• 열처리공학회지
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• 제30권1호
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• pp.17-20
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• 2017

Mechanical properties of STD61 steel are compared with those of carburized STD61 steel when both are quenched and tempered in vacuum heat treatment. Mechanical properties of carburized STD61 steel are improved better than STD61 steel in hardness, tensile strength, impact energy and wear resistance.

• 열처리공학회지
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• 제14권1호
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• pp.27-34
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• 2001

The effects of pre-heat treatment(Q/T) on microstructure and hardness of STD11 and STD61 tool steel nitrided by micro-pulse plasma were investigated. The quenching temperature for obtaining matrix hardness of STD11 and STD61 steel on range of HRC 50 to HRC 60 desired for machine parts is about $1070^{\circ}C$ and $1020^{\circ}C$ respectively. The hardness of STD11 and STD61 quenched at the temperature was HRC 63 and HRC 56 respectively. The nitrided case depth of STD11 and STD61 nitrided at $550^{\circ}C$ for 5 hours was independent of pre-heat treatment condition and the depth was approximately $100{\mu}m$. However, hardness and compactness of nitrided layer on Q/T treated specimen were higher than the annealed specimen. The case depth increased linearly with the increase of nitriding temperature, however, the hardness of nitrided layer decreased with the increase of temperature. Phase mixture of ${\gamma}-Fe_4N$ and ${\varepsilon}-Fe_{2-3}N$ was detected by XRD analysis in the nitrided layer formed at the optimum nitriding condition. The optimum nitriding temperature was approximately $490^{\circ}C$ which was $10^{\circ}C$ lower than the tempering temperature for preventing softening behavior of STD11 and STD61 matrix during nitriding process and the surface hardness of nitrided layer obtained by optimum pre-heat treatment condition was about Hv1400.

• 대한기계학회논문집A
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• 제38권4호
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• pp.427-436
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• 2014

이 연구에서는 STD61 열간금형강 상부에 생성되는 하드페이싱층에 적합한 하드페이싱 재료와 두께를 3 차원 비정상 열전달 및 열응력 해석을 통하여 예측하고자 한다. Stellite6, Stellite21과 19-9DL 초합금을 하드페이싱 재료로 적용하였다. 하드페이싱 재료와 두께가 하드페이싱된 시편 내부 온도, 열응력 및 변형률 분포 변화에 미치는 영향에 대하여 분석하였다. 이 결과로부터 큰 열전도도를 가지는 재료로 얇은 하드페이싱 층을 생성하는 것이 열전달 특성 측면에서는 효과적인 것을 알 수 있었다. 또한, Stellite21 초합금으로 2 mm 두께의 하드페이싱부를 STD61 열간 금형강 상부에 생성할 경우, 하드페이싱부와 기저부의 경계부에서 유효응력 및 주변형률 편차가 최소화됨을 알 수 있었다. 이 결과들로부터 STD61 열간금형강에 적합한 하드페이싱 재료와 두께를 예측할 수 있었다.

• 열처리공학회지
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• 제6권2호
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• pp.59-69
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• 1993

Bending fracture strength test and impact strength test were made for VC coated die steels treated by immersing in molten borax bath and for hardened steels which were quenched and tempered, in order to clarify the effect of VC coating at $1000^{\circ}C$. The material used in this investigation was representative cold and hot work die steels STD11, STD61. The results obtained are as follows. 1) The bending fracture strength of VC coated die steel (STD11, STD61) was lessened with increasing the thickness of the VC coated layer. 2) With increasing the immersing time (imcreasing the thickness of the VC coated layer) the maximum hardness was obtained at 480 minutes holding, after that holding time hardness was decreased. 3) The impact strength of the VC coated die steel was not decreased. In the casse of STD11, it was higher than that of the quenched condition especially at low tempering temperature, and vice versa at high tempering temperature. However in the case of STD61 shows the result to the contrary.

• 한국표면공학회지
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• 제43권6호
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• pp.260-265
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• 2010

STD 61 steel has been widely used for tools, metallic mold and die for press working because of its favorable mechanical properties such as high toughness, and creep strength as well as excellent oxidation resistance. The STD 61 tool steel coated with TiN and ZrN by sputtering results in improvement of wear and corrosion resistance. In this study, surface characteristics of TiN and ZrN film coated STD 61 by sputtering were studied by using FE-SEM, EDS, XRD, and XRR and nanoindentation tests. From the results of surface characteristics of coated specimen, the ZrN coated surface showed finer granular than that of TiN coated surface. The coated layer structures of ZrN and TiN were grown to (111) and (200) preferred orientation. From the results of XRR test for surface roughness, density and growth rate of coating film, surface roughness and growth rate of ZrN coated film revealed lower values those of TiN coated film, whereas density of ZrN coated film showed higher values than that of TiN coated film. From the nanohardness and elastic modulus test, nanohardness value and elastic modulus of ZrN coated film became higher than those of TiN coated film.

