• International Journal of Precision Engineering and Manufacturing
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• v.3 no.1
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• pp.26-32
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• 2002

Laser direct patterning of the coated photoresist (PMER-NSG31B) layer was studied to make halftone dots on the gravure printing roll. The selective laser hardening of the photoresist by Ar-ion laser(wavelength: 333.6∼363.8 nm) was controlled by the A/O modulator. The coating thickness in the range of 5∼11㎛ could be obtained by using the up-down directional moving device along the vertically located roll. The width, thickness and hardness of the hardened lines farmed under the laser power of 200∼260mW and irradiation time of 4.4∼6.6 $\mu$ sec/point were investigated after developing. The hardened width increased as the coating thickness increased. Though the hardened thickness was changed due to the effect of the developing solution, the hardened layer showed good resistance to the scratching of 2H pencil. Also, the hardened minimum line width of 10㎛ could be obtained. The change of line width was also found after etching, and the minimum line widths of 6㎛ could be obtained. The hardened lines showed the good resistance to the etching solution. Finally, the experimental data could be applied to make gravure halftone dots using the developed imaging process, successfully.

• Laser Solutions
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• v.3 no.2
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• pp.35-43
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• 2000

Laser direct patterning of the coated photoresit (PMER-NSG31B) layer was studied to make halftone dots on gravure printing roll. The selective laser hardening of photoresist by Ar-ion laser(wavelength : 333.6nm∼363.8nm) was controlled by the A/O modulator. The coating thickness in the range of 5㎛∼11㎛ could be obtained by using the up-down directional moving device along the vertically located roll. The width, thickness and hardness of the hardened lines formed under laser power of 200∼260㎽ and irradiation time of 4.4∼6.6$\mu$ sec/point were investigated after developing. The hardened width increased according to the increase of coating thickness. Though the hardened thickness was changed due to the effect of the developing solution, the hardened layer showed good resistance to the scratching of 2H pencil. Also, the hardened minimum line widths of 10㎛ could be obtained. The change of line width was also found after etching, and the minimum line widths of 6㎛ could be obtained. The hardened lines showed the good resistance to the etching solution. Finally, the experimental data could be applied to make gravure halftone dots using the developed imaging process, successfully.

• Journal of Institute of Control, Robotics and Systems
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• v.9 no.12
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• pp.1048-1054
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• 2003

In laser surface hardening processes, the geometrical parameters such as the depth and the width of a hardened layer can be utilized to assess the hardened layer quality. However, accurate monitoring of the geometrical parameters for on-line process control as well as for on-line quality evaluation is very difficult because the hardened layer is formed beneath a material surface and is not visible. Therefore, temperature monitoring of a point of specimen surface has most frequently been used as a process monitoring method. But, a hardened layer depends on the temperature distribution and the thermal history of a specimen during laser surface hardening processing. So, this paper describes the estimation results of the geometric parameters using multi-point surface temperature monitoring. A series of hardening experiments were performed to find the relationships between the geometric parameters and the measured temperature. Estimation results using a neural network show the enhanced effectiveness of multi-point surface temperature monitoring compared to one-point monitoring.

• Journal of the Korean Society for Heat Treatment
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• v.6 no.4
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• pp.230-236
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• 1993

The laser beam hardening has been experimentally tried to find the hardened characteristics of STD11. Experiment was performed on the optimum hardening condition with 2kW $CO_2$ laser. The microstructure of the hardened layers was observed using the microscope. The hardened zones exhibits very high Vickers microhardness of 720 Hv, however, the deoxidation was observed under the surface of hardened area. The case depth of hardened zones is about 0.6mrn and case width is 4mm. FEM-simulation on laser surface hardening of STD11 steel are described. With the proper assumption of the absorbed energy density, the calculated case depth and width in 2 kW $CO_2$ laser hardening were in good agreement with the experimental result. It was found that there is optimum absorbed energy density of STD11.

