Al-7Si 합급의 결정립 미세화에 미치는 TiC 첨가의 영향

한윤성 ( Yun Sung Han ),최창옥 ( Chang Ock Choi ) 한국주조공학회 2003 한국주조공학회지 Vol.23 No.2

N/A Al-Ti-C grain refiner form a relatively new alternative to the existing class of Al-Ti-B type grain refiners for achieving fine equiaxed structures in aluminum alloys during casting and solidification. The present study was carried out to investigate the influence of Al-Ti-C master alloys on the grain structure of Al-7Si alloys. The present study also investigates the relationship between grain refining efficiency and concentrations of Fe and Si in hypo-eutectic Al-Si alloys using Al-3Ti-0.13C master alloys. It is found that several parameters affect significantly the grain refining performance in silumin alloys. the present study reports the influence of various parameters such as alloy content, master alloy addition level, melt holding time and superheat on the grain refining efficiency in Al-7Si alloys.

정밀주조용 ALLOY738LC 모합금 제조 및 평가 기술

우한별(Hanbyul Woo),신정호(Jungho Shin),송영석(Youngseok Song) 항공우주시스템공학회 2023 항공우주시스템공학회 학술대회 발표집 Vol.2023 No.10

Functional and Environmental Advantage of Cleaning Ti5B1 Master Alloy

Aleksandar Mitrašinović,Miloš Tomić 한국정밀공학회 2022 International Journal of Precision Engineering and Vol.9 No.3

One of the greatest environmental goals for the aluminum alloys industry is generating higher quality products by introducing cleaner input materials while maintaining low production costs. A typical dilemma for the master alloy producers is the cleanness level of the master alloy since insoluble inclusions could serve as inoculants during the solidification process. In this work, commercial Ti5B1 master alloy is used for grain refinement of Al7Si4Cu aluminum alloy and compared with the cleaned master alloy that contained a lower amount of residual refractory oxides and salts. Metallography analysis was used for grain size measurement while Computer Aided Cooling Curve Analysis was used for assessment of the undercooling and heat release values. In all instances, specimens treated with the cleaned master alloy showed smaller grains in the final structure and lower undercooling values. The difference in released heat between liquidus and recalescence temperatures was about 25% in specimens where added 0.66 wt% of cleaned master alloys compared to specimens where the commercial master alloys were added. Using cleaner Ti5B1 master alloy with a higher number of TiAl 3 and TiB 2 particles improves its grain refi nementefficiency and transmits fewer impurities in produced parts. Producing cleaner master alloy would be beneficial from economic and environmental aspects by increasing its value and service time of produced parts besides simplifying the recycling process at the end of parts life-cycle.

백색금 합금용 모합금의 실리콘 함량에 따른 물성변화

송정호,노윤영,이현우,최민경,송오성,Song, Jeongho,Noh, Yunyoung,Lee, Hyeonwoo,Choi, Minkyoung,Song, Ohsung 한국재료학회 2015 한국재료학회지 Vol.25 No.2

We prepared 8 samples of non-silver and silver-added master alloys containing silicon to confirm the existence of nickel-silicides. We then prepared products made of 14K and 18K white gold by using the prepared master alloys containing 0.25, 0.35, and 0.50 wt% silicon to check for nickel release. We then employed the EN 1811 testing standard to investigate the nickel release of the white gold products, and we also confirmed the color of the white gold products with an UV-VIS-NIR-color meter. We observed $NiSi_x$ residue in all master alloys containing more than 0.50 wt% Si with EDS-nitric acid etching. For the white gold products, we could not confirm the existence of $NiSi_x$ through XRD after aqua-regia etching. In the EN 1811 test, only the white gold products with 0.25 wt% silicon master alloys successfully passed the nickel release regulations. Moreover, we confirmed that our white gold products showed excellent Lab indices as compared to those of commercial white gold ones, and the silver-added master alloys offered a larger L index. Our results indicate that employing 0.25 wt% silicon master alloys might be suitable for white gold products without nickel-silicide defects and nickel release problems.

Alloy 690 증기발생기 전열관 재료의 크리프 거동 평가

김종민,김우곤,김민철 한국압력기기공학회 2019 한국압력기기공학회 논문집 Vol.15 No.2

In recent years, attention has been paid to the integrity of steam generator (SG) tubes due to severe accident and beyond design basis accident conditions. In these transient conditions, steam generator tubes may be damaged by high temperature and pressure, which might result in a risk of fission products being released to the environment due to the failure. Alloy 690 which has increased the Cr content has been replaced for the SG tube due to its high corrosion resistance against stress corrosion cracking (SCC). However, there is lack of research on the high temperature creep rupture and life prediction model of Alloy 690. In this study, creep test was performed to estimate the high temperature creep rupture life of Alloy 690 using tube specimens. Based on manufacturer’s creep data and creep test results performed in this study, creep life prediction was carried out using the Larson-Miller (LM) Parameter, Orr-Sherby-Dorn (OSD) parameter, Manson-Haford (MH) parameter, and Wilshire’s approach. And a hyperbolic sine (sinh) function to determine master curves in LM, OSD and MH parameter methods was used for improving the creep life estimation of Alloy 690 material.

