This situation is similar to the transwarp beaming equation, where Scotty adjusts to have space be the thing that's moving. The portal and the titanium rod are moving relative to each other, so the titanium rod has momentum relative to the moving portal. This means that the titanium rod should pass through the metal block without any issues.
if you push a portal into a titanium rod with a metal block below and not against the second portal, the titanium rod should go through the metal block. This is because the portal is moving towards the titanium rod, and with respect to the portal,
electrons push other electrons away so this would probably make it explode
...so yeah...uh...
electrons push other electrons away so this would probably make it explode