• Title/Summary/Keyword: Weld Metal HAZ

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Friction Welding of Sintered Hard Tool Materials to Metals and Its Quality Evaluation by AE (마찰용접에 의한 초경공구재와 금속간의 압접기술개발과 AE에 의한 품질평가)

  • 오세규;전태언;박일동;오명석;이주석
    • Journal of Ocean Engineering and Technology
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    • v.10 no.1
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    • pp.36-46
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    • 1996
  • This paper deals with determinig the proper friction welding condition and analyzing various mechanical properties of friction welded joints of sintered carbide tool materials(K20, P25, and SKDX5 for the blade part of drill or press punch) to alloy steel (SKH4, SCM440 for the shank part of drill or press punch), the alloy steel to aluminum(A6061 for the interlayer material between the blade part and the shank) and sintered carbide tool materials to alumminum. And also acoustic emission test will be carried out during fiction welding to evaluate the weld quality.

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The Effect of Heat Input on Grooving Corrosion Behavior in the Welds of Electric Resistance Welding Steel Pipe (ERW 강관 용접부의 홈부식거동에 미치는 입열량의 영향)

  • Lee, B.W.;Lee, J.S.;Park, H.S.
    • Journal of Power System Engineering
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    • v.11 no.3
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    • pp.41-46
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    • 2007
  • The microstructure and electrochemical analysis of welds of electric resistance welding(ERW) pipe were investigated. The direction of metal flow line in HAZ of ERW pipe shifted to the inner(or outer) surface of pipe by plastic deformation during welding. The lowest heat input welds of ERW pipe was showed crack by liquid penetrant testing. Accelerated corrosion test by constant current density of 20mA/$cm^{2}$ developed groove at the welds of ERW pipe and the measured grooving factors were about $1.2{\sim}1.5$. Corrosion potential of base metal obtained by cyclic polarization in artificial sea water(3.5wt.% NaCl solution) was 100mV higher than that of weld metal of ERW pipe.

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The effect of welding methods on the stress corrosion behavior of the welded austenitic stainless steel (오스테나이트 스테인리스강 용접부의 응력부식 거동에 미치는 용접 방법의 영향)

  • 백신영
    • Journal of Advanced Marine Engineering and Technology
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    • v.19 no.4
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    • pp.42-50
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    • 1995
  • To study the effect of welding methods on the Stress Corrosion Cracking (SCC) behavior of welded AISI type 316L and 304 austenitic stainless steel, the Slow Strain Rate Technique(SSRT) has been adopted in the boiling 45 wt% $MgCl_2$ solution. The results are as follows. 1) Welded sections are more susceptible than base metal in SCC, and the rank of SCC, and the rasistance in welding method is TIG, MIG, $CO_2$ and ARC. 2) The Ultimate tensile strength(UTS) and the strain of both base metal and welded joint are reduced as decreasing extension rate. 3) The SCC resistance of 316L base metal and welded sections are superior than that of 304. 4) The tendency of pitting and the SCC suseptibility are agreed well, and the SCC site is welded deposit section in 316L whereas HAZ in 304.

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A Development of Optimizing Tools for Friction Stir Welding with 2 mm Thick Aluminum Alloy using a Milling Machine (밀링을 이용한 AI합금의 마찰 교반용접용 최적공구형상 및 치수개발에 관한 연구)

  • 장석기;신상현
    • Journal of Advanced Marine Engineering and Technology
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    • v.25 no.4
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    • pp.791-796
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    • 2001
  • Friction stir welding is a solid phase welding process that does not melt the metal when welding. The FSW is the most remarkable and potentially useful new welding technique that is still in development. Friction stir butt welding process on 2 mm thick Al 1050 plates by utilizing a milling machine was experimentally studied. With the optimized heat generating tool welds could be achieved that are void and crack free. It was found that the friction stir welded tensile test specimens failed in the HAZ outside of the weld metal, and that the tensile strength was above 90% of that of the base metal.

