Aluminum instead of copper

The concept of “aluminum instead of copper” was introduced after the 1960s, when copper resources were limited and expensive, while aluminum, which is the closest to copper in terms of performance, was abundant and inexhaustible. Aluminum-magnesium-silicon alloy is the most used aluminum alloy in wire and cable, as 6101 and 6201 alloy, state T1 and T4. 2020, the amount of this aluminum alloy in the world is more than 5000kt, and the amount in China is expected to be more than 1600kt, accounting for about more than 30% of the total consumption. Russia is developing nano-microstructure wire aluminum alloy with tensile strength of 320MPa-370MPa and electrical conductivity of 57.2% IACS-56.1% IACS (International Annealed Copper Standard). Copper resources in China are relatively scarce, and copper is indispensable in the production of certain components or products. Therefore, copper must be cherished and the work of “aluminum instead of copper” must be done effectively.

Copper and aluminum performance comparison

Copper is one of the earliest metal elements used by human beings. Copper is purple-red in color, high thermal and electrical conductivity, good conductor; does not oxidize in dry air, will form copper green in wet air containing CO2; reacts slowly with alkaline solutions, but easily forms complexes with ammonia; standard electrode potential is +0.337V, cannot displace hydrogen in acid, but can be dissolved in acid with oxidation, the electrochemical equivalent of divalent copper is 0.0003294g/C ( Coulomb). The extraction, processing, recycling and reuse of copper is not difficult, therefore, from the primitive society to the civilization prosperous, highly developed science and technology today, copper products have been accompanying mankind, making a significant contribution to the progress of mankind.

Aluminum is a relatively young metallic element. in 1746, the German scientist J.H. Pott made alumina from alumina. in 1807, the English chemist H. Davy attempted to make aluminum by electrolysis of molten alumina and in the following year gave the expected metal the name Alumium, which was later changed to Aluminium, i.e. aluminum. in 1825, the Danish chemist H.C. Oersted obtained a few milligrams of aluminum by reducing anhydrous alumina with potassium amalgam. in 1827, the German scientist F. Wohler obtained a small amount of aluminum by reducing alumina with potassium. in 1854, the French scientist S.C. Deville made aluminum by reducing NaAlCl4 with salt with sodium and produced some royal articles, such as In 1884, the total output of aluminum in the United States was 56.7 kg. In 1886, Hall, an American university student, and Heroult, a French university student, invented the method of aluminum refining by electrolysis of cryolite-alumina dissolved salt almost simultaneously, announcing the birth of the industrial extraction process of aluminum, and they obtained patents for their inventions in the United States and France respectively.

In 1888, Hall founded the Pittsburgh Metallurgical Company in Pittsburgh, the world’s first aluminum electrolysis plant, and produced the first commercial aluminum. The company manufactured household items such as aluminum teapots and made several aluminum alloys. From 1888 to 1893, the price of aluminum ingots dropped from $10.70/kg to $1.72/kg. around 1990, aluminum foil, wire and cable were also introduced.

The standard electrode potential of aluminum is -1.662V, and the electrochemical equivalent is 0.3356g/(A-h). The density of aluminum is only 30.13% of that of copper, therefore, replacing copper with aluminum can significantly reduce the mass of the workpiece, thus saving energy and reducing greenhouse gas emissions.

Is it feasible to replace copper with aluminum?

“Aluminum instead of copper” does not mean using aluminum instead of copper in all fields and sectors, but mainly means using aluminum instead of copper to produce conductive and thermally conductive (heat dissipation) parts.

Aluminum is about 70% lighter than copper, which reduces the mass of the workpiece and thus makes it easier to install. As early as the beginning of the 20th century, aluminum was used to replace copper in the production of high-voltage lines, so that the tension on wires and poles (towers) was greatly reduced. The automotive and aviation industries have also adopted aluminum conductors. the Airbus A380 aircraft, the world’s largest passenger aircraft manufactured by Airbus Europe, with a capacity of about 800 people, has aluminum conductors all over the aircraft.

But is it safe to use aluminum conductors instead of copper in your home? As it turns out, it is safe and there is nothing to worry about at all. North America has been converting residential electrical wiring to aluminum on a large scale since the mid-1960s. In other parts of the world, the “aluminum wire in the home” time is earlier. Aluminum wire emerged around 1990, when Alcoa made wire from the aluminum it extracted.

