알칼리 침출법을 통한 초경 공구의 재활용 및 자전연소합성법을 통해 제조된 나노급 탄화텅스텐 제조공정 연구

강희남,정동일,김영일,박상철,남철우,서석준,이진영,이빈 한국분말재료학회 2022 한국분말재료학회지 (KPMI) Vol.29 No.1

Tungsten carbide is widely used in carbide tools. However, its production process generates a significant number of end-of-life products and by-products. Therefore, it is necessary to develop efficient recycling methods and investigate the remanufacturing of tungsten carbide using recycled materials. Herein, we have recovered 99.9% of the tungsten in cemented carbide hard scrap as tungsten oxide via an alkali leaching process. Subsequently, using the recovered tungsten oxide as a starting material, tungsten carbide has been produced by employing a self-propagating high-temperature synthesis (SHS) method. SHS is advantageous as it reduces the reaction time and is energy-efficient. Tungsten carbide with a carbon content of 6.18 wt % and a particle size of 116 nm has been successfully synthesized by optimizing the SHS process parameters, pulverization, and mixing. In this study, a series of processes for the highefficiency recycling and quality improvement of tungsten-based materials have been developed.

텅스텐의 제련과 리사이클링 현황

손호상,Sohn, Ho-Sang 한국분말재료학회 (*구 분말야금학회) 2021 한국분말재료학회지 (KPMI) Vol.28 No.4

Because of its unique properties, tungsten is a strategic and rare metal used in various industrial applications. However, the world's annual production of tungsten is only 84000 t. Ammonium paratungstate (APT), which is used as the main intermediate in industrial tungsten production, is usually obtained from tungsten concentrates of wolframite and scheelite by hydrometallurgical treatment. Intermediates such as tungsten trioxide, tungsten blue oxide, tungstic acid, and ammonium metatungstate can be derived from APT by thermal decomposition or chemical attack. Tungsten metal powder is produced through the hydrogen reduction of high-purity tungsten oxides, and tungsten carbide powder is produced by the reaction of tungsten powder and carbon black powder at 1300-1700℃ in a hydrogen atmosphere. Tungsten scrap can be divided into hard and soft scrap based on shape (bulk or powder). It can also be divided into new scrap generated during the production of tungsten-bearing goods and old scrap collected at the end of life. Recycling technologies for tungsten can be divided into four main groups: direct, chemical, and semi-direct recycling, and melting metallurgy. In this review, the current status of tungsten smelting and recycling technologies is discussed.

초미립 WC-Graphene-Al₂O₃ 복합재료 소결 및 기계적 성질

손인진 ( In-jin Shon ) 한국열처리공학회 2023 熱處理工學會誌 Vol.36 No.4

Tungsten carbide has many industrial applications due to its high electrical and thermal conductivity, high melting temperature, high hardness and good chemical stability. Because tungsten carbide is difficult to sinter, it is sintered with nickel or cobalt as a binder and is currently used in nozzles, cutting tools, and molds. Alumina is reported to be a viable binder for tungsten carbide due to its higher oxidation resistance and lower cost than nickel and cobalt. The ultrafine tungsten carbide-graphene-alumina composites were rapidly sintered in a high frequency induction heating active sintering unit. The microstructure and mechanical properties (fracture toughness and hardness) of the composites were investigated and analyzed by Vickers hardness tester and electron microscope. Since the high-frequency induction heating sintering method enables high-speed sintering, ultrafine composites can be prepared by preventing grain growth. In the tungsten carbide-graphene-alumina composites, the grain size of tungsten carbide increased with the amount of alumina participation. The hardness and fracture toughness of the tungsten carbide-5% graphene- x% alumina (x = 0, 5, 10,15) composites were 5.1, 8.6, 8.6, and 8.4 MPa-m^1/2 and 2384, 2168, 2165, and 2102 kg/mm², respectively. The fracture toughness increased without a significant decrease in hardness. Sinterability was improved by adding alumina to tungsten carbidegraphene. (Received June 9, 2023; Revised June 19, 2023; Accepted July 3, 2023)

