Steel is a common metal that is used for several purposes because of its properties. It has lower cost, greater strength requires little energy for production, and can be completely recycled. All these properties make it one of the metals that are high in demand and environment friendly. It is used in several big and small applications such as structural applications, automobiles, medical instruments, for making large infrastructures, etc.
Steel is an alloy that is composed of iron, carbon, phosphorus, oxygen, silicon, and sulfur. It contains around 0.08-1.5% of carbon. It has good strength, hardness, durability, and flexibility.
Methods used for making steel:
Iron is heated to melt it in order to remove all the impurities and add other elements such as carbon, phosphorus, oxygen, silicon, and sulfur. There are 2 commonly used methods for steel production:
1. Blast Furnace Method
2. Electric Arc Furnace Method
Blast Furnace Method
This method was developed by Henry Bessemer who was an Englishman. This method involves blowing air for the purpose of oxidization through molten iron in order to remove impurities and producing steel.
The blast furnace used these days is a large cylindrical shaped steel that is made heat resistant by forming a layer of bricks. The iron is melted in the furnace which results in the release of oxygen from the top of the furnace and melted iron which also removes impurities at the same time is found at the bottom. The melted portion is then drained and the molten steel is taken out through a tap hole.
Electric Arc Furnace (EAF) Method
Electric Arc Furnace the method is for making special types of steel such as stainless steel, and steel that are used in aerospace and engineering applications. It can also be used for producing other types. The positive point about the electric arc furnace method is that it uses recyclable or scrap steel products which makes it an environment-friendly method.
In this method, the charged electrodes are used to heat and melt the scrap to which other elements are added for the desired alloy. Oxygen is released and impurities are removed and the molten steel can be taken out.
Types of Steel
According to the chemical compositions there are four types of steel
1. Carbon Steel
Carbon steel contains higher quantity of carbon as compared to other types of steel ranging from 0.3%-2.5%. It is divided into three types Low carbon steel (0.4-0.3% carbon content), Medium carbon steel (0.31-0.60% carbon content) and High carbon steel (0.60-2.5% of carbon content).
2. Stainless Steel
Stainless steel is a corrosion-resistant alloy, that contains chromium which protects it from rusting and corrosion. Stainless steel is available in different grades and different grades of stainless steel are suitable for different environments.
3. Alloy Steel
Alloy steel is carbon steel that is alloyed with one or more elements in amounts ranging from 1% to 50% by weight and can bring a change in its mechanical properties. Alloy steel has two categories; high alloy steel and low alloy steel. High alloy steel has a greater quantity of alloying elements and low alloying steel has a lower quantity of alloying elements around 1%-5%.
4. Tool Steel
Tool steel as the term suggests is a type of steel that is used for making tools. Its properties make it suitable for several applications such as corrosion resistance, hardness, good under high temperatures, and cryogenic toughness and maintains its shape. Tool Steel is available in different grades and forms.
All types of steel contain iron and carbon but it is the quantity of carbon and other elements that determine the grade of the steel.
Steel can be classified into several types depending on different factors other than a composition such as finishing method (hot rolled steel and cold rolled steel), Microstructure (Ferritic, Martensitic, etc.), Heat Treated (Annealed, Quenched and Tempered) etc.
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