• 제목/요약/키워드: high Heat Input Welding

검색결과 187건 처리시간 0.021초

용접구조용 고장력강의 용접부 인성에 미치는 미세 조직과 용접 입열량의 영향 (Effects of microstructure and welding heat input on the toughness of weldable high strength steel weldments)

  • 장웅성;방국수;엄기원
    • Journal of Welding and Joining
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    • 제7권3호
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    • pp.44-54
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    • 1989
  • This study was undertaken to evaluate the allowable welding heat input range for high strength steels manufactured by various processes and to compare the weldability of TMCP steel for high heat input welding with that of conventional Ti-added normalized steel. The allowable welding heat input ranges for conventional 50kg/$mm^2$ steel to guarantee D or E grade of ship structural steel were below 150 and 80kJ/cm respectively. Such a limit in welding heat input was closely related with the formation of undesirable microstructures, such as grain boundary ferrite and ferrite side plate in the coarse grain HAZ. In case of 60 and 80kg/$mm^2$ quenched and tempered steels, for securing toughness in weldments over toughness requirements for base metal, each welding heat input had to be restricted below 60 and 40kJ/cm, that was mainly due to coarsened polygonal ferrite in weld metal and lower temperature transformation products in coarse grain HAZ. The TMCP steel could be appropriate as a grade E ship hull steel up to 200kJ/cm, but the Ti-added normalized steel could be applied only below 130kJ/cm under the same rule. This difference was partly owing to whether uniform and fine intragranular ferrite microstructure was well developed in HAZ or not.

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세립강 저입열 용접부의 기계적 성질 (Mechanical properties of fine grained steel weldments formed with low heat input)

  • 윤중근;박태동;김광수;박영수
    • 대한용접접합학회:학술대회논문집
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    • 대한용접접합학회 2003년도 추계학술발표대회 개요집
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    • pp.227-229
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    • 2003
  • Low heat input welding methods have been investigated in order to minimize the HAZ softening of the 600MPa grade fine grained steel weldment. The welding processes of interest were a high speed FCA welding with a multi-torch welding system, laser welding with filler feeding and hybrid laser welding. No HAZ softening was found for all the weldments formed with low heat input less than 10kJ/cm. Tensile strength of the weldments was high enough to satisfy the required value. Impact toughness of the weldments was also good even at -20$^{\circ}C$.

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Al6082-T6의 MIG용접부에서 입열량에 따른 열영향부의 연화와 인장특성에 관한 연구 (A Study on Tensile Properties and HAZ Softening Depending on the Amount of Heat Input in MIG Welding of Al6082-T6)

  • 백상엽;박경도;김원일;조상명
    • Journal of Welding and Joining
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    • 제29권1호
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    • pp.59-64
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    • 2011
  • Al6082-T6 is widely used because of its corrosion resistance and excellent strength. HAZ softening occurs in MIG welding process for this aluminium alloys because this aluminium alloy is heated to higher temperature than its aging temperature during welding. Therefore, low heat input and minimum standard deviation of heat input are required for narrow HAZ width and, for higher strength of welds. In this study, Al6082-T6 was used to examine for HAZ softening with various heat input in aluminium MIG welding. For weldments, micro hardness was measured and tensile test was carried out. Minimum hardness was increased at high speed welding such as 80cm/min and 120cm/min in welding speed comparing with 40cm/min. Also, in case of high speed welding such as 80cm/min and 120cm/min, tensile strength of weldments was increased about 10% comparing with low speed welding(40cm/min).

大入熱 高張力鋼 熔接部 의 機械的 特性 變化 에 關한 硏究 (A study on the Mechanical Properties in High Heat Input Welds of High Strength Steels)

  • 김영식;배차헌
    • Journal of Welding and Joining
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    • 제1권1호
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    • pp.47-55
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    • 1983
  • The mechanical and microstructural properties in high heat input welds of home-made SM 50 high strength steels were investigated and compared with the manual shielded metal arc welds. Also, the fracture toughnesses of the simulated weld-bonds with various thermal cycles were quantatively examined in order to provide the basic data for further development of the high strength steels for high input welding. Main results obtained are as follows. (1) The embrittlement degree and the coarse grained region in high heat input welds appear to be extraordinarily large compared with the manual shielded metal arc welds, while the difference in change of nicrohardness is not so large in both welds. (2) The embrittleness in high heat input weld-bonds is mainly affected by the size of coarse grain rather than the microstructure. (3) The fracture toughness in high heat input weld-bonds can be improved by controlling the cooling rate from 800.deg.C to 500.deg.C rapidly.

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고강도 구조용 철강소재의 대입열 용접 시 열영향부의 조직 미세화 및 기계적 특성 향상에 미치는 TiN 및 B의 효과 (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)

  • 박진성;황중기;조재영;한일욱;이만재;김성진
    • 한국재료학회지
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    • 제29권2호
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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.

