QPQ, Tenifer, Melonize etc. trying to rework

hello forum

I'm stuck with the job of trying to polish some parts into tolerance that have been QPQ heat treated.

I'm using fine sandpaper and/or scotch-brite pads to bring down diameters .0005, this is a horrible job. Is this even safe for me? I'm not sure what hazards there are but the black finish is all over my hands and in the air.

The problem now is that the diameter of QPQ finished parts is supposed to be .999-1.001 and they are 1.002. bringing down the diameter a full thousandth completely wipes the black finish off.

I guess the black finish is what gives the parts corrosion resistance and lubricity. Would this be restored by black oxide? If that's not acceptable, would it be possible to have the heat-treaters just re-dip the final Quench in order to replace the original properties?

Polishing these to size sucks. If it's unhealthy and nonconforming, that would be THE sucks.

by the way

does anyone know of a good book about heat treat distortion of metal?

--Erik

Erik, I have no idea what QPQ is. We do a lot of different HT processse and I've never heard of it. As far as the book goes, there's lots of reading material out there, you have to hope your heat treater reads the same stuff you do.

We do a lot of ion-nitride and think we have the process down. Every now and then, we loose a part because of size. When the heat treater got stuck for a couple of high $ parts, the parts came in right for a while.

All of our surface treatment & plating is sent out. There isn't a month that goes by that we don't have a problem with one or the other. About a year ago, we had a part that came back from the plater with too much ENC on the bore. We sent back to strip and recoat. They damaged the 4 finish the second time. So we sent it back to strip, back to our shop to rework, and back to the plater. They had finished the part and were bringing it back to us. Their driver was in a hurry and negected to tie it down in the pick-up. You know the truck, the one with no tail-gate.
JR

haha

thanks for the good reply JRIowa

I asked our quality manager a question today and if you read this I'll be asking you too... let's say a guy spent his whole career on heat treating steel and had a metalurgy degree, could get his doctorate, had a knack for the science... could that man take a material cert and look at the composition of 1018 and send it to case hardening and predict how much it'll shrink or grow?

That's what QPQ is basically. Ferritic Nitrocarburizing. it's salt bath Quench, mechanical Polish, salt bath Quench. I guess the case depth is like .001-.006 and improves torsional resistance of 1018 by 100%. It is black, supposed to be very free-running, and has better corrosion resistance than chromium or nickel plating !!!

But +/- .001 then QPQ is a pain

let's say a guy spent his whole career on heat treating steel and had a metalurgy degree, could get his doctorate, had a knack for the science... could that man take a material cert and look at the composition of 1018 and send it to case hardening and predict how much it'll shrink or grow?

Click to expand...

We've got 2 of those guys. IMO the answer is NO!!!!

The difference is, you and I would "wag" it. They "EWAG" it (Educated wild assed guess).
JR