Aluminum Alloys – Effects of Alloying Elements

The important alloying elements and impurities are listed here alphabetically as a concise review of major effects. Some of the effects, particularly with respect to impurities, are not well documented and are specific to particular alloys or conditions.

Antimony is present in trace amounts (0.01 to 0.1 ppm) primary in commercial-grade aluminum. Antimony has a very small solid solubility in aluminum (<0.01%). Some bearing alloys contain up to 4 to 6% Sb. Antimony can be used instead of bismuth to counteract hot cracking in aluminum-magnesium alloys.

Arsenic. The compound AsAl is a semiconductor. Arsenic is very toxic (as AsO3) and must be controlled to very low limits where aluminum is used as foil for food packaging.

Beryllium is used in aluminum alloys containing magnesium to reduce oxidation at elevated temperatures. Up to 0.1% Be is used in aluminizing baths for steel to improve adhesion of the aluminum film and restrict the formation of the deleterious iron-aluminum complex.

Bismuth. The low-melting-point metals such as bismuth, lead, tin, and cadmium are added to aluminum to make free-machining alloys. These elements have a restricted solubility in solid aluminum and form a soft, low-melting phase that promotes chip breaking and helps to lubricate the cutting tool. An advantage of bismuth is that its expansion on solidification compensates for the shrinkage of lead. A 1-to-1 lead-bismuth ratio is used in the aluminum-copper alloy, 2011, and in the aluminum-Mg-Si alloy, 6262. Small additions of bismuth (20 to 200 ppm) can be added to aluminum-magnesium alloys to counteract the detrimental effect of sodium on hot cracking.

Boron is used in aluminum and its alloys as a grain refiner and to improve conductivity by precipitating vanadium, titanium, chromium, and molybdenum. Boron can be used alone (at levels of 0.005 to 0.1%) as a grain refiner during solidification, but becomes more effective when used with an excess of titanium. Commercial grain refiners commonly contain titanium and boron in a 5-to-l ratio.

Cadmium is a relatively low-melting element that finds limited use in aluminum. Up to 0.3% Cd may be added to aluminum-copper alloys to accelerate the rate of age hardening, increase strength, and increase corrosion resistance. At levels of 0.005 to 0.5%, it has been used to reduce the time of aging of aluminum-zinc-magnesium alloys.

Calcium has very low solubility in aluminum and forms the intermetallic CaAl4. An interesting group of alloys containing about 5% Ca and 5% Zn have superplastic properties. Calcium combines with silicon to form CaSi2, which is almost insoluble in aluminum and therefore will increase the conductivity of commercial-grade metal slightly. In aluminum-magnesium-silicon alloys, calcium will decrease age hardening. Its effect on aluminum-silicon alloys is to increase strength and decrease elongation, but it does not make these alloys heat treatable.

Carbon may occur infrequently as an impurity in aluminum in the form of oxycarbides and carbides, of which the most common is A14C3, but carbide formation with other impurities such as titanium is possible. A14C3 decomposes in the presence of water and water vapor, and this may lead to surface pitting.

Cerium, mostly in the form of mischmetal (rare earths with 50 to 60% Ce), has been added experimentally to casting alloys to increase fluidity and reduce die sticking.

Chromium occurs as a minor impurity in commercial-purity aluminum (5 to 50 ppm). It has a large effect on electrical resistivity. Chromium is a common addition to many alloys of the aluminum-magnesium, aluminum-magnesium-silicon, and aluminum-magnesium-zinc groups, in which it is added in amounts generally not exceeding 0.35%. In excess of these limits, it tends to form very coarse constituents with other impurities or additions such as manganese, iron, and titanium. Chromium has a slow diffusion rate and forms fine dispersed phases in wrought products. These dispersed phases inhibit nucleation and grain growth. Chromium is used to control grain structure, to prevent grain growth in aluminum-magnesium alloys, and to prevent recrystallization in aluminum-magnesium-silicon or aluminum-magnesium-zinc alloys during hot working or heat treatment.

