NO. 875 Friability And Moldability Tester
The friability test measures the ability of a compacted molding sand to resist abrasion or scuffing in the first few millimeters at the surface of the mold. Two 2-in. diameter x 2 in. high (50.8 x 0.8 mm) AFS specimens are placed side-by-side in a 7 in. diameter (177.8 mm) cylindrical screen and rotated against one another.
The amount of sand abraded from the specimens after one minute is collected and weighed. The weight of sand removed, divided by the original weight of the specimens and multiplied by 100 is reported as the friability in percent. A friability value above 11% can indicate a tendency to produce dirt defects and loss of casting surface quality.
An adjustable timer controls the test, and the unit includes a collecting pan as well as a brush and coarse screen (to pre-screen the sample), for use in the moldability test. In this test, a 200 g sample of loose sand is placed in the cylindrical screen and rotated for 10 seconds. The weight of sand passing through the screen, divided by two, gives the moldability index of the uncompacted sand.
While the laboratory moldability test has been succeeded by the compactability test for expressing the degree of temper of a molding sand, it is still valuable for monitoring the performance of automatic moldability controllers at the mixers.
The Dietert Company founded by Harry W. Dietert in 1922 is now part of DIETERT Foundry Testing Equipment Inc. Throughout the years, Dietert Laboratory instruments have been used worldwide in controlling sand quality for the production of high quality castings. Dietert moisture testing, analytical and mechanical test equipment have set the control standards for a wide range of industries and products.