start-ver=1.4
cd-journal=joma
no-vol=16
cd-vols=
no-issue=2
article-no=
start-page=109
end-page=114
dt-received=
dt-revised=
dt-accepted=
dt-pub-year=2021
dt-pub=202110
dt-online=
en-article=
kn-article=
en-subject=
kn-subject=
en-title=
kn-title=Formation and Its Mechanism of High-speed Micro-grooving on Metal Surface by Angled CW Laser Irradiation
en-subtitle=
kn-subtitle=
en-abstract=
kn-abstract=In general, pulsed lasers with high peak power have been used for the micro-groove formation. However, the processing speed is limited by the pulse repetition rate. On the other hand, CW laser can be expected to perform the high-speed processing by continuous energy input. The mechanism of micro-groove formation by CW laser was investigated by high-speed observation and the thermal fluid analysis. In the perpendicular irradiation of CW laser, the molten metal flows symmetrically around the keyhole to the backward direction, and micro-grooves remain at both edges of molten region. In contrast, in the angled irradiation, the molten metal at the reflection-side scatters as spatters. The remained molten metal flows from the reflection-side to the incident-side through the bottom of keyhole, since the recoil pressure is generated from the reflection-side to the incident-side. In addition, high-speed scanning contributes to keeping the sufficient time and force to move the molten metal in the backward direction. Then, the micro-groove remains at the reflection-side, while the upheaval is formed at the incident-side by gathering the molten metal from the reflection-side and the front of keyhole. Asymmetrical behavior of molten metal flow in angled irradiation of CW laser can create micro-groove in the reflection-side. 
en-copyright=
kn-copyright=

en-aut-name=TauraNozomi
en-aut-sei=Taura
en-aut-mei=Nozomi
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=1
ORCID=

en-aut-name=MitsunobuAkiya
en-aut-sei=Mitsunobu
en-aut-mei=Akiya
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=2
ORCID=

en-aut-name=SakaiTatsuhiko
en-aut-sei=Sakai
en-aut-mei=Tatsuhiko
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=3
ORCID=

en-aut-name=OkamotoYasuhiro
en-aut-sei=Okamoto
en-aut-mei=Yasuhiro
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=4
ORCID=

en-aut-name=OkadaAkira
en-aut-sei=Okada
en-aut-mei=Akira
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=5
ORCID=

affil-num=1
en-affil=Graduate School of Natural Science and Technology, Okayama University, Japan
kn-affil=

affil-num=2
en-affil=Faculty of Engineering, Okayama University, Japan
kn-affil=

affil-num=3
en-affil=NIPPON STEEL CORPORATION, Japan
kn-affil=

affil-num=4
en-affil=Graduate School of Natural Science and Technology, Okayama University, Japan
kn-affil=

affil-num=5
en-affil=Graduate School of Natural Science and Technology, Okayama University, Japan
kn-affil=
en-keyword=CW laser
kn-keyword=CW laser
en-keyword=micro-groove
kn-keyword=micro-groove
en-keyword=high-speed scanning
kn-keyword=high-speed scanning
en-keyword=thermal fluid analysis
kn-keyword=thermal fluid analysis
en-keyword=high-speed observation
kn-keyword=high-speed observation
END