• Archives of Metallurgy and Materials
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• 제64권2호
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• pp.571-578
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• 2019

The densification behavior of H13 tool steel powder by dual speed laser scanning strategy have been characterized for selective laser melting process, one of powder bed fusion based metal 3d printing. Under limited given laser power, the laser re-melting increases the relative density and hardness of H13 tool steel with closing pores. The single melt-pool analysis shows that the pores are located on top area of melt pool when the scanning speed is over 400 mm/s while the low scanning speed of 200 mm/s generates pores beneath the melt pool in the form of keyhole mode with the high energy input from the laser. With the second laser scanning, the pores on top area of melt pools are efficiently closed with proper dual combination of scan speed. However pores located beneath the melt pools could not be removed by second laser scanning. When each layer of 3d printing are re-melted, the relative density and hardness are improved for most dual combination of scanning. Among the scan speed combination, the 600 mm/s by 400 mm/s leads to the highest relative density, 99.94 % with hardness of 53.5 HRC. This densification characterization with H13 tool steel laser re-melting can be efficiently applied for tool steel component manufacturing via metal 3d printing.

• Advances in materials Research
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• 제13권3호
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• pp.183-194
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• 2024

D3 tools steel and 440C stainless steel (SS) are normally being employed for application such as knife blade and cutting tools. These steels are iron alloys which have high carbon and high chromium content. In this study, lab work focused on the microstructural and corrosion behavior of D3 tools steel and 440C SS after went through heat treatment processes. Heat treatments for both steels were started with normalizing at 1020 ℃, continue with hardening at 1000 ℃followed by oil quenching. Cryogenic treatment was carried out in liquid nitrogen for 24 hours. The addition of cryogenic heat treatment is believed to increase the hardness and corrosion resistance for steels. Both samples were then tempered at two different tempering temperatures, 160 ℃ and 426 ℃. For corrosion test, the samples were immersed in NaCl solution for 30 days to study the corrosion behavior of D3 tool steel and 440C SS after heat treatment. The mechanical properties of these steels have been investigated using Rockwell hardness machine before heat treatment, after heat treatment (before corrosion) and after corrosion test. Microstructure observation of samples was carried out by scanning electron microscopy. The corrosion rate of these steels was calculated after the corrosion test completed. From the results, the highest hardness is observed for D3 tool steel which tempered at 160 ℃(54.1 HRC). In terms of microstructural analysis, primary carbide and pearlite in the as-received samples transform to tempered martensite and cementite after heat treatment process. From this research, for corrosion test, heat treated 440C SS sample tempered with 426 ℃possessed the excellent corrosion resistance with corrosion rate 0.2808 mm/year.

• 한국정밀공학회지
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• 제31권12호
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• pp.1093-1100
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• 2014

The goal of this paper is to investigate preliminary the applicability of 3D printing technologies for the development of the hot bulk forming process and die. 3D printing technology based on the plastic material was applied to the preform design of the hot forging process. Plastic hot forging dies were fabricated by Polyjet process for the physical simulation of the workpiece deformation. The feasibility of application of Laser-aided Direct Metal Rapid Tooling (DMT) process to the fabrication of the hot bulk metal forming die was investigated. The SKD61 hot-working tool steel was deposited on the heat treated SKD61 using the DMT process. Fundamental characteristics of SKD 61 hot-working tool steel deposited specimen were examined via hardness and wear experiments as well as the observation of the morphology. Using the results of the examination of fundamental characteristics, the applicability of the DMT process to manufacture hot bulk forming die was discussed.

• 동력기계공학회지
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• 제5권3호
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• pp.73-79
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• 2001

The purpose of this investigation is experimentally to clarify the machinability and tool wear of STS 304 steel pipe material for piping. In order to determine the effects of cutting parameters and tool wear on thrust, torque, AE RMS, drilling is conducted on CNC milling machine. In this experiment, it is measured that thrust, torque, tool wear length, tool wear area and AE RMS during drilling using Hss tool. It has been found that a) During the drilling, the thrust and the torque of the STS 304 pipe are received more the effect of the feed than the spindle speed and the thrust increase with the increase of feed, b) The value of the AE RMS is been larger the effect of the cutting speed than the feed rate, and the value of the AE RMS increase with the increase of spindle speed, c) It has been found that the suitable feed in feed condition of 0.03, 0.05, 0.1, 0.15mm/rev is below 0.05mm/rev, d) The value of the AE RMS was shown a characteristic of the jump value during it was a sudden inrcrease of the tool wear. The increased character of the AE RMS value can be known an effective factor of the tool wear detection, and e) It can be quantitatively evaluated the condition of the tool according to calculate a area of the drill wear image which is obtained by a vision system.

• 한국분말재료학회지
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• 제24권3호
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• pp.195-201
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• 2017

In this study, H13 tool steel sculptures are built by a metal 3D printing process at various laser scan speeds. The properties of commercial H13 tool steel powders are confirmed for the metal 3D printing process used: powder bed fusion (PBF), which is a selective laser melting (SLM) process. Commercial H13 powder has an excellent flowability of 16.68 s/50 g with a Hausner ratio of 1.25 and a density of $7.68g/cm^3$. The sculptures are built with dimensions of $10{\times}10{\times}10mm^3$ in size using commercial H13 tool steel powder. The density measured by the Archimedes method is $7.64g/cm^3$, similar to the powder density of $7.68g/cm^3$. The hardness is measured by Rockwell hardness equipment 5 times to obtain a mean value of 54.28 HRC. The optimum process conditions in order to build the sculptures are a laser power of 90 W, a layer thickness of $25{\mu}m$, an overlap of 30%, and a laser scan speed of 200 mm/s.

