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merging designs for U.S. Army cannons are required to be smaller and lighter for integration into faster, more agile military land vehicles. Castings are well established in the private sector to reduce weight in cars and trucks while in- creasing structural performance, but they are underutilized in military applications. High performance specifi cations,


while challenging, are not the primary reason for this underutilization; rather, it is the long lead time typically required to fully comply with the military’s dimensional, surface integrity and internal integrity requirements. T e defl ector tray casting for the Army’s XM360 cannon (which is being redeveloped into the XM360E1 for the next M1 Abrams tank upgrade) is a success story illustrating how casting design was integrated with manufacturing engineering to transcend the usual outcomes of delays and cost overruns. T e integration of the casting process, casting fi nish- ing processes and machining of the rough casting resulted in an approved fi nished component 110 days from the Army’s order date. T e defl ector tray is both structural and functional. T e tray guides a new


projectile into the cannon’s breech and defl ects the spent casing into a hold- ing area after the projectile is fi red through the barrel. Due to force and surface wear, a steel alloy is required. Steel castings are renowned for structural tough- ness in severe service applications but also notorious for diffi culty in meeting cosmetic and dimensional requirements within a reasonable lead time. Because of their high yield strength, high material stiff ness and tolerance of defl ection without damage, steel castings also can be eff ective in lightweight applications. Pushing the limits of minimum as-cast wall thickness is important in reducing weight in this type of application.


H.A. Burrow Pattern Works


(HAB), Silesia, Mont., collaborated with the Metalcasting Consortium (AMC) sponsored by the Defense Logistics Agency (DLA), the Army’s Research, Development & Engineering Command (RDECOM), Benet Labo- ratory at Watervliet Arsenal, Waterv- liet, N.Y., Acme Castings, Huntington Park, Calif., and the Steel Founders’ So- ciety of America (SFSA) to convert an original 15-piece fabricated steel design to a one-piece, lightweight 19.5-lb. cast steel design.


The 15-piece fabrication design


was difficult and expensive to manu- facture and had an unacceptably high rejection rate. One of the first decisions in the new design was to choose a different steel alloy, because the carbon steel used for the fabrica- tion would not be a good casting candidate due to fluidity issues in the thin 0.08-in. wall sections. HAB determined an investment cast 17-4 PH alloy in H1100 condition had the fluidity and strength to be a good cast substitute. After numerous solid model


The printed inspection fi xture indicated minimum straightening was needed after heat treatment.


iterations, additional features previ- ously welded to the fabricated tray were added to the one-piece casting design, while still keeping the com- ponent’s total projected weight to 20 lbs. The additional features were added to the model casting require- ments, and the technical data pack- age (TDP) was modified accord- ingly. Benet sent a request for quote (RFQ) and TDP to a number of investment casters with the require- ment to provide one prototype cast- ing for testing, and then the project hit a snag. Benet received a few bids that were unacceptably high in price and lead time. Many investment casters who did not bid provided the following reasons: • T e walls were too thin. • T e thin-to-thick cross sections


Jul/Aug 2013 | METAL CASTING DESIGN & PURCHASING | 27


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