I have an idea about this.  You can get closeup views of the steel without the damaging heat radiation if you use fiber optics.  Put a good quality fiber optic bundle on the lens of the camera and run the other end up to the steel surface.  The IR can be filtered out by the fiber optics.  If this is no good, It might be possible to buy lenses or lens covers which can filter the IR.  This reminds me of work I've done using high intensity high pressure mercury/xenon arc lamps to illuminate heat sensitive materials.  The IR filter was simply a "glass" plate in the optical beam.  I don't know the composition of this plate.

Many types of filters are made for optical use, it should be possible to find something which transmits optical (or near 700nm light) and not IR light.