In what ways is aluminum inferior to copper

It must be admitted that aluminum is inferior to copper in some respects.

The electrical conductivity of aluminum is lower than that of copper. 99.990% Al has a resistivity of 2.6548 x 108Ω-m at 20° and an equivalent volume conductivity of 64.94% IACS. Therefore, a larger diameter aluminum wire must be used to make the conductivity of aluminum wire comparable to that of copper wire.

The hardness of aluminum is lower than that of copper. 99.5% Al annealed state Vickers hardness is about 200MN/m2, which is much lower than that of copper. The electrician’s experience is that after stripping the insulation from the wire, aluminum wire is more likely to produce cuts, dents, indentations, etc. than copper wire. Therefore, it is advisable to take extra care when stripping, butting and wiring aluminum wire, otherwise, the wound may become an overheating point and cause overheating.

The coefficient of thermal expansion of aluminum is greater than that of copper. When an electric current passes through the wire, the wire heats up. In the repeated heating expansion and cooling contraction, the aluminum wire will produce creep, which causes loose connections and overheating.

Aluminum oxide has poor electrical conductivity. Copper wire rust is not a big problem, because copper oxide conductive, copper wire can still work properly. But the aluminum line rust formed by aluminum oxide is not a good conductor of electricity, the current has a blocking effect, easy to cause overheating. The problem occurs mainly at the connections, such as sockets, closures, clamps, device connection points, distribution boards, etc. The solution is to use professional connectors.

In recent years, the electric vehicle market has become an investment hotspot. In order to reduce CO2 emissions and cable usage, electrical wiring has become a key issue. Therefore, the switch to the patented 1XXX, 6XXX and 8XXX series alloys replaced pure electrical aluminum EC (Pure EC Grade Aluminium, 99.7% Al). This trend was already seen in Europe 20 years ago, when some companies started to use Aluflex 137050 aluminum alloy and standard electrical alloy EC Grade 1370-Conductal 137050 aluminum alloy to manufacture aluminum battery cables for automobiles. In order to reduce the net mass of the car, some Japanese car companies advocate the use of aluminum wire instead of copper wire, with the goal of reducing 20kg, which is now close to this goal.

History of aluminum wire applications

Aluminum wire was first used as a commercial communications wire in 1944 for lines between Washington, D.C., and Baltimore, Maryland, in the United States.

In the early days, cable wire was drawn from iron, which was difficult to produce. In order to improve efficiency, factories dipped a layer of copper sulfate on the surface of iron wire as a lubricant, and production efficiency was greatly improved, so copper wire was used instead. in 1913, the International Electrotechnical Commission developed the IACS, which identified copper as having a conductivity of 100% IACS.

In 1930, PVC-insulated aluminum cables were tried in Germany. At the end of the Second World War, synthetic rubber and polyethylene cables became widely used, and in the 1950s, PVC was used commercially in many fields, especially in household cables, where “aluminum instead of copper” became almost universal. For a long time, most of the aluminum cable is made of 99.5% pure industrial aluminum AA1350.

The new era of aluminum cable

In the initial production of aluminum wire and cable, the 8000-series aluminum alloy was used. Alcoa did a lot of work in pioneering aluminum alloys for conductors, and the first 8000-series alloy was patented in 1972, followed by AA8030 alloy in 1973 and AA8176 alloy in 1975. Their mechanical properties were equivalent to those of copper, marking the dawn of a new era for aluminum wire and cable.

In the late 1940s, Properzi (Properzi) aluminum wire rod continuous casting and rolling process and equipment into the market for continuous casting and rolling of non-ferrous metal wire rod, the first production is the market in need of pure aluminum wire rod; after meeting the pure aluminum wire rod market demand, and then into the aluminum alloy wire rod market. Successively launched products are AAC (all-aluminum conductors, All-Aluminium Conductors), AAAC (all-aluminum alloy conductors, All Aluminium Alloy Conductors), ACAR (alloy reinforced aluminum conductors, Aluminium Conductor Alloy Reinforced Aluminium Conductor Aluminium Clad Steel Reinforced), ACSR/TW (Steel Reinforced Shaped Wire Aluminium Conductor, Steel Reinforced), ACSS/AS (Aluminium Conductors-Aluminium Clad Steel Core) Aluminium Conductors-Aluminium Clad steel suported), ACCC (Aluminium Conductor Composite Core), High Thermal and HTLS conductors (High Thermal and HTLS). Conductors).

