Visualization of models saved in STEP product data files (.stp, step), can be probably exported and saved as PNG images for previewing purposes. But no actual conversion is likely because there are no raster data to conversion anyway, a .step file contains just mesh and no texture.
Convert ISO-10303 STEP product data to Portable Network Graphic.
We have found 3 software records in our database eligible for .step to .png file format conversion.
Microsoft Windows software - convert step to png on Windows
A widely-used 3D animation application from Autodesk
Convert from step file format
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned step to png. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
A 3D CAD translation softwate
A 3D product data optimalization software