Cobalt is not a common addition to aluminum alloys. It has been added to some aluminum-silicon alloys containing iron, where it transforms the acicular ß (aluminum-iron-silicon) into a more rounded aluminum-cobalt-iron phase, thus improving strength and elongation. Aluminum-zinc-magnesium-copper alloys containing 0.2 to 1.9% Co are produced by powder metallurgy.

Copper. Aluminum-copper alloys containing 2 to 10% Cu, generally with other additions, form important families of alloys. Both cast and wrought aluminum-copper alloys respond to solution heat treatment and subsequent aging with an increase in strength and hardness and a decrease in elongation. The strengthening is maximum between 4 and 6% Cu, depending upon the influence of other constituents present.

Copper-magnesium. The main benefit of adding magnesium to aluminum-copper alloys is the increased strength possible following solution heat treatment and quenching. In wrought material of certain alloys of this type, an increase in strength accompanied by high ductility occurs on aging at room temperature. On artificial aging, a further increase in strength, especially in yield strength can be obtained, but at a substantial sacrifice in tensile elongation.

Copper-magnesium plus other elements. The cast aluminum-copper-magnesium alloys containing iron are characterized by dimensional stability and improved bearing characteristics, as well as by high strength and hardness at elevated temperatures. However, in a wrought Al-4%Cu-0.5%Mg alloy, iron in concentrations as low as 0.5% lowers the tensile properties in the heat-treated condition, if the silicon content is less than that required to tie up the iron as the aFeSi constituent.

Gallium is an impurity in aluminum and is usually present at levels of 0.001 to 0.02%. At these levels its effect on mechanical properties is quite small. At the 0.2% level, gallium has been found to affect the corrosion characteristics and the response to etching and brightening of some alloys.

Hydrogen has a higher solubility in the liquid state at the melting point than in the solid at the same temperature. Because of this, gas porosity can form during solidification. Hydrogen is produced by the reduction of water vapor in the atmosphere by aluminum and by the decomposition of hydrocarbons. In addition to causing primary porosity in casting, hydrogen causes secondary porosity, blistering, and high-temperature deterioration (advanced internal gas precipitation) during heat treating. It probably plays a role in grain-boundary decohesion during stress-corrosion cracking. Its level in melts is controlled by fluxing with hydrogen-free gases or by vacuum degassing.

Indium. Small amounts (0.05 to 0.2%) of indium have a marked influence on the age hardening of aluminum-copper alloys, particularly at low copper contents (2 to 3% Cu).

Iron is the most common impurity found in aluminum. It has a high solubility in molten aluminum and is therefore easily dissolved at all molten stages of production. The solubility of iron in the solid state is very low (~0.04%) and therefore, most of the iron present in aluminum over this amount appears as an intermetallic second phase in combination with aluminum and often other elements.

Lead. Normally present only as a trace element in commercial-purity aluminum, lead is added at about the 0.5% level with the same amount as bismuth in some alloys (2011 and 6262) to improve machinability.

Lithium. The impurity level of lithium is of the order of a few ppm, but at a level of less than 5 ppm it can promote the discoloration (blue corrosion) of aluminum foil under humid conditions. Traces of lithium greatly increase the oxidation rate of molten aluminum and alter the surface characteristics of wrought products.

Magnesium is the major alloying element in the 5xxx series of alloys. Its maximum solid solubility in aluminum is 17.4%, but the magnesium content in current wrought alloys does not exceed 5.5%. The addition of magnesium markedly increases the strength of aluminum without unduly decreasing the ductility. Corrosion resistance and weldability are good.

Magnesium-Manganese. In wrought alloys, this system has high strength in the work-hardened condition, high resistance to corrosion, and good welding characteristics. Increasing amounts of either magnesium or manganese intensify the difficulty of fabrication and increase the tendency toward cracking during hot rolling, particularly if traces of sodium are present.

