I'm not sure of the differences between iron and steel either as far as magical properties.  Both have been known to repel certain entities such as the fey.

As for your spirit problem I'd try afew things:

1) Speaking to it and find out what it wants.  If you're not able to communicate with it then invite a psychic over who can.    Make an offering to the being and ask it nicely to leave or to not cause mischief.  If that doesn't work blast it with light    rays (I like to use the silver and violet rays) or use spirit traps to capture it. Check out Inominandum's book on    Protection and Reversal magic for ideas.2) Research the history of the house/land.  See if there have been any reported incidents in the past or if the land was sacred    to any native groups.3) Look for any portals/spirit doorways which allow this being entrance and seal those. Somehow I feel the graveyard may have some     connection with the entity, but look for other portals/doorways around the house. Make a stronger ward in the area facing    the graveyard.4) Do a complete house cleansing.  Wash the floors/walls with Exorcism wash, fumigate the house with Exorcism Incense,    sprinkle Holy Water, annoint the walls, windows and doors with Holy Oil and with warding symbols.  Do this with prayer,    using psalms that are commonly used for exorcism and protection.5)  Raise the energy frequency/vibrations of the house to a very high level where it would make the entity uncomfortable      and want to leave.6)  Invoke angels like Michael to assist in escorting the spirit out.7)  When you sense the entity has left, and you have sealed all portals, place wards so the being can't come back.

Adesh!-Aghor Pir