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Volume 28, Issue 11
Displaying 1-11 of 11 articles from this issue
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Mitsuo MAEDA2000 Volume 28 Issue 11 Pages 727
Published: November 15, 2000
Released on J-STAGE: March 17, 2010
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Tomoo FUJIOKA2000 Volume 28 Issue 11 Pages 728
Published: November 15, 2000
Released on J-STAGE: March 17, 2010
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Keiichi KUBOTA, Kunihiko WASHIO2000 Volume 28 Issue 11 Pages 729-735
Published: November 15, 2000
Released on J-STAGE: March 17, 2010
JOURNAL FREE ACCESSHigher power YAG laser systems have been expected to realize novel applications of high-precision welding and cutting with flexible and clean processes for car industries and heavy-section industries etc. However, the output power of YAG laser is limited by the thermal effects of laser rods at the high power pumping. Recently high power technologies of lamp pumped YAG laser have been developed to realize 10 kW output power commercial laser with a good beam quality, by improving cavity modules performance and using cascade arrangement or MOPA technologies. The LD-pumped YAG laser is much superior to the lamp-pumped YAG laser from the viewpoint of the plug efficiency, beam quality, maintenance-free and etc. Owingto the rapid progress in high power LD pumping technologies, 2 kW LD-pumped YAG laser with an excellent beam quality of 50 mm·mrad has been already commercialized domestically and the higher output power LD-pumped laser has been further developed.View full abstractDownload PDF (1396K) -
Muneharu KUTSUNA2000 Volume 28 Issue 11 Pages 736-744
Published: November 15, 2000
Released on J-STAGE: March 17, 2010
JOURNAL FREE ACCESSRecently, high power laser diode (more than 100W), LD pumped YAG (more than 4kW), 10kW lamp pumped YAG laser and 10kW chemical oxygen-iodine laser (COIL) have been developed in the industrialized countries such as Germany, United States and Japan, which had their own big national projects. As a result of large numbers of research and developments, the modern laser materials processing has been realized and used in all kinds of industries now. At the end of 20th century, the price of laser diode has become lower and competitive to the conventional lasers. Lower the price of laser systems, wider is the field of their applications. In the present paper, the research and developments of laser materials processing in US, EU and Japan are outlined as a review.View full abstractDownload PDF (4077K) -
Relationship between Shielding Gas and Porosity FormationAkira MATSUNAWA, Naoki SETO, Seiji KATAYAMA2000 Volume 28 Issue 11 Pages 745-749
Published: November 15, 2000
Released on J-STAGE: March 17, 2010
JOURNAL FREE ACCESSIn higher power CW laser welding more than 5 kW, a serious imperfection so called porosity or gas pores are always formed and this fact hinders the industrial application of laser welding of thicker plates. The present authors have conducted systematic studies on keyhole and molten pool dynamics using a special X-ray transmission imaging apparatus and have revealed that the porosity formation is caused by the instability of keyhole. One of the most effective measures to suppress porosity formation is to use the pulse modulated laser under the adequate frequency and duty cycle. But no pulsed CO2 laser is available in the power range over 20 kW. The authors have found that porosity is perfectly suppressed or greatly reduced when pure nitrogen gas is used as the shielding gas, but its mechanism has been unknown. However, by the simultaneous observation of keyhole by X-ray method and laser induced plasma with a sufficient temporal resolution, it hasbeen revealed that nitrogen plasma is intermittently formed and the keyhole disappears while nitrogen plasmais formed. Namely, by the plasma and laser beam interaction, the keyhole dynamics is similar to that of modulated pulse laser welding and this leads to the suppression of porosity.View full abstractDownload PDF (1645K) -
2000 Volume 28 Issue 11 Pages 749-749,759
Published: November 15, 2000
Released on J-STAGE: March 17, 2010
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Takashi ISHIDE, Shuho TSUBOTA, Michisuke NAYAMA, Yoshiaki SHIMOKUSU, K ...2000 Volume 28 Issue 11 Pages 750-754