Magnesium-Silicon. Wrought alloys of the 6xxx group contain up to 1.5% each of magnesium and silicon in the approximate ratio to form Mg2Si, that is, 1.73:1. The maximum solubility of Mg2Si is 1.85%, and this decreases with temperature.
Precipitation upon age hardening occurs by formation of Guinier-Preston zones and a very fine precipitate. Both confer an increase in strength to these alloys, though not as great as in the case of the 2xxx or the 7xxx alloys.

Manganese is a common impurity in primary aluminum, in which its concentration normally ranges from 5 to 50 ppm. It decreases resistivity. Manganese increases strength either in solid solution or as a finely precipitated intermetallic phase. It has no adverse effect on corrosion resistance. Manganese has a very limited solid solubility in aluminum in the presence of normal impurities but remains in solution when chill cast so that most of the manganese added is substantially retained in solution, even in large ingots.

Mercury has been used at the level of 0.05% in sacrificial anodes used to protect steel structures. Other than for this use, mercury in aluminum or in contact with it as a metal or a salt will cause rapid corrosion of most aluminum alloys.

Molybdenum is a very low level (0.1 to 1.0 ppm) impurity in aluminum. It has been used at a concentration of 0.3% as a grain refiner, because the aluminum end of the equilibrium diagram is peritectic, and also as a modifier for the iron constituents, but it is not in current use for these purposes.

Nickel. The solid solubility of nickel in aluminum does not exceed 0.04%. Over this amount, it is present as an insoluble intermetallic, usually in combination with iron. Nickel (up to 2%) increases the strength of high-purity aluminum but reduces ductility. Binary aluminum-nickel alloys are no longer in use but nickel is added to aluminum-copper and to aluminum-silicon alloys to improve hardness and strength at elevated temperatures and to reduce the coefficient of expansion.

Niobium. As with other elements forming a peritectic reaction, niobium would be expected to have a grain refining effect on casting. It has been used for this purpose, but the effect is not marked.

Phosphorus is a minor impurity (1 to 10 ppm) in commercial-grade aluminum. Its solubility in molten aluminum is very low (~0.01% at 660oC) and considerably smaller in the solid.

Silicon, after iron, is the highest impurity level in electrolytic commercial aluminum (0.01 to 0.15%). In wrought alloys, silicon is used with magnesium at levels up to 1.5% to produce Mg2Si in the 6xxx series of heat-treatable alloys.

Vanadium. There is usually 10 to 200 ppm V in commercial-grade aluminum, and because it lowers conductivity, it generally is precipitated from electrical conductor alloys with boron.

Zinc. The aluminum-zinc alloys have been known for many years, but hot cracking of the casting alloys and the susceptibility to stress-corrosion cracking of the wrought alloys curtailed their use. Aluminum-zinc alloys containing other elements offer the highest combination of tensile properties in wrought aluminum alloys.

Zinc-Magnesium. The addition of magnesium to the aluminum-zinc alloys develops the strength potential of this alloy system, especially in the range of 3 to 7,5% Zn. Magnesium and zinc form MgZn2, which produces a far greater response to heat treatment than occurs in the binary aluminum-zinc system. The strength of the wrought aluminum-zinc alloys also is substantially improved by the addition of magnesium. Increasing the MgZn2, concentration from 0.5 to 12% in cold-water quenched 1.6 mm sheet continuously increases the tensile and yield strengths. The addition of magnesium in excess (100 and 200%) of that required to form MgZn2 further increases tensile strength.

Zinc-Magnesium-Copper. The addition of copper to the aluminum-zinc-magnesium system, together with small but important amounts of chromium and manganese, results in the highest-strength aluminum-base alloys commercially available. In this alloy system, zinc and magnesium control the aging process. The effect of copper is to increase the aging rate by increasing the degree of supersaturation and perhaps through nucleation of the CuMgAl2 phase. Copper also increases quench sensitivity upon heat treatment. In general, copper reduces the resistance to general corrosion of aluminum-zinc-magnesium alloys, but increases the resistance to stress corrosion. The minor alloy additions, such as chromium and zirconium, have a marked effect on mechanical properties and corrosion resistance.

