Proposal of a New G-BOP Test to Evaluate Cracks in Weld Beads in Thin Sheets
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TECHNICAL ARTICLE—PEER-REVIEWED
Proposal of a New G-BOP Test to Evaluate Cracks in Weld Beads in Thin Sheets Jose´ Hilton Ferreira da Silva Æ Hipolito Carvajal Fals Æ Roseana da Exaltac¸a˜o Trevisan
Submitted: 28 February 2008 / in revised form: 12 November 2008 / Published online: 9 December 2008 ASM International 2008
Abstract The objective of the present work is the evaluation of a proposal for a gapped bead-on-plate (G-BOP) test, used for study of hydrogen cracks in relatively thin sheets of welded steel. That new proposal consists of the replacement of the usual solid blocks by an assembly of blocks in such a way that the test can evaluate weld beads on thin sheets. Student t distribution is applied to examine the functionality of the proposed test. Weld metals were deposited with flux-cored wires E71T-1 and E71T8-K6, with diameters of 1.6 and 1.7 mm, respectively, under two different preheating temperatures. Metal susceptibility to hydrogen cracking was evaluated by the presence and percentage of cracks in the weld metal. In order to evaluate and verify the functionality of the new G-BOP test proposal, the following were examined: efficiency of the new test in inducing hydrogen cracks in the weld metal, result replicability, fracture modes present in cracks, and the cooling rate imposed on the welding zone. Results showed that the new G-BOP test proposal is viable; results were replicable and the test was efficient in inducing cracks in weld metal with a confidence of 90%. Keywords FCAW
Hydrogen cracking G-BOP Test
J. H. F. da Silva Federal Center of Technologic Education of the Bahia, Metallurgy Coordination, Simoes Filho, BA, Brazil e-mail: [email protected] H. C. Fals (&) R. da Exaltac¸a˜o Trevisan Department of Mechanical Engineering, State University of Campinas (UNICAMP), Sao Paulo, Brazil e-mail: [email protected] R. da Exaltac¸a˜o Trevisan e-mail: [email protected]
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Introduction One of the most serious faults in high-resistance, low-alloy steel welding is the occasional presence of undesirable hydrogen-induced cracks (HIC) [1, 2]. Although widely studied, hydrogen-induced cracks in welded joints continue to challenge users and researchers because of the numerous variables affecting the phenomenon and the lack of understanding of the consequent new materials, new welding processes, and new types of electrodes. After years of study, the formation of hydrogen cracks in the heataffected zones (HAZ) was nearly eliminated, but preventive practices applicable to the weld metal (WM) are not well established. As a consequence, research on the occurrence of hydrogen cracks in the weld metal has gained importance. The gapped bead-on-plate (G-BOP) test has great potential for evaluating susceptibility of molten zones to the HIC phenomenon. The G-BOP test has been chosen among the many weldability tests for its simplicity and reliability in quantifying susceptibility to hydrogen cracking. The test was developed in 1974 [3] and uses two steel blocks of 100 9 125 9 50 mm3 (3.94 9 4.92 9 1
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