Hydrogen Control Calculator
Determine hydrogen control requirements to prevent cracking.
AWS Hydrogen Designators
| Designator | Max H2 (ml/100g) | Application |
|---|---|---|
| H2 | 2 | Very critical, P91 |
| H4 | 4 | Most critical steels |
| H8 | 8 | High strength steel |
| H16 | 16 | Standard low-H |
Understanding Hydrogen-Induced Cracking
Three Conditions for HIC
- Hydrogen: Diffusible hydrogen in weld metal (from moisture, contamination)
- Susceptible Microstructure: Hard HAZ (martensite), high carbon equivalent
- Stress: Residual stress from restraint and cooling
Sources of Hydrogen
- Electrode Coatings: Absorb moisture from atmosphere
- Flux: SAW and FCAW flux can contain moisture
- Base Metal: Mill scale, rust, contamination
- Shielding Gas: Moisture in gas or hoses
- Environment: High humidity, rain, condensation
Electrode Storage Requirements (AWS A5.1)
- Baking: 260-430C (500-800F) for 1-2 hours for reconditioning
- Holding Oven: 120-175C (250-350F) during use
- Exposure Limit: 4 hours max out of oven (varies by electrode)
- Rebake Limit: Maximum of 3 rebakes typically allowed