With the development of production technology and the expansion of applications, the above aluminum conductors have also had greater development, more varieties, a wider range of applications. For example, a variety of composite AAC aluminum stranded wire, mainly used in low-voltage lines and substation connection lines; aluminum alloy core of AAAC stranded wire, mainly used in low, medium and high-voltage lines and extra-high voltage overhead lines; core wire for aluminum-magnesium-silicon alloy high-strength wire and 1350 wire ACAR stranded wire, the number of stranded strands determined by the design; ACSR stranded wire, steel core wire after plating, the outer layer of 1 layer or multi-layer cold-drawn 1350-H19 aluminum wire; AACSR steel-core aluminum alloy wire with steel core wire plated and stranded outer layer, mainly used in medium voltage, high voltage and extra high voltage overhead lines; ACSR/AS steel-core stranded wire with mechanical properties comparable to ACSR stranded wire. However, the steel core is covered with aluminum, thus, the load capacity is higher and the corrosion resistance is strong. These wires can be used in harsh corrosive environments; ACSR/TW (shaped aluminum wire with steel core), stranded shaped 1350-H19 wire on top of high-strength steel wire; ACSS/AS (aluminum wire – aluminum clad steel), with steel as the core, aluminum wrapped around the steel core, and then stranded with 1 or more layers of 350-0 aluminum wire as one composite cable; ACCC ( composite core aluminum cable), the core is a lightweight, high-strength carbon fiber and glass fiber reinforced thermal resin, prepared using advanced technology, the core is trapezoidal completely annealed around the high-efficiency aluminum wire; steel core heat-resistant aluminum alloy wire TACSR, which is similar to the structure of conventional ACSR wire, but the conventional ACSR wire using EC Grade Aluminium (EC Grade Aluminium) wire, while TACSR wire is made of cold-drawn heat-resistant aluminum alloy wire TAL, which can operate safely at 210°C or higher for long periods of time; GZTASCR (Thermal resistant aluminium conductors steel reinforced with GAP), which has a steel core reinforced with gaps. The steel core of this conductor is separated from the first layer of trapezoidal heat-resistant aluminum alloy wire by a non-thick gap that enables the steel core wire to withstand the stretching generated during installation, and the gap is filled with heat-resistant lubricating resin.

Properzi Continuous Casting and Rolling Line

The Italian Properzi Continuous Casting and Rolling line (Properzi CCR line) was developed by Properzi. At present, more than 75% of the world’s steel and aluminum conductors are produced by this process or similar processes. The Properzi continuous casting and rolling line for aluminum conductors consists of 13 parts.

After years of research and development, Propazi can provide CRE (Continuous Rotary Extrusion, Continuous Rotary Extrusion) technology and Propazi Forming Machine (Pro-Form, i.e. Properzi Forming Machine), which can produce and process shaped aluminum wire (trapezoidal wire), fan-shaped aluminum cable and wire, aluminum profile/bus bar, aluminum tube, aluminum clad steel wire, etc.

Russia develops aluminum alloy for nanotissue wire

In 2020, the world’s total consumption of about 5,000kt 6XXX series wire and cable aluminum alloy, that is, aluminum-magnesium-silicon system of 6101 and 6201 alloy, state T1 and T4. the tensile strength of this alloy is 150MPa-220MPa, specific resistance of 0.034Ω-mm2/m- 0.0360Ω-mm2/m, conductivity equivalent to 50.0% IACS-47.9% IACS, and are widely used in the field of overhead lines and ordinary wires. However, the industry would like to produce an alloy with better properties than 6101-T4 alloy to extend the line tower distance. 6101 alloy’s typical composition (mass %) is: Si 0.54, Fe 0.23, Cu 0.003, Mg 0.58, Zn 0.01, B 0.002, (Ti+V+Cr+Mn) 0.012, Al balance; typical properties are: tensile strength 195MPa, elongation 28%, specific resistance 0.03420Ω-mm2/m, conductivity equivalent to 50.4% IACS.

In order to improve the performance of aluminum alloys for wires in general, scientists from United Aluminum of Russia and some universities and research institutes have developed nano-microstructured wire rods with specimens with tensile strength of 320MPa-370MPa and electrical conductivity equivalent to 57.2% IACS-56.1% IACS.