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Vol.43, No.11, 729 ~ 735, 2005
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| Title |
| Special Edition : Symposium on Mechanical Behavior of Materials(1) ; Corelation of Fatigue Properties with Defects in Electric Resistance Welded Seams |
| 홍현욱 H. U. Hong , 김충명 C. M. Kim , 이종봉 J. B. Lee , 김정규 J. K. Kim |
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| Abstract |
| A study on the correlation between fatigue properties and defects in electric resistance welded (ERW) seams was investigated. The ERW seams were produced by varying power input in the range of 230-270 kW and seam annealing temperatures of 850-970 in API 5L X70 line pipe steel. ERW defects were mainly in circular shape less than 10 ㎛ in length, while the elongated-shaped ones less than 30 ㎛ in length were occasionally observed in the case of low power input condition, with their occurrence of 1.2% less. They were mainly identified as Si, Mn, Al, (Ca)-rich oxides inclusions. Repeated loading was applied to notched three point bend specimens in order to investigate the susceptibility to pressure reversals of ERW seams. There was no occurrence of pressure reversals (sudden load drop) in all of the conditions investigated. Furthermore, the bond line ductility was found to be satisfactory. These results can be explained by the fact a bond line free from defects was successfully obtained from a wide range of ERW conditions, and also that the fusion zone was tough enough to inhibit initiation of microcracks. |
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| Key Words |
| APT 5L X70, Electric resistomce welding, Fatigue, Pressune reversal, Defect, Three point bending, Bond Line |
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