Titanium and Hastalloy service in high temperature

[UchidaDS]

I would like to use titanium to serve in a furnace-500C.
Not sure what properties (for example, titanium) I need to know whether it is suitable to use?
For example, the thermal coefficient...

I found out that Titanium is cheaper than Hastalloy at some point.
Need help...

 

[metengr]

Look at this information;

http://www.timet.com/datasheets-and-literature

Look at this information;

http://www.specialmetals.com/index.php

Compare and contrast.

 

[EdStainless]

Ti have very low strength at elevated temps, and 500C is very hot for Ti.
There are Ti alloys that can be used at higher temps, but they get very expensive.

What characteristics are you interested in?
Why Ti vs Alloy C?

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Plymouth Tube

 

[btrueblood]

One property to consider would be the rate of oxidation of the metal (for instance, titanium will react rapidly with oxygen in air above 1200 C, and with nitrogen at 900 C, etc.)

 

[UchidaDS]

Yes, titanium will be cross out from the list.
Now I choose SS316 base on "Recommended Material for furnace parts and fixtures" and I am "familiar" with it.
I refer to this book: Heat-resistant Materials edited by Joseph R. Davis
But if you guys have more inputs/recommendation, please let me know.

Thanks guys!

 

[metengr]

Without knowing the specific component(s) for the furnace, the new material choice is reasonable. The other is 309 stainless steel, as well.

 

[XL83NL]

310 maybe

 

[EdStainless]

in order of strength at temp and general resistance to oxidation damage
316, 309, 310, 330, 800, 600, and then other special Ni alloys.
It all depends on how much stress is involved, will the temperature cycle (and how quickly), and what impurities are involved.

And don't build the structure too rigid. With temperature cycling parts will either distort or fail. It is better to have distortion.

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Plymouth Tube

 

[btrueblood]

Ed, to be clear, your list reads in increasing strength/oxidation resistance from 316 (low) and improving (better) as the list goes on?

 

[UchidaDS]

Where can I find this information regarding the relation of strength/oxidation resistance?

 

[metengr]

http://www.nickelinstitute.org/~/Me...tureCharacteristicsofStainlessSteel_9004_.pdf

 

[EdStainless]

Yes, in increasing order.
The doc linked by Metengr is the real deal.
You need to balance fig 6 (strength) and table 5 (oxidation damage).

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Plymouth Tube

 

[UchidaDS]

Thanks!!

 

[UchidaDS]

If I request to fabricate a part that made out of 309 or 316, for instance, are these material annealed or not annealed by default?
Meaning that is it all the material had performed annealing before selling it to customer?

 

[btrueblood]

In terms of cost, you will find it cheaper to buy those alloys "as wrought" or "as rolled" or "as drawn". You can get annealed material by specifying it, but it will not likely be a default condition, nor is there any such thing as a default condition. You can guarantee that if you want something and don't specify it on the drawing, you will likely get something else - Murphy's law.

 

[UchidaDS]

Based on the reading, it seems that the fig. is stated as "annealed".
How about cold rolled and hot rolled? Or it doesn't matter of the raw process since annealing will do the job (stress relief)?

 

[EdStainless]

For elevated temp service you really want to use annealed material. Because in service parts of the material may be stress relieved resulting in significant variations in strength. This can lead to severe distortion and accelerated thermal fatigue.

Each ASTM product spec has a required condition. For sheet and plate annealed is by far the most common. Long products (bar and structurals) can be ordered both ways. (sheet can also, but that is very special)

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Plymouth Tube

 

[UchidaDS]

I am not familiar with the heat treatment process.
Let say if I have a part and machine it to size. Material is 304SS (don't know it is annealed or not, how it is made from raw, etc, because not specify in the drawing).
It had about overall of .300" thick, width is about .500" and 12" outside diameter with some complex shape.
I want to hold the flatness and some other tolerance, if I annealed this part, will it change the form (in terms of tolerance, not about the phase)?
And call it for Full Annealing, Process Annealing or Stress Relief Annealing ...?

 

[EdStainless]

There is no stress relief of stainless steel, unless you don't care about corrosion resistance.
All you can do is full solution anneal.
What is critical is the uniformity of the cooling.
If dimensions are critical after some thermal cycles,
the piece should be annealed before machining, maybe again after rough machining.
And then maybe even again after it is done.
Yes you will get distortion. Variations in section thickness almost guarantee that you will.

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Plymouth Tube

 

[moltenmetal]

304 is a better choice for high temperature oxidizing services than 316, as well as usually being cheaper. The Mo content does you no good and can do some harm. H grade for creep resistance above 1000 F.

The issue with Ti isn't reduced strength per se- it's reduced ductility due to oxygen and nitrogen pick-up at elevated temperatures over the longer term. Piping code uses are limited to 600 F (315 C) for this reason.