• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1999.05a
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• pp.21-26
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• 1999

In this study, to assess chip breaking characteristics of cold-drawn free machining steels, a newly developed non-dimensional parameter, chip breaking index, C/sub B/ has been adopted. And for comparison with free machining steels, chip breaking characteristics of conventional carbon steels were investigated. Properly controlled chips were produced with the C/sub B/ value of 0.05∼0.2, regardless of steel types. In case of cold-drawn free machining steels, however, cycle times of chip breaking are relatively shorter than those of conventional steels. And properly controlled chips were obtained from wider range of feed rate.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.10a
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• pp.245-251
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• 2004

This paper is studied on the effect of TiAlN coated Ball End Mill and MQL(Minimum Quantity Lubrication) cutting condition on cutting characteristic of high hardness steels. KP4 steels[HRC32] and STD11[HRC60] heat treated steels were used as the workpiece and WC-Co ball end mill and single and multi layer TiAlN coated ball end mill were utilized in the cutting tests. MQL device was used to spray botanical oil coolant. Result showed that TiAlN coated ball end mill were increased the cutting length than WC-Co ball end mill in the cutting speed[$245{\sim}320m/min$] about $2.3{\sim}5.7$ times for KP4 steels and about $2.5{\sim}4.3$ times far STD11 heat treated steels. The multi layer TiAlN coated ball end mill is good for KP4 steels than single layer coated.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10a
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• pp.245-250
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• 2003

This research conducted milling tests to study effects of cutting environment conditions of ball end mills on the characteristics of hard milling process. KP4 steels and STD11 heat treated steels were used as the workpiece and WC-Co ball end mill tools with TiAIN coated were utilized in the cutting tests. Dry cutting without coolant and semi-dry cutting using botanical oil coolant were conducted and MQL (Minimum Quantity Lubricant) device was used to spray coolant. Cutting forces, tool wear and surface roughness were measured in the cutting tests. Results showed that dry cutting of KP4 and hardened STD11 specimens produced better surface quality and wear performance than MQL spray cutting did.

• Journal of the Korean Society for Heat Treatment
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• v.14 no.2
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• pp.81-88
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• 2001

The effects of post-oxidation and sulfnitriding treatments on the phase transformation in the nitrided case of tool steels have been studied. Dense and compact $Fe_3O_4$ layer was formed at the outer surface of nitride compound layer by post-oxidation treatment and multi layer of iron sulfide(FeS) was formed in the compound layer by sulfnitriding treatment. The surface hardness decreased because of formation of the soft oxide or sulfide at the nitride surface. Diffusion layer of nitride case was not affected by post-oxidation treatment or sulfnitriding treatment of nitrided alloy tool steels.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.1078-1082
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• 1997

The use of CBN tool material has been greatil increased because of the superior metal cutting performance for the machining of hardened steels. This paper presents some experimental results on the ball endmilling of hardened steels. Three different hardnesses of STB-11 workpieces were machined using CBN ball endmills, and the machining charteristics including cutting forces, tool wear, and surface roughness of machined surface were compared. It has been found that the CBN ball endmill works better in the machining of harder workpieces. The microscopic examination explains that this unusual phenomenon is cause by the difference of microstructure of each workpieces.

• Transactions of Materials Processing
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• v.13 no.1
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• pp.45-52
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• 2004

This research conducted milling tests to study effects of cutting environment conditions of ball end mills on the characteristics of hard milling process. KP4 steels and STD11 heat treated steels were used as the workpiece and WC-Co ball end mill tools with TiAlN coated were utilized in the cutting tests. Dry cutting without coolant and semi-dry cutting using botanical oil coolant were conducted and MQL(Minimum Quantity Lubricant) device was used to spray coolant. Cutting forces, tool wear and surface roughness were measured in the cutting tests. Results showed that dry cutting of KP4 and hardened STD11 specimens produced better surface quality and wear performance than MQL spray cutting did.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.10a
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• pp.238-244
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• 2004

This research conducted milling tests to study effects of cutting environment conditions of ball end milts on the characteristics of high speed milling cutting process. KP4 steels and STD11 heat treated steels were used as the workpiece and WC-Co ball end mill tools with TiAIN coated were utilized in the cutting tests. Dry cutting without coolant and semidry cutting using botanical oil coolant by the MQL(Minimum Quantity Lubricant) device were conducted. Cutting forces, tool wear and surface roughness were measured in the cutting tests. Results showed that MQL spray cutting of KP4 and hardened STD11 specimens produced better surface quality and wear performance than dry cutting did.

• 연구논문집
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• s.33
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• pp.175-182
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• 2003

In this study, the wear resistance of the complex powder diffusion treated KS STD 61 has been investigatived. KS STD 61 tool steel was pretreated in quenching and tempering processes to obtain the tempered martensitic microstructure. The samples were packed with complex powder in steel pot($\Phi$90x60mm) and heated in a box furnace. the complex powder diffusion treatment are carried out at $540^{\circ}C$, $520^{\circ}C$, $500^{\circ}C$ for 40min, 1.5hr and 2.5hr. The microstructure, microhardness, wear resistance, and coating layer thickness of the complex powder diffusion treated samples were investigation. The weight loss of as heat treated sample was 0.4mg and that of the complex powder treated at $540^{\circ}C$ for 2.5hr was 0.17mg. These result means that the wear resistance of tool steels can be easily improved by the powder diffusion process at conventional tempering treatment temperature.

• International Journal of Precision Engineering and Manufacturing
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• v.9 no.4
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• pp.74-78
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• 2008

High-speed tool steels are extensively used in tooling industries for manufacturing cutting tools, forming tools, and rolls. Electrical discharge machining (EDM) has been found to be an effective process for machining these extremely hard and difficult-to-cut materials. Extensive research has been conducted to identify the optimum machining parameters for EDM with different tool steels. This paper presents a fundamental study of the surface characteristics of SKH-51 tool steel machined by micro-EDM, with particular focus on obtaining a better surface finish. An RC pulse generator was used to obtain a better surface finish as it produces fine discharge craters. The main operating parameters studied were the gap voltage and the capacitance while the resistance and other gap control parameters were kept constant. A negative tungsten electrode was used in this study. The micro-EDM performance was analyzed by atomic force microscopy to determine the average surface roughness and the distance between the highest peak and lowest valley. The topography of the machined surface was observed using a scanning electron microscope and a digital optical microscope.

• Transactions of the Korean Society of Mechanical Engineers
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• v.7 no.3
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• pp.319-327
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• 1983

The thermal diffusivity one of the series of standard pieces for spark test are determined by the flash method. The standard pieces are composed with carbon steels, structural carbon steels, alloy steels and high speed tool steels. In order to compute the thermal conductivity of the standard pieces, their specific heats are measured by a differential scanning calorimeter. The thermal conductivities are calculated from the data of specific heat, density and thermal diffusivity. To increase the accuracy of data for the thermal diffusivity by data reduction excursion method in the flash method, the governing heat diffusion equation, which is closely described experimental conditions with the finite pulse and the heat loss from the sample surfaces, is solved. In this analysis an integral transform is used.