WCO Explanatory Notes reproduced for reference. © World Customs Organization. Verify against official WCO publication.
74.05 - Master alloys of copper. Master alloys are defined in Chapter Note 1 (c). The master a110 s of this heading are alloys containing more t h e 10 % by weight of copper together with ot ier elements, and which, because of thelr composition, are too brittle for normal metal working. They are therefore used either to introduce into brass, bronze or aluminium bronze, other elements with a higher melting point than those alloys, or highly oxidisable elements (e.g., aluminium, cadmium, arsenic, magnesium) or elements sublimable at the fusion temperature, or else to facilitate the preparation of certain alloys by adding de-oxidising, de-sulphurising or similar elements (e.g., calcium). The copper acts as a solvent or diluent of the other elements and must be present in amounts sufficient to reduce the melting point or the oxidising or sublimating action of the master alloy. If the pro ortion of copper is too high, however, that metal unduly dilutes the other elements introduce into the alloys. The copper content generally ranges between 30 and 90 % in these products but may, in special cases, be above or below these limits. X The heading therefore excludes, for exam le, any COP er-nickel alloy, even if intended for use as a master alloy since copper-nickel a1 oys are use lly malleable in all proportions. Other alloys, for exampie copper man anese and copper-silicon alloys, ma or may not be malleable according to the proportions of e constituent metals present; in suc cases the heading covers only those alloys which are not usefully malleable. f % h K Master alloys of this heading include copper aluminium, copper beryllium, copper boron, co er cadmium, copper chromium,copper iron, copper magnesium, copper manganese, copper mo ybdenum, copper silicon, copper titanium or copper vanadium. PP Master alloys are generally in the form of small blocks or cakes divided for easy breaking, brittle sticks or pellets, and have the appearance of crude foundry products. Copper phosphide (phosphor copper) containing more than 15 % by weight of phosphorus falls in heading 28.48.
1.- In this Chapter the following expressions have the meanings hereby assigned to them : (a) Refined copper Metal containing at least 99.85 % by weight of copper; or Metal containing at least 97.5 % by weight of copper, provided that the content by weight of any other element does not exceed the limit specified in the following table : TABLE - Other elements Element Limiting content % by weight Ag Silver 0.25 As Arsenic 0.5 Cd Cadmium 1.3 Cr Chromium 1.4 Mg Magnesium 0.8 Pb Lead 1.5 S Sulphur 0.7 Sn Tin 0.8 Te Tellurium 0.8 Zn Zinc 1 Zr Zirconium 0.3 Other elements*, each 0.3 * Other elements are, for example, Al, Be, Co, Fe, Mn, Ni, Si. (b) Copper alloys Metallic substances other than unrefined copper in which copper predominates by weight over each of the other elements, provided that : (i) the content by weight of at least one of the other elements is greater than the limit specified in the foregoing table; or (ii) the total content by weight of such other elements exceeds 2.5 %. (c) Master alloys Alloys containing with other elements more than 10 % by weight of copper, not usefully malleable and commonly used as an additive in the manufacture of other alloys or as de-oxidants, de- sulphurising agents or for similar uses in the metallurgy of non-ferrous metals. However, copper phosphide (phosphor copper) containing more than 15 % by weight of phosphorus falls in heading