mar aging 300 steel? 2

[mfgenggear]

any help here would be appreciated

I am interested in the amount of actual contraction after heat treat.
according to the material suppliers material data
the material contracts .001 in/in after aging.

Please advise if any one has actual experience with this material.

Thanks in Advance

 

[metman]

mfgenggear,

Yes have had actual experience with this material but not with respect to volume change from heat treat.

Contracts? Are sure it is not expands?

We had a 4" dia splined shaft AISI 4340 carburized and heat treated that was failing from fatigue and scrambling a $20,000 gear case. I replaced the 4340 with 300 maraging. This doubled the life from three months to six months but eventually had to re-design for larger cross section. This was for an underground coal mining machine.

 

[mfgenggear]

Metman

Interest info.

was the shaft finished then heat treated?
if so how much dimensional change was there ?
I am interested in the spline data before and after
heat treat.

Do you know what the tolarance the spline shaft was held?


Thanks in Advance

 

[israelkk]

Low alloys steels such as 4340 that are heat treated for higher strength by quenching do expand when heat treated. However, PH steels and Maraging steels which are hardened by aging treatment contracts/shrinks after heat treatments. This is a well known property and should be taken into account when precise dimensions are involved.

The best practice is to machine/grind the accurate dimension after heat treatment.

 

[mfgenggear]

Israelkk

I understand but there is a limit to how many dimensions have to be remachined when it is 59 min HRc.

Depending on the configuration i suspect this material will actually contract approximately .0003-.0005 in/in.

We make lots of parts from AISI 9310, 4340, Nit 135, H-11, M-50 and so on but not many from Maraging 300. so according to the Material Data. it contracts .001 in/in so at 4.00", so it changes dimensional .004 right!!
well not allways, if my tolerance is +/-.002 to +/- .005
all over.
then I do not want to remachine all the attributes
due to cost.

I will make some dummy parts, then insp before and after heat treat. and record my data.

I was hoping some here has worked with this material before.

Thanks in advance

 

[israelkk]

mfgenggear

Each batch and heat lot of Marage 300 will behave differently. Some will shrink 0.0005 in/in but other batches of material in the future will shrink 0.001 in/in. Therefore every time you manufacture parts from Marage 300 you will need to do tests. If this is an acceptable approach it may work but I an not sure it is more economical especially for line production.

If your dimension tolerances are +/-.002 to +/- .005 you may use final machining only for the +/-.002 dimensions assuming you will machine the +/- .005 to +/- .003 before heat treatment.

One more issue to take into account is the aging process if not produced under vacuum or inert atmosphere will create heat tint on the part surface. If a surface protection against corrosion is needed the removal of the heat tint may change the dimensions due to material removal. Marage 300 is not a stainless steel it will corrode without surface protection.

 

[mfgenggear]

Israelkk

I apprecieate any information that is given, because
learning the hard way gets expensive from deviations
which are not acceptable. so your advise is so much apprecieated. Sometimes in manufacturing we walk the fine line. I do not really like too and I like to stack it as much as possible in my favor.

This material apparntly has Titanium with Co.

Thanks in Advance.

 

[mfgenggear]

O yes one more Item I forgot to explain is
when parts are case harden which this part will have a case harden gear, which by design it will be difficult to machine .But can be done, the part is limited on the stock removal, for example .005-.010 total case depth (Nitride).
stock removal permited will be .0015-.003 per surface
if case depth is held to .008-.012

so if I do not machine this part to the correct size
and if the part contracts more than stock I have left.
I'am done parts are scrap.
This is just one example of many, so this is generally
what we as Manufacturing Engineers have to manage and
anticipate.

 

[metman]

mfgenggear

.005-.010" case depth seems like a lot for Nitriding. My experience has been about .002 case. However, it just requires longer soak time which adds up, Nitriding being a long process anyway.

Our spline tolerances were based on SAE standards (SAE used to publish a book about 1/2" thick devoted to splines with beautiful drawings and tables). Also the machining and heat treat were performed by a sister facility with gear making capacity and an on-site metallurgist. Therefore we merely called out final properties and tolerances on the drawing.

The cost of 300 maraging is significant and therefore a sample cut from the same batch and processed to determine actual shrinkage, as you have suggested, is justifiable.

 

[mfgenggear]

Thanks to all for the help

 

[mfgenggear]

follow up to this thread.

the material contracted approximately .0009-.0015 in/in

linears .001-.0015 in/in
diameters .0009-.0012 in/in

average = .0012 in/in

that said it was using geometry simular to the part.
aged, then masked, then nitrided .
HTH

Mfgenggear.

 

[itsmoked]

Thanks for getting back mfgenggear.

Not too much change! That's great.

Slight hijack: Where are you finding this 300? I spent a week looking for a few pounds and could only find people willing to sell me whole batches of multiple tons.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[mfgenggear]

itsmoked

Purchased by our material buyer from Fry Steel
from Santa fe Springs, California, USA.

Note : fry steel should sell you what you need.

change was enough to cause some stress, for example at 5 inches long, the parts change (contracted) .006 total
and in my opinion it gets to expensive to remachine all surfaces so I adjusted accordinly.

Take Care

 

[itsmoked]

Thanks.

Keith Cress
kcress -

http://www.flaminsystems.com