Why is preheating essential during welding of high-carbon equivalent pipeline steels?

Preheating is essential during the welding of high-carbon equivalent pipeline steels primarily to prevent hydrogen induced cracking (HIC) and to ensure adequate weldability. The carbon equivalent (CE) is a calculation that represents the hardening tendency of steel; higher CE values indicate a greater susceptibility to hardening and cracking during welding. High-carbon equivalent steels are more prone to forming a hard and brittle microstructure in the heat-affected zone (HAZ), the area surrounding th....