AIuminium and articles thereof Note. 1.- In this Chapter the following expressions have the meanings hereby assigned to them : (a) Bars and rods Rolled, extruded, drawn or forged products, not in coils, which have a uniform solid cross-section along their whole length in the shape of circles, ovals, rectangles (including s uares), equi1ater:l trim les or regular convex polygons (includh " flattened c~rcles" and " mofified rectan les of wkch two opposite sides are convex arcs, 8 e other two sides being straight, of equal en& and parallel). Products with a rectangular (including s uare), triangular or poly onal cross-sect~on may have corners rounded along the~rwhole length. ~ % thxkness e of such pro ucts which have a rectangular (including " modified rectangular ") cross-section exceeds one-tenth of the width. The expression also covers cast or sintered products, of the same forms and dimensions, which have been subsequently worked after production (otherwise than by simple trimming or de-scaling), rovided that they have not thereby assumed the character of articles or products of other Eeadings. (b) Profiles Rolled, extruded, drawn, forged or formed products, coiled or not, of a uniform cross-section along their whole length, which do not conform to any of the definitions of bars, rods, wire, plates, sheets, strip, foil, tubes or ipes. The expression aIso covers cast or sintered products, of the same forms, which have been su sequently worked after production (otherwise than by simple trimming or de-scaling), provided that they have not thereby assumed the character of articles or products of other headings. E (c) Wire Rolled, extruded or drawn products, in coils, which have a uniform solid cross-section along their whole length in the shape of circles, ovals, rectangles (including s uares), equilateral triangles or regular convex polygons (including " flattened circles " and " mod%ed rectan les ", of which two opposite sides are convex arcs, the other two sides being straight, of equal ength and parallel). Products with a rectangular.(includmng square), triangular or polygonal cross-section may have comers rounded along theu whole len h. The hckness of such products whch have a rectangular (including modified rectan& ") cross-section exceeds one-tenth of the width. P (d) Plates, sheets, strip and foil Flat-surfaced roducts (other than the unwrought products of heading 76-01), coiled or not, of solid rectan@Yar (other than s uare) cross-section with or without rounded comers (including "modified rectan les " of whic two opposite sides are convex arcs, the other two sides being straight, of equal !ngth and parallel) of a uniform thickness, which are : - of rectangular (including square) shape with a thickness not exceeding one-tenth of the width, - of a shape other than rectangular or square, of any size, provided that they do not assume the character of articles or products of other headings. Headings 76.06 and 76.07 apply, inter alia, to plates, sheets, strip and foil with patterns (for example, grooves, ribs, che uers, tears, buttons, lozenges and to such products which have been perforated, corn ated, polis ed or coated, provided that ey do not thereby assume the character of articles or profucts of other headings. h (e) Tubes and pipes Hollow products, coiled or not, which have a uniform cross-section with only one enclosed void along their whole length in the shape of circles, ovals, rectangles (including squares), equilateral triangles or regular convex polygons, and which have a uniform wall thickness. Products with a rectangular (including square), equilateral piangular or regular convex polygonal cross-section, which may have corners rounded along their whole length, are also to be considered as tubes and pipes provided the inner and outer cross-sections are concentric and have the same form and onentation. Tubes and ipes of the fore oing cross-sections may be olished, coated, bent, threaded, drilled, waiste$expanded, cone-staped or fitted wlth flanges, eo lars or rings. P Subheading Notes. 1.- In this Chapter the following expressions have the meanings hereby assigned to them : (a) Aluminium, not alloyed Metal containing b weight at least 99 % of aluminium, provided that the content by weight of any other element oes not exceed the limit specified in the following table : d' TABLE - Other elements Element Limiting content % by weight Fe + Si (iron plus silicon) I Other elements('), each 0. "' Other elements are, for example Cr, Cu, Mg, Mn, Ni, Zn. (2) Copper is permitted in a proportion greater than 0.1 % but not more than 0.2 %, provlded that neither the chromlurn nor manganese content exceeds 0.05 %. (b) Aluminium alloys Metallic substances in which aluminium predominates by weight over each of the other elements, provided that : (i) the content by wei ht of at least one of the other elements or of iron plus silicon taken together is greater than the Ernit specified in the foregoing table; or (ii) the total content by weight of such other