Zirconium additions in the range 0.1 to 0.3% are used to form a fine intermetallic precipitate that inhibits recovery and recrystallization. An increasing number of alloys, particularly in the aluminum-zinc-magnesium family, use zirconium additions to increase the recrystallization temperature and to control the grain structure in wrought products.

Aluminum and Aluminum Alloys Casting Problems

Aluminum castings have played an integral role in the growth of the aluminum industry since its inception in the late 19th century. The first commercial aluminum products were castings, such as cooking utensils and decorative parts, which exploited the novelty and utility of the new metal. Those early applications rapidly expanded to address the requirements of a wide range of engineering specifications.

Alloy development and characterization of physical and mechanical characteristics provided the basis for new product development through the decades that followed. Casting processes were developed to extend the capabilities of foundries in new commercial and technical applications. The technology of molten metal processing, solidification, and property development has been advanced to assist the foundry man with the means of economical and reliable production of parts that consistently meet specified requirements.

Today, aluminum alloy castings are produced in hundreds of compositions by all commercial casting processes, including green sand, dry sand, composite mold, plaster mold, investment casting, permanent mold, counter-gravity tow-pressure casting, and pressure die casting.

Alloys can also be divided into two groups: those most suitable for gravity casting by any process and those used in pressure die casting. A finer distinction is made between alloys suitable for permanent mold application and those for other gravity processes.

Material constraints that formerly limited the design engineer’s alloy choice once a casting process had been selected are increasingly being blurred by advances in foundry technique. In the same way, process selection is also less restricted today. For example, many alloys thought to be unusable in permanent molds because of casting characteristics are in production by that process.

Melting and Metal Treatment

Aluminum and aluminum alloys can be melted in a variety of ways. Coreless and channel induction furnaces, crucible and open-hearth reverberatory furnaces fired by natural gas or fuel oil, and electric resistance and electric radiation furnaces are all in routine use. The nature of the furnace charge is as varied and important as the choice of furnace type for metal casting operations. The furnace charge may range from prealloyed ingot of high quality to charges made up exclusively from low-grade scrap.

Even under optimum melting and melt-holding conditions, molten aluminum is susceptible to three types of degradation:

  • With time at temperature, adsorption of hydrogen results in increased dissolved hydrogen content up to an equilibrium value for the specific composition and temperature
  • With time at temperature, oxidation of the melt occurs; in alloys containing magnesium, oxidation losses and the formation of complex oxides may not be self-limiting
  • Transient elements characterized by low vapor pressure and high reactivity are reduced as a function of time at temperature; magnesium, sodium, calcium, and strontium, upon which mechanical properties directly or indirectly rely, are examples of elements that display transient characteristics.

Turbulence or agitation of the melt and increased holding temperature significantly increase the rate of hydrogen solution, oxidation, and transient element loss. The mechanical properties of aluminum alloys depend on casting soundness, which is strongly influenced by hydrogen porosity and entrained nonmetallic inclusions.

Hydrogen influence on aluminum

Hydrogen is the only gas that is appreciably soluble in aluminum and its alloys. Its solubility varies directly with temperature and the square root of pressure. During the cooling and solidification of molten aluminum, dissolved hydrogen in excess of the extremely low solid solubility may precipitate in molecular form, resulting in the formation of primary and/or secondary voids.

Drossing fluxes are designed to promote separation of the aluminum oxide (Al2O3) dross layer that forms on the surface of the melt from the molten metal. Drosses and liquid or solid metal are usually intermingled in the dross layer. The drossing fluxes are designed to react with Al2O3 in the slag or dross layer and to recover metal. The fluorides wet and dissolve thin oxide films according to the general reaction.

Hydrogen Sources. There are numerous sources of hydrogen in aluminum. Moisture in the atmosphere dissociates at the molten metal surface, offering a concentration of atomic hydrogen capable of diffusing into the melt. The barrier oxide of aluminum resists hydrogen solution by this mechanism, but disturbances of the melt surface that break the oxide barrier result in rapid hydrogen dissolution. Alloying elements, especially magnesium, may also affect hydrogen absorption by forming oxidation reaction products that offer reduced resistance to the diffusion of hydrogen into the melt and by altering liquid solubility.

