Mining is one of the largest industries in Australia, contributing to 10.4% of Australia’s GDP in 2020. Australia is the greatest global producer of iron ore and bauxite, which are processed to form steel, aluminum and other metals such as gold, silver, zinc, and lead. Production of raw metals is the backbone of many industries like manufacturing, automobile, oil and gas. The manufacturing and automobile sectors use pure metals to fabricate products for industrial/commercial use. Industrial gas is used for treatment, cutting, and welding these metals into desired shapes. These are the procedures followed in metal production and fabrication by the industries.
- Extraction of Pure Metals
The first step in metal production is to extract raw mineral ores from the earth. The mineral ores are then processed to remove impurities and extract pure metal by a process called leaching. Metals can also be heated in a blast furnace to remove impurities that require gases like oxygen and carbon dioxide. Nitrogen gas is used to create an inert environment and remove other reactive gases during purification.
- Treatment of Raw Metals
After the extraction of pure metals like steel and aluminum from their ores, the next step is to strengthen the raw material. Often, original equipment manufacturers (OEM) have strength requirements for the raw material which they use and these goals are met by procedures like heat treatment. Although hard materials strengthen the product, they can be difficult to work with during manufacturing. But soft materials are not durable.
To harden them, these metals are heated in a controlled manner to the desired temperature, and then cooled slowly at a defined rate through a process called annealing, to increase softness. They are then tempered to make them brittle through the process of slow heating. Different industrial gases are used for this treatment:
- It is used to create inert environments which prevent the metal from reacting (oxidising) with the surroundings.
- It helps prevent overheating of metals.
- Metals are heated in the presence of nitrogen, which leads to the diffusion of nitrogen onto the metal’s surface to harden it (Nitriding).
- Inert gases (Argon, helium)
- They are used to create inert environments for non-ferrous metals like copper, brass, and aluminum.
- Helium is used in vacuum heat treatment.
- It is used to remove carbon from steel.
- It can create bright surfaces for processes like bright annealing.
- Fabrication of Metals into Desired Forms
In manufacturing, raw metals are modified into the shape of the final product. The final product must have the desired shape, accurate to its dimensions, and the desired strength. Raw metals come in standard shapes like cuboids (ingots), long bars with rectangular cross-section (billets), or sheets. Cutting and welding (fusing two metal pieces by melting the joint with heat) are the most common processes used in the processing of these metals.
Gases Used for Different Fabrication Processes
Gas cutting is a method which uses oxygen and fuel gases (like acetylene, propane, natural gas) to cut metals precisely.
Gases are used to perform multiple tasks during welding like:
- Heating – Hydrocarbons like Acetylene and Propane are used as a heat source (with oxygen gas) to heat the metal.
- Shielding – The region where metal is heated to weld must be shielded from the atmosphere to prevent its oxidation. Shielding gases also control the heating rate which in turn improves the quality of weld. Carbon dioxide, argon, helium and nitrogen are a few of the many gases used for welding.
Metal fabrication industries must hence invest in good quality industrial gas to produce strong and durable metals.