Summary Recommended preheat values are based on prevention of hydrogen cracking for hydrogen contents up to 15mL/100g of weld metal The preheat values provided in AS/NZS 1554 are very conservative if low hydrogen consumables or processes are used for welding. Welding can generally be safely done with no risk of hydrogen cracking at ambient temperatures providing that H5 FCAW consumables are used, or welding is done using a low hydrogen process like GMAW. How much preheat is actually necessary for structural steel? There are 3 fundamental main reasons for preheating Prevent hydrogen cracking Prevent formation of hard HAZ Improve fusion Standards such as AS/NZS 1554.1 are used to determine the required preheat based on material group, heat input and combined joint thickness. But what is the basis for the minimum preheat temperature calculations in standards? Where did they come from? The short answer is Hydrogen Assisted Cold Cracking (HACC) prevention! The reality is t...
Summary Recommended preheat values are based on prevention of hydrogen cracking for hydrogen contents up to 15mL/100g of weld metal The preheat values provided in AS/NZS 1554 are very conservative if low hydrogen consumables or processes are used for welding. Welding can generally be safely done with no risk of hydrogen cracking at ambient temperatures providing that H5 FCAW consumables are used, or welding is done using a low hydrogen process like GMAW. How much preheat is actually necessary for structural steel? There are 3 fundamental main reasons for preheating Prevent hydrogen cracking Prevent formation of hard HAZ Improve fusion Standards such as AS/NZS 1554.1 are used to determine the required preheat based on material group, heat input and combined joint thickness. But what is the basis for the minimum preheat temperature calculations in standards? Where did they come from? The short answer is Hydrogen Assisted Cold Cracking (HACC) prevention! The reality is t...