High‐power Full Penetration Welding Behavior

Abstract

AuTHORSDue to their different physical beam characteristics, there are fundamental differences in the process behavior of Co 2 lasers and solid-state lasers during deep penetration welding. High-quality full penetration welds can be achieved in thick sheet metal with both beam sources. However, the beam sources differ in regards to productivity, process stability, and seam quality depending on the material being welded.CO 2 lasers and solid-state lasers (SSLs) are the most commonly used beam sources for laser welding. featuring high laser power combined with high beam quality, CO 2 lasers have been on the market since the 1980s. Thanks to their high electrical efficiency and the simplicity of guiding the beam through appropriate cables, SSLs with wavelengths around the 1 µm mark are increasingly used in industrial manufacturing. The development of diode-pumped disk and fiber lasers enabled these laser systems to catch up on CO 2 lasers regarding power and beam parameter product, resulting in an increase in the maximum attainable weld depth.Virtually all industrial thick sheet metal applications larger than 8 mm require a full penetration weld for reasons of strength, for example in the fields of shipbuilding, train and railroad construction, and pipeline engineering as well as for welding axle drives [1]. While deep penetration welding using CO 2 lasers is characterized by outstanding seam quality allied to high process reliability over a broad range of parameters, the seam quality achieved using solid-state lasers is more dependent on the material and process parameters. This article will compare the suitability of the two beam sources for full penetration welding.

Root formation and metallurgical challenges in laser beam and laser-arc hybrid welding of thick structural steel

“…At larger defocusing distances (FPP > 30 mm), the humping and then the lack of penetration (at FPP ≈ 40 mm) occur due to larger spot diameter at the surface, and thus lower power intensity. This trend agrees with other researchers [6,18,27]. There is a possible process window, characterized by a smooth root appearance with a slight reinforcement, when there is a balance between laser power and FPP to obtain full penetration and the occurrence of melt ejections.…”

“…3.8), a Fig. 15 Comparison of present study case a with published results from b, c TRUMPF GmbH [5,27] and d, e Osaka University [18]. IP is incomplete penetration, H is humping mode, GR is bandwidth providing good (acceptable) root quality, and ME is melt ejection mode.…”

“…Reisgen et al [3] showed that good root quality can be achieved even in welding of 50 mm thick steel plates with single-pass using only 16 kW disk laser power (in vacuum, pressure at 0.1 kPa) at 0.25 m/min welding speed. Researchers from TRUMPF GmbH published results [43] showing a promising equipment with improved coaxial shielding during LBW providing smooth root quality, while conventional shielding conditions provided humping. In fact, such studies are very rarely published.…”

Laser-arc hybrid welding of 12- and 15-mm thick structural steel

“…Evidently, with an increase of plate thickness from 12 to 15 mm, the frequency of humping occurrence is higher due to an increased molten mass of the weld pool. It was shown that duplex stainless steels having very different chemical composition provides much less humping [55]. Pan et al [56] showed that the use of CO 2 in the shielding gas significantly increased the process window, which may be attributed to the change of molten metal chemistry and physical properties such as surface tension.…”