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Effects of TiN and B on Grain Refinement of HAZ Microstructure and Improvement of Mechanical Properties of High-strength Structural Steel Under High Heat Input Welding (고강도 구조용 철강소재의 대입열 용접 시 열영향부의 조직 미세화 및 기계적 특성 향상에 미치는 TiN 및 B의 효과)

  • Park, Jin-seong;Hwang, Joong-Ki;Cho, Jae Young;Han, Il Wook;Lee, Man Jae;Kim, Sung Jin
    • Korean Journal of Materials Research
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    • v.29 no.2
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    • pp.97-105
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    • 2019
  • In the current steel structures of high-rise buildings, high heat input welding techniques are used to improve productivity in the construction industry. Under the high heat input welding, however, the microstructures of the weld metal (WM) and heat-affected zone (HAZ) coarsen, resulting in the deterioration of impact toughness. This study focuses mainly on the effects of fine TiN precipitates dispersed in steel plates and B addition in welding materials on grain refinement of the HAZ microstructure under submerged arc welding (SAW) with a high heat input of 200 kJ/cm. The study reveals that, different from that in conventional steel, the ${\gamma}$ grain coarsening is notably retarded in the coarse grain HAZ (CGHAZ) of a newly developed steel with TiN precipitates below 70 nm in size even under the high heat input welding, and the refinement of HAZ microstructure is confirmed to have improved impact toughness. Furthermore, energy dispersive spectroscopy (EDS) and secondary-ion mass spectrometry (SIMS) analyses demonstrate that B is was identified at the interface of TiN in CGHAZ. It is likely that B atoms in the WM are diffused to CGHAZ and are segregated at the outer part of undissolved TiN, which contributes partly to a further grain refinement, and consequently, improved mechanical properties are achieved.

Electrochemical Evaluation on Corrosion Property of Welding Zone of 22APU Stainless Steel (22APU 스테인리스강의 용접부위의 부식특성에 관한 전기화학적 평가)

  • Moon, Kyung-Man;Kim, Yun-Hae;Lee, Sung-Yul;Kim, Jong-Do;Lee, Myung-Hoon;Kim, Jin-Gyeong
    • Journal of Advanced Marine Engineering and Technology
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    • v.33 no.8
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    • pp.1162-1169
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    • 2009
  • Two kinds of welding methods were carried out for 22APU stainless steel, one is a Laser welding and the other is the TIG welding. In this case, difference of corrosion characteristics of welded zone with two welding methods mentioned above was investigated with electrochemical methods such as measurement of corrosion potential, polarization curves and cyclic voltammogram etc.. Vickers hardness of all welded zone (WM:Weld Metal, HAZ:Heat Affected Zone, BM:Base Metal)in the case of Laser welding showed a relatively higher value than those of TIG welding. Futhermore their corrosion current density in all welding zone were also observed with a lower value compared to TIG welding. In particular corrosion current density of BM regardless of welding method indicated the lowest value than those of other welding zone. Intergranular corrosion was not observed at the corroded surface of all welding zone in the case of Laser welding, however it was observed at WM and HAZ with TIG welding, which is suggested that chromiun depletion due to forming of chromium carbide appears to WM and HAZ which is in the range of sensitization temperature. Therefore their zone can easily be corroded with more active anode. Consequently we can see that corrosion resistance of all welding zone of 22APU stainless steel can apparently be improved by using of Laser welding.

Friction Welding and AE Characteristics of Magnesium Alloy for Lightweight Ocean Vehicle (해양차량 경량화용 마그네슘합금의 마찰용접 및 AE 특성)

  • Kong, Yu-Sik;Lee, Jin-Kyung;Kang, Dae-Min
    • Journal of Ocean Engineering and Technology
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    • v.25 no.6
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    • pp.91-96
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    • 2011
  • In this paper, friction welded joints were constructed to investigate the mechanical properties of welded 15-mm diameter solid bars of Mg alloy (AZ31B). The main friction welding parameters were selected to endure reliable quality welds on the basis of visual examination, tensile tests, impact energy test, Vickers hardness surveys of the bonds in the area and heat affected zone (HAZ), and macrostructure investigations. The study reached the following conclusions. The tensile strength of the friction welded materials (271 MPa) was increased to about 100% of the AZ31B base metal (274 MPa) under the condition of a heating time of 1 s. The metal loss increased lineally with an increase in the heating time. The following optimal friction welding conditions were determined: rotating speed (n) = 2000 rpm, heating pressure (HP) = 35 MPa, upsetting pressure (UP) = 70 MPa, heating time (HT) = 1 s, and upsetting time (UT) = 5 s, for a metal loss (Mo) of 10.2 mm. The hardness distribution of the base metal (BM) showed HV55. All of the BM parts showed levels of hardness that were approximately similar to friction welded materials. The weld interface of the friction welded parts was strongly mixed, which showed a well-combined structure of macro-particles without particle growth or any defects. In addition, an acoustic emission (AE) technique was applied to derive the optimum condition for friction welding the Mg alloy nondestructively. The AE count and energy parameters were useful for evaluating the relationship between the tensile strength and AE parameters based on the friction welding conditions.

