Titanium Content in INCONEL 600

[FurnitureGuy]

Good morning...

We have received some Inconel 600 sheet for a job we are getting ready to fabricate. The material was purchased to ASTM B186. CMTRs (verified through PMI) show a Titanium content of up to 0.27% depending upon the sheet. Additionally, the Cobalt percentages are up to 0.52%.
Per the specification, there should, theoretically, be no Titanium or Cobalt in this material.

Does anyone know the effect these elements have on Inconel 600? Specifically: weldability, formability and any effect on the corrosion resistance.

Thanks in advance!!!

Cheers!

Mike


Michael Thompson
~~~~~~~~~~~~~~~~~~~
No honey, it's not the garage... it's my shop.

 

[EdStainless]

These elements weren't added intentionally, they came from using Ni based areo-space alloy scrap in making the heat.
The Co is no problem at all.
The Ti at these levels shouldn't be an issue. There are many Ni based alloys that are welded with higher Ti levels.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[FurnitureGuy]

Thanks EdStainless... I appreciate your help!!

Cheers!!

Mike

Michael Thompson
~~~~~~~~~~~~~~~~~~~
No honey, it's not the garage... it's my shop.

 

[arunmrao]

Ed Can you please tell,what percentage of scrap is generally used while making these alloys? I thought,that only secondary processors casting foundries used scrap.

Learn the rules,so you know how to break them properly.
Dalai Lama

_____________________________________

 

[mcguire]

Ed's answer makes sense, but I wonder how any Ti introduced as scrap would survive the melting without being oxidized after which it would not be reduced. This, then, implies that the Ti is there as oxide or complex includions. 0.27% Ti would imply about 1% by volume inclusions, which is extremely dirty for such an alloy. That makes me wonder if it wasn't a deliberate addition, and I know what Ed thinks about such things.
I am suspicious. That much Ti implies that the producer is either not a very good melter/refiner or not a very rule-abiding one.

Michael McGuire

http://stainlesssteelforengineers.blogspot.com/

 

[EdStainless]

My response didn't post. I'll try again.
With stainless steels and Ni alloys the scrap charge rates are at lest 75%. For commodity grades like 304 it reaches 95%.
My hunch in this case is that they have added some scrape from an aerospace grade that has 3-6% Ti. That would also explain the Co. These alloys have very low C and may have been added after oxygen blowing in order to raise the Ni. Of if the charge materials were low enough in C, Si and so on then the metal may not have been refined at all.

Metal recycling is odd sometimes. Plain and low alloy steel from integrated mills actually contains a lot of virgin metal because of the iron (blast furnace and DRI) that is used. The mini-mills (Nucor) are 100% scrap, and everyone else is somewhere in between.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[MSUKeith]

I agree with Mr. McGuire on this one - something doesn't sound right. At the very least you should:
- Get the orginal mill cert from the producing mill, not a retyped cert from a intermediate processor or service center. This will confirm that the mill produced it and shipped it as Inconel 600 and was not re-labelled because it 'met the chem spec'. Also confirm the C level.
- Get a cross section cut and polished to look at microstucture. Ti will form carbide/nitride precipitates that disolve during welding and do not have time to reform. Carbon and nitrogen in solution can have negative effects on weld quality.

I believe the mill should also be an approved licensee of Special Metals to call it Inconel, right?

 

[EdStainless]

Most likely it is alloy 600.
Knowing the source would be interesting.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[mcguire]

Thinking about this one some more, I find this level of titanium is too high to be inadvertant. This is enough titanium to probably fully stabilize this alloy, i.e. tie up all the C and N.

I wish someone from Special Metals would reply to this. I found a paper written by Special Metals people who cite significant titanium in alloy 600 made by them. I cannot explain the apparent contradiction with specs but clearly this addition is deliberate.
The link is below.

http://www.specialmetals.com/docume...blems in the Chemical Processing Industry.pdf

Michael McGuire

http://stainlesssteelforengineers.blogspot.com/