Analysis of underbead cracking in underwater wet weldments on A516 grade 70 steel
By: Ryan Daniel Manning
Publisher: Naval Postgraduate School; Available from National Technical Information Service
Published: 1998
Place of publication: Monterey, Calif; Springfield, Va
Language: eng
Number of pages: 39
Description: 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.
Notes: "September 1998."

Thesis advisor(s): Alan G. Fox.

Thesis (M.S. in Mechanical Engineering) Naval Postgraduate School, September 1998.

Includes bibliographical references (p. 37)

Approved for public release; distribution unlimited.

Also available online.

Mode of access: World Wide Web.

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US Coast Guard (USCG) author.

dk/dk cc:9116 12/3/98.