The project objective was to reduce the manufacturing costs of Alloy 625 piping systems on Virginia Class Submarines (VCS). This project demonstrated that a newly identified closed-die, cold forming technique can be economically and successfully applied to manufacture large-bore, seamless elbows made of Alloy 625, a nickel-based alloy.
The cost to produce seamless Alloy 625 large-bore elbows is high due to expensive raw material and forming costs.
The new cold forming process results in minimal thinning of the wall in the heel of the elbow, thereby allowing the wall thickness in the starting pipe to be reduced. The reduced wall thickness equates to less raw material required for a ship set of fittings. Cost savings is based solely on the current market price for the raw material used to manufacture the Alloy 625 elbows. Raw material cost savings have been found to range from $660K to $150K per VCS shipset.
The project will position the forming vendor to compete in the next multi-hull procurement by General Dynamics Electric Boat, starting with VCS SSN 792. Northrop Grumman Shipbuilding - Newport News has already procured seamless Alloy 625 elbows formed via the identified process for CVN 78 Class. The new manufacturing process is applicable to new construction, overhaul and repair and can be further extended to Alloy 625 piping systems on all Navy platforms.