화학기상응축법에 의한 나노구조 텅스텐카바이드 분말의 제조와 미세구조 변화

김병기,김진천,하국현,최철진,O.V.Tolochko 한국분말야금학회 2002 한국분말재료학회지 (KPMI) Vol.9 No.3

Nanosized tungsten carbide powders were synthesized by the chemical vapor condensation(CVC) process using the pyrolysis of tungsten hexacarbonyl($W(CO)_6$). The effect of CVC parameters on the formation and the microstructural change of as-prepared powders were studied by XRD, BET and TEM. The loosely agglomerated nanosized tungsten-carbide($WC_{1-x}$) particles having the smooth rounded tetragonal shape could be obtained below $1000^{\circ}C$ in argon and air atmosphere respectively. The grain size of powders was decreased from 53 nm to 28 nm with increasing reaction temperature. The increase of particle size with reaction temperature represented that the condensation of precursor vapor dominated the powder formation in CVC reactor. The powder prepared at $1000^{\circ}C$ was consisted of the pure W and cubic tungsten-carbide ($WC_{1-x}$), and their surfaces had irregular shape because the pure W was formed on the $WC_{1-x}$ powders. The $WC_{1-x}$ and W powders having the average particles size of about 5 nm were produced in vacuum.

Surface Grinding of Tungsten Carbide for High Quality Using Diamond Wheel

Heo, Seoung-Jung,Wang, Duck-Hyun,Kim, Won-Il 한국공작기계학회 1995 한국생산제조학회지 Vol.4 No.3

Various surface grinding experiments using resin bonded diamond abrasive wheels are carried out for tungsten-carbide materials in order to minimize the damage on the ground surface and to purse the the precise dimension compared to conventional grinding machine. When grinding quality is constant, theoreticalgrinding effect is changed according to the speed of workpiece. Accordingly, grinding forces, which are Fn, Ft, were analyzed for the machining processes of tungsten-carbide material to obtain optimum grinding conditions. Brief investigation is carried out to decrease the dressing efficiency of resinoid bonded diamond grinding wheel to grind tungsten-carbide. Truing is also carried out to provide a desired shape on a wheel or to correct a dulled profile. High quality in dimensional accuracy and surface are often required as a structural components, therefore 3-points bending test is carried out to check machining damage on the ground surface layer, which is one of sintered brittle material. From this experimental study, some useful machining data and information to determine proper machining condition for grinding of tungsten-carbide material s are obtained.

디스크 공구를 이용한 초경합금의 미세 홈 가공에 대한 연구

김민기,양찬영,심대보,이지효,김보현 한국정밀공학회 2024 한국정밀공학회지 Vol.41 No.2

Recently, the demand for micromachining of hard materials has been increasing. Machining microholes, grooves, and structures in hard materials such as tungsten carbide is very difficult. In this study, the machining characteristics of amicrodisk tool for microgroove machining of tungsten carbide were studied. Microtools made of polycrystalline diamond (PCD) were fabricated using wire electrical discharge grinding (WEDG) to machine high-hardness tungsten carbide. Rectangular and V-shaped disk tools were fabricated by WEDG with controlled wire paths. In the micro grooving of tungsten carbide, the effects of capacitance and feedrate on the surface roughness of microgrooves and the wear of disk tools were studied. As the capacitance and feed rate decreased, the surface roughness decreased and no significant wear was observed in the PCD tool. However, an increase in tool edge radius of several micrometers was observed.

Tungsten Carbide-Silicon Carbide Nanocomposite Fibers Prepared from Tungsten Nanoparticle Dispersed Polycarbosilane by Electrospinning

신동근,조광연,진은주,김영희,김수룡,권우택,이윤주,Jun-Sung Hong,류도형 한양대학교 세라믹연구소 2013 Journal of Ceramic Processing Research Vol.14 No.4

W2C–SiC nanocomposite fibers were fabricated by electrospinning and pyrolysis using tungsten nanoparticle (nW; diameter, 3-5 nm) dispersed polycarbosilane solution. The nW was uniformly dispersed in the electrospun polycarbosilane fibers and transformed into α-W2C during pyrolysis at 1200 o C, where the polycarbosilane-derived SiC fibers acted as a source of carbon and as an effective support for the α-W2C nanoparticles, preventing them from converting into another phase at 1200 o C. A part of the nW dispersed on the fiber surface is considered to transform into α-W2C at the early stages of pyrolysis by carburization with the gases evolved during the pyrolytic decomposition of poly carbosilane, such as CH4.

