Analysis of underbead cracking in underwater wet weldments on A516 grade 70 steel.
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Authors
Manning, Ryan Daniel
Subjects
Underwater wet welding
Hydrogen cracking
underbead cracking
Non-metallic inclusions
Shielded Metal Arc Welding
Hydrogen cracking
underbead cracking
Non-metallic inclusions
Shielded Metal Arc Welding
Advisors
Fox, Alan G.
Date of Issue
1998-09
Date
Publisher
Monterey, California. Naval Postgraduate School
Language
en_US
Abstract
The use of underwater weldments on U.S. Naval Vessels is highly desirable due to the ability of performing repairs without costly dry dock expenses. The primary problem with underwater wet weldments is underbead cracking in the heat affected zone (HAZ). The fundamental factors causing underbead cracking in underwater wet weldments using a shielded metal arc welding (SMAW) process are high quench rates, slag inclusions, diffusible hydrogen levels and porosity. The weld metal analysis included use of optical and scanning microscopy as well as microhardness testing. Three weld samples made at 5 deg C, 12 deg C, and 25 deg C water temperature were analyzed in this thesis. HAZ underbead cracking was present in all three welds analyzed although the 5 deg C sample was the only weld that exhibited extensive cracking whereas the 25 deg C sample only had cracking near the upper 50% of the weld passes. Crack origination in all three samples near the cap was evident and was most likely due to small levels of bead tempering at this location. This thesis addresses the mechanisms of the cracking as well as the effects of diffusible hydrogen, cooling rates, and water temperatures on wet weldments
Type
Thesis
Description
Series/Report No
Department
Mechanical Engineering
Organization
Naval Postgraduate School
Identifiers
NPS Report Number
Sponsors
Funder
Format
x, 39 p.;28 cm.
Citation
Distribution Statement
Approved for public release; distribution is unlimited.
Rights
This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.