9Cr Carbon Steel @ High Temperature

[NickelMet]

Does anyone have information they could share on the tensile properties (yield strengths) and other mechanical properties for 9Cr low alloy carbon steel (in particular SA 335-P9) at elevated temperature (in excess of 1000°F)?

Thanks!
~NiM

 

[metengr]

The following is information that I had in my files from US Steel Corp back in the good old days. The mechanical property information does not specifically apply to SA 335 P9 but is as close as one gets, the alloy is USS 9, which is 9 Cr-1Mo;

Typical Tensile Properties;
@ 1100 deg F - UTS is 41 Ksi, 0.2% YS is 23 Ksi
@ 1300 deg F - UTS is 18.5 Ksi, 0.2% YS is 10.5 Ksi
@ 1500 deg F - UTS is 10 Ksi, 0.2% YS is 3.5 Ksi

Creep and Rupture Properties

Stress to cause 1% def in 100K hrs
At 1100 deg F, the stress is 5.8 Ksi
At 1200 deg F, the stress is 2.6 Ksi
At 1300 deg F, the stress is 1 Ksi

Stress to cause Rupture in 10,000 hrs
At 1100 deg F, the stress is 10.5 Ksi
At 1200 deg F, the stress is 5.5 Ksi
At 1300 deg F, the stress is 2.5 Ksi

 

[NickelMet]

Thanks Metengr for the information.

~NiM

 

[davefitz]

Please note that the alloy SA335 P91 ( Niobium modified 9 chrome) is usually specified for use at elevated temperatures. There are also other forms of tungstem modified 9 chrome also available (p92, P911)

 

[NickelMet]

Davefitz:

Thanks for the information. However, I'm investigating a runaway temperature failure. The normal temperature should never exceed 850°F and there is a good possibility the tubes I'm examining saw 1600-1700°F. (NOT a pretty sight...)

~NiM

 

[SMF1964]

At 1600, the stuff should be like taffy and I would expect it to have failed at some temperature below the lower critical and before it reached 1600-1700°F.

 

[NickelMet]

Let's just say that what remained did look like pulled taffy with plenty of alligator skin and stretch marks, black as coal.

Also, when I mention a temperature, I'm just guessing at the firebox temperature. The actual tube temperature may have been cooler by a tad bit, but not much. If anyone has good information regarding temperatures and failures in this material, I'm all ears.

Thanks everyone.

~NiM

 

[metengr]

This sounds like either superheater or reheater tubing that had become bottled up (inadvertent isolation) during service or shortly after start-up, and resulted in short term overheat. Your exact description of the failed tubes sounds like an incident I had experienced several years ago on a twin furnace, radiant reheat power boiler.

 

[NickelMet]

Similar situation Metengr, but not boiler tube related. I really can't go into details due to confidentiality agreements and such. However, it is a new one on me to investigate, so I'm scrounging for information.

~NiM