ceramic bead in wire patenting ???

[aeroceramics]

I was told that ceramic beads (based on alumina) are being used during the wire patenting process.
Is this true?
If so, what would be the reason for using the ceramic beads?

Any help is greatly appreciated.

Aeroceramics

 

[swall]

This would be a fluidized bed heat treat. You have a fine "ceramic" media (powder), such as alumina or silica that is heated and then fluidized by an inert gas, usually nitrogen.This fluidized mass of media is contained in an open vessel, heated at the patenting temperature and the wire is drawn through.The fluidized beds are a replacement for lead baths, historically used in the patenting process. It is desirable these days to get the lead out, and the fluidized beds are one option.They have the side benefit of not leaving lead deposits on the wire.

 

[aeroceramics]

Thanks so much Swall.

Few more question.

Could you explain how this fluidized bed heat treatment affects the wire properties?

I was told that spherical beads (diameter ~2mm) are used, not "powders". Obviously, spherical beads would not cause any scratch defects on the wire surface whereas angular shaped powder might cause scratches.
Is there any specific requirement for the fluidized bed media? What's the typical size?

Thanks in advance.

 

[swall]

Patenting produces a fine pearlitic structure, whereas a quench and temper process for steel produces a martensitic structure. Wire (in the range of 1% carbon) is unique among steel products in being capable of being processed by patenting. As for mechanical propeties, a .060" dia music wire would exhibit a typical tensile strength in the range of 310ksi, whereas a quench and temper process(i.e. oil tempered carbon steel wire)on wire in the same size range would yield a typical tensile in the range of 260ksi. I can't answer the question about the 2mm bead size. Most fluidized beds I'm familiar with use alumina in the size range of around .1mm (.004").

 

[swall]

I shouldn't overlook the simple expanation here. Perhaps the 2mm beads are used to cover the top layer of molten lead in a conventional lead patenting bath.Top cover of some sort is necessary to prevent lead oxide fumes from being introduced into the air around the bath.