High temperature cracking in weldments.

Homma, Hiroyuki

doi:10.2207/qjjws1943.57.496

Cited by 7 publications

(4 citation statements)

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“…The specimen without B has a small eutectic region, as shown in Fig. 9(a); therefore, the formation mechanism of cracks in the present process is similar to that reported by S. Kou 28) and Homma et al 34) The boron-added specimens have a large eutectic region, as shown in Figs. 9(b), (c), and (d).…”

Section: Discussionsupporting

confidence: 87%

“…As shown in Figs. 9(b), (c), (d), the microstructures with fine and complex structures, which have a low dendrite arm width and a wide gap between the secondary dendrite arms, are similar to those observed in the small cracks reported by Senda et al 33) Kou 28) and Homma et al 34) reported that the liquid phase can be fed into the initial cracks immediately and that cracks can be healed during the start of the solidification stage. However, in the final stage, the liquid feed was insufficient, and cracks occurred at the liquid film interface.…”

Section: Discussionsupporting

confidence: 79%

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Suppression of Solidification Defects in Partial Non-Magnetization Improvement for Silicon Steel

Hamada,

Horikawa,

Mitarai

et al. 2023

Mater. Trans.

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Leakage flux in rotor core bridges is a problem specific to interior permanent-magnet (IPM) motors. It is widely known that the partial nonmagnetization of bridges reduces the magnetic flux leakage. In a previous study, a process was proposed whereby a part of the silicon steel sheet that bridges after pressing was non-magnetized by melting and mixing Ni-Cr alloy powder with a silicon steel sheet using a laser, and the rotor core was produced by laminating them. However, because the final solidification part had solidification defects, such as cracks and shrinkage cavity, the process was proposed to leave a homogenous part free of solidification defects. Therefore, the area of the improved portion increased. We focused on developing a new alloy for non-magnetic improvement to suppress solidification defects. The improved portion was melted and mixed using a laser with various B contents to obtain a composition of Fe-(15-20) mass%Ni-(15-20) mass%Cr-(2-3) mass%Si-(0-1.6) mass%B. Large cracks and large shrinkage cavity were observed in the boron-free alloy. The cracks and shrinkage cavity decreased with an increase in the B content. The minimization of the area of non-magnetic improvement is possible by suppressing solidification defects. Consequently, the laser processing speed per piece and the amount of expensive nickel were reduced. These new alloys show promise for practical applications in the partial non-magnetization process.

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Section: Discussionsupporting

confidence: 87%

Section: Discussionsupporting

confidence: 79%

Suppression of Solidification Defects in Partial Non-Magnetization Improvement for Silicon Steel

Hamada,

Horikawa,

Mitarai

et al. 2023

Mater. Trans.

View full text Add to dashboard Cite

show abstract

“…However, in the final stage, the liquid feeding is insufficient, and cracks occur at the liquid film interface. Sample C has a small eutectic region; therefore, the formation mechanism of cracks in the present process is similar to that reported by Homma et al 33) As mentioned above, in order to reduce cracks, it may be necessary for the microstructure of partial non-magnetic improvement to be complex and in sync with the increment of the eutectic region as suggested by Senda et al 32)…”

Section: Discussionsupporting

confidence: 82%

“…A typical solidification crack is shown along the primary crystal in the mushy zone. Homma et al 33) reported that the liquid phase can be fed into initial cracks immediately and that cracks can be healed during the start of the solidification stage. However, in the final stage, the liquid feeding is insufficient, and cracks occur at the liquid film interface.…”

Section: Discussionmentioning

confidence: 99%

Development of Rotor Core with High Magnetic Flux by Partial Non-Magnetic Improvement of Silicon Steel

Hamada

Watarai²,

Mitarai

et al. 2023

Mater. Trans.

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Flux leakage in the rotor core bridges is a problem specific to interior permanent magnet motors and has been unsolved till date. It is widely known that if the bridges are partially non-magnetically improved with low magnetic polarization, the leakage flux will be smaller, and the rotor will have a higher magnetic flux. We proposed that the portion of the silicon steel sheets that becomes the bridge after pressing can be nonmagnetized and laminated to fabricate the rotor core. Partially non-magnetic material with a polarization of almost zero was obtained by melting and mixing NiCr alloy powder with the silicon steel sheets. This non-magnetic improvement treatment was applied to the bridge in the rotor core sheet, in which the non-magnetic area width was 1.45 mm, and the prototype rotor core was fabricated by laminating 60 rotor core sheets. Upon measurement, the rotor core showed approximately 35% higher magnetic flux than a conventional one, with the actual value nearly identical to that obtained from the magnetic field analysis.

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Microstructure and mechanical properties of additively manufactured CoCrW alloy using laser metal deposition

et al. 2020

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High temperature cracking in weldments.

Cited by 7 publications

References 0 publications

Suppression of Solidification Defects in Partial Non-Magnetization Improvement for Silicon Steel

Suppression of Solidification Defects in Partial Non-Magnetization Improvement for Silicon Steel

Development of Rotor Core with High Magnetic Flux by Partial Non-Magnetic Improvement of Silicon Steel

Microstructure and mechanical properties of additively manufactured CoCrW alloy using laser metal deposition

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