Author Topic: Cast iron ''SPRUES'' can they be of use to the model machinist?  (Read 15231 times)

Offline MuellerNick

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Re: Cast iron ''SPRUES'' can they be of use to the model machinist?
« Reply #15 on: August 13, 2013, 01:47:44 PM »
Quote
What does it actually do to the metal by allowing it to oxidize?


It does nothing. Absolutely nothing. Except waste time and some "Oh! Wow!" from those who believe tell-tales.


Internal stresses in a casting are gone after a week. The fastest decline is within a few hours.


Yes, there are stories, that BMW, during their F1 engagement during the turbo area, bought old castings. And that they buried them and that they peed on them. And whatever. Just to build some mysteries around their success. Others do that too.


Nick

Offline derekwarner

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Re: Cast iron ''SPRUES'' can they be of use to the model machinist?
« Reply #16 on: August 14, 2013, 12:41:09 AM »
mmmmmm...strapping a casting down to a steel plate in the back of a truck & take the plate for a 50km ride on a bumpy road  :cartwheel:  :ROFL: will progress the stress relieving  function ....Derek
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Offline firehazard

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Re: Cast iron ''SPRUES'' can they be of use to the model machinist?
« Reply #17 on: August 14, 2013, 12:33:32 PM »
Hi,

it is my understanding that there are two different reasons to heat treat iron castings.

Stress relief and machinability.

Stress relief treatment is kept below 550 degrees C and the old rule is one hour for every inch of thickness followed by a slow cool down.

To improve machinability heat to 800 degrees C quickly and a slow cool down. This will break down the carbides but sadly reduces the strength and hardness of the iron.

"Modern Foundry Practice" which seems to be from the late forties is a good book if you can find it.

take care

John

Offline Ian S C

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Re: Cast iron ''SPRUES'' can they be of use to the model machinist?
« Reply #18 on: August 14, 2013, 02:47:29 PM »
The manager of the retail shop that I bought my Taiwanese lathe from had just returned from the factory in Taiwan, and he was telling me about it, out in the yard were piles of castings ageing, one large stack labelled Colchester England,  He asked the factory manager about these, and was told that they stayed there 5 years,  I think their own castings around 3yrs.  the Colchester stuff was lathe beds.  The castings were partly machined.     Ian S C

Offline MuellerNick

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Re: Cast iron ''SPRUES'' can they be of use to the model machinist?
« Reply #19 on: August 14, 2013, 03:14:19 PM »
I highly suggest reading this PDF: http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=AD0620556
If someone has a research (and not just wild claims by hearsay), I'd like to read it. Even if it shows the contrary.


Nick

Offline tel

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Re: Cast iron ''SPRUES'' can they be of use to the model machinist?
« Reply #20 on: August 14, 2013, 09:49:27 PM »
Well, regardless of whether it works or not, it was most certainly the practice of the car manufacturers here - I have seen the (row upon row upon row of) castings sitting out weathering myself, aat more than one plant. These days I believe they use an artificial aging process.
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Offline Dan Rowe

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Re: Cast iron ''SPRUES'' can they be of use to the model machinist?
« Reply #21 on: August 14, 2013, 10:07:53 PM »
Nick,
I did read that paper several days ago. It does not mention the method that both Bob and I mentioned and that is to take a SURFACE cut and leave the casting to age out doors. In Bob's case he did say under the bench.

I checked my marine engineering books and the internet and I can not locate a source of that method so I must have gotten the information from a Sulzer field service rep. So that does make it hearsay but now at least 3 folks or more have mentioned partially machined castings in a field so this is or was common practice for some operations.

Dan
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Offline ths

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Re: Cast iron ''SPRUES'' can they be of use to the model machinist?
« Reply #22 on: August 14, 2013, 10:18:38 PM »
I don't think that there's anything magic about 'outdoors', it's just cheaper than building an 'indoors'.

Offline Dan Rowe

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Re: Cast iron ''SPRUES'' can they be of use to the model machinist?
« Reply #23 on: August 14, 2013, 10:38:39 PM »
The paper referenced by Nick does have a test of heating and cooling cycles with dry ice and then heating to 2200F for four cycles which had a very small improvement but the casting was not given a surface cut before the cooling/heating cycles.

The castings I was talking about are large cylinder liners that is 900mm bore and 1550mm stroke so yes it is a cheaper solution to use an empty field than to build another building.

Dan
ShaylocoDan

Offline Maryak

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Re: Cast iron ''SPRUES'' can they be of use to the model machinist?
« Reply #24 on: August 15, 2013, 12:32:18 AM »
Hi Guys,

Without getting at all technical...............no major company seeking to maximise their profit margin is going to adopt a process which is not going to give a positive benefit, be it buying a field, producing parts 5 years in advance of them being required; etc.

