High Temp Metallurgy Resources

There are a host of variables that need to be considered for understanding behavior of steel at elevated temperatures.

Obviously the temperature; whether or not short or long term and steady or intermittent time at temperature, and application of load.

If you put the gun to the head of my wife's dog, and I liked my wife and dog today, (Just kidding folks) I would use the percentage of elevated temperature strength compared to room temperature strength, plotted as temperature increases. If two indicators are available, Creep can be plotted as a time plot; stress- creep strain plot, Stress time plot, or probably best way, isochronous total strain vs Stress curves.

Other tests to look for include short term elevated temperature tests ASTM E21, long term elevated temperature tests ASTM E139, ASTM E292;, short and long term tests following a long term exposure to elevated temperature (look for test for evidence of over tempering or spheroidization, loss of section by oxidational flaking), thermal shock tests, time dependent fatigue tests and simulated seervice qualification tests.

For applications I would consult the appropriate AMS, ASME, or ASTM specifications.

The AISI designations for steels intended for elevated temperature service have three digit grade identifier beginning with a 6; AISI 601 corresponds to AMS 6304; AISI 602 corresponds to AMS 6302,6385,6458; AISI 603 corresponds to AMS 6303, 6436; AISI 610 corresponds to AMS 6437 and 6485. All of these documents should give you important info you seek.

As a working metallurgist, I would also offer you one CRITICAL warning: There are specific embrittlement ranges to beware of :

For regular steels, 230- 370 degrees C is blue brittle range.

For fine grained High Chrome stainless steels, 400-500 Degree C range can become embrittled with the development of a second cr rich ferrite phase as opposed to the normal iron rich ferrite. Some stainlesses (i don't remember which, can also develop Sigma phase embrittlement when held in 560 degrees C to 980 degrees C range for long perods. When sigma phase stainlesses cool below 260Degrees C, they lose all toughness and become Freakingly notch sensitive.

If you are going to be working in this field, I would suggest the ASM Metals handbook series. (mine are all about testing and processing rather than the ones that talk about engineering applications, sorry).

The one book that you should own personally is the metals handbook desk edition. see link below. Mine is first printing, 1984, and has at least 60 book marks or placeholders. Very well worn.

If you purchase the metals handbook desk edition let me know and I will tell you where to find the good stuff.

Don't wait for the new edition, get the old one used:

http://www.amazon.com/Metals-Handbook-Desk-2nd-Davis/dp/0871706547

milo

Code related: ASME BPVC Section II - Part D

General reference: MMPDS-01; http://www2.tech.purdue.edu/at/courses/at308/Technical_Links/MMPDS/OptionsMenu.pdf

(that is a linked/bookmarked pdf ... click away ... or find that document elsewhere)

Just remember that most all steels start to lose a significant percentage of their strength as tempertures rise, different alloys lose it at different rates and a lot of it has to do with the Jominy hardenability of the steel and the amount of cold work that has gone into the part. Some alloys are VERY sensitive to temperature. 25% Cr Duplex Stainless alloys for instance are particularly sensitive to temperture, losing a whopping 23% of their strength between room temp and 150 degrees C.

First you need to define what you mean by "high" temperatures. Are we talking 300 degrees F? 800? 1200? Steady state or cyclical? and what kind of environment will it be in? Oxidizing? Neutral? Reducing?

There are a lot of things that go into this equation. I would suggest that if you are looking at high temp service you should be considering alloys that don't have high temp issues such as Cobalt, Nickel or Titanium alloys. Yes they cost a whole lot more (Nickel prices are fairly depressed right now however.) but the cost savings from fewer failures in service can offset that up front cost by a large amount depending on the situation. There is a reason why the hot sections of jet engines for instance are made from Nickel alloys.

I'm really looking for general references that I can review any time one of these questions come up.

In this particular case, we had a problem with some of our heaters so I started to look into it. The design temperature was 750F and we had been operating around 1200F. As it turns out, we were still within the acceptable stress range based on API 530 (from the temp/pressure combination), but we were also in the sensitization range of 316 SS. Luckily, I stumbled across this while evaluating the situation but I think that was more luck than anything else. What I would like is some kind of manual that I could reference if I run into another situation like this.

For the heater I'm working on now, the design temperature is 700F (calculations are 30 years old) but my calculations show that it is good for up to 900F based on the low design pressures. I want to make sure that carbon steel is okay to operate in this temperature range but I would prefer not to start another CR4 question every time I run into this problem with a different metal or temperature.

Obtain a copy of High-Temperature Property Data Ferrous Alloys. It is an ASM International Publication ISBN: 0-87170-243-6

Steel structure changes drasticly at the transformation temperature(s). These temperatures are publicized .

PEbob