• 한국세라믹학회지
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• 제36권12호
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• pp.1381-1389
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• 1999

• 소성∙가공
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• 제32권3호
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• pp.114-121
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• 2023

During rolling, rolling mill rolls endure wear when shaping metal billets into a desired form, such as bars, plates, and shapes. Such wear affects the lifespan of the rolls and product quality. Therefore, in addition to rigidity, wear performance is a key factor influencing the performance of rolling mill rolls. Conventional methods such as casting and forging have been used to manufacture rolling mill rolls. However, powder alloying methods are increasingly being adopted to enhance wear resistance. These powder manufacturing methods include atomization, canning to shape the powder, hot isostatic pressing to combine the powder alloy with conventional metals, and various wear performance tests on rolls prepared with powder alloys. In this study, numerical simulations and experimental tests were used to develop and elucidate the wear analysis mechanism of rolling mill rolls. The wear characteristics of the rolls under various rolling conditions were analyzed. In addition, experimental tests (wear and surface analysis tests) and wear theory (Archard wear model) were used to evaluate wear. These tests were performed on two different materials in various powder states to evaluate the different aspects of wear resistance. In particular, this study identifies the factors influencing the wear behavior of rolling mill rolls and proposes an analytical approach based on the actual production of products. The developed wear analysis mechanism can serve the future development of rolls with high wear resistance using new materials. Moreover, it can be applied in the mechanical and wear performance testing of new products.

• 열처리공학회지
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• 제33권3호
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• pp.99-106
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• 2020

Selective laser melting (SLM) is an additive manufacturing process by melting metallic powders and stacking into layers, and can product complex shapes or near-net-shape (NNS) that are difficult to product by conventional processes. Also, SLM process is able to raise the efficiency of production by creating a streamlined manufacturing process. For manufacturing in SLM process using Ti-6Al-4V powder, analysis of microstructural evolution and evaluation of mechanical properties are essential because of rapid melting and solidification process of powders according to high laser power and rapid scan speed. In addition, it requires a post-processing because the soundness and mechanical properties are degraded by defects such as pore, un-melted powder, lack-of-fusion, etc. In this study, hot isostatic press (HIP) was conducted as a post-processing on SLM-printed Ti-6Al-4V alloy. Microstructure of post-processed Ti-6Al-4V alloy was compared to as-built Ti-6Al-4V, and the evolution of quasi-static (Vickers hardness, room temperature tensile characteristic) and dynamic (high-cycle fatigue characteristic) mechanical properties were analyzed.

• 한국세라믹학회지
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• 제32권6호
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• pp.653-658
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• 1995

Directional effect of applied pressure during sintering on the microstructure and fracture toughness of the heat-treated silicon nitride ceramics has been investigated. The specimens with a composition of 92Si3N4-8Y2O3(in wt%) were sintered at 172$0^{\circ}C$ by a hot press (HP ) and a hot isostatic press (HIP) and heat-treated for grain growth at 1800~20$0^{\circ}C$. The fracture toughness of the HP samples increased with the grain size while the fracture toughness of the HIP treated samples remained the same even though the grain growth occurred. This discrepancy was explained by a bimodal grain size distribution and large aspect ratio of the HPed samples and a monomodal grain size distributjion and samll aspect ratio of the HIP treated samples.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2008년도 춘계학술발표대회 개요집
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• pp.13-13
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• 2008

• 동력기계공학회지
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• 제7권3호
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• pp.18-22
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• 2003

A Study has been made to investigate the effects of hot isostatic press(HIP) and post-HIP heat treatment on microstructures and mechanical properties of Ni-based single crystal superalloy CMSX-4. HIP process was found to heal and close micropores significantly, but did not affect the morphologies of. The elimination of as-cast micropores obtained by HIP process resulted in improved stress-rupture lives of Ni-base single crystal superalloy by 185%.

• Composites Research
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• 제20권4호
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• pp.9-17
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• 2007

분말야금법 및 고온진공가압기술, 열간등가압성형기술을 이용하여 알루미늄 금속기 복합재료를 제작하였으며 이들과 관련한 미시역학 기반 강화공정 모델을 개발하였다. 고온, 가압 성형공정은 기지재료의 비탄성거동과 성형체 내부의 기공 제거를 통한 충진을 수반하게 되며 이러한 공정은 압력, 온도 및 강화재의 체적분률 등과 같은 공정변수의 영향을 받게 된다. 따라서 개발된 강화공정 모델을 유한요소해석 프로그램에 적용함으로써 고온진공가압과 열간등가압 동안 기공의 상대밀도 변화에 따른 충진거동을 예측하였고 다양한 공정조건 하에서 실험결과와 잘 일치함을 확인하였다. 완성된 알루미늄 금속기 복합재료의 건전성 평가와 관련하여 인장시험을 수행하였으며 초기 잔존하는 기공의 영향에 따른 제반 기계적 특성을 고찰할 수 있었다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 추계학술대회 논문집
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• pp.280-280
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• 2007

Lead oxide-based ferroelectrics are the most widely used materials for piezoelectric actuators, sensors and transducers due to their excellent piezoelectric properties. Considering lead toxicity, there is great interest in developing lead-free piezoelectric materials, which are biocompatible and environmentally friendlier. Recently alkali oxide materials, including sodium - potassium niobate (NKN), have been given attention in view of their ultrasonic application and also as promising candidates for piezoelectric lead-free system. However, it is difficult to sinter such NKN-based materials via conventional sintering process. In this reason, many researchers have investigated hot press, hot isostatic press or spark-plasma sintering of NKN-based ceramics. In this study, as candidates for lead-free piezoelectric materials, dense (Na,K,Li)(Nb,Sb)$O_3$ systems were developed by conventional sintering process. The microstructures and piezoelectric properties of the (Na,K,Li)(Nb,Sb)$O_3$ systems were investigated as a function of variable compositions. The excellent piezoelectric and electromechanical properties indicate that this system is potentially good candidate as lead-free material for a wide range of electro-mechanical transducer applications.

• 한국분말재료학회지
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• 제26권6호
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• pp.508-514
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• 2019

In the development of advanced ceramic tools, material improvements and design freedom are critical in improving tool performance. However, in the die press molding method, many factors limit tool design and make it difficult to develop innovative advanced tools. Ceramic 3D printing facilitates the production of prototype samples for advanced tool development and the creation of complex tooling products. Furthermore, it is possible to respond to mass production requirements by reflecting the needs of the tool industry, which can be characterized by small quantities of various products. However, many problems remain in ensuring the reliability of ceramic tools for industrial use. In this study, alumina inserts, a representative ceramic tool, was manufactured using the digital light process (DLP), a 3D printing method. Alumina inserts prepared by 3D printing are pressurelessly sintered under the same conditions as coupon-type specimens prepared by press molding. After sintering, a hot isostatic pressing (HIP) treatment is performed to investigate the effects of relative density and microstructure changes on hardness and fracture toughness. Alumina inserts prepared by 3D printing show lower relative densities than coupon specimens prepared by powder molding but indicate similar hardness and higher fracture toughness values.