The document provides explicit metallurgical, welding, and manufacturing requirements to ensure that the heat-affected zones (HAZ) and weld metals do not exceed specific hardness thresholds. High hardness correlates directly with increased susceptibility to brittle failure in sour services. Key Core Requirements of NACE RP0472
NACE RP0472 addresses two main types of environmental cracking:
This standard is the "go-to" guide for protecting carbon steel—specifically —from cracking when exposed to harsh chemicals like wet hydrogen sulfide ( H2Scap H sub 2 cap S ). Without these controls, welds are highly susceptible to: nace rp0472 pdf
Revisions frequently update testing frequencies and chemical composition limits based on recent field failures.
During PQR, cross-sectional Vickers (HV5 or HV10) or Rockwell testing is performed. Surveys must map the weld metal, the fusion line, and multiple points across the HAZ to find the peak hardness value. NACE MR0103 vs. NACE RP0472 vs. NACE MR0175 Without these controls, welds are highly susceptible to:
NACE RP0472 defines weldments to include the weld deposit, base metal heat-affected zones (HAZs), and adjacent base metal zones that are subject to residual stresses from welding. This comprehensive definition ensures all potentially vulnerable areas of a welded joint are addressed.
It tempers hard microstructures (like martensite), lowering overall hardness. NACE MR0103 vs
: RP0472 mandates that welding procedures must be tested specifically for hardness before they are ever used in the field. This ensures the "recipe" for the weld is inherently safe. 4. Integration with Global Standards
is a standard published by NACE International, now part of the Association for Materials Protection and Performance (AMPP). It is titled "Methods and Controls to Prevent In-Service Environmental Cracking of Carbon Steel Weldments in Corrosive Petroleum Refining Environments."
Title: 🛡️ NACE SP0472: Preventing Weld Cracking in Sour Service Environments