what is steel a mixture or a compound
Steel is an alloy, therefore it is a mixture. It is not an element because it is not on the periodic table. It is not a compound because the iron and carbon are not chemically bonded together.
Steel is considered a mixture rather than a compound because the iron does not chemically bond with the carbon and other components. Instead, in simple iron-carbon alloys, the carbon atoms are small enough to intersperse themselves within the open spaces of the iron crystal.