Evaluation of the effect of focal plane position on the penetration depth in laser welding of high-strength steel

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Abstract

The article presents the results of laser welding of steel using the lenses with a focal length of 300, 500, 700 and 900 mm. The effect of focal plane position of laser radiation relative to the work surface of the welded plate on the weld penetration depth has been evaluated. The research is based on a series of experimental welding samples using the lenses with various focal lengths and controlled changes in the focal point relative to the welded plate surface. The results can be used to select the process modes for laser welding of thick high-strength steels and to develop recommendations for the equipment adjustment.

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About the authors

Yarob Aldaiee

Peter the Great St. Petersburg Polytechnic University

Author for correspondence.
Email: aldaiee.yarob@gmail.com
ORCID iD: 0009-0000-7968-668X

engineer of the research laboratory “Laser and Additive Technologies”, Institute of Mechanical Engineering, Materials and Transport

Russian Federation, St. Petersburg

Daria A. Kuznetsova

Peter the Great St. Petersburg Polytechnic University

Email: kuznetsova_da@spbstu.ru
ORCID iD: 0009-0003-3938-5710

engineer of the research laboratory “Laser and Additive Technologies”, Institute of Mechanical Engineering, Materials and Transport

Russian Federation, St. Petersburg

Maxim E. Pirogov

Peter the Great St. Petersburg Polytechnic University

Email: maks.pirogov2000@mail.ru
ORCID iD: 0009-0006-7374-4635

engineer of the research laboratory “Laser and Additive Technologies”, Institute of Mechanical Engineering, Materials and Transport

Russian Federation, St. Petersburg

Mikhail V. Kuznetsov

Peter the Great St. Petersburg Polytechnic University

Email: kuznetsov_mich@mail.ru
ORCID iD: 0000-0002-9981-1078

Cand. of Sc. (Techn.), Head of the Research Laboratory “Laser and Additive Technologies”, Director of the Russian-German Center for Laser Technologies, Institute of Mechanical Engineering, Materials and Transport

Russian Federation, St. Petersburg

Anatoly A. Popovich

Peter the Great St. Petersburg Polytechnic University

Email: director@immet.spbstu.ru
ORCID iD: 0000-0002-5974-6654

Dr. of Sc. (Techn.), professor, director of the Institute of Mechanical Engineering, Materials and Transport

Russian Federation, St. Petersburg

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Supplementary files

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2. Fig. 1. Robotic process system for hybrid laser-arc welding (RPS HLAW)

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3. Fig. 2. Results of the beam quality measurements at the output of the optical head 100/500 mm (length of the optical cable 15 m); the measurements have been carried out using the Primes device (measured parameter ВРР = 4,1 mm · mrad)

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4. Fig. 3. Schematic diagram for determining the focal plane position in the pulse mode

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5. Fig. 4. Plate with the prints: a) focal lengths of lenses 300 and 500 mm; b) focal lengths of lenses 700 and 900 mm

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6. Fig. 5. Print traces after the laser beam impact: a) observation instrument – inverted optical microscope IM7004L; b) focal length F = 300 mm; c) F = 500 mm; d) F = 700 mm; e) F = 900 mm

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7. Fig. 6. Dependence of the print diameter D1, D2, D3 and Dav on the focal plane displacement dF from the processed surface of the welded plate for the lenses: a) focal length F = 300 mm; b) F = 500 mm; c) F = 700 mm; d) F = 900 mm

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8. Fig. 7. Schematic of experimental points and their approximation function

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9. Fig. 8. Approximation function for three experiments D1, D2, D3 and 95% prediction range for the lenses: a) focal length F = 300 mm; b) F = 500 mm; c) F = 700 mm; d) F = 900 mm

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10. Fig. 9. Experimental samples: a) first plate; b) second plate; c) plates after cutting

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11. Fig. 10. Sections after welding using the lenses: a) focal length F = 300 mm; b) F = 500 mm; c) F = 700 mm; d) F = 900 mm

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12. Fig. 11. Dependence of the penetration depth h on the focal displacement dF for the lenses: a) focal length F = 300 mm; b) F = 500 mm; c) F = 700 mm; d) F = 900 mm

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Copyright (c) 2025 Aldaiee Y., Kuznetsova D.A., Pirogov M.E., Kuznetsov M.V., Popovich A.A.