주얼리용 마스터패턴의 쾌속제작에 관한 연구

주영철,이창훈,송오성 한국산학기술학회 2002 한국산학기술학회논문지 Vol.3 No.2

주얼리 제조 공정중 마스터패턴 제조 공정은 전체 제조원가의 20%를 차지하기 때문에 매우 중요한 공정이다. 지금까지는 수작업으로 왁스 패턴을 제작하고 이를 이용하여 석고형을 만들고 석고형로 마스터 패턴을 제작하는 복잡한 공정을 거쳐 제작하였다. 본 연구는 쾌속조형기를 이용하여 듀라폼 재질의 몰드를 만들고 저융점합금을 이용하여 마스터패턴을 직접 제작하는 새로운 공정을 개발하였다. 듀라폼의 용융점이 190℃ 이므로 용융점 70℃의 Pb-Sn-Bi-Cd 제의 저융점 합금을 주물재료로 이용하여 마스터패턴을 제작하였다. The master pattern manufacturing process is one of the most important processes in jewelry industry because the process takes 20% of total jewelry manufacturing costs. The previous jewelry manufacturing process has many steps of "rough design → detailed drawing → wax pattern manufacturing → lime soda flask mold manufacturing → silver master pattern manufacturing → mass production of wax pattern → investment casting process → final jewelry product." A novel process that reduces processing steps by using a rapid prototyping system (RP) has been suggested. The process is "3D CAD design → DuraForm mold manufacturing by RP → manufacturing master pattern by low melting alloy → mass production of wax pattern → investment casting process → final jewelry product." Molds are made with DuraForm powder, of which melting temperature is 190℃, by a selective laster sintering type RP. An alloy of Pb-Sn-Bi-Cd, of which melting temperature is 70℃, is casted in the DuraForm molds. Spheres and rings of diameter 20 ㎜ are made by this process. The dimension deformation rate is less than 2%, and the post processing of the castings is convenient. The casting made by the suggested process can be used as a master pattern of jewelry products.

Cleavage fracture toughness of tempered martensitic Ni-Cr-Mo low alloy steel with different martensite fraction

Lee, K.H.,Park, S.G.,Kim, M.C.,Lee, B.S. Elsevier Sequoia 2012 Materials science & engineering. properties, micro Vol.534 No.-

This study investigates the relationship between fracture toughness behavior and phase fraction using the master curve approach for SA508 Gr.4N Ni-Cr-Mo low alloy steel. The different phase fractions of the model alloy were obtained by controlling the cooling rate from the austenitization temperature to transformation temperature. The fracture toughness tests were carried out using ASTM E1921-09c, standard master curve method. Yield strength and the impact toughness at room temperature are improved when increasing tempered martensite fraction, but the transition region narrowed in a fully martensitic microstructure. Fracture toughness test results indicated that transition properties are improved when increasing the tempered martensite fraction by reducing the probability of discovering carbide larger than critical size, which can act as cleavage initiation site. The exponential fitting for datasets of the model alloys showed that the temperature dependency of the measured fracture toughness is steeper with higher fraction of the tempered martensite. The T<SUB>0</SUB> values determined from the adjusted curves for the data distribution well reflect the variation of transition property with the phase fraction when compared to the T<SUB>0</SUB> values from the standard master curves.

Analysis of the master curve approach on the fracture toughness properties of SA508 Gr.4N Ni–Mo–Cr low alloy steels for reactor pressure vessels

Lee, Ki-Hyoung,Kim, Min-Chul,Lee, Bong-Sang,Wee, Dang-Moon Elsevier 2010 Materials science & engineering. properties, micro Vol.527 No.15

<P><B>Abstract</B></P><P>This study aims at assessing the fracture toughness behavior of tempered martensitic Ni–Mo–Cr low alloy steels for reactor pressure vessels in a transition temperature region using a master curve approach. The fracture toughness tests for model alloys with various chemical compositions were carried out following ASTM E1921-08. The microstructures, tensile properties, and Charpy impact toughness were also evaluated. Alloying elements such as Ni, Cr, and Mo affected the mechanical properties of alloys from changes in the phase fraction and precipitation behavior. In the fracture toughness test results, the data sets showed a deviation from the median curve and a smaller scatter than that of the prediction of the ASTM standard, especially in the lower transition region. The exponential parameter of the master curve equation was adjusted by an exponential fitting to data sets for expressing well the temperature dependency of the fracture toughness. The adjusted parameter provided good agreement for data distribution and the independence of <I>T</I><SUB>0</SUB> from test temperatures through an overall temperature range in contrast with the results from the standard master curve.</P>

A Novel Process for Producing Ferromolybdenum Powder Master Alloy without Generating Secondary Pollutants through a Two-Step Hydrogen Reduction Process

Kim, Byung-Su,Kim, Sang-Bae,Lee, Hoo-In,Choi, Young-Yoon The Japan Institute of Metals 2011 MATERIALS TRANSACTIONS Vol.52 No.6