Hydrogen Porosity. Two types or forms of hydrogen porosity may occur in cast aluminum. Of greater importance is inter-dendritic porosity, which is encountered when hydrogen contents are sufficiently high that hydrogen rejected at the solidification front results in solution pressures above atmospheric. Secondary (micron-size) porosity occurs when dissolved hydrogen contents are low, and void formation is characteristically subcritical.

Finely distributed hydrogen porosity may not always be undesirable. Hydrogen precipitation may alter the form and distribution of shrinkage porosity in poorly fed parts or part sections. Shrinkage is generally more harmful to casting properties. In isolated cases, hydrogen may actually be intentionally introduced and controlled in specific concentrations compatible with the application requirements of the casting in order to promote superficial soundness.

Hydrogen in Solid Solution. The disposition of hydrogen in a solidified structure depends on the dissolved hydrogen level and the conditions under which solidification occurs. Because the presence of hydrogen porosity is a result of diffusion-controlled nucleation and growth, decreasing the hydrogen concentration and increasing the rate of solidification act to suppress void formation and growth. For this reason, castings made in expendable mold processes are more susceptible to hydrogen-related defects than parts produced by permanent mold or pressure die casting.

Hydrogen Removal. Dissolved hydrogen levels can be reduced by a number of methods, the most important of which is fluxing with dry, chemically pure nitrogen, argon, chlorine, and freon. Compounds such as hexachloroethane are in common use; these compounds dissociate at molten metal temperatures to provide the generation of fluxing gas.

Gas fluxing reduces the dissolved hydrogen content of molten aluminum by partial pressure diffusion. The use of reactive gases such as chlorine improves the rate of degassing by altering the gas/metal interface to improve diffusion kinetics. Holding the melt undisturbed for long periods of time at or near the liquidus also reduces hydrogen content to a level no greater than that defined for the alloy as the temperature-dependent liquid solubility.

Oxidation

Oxide Formation. Aluminum and its alloys oxidize readily in both the solid and molten states to provide a continuous self-limiting film. The rate of oxidation increases with temperature and is substantially greater in molten than in solid aluminum. The reactive elements contained in alloys such as magnesium, strontium, sodium, calcium, beryllium, and titanium are also factors in oxide formation. In both the molten and solid states, oxide formed at the surface offers benefits in self-limitation and as a barrier to hydrogen diffusion and solution. Induced turbulence, however, results in the entrainment of oxide particles, which resist gravity separation because their density is similar to that of molten aluminum.

Oxides are formed by direct oxidation in air, by reaction with water vapor, or by aluminothermic reaction with oxides of other metals, such as iron or silicon, contained in tools and refractories. Aluminum oxide is polymorphic, but at molten metal temperature the common forms of oxide encountered are crystalline and of a variety of types depending on exposure, temperature, and time. Some crystallographic oxide forms affect the appearance and coloration of castings, without other significant effects.

Oxide Separation and Removal. It is usually necessary to treat melts of aluminum and its alloys to remove suspended nonmetallics. This is normally accomplished by using either solid or chemically active gaseous fluxes containing chlorine, fluorine, chlorides, and/or fluorides. In each case, the objective is the dewetting of the oxide/melt interface to provide effective separation of oxides and other included matter and the flotation of these nonmetallics by attachment to either solid or gaseous elements or compounds introduced or formed during flux treatment.

Fluxes can also be used to minimize oxide formation. For this reason, melts containing magnesium are often protected by the use of salts that form liquid layers, most often of magnesium chloride, on the melt surface. These fluxes, termed covering fluxes, must be periodically removed and replaced. Carbon, graphite, and boron powder also effectively retard oxidation when applied to the melt surface.

Effects of Inclusions. In addition to oxides, a number of additional compounds can be considered inclusions in cast structures. All aluminum contains aluminum carbide (Al4C3) formed during reduction. Borides may also be present. By agglomeration, borides can assume sufficient size to represent a significant factor in the metal structure, with especially adverse effects in machining.

