Key difference - alloyed vs. unalloyed steel
Alloyed and unalloyed steel are chemical names for two types of steel . Steel is a metal alloy . It is made up of iron and some other elements like carbon. In the case of unalloyed steel, no elements are added to the steel during melting. Steel is used all over the world for various reasons, such as low cost, ease of manufacture, strength, etc. There are different types of steel according to their properties. Alloy steel is a type of steel and, in addition to iron and carbon, contains a high proportion of other elements. The main difference between alloy steel and mild steel is that in alloy steel, other elements are added to the iron during melting, while in mild steel, no elements are added during melting.
Key areas covered
1. What is an alloy steel - definition, properties 2. What is a mild steel - definition, properties 3. What is the difference between alloy and mild steel - comparison of the main differences
Key Terms: Alloy, Alloy Steel, Carbon, Chromium, High Alloy Steel, Interstitial Alloy, Iron, Metal, Unalloyed Steel, Low Alloy Steel, Smelting, Steel, Substitute Alloy
What is an alloy steel?
Alloy steel is a type of steel made up of iron, carbon, and a few other elements. The other elements contained therein typically include manganese , silicon , nickel , titanium , copper and chromium . These elements are called alloying 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 proportion of alloying elements. High- alloy steel has a high proportion of alloy elements. Alloy steel is resistant to corrosion due to the presence of elements such as chrome. Alloying elements are usually added to improve the hardness and durability of the steel.
For example, stainless steel is an alloy steel. It contains about 10% chromium along with iron and carbon in the mix of elements. Due to its corrosion-resistant property, stainless steel is used in the manufacture of kitchen items.
Figure 1: A stainless steel wristwatch. Stainless steel is a good example of an alloy steel.
There are two main types of alloys as replacement alloys and interstitial alloys . When a molten metal is used in making alloys, the size of the atoms determines which type is formed. When the atoms of the metals to be mixed have relatively similar sizes, a type of substitution alloy is formed, but when one type of metal atom is smaller than the other type, an interstitial alloy is formed.
What is a carbon steel?
Unalloyed steel is a type of steel to which no other elements are added when it is melted. Smelting is the process of extracting a metal from its ore. This process involves heating and melting the ore. Smelting removes any impurities in the iron ore. The melting process is carried out several times to remove the carbon. If there is too much carbon, it is not a mild steel. The carbon content should be reduced to around 1%.
In the manufacture of alloy steel, some elements such as chromium and cobalt are added to the iron, but in the manufacture of unalloyed steel no other elements are added. Since there are no other elements besides iron and a small amount of carbon, unalloyed steel is less durable and less flexible. Therefore, this steel should be subjected to a process known as tempering. Tempering is the process of heating iron to a high temperature to make it susceptible to cracking during welding.
Figure 2: Wrought iron fences are a good example of a mild steel application. Wrought iron is considered to be unalloyed steel due to its very low carbon content.
Mild steel is used in construction where metals with high strength are required. Here, non-alloy steel bars are used to reinforce concrete, gates, fences, etc.
Difference between alloyed and unalloyed steel
definition
Alloy steel: Alloy steel is a type of steel made up of iron, carbon, and some other elements.
Non-alloy steel: Non-alloy steel is a type of steel to which no other elements are added during melting.
Presence of carbon
Alloy steel: Alloy steel consists of a high proportion of carbon.
Unalloyed Steel: Unalloyed steel has little or no carbon content.
Melt
Alloy Steel: Alloy steel is made by adding various elements during melting.
Mild Steel: In the manufacture of Mild Steel, no other elements are added when it is melted.
corrosion
Alloy steel: Alloy steel is less resistant to corrosion due to the presence of iron.
Unalloyed steel: Unalloyed steel is subject to severe corrosion due to its high 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.
diploma
An alloy is a mixture or a mixture of two or more metallic components. It can be homogeneous or heterogeneous. Alloy steel is a type of steel that contains iron, carbon and some other elements in its chemical composition. The main difference between alloy and mild steel is that alloy steel is made of iron to which other elements are added as it melts, while mild steel does not contain added elements when it is melted.
References:
1. The editors of the Encyclopædia Britannica. "Melt." Encyclopædia Britannica, Encyclopædia Britannica, inc., November 30, 2016, Available here . 2nd bell, Terence. “What are the different types of steel?” The scales, available here . 3. Free texts. “6.7A: Substitute Alloys.” Chemistry LibreTexts, Libretexts, Dec. 12, 2016, available here .
Image courtesy:
1. “Elegant wristwatch, metal, stainless steel” (Public Domain) via PIXINO 2. “Wrought iron fence on Buckingham Palace Rd - geograph.org.uk - 1157492” By Nigel Mykura (CC BY-SA 2.0) via Commons Wikimedia
