SA 387 Grade 22 Cl.2 - Welding Crack

[williams p wilson]

Hai Experts,

Greetings!!

Hope you are doing well.

We found crack on Turbine Exhaust Stack butt weld joints made by 6 mm thick, SA 387 Grade 22 Cl.2 

We repaired with E91T1-B3 with FCAW welding process  with a preheat of 140 degree C , maximum Interpass temp. of 240 degree C.

But again welding crack observed while doing the MPI, request to please share your comments to solve this matter.

Thank You & Regards

Williams P Wilson

+968-94600828

QA/QC Engineer

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[abdullah Alhiji]

Dear, 

From the look of the crack it seems this is a hot crack. The reason of this is likely due to not being able to manage the welding parameters. take care of the following: 

• Lower the heat input: Adjust welding parameters to reduce heat input, especially given the thin material (6 mm).
• Ensure uniform weld bead geometry: Aim for a balanced, wider bead to minimize centerline solidification cracking.
• Verify material cleanliness: Ensure the base metal and filler wire are free from impurities.
• Monitor preheat and interpass temperatures: Keep the heat input consistent across the entire weld to avoid uneven cooling.
• Refine welding technique: Control weld speed, clean between passes, and ensure proper FCAW process controls as per the WPS. 

keep us updated after following the above please. 

Thanks, 

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[Alireza Aghaei]

Hi Dear

You should do DHT operation immediately after finishing the welding process

post heating is to minimize the susceptibility to cold cracking due to residual hydrogen in the welds and to minimize problems due to low as-welded toughness. Because of hydrogen pick up during the welding process, a dehydrogenation heat treatment is applied to the weld to outgas the hydrogen before a weld allowed to cool.

DHT will be started at 300 C within a minimum 200 mm band with weld in the center line promptly at the first strike of arc and will be finished minimum 2 hours after taking the strike off the base metal.

Thanks,

[sridhar cn]

Welding SA 387 Grade 22 Cl.2, a high-strength alloy steel, can lead to issues like cracking if not handled properly. During the welding process:

o  Preparation: Preheating to 150⁰ C or as per specific guidelines or standards is essential to reduce the cooling rate of the weld and minimize 

    the risk of cracking.

o  Welding Procedure: Control the heat input with proper welding parameters Ampere, voltage, and travel speed) to avoid residual stresses.

o  Use Interpass Temperature Controls: Monitor the Interpass temperature to 250⁰ C to prevent overheating of the weld area.

o  Welding Technique: Instead of weaving, use stringer beads to reduce heat input and distortion.

o  Post-Welding Treatment: Post-heat weld and HAZ areas to 300-350 ⁰ C to release residual Hydrogen.

o  Post-Weld Heat Treatment: PWHT to 700°C to 760°C (but specific requirements may vary) to relieve residual stresses that may have been 

    introduced during welding.

o  Slow Cooling: Allow the welded assembly to cool slowly by 50 to 75⁰C (up to 325⁰C and air cool to room temperature to minimize the risk of 

    cracking.

o  Welding Environment: Avoid welding in windy (do not use fans) to evade faster cooling during welding and lead to cracking.

o  Training and Skill Development: Ensure Proper Training for Welders: Using skilled welders (under proper supervision & Inspection) familiar 

    with the specific requirements for welding LAHT steels can significantly reduce the risk of defects.

o  Filler wire: E 91T5-B3, a basic type of FCAW filler wire, designed to weld LAHT steels can be used in place of E 91 T1-B3 filler wire which is a 

    rutile version and may have moisture content.                                                                                                                                          

    But, why use a FCAW process for a 6 mm thick? You can also weld with an ER91-B3 (Hyundai, Kobe or equivalent brand) which may have less than 

    3 ppm hydrogen and help to avoid weld cracks. If it is a small job, you can use a GTAW / SMAW process too.

o  Repair welding: Follow the above procedure including a DP / MT test(s) after removing all the cracks through grinding and before repair welding. 

Hope the above inputs may help to avoid cracks while welding SA 387 Grade 22 Cl.2 material.

C Sridhar.

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[senthil vel]

Fcaw should be avoid ,and Follow the Post heat after welding ,  Fcaw not suitable for this Material and thickness range

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