Development of AC-MIG welding process(Report 5). Application of AC-MIG narrow gap welding process for butt joints of 980MPa high strength steels.

Tsushima, Sadao; Horii, Yukihiko; Yurioka, Nobutaka

doi:10.2207/qjjws.12.51

Cited by 2 publications

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“…4,5 Considering the hardness values ranging from 280 to 390 Hv, the reduction in the absorbed energy can also be attributed to the microstructural change from martensite and bainite to granular bainite. In this connection, the SEM observation of the weld metal after two step electrolytic etching suggested the formation of MA constituent, namely an embrittlement factor formed in the granular bainite, when the CO 2 content of the shielding gas was 15% or more (Fig.…”

Section: Discussionmentioning

confidence: 99%

“…The weld metal produced using pure Ar shielding gas having O content much lower than those of other weld metals should also be taken into account to account for the very high Charpy energy, since it has been reported that the toughness of the weld metal for 950 MPa class steel is increased monotonically with reduction in O content. 4,5 Considering the hardness values ranging from 280 to 390 Hv, the reduction in the absorbed energy can also be attributed to the microstructural change from martensite and bainite to granular bainite. In this connection, the SEM observation of the weld metal after two step electrolytic etching suggested the formation of MA constituent, namely an embrittlement factor formed in the granular bainite, when the CO 2 content of the shielding gas was 15% or more (Fig.…”

Section: Discussionmentioning

confidence: 99%

“…[1][2][3][4][5] Controlling the weld metal microstructures as well as raising the welding productivity are critical factors for the development of weld metal of high strength steel to secure satisfactory mechanical properties and to reduce production costs. In order to meet the demand to apply 950 MPa class steel to the fabrication of large scale steel structures, a weld wire for the 950 MPa class steel has been under development to obtain the required strength and toughness, which depend primarily on the microstructure.…”

Section: Introductionmentioning

confidence: 99%

“…In order to extend the use of HSLA steels of more than 780 MPa for a variety of welded structures such as building, bridge, penstock, line pipe and offshore structures, many investigations have been made of the microstructures of weld metals and heat affected zones for these steels. [1][2][3][4][5] Controlling the weld metal microstructures as well as raising the welding productivity are critical factors for the development of weld metal of high strength steel to secure satisfactory mechanical properties and to reduce production costs. In order to meet the demand to apply 950 MPa class steel to the fabrication of large scale steel structures, a weld wire for the 950 MPa class steel has been under development to obtain the required strength and toughness, which depend primarily on the microstructure.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Microstructures of gas metal arc weld metal of 950 MPa class steel

Gouda¹,

Takahashi²,

Ikeuchi³

2005

Science and Technology of Welding and Joining

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The effects of shielding gas composition on the properties and microstructure of single pass weld metals produced by GMA (gas metal arc) groove welding of 950 MPa class steel plates have been investigated. The shielding gas employed was a mixture of argon (Ar) and carbon dioxide (CO 2 ) (0-25%), and the weld heat input was ,3 kJ mm. With increasing CO 2 content, the hardness of the weld metal decreased from 380 HV to 280 HV, and the absorbed energy of the Charpy impact test decreased from 130 J to 90 J. The microstructures of the weld metal, consisting primarily of low carbon martensite and carbide free bainite, became more bainitic as the CO 2 content of the shielding gas was increased. It was also found that the MA constituent, embrittling microstructure, was formed in the granular bainitic area, the volume fraction of which increased with the CO 2 content of the shielding gas.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Microstructures of gas metal arc weld metal of 950 MPa class steel

Gouda¹,

Takahashi²,

Ikeuchi³

2005

Science and Technology of Welding and Joining

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Shibahara¹,

Dan²,

WU³

et al. 2010

J.JASNAOE

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To achieve high efficiency and cost reduction, large heat input welding such as submerged arc welding (SAW) and metal inert gas arc welding (MIG) using large currents are employed. However, the large heat input given to the weld may produce coarse grains in the HAZ and a reduction of toughness. To avoid these problems, narrow gap welding (NGW) which is effective in reducing heat input and achieving high productivity is often employed. However, the pear-shaped bead cracking may form according to the welding condition in the case of narrow gap welding. Therefore, the welding conditions must be carefully selected to prevent the cracks. In this study, the influences of the heat input parameters, such as heat input width, heat input depth and the total amount of heat input on the pear-shaped bead crack formation under narrow gap welding are investigated using the Thermal-elastic-plastic FEM with temperature dependent interface element. Furthermore, to find the optimum values of the heat input parameters, the optimization system which can consider the formation of pear-shaped bead cracking is developed. As optimization methods, Complex Method (CM) and Genetic Algorithm (GA) are adopted. Using these methods, the ideal heat input distribution to achieve deeper penetration with small heat input and without cracking can be computed. As a result, the superiority of the welding using narrow gap can be shown in the viewpoint of heat input efficiency.

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Development of AC-MIG welding process(Report 5). Application of AC-MIG narrow gap welding process for butt joints of 980MPa high strength steels.

Cited by 2 publications

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Microstructures of gas metal arc weld metal of 950 MPa class steel

Microstructures of gas metal arc weld metal of 950 MPa class steel

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