What's new
What's new

Machining 25Cr Super Dulplex (F55) forgings advice...?

DMSCNC

Plastic
Joined
Dec 14, 2017
Hi,

We are looking at machining some 25Cr super duplex forgings and I am looking for some advise on the best procedure/process for doing this? Ideally from somebody that machines this material on a regular basis if possible. We have only machined this material in limited amounts in the past and they were very small components, these items are around 270mm dia x 490mm long.

We planned to rough machine the parts fairly close to size and then leave for 48hrs before finish machining, when I say fairly close I mean around 0.5mm (.020") left on all over. As I understand the material moves around a lot after roughing.

If anyone has any advise on this it will be greatly appreciated?

Note: Parts will be turned and milled.

Thanks in advance.
 
I had to ask, as those sizes are near identical for a turn key I did for a client in 2507.

What condition are you getting the castings? (post cast annealing\stress relieved?)

Turning is pretty straight forward, but you have to be careful not to rub while turning, or youll have notch wear like a bastard on your turning tools and end mills.
I like to use HSM toolpaths for milling SD, just make sure youre feeding enough, and not running sfm too fast.
Flute engagement is critical, or youll hammer the cutting edges off the endmill. Larger CR, SHARP cutters with a good coating.
No recutting chips.
Avoid interrupted cuts where you can.

Treat like 316L, but shittier.

Kind of tough to give details without an idea of part shape.
 
Hi Macds,

Thank you for your reply, I have only been given limited amounts of information on the castings but I believe they are stress relieved. The sizes I stated are pretty rough, not really exact dimensions. We machine a lot of 316 so that is good to know, although I imagine the SFM will be way down in comparison to even 316? We will typically cut 316 at 120mm PM, whereas we have had to machine other exotics (Inconel) at 20-30mm Pm. Substantially slower.

What is your opinion on the rough turning and rest period to allow the material to move?

Thanks.
 
Your feed rate is going to be based on chip load and cutting speed.
For full engagement HSM type endmilling I like to be between 180-220 sfpm. Chip load (accounting for radial chip thinning) is around .005" with a 1/2" end mill, full depth of cut and .045" step over.
Turning we can be down around 80 sfpm, and .01" feed per rev. .05" DOC.

rest period we dont usually worry about too much, as it has lots of time to move while roughing.
Also depends on where on the part material is coming off (all one side, or balanced?).

You could try a low temperature "aging"\stabilization cycle in your heat treat oven after rough machining, if you have one.

Hope this helps a bit.
 
We machine a lot of F55 forgings.
Are you cutting forgings or castings? You mention both.
For rough turning we preferably use something like a PSBNR (approach angle of 75 degrees)
and for facing PSKNR (Again 75 degrees)
You can't get into a corner with this geometry so we would rough as much as possible with the above
then take the corner out with a CNMG
We've tried a lot of different tip grades but always seem to end up back at Sandvik 2035 with 1.2 tnr
50/60 m/min
0.35mm/rev
4mm d.o.c.
What lathe are you doing the turning on?
 
Last edited:
The parts will move as you machine them as stresses imbalanced by the removal of other stressed material find new equilibrium and as cold work surface stresses imparted by the cutting process do the same, but from a metallurgical perspective there won’t be a delay in the distortion process; It’s instantaneous.

After ensuring the forging has been stress relieved prior to rough machining, the best thing you can do to minimize distortion is to ensure your semi-finish and finish passes are cut with fresh edges in good condition to minimize cold work of the surface.
 
Thank you to all that have replied, that is a great help.

The approach angles and the S&F's will give us a good starting point.

The material being removed is pretty balanced, and the components are heavy walled once finished so I am hoping for not too much movement.

The machines will be Mazak Nexus QT250 and CMZ TBI520 - Both 2 axis lathes. (turning) The milling will be done on a Mazak VCS 430 (4 axis).

Thanks again.
 








 
Back
Top