Effect of temperature on Manganese bronze screws?

[consano]

I wanted to know if anyone out there knew of any research on the effects of temperature on Manganese Bronze C67500. I need to know what the effects on the tensile and yield strengths would be versus temperature increase.

I have screws that need to be used in a 500F environment.

Thanks

 

[btrueblood]

I believe 500F is the stress-relief temperature for Manganese Bronze (see data for the cast version of the alloy). Thus, any cold-work done on the bar that contributes to its tensile strength may go away over time at 500F.

 

[kenvlach]

I will go even further than btrueblood: Except for short times and low loads, this alloy shouldn't be used at 500 °F.

For two alloys of similar composition to C67500, the annealing temperature is 260 °C (500 °F). Lots of creep-rupture data, etc. for C86500. Curves are shown in ASM Handbook vol. 2, some of the data is available at the MatWeb link below. Looking at the 250, 350 & 450 °F curves, the rupture stress for 100 hours at 500 °F is <100 MPa (~10 ksi). From the isochronous stress-strain curves at 450 °F, for a given strain (~0.15%), an initial stress of 90 MPa will decay to ~33 MPa after 100 hours, and to 20 MPa after 2000 hours. From MatWeb, the Creep Strength is 12 MPa (1740 psi) for 0.1% creep in 10,000 hours at 230°C (450 °F). And, the comparison alloy C86500 has more Mn, Al & Ni which likely improve creep resistance over that of C67500.

Manganese Bronze A,
C67500: Cu 58.5, Fe 1.4, Mn 0.1, Sn 1, Zn 39

http://www.matweb.com/search/SpecificMaterial.asp?bassnum=MCUADV

C86400: Cu 56–62, Fe max 2, Mn max 1.5, Sn max 1.5, Zn 37, Al max 1.5, Ni max 1, Pb 0.5–1.5.

C86500: Cu 55–60, Fe 0.4–2, Mn max 1.5, Sn max 1, Zn 39, Al 0.5–1.5, Ni max 1, Pb max 0.4.

http://www.matweb.com/search/SpecificMaterial.asp?bassnum=MCUDBK