탄소강관의 ERW 용접부 홈부식 손상에 관한 연구 (A Study on Grooving Corrosion at the Weld of a Low Carbon Steel Pipe Made by Electrical Resistance Welding)

  • 김용;이보영
    • Journal of Welding and Joining
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    • 제22권5호
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    • pp.58-64
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    • 2004
  • Although leakage at a low carbon steel pipe made by electrical resistance welding (ERW) was reported due to grooving corrosion, the cause for the corrosion has not yet been cleared. In order to clarify the main cause, failure analysis on the leaked pipe was carried out, followed by metallographic investigation and corrosion test for the various ERW pipe made with different welding heat input. The microstructure, particularly inclusion content, of the weldment is dependant on the welding heat input applied. For an improper low heat input, the amount of inclusion at the weld was high. High inclusion content accelerated grooving corrosion at the weld. It is therefore that welding heat input should be controlled based on the carbon content of the pipe in order to improve the corrosion resistance of the ERW pipe.

전자비임용접한 $175Kg/mm^2$급 박판 Maraging강의 이음강도에 미치는 용접입열 및 열처리의 영향 (The effect of welding heat input and heat-treatment on the strength of the electron beam welded $175Kg/mm^2$ maraging steel sheet)

  • 윤한상;정병호;배차헌
    • Journal of Welding and Joining
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    • 제4권2호
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    • pp.21-29
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    • 1986
  • The influence of welding heat input variation(600-900J/cm) and heat-treatment condition after welding on tensile strength of butt welded joint in $175Kg/mm^2$ strength level Maraging steel(Co-free and Co-containing) sheets was investigated on the basis of hardness distribution, microstructure of weld metal and fracture surface. The obtained main results are as follows; 1. The strength of weldment (UTS, NTS), joint efficiency showed a little decreasing tendency with the increase in welding heat input, and the elongation showed a little increasing tendency with the increase in the width of weld metal. It was considered because of the plastic constraint of the high strength base metal. 2. The strength of weldment was better in the solution treatment and aging than the aging only after welding due to the disappearance of almost denverite in weld metal. 3. The hardness distribution in weldment after welding and heat-treatment was almost similar to both Co containing and Co free Maraging steel with change in welding heat input. 4. The fracture was occurred at weld metal, and the fracture surface showed a relatively shallow dimples in both Co containing and Co free Maraging steel.

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무산소동의 마찰 용접 특성에 관한 연구 (Study on the Frition Welding Characteristics of Oxygen Free High Conductivity Copper)

  • 정호신;소전강
    • 한국해양공학회지
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    • 제11권1호
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    • pp.10-15
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    • 1997
  • Copper and its alloy had been used widely because of its pronouncing characteristics on their high thermal and electrical conductivity. Various fusion welding methods, such as SMAW, SAW, GTAW, GMAW, Electroslag welding amd so on are applied to weld copper and its alloy. But fusion welding of copper has so many welding problems. THe most serious problems were poor penetration amd high thermal contration stress due to its high thermal conductivity and porosity could be formed by rapid cooling rate of fusion welding. In order to avoid such fusion welding problems, preheating, peering and heat treatment must be applied to obtain sound weld joint of copper. But preheating induce another welding problem such as grain coarsening of weld heat affected zone. This grain coarsening reduces ductility and strength of weld joint. In this view of point, friction welding of copper is triedm to obtain sound weld joint of copper by reducing metallurgical problems. This study introduced new concept of heat input for evaluating the friction weldability of copper. As a result, weldability of copper could be evaluated by this new concept of heat input.

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용접 입열량에 따른 고질소 TiN 강재의 용접부 충격인성 및 미세조직 변화에 관한 연구 (A Study on the Impact Toughness and Microstructure change for High Nitrogen TiN Steel Alloy with Welding Heat Input.)

  • 권순두;이광학;박동환
    • 대한용접접합학회:학술대회논문집
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    • 대한용접접합학회 2004년도 추계학술발표대회 개요집
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    • pp.123-124
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    • 2004
  • This study was investigated on the impact toughness and microstructure of welded metal and heat affected zone for Hi Nitrogen TiN Steel. With welding procedures, welding heat input applied were 30, 79 and 264 kJ/cm. TiN steel has shown very small prior austenite grain size for all the welding heat input applied, which was considered to result from the effect of TiN particles. In case of single SAW and EGW welding, the dilution rate of base metal into the weld was not high, resulting that there were no significant effects of base metal chemical composition on the mechanical properties of welds. However, TSAW with double Ypreparation carried very high dilution rate so that TiN steel has impaired the toughness of weld metal because N content in the weld was increased through the dilution of base metal.

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Duplex SS 육성 용접부의 물성에 미치는 열처리전 페라이트 함량의 영향 (The Effect of Ferrite Ratio on the Properties of PWHT Overlaid Welds)

  • 성희준;김영일;서창교
    • 대한용접접합학회:학술대회논문집
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    • 대한용접접합학회 2005년도 춘계학술발표대회 개요집
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    • pp.294-296
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    • 2005
  • Several duplex overlaied-weldments which have different ferrite ratio were prepared by changing welding heat input ant post weld heat treatment were carried out to understand the effect of the ferrite ratio on the precipitation during post weld heat treatment. High heat input weldment indicated low ferrite ratio, while low heat input weldment has high ferrite ratio. Low ferrite ratio weldment showed much and faster precipitation. But high ferrite ratio weldment showed less and slower precipitation.

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