• Journal of Welding and Joining
• /
• 제10권1호
• /
• pp.20-34
• /
• 1992

Characteristics of two correcting methods, a new Autogeneous GTAW heating (TIG) method and the conventional GMAW bead-on plate welding(MIG) method, for distorted aluminum fabrication structures were studied. As a result of microscopic study of Autogeneous GTAW heating and GMAW bead-on plate welding areas, porosities in weld metal and surface cracks in local heating zone were found. Through the mechanical tests, it was verified that porosities decrease tensile strength and surface of distortion, angular displacement and transeverse shrinkage were measures and compared. In order to investigate changes of material properties in heating area and cause of defects such thermal stresses were calculated by ADINA. Through the computations of transient thermal stresses and microscopic observation of fracture surface, thermal stress was found to be the cause of crack during Autogeneous GTAW heating.

• Journal of Welding and Joining
• /
• 제14권2호
• /
• pp.79-89
• /
• 1996

일정진폭하중과 과대하중비 2.5의 단일 인장과대하중에 의한 4140강 용접부 의 피로균열성장거동을 실온과 -45.deg.C의 저온에서 피로시험과 파면관찰을 통하여 고찰하였다. 이때, 용접부 미시조직의 영향을 평가하기 위해 모재(parent metal), 열영향부(as-welded HAZ), 열처리된 열영향부(PWHT HAZ)로 나누어 응력비 0과 0.5로 CT시험편을 이용하여 피로시험을 실시하였다. 피로균열성장거동은 재료의 미시조직과 온도변화보다는 응력비에 크게 영향을 받았으며, 단일 과대하중에 의한 피로균열성장 지연효과가 모든 재료에서 상당히 크게 나타났다. 전자현미경에 의한 피로파면 관찰 결과, 실온에서는 연성의 스트라이에이숀과 -45.deg.C에서는 의벽개파면과 같은 피로 균열성장거동을 나타내고 있다.

• 대한용접접합학회:학술대회논문집
• /
• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
• /
• pp.499-504
• /
• 2002

The microstructural change associated with the hardness profile in friction stir welded, age-hardenable 6005 Al alloy had been evaluated. Frictional heat and plastic flow during friction stir welding created the fine recrystallized grain (Stir Zone, SZ), the elongated and recovered grain (Thermo-Mechanical Affected Zone, TMAZ) in the weld zone. Heat affected zone (HAZ), which could be only identified by hardness test because there is no difference in the grain structure compared with that of the base metal, was formed beside the weld zone. A softened region had been formed near the weld zone during friction stir welding process. The softened region was characterized by the dissolution and coarsening of the strengthening precipitate during the friction stir welding. The sound joints of 6005 Al alloys were successfully formed under a wide range of the friction stir welding conditions.

• Journal of Welding and Joining
• /
• 제8권2호
• /
• pp.27-39
• /
• 1990

The effect of silicon and manganese, in the ranges of 0.3% to 1.0wt% Si and 0.7 to 2.6wt%Mn, on the microstructure and mechanical properties of flux cored arc welded deposits have been investigated for the purpose of improving mechanical properties. Microstructure of weld metals was mainly influenced by manganese content, and manganese increased the volum fraction of acicular ferrite and refined the microstructure. Also, tensile properties were governed by manganese content, ultimate tensile strength and yield strength were increased by approximately 82MPa and 58MPa per 1% Mn addition to the deposit. Toughness was improved by increasing Mn content and lowering Si content. Optimal impact properties were obtained at above 1.8wt% Mn and below 0.5wt% Si. Acicular ferrite was predominant factor in improving mechanical properties. Formation of acicular ferrite was promoted by manganese and no direct relationship between AF(acicular ferrite) proportion and oxygen in weld metal was found.

• 한국공작기계학회:학술대회논문집
• /
• 한국공작기계학회 2003년도 추계학술대회
• /
• pp.289-294
• /
• 2003

The object of this study is to investigate the effect of compounded welding by using acoustic emission (AE) signals fur weld heat affected zone (HAZ) in tensile testing. This study was carried out a SM 490A high tension steel for electronic shielded metal are welding (SMAW), $\textrm{CO}_2$ gas arc welding and TIG welding. And correspondingly, the root openings are 3, 4 and 2.8mm. Data displays are based on the measured parameters of the AE signals, along with environmental variables such as time and load. These history plots give us useful and powerful information to analyze the results of material evaluation testing.

