Proper PWHT can stop stress-induced corrosion

Journal Article · Thu May 01 04:00:00 EDT 1997 · Welding Journal

OSTI ID:500905

Bloch, C; Hill, J ^[1]; Connell, D ^[2]

---

1. Serv-Tech, Inc., Houston, TX (United States). Hill Technical Heat Treatment Div.
2. Detroit Edison, MI (United States)

Postweld heat treatment of welded joints to improve the ductility of welds susceptible to cracking due to metal composition or wall thickness has become an essential component of standards generated by professional organizations. When properly applied, these procedures have proven to be quite effective in preventing premature weld-related failures. Recently, the welding industry has recognized that weld-induced stress also plays a role in certain localized corrosion phenomena. To address the cause of these long-term corrosion failures, it has become common practice to specify postweld heat treatment for thin-walled piping and vessels that would otherwise be exempt from code procedures. Corrosion often continues to be a problem even after post-weld heat treatment (PWHT) is performed on these relatively thin-walled weldments. The results of the extensive tests performed for the preparation of this paper indicate that surprisingly large through-wall radial temperature gradients often exist during the application of common PWHT practices. As a result of these radial temperature gradients, the standard application of heating elements to the pipe exterior does not always provide assurance that the interior surfaces at the edge of the heat-affected zone (HAZ) will achieve the temperatures necessary to adequately reduce weld-induced hardness. It is on these interior surfaces that the stress-induced corrosion phenomena is initiated.

• OSTI ID: 500905
• Journal Information: Welding Journal, Journal Name: Welding Journal Journal Issue: 5 Vol. 76; ISSN 0043-2296; ISSN WEJUA3
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
HEAT AFFECTED ZONE
HEAT TREATMENTS
PIPES
STEEL-ASTM-A533-B
STRESS CORROSION
TEMPERATURE GRADIENTS
WELDED JOINTS