1). T e void was located on a casting surface that had no contact or wear with any other structure on the as- sembled bridge (Fig. 2). Next, on the construction site, an engineer ques- tioned a casting surface. Finally, before the project reached completion, a fork truck driver at the bridge construction site dropped one of the fi nished cast- ings and infl icted additional damage trying to put the casting back in the proper place.
Many steel casting customer are unaware of the design criteria necessary to make a part machinable. Prior to the parts being produced, a machine shop that can handle castings of the size involved in the project must be found. The location of the machine shop is critical.
were not an issue. Each part stated on the blueprint an ASTM A-27 or A-148 cast grade. No nondestructive testing was specifi ed on the drawing, nor were supplemental specifi cations included on the purchase order. In spite of the engineering teams’
eff orts, multiple post cast issues arose. During a walkthrough of the machine shop and review of machined and un-machined castings intended for use in a bridge assembly, an inspector made note of a small, 0.25 x 0.25-in. void with a clean, solid bottom (Fig.
Repercussions T e metalcaster indicated to the
customer that it was unusual for cast- ings and a project of this magnitude not to have any special testing or inspection requirements. However, the customer did not believe other specifi - cations were required for the contract. After the first problem was dis-
covered by the source inspector, sev- eral weeks passed before discussion began about which entity would pay for third party ultrasonic inspection of the defective casting. After mul- tiple conversations on the purchase specifications and responsibilities, it was determined the customer should pay for the testing. The acceptance criteria was determined to be per ASTM A609: • Procedure A, Table 2, Quality Level 1.
• Procedure B, Table 3, Qual- ity Level 2, Single Isolated Indications.
• Procedure B, Table 4, Quality Level 2-3, Clustered Indications. T e inspection was specifi ed to
cover more than half of the casting. T e part in question weighed more than 5,700 lbs. T e casting passed the ultrasonic inspection. For the casting surface issue
discovered on the bridge construc- tion site, additional material had developed on the casting due to a sand scab defect that occurred in the casting process. T e casting supplier was able to partially remedy the issue by grinding the surface clean. As a result of the discovery of the defect, the supplier and buyer decided to perform ultrasonic inspection on the second of two castings of the same part number. T e inspection neces-
42 | METAL CASTING DESIGN & PURCHASING | Jan/Feb 2012
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