Called Superseed® Extra Al Inoculant, the new product contains a specially formulated combination of aluminium, strontium, and zirconium that essentially eliminates chilled white iron in thin sections and corners, increasing the machinability of gray-iron castings. The extra aluminium allows foundries to use a single alloy to increase the aluminium content of iron to more than 0.010%, a level that helps eliminate chill. The strontium and zirconium contents of this alloy enhance chill reduction and strength.
At the same time, the new inoculant achieves strong chill reduction without relying on calcium, as in other inoculation practices. As a result, this low-calcium inoculant generates very little slag, reducing the slag build-up in iron being transferred to pouring equipment and increasing the life of pouring-box refractories compared to other foundry inoculants. The unique combination of elements in Superseed® Extra Al Inoculant also lengthens the time it generally takes for inoculation to fade after additions are made.
“We developed Superseed® Extra Al Inoculant in response to a gray-iron customer who asked us for an alloy that maximizes chill reduction without building up slag in the pouring ladle,” said Matthew Liptak, Elkem’s Sales Manager who invented the alloy and has applied for a patent. “In extensive laboratory and field trials, we found that the alloy’s higher aluminium content, together with controlled strontium, zirconium, and calcium levels, achieved these goals better than existing inoculants.
As part of the development process, Elkem’s Research and Development facilities in Kristiansand, Norway extensively tested different inoculants in laboratory iron. Superseed® Extra Al Inoculant produced substantially greater chill reduction than either low-aluminium inoculants that contained only strontium and zirconium or aluminium-bearing alloys without strontium and zirconium.
“By increasing the aluminium content of iron to over 0.010% in the presence of strontium and zirconium, we achieved the optimum nucleation that is needed to eliminate the hard carbides that reduce machinability,” said Cathrine Hartung, Elkem’s R&D Engineer who conducted the tests at Kristiansand. “In addition, we found that Superseed® Extra Al Inoculant gave higher tensile strengths in gray-iron castings than the other alloys we tested.”
Superior chill reduction was also obtained when Superseed® Extra Al Inoculant was tested in production foundries and compared to other inoculants. In addition, long-term use of Superseed® Extra Al Inoculant produced less slag build-up in the pouring box compared to the other practices, reducing the risk of slag defects in the finished casting.A paper entitled, “A Novel Inoculant Promoting a Type A Graphite Structure in Gray Iron,” presented the laboratory and field results with Superseed® Extra Al Inoculant at the American Foundry Society’s 2018 Metalcasting Congress in Fort Worth, Texas.