• 융합정보논문지
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• 제10권11호
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• pp.218-223
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• 2020

본 연구는 3D프린터로 제작된 PLA재질의 도구와 기성품인 스테인리스 스틸 재질 도구 사이의 연부조직 가동술에 의한 근활성도 차이를 관찰하고자 수행하였다. 본 연구는 20대 성인 10명이 참석하였고, 모든 대상자는 각각 PLA재질의 도구를 사용하여 연부조직 가동술을 받은 PLA 집단과 스테인리스 스틸 재질의 도구를 사용한 Stainless 집단에 모두 참여하여 도구를 이용한 연부조직 가동술(IASTM)을 받았다. 모든 대상자는 중재 후 근활성도의 측정을 통해 %MVIC가 측정되었고, 이를 Mann-Whitney U검정을 통해 집단간 비교를 통해 검증하였다. 본 연구의 결과는 중재 후 위팔 두갈래근의 %MVIC 값은 두 집단 간 유의한 차이를 보이지 않았다. 따라서 IASTM의 적용에서 도구의 재질에 따라 근활성도의 차이를 보이지 않았고, 이는 3D프린터로 제작된 PLA재질의 IASTM 도구가 스테인리스로 제작된 기성품과 신경근 조절 능력에서 유사한 결과를 도출해 냄으로 보인다. 이에 추후 연구에서는 다양한 환자군을 대상으로 도구의 실효성에 대해 검증할 것이다.

• 한국분말재료학회지
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• 제22권3호
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• pp.157-162
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• 2015

SKD11(ASTM D2) tool steel is a versatile high-carbon, high-chromium, air-hardening tool steel that is characterized by a relatively high attainable hardness and numerous, large, chromium rich alloy carbide in the microstructure. SKD11 tool steel provides an effective combination of wear resistance and toughness, tool performance, price, and a wide variety of product forms. Adding of CNTs increased the performance of mechanical properties more. 1, 3 vol.% CNTs was dispersed in SKD11 matrix by mechanical alloying. SKD11 carbon nanocomposite powder was sintered by spark plasma sintering process. FE-SEM, HR-TEM and Raman analysis were carried out SKD11 carbon nanocomposites.

• Design & Manufacturing
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• 제16권3호
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• pp.39-43
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• 2022

In this study, we designed an vibration cutting tool that can achieve improvements such as low cutting force, interrupted chip evacuation and better surface quality of cutting performance to obtain high-quality surface roughness and improvement of tool wear, which is an issue in the machining of high-hardness mold steel. Among the resonance frequency modes of the vibration cutting tool, the bending mode was used to maximize the driving amplitude of the vibration tool tip, and the resonance frequency was confirmed through the finite element method. After measuring the actual resonant frequency of the designed tool using an optical fiber sensor, the cutting force and machining surface of vibration cutting and conventional cutting were compared and analyzed in the turning process of high hardness mold steel (STAVAX). As a result of the experiment, the cutting force was reduced by about 20 % compared to the conventional cutting process, and the surface roughness was also improved by about 60 %. This study suggested that the tool wear and surface quality of high-hardness steel can be improved through the vibration cutting method in the machining of high hardness mold steel.

• 소성∙가공
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• 제31권3호
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• pp.129-135
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• 2022

The purpose of this study was to quantitatively evaluate the influence of hardness of tool materials on wear resistance in the sheet metal forming process. Punches used in the wear test were made of STD-11 and K340 tool material, and the tempering temperature was set to 530℃ and 500℃, respectively, to control the hardness of the tool materials. The punches mimic the shape of stamping tool of automotive body component to reflect its plastic deformation, and are designed to concentrate wear on the curvature region of punches. Progressive die and coil sheet were used to save time, cost, and raw sheet materials. By quantitatively measuring the wear depth of the punches, the wear behavior and mechanism of the punches were investigated, and characteristics of hardness and wear resistance according to tool materials and tempering temperatures were evaluated. Testing results indicate that the punch made of K340 tool steel with higher hardness had better wear resistance than that of STD-11 tool steel, and the hardness and wear resistance of tool steel were significantly impacted by the tempering temperature.

• 한국분말재료학회지
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• 제20권4호
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• pp.291-296
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• 2013

SKD11 (ASTM D2) tool steel is a versatile high-carbon, high-chromium, air-hardening tool steel that is characterized by a relatively high attainable hardness and numerous, large, chromium rich alloy carbide in the microstructure. SKD11 tool steel provides an effective combination of wear resistance and toughness, tool performance, price, and a wide variety of product forms. The CNTs was good additives to improve the mechanical properties of metal. In this study, 1, 3 vol% CNTs was dispersed in SKD11 matrix by mechanical alloying. The SKD11+ CNT hybrid nanocomposites were investigated by FE-SEM, particle size distribution, hardness and wear resistance. The CNT was well dispersed in the SKD11 matrix and the mechanical properties of the composite were improved by CNTs addition. It shows good feasibility as cold work die tool.