• 연구논문집
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• 통권26호
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• pp.121-132
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• 1996

The carburising surface modification treatment of the die steel has been used for improving wear resistance and heat cycle strength of the die and preventing a pitting on the surface because the carbides are forming in the matrix during carburising. Generally, the hot forging die was used after quenching-tempering treatment or nitriding after quenching-tempering treatment. The nitriding after carburising on the surface of a hot die steel and a wear resistance die steels was suggested by SOUCHARD, JACQUOT. and BUVRON. This surface modification treatment improved the adhesive and abrasive wear resistance and friction coefficient. The process was introduced to the forging die of stainless steel, titanium alloy steel, alloy and medium carbon steel and the physical properties of the die after the treatment were improved. The surface hardening treatment of the nitriding, the carburising, the boriding, and TD process were used to improved the life time of the forging die. Also, the coating process of PVD, CVD and PCVD were used and the hard chromium plating was occasionally used. Therefore, this study analyzed the effects of the carburising time and the conditions of nitriding on STD61 steel. The case depth, the surface hardness, the forming carbide size and shape during overcarburising process on the die steel were also examined.

• 열처리공학회지
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• 제9권2호
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• pp.130-138
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• 1996

It has been investigated that the ion nitriding effects of a STD61 steel in various time conditions of 3 to 9 hours, and the microstructure of compound and diffusion layers of the ion nitrided specimen for 6 hours and subsequently reheated for 1 hour at various temperatures of $400{\sim}800^{\circ}C$ As the nitriding time increased, the thickness of compound and diffusion layers was increased, but the hardness of surface was not considerably increased (Max Hv=1045 at 9hrs). Some of the nitrogen was denitrided out of the surfac and diffused into the core, and also the oxides ($Fe_3O_4$, $Fe_2O_3$) were formed on the surface of the specimen during reheating. The compound layer was partially decomposed at about $600^{\circ}C$ but the diffusion layer was increased up to $800^{\circ}C$. With increasing reheated temperture, the hardness of the surface was decreased, whereas the hardness depth of diffusion layer (0.25mm) was increased up to $600^{\circ}C$ more than that of ion nitrided (0.18mm). The blend-heat treated STD61 steel by ion nitriding is therefore expected to hold on the characteristics of ion nitriding up to $600^{\circ}C$.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.711-714
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• 2002

Although recent research of metallic materials in high temperature fatigue have been much accomplished, many studies about brittle material as a die steel in high temperature fatigue does not have been reported. Especially, the study on the fatigue behavior over the transformation temperature is not studied sufficiently because of its difficult analysis and experiment. Therefore, reliable results of brittle material in high temperature fatigue behavior are needed. In this paper, stress-strain curves and stress-life curves in die STD61 steel at 700 and 900 are carefully examined, as the basic experimental data are used to predict from fatigue life over 700.

• 열처리공학회지
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• 제13권4호
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• pp.217-223
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• 2000

The boronizing effects of STD 61 steel have been studied on the micro structure and hardness. The STD 61 Steel was soaked in molten salt, consisted of KCl, $BaCl_2$, NaF, $B_2O_3$, FeB, and Ce, at various temperatures and times. The boronizing conditions for the peak hardness were the temperature range of $900^{\circ}C$ to $950^{\circ}C$ for 5 hr and that of $1000^{\circ}C$ for 3 hr, respectively. Four boride layers such as FeB, $Fe_2B$, ${\alpha}$ and matrix layer surface were observed from the microscopic surface examination. The thickness of boride layer was increased by increasing the boronizing time and the temperature. The structure of boride layer was tooth shape.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2011년도 춘계학술대회 및 Fine pattern PCB 표면 처리 기술 워크샵
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• pp.103-103
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• 2011

본 연구에서는 TiN/ZrN 복합층을 STD 61 공구강 표면에 마그네트론 스퍼터링 (magnetron sputtering) 방법을 이용하여, 표면온도, 스퍼터링 파워, 시간, 버퍼층의 두께에 따른 변수를 두어 실험하였다. 표면 특성을 알아보기 위해 OM, FE-SEM, AFM, EDS, XRD, XRR 그리고, 긋기 및 나노경도 시험을 시행하였다.