars

Es un tipo de defecto que puede mostrar una barra de acero especial, en este caso para la fabricación de chavetas de uso industrial.
En el texto que estoy traduciiendo. aparece este requisito:
"The product furnished shall be free from pipe"
Aquí hay una descripción del defecto:
"When molten metal is poured into an ingot mold it cools, starts to solidify and contracts. The outer surfaces solidify first and become fixed, while the center remains molten and, as it in turn cools and contracts, a depression is formed in the top. If a source of molten metal is not maintained at the top of the ingot this depression can be quite deep. It is known as primary pipe..., etc."
http://www.eolss.net/Sample-Chapters/C05/E6-36-04-01.pdf

¿Hay algún término conocido en español?
Gracias de antemano,