Material type PIPE in BOM

Dear Gurus,

I am using pipeliene material as the component in semifinished assy. When I run the costing for the semifinished assy ity is giving error ""No price could be determined for material/batch XXXXXXXXXXXXXX/ plantXXXX

Message no. CK465""

The material type for pipeline item in PIPE.

What should be the item category for the PIPE materil in BOM of Semifinished product.

How the consumption for the PIPE material will update during the backflush.

Thanks and regards

Murugesan