Under all conditions, inclusions whether in film or particle form are damaging to mechanical properties. The gross effect of inclusions is to reduce the effective cross section of metal under load. The more devastating effect on properties is that of stress concentration when inclusions appear at or near the surface of parts or specimens. Fatigue performance is reduced under the latter condition by the notch effect. Ultimate and yield strengths are typically lower, and ductility may be substantially reduced when inclusions are present.

Hard particle inclusions are frequently found in association with film-type oxides. Borides, carbides, oxides, and nonmetallic particles in the melt are scavenged and then concentrated in localized regions within the cast structure.

Structure Control

A number of factors define the metallurgical structure in aluminum castings. Of primary importance are dendrite cell size or dendrite arm spacing, the form and distribution of microstructural phases, and grain size. The foundryman can control the fineness of dendrite structure by controlling the rate of solidification.

Microstructural features such as the size and distribution of primary and intermetallic phases are considerably more complex dendrite cell size measurements are becoming increasingly important.

Grain Structure

A fine, equiaxed grain structure is normally desired in aluminum castings. The type and size of grains formed are determined by alloy composition, solidification rate, and the addition of master alloys (grain refiners) containing intermetallic phase particles, which provide sites for heterogeneous grain nucleation.

Grain Refinement Effects. A finer grain size promotes improved casting soundness by minimizing shrinkage, hot cracking, and hydrogen porosity. The advantages of effective grain refinement are:

  • Improved feeding characteristics
  • Increased tear resistance
  • Improved mechanical properties
  • Increased pressure tightness
  • Improved response to thermal treatment
  • Improved appearance following chemical, electrochemical, and mechanical finishing

Under normal solidification conditions spanning the full range of commercial casting processes, aluminum alloys without grain refiners exhibit coarse columnar and/or coarse equiaxed structures.

A fine grain structure also minimizes the effects on castability and properties associated with the size and distribution of normally occurring intermetallics. Large, insoluble intermetallic particles that are present or form in the temperature range between liquidus and solidus reduce feeding. A fine grain size promotes the formation of finer, more evenly distributed intermetallic particles with corresponding improvements in feeding characteristics. Because most of these more brittle phases precipitate late in the solidification process, their preferential formation at grain boundaries also profoundly affects tear resistance and mechanical properties in coarse-grain structures.

Porosity, if present, is of smaller discrete void size in fine-grain parts. The size of interdendritic shrinkage voids is directly influenced by grain size.

The finer distribution of soluble intermetallics throughout grain-refined castings results in faster and more complete response to thermal treatment. More consistent mechanical properties can be expected following thermal treatment.

Grain Refinement. All aluminum alloys can be made to solidify with a fully equiaxed, fine grain structure through the use of suitable grain-refining additions. The most widely used grain refiners are master alloys of titanium, or of titanium and boron, in aluminum. Aluminum-titanium refiners generally contain from 3 to 10% Ti. The same range of titanium concentrations is used in Al-Ti-B refiners with boron contents from 0.2 to 1% and titanium-to-boron ratios ranging from about 5 to 50. Although grain refiners of these types can be considered conventional hardeners or master alloys, they differ from master alloys added to the melt for alloying purposes alone.

To be effective, grain refiners must introduce controlled, predictable, and operative quantities of aluminides (and borides) in the correct form, size, and distribution for grain nucleation. Wrought refiner in rod form, developed for the continuous treatment of aluminum in primary operations, is available in sheared lengths for foundry use.

Aluminum Alloys: Terms, Definitions and Products

Aluminum alloys have numerous technical advantages that made them one of the dominant structural material families of the 20th century. Aluminum has low density (2.71 g/cm3) compared with competitive metallic alloy systems. It also has good inherent corrosion resistance because of the continuous, protective oxide film that forms very quickly in the air, and good workability that enables aluminum and its alloys to be economically rolled, extruded, or forged into useful shapes. In this article standardized terms and products made from aluminum alloys are described.

