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금형공구강의 후산화와 침류질화에 의해 형성된 복합층의 조직과 특성에 관한 연구
이재식(J . S . Lee),김한군(H . G . Kim),유용주(Y . Z . You) 한국열처리공학회 2001 熱處理工學會誌 Vol.14 No.2
N/A 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 Fe₃O₄layer 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.
이재식(J . S . Lee),김한군(H . G . Kim),유용주(Y . Z . You) 한국열처리공학회 2001 熱處理工學會誌 Vol.14 No.1
N/A 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℃ and 1020℃ 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℃ for 5 hours was independent of pre-heat treatment condition and the depth was approximately 100㎛. 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 Υ-Fe4N and ε-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℃ which was 10℃ 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.
마이크로 펄스 플라즈마 질화에 의해 생성된 금형 공구강의 표면층에 관한 연구 - 공정 변수의 영향 -
이재식(J . S . Lee),김한군(H . G . Kim),유용주(Y . Z . You) 한국열처리공학회 2001 熱處理工學會誌 Vol.14 No.1
N/A The effects of gas composition, pressure, temperature and time on the case thickness, hardness and nitride formation in the surface of tool steels(STD11 and STD61) have been studied by micro-pulse plasma nitriding. External compound layer and internal diffusion layer and the diffusion layer were observed in the nitrided case of tool steels. The relative amounts and kind of phases formed in the nitrided case changed with the change of nitriding conditions. Generally, only nitride phases such as γ(Fe₄N), ε(Fe_(2-3)N), or Cr_(1.75)V_(0.25)N₂phases were detected in the compound layer, while nitride and carbide phases such as ε-nitride(Fe_(2-3)N), (Cr,Fe)_7C₃or Fe₃C were detected in the diffusion layer by XRD analysis. The thickness of compound layer increased with the increase of nitrogen content in the gas composition. Maximum case depth was obtained at gas pressure of 200Pa.
염종택(J. T. Yeom),김지훈(J. H. Kim),김정한(J. H. Kim),홍재근(J. K. Hong),이재식(J. S. Lee) 한국소성가공학회 2009 한국소성가공학회 학술대회 논문집 Vol.2009 No.5
The hot forming process of a CAM for vessel engine was designed by finite element (FE) simulation and experimental analysis. An aim of process design was to achieve the near-net shaped CAM forgings by hot forging process. Based on the compression test results of the low alloy steel, deformation processing map was generated using the superposition approach between the dynamic materials model(DMM) and flow stability and/or instability criteria. From the processing map, the initial heating temperature was determined as 1200℃. FE analysis was simulated to predict the formation of rolling defects and deformed shape with different forging designs. Optimum process design suggested In this work was made by comparing with the CAM for vessel engine manufactured by actual forging process.