Nickel, a valuable and versatile metal, is not only scarce but also challenging to extract and refine. With an ore grade that is notably low, producing just one ton of nickel requires a staggering 260 tons of nickel ore, and the refining process is significantly more complex than that of copper. This article delves into the fascinating world of scrap nickel, exploring its classification, identification, and uses, while highlighting some lesser-known statistics and facts about this precious metal.
Nickel stands out for its magnetic properties at room temperature, which vanish when heated to 350°C. Its applications are diverse and essential across various industries. Nickel plating, for instance, is a common method to prevent corrosion on metal products, including medical and surgical appliances, which require a nickel coating for easier disinfection. The metal is also a key component in the creation of numerous alloys, such as high-alloy nickel-containing stainless steel, heat-resistant steel, precision alloy, and permanent magnets. These alloys are indispensable in telecommunications, instrumentation, medical, metal powder, and chemical industries due to their high heat resistance, corrosion resistance, and excellent plasticity.
According to the Nickel Institute, the global demand for nickel in stainless steel alone accounted for approximately 74% of total nickel usage in 2019. This highlights the metal's critical role in modern manufacturing and technology.
Scrap nickel is categorized based on its nickel content and can be divided into three main types:
Pure nickel scrap includes sheets, bars, ingots, and powders with a nickel content ranging from 97% to 99%. This form of nickel is characterized by its silver-white color with a slight greenish tinge, lustrous appearance, and magnetic properties. It is soft, tough, and has a fine, dense structure. Pure nickel typically comes from producers who use nickel as a raw material.
Hetero nickel is a more complex category, encompassing nickel alloys with over 25% nickel content. This group includes nickel-iron, nickel-chromium, nickel-chromium-iron, nickel-chromium-tungsten, molybdenum-iron, nickel-copper, nickel-copper-iron, and nickel-copper-manganese alloys, among others.
To identify different types of scrap nickel, one can use the grinding spark test, where a sample is ground on a fast wheel, and the color of the sparks helps determine the alloy type. Chemical qualitative methods are also employed, involving dissolving a sample in aqua regia and observing the resulting color to identify the alloy. Nickel wire, powder, plate, and belt, often found as leftovers in telecommunications equipment and electroplating factories, exhibit a silvery white surface that turns slightly greenish upon oxidation. When ground, they produce fuchsia sparks and are magnetic.
Pure nickel scrap can be directly used as raw material for various industrial applications or for smelting nickel alloy plating. Waste hetero nickel, including old and new nickel coins, can be recycled into the same grade alloy if its composition is clearly identified. If the grades are indistinguishable and free of elements like cobalt, copper, tungsten, and molybdenum, the scrap can be used to smelt nickel-chromium stainless steel. Complex compositions may be repurposed as raw material for rolling drums. Additionally, nickel-containing waste water, residues, and sludge can be processed to extract chemical raw materials such as nickel oxide, chloride, nitrate, sulfate, and hydroxide, although the extraction process is technically demanding and costly.
For more detailed information on nickel and its applications, the Nickel Institute provides a wealth of resources and industry insights.
Source: Adapted from information available on the Metal Heaven Chemical Products website.
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