Processes of Metallurgy - Introduction, Principles, FAQs

Metallurgy is the science and technology concerned with the properties of metals and their production and purification. It deals with the study of the physical and chemical behaviour of metallic elements, their intermetallic materials, and alloys. An alloy is a mixture, usually a solid solution containing at least one metallic element.

Combined State and Native State

Metals are found in nature mostly in two forms: the combined state and the native state. In the combined state, metals exist as compounds, very frequently as oxides, sulphides, or carbonates. Processing of these compounds to arrive at the pure metal is necessary. Example: iron mostly occurs as the ore Fe2O3, hematite, or Fe3O4, magnetite. Have you ever wondered how we get various metals like iron, gold, silver, aluminium, etc, and use them for a variety of purposes? Well in this chapter (General Principle and Process of Isolation of Metals) you will be introduced to how do we extract metals from their ores and how we process them for final use - Metals gave us weapons, tools, ornaments, utensils, etc. The ‘Seven metals of antiquity, are gold, copper, silver, lead, tin, iron and mercury.

To obtain a particular metal, we look for minerals. Minerals are basically naturally occurring chemical substances in the earth's crust that are obtained through mining. Out of many minerals in which a metal may be found, only a few are viable to be used as a source of that metal. Such minerals are known as ores.

Rarely, does an ore contain only a desired substance. It is usually contaminated with earthly or undesired materials known as gangue.

Metallurgy is a process of extracting metals from their ores and modifying the metals as per their needs. Metallurgy usually refers to the commercial method of extracting metals as opposed to laboratory methods. It also deals with the chemical, physical, and atomic properties and structures of metals and alloys (mixture of metals).

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Types of Ores

Ores are rocks that naturally occur to contain sufficient quantities of minerals having important elements like metals. Getting metal ores forms a very vital part of metallurgy. Different examples of ores can be commonly classified as:

• Oxide Ores: Normally, in these ores, the metal is combined with oxygen. Examples include bauxite, which is aluminium ore, and hematite, which is iron ore.
• Sulphide Ores: In these ores, metals are combined with sulphur. Examples include galena (lead ore) and chalcopyrite (copper ore).
• Carbonate Ores: These ores contain metals combined with carbonates. Examples include calcite (calcium ore) and dolomite (magnesium ore).

Principle of Metallurgical Extraction

General Principles

The process by which metals are extracted from their ores and prepared for use is built upon some very basic principles of chemistry and physics. These include:

• Reduction: This is when metal oxides are reduced to pure metal by losing oxygen. The removal of this oxygen from the metal oxide is most commonly done using carbon, in the form of coke, in a blast furnace, particularly for iron.
• Electrolysis: It is used for metals that are too reactive for reduction with carbon. Metals like aluminium are reduced by electrolyzing alumina dissolved in molten cryolite.
• Thermal Decomposition: Some metal carbonates, on heating, decompose to yield metal oxide and carbon dioxide which then can be reduced to metal.

Process in Metallurgy

Concentration of Ore

The ore is at first concentrated to remove impurities. Depending upon the nature of the ore techniques like froth flotation, magnetic separation, and gravity separation are used.

Extraction of Metal

The concentrated ore is then treated with various processes for extracting metal:

• Pyrometallurgy: The process of heat treatment for minerals and metallurgical ores and concentrates. Physical and chemical changes are induced in the materials to allow the recovery of useful metals. For example, smelting and roasting.
• Hydrometallurgy: The application of aqueous chemistry in the recovery of metals from ores, concentrates, and used or scrap material. Leaching and precipitation constitute the hydrometallurgical common processes.
• Electrometallurgy: Electrical energy drives the extraction of metals from ores or solutions. Some common examples include electrorefining and electrowinning processes.

Refining of Metal

The extracted crude metal is further refined to get rid of impurities. This can be achieved in a number of ways, such as:

• Distillation: Applied when the boiling point of metals like zinc and mercury is low.
• Liquation: The fusible metal is separated from the less fusible one through melting.
• Electrolytic Refining: Impure metal is made on the anode and pure metal is deposited on the cathode.

Related Topics Link,

• Calcination and Roasting
• Distillation
• Difference between Metallic and Non Metallic Minerals
• Filtration

Applications and Relevance of Metallurgy

Metallurgy has such a deep impact in various industries and on our everyday life. It speaks for its applications, extending from producing basic household items to advanced technological innovations.

Industrial Applications

• Construction: An alloy of iron, namely steel, is a core material in construction.
• Transportation: Aluminium and steel metals are widely used in the construction of various means of transport, including aircraft, automobiles, and ships, because of their strength and light qualities.
• Electronics: Precious metals, such as gold and silver, along with copper, play a very important role in electronics. They show good conductivity and are at the same time resistant to corrosion.

Inventions and Innovations

• Material Science: As a significant part of metallurgy, it deals with developing new material grades with improved properties for a wide range of applications, such as from space industries to medical apparatus.
• Sustainable Practices: Improvements in metallurgy are of key interest for recycling metals that lessen the ecological impacts caused by mining and metal production processes.

Recommended topic Video on ( Metallurgy)

Some Solved Examples

Example 1

Question:
The seven metals of antiquity are:

1) Gold

2) Copper

3) Iron

4) All of them

Solution:
The ‘Seven metals of antiquity are gold, copper, silver, lead, tin, iron, and mercury.

Hence, the answer is option (4).

Example 2

Question:
An ore usually contains undesired impurities, which is known as:

1) Flux

2) Slag

3) Gangue

4) None of the above

Solution:
An ore rarely contains only a desired substance. It is usually contaminated with earthly or undesired materials known as gangue.

Hence, the answer is option (3).

Example 3

Question:
In metallurgy, the term "gangue" is used for:

1) Contamination of undesired earthy materials.

2) Contamination of metals other than the desired metal.

3) Minerals which are naturally occurring in pure form.

4) Magnetic impurities in an ore.

Solution:
An ore rarely contains only a desired substance. It is usually contaminated with earthy or undesired material, known as gangue. So, in metallurgy, the term "gangue" is used for the contamination of undesired earthy materials.

Hence, the answer is option (1).

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Summary

Metallurgy provides core materials for an infrastructure-based industry and technology, from construction to transport and electronic gadgets. This paper has thrown light on the occurrence of metals in combined and native states, types of ores, principles, and processes involved in metallurgical extraction. The relevance of metallurgy to real-life applications and how it affected industrial and technological advancement is discussed.Knowing how metallurgy works allows new continuous material and technique development and hence progress in many other fields towards a sustainable future.

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