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.