• Title/Summary/Keyword: Weld Metal HAZ

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A Fracture Mechanics Study on the Fatigue Crack Growth Behaviors in Aluminum Alloy Weldments (알루미늄 합금 용접부의 피로균열성장거동에 관한 파괴력학적 연구)

  • 차용훈
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.5 no.3
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    • pp.31-39
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    • 1996
  • The objective of this study is to investigate the influence of welding residual stresses on the fatigue crack growth behavior of cracks located transverse to the weld bead. For this purpose, G. T. A (Gas Tungsten Arc) welding was performed on hte Al alloy 1100-O plate and the same initial crack is made on HAZ(Heat Affected Zone), weld metal and base meta respectively. Specimens were used CT(Compact Tension) specimens. Initial welding residual stresses were measured by using strai gage sectioning method. All specimens were tested under constant amplitude load with stress ratio R=0.1, It is possible to predict fatigue crack growth behaviors and the fatigue life, using numerical analysis together with distribution of initial residual stress and the values of C and m obtained from $da/dN-{\Delta}K$

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A Study on Corrosion Fatigue Properties of Welded Joints for TMCP High Strength Steels (TMCP 고장력강 용접부의 부식도영 특성에 관한 연구)

  • 이택순;이휘원;김영철
    • Journal of Ocean Engineering and Technology
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    • v.10 no.3
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    • pp.14-23
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    • 1996
  • The corrosion fatigue test were carried out to evaluate the fatigue characteristics of accelerated cooled (ACC) TMCP high tensile strength steels and weld joint with high heat input by one side one run submerged are welding. In this paper, the fatigue crack growth behaviors were investigated with the center crack tension specimen of base metal and heat affected zone in substitute sea water and air, respectively Main results obtained are sunnarized as follows: 1. The fatigue crack growth rates in sea water faster than those in air environment for the different heat input values, crack growth rate of base metal is very fast and effect of heat input is not remarkable. 2. In HAZ (82kJ/cm, 116kJ/cm), the crack branching phenomena were observed in both air and sea water environment, 3. In SEM observation, the corrosion effect on base metal was larger than that on HAZ in corrosion environment.

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Marco and Microscopic Observations of Fatigue Crack Growth in Friction Stir Welded 7075-T651 Aluminum Alloy Plates (마찰교반용접된 7075-T651 알루미늄 판재의 피로균열전파의 거시적 및 미시적 관찰)

  • Kong, Yu-Sik;Kim, Seon-Jin
    • Journal of Power System Engineering
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    • v.18 no.2
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    • pp.62-69
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    • 2014
  • In this paper, in order to investigate the effects of marco and microscopic observations of fatigue crack growth in friction stir welded (FSWed) 7075-T651 aluminum alloy plates, fatigue crack growth tests were performed under constant amplitude loading condition at room temperature with three different pre-cack locations, namely base metal (BM-CL) and two kinds of pre-crack locations in welded joints, weld metal (WM-CL) and heat affected zone (HAZ-CL) specimens. The fatigue crack growth behavior of FSWed 7075-T651 aluminum alloy plates were discussed based on the marco and microscopic fractographic observations. The marcoscopic aspects of surface crack growth path for BM-CL and HAZ-CL specimens indicate relatively straight lines, however, the crack growth paths of WM-CL specimens grow first straight and by followed toward the TMAZ and HAZ. The microscopic aspects of fatigue fracture for BM-CL and HAZ-CL specimens indicate typical fatigue striation, but WM-CL showed intergranular fracture pattern by micro structural changes of FSW process.