• 한국공작기계학회:학술대회논문집
• /
• 한국공작기계학회 2003년도 춘계학술대회 논문집
• /
• pp.363-370
• /
• 2003

The object of this study is to investigate the effect of compounded welding by using an acoustic emission (AE) signals and doing a source location for weld heat affected zone (HAZ) through tensile testing. This study was carried out a SM 490A high tension steel for electronic shielded metal arc welding (SMAW), $CO_2$ gas arc welding and TIG welding. Data displays are based on the measured parameters of the AE signals, along with environmental variables such as time and load. These history plots are displays showing the chronological course of the test. Also, source location gives the X- and Y-coordinates of the AE source.

• Journal of Welding and Joining
• /
• 제20권4호
• /
• pp.534-537
• /
• 2002

In the various industry such as shipbuilding and automobile, etc., Al-alloys are used to reduce weight and improve economical efficiency, and they are mainly utilized in the process of Friction Stir Welding (FSW). A number of studies have been carried out on the metallurgical characteristics of friction stir welding In Al-alloys. However, research on the thermal behavior of FSW by using numerical analysis is not sufficient in the domestic and abroad. In this paper, therefore, numerical simulation was used to find out thermal behaviour of FSW by finite element method. We considered heat source that occurred by friction between tool shoulder including pin and base metal. To confirm the result of simulation, macrostructure is examined and compared after welding. The result of numerical simulation shows that Al-alloy is welded under a melting point of Al around pin by FSW.

• 대한용접접합학회:학술대회논문집
• /
• 대한용접접합학회 2006년도 춘계 학술대회 개요집
• /
• pp.140-142
• /
• 2006

The bend ductility of Type 410S ferritic stainless steel overlay weld on carbon steel was investigated. Overlay weld that was stabilized with Nb had large columnar ferrite grain and Nb precipitate on grain boundary. And that caused fracture when bend test without concern of PWHT condition. Proper bend ductility at as-welded condition was achieved by refining ferrite grain with addition of $0.04{\sim}0.09%$ Al and $0.2{\sim}0.5%$ Ti that make oxide, carbide and nitride at high temperature.

• 대한용접접합학회:학술대회논문집
• /
• 대한용접접합학회 1997년도 특별강연 및 추계학술발표 개요집
• /
• pp.147-150
• /
• 1997

The characteristics of underwater welding of SWS490 steel were investigated. The bead-on-plate type welding with one or three pass using ilmenite and water-proofed type electrodes was performed by varying welding currents and the sizes of electrodes used. The amounts of hydrogen absorbed inter the weld metal were measured according to the JIS Z 3118 specification and the results were interpreted in terms of the cold cracking behaviours of the welded steel. The microstructural changes as well as the microhardness distribution after underwater welding were also investigated using Vickers microhardness tester and S.E.M (scanning electron microscopy) and O.M (optical microscopy). The results indicated that the cold cracking could be avoided by three pass welding under low current with an electrode with a small diameter.

• 대한용접접합학회:학술대회논문집
• /
• 대한용접접합학회 2003년도 추계학술발표대회 개요집
• /
• pp.256-258
• /
• 2003

Hot-rolled and Extruded plates of AZ type magnesium alloys were successfully joined by friction stir welding(FSW). AZ31B-H24 and AZ61 plates with the thickness of 4mm were used, and the microstructural development in the stir zone were investigated using optical and scanning electron microscopes. The grain size of base metal and stir zone were investigated using the line-intersecter method. Hardness of the stir zone was remarkably increased due to very fine recrystallized grain structure both in AZ3l and AZ6l alloys. Tensile strengths of the FS welded Mg alloys AZ31 and AZ61 were strongly affected by formation of the intermetallic compounds, ${\beta}$-Al$\sub$12/Mg$\sub$17/.