Muneharu Kutsuna

Interaction of both plasmas in CO2 laser-MAG hybrid welding of carbon steel

Researches and developments of laser and arc hybrid welding has been curried out since in 1978. Especially, CO2 laser and TIG hybrid welding has been studied for increasing the penetration depth and welding speed. Recently laser and MIG/MAG/Plasma hybrid welding processes have been developed and applied to industries. It was recognized as a new welding process that promote the flexibility of the process for increasing the penetration depth, welding speed and allowable joint gap and improving the quality of the welds. In the present work, CO2 Laser-MAG hybrid welding of carbon steel (SM490) was investigated to make clear the phenomenon and characteristics of hybrid welding process comparing with laser welding and MAG process. The effects of many process parameters such as welding current, arc voltage, welding speed, defocusing distance, laser-to-arc distance on penetration depth, bead shape, spatter, arc stability and plasma formation were investigated in the present work. Especially, the interaction of laser plasma and MAG arc plasma was considered by changing the laser to arc distance (=DLA).

Laser roll welding of dissimilar metal joint of zinc coated steel to aluminum alloy

There is a subject to reduce the weight of car body by replacing steel to aluminum alloys as some structural body parts for improving fuel consumption and suppressing CO2 generation. As one of the solutions, the hybrid body structure concept using aluminum alloys and high strength steels is proposed recently. However, it is well known that fusion welding of steel and aluminum is difficult due to the formation of brittle intermetallic compounds at the joint interface. Therefore, new welding processes by which these dissimilar materials can be joined in high reliability and productivity are demanded. “Laser roll welding” has been developed for joining of dissimilar metals by Kutsuna, Rathod, and Tsuboi in 2002 (Japanese Patent No. 3535152 and No. 3692135). Controlling the formation of the brittle imtermetallic compounds was tried by application of laser roll welding to get a sound joint. In the present work, laser roll welding of zinc coated steel and aluminum alloy was fundamentally investigated, and the process parameters were studied. Furthermore, the influences of process parameters on the weldability, the formation of intermetallic compound layer, and the joint properties have been investigated to get a sound joint. When intermetallic compound layer thickness was less than 10 μm, failure of tensile shear test specimen occurred in the base metal of the zinc coated steel.There is a subject to reduce the weight of car body by replacing steel to aluminum alloys as some structural body parts for improving fuel consumption and suppressing CO2 generation. As one of the solutions, the hybrid body structure concept using aluminum alloys and high strength steels is proposed recently. However, it is well known that fusion welding of steel and aluminum is difficult due to the formation of brittle intermetallic compounds at the joint interface. Therefore, new welding processes by which these dissimilar materials can be joined in high reliability and productivity are demanded. “Laser roll welding” has been developed for joining of dissimilar metals by Kutsuna, Rathod, and Tsuboi in 2002 (Japanese Patent No. 3535152 and No. 3692135). Controlling the formation of the brittle imtermetallic compounds was tried by application of laser roll welding to get a sound joint. In the present work, laser roll welding of zinc coated steel and aluminum alloy was fundamentally investigated, and the p...

Laser-roll welding of a dissimilar metal joint of low carbon steel to aluminium alloy using 2 kW fibre laser

Recently, lightening, speed-up and decreasing vibration of the transport vehicles have been discussed for improving of environmental problems. As one solution, the material hybrid concept using aluminum alloys and high strength steels has been proposed. Therefore, new welding processes by which these dissimilar materials can be joined in high reliability and productivity are demanded. Laser roll welding was developed for joining of dissimilar metals by M. Kutsuna, M. Rathod and A. Tsuboi in 2002. Up to now, a CO2 laser has been used as a heat source. In the present work, laser roll welding of low carbon steel and aluminum alloy using a 2 kW fibre laser was investigated to improve the joint properties due to the effective heating characteristics. Effects of the process parameters were studied. Otherwise, the influences of process parameters on the weldability, the formation of intermetallic compound layer and the mechanical properties have been investigated. As a result, various types of intermetallic compound layer were confirmed at the laser roll welded joint interfaces. When intermetallic compound layer thickness was less than 10 μm, the specimen was a failure in the base metal of low carbon steel in the tensile shear test.

Study on porosity formation in laser welds of aluminium alloys (Report 2). Mechanism of porosity formation by hydrogen and magnetism

Summary The CO2 laser welding of A3003, A7N01, A5052 and A5182 aluminium alloys, was carried out at different welding speeds and laser powers. The behaviour of porosity in the laser welds was investigated to make clear the mechanism of porosity formation. Three types of porosity of more than 20 μm in diameter were observed. According to the analysis of porosity gas in the laser welds of aluminium alloys, hydrogen was about 60 to 80 vol% of the total gas, with the rest being nitrogen and helium. For the laser welds of Al-Mg alloys, most small pores were formed along the solute band with magnesium enrichment, since magnesium had higher solubility for hydrogen in the liquid state than pure aluminium. It is concluded that porosity formation is greatly influenced by the magnesium content of Al alloys and hydrogen owing to the interaction of hydrogen and magnesium.

