Wyniki wyszukiwania - BazTech

1

A study on the CO2 laser welding characteristics of high strength steel up to 1500 MPa for automotive application

Kim C.-H., Choi J.-K., Kang M.-J., Park Y.-D.

Journal of Achievements in Materials and Manufacturing Engineering

|

2010

|

Vol. 39, nr 1

79-86

EN

Purpose: This paper presents the mechanical and metallurgical characteristics of laser weldments for automotive steels with high strength ranging from 370 MPa to 1500 MPa. Design/methodology/approach: Butt joint welding was conducted on high strength steel sheets by using a CO2 laser with 6 kW output power. For sound welds with full penetration, the proper welding conditions were chosen and the cross-sectional bead shape, tensile strength, hardness profile and micro-structure were evaluated for each case. Findings: Laser welding is known to be a low heat input process because of its high heat density and welding speed. But for laser welding of ultra high strength steel with strength over 780 MPa, micro-structural softening was observed in the HAZ (heat affected zone), resulting from dissolved martensite. Practical implications: The tensile strength reduction in laser welding of ultra high strength steed should be considered in the design of car body structures. The HAZ softening that occurs in butt joint welding can reduce the tensile shear strength for overlap joint welds, which are predominantly mostly used in the BIW (body-in-white) structure. Originality/value: This paper quantitatively demonstrates the occurrence of HAZ softening and a tensile strength reduction in laser welding of automotive steel with 780 MPa strength and more.

2

Position welding using disk laser-GMA hybrid welding

Kim C.-H., Lim H.-S., Kim J.-K.

Journal of Achievements in Materials and Manufacturing Engineering

|

2008

|

Vol. 28, nr 1

83-86

EN

Purpose: Position welding technology was developed by using disk laser-GMA hybrid welding in this research. Design/methodology/approach: The effect of hybrid welding parameters such as the shielding gas composition and laser-arc interspacing distance were investigated for the bead-on-plate welding. The pipe girth welding was implemented and the adequate arc welding parameters were selected according to the welding position from a flat position to an overhead position. Findings: The optimized shielding gas composition and laser-arc interspacing distance for disk laser-GMA hybrid welding were 80% Ar-20% CO2 and 2mm, respectively for the bead-on-plate welding. The sound welds could be achieved even in the pipe girth welding, but the proper joint shape should be prepared. Research limitations/implications: The laser-arc hybrid welding was implemented for pipe girth welding as a kind of 3-dimensional laser welding and the process parameters could be optimized according to the various target materials and sizes. Practical implications: The optimized process parameters for the disk laser-arc hybrid welding can extend the application of the laser hybrid welding technology. Originality/value: This research showed the possibility of the disk laser-GMA hybrid welding as new pipe girth welding technique. The behaviour of molten pool and droplet transfer could enhance understanding of the hybrid welding.

3

Weldability during the laser lap welding of Al 5052 sheets

Kim J.-K., Lim H.-S., Cho J.-H., Kim C.-H.

Archives of Materials Science and Engineering

|

2008

|

Vol. 31, nr 2

113-116

EN

Purpose: The paper presents the effect of the laser welding parameters of the laser focal position, the welding speed and the laser output power on the weldability of Al the 5052 alloy during laser lap welding. Design/methodology/approach: Lap welding is conducted on an Al 5052 plate with a thickness of 1 mm. After welding, the bead surfaces and cross sections were evaluated with various laser welding parameters. The degree of porosity was also examined by X-ray transmission testing. Findings: The influences of the focal point, the laser power and the welding speed on the formation of bead and on the degree of porosity were experimentally investigated. The bead quality was improved when the beam was defocused compared to when it was focused on the surface. It was found that the porosity decreased when the heat input is lowered, except when the lower plate is not melted. Research limitations/implications: Various types of aluminium alloys, such as sheet, extrusion and casting types, are used industrially in diverse combinations. Therefore, it is necessary to evaluate the weldabilities of these materials. This research is limited to Al 5052 alloys at present plans are underway to expand it to various aluminium based alloys. Practical implications: Automotive industries are continuously increasing their use of aluminium alloys in manufacturing. The results of this research can be referred to by the automotive industry as a basic technique. Originality/value: This research shows the influence of different welding parameters on the weldability during the lap welding of Al 5052 Al alloy. The results are based on the extensive experiments.