Fatigue Crack Propagation Behavior of 316L Stainless Steel and Frequency Characteristics of its Acoustic Emission (316L 스테인리스강의 피로균열 진전 거동과 음향방출신호의 주파수 특성)

  • Lee, S.K.;Do, J.Y.;Nam, K.W.;Kang, C.Y.;Ahn, S.H.
    • Journal of Power System Engineering
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    • v.4 no.2
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    • pp.52-57
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    • 2000
  • We investigated the fatigue crack propagation of base metal, weld metal and heat attected zone in 316L stainless steel. And we analysed acoustic emission signals during the fatigue test by time-frequency analysis method. The specimens of weld metal and HAZ had longer fatigue life and slower rate of crack propagation better than base metal. And as a result of time-frequency was 200-300 kHz was obtained by fatigue crack propagation and 500 kHz was obtained by dimple and separate of inclusion.

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The Effect of Weld Metal Copper Content on HAZ Cracking in Austenitic Stainless Steel welded with Al-brass

  • Lee, H.W.;Lee, J.S.;Choe, W.H.
    • Proceedings of the KWS Conference
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    • 2005.06a
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    • pp.152-154
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    • 2005
  • Austenitic stainless steel has good weldability but is sensitive to hot cracking such as solidification crack and liquation crack. In this study, the specimens of dissimilar metals made between austenitic stainless steel and Al-brass were welded by GTAW process using four different filler metals. Cracks were detected in the heat-affected zone of the stainless steel when welded with CuAl, CuSn and NiCu filler metals, but no cracks were detected a Ni filler metal was used. The cracks propagated along the grain boundary in the heat affected zone near the fusion line to base metal of 316L stainless steel. The cracks were located inside the weld bead with very fine hairline crack. All cracks initiated at the fusion line and moved forward in the base metal. From energy dispersion spectroscopy (EDS), Cu peak was detected only in the crack-opening area.

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A Characteristic of microstructural evolution, microhardness and tensile properties in CrMoV rotor steel weldment experienced by the cyclic thermal aging heat treatment (CrMoV강 용접부의 주기적 열시효처리에 따른 미세조직, 미세경도 및 인장강도 특성)

  • Kim, G.S.;Koh, J.H.
    • Journal of the Korean Society for Heat Treatment
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    • v.12 no.4
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    • pp.303-312
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    • 1999
  • An investigation of the CrMoV rotor steel weldment which experienced by cyclic thermal aging heat treatment and as-received condition was performed. This evaluation was carried out to confirm whether this type of weldment is appropriate for the service environment in terms of microstructural examinations, microhardness measurements and tensile tests. The cyclic thermal aging heat treatment, containing continuous heating and cooling thermal cycle was programmed to simulate the real rotor service condition. The heat treatment was performed for 40 cycles(5920hrs). The results indicated that the weldment was composed of 4 different regions such as heat affected zone of the base metal, butter weld(initial weld), full thickness weld(final weld) and the base metal. The double welding process was applied to eliminate the susceptibility of reheat cracking at heat affected zone of base metal. The grain refinement at the HAZ due to the welding process could reduce the possibility of cracking susceptibility, but its tensile properties was appeared to be low due to the weld metal in as-received condition. The benefit effect, grain refinement was extended with carbides coarsening during the cyclic thermal aging heat treatment. However the poor mechanical properties of the weldment was more degraded as undergoing the heat treatment.

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Electrochemical Evaluation of Corrosion Property of Welding Zone of 304 Stainless Steel (304 스테인리스강의 용접부위의 부식특성에 관한 전기화학적 평가)

  • Moon, Kyung-Man;Kim, Yun-Hae;Kim, Jong-Do;Lee, Myung-Hoon;Kim, Jin-Gyeong
    • Journal of Ocean Engineering and Technology
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    • v.23 no.4
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    • pp.58-63
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    • 2009
  • Two kinds of welding methods are used for austenitic 304 stainless steel: laser welding and TIG welding. The difference in the corrosion characteristics of the welded zone between these two welding methods was investigated using electrochemical methods, such as corrosion potential measurements, polarization curves, cyclic voltammograms, etc. The Vickers hardnesses of all the welded zones (WM: Weld Metal, HAZ: Heat Affected Zone, BM: Base Metal) showed relatively higher values in the case of laser welding than for TIG welding. Furthermore, the corrosion current densities of all the welding zones showed lower values compared to TIG welding. In particular, the corrosion current density of the HAZ with TIG welding had the highest value of all the welding zones, which suggests that chromium depletion due to the formation of chromium carbide appears in the HAZ, which is in the range of the sensitization temperature. Thus, it can easily be corroded with a more active anode. Consequently, we found that the corrosion resistance of all of the welding zones for austenitic 304 stainless steel could apparently be improved by using Laser welding.

