Preheat Temperature Calculator
An engineering tool to determine the minimum preheat and interpass temperature required for welding carbon and low-alloy steels, based on AWS D1.1 and other standards.
Why is Preheating Necessary in Welding?
Preheating is the process of heating the base metal to a specific temperature before welding begins. This might seem counterintuitive—why heat something you're about to heat with a 6000°C arc? The reason is to control the **cooling rate** of the weld. When welding high-strength or thick steels, a rapid cooling rate can cause a brittle microstructure (martensite) to form in the Heat-Affected Zone (HAZ). If hydrogen is also present (from moisture in the electrode or atmosphere), it can lead to a catastrophic defect called hydrogen-induced cold cracking. Preheating slows down the cooling, allowing hydrogen to escape and preventing the formation of these brittle structures.