What type of chemical bond makes the alloy steel?

The general properties of a metal, such as malleability, ductility, conductivity to heat and electricity, are thought to result from non-localized metallic bonding, in which each metal atom donates a portion of its valence electrons to the lattice, giving metal nuclei a positive charge. Alkali metals, such as lithium, sodium, potassium, and rubidium, only have one electron to contribute to the metallic lattice, making them generally soft and low melting. Many electron metals, like iron, have higher melting points, but still exhibit malleability and ductility at elevated temperatures.

Thus, steel is an alloy of iron and carbon and is the best material for tools. Steel is a metal and exhibits metallic bonding as a result. During the manufacturing process, a small amount of carbon is added to make steel steel, up to 1-2% w/w.

I have no idea how the carbon is attached to the iron atoms; it's one of those areas where chemistry becomes metallurgy and function supersedes chemistry. Steel contains a lot of different metals, and different alloys can be specially made for different uses.

The type of chemical bond that makes alloy steel is metallic bonding.