Profiles

Profile, section, shape: Wrought product, usually extruded, of uniform cross-section along its whole length and with a cross-section other than rod/bar, wire, tube, sheet or strip. They are usually supplied in straight lengths but sometimes in coiled form. Depending on the form of the cross-section, it can be called solid profile or hollow profile.

Extruded profile: Profile brought to final dimensions by extrusion.

Solid profile, solid section, solid shape: Profile in which the cross-section does not include any enclosed void.

Hollow profile, hollow section, hollow shape: Profile in which the cross-section includes either one enclosed void, provided that the cross-section is other than a tube, or more than one enclosed void.

Precision profile: Profile, which fulfils special requirements concerning tolerances on form and dimensions.

Rods/bars

Rod/bar: Solid wrought product of uniform cross-section along its whole length, supplied in straight lengths. Cross-sections are in the shape of circles, oval, squares, rectangles, equilateral triangles or regular polygons. Products with a square, rectangular, triangular or polygonal cross-section can have corners rounded along their whole length.

Extruded rod / bar: Rod or bar brought to final dimensions by extrusion.

Cold-drawn rod / bar: Rod or bar brought to final dimensions by cold drawing.

Brazing rod: Rod made of a low melting temperature alloy for use as filler metal in brazing.

Filler rod, welding rod: Rod for use as filler metal in joining by welding.

Square rod/bar: Rod or bar of a square cross- section.

Rectangular rod/bar: Rod or bar of a rectangular cross-section. The thickness of these rods exceeds one-tenth of the width. The term “rectangular rod/bar” includes “flattened circles” and “modified rectangles” of which two opposite sides are convex arcs, the other two sides being straight, of equal length and parallel.

Hexagonal rod/bar: rod or bar having the cross-section of a regular hexagon.

Wire

Wire: Wrought product of uniform cross-section along its whole length, supplied in coiled form. Cross-sections are in the shape of circles, ovals, squares, rectangles, equilateral triangles or regular polygons. Products with a square, rectangular, triangular, or polygonal cross-section can have corners rounded along their whole length.

The thickness of rectangular wires exceeds one-tenth of the width. Wire in the upper thickness range is often called “coiled rod”. The term “rectangular wire” includes “flattened circles” and “modified rectangles”, of which two opposite sides are convex arcs, the other two sides being straight, of equal length and parallel.

Drawing stock: Semi-finished solid wrought product of uniform cross-section along its whole length supplied in coils of a quality suitable to drawing into wire. Cross-sections are approximately round, triangular or regular polygonal with dimensions usually exceeding 7 mm.

Conductor wire: Wire possessing the requisite electrical and mechanical properties for use as an electrical conductor.

Filler wire, welding wire: Wire for use as filler metal in joining by welding.

Flattened wire: Wire produced by flattening round wire between rolls or by drawing through a die with flat opening.

Brazing wire: Wire of a low melting temperature alloy for use as filler metal in brazing.

Tubes

Tube: Hollow wrought product of uniform cross-section with only one enclosed void along its whole length, and with a uniform wall thickness, supplied in straight lengths or in coiled form. Cross-sections are in the shape of circles, ovals, squares, rectangles, equilateral triangles or regular polygons and can have corners rounded along their whole length, provided the inner and outer cross-sections are concentric and have the same form and orientation. Tubes can also be formed by piercing and by forming and joining sheet or strip.

Extruded tube: Tube brought to final dimensions by extrusions.

Drawn tube: Tube brought to final dimensions by cold drawing.

Porthole/bridge tube: Tube produced by extrusion of a solid billet through a porthole or bridge die. This tube is characterized by one or more seams formed by longitudinal bonding of two or more edges under pressure.

Seamless tube: Tube in which longitudinal bonding of edges is made by pressure, fusion or mechanical interlocking.

Welded tube: Tube formed from plate, sheet or strip with the abutting edges automatically welded.

Seam welded tube: Welded tube fabricated using filler wire.

H.F. seam welded tube: Welded tube fabricated from strip by use of H.F. current without filler wire.

Tube stock: Semi-finished tube suitable for the production of drawn tube.

The method of selection of aluminum windows and doors

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