how is steel affected at 0°C, 30°C and 315.556°C? please help and explain.?

315.566 °C ? Temperature to three decimal places? You got to be kidding. Steel at 315.566 is affected the same as steel at 315 °C, or 316 °C. If you can tell the difference in the effects from just a tiny fraction of a degree, you're better than 99.9% of the science labs in the world. There's more effect from what you had for breakfast the morning of any measurement of effects.

There are no melting or crystallization effects below 738 °C. Steel expands about 1.44% per 1 °C, but it could easily be 14.3% or 14.5%.