Fluxless laser beam joining of aluminium with zinc coated steel

Abstract

A laser welding-brazing (LWB) process to join zinc coated steel and aluminium sheets in two different flange geometries is reported. The deep drawing steel sheets are covered by a zinc layer of maximum thickness 10 mm, and a zinc based filler wire was used in the welding experiments with a Nd-YAG laser. Because of the differences in melting temperatures between iron (1808 K), aluminium (933 K), and zinc (693 K), it is possible to weld the aluminium alloy only. Owing to the zinc coating on the steel side, a Zn-Al alloy can be brazed onto the steel without any flux agent. The inevitable formation of a Fe-Al intermetallic phase at the bondline of the weld seam and the steel can be limited to a thickness of less than 5 mm and to a proportion of the contact area only. Mechanical as well as dynamic tests show results comparable to those obtained via other joining techniques. Salt chamber corrosion tests of varnished specimens display minor damage and no decline in tensile strength.

Intermetallics Synthesis in the Fe–Al System via Layer by Layer 3D Laser Cladding

“…Another interesting direction is the laser welding of dissimilar materials, i.e., Fe and Al alloys, which is important for the aerospace and automobile industries where serious difficulties are caused by the high brittleness of the intermetallide phases generated in the melting pool [26][27][28][29][30][31]. On knowing the succession of the phase-structural transformations in the laser weld joint, it is possible to attain the fabrication creation of such a barrier layer of the alloying elements [26,27,30], that is capable of wetting the joining alloys on the basis of iron and aluminum, which protects them from the contact during the melting and prevents the formation of undesirable phases.…”

“…On knowing the succession of the phase-structural transformations in the laser weld joint, it is possible to attain the fabrication creation of such a barrier layer of the alloying elements [26,27,30], that is capable of wetting the joining alloys on the basis of iron and aluminum, which protects them from the contact during the melting and prevents the formation of undesirable phases. Different methods of the plasticity improvement of such welded joints exist, such as crystallographic structure modification, boundary strengthening, grain size decrease, columnar structure creation, micro-and macro-alloying.…”

Characterization of Intermetallic Compounds in Dissimilar Material Resistance Spot Welded Joint of High Strength Steel and Aluminum Alloy

“…15,16) The solid state welding techniques are expected to restrain the growth of the intermetallic compound layer within a permissible limit, which has been identified as 10 μm thickness, 17) but the adaptability of these methods is restricted in automotive industry due to equipment configuration. In the last few years, arc welding-brazing, [18][19][20][21] laser reactive wetting 6) and laser brazing 4,5,[22][23][24][25] of the dissimilar materials of steel and aluminum alloy have drawn great attentions. Lin et al [18][19][20] studied dissimilar metals TIG welding-brazing of aluminum alloy to stainless steel using Al-Si, Al-Cu and Al-Si-Cu filler wires.…”

Optimised design of electrode morphology for novel dissimilar resistance spot welding of aluminium alloy and galvanised high strength steel

“…The adaptability of these solid state welding methods is restrained to a certain extent in automotive industry due to the limitation on configuration and capacity of welding equipments. Besides, arc welding-brazing [19,20] and laser brazing [21][22][23] are also employed to weld aluminium alloy and steel. The results indicated that composition, morphology and thickness of the intermetallic compounds could be regulated with the introduction of filler metals, whereas cracks also tended to initiate at the intermetallic compounds and then propagate through them.…”