Can somebody point me to a reference that has 12L14 strength properties for 300 and 500 deg C? A curve of yield strength vs temperature would be ideal.
12L14 will be comparable or inferior to any low carbon steel such as 1018, 1020 etc.. Therefore, try to find data for those alloys.
MIL-HDBK-5J quotes for 1025 : "2.2.0.3 Environmental Considerations — Carbon steels have poor oxidation resistance above
about 900 f to 1000 F. Strength and oxidation-resistance criteria generally preclude the use of carbon steels
above 900 F..."
One thing to consider is the 12L14, being a leaded steel, will sweat lead at those temperatures. You can have issues with pressure tightness in plugs or fittings if there is lead segregation at the center.
Although the lead in 12L14 melts at ~326 oC, it doesn't segregate out, at least in short term heatings. With properly manufactured 12L14, the tiny lead globules wet and remain attached to well-distributed MnS inclusions. Thus, 12L14 can be annealed (~920°C), normalized, case carburized and forged (1300°C). There are also heat treatable leaded alloys such as 43L40 & 86L20, so the lead must remain dispersed for chemical reasons. Welding is a definite no-no, but brazing is possible when done quickly. Lead may segregate into the brazing alloy with prolonged heating.
"In good quality leaded steel, the lead is very finely dispersed and not prone to "sweating out". All known cases of "lead sweat" have been associated with steel rejectable on the basis of lead segregation ie. lead colonies of excessive size."
-- Paragraph 8.8 (on 50th pdf page)
Due to high sulfur & phosphorus as well as lead, long-term high temperatures probably result in segregation & weakened grain boundaries. I don't know of leaded steels being used at elevated temperatures, though. Vaguely recall 500 oF given as a limit.
Thanks for the help, fortunately the high temperature exposure is under a minute when under load so it seems for such use I can use comparable steel data.
