Tubitak

Yucel Birol

Osman Cakir

Fahri Alageyik

The present invention describes an effective grain refining practice for aluminum foundry alloys. The method described herein relies on the control of the Titanium level of the alloy to be grain refined and the addition of boron once it is melted. Boron addition can be made via Al&#x2014;B master alloys as well as with boron compounds such as KBF4 salt. The boron added into the melt dissolves first and then forms the AlB2 particles that act as potent substrates for the nucleation of aluminum once solidification process starts. The Ti concentration of the alloy must be controlled below 100 ppm for this method to offer effective grain refinement. The boron becomes ineffective when the Ti concentration in the alloy is higher.

Grain refinement, aluminium foundry alloys

A process is provided for producing aluminum-titanium-boron grain refining master alloys containing soluble titanium aluminide and insoluble aluminum boride particles, the process comprising mixing aluminum-boron alloy powder and KTiFsalt to obtain a blended mixture, heat treating the mixed powder blend thus obtained in an inert gas furnace just below the melting point of aluminum, at approximately 650 degrees Celcius sufficiently long and compacting the heated powder blend in the form of tablets. The cast grain size of an aluminum- 7 wt % silicon foundry alloy after inoculation with this master alloy at an addition level of 0.02% Ti was less than 200 microns for contact times of upto 15 minutes.

Process for producing improved grain refining aluminum&#x2014;titanium&#x2014;boron master alloys for aluminum foundry alloys

A process is provided for producing an aluminium-titanium-boron grain refining master alloy containing titanium boride and titanium aluminide particles, the process comprising melting aluminium in a silicon carbide crucible in a medium frequency induction or an electric resistance furnace, adding to the melt at a temperature between 750 degrees Celsius and 900 degrees Celsius, KBFand KTiFsalts, pre-mixed in proportions to obtain a Ti/B ratio of 5 in the melt, gently mixing the salt mixture with the melt without introducing any stirring, transferring the molten alloy to an electric resistance furnace maintained at 800 degrees Celsius, decanting the K&#x2014;Al&#x2014;F salt, the by-product of the salt reaction, thoroughly stirring the molten alloy in the SiC crucible with graphite rods before finally casting the molten alloy into cylindrical molds in the form of billets and finally extruding the billet into 9.5 mm rods.

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Kocaeli, Turkey

Yucel Birol