It details the soaking temperatures and hold times required to successfully temper the steel and achieve compliant hardness levels. 3. Production Hardness Testing
If the steel microstructure is excessively hard (and therefore brittle) and under tensile stress (such as residual welding stresses), the hydrogen triggers catastrophic, brittle cracking.
API previously published a document, API RP 942, with similar objectives to NACE RP0472. The API document has been discontinued, and NACE RP0472 is now recognized as the industry consensus standard. nace rp0472 pdf
These third-party providers often manage enterprise licenses for engineering firms needing SP0472 access . Typical Applications
When welding parameters alone cannot reduce hardness below 200 HBW, Post-Weld Heat Treatment is required. PWHT involves heating the completed weldment to a critical temperature (typically around 600°C to 650°C or 1100°F to 1200°F) and holding it for a specified duration. This process: It details the soaking temperatures and hold times
To achieve the mandated hardness levels and reduce residual stresses from welding, Post-Weld Heat Treatment (PWHT) is often required. PWHT involves heating the completed weldment to a specific temperature (typically between 595°C to 650°C or 1100°F to 1200°F) and holding it for a specified duration. This thermal process: Tempers hard microstructures (like martensite). Lowers overall hardness.
The standard documents several methods that can be used to ensure carbon steel weldments will be soft enough to resist cracking. These include: API previously published a document, API RP 942,
NACE RP0472, redesignated as NACE SP0472 and currently in its 2020 version, establishes essential guidelines for controlling carbon steel weldment hardness to prevent environmental cracking in petroleum refining environments. The standard dictates specific practices, such as a 200 Brinell hardness limit, to prevent cracking mechanisms like sulfide stress cracking and alkaline stress corrosion cracking. Purchase the official standard at the AMPP Store .
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(sour) environments, atomic hydrogen is generated by the corrosion reaction on the steel surface. Instead of forming harmless hydrogen gas ( H2cap H sub 2 ), the presence of sulfides allows atomic hydrogen (
The standard focuses on two primary types of environmental cracking:
