Optimised testing of heat treated iron castings
Employing specialised heat treatment methods on high-grade ductile iron produces ADI, a sophisticated material that gives unique structure with high strength and good ductility. In addition, ADI are extremely light, completely recyclable materials and offer excellent wear resistance and good noise damping properties. The low manufacturing costs make ADI an economical component that may find many applications within various industries such as transport, construction, agriculture, process machinery and machine tools. Despite its key features and associated benefits, current methods that could assure the integrity of the ADI casting have so far been insufficient. Thereby, many variations are still observed between the ADI heat treatment parameters and NDE measurements, such as eddy currents. Urged by this, the project combined the multi-frequency eddy current with other NDE tests, such as ultra-sonic propagation velocity. The latter are sensitive to graphite form and may provide reliable information about matrix structure. Multi-frequency eddy current measurements are capable of optimising sorting of complex ADI structures and ranking ADI castings in order of hardness. For a given chemical composition, these measurements may accurately identify changes in heat treatment variables, while different combinations of variables may give similar measurements. Combining these measurements with ultrasonic velocity measurements and using suitable algorithms, the tests may predict with maximum possible confidence, proof and tensile strengths of the measured values. With today's dynamic marketplace driving high performance, industries need foundries that can respond to their exact casting needs. Using the combined NDE tests that involve inexpensive and fast mechanical testing, it is possible to develop ADI castings that will meet defined specifications. These advanced services may then allow foundries not only to expand current markets, but also to develop new markets for mass-produced ADI.