The Spectral Emissivities of Iron, Nickel and Cobalt

Lund, Hannu; Ward, L.

doi:10.1088/0370-1301/65/7/309

Cited by 10 publications

(5 citation statements)

References 12 publications

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“…Iron exhibits relatively high absorptivity values decreasing monotonously with wavelength, as shown in Figure 5a. For wavelengths λ < 1.55 µm, the absorptivity values at the solid state are consistently larger than those at the liquid state, which is in accordance with the literature values of the X-point wavelength λ X, Fe of iron of λ X, Fe ≈ 1.55 µm, suggesting a stable welding process for the wavelength regime under investigation [72,77]. The corresponding PSC of iron, as shown in Figure 6a, shows almost constant values around 1.3 along the whole wavelength range under consideration, which are low compared to the value of copper at the wavelength region λ ≤ 575 nm, but still twice as high compared to the value of copper at ~1 µm.…”

Section: Comparison With the Process Stability Criterion Of Iron And ...supporting

confidence: 90%

“…Therefore, the relative size of the theoretical process window size ∆E rel increases and so the process becomes more stable, making the X-point the decisive turning point for process stability. This is valid as the change in absorptivity with temperature ∂A ∂T exhibits only a low variation with temperature, apart from small fluctuations in the short wavelength region due to interband transitions that lead to narrow absorptivity peaks which broaden and typically disappear rapidly with increasing temperature [18,36,77].…”

Section: Process Stability Criterionmentioning

confidence: 98%

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Why Color Matters—Proposing a Quantitative Stability Criterion for Laser Beam Processing of Metals Based on Their Fundamental Optical Properties

Kohl

Kaufmann

Schmidt

2022

Metals

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With its excellent automation capability and localized energy input enabling precise, reproducible welds, laser beam welding represents a preferred industrial joining technology. Electro-mobility drastically increases the need for defect-free and automatable copper joining technologies. However, copper welds that are produced with state-of-the-art infrared lasers often suffer from spattering and porosity. Recent publications show distinct improvements using novel beam sources at visible wavelengths, attributing them to increased absorptivity. Nevertheless, this cannot fully explain the steadier process behavior. This wavelength-dependent process stability has not yet been investigated sufficiently. Therefore, we have developed a predictive material-dependent criterion indicating process stability based on the example of copper heat-conduction spot welding. For this purpose, we combined energy balances with thermo-physical material properties, taking into account the wavelength and temperature dependence of the optical properties. This paper presents the key mechanism that we identified as decisive for process stability. The criterion revealed that X-points (unique, material-specific wavelengths) represent critical stability indicators. Our calculations agree very well with experimental results on copper, steel and aluminum using two different wavelengths and demonstrate the decisive, material-dependent wavelength impact on process stability. This knowledge will help guide manufacturers and users to choose and develop beam sources that are tailored to the material being processed.

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Section: Comparison With the Process Stability Criterion Of Iron And ...supporting

confidence: 90%

Section: Process Stability Criterionmentioning

confidence: 98%

Why Color Matters—Proposing a Quantitative Stability Criterion for Laser Beam Processing of Metals Based on Their Fundamental Optical Properties

Kohl

Kaufmann

Schmidt

2022

Metals

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“…460 [24]. 500 [20], 508 [25], 540 [ 171 1 430 [*] 1000 to 1 500 [26], 1600 [27] 1400 [27], 1 500 [28] 1 500 [28], 2 500 [29] 1 200 [*I, 2 500 [30] 700 to 750 [31], 850[*], 950 [30], 1200 [21] 1 loo[*], 1 300 [32], 1400 [33] 1 450 [*I 1 600 It can be seen that i . , points have been measured for solid and molten noble metals since at least 1912 [17] and for solid transition metals since 1919 [18].…”

Section: 3 Spectral Emissivity As a Function Of Wavelengthmentioning

confidence: 99%

Emissivity X Points in Solid and Liquid Refractory Transition Metals

1992

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The spectral emissivities of refractory transition metals have been measured from about 2 500 K up to temperatures above the melting point T,. The experimental method adopted is based on multiwavelength pyrometric measurements, where the determination of the spectral emissivity is implicitly related to the evaluation of temperature through the radiation emission law and an assumed relationship between the spectral emissivity E and the wavelength i.. Heating was produced with a pulsed laser in times of order looms. A specially constructed pyrometer was used which enabled measurements at six different wavelengths to be carried out at time intervals of order 0,l ms. A model for the evaluation of temperature and spectral emissivities has been developed and its limitations arising from statistical and systematic errors are discussed. Our experiments on the refractory transition metals Hf, MO, Nb, Re, Rh, Ta, W, V and Zr: (i) confirm the existence of a unique wavelength, i.,, for each metal (already well established in the solid state where &Jd;.ZO) to which different &,-isotherms converge for i<&, from which they diverge for j.>iX and at which E~ is independent of T, and thus equal, in particular, to its value at T,; (ii) indicate that R, is preserved through T,; and (iii) reveal that at T, these metals are effectively "grey". i.e. their emissivity, within the measurement uncertainty, is independent of i . (?ci;?i=0).

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“…Davis and Barker [293] [315] shows that the tensile strength of 99 Foley [317] reported that the tensile strength of nickel increased with decreasing temperature, from 65,000 psi at room temperature to 97,500 psi at -120°C. Additional data at temperatures down to -320°F are given by International Nickel [86].…”

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confidence: 99%

Nickel and its alloys

Rosenberg¹

1968

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The Spectral Emissivities of Iron, Nickel and Cobalt

Cited by 10 publications

References 12 publications

Why Color Matters—Proposing a Quantitative Stability Criterion for Laser Beam Processing of Metals Based on Their Fundamental Optical Properties

Why Color Matters—Proposing a Quantitative Stability Criterion for Laser Beam Processing of Metals Based on Their Fundamental Optical Properties

Emissivity X Points in Solid and Liquid Refractory Transition Metals

Nickel and its alloys

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