Yield Point and Temparature relationship of High Tensile Steel

[Vashi]

I have a steel material that has a yield strength of 515 mpa and a tensile strength of 615 mpa at zero degrees. What i need to know is will the tensile strength and yield strength be higher than 293 mpa at 80 degrees. The steel is ahigh tensile grade steel from china (Q390C).

[FredGarvin]

If it's Chinese, then I wouldn't count on any of those numbers.

Most common forms of steel are going to exhibit a general trend of decrease in yield strength and ultimate strength with increasing temperature. Since Q390C is not in any of my handy references, I can't comment exactly. However, if that alloy follows the same characteristics of regular alloy steels like a 4140, the yield point should be around 92-95% of the room temperature value according to MIL Handbook 5 (assuming your temperatures were in deg C).

[Vashi]

Thanks for your response. Yes I agree, it is difficult to count on these numbers. According to chinese standards. The Chemical Composition of these materials should be as follows. C-0.2,Si-0.55,Mn-1.00-1.6,P<0.045,S<0.035,V-0.02-0.2,NB-0.015-0.060,Ti-0.02-0.20,AL>0.015,CR<0.030,NI<0.7.

The yield Strength varies from 330 mpa to 390 mpa min allowed, with >50mm thick plates having the lowest min yield allowed at zero degrees.

Would this information help to determine if the mpa would be higher at 80 degrees c. And yes i was refering to the temprerature in C.

[nucleus]

The following is from Machinery’s Handbook for structural steel

Degrees Fahrenheit 210 400 570 750 930 1100 1300 1475
Strength % of 70 Deg F 103 132 122 86 49 28 ….. ……..