SECTION XV Note 5. Classification of alloys (other than ferroalloys and master alloys as defined in chapters 72 and 74):
(a) An alloy of base metals is to be classified as an alloy of the metal which predominates by weight over each of the other metals.
(b) An alloy composed of base metals of this section and of elements not falling within this section is to be treated as an alloy of base metals of this section if the total weight of such metals equals or exceeds the total weight of the other elements present.
(c) In this section the term “alloys” includes sintered mixtures of metal powders, heterogeneous intimate mixtures obtained by melting (other than cermets) and intermetallic compounds.
Here, the wood screw is composed of 50% iron, 25% copper and 25% aluminum base metals and as per Section Note 5(a) it has to be considered as if it is an alloy of iron and iron screws are classified under heading 7318.
7318.12.00 00 classifies threaded wood screws of iron which is the most specific description.