Hot Extrusion of new alloy

[telegraphroad]

Looking for a mechanism of removing the "as cast" structure of weld metal.  Metal is cast in a water cooled copper shoe, then turned round and cut to length.  Alloy is stainless steel "like" although is much harder than what most people are aware of.  Have anyone tried extrusion?  Zircar makes mounted ceramic extrusion dies in 0.05 inch to 1/16 inch diameter.  Looking at log splitter hydraulics (30Ton) as a forming tool.  Starting diameter would be about 3/8 to 1/4, about an 1 inch long.  Would a power hammering and annealing sequence be an alternative? 

 

Have not found a minimill that is willing to accept such small quantities of material.  

 

Motivation is finding a thesis topic.  Glad to share results/processing techniques.

 

If I've posted incorrectly please advise.   

 

Regards,

 

 

 

 

 

[ptree]

I have some experience in aluminum extrusion. From memory the extrusion pressure was 135,000psi at 925F. This was for the extrudable grades like 50XX series and 60XX series. The dies had to be massively supported and keeping weld and galling down was much of the technology. Graphite rub blocks on the runout table and graphite lubes were the industry standard 25 years ago when I had experience. A puller is needed to prevent a birdsnest of the extruded materials.

I do know that steel has been extruded, but have no personal experience.

Good Luck

[patrick]

It is not clear if you are wanting to change the microstructure of the metal or just the surface condition. Lathe turning as you described will only clean up the surface but will not alter the as cast microstructure. That will take mechanical deformation and heat. Extrusion could probably be used but would require surface conditioning as you are already doing. I suggest that you grind your ingot then experiment with thermal cycles (no deformation). See what properties and microstructure you get, then see what can be done from a hot work standpoint. Depending on the resources at the university, you may have access to a rolling mill. I would use that before a forging hammer since you can control the strain on the metal much more precisely with that tool.

 

Patrick

[telegraphroad]

Thanks for your inputs.  I do want to change the microstructure.  Turning the weld metal round was to get a slip fit within the extrusion tube.  Was going to use glass frit as a liner but will look at graphite.  I also think I'll start with aluminum and see what happens before increasing the temperature/changing to steel alloys.  

 

Strain control could be more critical than just getting a minimal amount of work in the weld metal--I'll look for an institution that has the capability.

 

Regards