In our last article on industrial gases used in mining， we took a look at the mineral processing part and how gases are used to process minerals and metals. This part of the mining process is known as metallurgy.

Metallurgy is a process used to extract pure metals. It is a method used to purify a metal and turn it into an alloy， which is essentially a mixture of metals. For example， silver and copper are combined together to make pure silver， and copper and zinc to make brass.

Some of the most common gases used in the production of steel and metal industries are oxygen， nitrogen and argon. In this article， we will delve into the use of these gases and their role in metallurgy.

Oxygen

In the production of the steel industry， oxygen is the main component of the Basic Oxygen Process (BOP)， which takes place in a Basic Oxygen Furnace (BOF). This process involves blowing high-purity oxygen into a furnace filled with molten iron and other scrap to convert it into steel.

The oxygen causes a reaction that releases heat and oxidizes impurities， for example， carbon in the batch. Oxygen is inserted into the melt pool at ultra-high speed and the process lasts about 20 minutes， but it can vary.

This is done to reduce the carbon content of the steel itself， thus converting the hot metal into a liquid steel with a low carbon content. Other impurities present in large quantities in the steelmaking process are sulfur and phosphorus.

Sulfur and phosphorus are usually removed by transferring them to a calcium oxide rich stage using a basic oxygen furnace. After the impurities are removed， the molten steel is poured into molds to cool and iron alloys are added to improve the properties of the steel， such as strength and corrosion resistance.

Nitrogen

Nitrogen is commonly used in the annealing process of metalworking. Nitrogen annealing involves reducing the hardness and increasing the ductility of the metal through heat treatment. Annealing is an important process if you want to work with a metal that will not crack under pressure and that can be easily formed without using additional heat， for example in cold working.

Annealing essentially reduces the crystal structure in the metal. Annealed metals are usually more suitable for the production of electricity. Nitrogen mixtures are often used in the annealing process

Nitrogen is used as an inert gas to provide an inert atmosphere in the furnace during the heating and cooling process. Because of the oxidation and chemical reactions that occur when oxygen is used to blast in a furnace， this makes nitrogen a critical gas for neutralizing the environment.

Nitrogen is also used to replace any hazards in the atmosphere that have the potential to create an unstable or combustible environment prior to the actual annealing process.

Argon

When it comes to the use of argon in the steelmaking process， it is used along with oxygen in a process called argon-oxygen decarburization (AOD). This process occurs after the metal has been melted into liquid form.

The AOD process itself goes through three stages: decarburization， reduction and desulfurization.

In the decarburization process， the liquid metal is transferred to a vessel for further refining by injecting an argon-oxygen gas mixture. This vessel is very similar to the one used in the basic oxygen furnace.

Previously， we said that oxygen reduces the carbon content of the metal. By diluting the oxygen with argon， it reduces the pressure of oxygen and carbon monoxide and oxidizes only a small amount of the alloy， whereas without the presence of argon， a larger portion is oxidized.

As the carbon content decreases， more argon is added to produce a higher concentration of argon. After this， argon is used to help mix and remove the hydrogen and nitrogen elements.

Then， during the reduction and desulfurization stages， alloy， lime and fluorspar are added to help manage the slag， which is a by-product formed during this process. It is sometimes used in concrete or as a supplementary material for the production of roads.

Other elements are added during the desulfurization stage to dilute the sulfur and remove oxygen. After the desired level of sulfur is reached， the slag byproduct is removed and the container is then ready to be excavated and poured into the mold.