Published: November 15, 2000
Released on J-STAGE: March 17, 2010
JOURNAL FREE ACCESSThis paper reviews techniques to apply the laser welding to heavy components. Especially high power CO2 laser applications in this area which include ship building and bridge building industry and high power YAG laser welding in the nuclear power plants are dealt with. In addition, future lasers for processing in heavy components are discussed.View full abstractDownload PDF (1741K) -
Kozo YASUDA, Mikio MURO2000 Volume 28 Issue 11 Pages 755-759
Published: November 15, 2000
Released on J-STAGE: March 17, 2010
JOURNAL FREE ACCESSThis work describes a chemical oxygen iodine laser (COIL) equipment and its application for material processing of cutting and welding. The COIL is capable of delivering high-power output. The shortwavelength (1315 nm) is suitable for the transmission using optical fibers with excellent beam quality. These characteristics make COIL a candidate for a variety of industrial applications in cutting and welding. A cutting application in decommissioning of nuclear reactors is one purpose of high power COIL system and a welding application in heavy industries of thick material is another purpose. The most important key requirement for an industrial laser is low operating cost. At this point of view there are many kinds of problemsto be solved for industrial application of COIL.View full abstractDownload PDF (1026K) -
Katsuhiro MINAMIDA2000 Volume 28 Issue 11 Pages 760-764
Published: November 15, 2000
Released on J-STAGE: March 17, 2010
JOURNAL FREE ACCESSThe full-scale use of lasers in the steel industry began nearly 23 years ago with their applications as controllable light sources. Its contribution to the increase in efficiency and quality of the steel making process has been important and brought us the saving of the energy, the resource and the labor. Laser applications in the steel making process generally require high input energy, so it is essential to consider the interaction between the laser beam and the irradiated material. We have developed plenty of new high-power-laser applications for the steel making process with their considerations in mind. A review of the following high-power-laser applications is given in the present paper: (1) Wedge shape welding with multiple reflecting effectof CO2 laser beam, (2) Butt welding of extra thin steel sheets by ripple mode Nd-YAG laser, (3) Developed laser flying welder connect hot bars of around 1100 °C for continuous hot rolling mill using two 45 kW CO2 lasers.View full abstractDownload PDF (771K) -
Yoshihiro YAMAUCHI, Keishin OTA, Yuji KAWAKAMI, Eiichi OZAWA2000 Volume 28 Issue 11 Pages 765-768
Published: November 15, 2000
Released on J-STAGE: March 17, 2010
JOURNAL FREE ACCESSGeneration fields in a laser ablation system for synthesizing ultra-fine particles in He gas were dynamically visualized by using a scatterplate interferometer, which was designed for in-situ and real-time observation of gas density and furthermore temperature distribution. The observed time-variation of the generation field's gas density distribution, which relates to the gas temperature distribution, shows that the Hegas temperature does not exactly correspond to the ablation laser shots, there exists a time constant which leads to the He gas slowly being heated up and cooling off between laser shots. Since the diameter distribution ofthe synthesized nano particles is sensitive to the ambient gas temperature, real-time observation of the gas temperature variation will be useful for controlling the particle properties.View full abstractDownload PDF (1163K) -
Fumitaka MURASE, Masahiro UEDA, Katsuhiko ASADA, Toshiro MATSUMOTO, Ka ...2000 Volume 28 Issue 11 Pages 769-771
Published: November 15, 2000
Released on J-STAGE: March 17, 2010
JOURNAL FREE ACCESSAn optical system has been developed for measuring the thickness and width of polyethylene sheet and the size of a rib on the sheet surface, in real time. The system is simple and consists of a sensor head including laser and silicon photodiode, a scanning system for the polyethylene sheet, and a data processing system. The precision of the measurement is about 1/100 mm and the time required for the measurement is about 120 seconds.View full abstractDownload PDF (758K)
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