Steel-to-Aluminum Joining by Control of Interface Microstructures - Laser-Roll Bonding and Magnetic Pulse Welding -

Laser-roll bonding and magnetic pulse welding are two relatively new processes that greatly minimize problems of metallurgical incompatibilities between dissimilar metals and alloys. These two processes, though technologically apart and invented for components with distinct geometries, utilize to various extents high pressures to facilitate rapid and localized interfacial heating and create reliable joints. In this paper, relations between process parameters, microstructures, and properties are discussed for aluminum-to-steel joints made by laser-roll bonding and magnetic pulse welding.

Laser roll welding of dissimilar metal joint of titanium to aluminium alloy

Recently, the demand for dissimilar metal joints of titanium to aluminium alloy has arisen in industry, especially in the transportation vehicle industry. However, it is well known that fusion welding of titanium to aluminium alloy is difficult because of generating the brittle intermetallic compound at the joint interface. Therefore, new welding processes with high reliability and productivity for these dissimilar materials are demanded. In the present work, Laser roll welding of titanium to aluminium alloy using a 2 kW fibre laser was tried to investigate the effects of the process parameters on the formation of the interlayer and the mechanical properties of the joint. As a result, the cross-section of the joint shows partial melting of the aluminium sheet and spreading of molten aluminium alloy on the titanium sheet occurs during the welding thermal cycle. Various types of intermetallic compound were confirmed at the interlayer of the welded joint. The specimen with a bonding width of 2.8 mm failed in the base metal of titanium in the tensile shear test. In Erichsen cupping tests, the Erichsen value was 5.7 mm. This value was 89% of the base metal of aluminium sheet.

Waterjet-guided laser processing

The waterjet-guided laser processing is a thermal cutting process in which the laser beam is used as the machine tool for cutting and the fine waterjet plays a role as an optical waveguide. The laser beam is guided in the waterjet stream with the full reflection that takes place at the boundary between water and air, in a manner similar to glass fibers. The waterjet also has the function of waveguiding and removing the cut products. The diameter of the waterjet can be controled between 50 and 200 μm. The diameter of laser beam is completely utilised. The useful length of waterjet is usually approximately 50 to 100 mm. The type of laser used is a pulsed Nd:YAG laser. The advantages of waterjet-guided laser processing are (1) no Z-axis control, (2) narrower cut widths down to 50 μm, (3) very small heat affected zone, (4) a little oxidation of the cut edges, and (5) no assist gas for cutting. A reseach was carried out for the new industrial application which is unsuitable by conventional laser cutting.

Study on porosity formation in laser welds in aluminium alloys (Report 1) : Effects of hydrogen and alloying elements

Summary The CO2 laser welding of aluminium alloys, A3003, A6061, A6N01, A5052, A5083 and A5182, was carried out at different welding speeds and the behaviour of porosity formed in the laser welds was investigated to make clear the mechanism of porosity formation. Three types of porosity were observed. The observed number of voids (Type A) of less than 50μm diameter decreased with an increase in welding speed and solidification rate because of lack of time for nucleation and growth of gas bubbles during laser welding. According to the analysis of porosity gas in the laser welds of A3003, A6061, A6N01 and A5052, hydrogen was about 90 vol% of total porosity gases and the rest was nitrogen. And for A5083 and A5182 alloy welds with deeper penetration, a small amount of helium, used as a shielding gas, was also detected. Besides, for the laser welds in Al-Mg alloys, the majority of porosity was formed along the solute band with Mg enrichment. The Mg induced polygonal porosity (Type C) and larger porosity (Type ...

Dissimilar Metal Joining of Zinc Coated Steel and Aluminum Alloy by Laser Roll Welding

© 2012 Ozaki and Kutsuna, licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Dissimilar Metal Joining of Zinc Coated Steel and Aluminum Alloy by Laser Roll Welding

Fiber laser welding of 780MPa high strength steel

A 2kW Ytterbium fiber laser, YLR-2000, was used for welding of 780MPa grade high strength steel. In the present work, this high strength steel is a kind of heat rolled, fine microstructure low carbon high strength steel used for welded constructions. The effects of defocusing distance, welding speed, shielding gas and its flow rate on cross section bead shape and penetration were studied in continue wave laser beam welding. The effects of frequency and duty cycle on the cross section bead shape and penetration were also studied in pulse fiber laser beam welding. In the fiber laser welding, square wave and triangle wave power output were adopted. The results showed that the pulse frequency and duty cycle of laser power had affected the bead shape and penetration in square wave Fiber laser welding. The pulse frequency of laser power had not effect on the bead width and penetration in triangle wave fiber laser welding. The microstructures of weld metals in different heat input were observed by optical microscopy. The hardness of welds was also tested and compared among welds welded at different welding speeds, in other words, in different heat inputs.A 2kW Ytterbium fiber laser, YLR-2000, was used for welding of 780MPa grade high strength steel. In the present work, this high strength steel is a kind of heat rolled, fine microstructure low carbon high strength steel used for welded constructions. The effects of defocusing distance, welding speed, shielding gas and its flow rate on cross section bead shape and penetration were studied in continue wave laser beam welding. The effects of frequency and duty cycle on the cross section bead shape and penetration were also studied in pulse fiber laser beam welding. In the fiber laser welding, square wave and triangle wave power output were adopted. The results showed that the pulse frequency and duty cycle of laser power had affected the bead shape and penetration in square wave Fiber laser welding. The pulse frequency of laser power had not effect on the bead width and penetration in triangle wave fiber laser welding. The microstructures of weld metals in different heat input were observed by optical micros...