Understanding Carbon and Low Alloy Steel in Welding

Did you know that there are more than 3500 different grades of steel in the world? While all these grades have applications in some way or other, carbon steel and alloy steel are the most commonly used metallic materials in welding. 

Let’s understand them in detail.

Carbon Steel

Carbon steel is an alloy of iron, carbon, silicon, manganese and other elements.  However, the carbon amount is very high and other elements are in very low proportion. It is stronger and more durable than stainless steel. Stainless steel is an alloy of a minimum of 10.5% chromium.

Carbon steel has the following characteristics:

• Less resistance to corrosion

• High strength

• Low weldability

• Low melting points

• Low ductility

It can be further categorized into three main groups:

1. Ultra-Low Carbon Steel: It has very low carbon, usually less than 0.1%.

2. Low Carbon Steel: It has carbon up to 0.3%.

3. Medium Carbon Steel: It has carbon in the range of 0.31% and 0.6%.

4. High Carbon Steel: It has carbon of more than 0.6%.

Low Alloy Steel

Low alloy steel is similar to carbon steel. However, alloy steel composition has a high percentage of extra alloy elements such as chromium, molybdenum, and others.

The alloy steel properties are as under:

• Better corrosion resistance than carbon steel

• Low strength as compared to carbon steel

• High weldability

• High melting point

• High ductility

What is Low Alloy Steel Used for?

Alloy steel applications can be found in electric motors, pipelines, power generators, aircrafts, gears, spindles, auto parts and transformers. 

The classification of alloy steel fall under two categories:

1. Low Alloy Steel

Low alloy steel contains a low amount of alloy elements. It has better mechanical properties than basic carbon steel. The key purpose of low alloy steel is to increase the hardenability of steel. This ensures optimization of mechanical properties and toughness after they undergo heat treatment.

2. High Alloy Steel

High-strength low-alloy steel, also known as HSLA, contains a high amount of alloy elements. It is designed to provide higher corrosion resistance and improved mechanical properties than normal carbon steel. The high strength low alloy steel composition has specific mechanical properties rather than chemical properties.

There are various other types of alloy steel:

• Microalloyed steel

• Advanced high-strength steel (AHSS)

• Maraging steel

• Tool steel

How to Choose Alloy Steel Grades?

When choosing alloy steel grades, you need to bear the following factors in mind:

• Formability

• Weldability

• Machinability

• Corrosion resistance

• Need for the heat treatment process

• Tensile strength

The choice of carbon and low alloy steel depends on the welding requirements. You can get buy good quality carbon and low alloy steel from DnH Secheron, India’s leading welding material manufacturer.