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heat treating 17-4PH

andy pullen

Hot Rolled
Joined
Dec 15, 2003
Location
Bel Air, MD
I have to make some cylinder rods for some hydraulic cylinders that go in an incinerator. I'm thinking of using 17-4PH and getting it heat treated for wear resistance and then hard chrome plated for durability.

How hard does this grade of stainless get when heat treated? I know the tensile strength goes up quite a bit. And is it machinable in the heat treated state? I can buy prehardened 17-4 by the way...

Thanks for your time,

andy Pullen
 
Andy,

"How hard does this grade of stainless get when heat treated?" 65Rc ;)

"And is it machinable in the heat treated state?"
At 65Rc it would be mighty tough to machine. :(

If you buy the prehardened stuff you can work with it up to 40-45 Rc after that forget it. :(
I would think 35-40 would be good enough for cylinder rods. :D Be advised even in its annealed state 17-4 is a pain to machine. :mad:


Scott
 
why not buy some induction hardened and be done?

why do you need it heat treated for wear resistance? thats what the chrome is for.

I made tons of hydraulic cylinder shafts and never used stainless. I dont see any benefit in using it.
 
The rods are going into the ashpan assembly on an incinerator. It's a dirty, corrosive environment. The steel rods that are in there are corroding after about 6 months. The chrome actually starts to deteriorate after 6 months and that tears up the seals. Then, they start to get scored.

I was thinking of induction hardened rods, since they work so well on construction equipment. But, I don't know how it would hold up in that environment corrosion wise....

AP
 
Hardening this would be good, chroming it for your use maybe a waste. I have HT'd things to Rc65 and a few things above that, they get brittle or will shatter if the forces exerted are powerful enough, such a mechanical stalling or a broken part gets in the area that this is. Sort of like getting a shattered ring in the cylinder of an engine, can do a lot of damage.

Jerry
 
Johnoder is correct. 45Rc is about max according to the literature I got recently. Condition H900 is the hardest at 45 Rc, and it goes down from there. Corrosion resistance when hardened is supposed to be as good as type 304SS.

I think it might be a good material to try under those conditions. How much heat will the rods get in service?
 
Andy,
You might check into salt bath nitro-carburized cylinder rod material. Its used heavily these days on things like highway snowplows and such that are subjected to salt and abrasion, because it will leave hard chromed rod in the dust in corrosive environments like that. Nitro Bar is one of the trade names for it. The cost is about 10% more than induction hardened chromed cylinder rod material.
 
Thank you all very much....

Munch,

I've worked with that nitro stuff. I may have a source for it. That might be worth a try, too.

andy Pullen
 
Andy, 17-4 condition H-900 has a problem with corrosion stress cracking. Condition H-1075 is far less likely to have this problem. We do not chrome 17-4 for shaft work. If we need more corrosion resistance, we usually go to Nitronic 50 (or 22Cr-13Ni-5Mn, a trademark of Carpenter Technology). Buy the stuff as TGP shafting.
JR
 
I run a lot of annealed 17-4 and it's around Rc40. It goes out to heat treat after it comes off the warner & swaseys. Dunno how hard it comes back at.
 
We cast some mill guides from this material a while back. The customer brought them back because his machinist couldn't machine them. We then recast the parts out of 304 stainless, he got them machined then shipped to the mill. The mill rejected them for being too soft. So I guess we will have to make them out of the correct material (again) and wish the customer good luck in machining them.
 
Perhaps Custom 455 S.S.? According to my Carpenter book resistance to stress-corrosion cracking is very good and improves as the precipitation hardening temperature is increased. Hardness ranges from about Rc50 at H900 to about Rc40 at H1050.

Mike
 
According to the Crucible website(both my Crucible heat treat books are at work) their 17-4(they refer to it as CSM 21) won't get above 40-43 HRC. They claim that in the annealed state(solution treated) that it is 32 HRC. This stuff is NOT fun to machine. They also have another grade of 17-4 that they've modified for easier machining(maybe) called 174 SXR. I know 17-4 shinks in the hardening process and I'm assuming that the 174 version will as well.