Highly efficient tungsten carbide counter electrode for dye-sensitized solar cells

김진,강진수,최정우,정주원,임아연,손윤준,성영은 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.1

염료감응태양전지(Dye-sensitized Solar Cells)는 가시광선 영역의 빛을 흡수하는 염료를 이용하여 빛에너지를 전기에너지로 변환하는 에너지변환장치이다. 일반적으로 염료감응태양전지의 작동전극으로는 염료가 흡착된 TiO₂를 사용하게 되고, 염료를 통해 흡수된 빛에너지로부터 전자가 생성되고 이 전자는 외부회로를 통하여 상대전극에 도달하게 된다. 상대전극은 전자를 받아 redox couple을 환원시키는 역할을 하는데, 일반적으로 전기전도성이 높고 촉매활성이 뛰어난 백금상대전극을 사용한다. 하지만 실질적인 염료감응태양전지의 대량생산과 상용화를 위해서는 noble metal인 백금을 대체할 수 있는 상대전극이 필요하게 된다. 백금전극을 대체할 물질로는 carbon materials, conducting polymer, transition metal compound 등 여러 대체 물질들이 연구가 되었다. 이번 실험에서는 전기화학적으로 합성한 Tungsten carbide를 상대전극으로 사용하여 전기화학적 분석을 진행하였다.

Micro Pin Fabrication of Tungsten Carbide Using Polycrystalline Diamond

박주아(Joo A Park),이의석(Ui Seok Lee),김보현(Bo Hyun Kim) Korean Society for Precision Engineering 2020 한국정밀공학회지 Vol.37 No.11

Micro tool fabrication is crucial in micro machining. Wire electro-discharge grinding (WEDG) is one of the popular methods applied to fabricate micro tools used for micro electrical discharge machining (EDM), electrochemical machining (ECM), and ultrasonic machining (USM). WEDG can machine micro tools or features regardless of workpiece hardness. In WEDG, however, the machining speed is relatively low and the discharge gap control is not easy. In this study, the micro mechanical machining using the polycrystalline diamond is introduced to fabricate the micro cylindrical tool or micro pin of the tungsten carbide. This method demonstrates the possibility of applying ductile machining of tungsten carbide without brittle fracture or cracks. This paper compared the machining characteristics such as material removal rate and surface roughness with the PCD-mechanical machining and WEDG.

텅스텐과 텅스텐-하프늄카바이드에 대한 삭마 실험 및 삭마 모델 개발 연구

김평기,노성준,김규홍 한국항공우주학회 2015 한국항공우주학회 학술발표회 논문집 Vol.2015 No.4

텅스텐과 텅스텐-하프늄카바이드에 대한 삭마 실험을 수행하고 이를 바탕으로 삭마 모델을 개발하였다. 텅스텐의 삭마 특성을 파악하기 위하여 엔탈피에 대한 삭마 실험을 수행하였으며, 엔탈피 증가에 따라 삭마량이 증가하는 것을 확인하였다. 실험 결과를 이용하여 텅스텐의 산화 속도를 도출하였으며 이를 기반으로 텅스텐의 삭마 모델을 개발하였다. 또한 고온 삭마에 취약한 단점을 개선하기 위하여 텅스텐-하프늄카바이드를 제작하고 삭마 실험을 수행하였다. 실험 결과 하프늄카바이드의 함량이 증가함에 따라 내삭마성이 증가하는 것을 확인하였으며, 텅스텐과 하프늄카바이드 입자간의 결합은 물리적인 요인에 기인함을 확인하였다. 이와 같은 실험 결과를 바탕으로 순수 텅스텐 삭마 모델을 확장한 텅스텐 복합재 삭마 모델을 개발하였다. In order to investigate ablation characteristics of pure tungsten, ablation experiments were conducted. The experiments were done varying enthalpy and stagnation pressure, and it was seen that the amount of recession increases along with the variables. From the experiments, oxidation coefficient of tungsten was deduced with which tungsten ablation mode was established. In addition, W-HfC specimens were produced and ablation experiments were conducted using the specimen. It was seen that the ablation resistance increases with respect to HfC volume fraction and with the experimental results, ablation model for W-HfC was developed.