What steel??

[Bruce Caulley]

Needs to have good machinability. Parts need to be nitrided after machining with minimum distortion.

 

I can't really say what the parts are, sorry.

 

I know it isn't much info, but I thought I would throw it out as a general question and see what anyone recommends.

 

Bruce

[mayday]

4130, 4340, 28-32 Rc

if the parts are somewhat delicate, restrain them in a clamp fixture thru heat treat

[Greg Williams]

Bruce

 

I would think any of the plastic mould tool steels would be OK, M200, M235, P20

[G Caputo]

Bruce,

Some of our mandrel parts get nitrided. looksy It's usually 4140 ht, decarb free material, 28-32 Rc that this gets done to

[Jack Mitchell]

Is the purpose of the nitride for extreme pressure or wear as in a dusty or grainy type environment?

Perhaps core material hardness is a none issue or is the workpiece required to be tough as well?

The basic size and function of this project is really the questionable factor here isn't it!

 

 

Regards, Jack

[Bruce Caulley]

Thanks all. Jack you are right. Core hardness is irrelevent, nitriding is for wear protection only. Parts are "smallish" with no thin walls and weigh between 50 and 350 grammes.

 

I have been using 4140 but would like to reduce cycle time by using something softer that I can still give a tough case.

 

Bruce

[CAM-mando]

We use Nitralloy.

 

Here is a good link though.

 

http://www.key-to-steel.com/Articles/Art132.htm

[Jack Mitchell]

8620 cuts like mild steel without the gumminess (simply delish).

The case harden goes up around 60Rc and can vary from .02" to .04" depending on your specification.

 

I would likely experiment with 8620 before entertaining gas nitriding.

 

Regards, Jack

[Bruce Caulley]

Thanks Cam.

 

Jack,

Does 8620 distort much during HT? I like the look of nitriding because with the tolerances I am chasing I could probly get away with no finish ops afterwards.

 

Bruce

[Jack Mitchell]

I would like rate a distortion factor on machining stresses to be relativly equal between 8620 or gas nitriding. Sand blast will clean the parts as this works on most carburized heat treat applications; the 8620 "slightly blackened" can be buffed to make it pretty though.

The method of hanging the workpiece on wires or placing them on support blocks is evident with nitriding.

Your heat treat specialist might have some valuable opinions to consider here as well.

 

Regards, Jack

[betts]

Bruce,

I am with the P-20 suggestion, as its stability is good, and it nitrides well. We have done this several ways. Our favorite is using XADC coating from Armaloy, but we have also used several different nitriding operations, the most popular being one called "Dyna-Blue". If you can't find anything on it, I will look it up for you. Don't have it available at the moment.

 

My .02

 

Nothing wrong with 4140, but it would need to be pre-hard for best results, and I think the P-20 would be better. Actually the best P-20 we have found for machinability is the Japanese PX-5. It really does machine easier, and although we haven't done a lot of nitriding with it, the ones we have done came out well.

[betts]

I would also say that Jack's 8620 suggestion is good, if you want to case harden. Its hard to beat. But small parts may be a litle difficult to keep the movement down.

[Bruce Caulley]

Thanks Dean, Jack.

 

Bruce