The link to the 17-4 page is here:
http://www.crucibleservice.com/eselector/prodbyapp/stainless/csm21s.html

And the 174 SXR page is here:
http://www.crucibleservice.com/eselector/prodbyapp/stainless/174sxrs.html

Up to a certain point material hardness is good, but hardness is only the resistance to deformation. After that point, the material might become brittle and may fracture or shatter. I'd talk to a steel mill(or more than one) and try to match corrosion resistance with toughness for your application. Wear resistance will also be an issue I'm sure, so be sure to include that in your discussion with the steel rep.
 
Andy... think about this for a moment... If its your equipment you are trying to fix, forget this posting.

If its a job your doing for some else for no pay but warm tingles to your heart, ditto.

But if your getting paid to fix this problem why are your trying to make the fix permanent? If you use regular product everything will need to be replaced again in six months - and you'll get paid again! Positive cash flow is never an item to decline... I said that!

Be well & Happy!
 
Thanks for all the replies....

Let me give some background to those who don't know me. I'm the machinist for the maintenance directorate at Fort Detrick, MD. I have to work closely with all of the departments and plants here on post. When the supervisor at the incinerator says he wants to icrease the life of his equiptment; then that's what we do. His dampers were made of mild steel and they were rotting away in 6 months. The dampers are now made if inconel and they still look as they did the day they were installed 12 years ago. Just dirtier....I want to make life easier on my coworkers who actually have to do the work in the field (which I have to assist with on occasion). Every job at the incinerator is dirty, nasty and hot. And, the millwrights hate to work there. Especially, in the summer.

The damper on the #4 incinerator is down at the moment, due to an explosion. Some fool put a 20 pound propane bottle in the trash and it slipped through and into the fire. The force from the blast broke the shaft that the damper rides on. I'm replacing the shaft with Nitronic 50 shafting. It was originally made of what looks like mild steel and it had been in there for about 3 years and about 1/3 of it's rotted away. Luckily, nobody was hurt. And it's been reasonably cool this week. Hopefully, when I get the new shaft made it will be raining when it's to reinstall the damper.

Repeat business is not the issue with most of what I do at work. I like to fix it right the first time. If, I can make things so they will double or triple (or more) the life of something; I'll do it. It means less of the nasty work for everybody else and gives us time to get the other work done.

I know, you're all thinking "lazy government employees". Sure, we have our share of those. But, we have a core group of dedicated people, too.

I appreciate all of your inputs.

Thank you,

Andy Pullen
 
Andy,

Thank you for the clarification. Seeing as how all of us contribute to the running of Fort Detrick via Uncle Sam's Irrupting Redundant Service (IRS), I appreciate you are trying to come up with a more durable fix, i.e., less costly to all of us over the long haul.

My apologies for the assumption.
 
DBGUY,

Don't worry about it. I worked in industry for 20 years and I don't believe in throwing money at a problem. If there's an inexpensive way to repair something the right way; I want to find it. You won't see me buying a $400 wrench or toilet seat. There aren't enough people like me in government service, unfortunately...

There are some GSA certified vendors mark their prices up for the goverment. We had one pair of salespeople in here from one company about 2 years ago. The man had one of those oily personalities. Slick salesman type. He's going on and on about these wonderful tools he's selling. The first thing he pulls out are combination drill/taps. (The woman's already writing up the order while this is going on.) I tell him I don't use that junk and that I don't want them. She looked at me like I called her a crack whore...and had to tear up the sheet she was working on. I told them I didn't want anything they had and had to get my boss to tell them to leave.

I'm digging for carbonitrided shafting at the moment. The best I can find has a 6 week delivery.

Andy Pullen
 
Andy,
Any idea what the service temperature is for the shaft? That should be one parameter guiding material selection. Also, if 17-4 PH looks like it might work, be sure to check out passivating the part after heat treatment.
Rich
 








 
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