By the end of this lesson, you should be able to:
The process for the extraction of metals in their natural form is called metallurgy. The compounds of metals that are found mixed with soil, sand, limestone, and rocks are called minerals. The extraction of metals from minerals for commercial purposes is cheap and requires minimum effort. These minerals are called ores. A substance is added to the charge in the furnace for purpose of removing impurities. This substance is called flux. Metallurgy involves the process of purification of metals as well as the formation of alloys.
Metallurgy also studies the chemical and physical behavior of metallic elements, inter-metallic compounds, as well as their mixtures called alloys. Metallurgy is different from metalworking. Metalworking is reliant on metallurgy. A person who practices metallurgy is called a metallurgist.
Metallurgy can be broadly grouped into physical metallurgy and chemical metallurgy. Physical metallurgy is concerned with the physical properties, physical performance, and mechanical properties of metals. Chemical metallurgy focuses on the oxidation and reduction of metals, and their chemical performance.
Historically, metallurgy has mainly focused on metal production. The production of metals begins with ore processing to extract the metal. This includes the mixing of metals to produce alloys. Metal alloys are mainly made up of a blend of two or more metallic elements. The study of the production of metals is classified into ferrous metallurgy and non-ferrous metallurgy.
Ferrous metallurgy involves alloys and processes that are based on iron. Non-ferrous metallurgy involves alloys and processes that are based on other metals apart from iron.
Traditional metallurgical processes include metal production, failure analysis, heat treatment, and joining of metals like soldering, brazing, and welding. Emerging areas in the field of metallurgy include nanotechnology, biomedical materials, electronic materials like semiconductors, as well as surface engineering.
The process of extracting metals from their ores and refining them for use is metallurgy. The following are the different steps in metallurgical processes or metal extraction.
Crushing and grinding. This is the first process in metallurgy. It involves crushing ores into a fine powder in a bar mill or crusher. This process is called pulverization.
The concentration of ores. This is the process of removing impurities from an ore. It is also called ore dressing. Below are various methods of concentration of ores.
Below is an illustration of the process of extraction of copper.
Extraction of metals. Extractive metallurgy involves the removal of valuable metals from ores and then refining them into a purer form. For you to convert a metal sulfide or metal oxide to a pure metal, you must reduce the ore chemically, physically, or electrolytically.
Refining and purification of impure metals. Metals such as aluminum, copper, and iron occur in nature in combined states. They can be in the form of carbonates, sulfides, or oxides. Metals extracted from their ores are not always in their pure form. They contain impurities that must be removed. The purpose of this process is to ensure that the metal produced is in its purest form. The process of purifying extracted metals is called refining. There are different methods of refining metals. The method used depends on the impurities present and their difference in properties with the metal being refined.
Other fields related to metallurgy include:
Common metals used in engineering include iron, copper, magnesium, zinc, nickel, titanium, silicon, and aluminum. These metals are mainly used as alloys with the exception of silicon. The iron-carbon alloy system is very common today. It includes cast irons and steel. Plain carbon steels have carbon as the only alloying element. They are used in high-strength, low-cost applications where neither corrosion nor weight is a major concern.
Stainless steel such as nickel alloys, galvanized steel, titanium alloys, or sometimes copper alloys is applied where resistance to corrosion is required.
Magnesium alloys and Aluminum alloys are mainly used where strong and lightweight parts are required like in aerospace and automotive engineering.
Copper-nickel alloys like Monel are applied in highly corrosive environments as well as for non-magnetic applications.
Nickel-based super alloys like Inconel are applied in high-temperature applications like turbochargers, pressure vessels, heat exchangers, and gas turbines.
Metals are shaped through processes like:
Cold working processes refer to altering the shape of a product by fabrication, rolling, or other processes, with the product still cold. This helps increase its strength, a process called work hardening.
Metals can be heat treated in order to change the properties of ductility, strength, toughness, resistance to corrosion, and hardness. The most common processes of heat treatment include tempering, quenching, and annealing.
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