Villy Inspection Share-4 _Key Points for Welding Inspection of Cr-Mo Steel - part 2
Villy Inspection Share-4 _Key Points for Welding Inspection of Cr-Mo Steel - part 2:
IV. Non-Destructive Testing (NDT)
11. Delay Before NDT for Cold Crack Susceptibility
Cr-Mo steel cold cracks have a delayed nature. Inspecting immediately after welding may miss defects. NDT should be performed at least 24 hours after welding. For thick-walled or high-strength steels (e.g., P91), a delay of 48-72 hours is recommended.
12. MT Mandatory After Grinding Surface Defects
After grinding defects like arc craters or undercut, perform MT to confirm complete removal. Visual inspection alone is insufficient.
13. Consider Repeating MT After PWHT
For highly restrained or critical welds, consider repeating MT after PWHT to detect any potential reheat cracks.
V. Documentation Verification
14. Review Original PWHT Charts
Request the original time-temperature recording chart. Verify that the heating rate, soaking period, and cooling rate comply with the WPS.
15. Verify Electrode Consumption Records
Spot-check the electrode issue records against the calculated consumption to ensure traceability and prevent the use of incorrect electrodes on-site.
16. Confirm Thermocouple Layout
During localized PWHT, review the thermocouple layout diagram to ensure proper placement and quantity for uniform temperature distribution in the heating zone.
Summary: The "Three-Step" Approach to Cr-Mo Steel Inspection
Stage, Core Inspection Actions:
- Pre-Weld
PMI for material grade, MT for bevels, verify preheat temperature, check electrode baking logs
- During welding
Monitor interpass temperature, zero tolerance for undercut, MT after tack/temp. Attachment removal
- Post-Weld
Verify slow cooling, NDT after ≥24h delay, hardness testing, review original PWHT charts
Cr-Mo steel welding inspection is a systematic process. Every step is crucial for the long-term service safety of the equipment. We hope this summary provides a useful reference for our peers in the industry. Feel free to add your thoughts and experiences in the comments!
