Hello,

Maximum solubility is can be understood by different phases of iron with temperature and corresponding maximum carbon content at that temperature.

Like for alpha iron, at room temperature the max solubility of carbon is 0.002 wt%

for alpha iron maximum is at 723 C and it is 0.02 wt%

for gamma iron it is 2.1 wt% at 1147 C

for delta iron it is 0.09 wt% at 1496 C

Solubility varies as the temperature varies.

Hope this helps.