You can open a STEP or IGES file in Autodesk Inventor (create a file). You can also place a STEP file in an assembly, import an IGES file into an existing Inventor part file, or place an IGES solid body as a component in an assembly. (Assemblies require Inventor.)
You can place imported data in a Construction folder that contains individual group, solid, surface, and wireframe nodes. A single node contains surfaces, so you can promote multiple surfaces as a single feature to the part environment.
In many cases, composite features possess the same behavior as Base Surface features. However, they can also have multiple individual bodies within them, such as solid and surface bodies that are not stitched as one. You cannot interact with the individual bodies.
Surfaces that cannot be stitched together remain in the Construction folder in the browser. Quilts are promoted to the part environment and are shown as surfaces in the browser. You can analyze and repair surfaces that did not automatically stitch when they were imported.
By default, Inventor applies the part name (file name of the inserted part) to browser file nodes. Other CAD systems may apply the part number property. When a STEP file is imported into Inventor, its name may differ from the name of the CAD system that generated the STEP file. To avoid confusion, use the Rename Browser Nodes command to specify the browser node naming scheme.
When you open a STEP file, if you select Save Parts During Load, the imported files are saved in Inventor format to locations specified by the Destination Directory settings. If files with the same name exist, the existing files are moved to the Old Versions folder.
When you open an IGES file, 308 and 408 structures are used. The block structures in the file are translated into multiple parts referenced by an assembly. Each part file contains the data for a single structure instance. If the Auto Stitch and Promote option fails or is turned off, the data is placed in construction groups in the defined part. Optionally, you can ignore the 308/408 block definitions and open all the data into a single part file.