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QC manual for forgings?

Q: What methods do you suggest for evaluating forging quality? I would still like to use magnetic-particle examination, but what is a good acceptance standard?

... I am trying to compile a quality specification for forgings we produce. A fairly extensive spec for cast parts has been created, and includes quality checks such as dimensional, magnetic particle, radiographic, and mechanical properties. For our castings we use ASTM E446 for the testing method and ASTM E125 for the acceptance criteria.

A: In general, the NDT specifications are not very comprehensive for automotive parts, but for aerospace they are quite comprehensive. So much depends on the safety-critical use criteria. For steering parts, the use of magnetic-particle inspection on a sample basis is typical for automotive and truck parts. Once a part is found with this test, it then is extended to a much larger sample and even 100% on occasion. Tensile property tests are typically specified for most all forgings depending on heat treatments, and/or if they are micro-alloy forgings. Nonferrous forgings are usually tested on a sample basis (1 per 1,000, or so.)

I know of no radiographic requirements on forgings. Ultrasonic testing is specified for aircraft/missile forgings, as is magnetic-particle testing and penetrant testing.

For more than 40 years H. James Henning held key technical positions in the forging industry, including as director of technology for the Forging Industry Association, and as president of Henning Education Services, a Columbus, OH, firm specializing in customized education and training in forging technologies.

Guidelines and recommendations offered in this column are based on information believed to be reliable and are supplied in good faith but without guarantee. Operational conditions that exist in individual plants and facilities vary widely. Users of this information should adapt it, and always exercise independent discretion in establishing plant or facility operating practice.

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