[ Casting ]
[ Casting ]
Table 2 . Common NDE / NDT activities .
NDE / NDT method General applications and positive attributes Limitations Radiography ( RT )
Magnetic Particle ( MT )
Liquid Penetrant ( PT )
Ultrasonic Testing ( UT )
Visual Testing ( VT )
Can be used for ferrous and non-ferrous materials . Has a great reference library from ASTM ( E192 , E186 , E280 , E446 ) for steels . Many different classifications of defects are showcased in the above reference radiographs
Used for ferro-magnetic materials as extremely sensitive to cracks and does well highlighting larger rounded indications .
Used on non-magnetic materials highlighting cracks of all sizes but is more sensitive when used as a fluorescent method . Does very well with all sizes of rounded indications .
Must be used on fine-grained materials . Larger-grained microstructures like austenitic materials and nickel-based alloys lose the back reflections .
Used to verify cast external and internal surfaces using reference photographs or tactile plates . Easy to use magnification to assist in evaluation .
Casting wall thickness vs . thinness and the ability to maintain proper levels of sensitivity . Is not reliable to exhibit cracking and linear indications .
Smaller ( 0.062 ” diameter and smaller indications ) are hard to ascertain . Relies on being able to magnetize with coil or cabling .
Can leave many false indications on the surface of certain alloys . Limited to surface evaluation only .
Needs a very experienced technician to be able to ascertain reflections from the material being tested .
Can be very subjective to determine conformance to specifications , difficult to find readily available Level III personnel . and reliable . UT is also capable of measuring material thickness . UT offers the flexibility of being a portable method . It can be done onsite and brought to the field where parts may be located . Radiography is more cumbersome and inconvenient for portable field work .
NDE / NDT overview Table 2 lists common NDE / NDT activities with some positive attributes and limitations that come with each technique .
Dimensional Testing Customer orders often require the produced parts to be measured to verify conformance to the customer ’ s drawings . They are expected to be able to measure with electronic devices such as coordinate measuring machines ( CMM ’ s ), dimensional scanners , and other electronic hand tools .
Positive Material Identification ( PMI ) Monitoring incoming materials as melt stock , qualifying outgoing foundry returns sales , as well as fulfilling contract or specification requirements makes PMI an extremely useful and operator-dependent procedure . PMI is a portable chemical analysis using a hand-held analyzer . This type of analyzer uses an x-ray tube which is like the full-sized XRF chemical analyzer or a laser-induced ablation technique ( LIBS ).
Hardness testing Hardness testing is a way to measure the surface quality of a cast material via proper response to heat treatment . It can be an indicator of the performance of the material based on its given application and is typically a requirement when certifying any high-specification cast alloy . Rockwell , Brinell , Vickers , Knoop , and Leeb- Equotip methods are commonly used in the foundry industry to meet high specification requirements . There is a multitude of specifications for the testing of material hardness both ASTM and EN / ISO .
Metallurgical testing In high-specification work , the need to determine the chemical , mechanical , and material properties of cast metal is crucial in ensuring that the customer receives a product that meets their design requirements . OES , tensile , hardness , impact , corrosion , metallography , and ferrite prediction testing are all essential methods to satisfy the stringency of high-specification castings .
Source inspection A source inspector is hired by a customer / disinterested third party , or the engineering group overseeing the project , to witness milestones in the creation of the casting . Common oversight is for some of the following operations :
•• Contract review
•• Melt and pouring
••
Stamping of heat numbers for traceability – castings and test material
•• Heat treatment
•• Welding
•• Post-weld heat treatment
••
All the inspection operations – VT , RT , MT , PT , dimensional , etc .
••
Endorsement of the certification package
••
Shipping operations
In conclusion The contract review , inspection , and material testing of high-specification casting are crucial to ensure that all identifying criteria are met during production . Projects require many details to be followed for a highspecification casting to be produced right the first time . The potential for economic and environmental impacts or loss of life puts stress on the foundry to verify the steps and operations are correct , processed by properly qualified technicians and certification personnel , and produced to the highest of quality and standards .
About the author
Michael Porfilio has worked in the American foundry industry since 1980 . His background is in the fields of metallurgy , quality management , sales , and marketing as well as operations management . He is a NDE Level III / ASME NQA-1 Lead Nuclear Auditor and ASTM A01 , E01 , and E07 Committee Member . Mike is the Director of Quality and Technical Services at Stainless Foundry & Engineering , Inc . in Wisconsin , USA , and also performs consulting in the business , quality and materials arenas .
30 Stainless Steel World June 2023 www . stainless-steel-world . net