Main Difference – Alloy vs. Non Alloy Steel
Alloy and non alloy steel are chemical terms used to name two types of steel. Steel is a metal alloy. It is composed of iron and some other elements such as carbon. Non alloy steel has no elements added to steel when it is smelted. Steel is widely used all around the world due to several reasons such as low cost, easy production, strength, etc. There are different grades of steel available according to their properties. Alloy steel is a type of steel and has high amounts of other elements apart from iron and carbon. The main difference between alloy and non-alloy steel is that in alloy steel, other elements are added to iron during smelting whereas, in non-alloy steel, no elements are added during smelting.
Key Areas Covered
1. What is an Alloy Steel
– Definition, Properties
2. What is a Non Alloy Steel
– Definition, Properties
3. What is the Difference Between Alloy and Non Alloy Steel
– Comparison of Key Differences
Key Terms: Alloy, Alloy Steel, Carbon, Chromium, High Alloy Steel, Interstitial Alloy, Iron, Metal, Non-Alloy Steel, Low Alloy Steel, Smelting, Steel, Substitutional Alloy
What is an Alloy Steel
Alloy steel is a type of steel composed of iron, carbon and some other elements. The other elements present in it typically includes manganese, silicon, nickel, titanium, copper, and chromium. These elements are called alloy elements because they are mixed together to form an alloy. The purpose of adding these elements is to improve the properties of steel. Alloy steel can be divided into two categories as follows:
- Low alloy steel
- High alloy steel
There are two types of alloy steel as low alloy steel and high alloy steel. Low alloy steel has a low amount of alloy elements. High alloy steel has a high amount of alloy elements. Alloy steel is corrosion resistant due to the presence of elements such as chromium. Normally, alloy elements are added in order to improve the hardness and durability of the steel.
For example, stainless steel is an alloy steel. It contains about 10% of chromium along with iron and carbon in the mixture of elements. Due to its corrosion resistant property, stainless steel is used to manufacture kitchen items.
Figure 1: A wristwatch made out of stainless steel. Stainless steel is a good example of an alloy steel.
There are two main types of alloys as substitutional alloys and interstitial alloys. When a molten metal is used in the production of alloys, the size of the atoms will determine which type is going to be formed. If the atoms of the metals that are going to be mixed have relatively similar sizes, substitutional alloy type is formed, but if one type of metal atoms are smaller than the other type, an interstitial alloy is formed.
What is a Non Alloy Steel
Non alloy steel is a type of steel that has no other elements added during smelting. Smelting is the process of extraction of a metal from its ore. This process involves heating and melting the ore. Smelting removes impurities present in the iron ore. The smelting process is done several times in order to remove the carbon. If too much carbon is present, it is not a non-alloy steel. The carbon content should be dropped to about 1 %.
In the production of alloy steel, some elements such as chromium, cobalt are added to iron, but in the production of non-alloy steel, no other elements are added. Since there are no other elements other than iron and a little amount of carbon, non-alloy steel has a less durability and less flexibility. Therefore, this steel should undergo a process called tempering. Tempering is the process of heating iron at a high temperature in order to make it sensitive to cracking that take place during welding.
Figure 2: Fences made of wrought iron is a good example for an application of non-alloy steel. Wrought iron is considered a non-alloy steel due to its very little carbon content.
Non-alloy steel is used in the field of construction where metals with a high strength are required. Here, non-alloy steel bars are used to strengthen concretes, to make gates, fences, etc.
Difference Between Alloy and Non Alloy Steel
Definition
Alloy Steel: Alloy steel is a type of steel composed of iron, carbon and some other elements.
Non Alloy Steel: Non alloy steel is a type of steel that has no other elements added during smelting.
Presence of Carbon
Alloy Steel: Alloy steel is composed of a high amount of carbon.
Non Alloy Steel: Non alloy steel has less or no carbon content.
Smelting
Alloy Steel: Alloy steel are made by adding different elements during smelting.
Non Alloy Steel: No other elements are added during smelting in the production of non-alloy steel.
Corrosion
Alloy Steel: Alloy steel is less resistant to corrosion due to the presence of iron.
Non Alloy Steel: Non alloy steel highly undergoes corrosion due to the high amount of iron content.
Examples
Alloy Steel: Stainless steel is a good example of alloy steel.
Non Alloy Steel: Wrought iron is a good example of non-alloy steel.
Conclusion
An alloy is a mixture or a blend of two or more metallic components. It can be either homogeneous or heterogeneous. Alloy steel is a type of steel which includes iron, carbon and some other elements in its chemical composition. The main difference between alloy and non-alloy steel is that an alloy steel is composed of iron added with other elements during smelting whereas non-alloy steel has no added elements when it is smelted.
References:
1. The Editors of Encyclopædia Britannica. “Smelting.” Encyclopædia Britannica, Encyclopædia Britannica, inc., 30 Nov. 2016, Available here.
2. Bell, Terence. “What Are the Different Types of Steel?” The Balance, Available here.
3. Libretexts. “6.7A: Substitutional Alloys.” Chemistry LibreTexts, Libretexts, 12 Dec. 2016, Available here.
Image Courtesy:
1. “elegant wristwatch, metal, stainless steel” (Public Domain) via PIXINO
2. “Wrought Iron Fencing on Buckingham Palace Rd – geograph.org.uk – 1157492” By Nigel Mykura (CC BY-SA 2.0) via Commons Wikimedia
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