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Getting Cleaner Metal into the Mold

April 8, 2010
New techniques are emerging to improve the value of castings by improving the efficiency of molten metal treatment and pouring, for iron and aluminum.
Foseco’s INITEK process, a patented technique for ductile iron inoculation , will be commercialized later this year.

Cleaner metal means better quality castings, so metalcasters continue to seek techniques to improve moltenmetal treatment, handling, filtration, and pouring processes. For example, later this year Foseco will introduce a new initializing process for ductile iron production, promising that it will make inoculation more efficient and more effective, and improve a foundry’s overall productivity. More specifically, the developer says the INITEK process will improve metallurgical and mechanical properties of the ductile iron.

Foseco says INITEK is particularly well suited to foundries that conduct magnesium treatment ain the ladle, such as sandwich and over-pour techniques. Reducing the consumption of magnesium ferrosilicon (or other inoculants) will allow lower tapping temperatures, reducing melting energy consumption. It also raises the possibility of using low-cost iron scrap without affecting the final metallurgical properties.

INITEK, for which a patent is pending, involves four components: a specially designed ladle for magnesium treatment, called the “Foseco converter”; specially developed inoculants and a high-insulation refractory lining; proprietary process know-how; and a specially developed thermal analysis system to measure the quality of the liquid iron.

As to finished products, because INITEK uses fewer ferroalloys, which improves the purity of the iron, it also reduces the cost of cleaning and heat-treating finished castings.

Recognizing the difficulty and hazards of in-stream inoculation, especially in highvolume production, flow-control process specialist SERT is working to improve iron quality by addressing inoculation, too. Undetected, improperly inoculated molds may be responsible for a series of scrapped castings if the defect is not detected soon enough, it explains.

The company offers the SERT-INOCHECK process to monitor in-stream inoculation, to ensure that each mold is ready for each pour. Whenever inoculant is missing in the iron stream — e.g., inoculant starts too late, inoculant stream is absent or misaligned, or feeding time is too short — the process triggers an alarm.

Alarms can be used to stop the pouring process, leaving the mold less than full and easier to detect and reject downstream. Or, alarms can be used to stop the molding line or flag a mold that poorly completed.

In addition, the SERT-INOCHECK system stores images of the actual inoculation, for use immediately and/or later. During production, any flagged mold can be “replayed” to help the operator understand the cause of the alarm and take immediate corrective action. When production is stopped, the whole database can be read and the statistical results analyzed to locate causes of poor inoculation.

Another development from SERT is an inoculant dosing system, INOFEED. Used in combination, INOFEED and INOCHECK make casting production more reliable, and both systems can be used in conjunction with SERT’S UCERAM automatic pouring system to optimize iron pouring control and casting traceability.

One supplier concentrating its development efforts on the comparable point in the production of better quality of aluminum castings is Pyrotek. The FIT 10 flux injection unit is a portable and cost-efficient, mechanical fluxing station, designed for sub-surface injection of powdered or fused flux at a rate of 1–3 lb (0.5–1.4 kg) per minute. For flexibility and portability in casting operations, it was designed without electrical connections: it runs on pressurized inert gas.

The FIT 10 unit can be used to deliver fused refining agents and powdered fluxes to remove akali metals and to separate inclusions from the molten metal bath. Powdered fluxes also remove inclusions and help to keep the furnace clean, which extends refractory life and reduces the risk of damage during physical cleaning.

The unit is a 60-lb (27-kg) stainless steel tank, corrosion-resistant and capable of large-volume injections. Flux-flow rates from 1 to 3 lb/min are achieved, and there are no moving parts to wear or plug. It operates with argon or nitrogen.

In process, the FIT-10 removes oxides and hydrogen for cleaner aluminum, and with less smoke generated from fluxing because the reaction takes place below the metal surface. This also reduces the amount of flux needed, and reduces the amount of aluminum retained in the dross.

It is inexpensive to operate, and the controls are simple enough to minimize operator training; the small platform (24 x 24 x 36 in.) simplifies portability. The unit’s removable lid makes inspection simple.

For aluminum transfer, Pyrotek has introduced the Overflow Transfer System. The OTS is an integrated transfer pump and graphite shaft/impeller that eliminates risers and posts. An optional strainer or bonded particle filter is available, too. An integrated launder system is supplied, and a lightweight chute mates with the exit of the overflow bowl.

With four different bowl lengths, there is a size available to fit any furnace, according to the developer, and its small footprint ensures it can be dropped into almost any transfer well, with no furnace modifications.

Customers report very smooth metal transfer results, Pyrotek says, including half the amount of dross compared to common transfer pumps. It adds that metal quality tests show that the OTS delivers better quality metal from the furnace, without the need for transfer piping, and reduced maintenance.