Degassing Castings

Ask an Expert From: Products Finishing, , from Powder Coating Consultants, Div. of Ninan, Inc.

Posted on: 5/1/2003

Question: This is in response to your article in the October 2002, Products Finishing.

Question:

This is in response to your article in the October 2002, Products Finishing. I represent a company that manufactures a de-gassing agent. This material is added to the molten metal prior to pour where it consumes the different gases that are created. As you know these gases can cause porosity and other issues. This product is in effect in all metals and gases. I have attached a tech sheet. If you have any questions please let me know. J. B.

TECHNICAL INFORMATION: METALLURGICAL ADDITIVE

This product is a metallurgical additive that is a completely dissolved polymer, which, at the melting temperature of metal, provides a uniform and controlled evolution of gas. The additive is effectively a gas in solid form affording a new, convenient and 100% reliable method for introducing a gaseous medium into a metal melt for stirring, degassing and protective blanketing.

Physical Properties: The additive is a waxy solid, which is offered in the shape of cakes and weighs approximately six oz. and is also available in other forms based on individual engineering requirements. The surfaces to volume ratio determines the rate of gas evolution, and therefore cakes (ring-shaped sections) are designed to produce a uniform rate of gas evolution.

The six-ounce ring takes approximately 35-45 seconds to decompose at 2,900F.

Degassing: The initial action of the additive at melt temperatures is the production of gaseous alkenes. The mechanical action of alkenes rising to the surface at the melt temperature allows for displacement of dissolved gases without the possibility of excessive reoxidation of exposed surfaces.

Decomposing the additive consumes the available oxygen, thus protecting the molten metal from oxidation. The additive added to a mold prior to teeming of stainless steel for example insures against oxygen pick-up.

For more information on this product, please contact Magna-Chemical Technologies Inc. at (888) 851-4089; Fax (309) 593-4234.

Answer:

All you casting suppliers, please take notice. If this material does what it says and won’t compromise the metallurgy of the product being cast, then we may have some hope yet to reduce/eliminate out-gassing of cast products when they are powder coated.

As with the above question, I will pass this information onto my readers in hopes that maybe a new approach can be developed to reduce/eliminate outgassing of powder coated castings. However, I will have to see hard antidotal results or a study before I can recommend such a product as the next “magic bullet” to prevent outgassing when powder coating castings.

 


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