Microstructure and mechanical properties of laser surface treated 44MnSiVS6 microalloyed steel

Dewi, Handika Sandra; Fischer, Andreas; Volpp, Jöerg; Niendorf, Т.; Kaplan, Alexander

doi:10.1016/j.optlastec.2020.106139

Cited by 18 publications

(12 citation statements)

References 22 publications

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“…The grain refinement and precipitation hardening improve the strength of HSLA steels; therefore, they are suitable for car body applications. The elements such as Ti and Nb form precipitates that control grain growth and cause precipitation strengthening [9,10]. Most HSLA steels are supplied in the as-hot-rolled condition with ferritic-pearlitic microstructure.…”

Section: Introductionmentioning

confidence: 99%

Joining the High-Strength Steel Sheets Used in Car Body Production

Kaščák¹,

Cmorej²,

Spišák³

et al. 2021

Adv. Sci. Technol. Res. J.

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Nowadays, there are several important reasons for using high-strength sheets in the manufacturing of car bodies. Car manufacturers choose the steel with good formability, fatigue resistance and ability to absorb impact energy. Microalloyed steels and dual-phase steels are the materials which fulfil the above-mentioned criteria. The application of high-strength sheets has led to the development of new materials joining techniques. Mechanical joining, such as clinching, is the innovative technique to join these progressive materials. Materials of different thicknesses can be joined by clinching. The paper focuses on the comparison of the properties of the joints made by clinching and resistance spot welding. The application of resistance spot welding is still the most used joining method in car body production. These properties were investigated by tensile test and metallographic observation. The HCT600X+ZF, HCT600X+Z and HX420LAD+Z steel sheets were used for the experiments. The results of tensile test show that the values of load-bearing capacity of clinched joints reached from 3900 N to 5900 N and the resistance spot welded joints reached the values of load-bearing capacity from 12000 N to 19500 N. In comparison to the resistance spot welded joints, the clinched joints reached from 32 to 48% of load-bearing capacity.

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Section: Introductionmentioning

confidence: 99%

Joining the High-Strength Steel Sheets Used in Car Body Production

Kaščák¹,

Cmorej²,

Spišák³

et al. 2021

Adv. Sci. Technol. Res. J.

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“…This is in line with previous studies on a similar steel grade. Due to the extremely rapid nature of laser treatment, the material is not fully austenitized, and ferrite islands remain due to the limited time for carbon diffusion [7]. In case of the present work, the absolute values are similar for both surface geometries.…”

Section: Residual Stress Analysismentioning

confidence: 58%

“…The use of a laser beam as a heat source in order to illuminate the surface provides the advantage of a controlled and local heat input. However, the depths of the hardened zone is mostly comparably narrow due to the limited dwell time, which might not give enough time for microstructural transformations in deeper regions (e.g., [7]). It was shown that the fast thermal cycle leads to a different microstructural appearance compared with traditional heat treatments due to the limited time for carbon diffusion (e.g., [8]) inherent to the rapid laser processes.…”

Section: Introductionmentioning

confidence: 99%

“…It was shown that the fast thermal cycle leads to a different microstructural appearance compared with traditional heat treatments due to the limited time for carbon diffusion (e.g., [8]) inherent to the rapid laser processes. In consequence, ferrite islands can be present although austenitization temperature was reached at the surface and in subsurface areas [7].…”

Section: Introductionmentioning

confidence: 99%

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Influence of complex geometries on the properties of laser-hardened surfaces

Volpp

Dewi

Fischer

et al. 2020

Int J Adv Manuf Technol

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Laser surface hardening provides for many advantages in terms of flexible production due to very localized and controlled energy input into the material. Laser processing offers the possibility to treat surfaces in order to locally strengthen the areas that are prone to fatigue cracking. It is well known that laser energy absorption depends on many parameters, e.g., the surface structure and the surface orientation. The incident angle of the laser beam plays a key role in this regard. When complex geometries like crankshaft fillets are treated, the surface cannot be considered a series of flat surfaces. Obviously, this leads to locally varying degrees of energy absorption. In the present work, curved surface structures were chosen in order to analyze the impact of the geometrical characteristics on surface and subsurface material properties after laser treatment. Microstructure evolution generally was found to be similar for flat and curved geometries. However, even if higher absorption in the groove due to the illumination at larger incident angles was expected, the outer parts of the curved geometry were not fully hardened. Thus, the increased effective length of the complex geometry-treated and the larger heat-affected volume are expected to have a more dominant influence on the final appearance of the subsurface microstructure. Eventually, for austenitization of the complete illuminated surface volume, the energy density needs to be increased.

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“…[4][5][6] Integrated mirrors, modulators, diffractive optic elements (DOEs), and special beam shaping lenses are commonly applied for laser processing to improve process efficiency. [7][8][9][10] For instance, laser beams with higher intensity values at the edge are able to generate a homogenous treated area. 11 Optimal power ratios between the center and edges of the laser beam profile can give uniform in-depth heat distributions.…”

Section: Introductionmentioning

confidence: 99%

Impact of laser beam oscillation strategies on surface treatment of microalloyed steel

Dewi

Volpp

2020

Journal of Laser Applications

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The depth homogeneity of laser-treated zones is one possible factor to define the quality and efficacy of altered mechanical properties in materials. For instance, half-rounded cross-sectional shapes of laser hardened zones using Gaussian beams provide dissimilar hardened depth in the edges and center of the treated area. This means that the in-depth distribution of compressive residual stress varies between the edges and the center of the hardened area. Nonhomogeneity of compressive residual stress distributions can inhibit fatigue properties and can lead to product failure. The utilization of oscillated laser beams has been proven to improve the welding efficiency and energy input distribution to the material, which promises achieving a homogeneous depth of laser-treated zones in hardening applications. Therefore, this work examines the influence of triangular, square, and circular beam oscillation strategies on the energy input distribution during the process and the geometry of the laser-treated zones on microalloyed steel. Laser beam pathways were assembled using a vector graphic editor to visualize the energy distribution from each oscillation strategy. Cross section images of the hardened tracks were taken and related to the thermal energy input profiles. It was revealed that each oscillation strategy demonstrates characteristic temporal and spatial thermal energy input distribution, influencing the geometry of the hardened zone. The circular oscillation strategy produced a widely constant depth in contrary to the triangular and square beam oscillation due to its characteristic energy distribution that allows homogeneous heat dissemination in the material. This confirms that the laser beam oscillation strategy can tailor the energy input distribution to optimize the processing outcome.

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Microstructure and mechanical properties of laser surface treated 44MnSiVS6 microalloyed steel

Cited by 18 publications

References 22 publications

Joining the High-Strength Steel Sheets Used in Car Body Production

Joining the High-Strength Steel Sheets Used in Car Body Production

Influence of complex geometries on the properties of laser-hardened surfaces

Impact of laser beam oscillation strategies on surface treatment of microalloyed steel

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