A Study on the Stress Corrosion Cracking Evaluation for Weld Joint of Steel by Using Miniaturized Small Specimen (미소시험편에 의한 강 용접부의 응력부식 균열 평가에 관한 연구)

  • 유효선
    • Journal of Welding and Joining
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    • v.12 no.4
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    • pp.63-75
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    • 1994
  • The conventional SCC(stress corrosion cracking) test methods have much difficulty in evaluating the SCC behaviors of the localized zone like HAZ, bond line and weld metal because of the specimen size. Accordingly, the purpose of this paper is to develop the new SCC test method of the welded zone by evaluating the SCC susceptibility on parent metal and various microstructures of the welded zone by SP(small punch) test method using miniaturized small specimen and SSRT(slow strain rate test) method(SP-SSRT). Besides, this study is to verify the efficiency of the SP-SSRT results through AE(acoustic emission) test which is a useful technique to monitor the microfracture processes of the material. From the results of SCC susceptibility, SEM observation and AE test, it can be concluded that the SP-SSRT test using miniaturized small specimen(10mm*10mm*0.5mm) will be a good test method to evaluate the SCC susceptibility on the local zone such as the welded zone.

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Structures and Defects in Welds of High Strengths Al Alloys by Using GTAW (GTAW에 의한 Al 합금 용접부의 조직 및 결합에 대한 연구)

  • 하려선;정병호;박화순
    • Journal of Welding and Joining
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    • v.21 no.5
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    • pp.540-546
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    • 2003
  • Recently Al alloys are being used gradually for structural materials of transports. In welding of Al alloys used for transports, good weldabilities as well as adequate mechanical properties of the welds should be ensured as structural materials. In this study, the welds formation, macro and microstructural characteristics, generation of defects and hardness distribution in welds of Al alloys of 5083, 6N01 and 7N01 by DCSP- and AC-GTA welding process, were investigated. The deeper penetration was obtained in all welds of the alloys by DCSP-GTAW with He gas, compared with those by using AC-GTAW. The 6N01 alloy showed high susceptibilities to solidification cracking in weld metal and liquation cracking in HAZ of the welding beads of both DCSP- and AC-GTAW process. The cracking ratio of 6N01 alloy was increased with increasing of welding current. The porosity ratios in weld metal of all alloys used were extremely low including all welding conditions of DCSP-GTAW. However, in AC-GTAW process, the porosity ratios of the welds using Ar gas showed much higher values than those using He gas.

The dynamic fracture toughness of aluminum alloy weld zone by instrumented charpy test (計裝化 샬피 시험법 에 의한 알루미늄 합금 용접부 의 동적파괴 인성)

  • 문경철;강락원;이준희
    • Journal of Welding and Joining
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    • v.3 no.2
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    • pp.42-51
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    • 1985
  • The dynamic fracture toughness, fracture characteristics, impact tension and tensile properties of Al-Mg-Si T5 alloy and Al-Zn-Mg T6 alloy respectively welded with filler metal of Alcan 4043 were investigated. The dynamic fracture toughness values were obtained rapidly and simply for the specimen of small size by using instrumented Chirpy impact testing machine. the testing temperatures of the specimen were a range of room temperature and-196.deg. C. The results obtained in this experiment are summarized as follows. With decreasing the testing temperatures, dynamic tensile stress and fracture load were increased, on the other hand the deflection and impact value showed decreasing tendency in order of base metal>HAZ>weld. Changes of total absorbed energy were more influenced by the crack propagation energy than the crack initiation energy. At the low temperatures, the unstable rapid fracture representing the crack propagation appeared for the specimens of Charpy press side notched in Al-Zn-Mg alloy, but it was difficult to obtain the unstable rapid fracture in Al-Mg-Si alloy. Because of the development of plastic zone at the notch root, it was difficult to obtain thevalid $K_{1d}$ value in Al-Mg-Si alloy. Therefore the fatigue cracked specimens were effective in both Al-Mg-Si and Al-Zn-Mg alloys. With decreasing the impact testing temperatures, specimens underwent a transition from dimple-type transgranular fracture to lamella surface-type intergranular fracture because of the precipitate at the grain boundaries, impurities and crystal structure of the precipitates.s.

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