Hello Author,
Open CASCADE Technology (OCCT) provides a ready-to-use STEP reading / writing interface, as well as a wide variety of modeling algorithms, that together can let your create your models and store them in STEP files.
As for using OCCT C++ API from Delphi, it should be possible with help of our advanced component "C# .NET wrapper".
Please, do not hesitate to contact us at http://www.opencascade.com/contact for more information and assistance.
Best regards,
Commenter-1