elements exceeds I %. Notwithstanding the provisions of Chapter Note 1 (c), for the urposes of subheading 7616.91 the term " wire " applies only to products, whether or not in coils, o any cross-sectional shape, of which no cross-sectional dimension exceeds 6 mm. F GENERAL This Chapter covers aluminium and its alloys, and certain articles thereof. Aluminium is obtained princi ally from bauxite, a crude hydrated alumina (see the Explanatory Note to heading 26.06). The irst stage of the extraction is designed to convert the bauxite into pure aluminium oxide (alumina). For this purpose the ground ore is calcined and then treated with sodium hydroxide to produce a solution of sod~umaluminate; this is then filtered to eliminate insoluble impurities (iron oxide, silica, etc.). The aluminium is then precipitated as aluminium hydroxide, which is calcined to give pure aluminium oxide in the form of a white powder. However, aluminium hydroxide and aluminium oxide are classified in Chapter 28. F. In the second stage, the metal is extracted by electrolytic reduction of the alumina dissolved in fused cryolite (the latter is sodium aluminium fluonde, but it acts solely as a solvent). This electrolysis is carried out in carbon lined baths which act as the cathode; carbon bars are used as anodes. The aluminium is de osited in the bottom of the baths fiom where it is syphoned. It is then cast in the form of bloc s, ingots, billets, slabs, wire bars, etc., usually after refining. By repeated electrolysis, aluminium can be obtained almost completely pure. Aluminium may also be obtained by the treatment of certain other ores such as leucite (double silicate of aluminium and potassium), by re-melting aluminium waste and scrap or by processing residues (slag, dross, etc.). Aluminium is a bluish-white metd characterised by its lightness. It is very ductile and easily rolled, drawn, forged, stamped, and may be cast, etc. Like other soft metals, aluminium is also very suitable for extrusion and die-casting. In modern practice it can be soldered. Aluminium is an excellent conductor of heat and electricity and is a very good reflector. Since the oxide film which forms naturally on its surface protects the metal, it IS often produced artificial1 in greater depth by anodising or chemical treatment; the surface is also sometimes coloured wing these processes. d The hardness, toughness, etc., of aluminium can be very substantially increased by a110 'ng with other elements such as copper, magnesium, silicon, zinc or manganese. Certain of $e alloys may be improved by age-hardening treatments. These processes may be followed by tempering. The principal aluminium alloys which may be classified in this Chapter under the provisions of Note 5 to Section XV (see the General Explanatory Note to that Section) are : (1) Aluminium-copper alloys. These are aluminium based alloys with a low copper content. (2) Aluminium-zinc-copper alloys. (3) Aluminium-silicon alloys (e-g., " alpax ", silumin "). " (4) Aluminium-manganese-magnesium alloys. (5) Aluminium-magnesium-siliconalloys (e.g., " almelec "," aldrey '3. (6) Aluminium-copper-magnesium-manganese alloys (e.g., " duralumin '3. (7) Aluminium-magnesium alloys (e.g., " magnalium "). (8) Aluminium-manganese alloys. (9) Aluminium-zinc-magnesium alloys. Most of these alloys may also contain small quantities of iron, nickel, chromium, etc.; they are often marketed under trade names which vary according to the country of origin. The special properties of aluminium and its alloys favour their wide use : in the aircraft, automobile or shpbuilding industries; in the building industry; in the construction of railway or tramway rolling-stock- in the electrical industry (e.g., as cables ; for all types of containers $reservoirs and vats of all sizes, transport casks, drums, etc.); for ousehold or kitchen utensils; or the manufacture of foil; etc. h The Chapter covers : (A) Unwrought aluminium, and waste and scrap (headings 76.01 and 76.02). (B) Aluminium powders and flakes (heading 76.03). (C) Products general1 obtained by rolling, extruding, drawing or forging the unwrought aluminium of heac ring 76.01 (headings 76.04 to 76.07). (D) Various articles specified in headings 76.08 to 76.15, and other articles of the residual heading 76.16 which covers all other aluminium articles other than those included in Chapter 82 or 83, or more specifically covered elsewhere in the Nomenclature. Products obtained by sintering aluminium and alumina are considered as cermets and are excluded from this Chapter (heading 81.13). Products and articles of aluminium are frequently subjected to various treatments to improve the properties or appearance of the metal, to protect it from corrosion, etc. These treatments are generally those referred to at the end of the General Explanatory Note to Chapter 72, and do not affect the classification of the goods. The classification of composite goods, particularly made up articles, is explained in the General Explanatory Note to Sectton XV. -