Metallurgy is the field of study of metals (ferrous and non-ferrous both), their extraction, processing, properties, application & further understanding of metals’ different behavior under varying conditions. Also, alloys come under the field of metallurgy. Alloy is a solid solution of one or more metals with one or more non-metals having metallic properties. Metallurgy is known to humankind for a very long time for thousands of years. Improvement of metallurgy will improve the human race because most things are made of alloys, not metals. People have this misconception and use the term metal more often, but the word alloy should be used because pure metals do not have the required mechanical properties to be used as any building materials.
Ores are found in natural abundance and contain our desired minerals along with impurities. It is important to remove these impurities from the ores to obtain the high-grade metals that we will use to cast different items. These impurities are called gangue and are usually removed by the various purification processes. The common flow of metal extraction from ores are as follows:
We’ll discuss these steps in detail.
The concentration of ores:
Concentration is when we remove the unwanted materials like sand, dust, etc., from the ores, so we get concentrated ore full of our required metals. It is also called dressing or benefaction. First, the physical and chemical properties of gangue and the metals are accessed. A suitable process is then used. Before going for concentration, the ores go through crushing and grinding to make the small size ores.
Different methods of concentration:
In this type of separation, the fundamental property of their specific gravities is used. The difference in the gravity of the gangue and the metal is used as the separation mechanism. In this gravity separation method, an upward stream of running water is used to wash away the lighter particles. And the heavier particles are found at the bottom.
In this method, the magnetic properties of the ores or gangue are used to separate them. A roller made of magnetic wheels is used to attract the magnetic particles in a different container. In contrast, the non-magnetic compounds are gone in a different container.
This method is extensively used to remove gangue from sulfide ores. In this method, the crushed ore is mixed with water to form a suspension. Froth stabilizers and collectors are added to the suspension. Collectors increase the unwettable quality of the mineral particles, and froth stabilizers make the froth stable. Oils make the mineral particles wet, while water soaks the gangue. A rotating paddle andair stirs the mixture in the process. Consequently, froth carrying the mineral particles is formed. The light froth is skimmed off and then dried for the recovery of the mineral particles.
It is likely to separate two sulphide ores by adjusting the proportion of oil to water or using ‘depressants’. In case of an ore containing ZnS & PbS, the depressant used is sodium cyanide. It selectively prevents zinc sulfide from coming to the froth but allows lead sulfide to come with the froth.
Extraction of Metals from Ores:
For extraction, various methods are used. We will study the roasting and calcination methods.
Eg: 2ZnS + 3O2 → 2ZnO + 2SO2
Fe2O3.xH2O(s)-à Fe2O3 (s) + xH2O(g)
ZnCO3 (s) -à ZnO(s) + CO2 (g)
Basic metallurgical processes in an important part of class 10th NCERT syllabus: We learn about the various ways employed to extract any pure metal from their naturally occurring ores. The ores are found with impurities called gangue, which needs to be separated before their use. Various methods of concentration, extraction, and purification are used to treat these ores.
The primary steps involved in any metallurgical process are;
The metallurgy is broadly divided into two parts.
The basic metallurgical processes are:
They form the backbone of modern aircraft and carriers, automobiles and engines, trains, ships & endless recreational vehicles; buildings; implantable devices; cutlery and cookware; coins and jewellery; firearms; and musical instruments.
The basic metallurgical properties that we should be concerned about upon extraction are as follows.
You can learn more about the basic metallurgical processes by checking on the explanatory videos with some real life examples on the MSVgo app.