CARBON STEEL

Carbon steel is composed of a mixture of two main elements metal (iron) and non-metal (carbon). However, it may contain some other alloying elements such as cobalt manganese, and nickel, marking the desired capacity.

Carbon steel 

carbon steel can be classified as follows:

Low carbon steel

Medium Carbon Steel

High Carbon Steel

Carbon content

As the carbon percentage increases, steel has the ability to become hard and strong through heat treatment; however, it becomes less ductile. Despite the heat treatment, a high carbon content reduces weldability. For example:

Carbon content in low carbon steel is 0.5 to 0.30%.

Carbon content in Medium carbon steel is 0.30 to0.50%

Carbon content in High carbon is 0.50 to1.50%

Low Carbon Steel

Low carbon steel can be mechanized easily. It is also divided into grades according to different amounts of carbon such as

With 0.05 to0.15% carbon content, rivets, screws, presses, sheets, pipes, nails, and chains can be manufactured.

With 0.15 to0.30% carbon content, Plates, structural shapes, and bars can be manufactured. With a melting point (1539 to 1515) degrees centigrade, low-carbon steel can be machined easily. It is also relatively inexpensive.

Weldability

At present, low carbon steel is the most commonly used material just because of its strength and comparatively inexpensive. Low carbon steel can be welded by almost all welding processes such as:

Oxy-acetylene welding

Flux shielded metal arc welding

Gas metal arc welding

Submerged arc welding

Plasma arc welding

Thermit welding

Resistance welding

Electroslag welding

Brazing 

Medium Carbon Steel

Welding of medium carbon steel is comparatively difficult due to the high carbon content that can cause weld brittleness. The melting point of High carbon steel is 1515℃ to1492℃, and it is harder than low carbon steel.
Medium carbon steel has a carbon content of 0.30% to 0.50%. During welding, the weld hardens into the joint and forms martensite in the heat-affected zone due to rapid cooling which may cause cracking. This can be avoided by using special welding techniques and appropriate electrodes.
Medium carbon steel can be welded by the following processes:

•  Shielded Metal Arc Welding.
• Oxy-acetylene Welding
• Resistance Welding.
• Thermit Welding
• Submerged Arc Welding.

High Carbon Steel

High carbon steel has a welding range due to its high carbon content, the melting point of high carbon steel is 1492–1405.
Originally high carbon steel is welded for repair purposes using the following welding processes:

• Resistance Welding
• Thermit Welding
• Shielded Metal Arc Welding
• Oxyacetylene welding

ASTM code for Carbon Steel

Pipes:-

ASTM A53 Gr. A/B, ASTM A106 Gr. A/B/C, ASTM A333 Gr.1/Gr.6,

Tubes:- 
  ASTM A178/179/192, ASTM A334 Gr.1/6.

Wrought Iron fittings :-

ASTM A234Gr.WPA/B, ASTM A420 Gr.WPL6

Forged Fittings:-ASTM A181. ASTM A105, ASTM A350 LF1/2.

Cast Fittings:-ASTM A216, ASTM A352 LCB/C.

Plates: -ASTM A285, ASTM A515, ASTM A516.