<P>A new process for producing ferromolybdenum powder master alloy without generating secondary pollutants by a two-step hydrogen reduction process involving MoO<SUB>3</SUB> and mill scale has been developed. In this process, mill scale which is an iron byproduct generated from the steel rolling process is used as an iron source. Experimentally, ferromolybdenum powder master alloy was produced by a two-step hydrogen reduction process: The first hydrogen reduction stage was carried at a horizontal furnace for 60 min at 848 K under a hydrogen gas at a partial pressure of 101.3 kPa, and the second hydrogen reduction stage was done at the same furnace for 40 min at 1123 K under the same hydrogen partial pressure. In the process, the reduction reactions of MoO<SUB>3</SUB> to MoO<SUB>2</SUB> and mill scale to Fe proceed simultaneously in the first reduction step, and then the reduction reaction of MoO<SUB>2</SUB> to Mo does in the second reduction step. The reaction rate of the second step in the two-step hydrogen reduction process of MoO<SUB>3</SUB>-Fe<SUB>2</SUB>O<SUB>3</SUB> mixture was also measured under isothermal condition in hydrogen atmosphere using TGA equipment. As an example, at 1173 K under a hydrogen partial pressure of 101.3 kPa, almost 100% of MoO<SUB>2</SUB> was reduced to Mo in 5 min. The nucleation and growth model were found to be applicable to the reaction rate. The reaction was first order with respect to hydrogen partial pressure and had an activation energy of 83.8 kJ/mol (20.1 kcal/mol).</P>

Magnetic and magnetocaloric properties of Ni-Ag-Mn-Sn ribbons and their composites

Thanh, Tran Dang,Duc, Nguyen Huu,Dan, Nguyen Huy,Mai, N.T.,Phan, T.L.,Oh, S.K.,Yu, Seong-Cho Elsevier 2017 Journal of Alloys and Compounds Vol.696 No.-

<P><B>Abstract</B></P> <P>In this work, we have investigated the influence of Ag-doping on the magnetic and magnetocaloric effect (MCE) of Ni<SUB>50-x</SUB>Ag<SUB>x</SUB>Mn<SUB>37</SUB>Sn<SUB>13</SUB> ribbons with <I>x</I> = 1, 2, and 4, which were prepared by a melt-spinning method. With increasing Ag concentration, a systematic decrease in the antiferromagnetic interaction and in the magnetic phase transition temperatures was observed. Analyses of the critical behavior based on the Banerjee criterion and scaling hypothesis for <I>M</I>(<I>H</I>, <I>T</I>) data near the ferromagnetic-paramagnetic transformation prove an increase of Ag favors establishing long-range ferromagnetic interactions in the austenitic phase. The temperature and magnetic field dependences of magnetic entropy change, Δ<I>S</I> <SUB>m</SUB>(<I>T</I>, <I>H</I>) were investigated via isothermal magnetization measurements. Interestingly, these samples exhibit a MCE at room-temperature with the Δ<I>S</I> <SUB>m</SUB>(<I>T</I>) curves distributed over a quite wide temperature range. To enhance the relative cooling power (RCP) value and to extend the magnetic phase transition region, we have prepared the composites in the form of the layered material samples based on ribbons obtained above. Under Δ<I>H</I> = 10 kOe, the maximum value of Δ<I>S</I> <SUB>m</SUB> (denoted as |Δ<I>S</I> <SUB>max</SUB>|) at around room-temperature is 1.08 J kg<SUP>−1</SUP> K<SUP>−1</SUP>, corresponding to RCP = 51.8 J kg<SUP>−1</SUP>, which is about 10% higher than that obtained from a separate sample. Additionally, we also pointed out that the dependences of |Δ<I>S</I> <SUB>max</SUB>| on Δ<I>H</I> at around room-temperature for samples obey a power law, |Δ<I>S</I> <SUB>max</SUB>| = <I>a</I> × Δ<I>H</I> <SUP>n</SUP>, and all the Δ<I>S</I> <SUB>m</SUB>(<I>T</I>, <I>H</I>) data obey completely a universal master curve.</P> <P><B>Highlights</B></P> <P> <UL> <LI> An increase of Ag in Ni<SUB>1-x</SUB>Ag<SUB>x</SUB>Mn<SUB>37</SUB>Sn<SUB>13</SUB> ribbons favors establishing long-range FM order in the austenitic phase. </LI> <LI> High magnetic entropy change, wide operative temperature range, and high RCP value around room-temperature. </LI> <LI> The composite of Ni<SUB>1-x</SUB>Ag<SUB>x</SUB>Mn<SUB>37</SUB>Sn<SUB>13</SUB> ribbons exhibits higher RCP value and extends the magnetic phase transition region. </LI> <LI> Field dependence of |Δ<I>S</I> <SUB>max</SUB>| can be expressed by the power law. </LI> <LI> All the Δ<I>S</I> <SUB>m</SUB>(<I>T, H</I>) data around room temperature are followed a universal master curve. </LI> </UL> </P>