• Tribology and Lubricants
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• v.20 no.1
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• pp.7-13
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• 2004

High strength steels are widely used as tribo-materials in the field. Previous study revealed that for mild steel, the states of strain on the worn surface measured by X-ray diffraction has a good relationship with the state of wear. The objective of this study is to identify the relationship between the state of strain on the worn surface and the state of wear in high strength steels. Sliding wear tests were carried out using several hardened steels. X-ray diffraction tests were conducted to analyze the state of strain on the worn surface during wear. The experimental results indicated that the state of strain on worn surface in the hardened steel shows the same tendency as in the mild steel. It is clear that change of half value width on the worn surface as a function of sliding speeds is broadly similar in shape to wear characteristics curve and its magnitude has a good relationship with the wear rate at two different wear modes in the hardened steel.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.10 no.5
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• pp.25-30
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• 2001

The purpose of this investigation is experimentally to clarify the machinability and optimum tool geometry on milling of hardened STD11 steel. In the finish process office milling of high hardened STD11 steel by CBN tool, the optimum tool shape is suggested, which can minimize the tool fracture and chipping by impact. It is measured that cutting farce, tool wear and surface roughness generated during single-insert face milling using various geometric CBN tools. It has been found that the optimal chamfer angle of CBN tool is about -$25^{\circ}C$ and the suitable chandler width is 0.2mm. The nose radius of tool is the most excellent at 1.2mm in the viewpoint of tool wear and surface roughness.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.11
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• pp.191-198
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• 2000

Laser direct patterning of the coated photoresist (PMER-NSG31B) layer was studied to make halftone dots on gravure printing roll. The selective laser hardening of photoresist by Ar-ion laser(wavelength: 333.6~363.8nm) was controlled by the A/O modulator. The coating thickness in the range of 5~11$\mu m$ could be obtained by using the up-down directional moving device along the vertically located roll. The width, thickness and hardness of the hardened lines formed under the laser power of 200~260㎽ and irradiation time of 4.4~6.6 $\mu$sec/point were investigated after developing. The hardened width increased as the coating thickness increased. Though the hardened thickness was changed due to the effect of the developing solution, the hardened layer showed good resistance to the scratching of 2H pencil. Also, the hardened minimum line widths of 10$\mu m$ could be obtained. The change of line width was also found after etching, and the minimum line widths of 6$\mu m$ could be obtained. The hardened lines showed the good resistance to the etching solution. Finally, the experimental data could be applied to make gravure halftone dots using the developed imaging process, successfully.

• Laser Solutions
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• v.18 no.2
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• pp.1-4
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• 2015

This study is related to the surface hardening treatment to spheroidal graphite cast iron for die by using high power diode laser. Laser device used in this experiment is capable of real-time laser power control. This is because the infrared temperature sensor (two color pyrometer) attached to the optical system measures the surface temperature of specimen and adjusts the laser power in real time. The surface treatment was carried out with the change of heat treatment temperature at the beam travel speed 3 mm/sec. Hardened width and depth was measured and hardened zone was analyzed by micro vickers hardness test in order to research the optimum condition of heat treatment. The changes in microstructure of the hardened zone also was examined. As a result of hardness measurement and observations on microstructure of hardened zone, hardness increased over three times as compared with base metal because the martensite was formed on the matrix structure.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.921-924
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• 1995

Case hardening behavior of carbon tool steel(SK5) was investigated after pulsed YAG laser irradiation. In the case od beam passes,martensite formed in the melt zone and in former pearlite regions of the austenitization zone exhibits vary high Vickers hardness values. The molten depth and width decrease as the beam power density increase. The influence of depth and width of color painted specimen was also investigated. The molten zone of the black painted specimen was the largest. The were loss of the black painted specimen was smaller than any other painted or raw material.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.6
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• pp.112-119
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• 1995

Early fracture and cutting force of ceramic tool for hardened STC3 steel was investigated in this study. It was found that early fracture of ceramic tool was mostly occurred before normal wear was progressed beyond a critical cutting speed and normal wear was performed under the critical cutting speed. The relationships among critical cutting speed, which was a cause of early fracture, suggested cutting cross section, that is, maximum thickness of cut and width of cut, and cutting force were examined. The following conclusions were obtained: (1)Critical cutting speed showed a high value in the case of small maximum thickness of cut and large nose radius, but was not influenced by width of cut, (2)Principal, feed and radial force, respectively, showed the proportional value to constant cutting area, width of cut and maximum thickness of cut orderly, (3)Occurrence of early fracture was dependent upon radial force.