• Title/Summary/Keyword: diffusible hydrogen

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A study on the fatigue fracture characteristics of TMCP high tensile strength steel welds (TMCP 고장력강 용접부의 피로파양 특성에 관한 연구)

  • 김영식;노재충;한명수;김윤해
    • Journal of Advanced Marine Engineering and Technology
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    • v.12 no.1
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    • pp.47-54
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    • 1988

  • TMCP steel manufactured by controlled rolling followed by accelerated cooling process is known to have extra-ordinary mechanical properties such as tensile strength and toughness. However, there is much uncertainty about the fatigue fracture characteristics of this steel. In this paper, the fatigue fracture behaviour of the TMCP steel in base metal and weldment were inspected through the Dynamic Implant test method. Those results were quantitavely compared with those of the ordinary normalized steel of same strength level. Moreover, the effect of the diffusible hydrogen included in the welded part on the fatigue fracture behaviour were made clear. As the experimental results, the fatigue fracture characteristics of the TMCP steel in case of base metal proved out to be superior to that of the normalized steel. However, the TMCP steel weldment including the diffusible hydrogen appeared to have inferior fatigue characteristics compared with the same conditioned normalized steel weldment.

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COLD CRACK SUSCEPTIBILITY OF HIGH STRENGTH WELD METAL

  • Kim, H. J.;B. Y. Kang
    • Proceedings of the KWS Conference
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    • 2002.10a
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    • pp.266-272
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    • 2002

  • This study reviews the factors controlling the weld metal cracking and shows the difference from those of HAZ cracking. It further reviews the recent progresses made in consumable design for improving the crack resistance in the high strength weld metal. Previously the controlling factors for weld metal cracking were regarded as weld metal strength, diffusible hydrogen and weld metal height. However an overall review presented in this article shows that the cold crack resistance can be improve significantly through the microstructural control and that an increase in tensile strength is not necessarily related to a decrease in the resistance to cold cracking.

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Effect of Moisture in Arc Welding Electrode on Mechanical Properties of Weld Metal (아아크 용접봉 피복제 의 함수량 이 용접금속 의 기계적 성질에 미치는 영향)

  • 윤희만;김연식;박종은
    • Journal of Welding and Joining
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    • v.2 no.1
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    • pp.30-40
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    • 1984

  • Moisture content in the coating of an electrode is known to cause defects such as porosities, fish eyes and cracks in the weld metal, however, quantitative relationship between them is not clearly understood. In this study widely consumed and the most common type of arc welding rods such as ilmenite and low hydrogen type were chosen for the investigation, and attempts were made to correlate the relationship between the mechanical properties and gas contents when welding was carried out with electrodes of various moisture contents. As the relative humidity changed from 70% to 92%, it was determined that moisture content to reach saturation was in the range of 0.6~6.8%. As the moisture content in the electrode coating was increased, the amount of gaseous components (H, O, N) in the weld metal was accordingly increased, especially diffusible hydrogen showed prominent effect, i.e. it increased proportionally to the increase of the moisture content. The mechanical properties of the weld metal was observed to become more inferior as the diffusible hydrogen was greater. It was determined for ilmenite type of electrode that the increase of hydrogen content was approximately 1.8ml per unit weight percent increase of moisture and also tensile strength resulted lowering from $45.3kg/\textrm{mm}^2$ to $42.7kg/\textrm{mm}^2$ as moisture content increased from 0.7% to 6.8%. For low hydrogen type the increase of the hyrogen was about 2.4ml per unit percent of moisture and tensile strength decreased from $63.0kg/\textrm{mm}^2$ to $53.8kg/\textrm{mm}^2$ particularly in the region of moisture content 0.1~4.2%.

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