Table of Contents
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Introduction
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What Causes Hydrogen Cracking in Welding
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Best Practices to Prevent Hydrogen Cracking
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Material-Specific Considerations
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Inspection, Detection & Quality Control
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Case Studies & Real-World Learnings
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Conclusion
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Key Takeaways
Introduction
Hydrogen cracking in welding, also known as cold cracking or hydrogen-induced cracking, is one of the most critical and costly weld defects in industrial fabrication. Unlike hot cracking, which occurs during solidification, hydrogen cracking typically develops hours or even days after welding, often without visible warning signs.
This delayed failure mechanism can compromise structural integrity, increase rework costs, and pose serious safety risks, particularly in pressure vessels, pipelines, structural steel, and high-strength components.
Industries operating under quality standards such as EN ISO 5817 must take strict preventive measures to control hydrogen-related weld defects.
This guide explains what causes hydrogen cracking in steel, the difference between cold and hot cracking, and best practices to prevent it, from consumable selection to inspection.
What Is Hydrogen Cracking in Welding?
Hydrogen cracking is a weld defect that occurs when hydrogen atoms diffuse into the weld metal and heat-affected zone (HAZ), causing microcracks. It is often delayed, appearing after the weld has cooled, which makes early detection difficult.
Key Causes of Hydrogen Cracking
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Hydrogen Sources
Hydrogen enters the weld from several sources:
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Moisture in electrode coatings, fluxes, or shielding gases
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Damp or improperly stored welding consumables
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Surface contaminants like oil, grease, paint, or rust
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High environmental humidity during welding
Once in the weld, hydrogen diffuses into the HAZ and can remain trapped until it initiates cracks.
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Metallurgical Susceptibility
Certain steels are more prone to hydrogen embrittlement:
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Hard martensitic structures in the HAZ
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High carbon or alloyed steels (Cr, Mo, etc.)
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High carbon equivalent (CE) materials
Hard microstructures lower hydrogen tolerance and increase crack initiation risk.
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Residual Stresses & Cooldown
High stress and rapid cooling promote cracking:
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Rigid joint designs or excessive clamping
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Thick sections with uneven heat distribution
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Fast cooling rates that trap hydrogen
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Timing and Hydrogen Diffusion Window
Unlike other defects, hydrogen-induced cracking in welding is delayed:
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Occurs after weld solidification
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Develops as hydrogen migrates to stressed regions
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Requires careful preventive measures
Best Practices to Prevent Hydrogen Cracking
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Use Low-Hydrogen Consumables
Controlling hydrogen input is the most effective preventive measure:
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Use low-hydrogen electrodes and wires (H4 or H8 classification)
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Recommended consumables: Like E-7018 SUPRATHERME , E-8018-B2 CROMOTHERME-1 etc
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Store electrodes in dry, temperature-controlled ovens
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Re-dry electrodes per manufacturer guidelines
2. Surface Preparation & Cleanliness
Clean surfaces prevent hydrogen pickup:
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Remove oil, grease, paint, rust, and moisture
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Ensure joint edges are dry before welding
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Use degreasing and mechanical cleaning methods
3. Preheating & Interpass Temperature Control
Critical for crack-sensitive steels:
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Slows cooling, allowing hydrogen to escape
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Reduces HAZ hardness
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Preheat based on material, thickness, and carbon equivalent (EN 1011-2)
4. Heat Input Strategy
Balanced heat input prevents rapid cooling and excessive stress:
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Too low: Rapid cooling - higher hardness
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Too high: Residual stress - distortion
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Process selection matters: GTAW for precise control, SMAW/FCAW require strict parameter control
5. Post-Weld Heat Treatment (PWHT)
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Hydrogen bake-out to remove trapped hydrogen
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Stress relief to lower tensile stresses
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Tempering brittle microstructures
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Critical for thick sections and high-strength steels
6. Joint Design & Restraint Management
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Minimise excessive clamping
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Proper fit-up and alignment
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Welding sequences that balance shrinkage stresses
Material-Specific Considerations
|
Material Type |
Hydrogen Cracking Susceptibility |
Preventive Measures |
|
Carbon & Low-Alloy Steels |
Moderate to high (increases with higher carbon equivalent) |
- Preheating for thick sections - Post-Weld Heat Treatment (PWHT) - Controlled cooling to avoid martensitic HAZ formation |
|
High-Strength & Specialised Steels |
Very high (high sensitivity to hydrogen embrittlement) |
- Strict control of heat input - Proper preheat temperature - Use low hydrogen electrodes |
|
Stainless & Austenitic Alloys |
Lower overall cracking risk, but higher hydrogen solubility |
- Careful control in dissimilar metal welds - Controlled dilution - Correct filler and consumable selection |
Inspection, Detection & Quality Control
Because hydrogen cracking can be delayed, inspection is critical:
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Visual inspection for surface cracks
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Dye penetrant testing (DPT) for surface-breaking defects
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Magnetic particle inspection (MPI) for ferromagnetic steels
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Ultrasonic testing (UT) and radiography (RT) for subsurface cracks
Standards should align with EN ISO 5817 or project-specific requirements.
Case Studies & Real-World Learnings with D&H Solutions
Scenario 1: Pipeline Fabrication
Pipelines operating under high pressure are prone to hydrogen-induced cracking, which can lead to costly rework and delays. By using D&H Secheron low-hydrogen electrodes and following recommended preheating and interpass temperature practices, welds can achieve improved resistance to cold cracking, reducing the risk of delayed failures.
Scenario 2: High-Strength Pressure Vessel Maintenance
Maintenance of high-strength pressure vessels often faces microcracks due to residual stresses and hydrogen diffusion. Applying D&H guidance on controlled heat input, preheating, and post-weld heat treatment (PWHT) helps mitigate the risk of hydrogen embrittlement and ensures stronger, more durable welds.
Scenario 3: Industrial ROI through Preventive Measures
Industries adopting D&H low-hydrogen welding solutions and technical expertise can experience:
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Lower defect and repair rates
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Reduced downtime and associated costs
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Enhanced confidence in long-term weld reliability
Key Learning: Proactive use of D&H consumables and welding expertise makes the prevention of hydrogen cracking far more effective than reactive repairs, ensuring safer, more durable, and cost-efficient fabrication.
Conclusion
Preventing hydrogen cracking in welding is essential for achieving safe, durable, and high-quality welds in critical applications. By controlling hydrogen input, managing heat effectively, and selecting appropriate low-hydrogen consumables, fabricators can significantly reduce the risk of cold cracking and hydrogen embrittlement.
At D&H Sécheron, we support industries with advanced low-hydrogen welding solutions and application expertise. Explore our LoTherme consumable range or connect with our technical specialists to ensure reliable, crack-resistant weld performance.
Key Takeaways
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Hydrogen cracking is a delayed, high-risk weld defect
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It results from hydrogen presence, hard microstructures, stress, and rapid cooling
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Low-hydrogen consumables and proper storage are critical
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Preheating and controlled heat input significantly reduce risk
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PWHT and inspection help prevent delayed failures
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Prevention costs far less than repair and rework
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