For the technically minded.

http://www1.eere.energy.gov/manufacturing/resources/metalcasting/pdfs/age_strengthening.pdf

Best Regards
Bob
« Last Edit: August 15, 2013, 02:25:07 AM by Maryak »
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Offline firehazard

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Re: Cast iron ''SPRUES'' can they be of use to the model machinist?
« Reply #25 on: August 15, 2013, 01:15:33 AM »
Hi,

that was a very interesting paper.

This discussion has strayed quite a long way from the initial question.

If I was pouring a component for serious use I would not use straight grey iron. Just 1% nickel in the mix makes a huge difference. I suspect the components people have observed, or just been told about may not be plain old grey iron.

The famous "Meehanite" people have been modifying cast iron and its properties for a good while but they don't tell all they know.

"High Duty" iron is not the same thing at all as plain grey iron and there is an extensive body of literature dealing with the possibilities. As well as the proprietary recipies of the Meehanite people and many others. Including engine manufacturers.

Precipitation hardening is not just confined to aluminium and its alloys.

Take care

John







Offline MuellerNick

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Re: Cast iron ''SPRUES'' can they be of use to the model machinist?
« Reply #26 on: August 15, 2013, 06:51:55 AM »
So, there do happen two things:
Stress relief and strengthening. Both occur within 10 days.


If you have roughed a cast part, put it anywhere for a week and then do finish machining.
But it is absolutely impractical to completely grind off the outer skin of say a lathe-bed or an engine block.


Age hardening of aluminium alloys is a well researched and documented process. But also, it is a quite different alloy than cast iron.


Nick

Offline kellswaterri

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Re: Cast iron ''SPRUES'' can they be of use to the model machinist?
« Reply #27 on: August 15, 2013, 11:00:21 AM »
   Crikey!!! some thing new learned every day...I will take a little from each post and proceed to my shed...
                                                            Thanks all,
                                                                      John.

Offline steamer

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Re: Cast iron ''SPRUES'' can they be of use to the model machinist?
« Reply #28 on: August 15, 2013, 11:01:53 AM »
Gentlemen,

I have seen both methods used before in real life...hell by the same company!  Heald Machine.

New castings had the following notes on them if they were "Iron"

First.....NEVER EVER ask for "Cast Iron"....or you will get it!.....I seem to remember watching a 42" faceplate being turned and blowing up tools....When we investigated, you could see the outline of a railroad spike in the casting!....and that is what it was...and hard as glass too!

We would specify Meehanite GC-40
Meehanite is a process by which the iron was produced.  All that says is if you get iron to that specification, you will get the quality you want in a machine tool.
The GC-40 designation was Grey cast iron with a 40000 psi minimum tensile yield

The next note was the money shot though.

"Stress relieve to 220 BHN +/- 20%".....I remember that very clearly. and it was drilled into my head by the "Gray Beards"

Now if it was stress relieved, it was generally per the document that Nick is referring to, I remember it was at 1100 for one hour.    HOWEVER

We had a bunch of Meehanite machine bases for Heald 272A's sitting in the back lot stacked up for "seasoning".....well that's all well and good...but I seem to remember occasionally the floor having a problem them moving around during machining...not all...just some.

We also had a vibratory stress relieving machine rig....I even watched a machine base dropped from a crane on to the floor because it would "knock" the stress out......

I think if you have really good material, poured by someone who knows what they are doing, the stresses will be low to begin with.
Otherwise, I would use the navy recommendations.

JMHO.......your mileage may vary....professional driver on closed course........yada yada yada

Dave
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Offline steamer

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Re: Cast iron ''SPRUES'' can they be of use to the model machinist?
« Reply #29 on: August 15, 2013, 11:16:00 AM »
Additionally, Nick, I know I've bumped a straight edge and watched it curl up...and following the "generally accepted" practice of letting it "rest" over night have the curl come back  out

NO I can not explain that...but I am not the only one who has observed that either

As to getting the "skin" off....if the surface is in a chilled state, and hard, then a lot of stress will be relieved once it is cut off...but from the surface...not  necessarily from deep inside the part.

At that point it's a question of how thick the sections are..how it was processed and handled...I would say you may have better luck with the lottery than guessing the stress state of the casting in this condition.....I wouldn't want to build an important part of a machine tool or an engine with it.


Which nicely gets us back on topic now doesn't it...perhaps we should save our sheckles for good material to make important parts out of ...hmmmm?
 8)
Dave
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Damned ijjit!