Generally steel can be used up to about 400 C when above this the effects of creep and stress or strain accumulation will occur. Otherwise the only consideration of steel at temperature is it's strength, ie. yield value, which will reduce with temperature.
It depends on what heat treatments have been performed on this steel. This grade is an unalloyed, mild steel, meaning that only Mn and Si are present in appreciable amounts. Since the carbon content is specified to the range of 0.12-0.18, the ductile-to-brittle transition temperature will be near -40 C. This means that brittle fracture becomes a concern, so fatigue and impact conditions could lead to premature failure.
If the steel has been subsequently case-hardened, which is typical for this alloy when used for gears, cams, rollers, etc., then the case-hardened zone will be extremely brittle, and will be quite susceptible to brittle fracture under high loads.
