[논문]Microstructure and CTOD (crack tip opening displacement) of Deposit Weld Metal in 30 mm Thick Plate

Lee Hae-Woo; Kim Hyok-Ju; Park Jeong-Ung; Kang Chang-Yong; Sung Jang-Hyun

doi:10.3740/mrsk.2004.14.9.642

[국내논문] Microstructure and CTOD (crack tip opening displacement) of Deposit Weld Metal in 30 mm Thick Plate 원문보기

한국재료학회지 = Korean journal of materials research, v.14 no.9, 2004년, pp.642 - 648

Lee Hae-Woo (Welding research team, Samsung heavy industries) , Kim Hyok-Ju (Welding research team, Samsung heavy industries) , Park Jeong-Ung (Department of Civil engineering, Chosun university) , Kang Chang-Yong (Div. of Mat. Sci. and engineering, Pukyong national university) , Sung Jang-Hyun (Department of metallurgical engineering, Dong-A university)

Abstract ▼ AI-Helper

The microstructure and crack tip opening displacement (CTOD) of deposit weld metal were investigated for a 30 mm- thick plate welded with flux cored arc welding (FCAW) and submerged arc welding (SAW) processes. The CTOD test was carried out both as welded condition and as stress-relieved specimen by local compression. The crack growth rates in FCAW were faster than those in a SAW, and the acicular ferrite content by the SAW process was increased relatively more than that by the FCAW process. The fatigue crack growth rate in a welded specimen was faster than that in locally compressed specimen. The CTOD value of locally compressed specimens was lower than that of as welded specimen. Furthermore, the CTOD value tested with the SAW process was higher than that tested with the FCAW process.

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가설 설정

2) The acicular ferrite content welded with SAW process was transformed relatively more than that welded with the FCAW process.
3) The mean CTOD value of a locally compressed specimen was lower than that of a as- welded specimen.
4) The fatigue crack growth rate of the flux-cored arc welding was faster than that of the submerged arc welding.

제안 방법

The CTOD test was carried out on both as welded condition specimens and as stress- relieved specimens by local compression. Local compression is a technique whereby mechanical stress is relieved at the weldment by inserting a hardened steel platen into the local region in front of the machined notch before fatigue pre-cracking.
In this study, therefore, CTOD characteristics, hardness, and microstructure were studied according to FCAW and SAW processes.
The test was carried out on two kinds of samples: One was a sample under the as- welded condition, and the other was a stress-relieved sample obtained by local compression. Local compression is a technique whereby mechanical stress is relieved at the weldment using a hardened steel platen into the local region in front of the machined notch before the fatigue pre-cracking.
After completion of the test, the fracture surface was examined on the basis of BS 5762; the fatigue crack length was respectively measured for 25%, 50%, 75% of the thickness of the specimen; and the maximum-minimum length of crack was measured by using a 20x magnifier.

대상 데이터

The CTOD test specimens were made from as deposited weld metal along the welding line (NP specimen, BS7448 part ²⁾.
Test equipment was a ±25 ton capacity, uniaxial tension fatigue test machine. Testing was performed at the load control condition at a stress ratio = 0.

성능/효과

The test carried out at the condition in which the increasing rate of stress intensity factor during the initial elastic deformation was controlled within the range of 15 Nmm^-3/2 to 80 Nmm^-3/2seconds (Poisson's ratio of 0.3).
1) The mean CTOD value of the specimen welded with SAW process was hi^ier than that welded with FCAW process and was increased with the amount of acicular ferrite.

참고문헌 (15)

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