Evaluation of Hydrogen Cracking in Weld Metal Deposited using Cellulosic Electrodes

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• Gas Pipeline
• Hydrogen
• Leak Detection
• Weld/Fabrication Defects

Main Objective

The objectives of the proposed project can be summarized as follows:

• To determine the effect of electrode drying and arc length on weld metal chemistry, mechanical properties and hydrogen cracking susceptibility.
• To determine the effect of electrode re-hydration on weld metal chemistry, mechanical properties and hydrogen cracking susceptibility.
• To develop practical guidelines on how to prevent hydrogen cracking in welds deposited using cellulosic covered electrodes.

Public Abstract

Background: Cellulosic-coated electrodes (primarily AWS EXX10-type) are traditionally used for "stovepipe" welding of pipelines because they are well suited for deposition of pipeline girth welds and are capable of high deposition rates when welding downhill. Extensive work was undertaken in the 1970s and 1980s to study heat affected zone (HAZ) hydrogen-assisted cracking, and guidelines were developed to avoid HAZ hydrogen cracking by controlling heat input and preheat. Improvements in steel making practice and the trend towards leaner chemistries have also helped to alleviate HAZ hydrogen cracking. In recent years, weld metal hydrogen cracking has become more of an issue with the trend towards higher-strength steels and welding with minimal or no preheat.

Objectives:
1) Determine the effect of electrode drying and arc length on weld metal properties
and hydrogen cracking susceptibility
2) Determine the effect of electrode re-hydration on weld
metal properties and susceptibility
3) Develop practical guidelines on how to prevent

hydrogen cracking in weld metal deposits using cellulosic covered electrodes.

Technical Approach: The proposed project aims to further define the conditions that can lead to hydrogen cracking in weld metal deposited using cellulosic-coated electrodes, in terms of operator preference (arc length), electrode properties, power supply selection, and materials handling, and to develop welding guidelines, and if applicable, re-hydration guidelines to prevent weld metal hydrogen cracking. A work scope similar to that used for PR-185-9909 is proposed. The work will be carried out in three phases: Phase 1 will focus primarily on consumable selection and a preliminary evaluation of the effects of electrode drying, Phase 2 will focus

primarily on a preliminary evaluation of the effects of electrode re-hydration, and Phase 3 will focus primarily on detailed evaluation of procedure variables and development of guidelines.

Project Team: Edison Welding Institute, Inc. (EWI) and PRCI

Sponsoring Organizations: U.S. Department of Transportation (DOT) Pipeline and Hazardous Materials Safety Administration (PHMSA) and Pipeline Research Council International, Inc. (PRCI)