Estimation for the Distribution of Creep Crack Growth Coefficients by Probabilistic Assessment (확률적 방법에 의한 크리프 균열성장 계수의 분포 추정)

  • Lee, Sang-Ho;Yoon, Kee-Bong;Choe, Byung-Hak;Min, Doo-Sik;Ahn, Jong Seok;Lee, Gil Jae;Kim, Sun-Hwa
    • Korean Journal of Metals and Materials
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    • v.48 no.9
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    • pp.791-797
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    • 2010
  • The creep crack growth rate (da/dt) of the Cr-Mo steels tested by pre-crack and the voltage (or resistance) variables were related into fracture parameter (Ct), crack growth coefficient (H), and an exponent (q) in the parts of Base, weld and HAZ. The fracture parameter (Ct) has various variables relating to the specimen and crack shape, applied stress, and creep strain curve. The H and q was inferred by OLS regression (ordinary least square method), and the H values were solved in statistics and probability assessment, which were attained fromPDF's distributions (probability density function). The HAZ part has the highest value of q by OLS regression and the widest distribution of H by PDF of WEIBULL, which means that the crack sensitivity of HAZ should be cautioned against the creep crack growth and failure.

Experimental Studies on Joinability of SWS 490A High Tension Steel using Acoustic Emission Signals (음향방출 신호를 이용한 SWS 490A 고장력강의 접합성 평가에 대한 실험적 연구)

  • Rhee Zhang-Kyu;Woo Chang-Ki
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.14 no.3
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    • pp.87-95
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    • 2005
  • The object of this study is to investigate the effect of joinability by using acoustic emission(AE) signals and doing a pattern recognition for weld heat affected zone(HAZ) in tensile testing. This study was carried out an SWS 490A high tension steel for electric shielded metal arc welding(SMAW), $CO_2$ gas arc welding and TIG welding. And correspondingly, the root openings are 3, 4 and 2.8mm. The results of the tensile test of weld HAZ come out electric shield arc welding $>\;CO_2$ gas arc welding > TIG welding in case of single welding. It is believed that this is a phenomenon where difference of its root opening or base metal thickness. Also, the technique of AE is ideally suited to study variables which control time and stress dependent fracture or damage process in metallic materials.

Experimental Studies on Joinability of SWS 490A High Tension Steel using Acoustic Emission Signals (음향방출 신호를 이용한 SWS 490A 고장력강의 접합성 평가에 대한 실험적 연구)

  • 이장규;우창기;윤종희;조진호;조대희;박성완;김봉각;구영덕
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • 2004.10a
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    • pp.40-48
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    • 2004
  • The object of this study is to investigate the effect of joinability by using acoustic emission (AE) signals and doing a pattern recognition for weld heat affected zone (HAZ) in tensile testing. This study was carried out an SWS 490A high tension steel for electric shielded metal arc welding (SMAW), $CO_2$ gas arc welding and TIG welding. And correspondingly, the root openings are 3, 4 and 2.8mm. The results of the tensile test of weld HAZ come out electric shield arc welding > $CO_2$ gas arc welding > TIG welding in case of single welding. It is believed that this is a phenomenon where difference of its root opening or base metal thickness. Also, the technique of AE is ideally suited to study variables which control time and stress dependent fracture or damage process in metallic materials.

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