Simple Solutions That Work! Issue 8

Attempts at switching inoculants and/or blending inoculants met with little to no improvement. The end consumer of the castings had to anneal all castings to eliminate carbides. To reduce costs, the customer requested that the castings must be produced as-cast to avoid costly heat treatment and improve machinability. Foundry A produces ductile iron to a 65-45-12 ferritic specification. Melting is done in a 6,000-pound medium frequency induction furnace. A 1,200 pound tundish ladle is used for magnesium treatment; 1.75% GloMag R6-8 magnesium ferrosilicon is added to a 1,000 pound tundish ladle, and covered with 7 pounds of cover steel. The standard post-inoculation practice consisted of adding 4.5 pounds of Calsifer 75, a calcium bearing 75% ferrosilicon. A K15 cast in-mold inoculant insert was used in each shell mold. All attempts using numerous inoculant blends failed to eliminate carbides. The most successful combination of inoculants was found to be 3.0 pounds of Calsifer 75, 3.5 pounds of VP216, and 0.6 pounds of SOD added as a separate, independent addition to enhance the performance of the inoculants. The occurrence of carbides in thin sections was eliminated only when SOD was used. The properties of the standard inoculant practice compared to using the modified practice using Sphere-o- Dox as an inoculant enhancer is shown below: STANDARD ENHANCED PERCENTAGE PRACTICE INOCULATION IMPROVEMENT Nodule Count 250 300 20.0% % Nodularity 95 97 2.11% % Ferrite 20 58 190.0% % Pearlite 60 32 - 46.7% Reduction % Carbide 20 0 - 100% Reduction The mechanical properties obtained from these same castings, are shown below: UTS (PSI) YS (PSI) % ELONGATION BHN Customer Specification 65,000 Min. 45,000 Min. 12% Minimum 156-217 SOD Enhanced Inoculation 68,600 48,000 19.9% 162 Both the microstructural and mechanical property improvements elicited very favorable results for the end customer. In addition, elimination of the annealing cycle and improvement in machinability resulted in significant cost savings. This example of a Sphere-o-Dox case history has been equally successful in casting pearlitic ductile iron grades and is just one example of how a custom-blended inoculant, containing sulfur and oxygen, can result in significantly improved inoculation. Presently, many foundries throughout the world have incorporated using this non-ferrosilicon based oxygen and sulfur containing inoculant to increase the potency of their current inoculation practice to not only reduce their inoculant cost per ton, but also to improve mechanical properties and machining properties. Note: This article is a longer version of an article that originally appeared in the January 2018 issue of Foundry Management & Technology. Reprinted by permission of Penton Media, Inc. 34 Contact: ROD NARO [email protected]