A few questions first.
[ul]
[li]There appear to be various standards that use ST 52 as a designation, such as DIN 17100, DIN 2391, DIN 2448, etc. etc. etc. Which are you asking about?[/li]
[li]For some specs there seem to be various grades within ST52. If your DIN has grades, which grade do you mean?[/li]
[li]What product form are you using? Plate, bar, etc. This may be answered when you specify your DIN.[/li]
[li]What Code are you trying to meet?[/li]
[/ul]
As an example of one possible answer, a number of sites suggest DIN 17100 ST52-3 plate is similar to A572-50 plate, which tells me that A36 plate would be too weak to replace this ST52.
If you mean "Can I substitute A36 where ST52 was used in the design?", the answer is "generally, no".
If you want to revise a design to use one material instead of the other, you can go through the design and see how it works. Maybe be minimal difference. Or thickness, lowest design temp, etc, may come up different.
