• Design & Manufacturing
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• v.1 no.1
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• pp.23-26
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• 2007

This paper has comparatively analyzed the characteristics of the machined surface of a specimen made by machining Die Steel STD11 and a specimen obtained by W-EDM steel. If a press die is manufactured through W-EDM, products of shapes that cannot easily be made through machining can be manufactured easily. However, the life of the press die is significantly reduced compared with the press die made through machining. This is believed to be caused by the deformed layer that has occurred on the surface of the press die that was made through W-EDM. The roughness of the 2 specimens was measured, and it was learned that the distribution of the roughness of the specimen made through the 1st W-EDM was rough.

• 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.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.3 no.3
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• pp.17-23
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• 2004

The performance and life of a die are influenced by the machining methods. In order to examine the effects of machining methods on surface charactenstics, simple experiments are devised and performed. A die steel STD11, commonly used as a die material in press working, is selected. Three ways of machining methods to manufacture a die are considered. Those are (1) milling and then grinding, (2) wire-cut electric discharge dachining (W-EDM) and (3) heat treatment after W-EDM. The resulting surface roughnesses are measured. Also, the changes of surface microstructures are investigated using the scanning electron microscope(SEM) with energy dispersive X-ray spectrometer(EDS) and the results are discussed in details.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1898-1904
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• 2003

Laser heat treatment is an effective technique used to improve the tribological properties and also to increase the service life of automobile components such as camshafts, crankshatfs, lorry brake drums and gears. High power $CO_{2}$ lasers and Nd:YAG lasers are employed for localized hardening of materials and hence are of potential application in the automobile industries. The heat is conducted rapidly into the bulk of the specimen causing self-quenching to occur and the formation of matrensitic structure. In this investigation, the microstructrual features occurring in Nd:YAG laser hardening SM45C and $STD_{11}$ steel are discussed with the use of optical microscopic and scanning electron microscopic analysis. Moreover, This paper describes the optimisation of the processing parameters for maximum hardened depth of SM45C and $STD_{11}$ steel specimens of 10mm thickness by using CW Nd:YAG laser.

• 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.

• Journal of the Korean Vacuum Society
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• v.3 no.4
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• pp.449-456
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• 1994

산업용 주요 냉간금형 소재인 STD 11 강에 질소이온주입하여 이온조입조거에 따른 질화물형성 거동, 경도 및 내마모성 변화에 관해 연구하였다. XRD분석결과 90keV 에너지로 5$\times$1017 ions/cm2 조사 량 이상에서 Fe2N형태의 질화물이 형성되었으며 3$\times$1016 ions/cm2 범위의 모든 조사량에서 경도 및 조 사량에서 경도 및 내마모성 향상효과를 얻었다. Al2O3와의 ball-on-disc 마모거동 분석결과 STD 11모재 는 응착마모와 산화마모의 혼합형태로 마모되는 반면 질소이온주입한 경우 산화마모 경향이 강하게 나 타났다.

• Journal of the Korean Society for Heat Treatment
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• v.22 no.5
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• pp.282-289
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• 2009

The effects of the high temperature gas nitriding (HTGN), tempering and subzero treatment of STD11 steel have been investigated. HTGN treatment was carried out at $1050^{\circ}C$, $1100^{\circ}C$ and $1150^{\circ}C$ for 1 hr. in an atmosphere of $1\;kg/cm^2$ nitrogen gas. Tempering and double-tempering were performed at $550^{\circ}C$ for 1 hr. The surface layer of HTGN-treated steel appeared the precipitates of $M_2N$, $M_7C_3$ and $M_{23}C_6$ in the matrix of austenite. However, the interior region exhibited martensite with the precipitation of carbides. The nitrogen content of the surface layer appeared ~1.35 wt.%, ~0.83 wt.% and ~0.56 wt.% at the HTGN treatment temperature of $1050^{\circ}C$, $1100^{\circ}C$ and $1150^{\circ}C$, respectively. The surface hardness of double-tempered and subzero-treated steel measured the maximum value of 828 Hv, 960 Hv, 750 HV after HTGN treatment at the $1050^{\circ}C$, $1100^{\circ}C$ and $1150^{\circ}C$, respectively. These hardness value increased above 230~420 Hv compared with the HTGN-treated steel due to the decrease in retained austenite and existence of fine precipitates.

• 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 Heat Treatment
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• v.30 no.5
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• pp.215-221
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• 2017

The effect of austenitizing temperature on the degree of carbides re-solutionizing, mean graine size, hardness and the volume fraction of retaind austenite ($V_{\gamma}$) etc., has been studied by means of metallography, X-ray diffractometry and hardness measurement in STD 11 tool steel. As austenitizing temperature increases, the amount of alloying elements which is re-dissolved into matrix increases, resulting in increase of $V_{\gamma}$, due to the chemical stabilization of austenite. The Vickers hardness value decreases with increasing austenitizing temperature, which is attributed to grain size as well the volume fractions of $V_{\gamma}$ and carbides. Theoretical diffraction intensity of (200) ${\alpha}^{\prime}$, (211) ${\alpha}^{\prime}$ (200) ${\gamma}$ and (220) ${\gamma}$ peaks obtained by $CuK_{\alpha}$ chracteristics X-ray (${\lambda}=0.15429nm$) was calculated, and quantitative analysis of $V_{\gamma}$ could be carried out by X-ray diffraction method. The resultant value is well coincided with the value obtained by image analysis method. When the quenched specimen is tempered above $200{\sim}400^{\circ}C$ for 30 min, the transition carbides i.e., MC and $M_2C$ in the size of about 20 nm begin to precipitate at $300^{\circ}C$.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.8 no.6
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• pp.16-25
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• 1999

In recent years, grinding techniques for precision machining of brittle materials used in die, model and optical parts have been improved by using superfine abrasive wheel and precision grinding machine. The completion of optimum dressing of superfine abrasive wheel makes possible the effective precision grinding of die steel(STD-11). In this study, a new system and the grinding mechanism of optimum in-process electrolytic dressing were proposed. This method can carry out optimum in-process electrolytic dressing of superfine abrasive wheel. Therefore, the optimum in-process electrolytic dressing is a good method to obtain the efficiency and mirror-like grinding of STD-11.