Laserstrahlschweißen von Stahl und Titan hoher Blechdicke unter dem Einfluss eines lokal reduzierten Umgebungsdruckes
Bibliographic record
Abstract
The increasing power of the laser beam sources allow a continuous expansions of applications, particularly for metals with high thickness. Due to the increase of the power, a number of negative effects arise which can adversely affect the welding result. That is particularly important for the metal vapour plume, that forms due to the high temperature in the keyhole and evolves in direction of the laser beam axis. The usable laser beam power is thus decreased and thereby the available power for the welding process declines as well. A suppression of the vapour plume is possible, with the help of an applied vacuum. Thereby, the complete amount of laser beam power is available for the welding process. This has positive effects on the welding depth and the weld quality. The limiting factor is the size of the vacuum chamber, which is adapted to the component to be welded. The aim of this study was to make the vacuum technology available independently of the component size. The patented pending vacuum cap presented in this thesis is placed at the welding area and movable in welding direction. The positive influence of the vacuum is used during the welding process, but it is not limited by the component size. The used local vacuum device has been specially designed for the available laser system, designed by CAD and manufactured afterwards. Instead of being made of glass, an aerodynamic window was used as a boundary layer between the ambient pressure and the vacuum region. For the design of the Laval nozzle in the aerodynamic window, a Schlieren test stand has been developed to make the stream visible. The positive influence of the welding under vacuum to the weld pool is independent of the composition of the material. However, the effect of the vacuum is stronger for some alloys compared to others. Steel was readily welded already under atmospheric conditions, whereas welding of titanium alloys succeeds only with high complexity of the shielding gas supply. For this reason, significant effects were expected for the titanium alloy. Therefore, the focus of this work lies on the titanium alloy Ti3Al2,5V. Previously, it was not possible to weld material thicknesses of 20 mm with satisfactory quality with a 20 kW fiber laser. Piineering tests were carried out on different thicknesses of S235 and S355. The great potential of this method was already shown for these structural steel types. The welding depths were increased by around 30 % to 50 % compared to the welding under atmospheric pressure. The transfer of the results on the titanium plates showed similar results. Again, a significant increase in the penetration depth up to 75 % can be observed under the influence of the local vacuum. Thus it was possible to weld thick titanium plates up to 28 mm with using fiber lasers.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.006 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".