50% Nickel cast iron ?

[Tmoose]

A 7000 lb casting is usually made of cast steel, or a mid grade ductile iron.
We are working on a used one.

Three Positive Material Identification (PMI) tests were done in one area of a machined surface.
The pre-cleaning as reported was pretty good, with one possible complication.
Repeating the tests now will be problematic.

Test results.
Si 2.57
S .69
Ti .19
Cr .06
Mn 3.48
Fe 42.39
Ni 50.63

Has anyone heard of such a material?

Searches for commercial materials with similar chemistry so far only come up with far fetched options. Powdered metal recipes, and parts with magnetic requirements.


The part is also pretty rusty, which strikes this rank amateur metallurgist as surprising with the high nickel content.

My first thought is we REALLY need to do a few more tests on freshly ground surfaces.
My second thought is the test surface was contaminated with Nickel, possible anti-seize compound from previous installation, or from the wire brush used for cleaning.
My third thought is such an exotic material may have been an (expensive) foundry mistake.

thanks,

Dan T

 

[btrueblood]

Is it possible you probed in an area that had undergone weld repair or weld surfacing? Ni-rod and similar high nickel alloys get spec'd for ductile cast iron repairs pretty often.

https://www.lincolnelectric.com/en-.../Pages/stick-electrodes-cast-iron-detail.aspx

 

[EdStainless]

Cr is what makes things stainless, so rust is expected.
The 36% Ni steels and cast irons for low thermal expansion rust easily.
Given that your device does not have calibrations for this range it could be a 36% Ni Ni-Resist casting.
At this Ni it should be non-magnetic, could have been part of a electromagnetic device.


= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy

 

[Tmoose]

Hi EdStainless,

" Given that your device does not have calibrations for this range "

I'll look into this.
The instrument's software display makes the claim the Fe and Ni results are within 0.2%.

thanks,

Dan T

 

[arunmrao]

Apart from the 36% Ni grade, there is also the 42% grade Invar. A 7000lbs casting in Invar is quite huge. The largest I cast, was about 1000kilos in Invar alloy.



"Even,if you are a minority of one, truth is the truth."

Mahatma Gandhi.

 

[TugboatEng]

As many times as that thing has broken I'd say it's time to start from scratch, regardless.

 

[Tmoose]

Thanks all,

Just as Btrueblood suggested, Recent indications are the PMI tests //may// have been done right on top of a massive weld repair.
And "coincidentally" the Ni and Fe results are relatively close to "typical deposited" chemistry of commercial cast iron welding electrodes.

Fancy that !?

thanks,

Dan T

 

[mrfailure]

I don't suppose you can remove material from a noncritical area of the casting so you can get an accurate quantitative chemistry, can you?

 

[TugboatEng]

You can see where a weld repair was performed between the 4th and 5th bolt holes from the right. A sample taken anywhere but there should give a better result. The left side has been repaired by metal stitching as well and also appears to have had a plate lapped over it. This casting is a mess.

 

The instrument's software display makes the claim the Fe and Ni results are within 0.2%.

The instrument's software display is lying through its pixels.

PMI is not chemical analysis; look up any of my old rants on the topic.



"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[EdStainless]

Or wait a little bit and one of us will go off on the subject again.
That number that they give you is based on statistics of how many counts it measured.
It has that precision, but it says nothing of accuracy.
There is no such thing as reliable standard-less XRF, there are too many interferences (some add and some subtract).
When we do XRF in the lab on a machine that has separate detectors for each element we are working with 10e4 to 10e7 more counts and we have real standards that we used to build calibration curves.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy

 

[mrfailure]

Besides chemistry, you should make a replica of the microstructure so you can tell whether you have cast steel versus ductile iron. That differentiation is necessary for any subsequent repairs.

 

[btrueblood]

:-/ Well, it's happened to me before, we buy a lot of DI castings and occasionally get one that looks odd. PMI is an easy test to confirm suspected welding of casting defects for us, where no nickel should be showing up. But at least those vendors try for a decent repair, unlike some who ship parts "repaired" with bondo.

 

[Tmoose]

No repairs for this casting.
I'm requesting a recount. ( New PMI on well prepared rusty chunk).

I think we are debating scrap value vs 1000s of US bux to ship the junk back to the customer.

Scrap value of 7000/2 = 3500 lbs of nickel = maybe $10,000 ± a lot
Scrap value of 7000 lbs of ductile iron = $350

 

[IRstuff]

http://www.online.stahlschluessel.de/SearchComposition.aspx

shows 28 alloys with roughly 50/50 Fe/Ni, but none with that high enough Mn or Si.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

faq731-376 forum1529 Entire Forum list

http://www.eng-tips.com/forumlist.cfm

 

[MagBen]

The shape and the size of the casting are unlikely a 50/50 (Ni/Fe) magnetic alloy. From other perspective, high Mn and Si implies this a cast iron product. In Fe-Ni system, it will be non-magnetic (low Curie temp <RT)only when Ni = about 10-25% Ni.

A easiest way to give you a proximate estimate is to use a magnet to full.
If not magnetic, it is Ni-resist casting with a lower Ni (<25%).
If it is magnetic, but not as strongly pulled as carbon steel, this is high Ni-resist casting.
If it is very strong magnetic like carbon steel, it is a cast iron.

 

[MagBen]

By the way, 50% Ni-Fe high permeability alloy can rust like a fire truck, can be easily corroded. Even 80Ni-Fe can be corroded in air. Ni alone cannot give you much corrosion resistance.

 

[gtaw]

I always send samples out for a chemical analysis. I never trust a PMI gun when a critical welded repair is necessary.

Is this suppose to be cast iron? Is it suppose to be a nickel iron casting? If it was ordered as cast iron, it seems doubtful someone made a mistake that is so costly. Nickel sure "ain't" inexpensive, so if someone inadvertently added that much to the mix, someone probably got their hind end handed to them.


Best regards - Al

 

[Tmoose]

Absolutely No repairs planned for this poor old casting. Her days are done.
I'm requesting a recount. ( New PMI on well prepared rusty chunk).

The interest in the material is I think because we are debating scrap value ( to be paid to the owner ) vs 1000s of US bux to ship the junk back to the owner so they can scrap it.

Scrap value of 7000/2 = 3500 lbs of nickel = maybe $10,000 ± a lot
Scrap value of 7000 lbs of ductile iron = $350.

I am not sure if a certified analysis will need to be provided to the owner to justify the check from the scrap yard. I bet they have scrapped these before.

Again, thanks all.

Dan T

 

[mrfailure]

You are worried about a couple hundred dollars for a real chemical analysis to know what you have and what its scrap value is? Real quantitative chemistry is worth it either way!