I am thinking about constructing a 350 ton press, and would like to try extruding some aluminum for grins and giggles. my problem is that I have no experiance in making the extrusion die. I have made many presses, and precision heating furnaces, so that should not be a problem. but in the die lyes some chalenges. the part I want to make is a hallow part, I understand the consepts of extrusion, however lack some specific information. here are some questions that one might be able to answer, I am looking into purcahsing some good books on the subject as well:
What are the tempratures used to extrude aluminum?
What are the angles leading to the finish edge?
Is there typically a "final" flat that is parralel to the surface of the part or other angle just before the part leaves the die?
When using a forming mandrel for the hollow, what taper is common on the leading edge and the trailing ege?
On the trailing edge of the mandrel what distance is typicall from the finish edge to allow the parts material to flow together properly?
What strength or alloy of material are the dies typically made with?
Aluminum is heated to a superplastic state for the extrusion. The temperature should be about 480-530 celsius for 6061 if I remember correctly. If your extrusion press is powerful enough you can extrude cold aluminum but it will quickly wear the dies.
There are two types of flow-channel - extrusion surface combinations I have seen. The other has a leading edge angle ranging from parallel to about 30 degrees followed by a 1mm high step. The extrusion surface is located at the top of the step. The other combination has the extrusion surface continue straight from the flow channel without a step. The latter comfiguration usually has a very slight angle of 5 degrees at most. The former is used on small wall thicknesses and the latter on large ones.
The extrusion surface length should also reflect the wall thickness. Extrusion surface length range from 3mm to 50mm. There isn't really a clearcut answer for your questions because even today the final filing and grinding of the flow channels and even extrusion surfaces is made by hand.
On 230mm dies the flow channels merge to form flow welding about 1" before the extrusion surface starts.
All the extrusion dies I've seen have been made of either ANSI H11 or H13. I don't really know what determines which one is used. The dies are gas nitride hardened before extruding.