CASTING INNOVATIONS
Ductile Iron Treatment Reduces Magnesium, Improves Properties Ductile iron casting facilities
often face metallurgical limitations arising from excessive magnesium use, which can lead to carbide- forming tendencies, shrinkage and nonmetallic inclusions. Foseco, the Foundry Division of the Vesuvius Group, now offers a treatment pro- cess that can replace the magnesium ladle treatment process and can reduce the use of magnesium while improving properties. Te INITEK process uses a
specially designed prism-shaped converter ladle (i.e. the CONVER- TOR ladle,) unique thermal analysis equipment (i.e. the ITACA sys- tem) and engineering and process know-how, along with proprietary consumables, to increase magnesium- recovery and reduce temperature loss in the production of ductile iron. Te iron is initialized with Foseco’s INODEX alloy to neutralize oxygen and ensure that oxides are present as nucleation sites that promote graph- ite growth, rather than as slag. After initialization, magnesium treatment is performed followed by a small, late- stream inoculation. According to Foseco, magnesium
recovery with INITEK occurs in the range of 75-98%, depending on the size of the Convertor. The variable oxygen in the base melt does not combine with magnesium to form slag. It becomes suspended as mi- croinclusions of oxide that provide
Table 1. Cost savings from the Initek process. Cost changes Refractories
Energy
Metallic charge (pig iron and steel scrap) Casting cleaning, shot-blasting & grinding TOTAL
Value per ton of liquid iron ($) +3.64
-10.41 -40.35 -39.04 -96.31
Table 2. Comparison of the magnesium ladle treatment process and Initek. Previous process
Initek
Furnace charge and metal treatment Pig iron
Steel
FeSiMg Inodex
Tap temperature
Mechanical properties specified and achieved Tensile strength (350 Mpa)
Yield strength (220 Mpa) Elongation% (22) Impact Energy (12) Hardness (150)
nucleation sites for inoculation. Magnesium is no longer used as a de-oxidizer, so lower magnesium additions are required. By reduc- ing excess dissolved magnesium in the melt, a soft iron with high elongation results. The absence of slag increases fluidity, so pouring temperatures can be lowered. Metalcasting facilities treating
their iron with INITEK have been able to reduce the use of pure raw
80% 15%
1.775% 0
2,768F
415 260 16 13
155
40% 55% 1%
0.4% 2,642F
382 230 27
17.5 137-140-147
When Foseco’s converter ladle is in the horizontal position, the surface area losing heat to the atmo- sphere is smaller than it would be in a cylindrical vessel. When upright, the metallostatic head of the converter ladle is greater, which increases magnesium recovery.
44 | MODERN CASTING April 2012
materials and still obtain the re- quired properties. A French jobbing metalcasting facility began incorpo- rating the INITEK process to im- prove its metallurgical consistency. The iron shop produces castings up to 2.2 tons (2 metric tons), many of which are for the highly-specified wind industry. It used 1 and 2-ton capacity converters with an INO- DEX addition rate of 0.4%. The same metalcaster realized a total savings of $94 per ton of mol- ten iron with the INITEK process (Table 1). The elongation and low temperature impact properties were significantly improved over its es- tablished magnesium ladle treatment process, even with a charge using less pig iron and more steel scrap at a less expensive price (Table 2). The manganese content of the alloy is higher, and the silicon content is re- duced, which would normally reduce the elongation properties. The INITEK process is currently used in production in six metalcast- ing facilities worldwide and in trials
at 16 plants. Visit
www.foseco.com for more information.
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