• Title, Summary, Keyword: Heat Resistant metals

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High Temperature Corrosion Properties of Heat Resistant Chrome Steels in SO2 Atmosphere (고온 이산화황 환경 내 내열 크롬강에 대한 부식특성 연구)

  • Lee, Han-sang;Jung, Jine-sung;Kim, Eui-hyun
    • Korean Journal of Metals and Materials
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    • v.47 no.2
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    • pp.99-106
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    • 2009
  • The high temperature corrosion properties of heat resistant steels were investigated in oxidation atmosphere including sulfur dioxide. The heat resistant steels of T22, T92, T122, T347HFG and T304H were evaluated at 620, $670^{\circ}C$ for 400 hours. The corrosion rates showed a decreasing tendency while chrome contents of those steels increased from 2 mass.% to 19 mass.%. The in crease in temperature increasement has an more effect on the corrosion rates of low chrome steels than high chrome steels. The weight gains of T22, T92, T304H at $670^{\circ}C$ were 3.7, 1.65, 1.23 times compared with those at $620^{\circ}C$. The external scale formed on T22 was composed of hematite, magnetite and Fe-Cr spinel and internal layer including iron oxide mixed with sulfide. The scales formed on T92, T122, T304H consisted of an outer layer of hematite and inner layer of chrome oxide and hematite. The proportion of chrome oxide at inner layer was increased when the chrome contents in heat resistant steels were increased.

A Study on the Optimum Chemical Composition of Insert Metal for Liquid Phase Diffuse Bonding (액상확산접합용 인서트금속의 화학조성 최적화에 관한 연구)

  • 김대업;정승부;강정윤
    • Journal of Welding and Joining
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    • v.18 no.5
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    • pp.90-97
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    • 2000
  • Effect of alloy elements on joinability of insert metal for liquid phase diffusion bonding of heat resistant alloys was investigated in this study. Also, optimum chemical composition of insert metal was explained using interpolation method. The insert metals utilized was commercial Ni-base amorphous foils and newly developed Ni-base filler metals with B, Si and Cr in this study. Melting point and critical interlayer width(CIW) decreased with increasing additional amount of B, Si and Cr, melting point lowering element of the insert metal. Optimized chemical composition of insert metals could be estimated by interpolation method. The optimum amount of B, Si, Cr addition into the insert metal were found to be about 3%, 4% and 3%, respectively. The measured characteristic values, melting point, microhardness in the bonded interlayer and CIW of the insert metals were the almost identical to ones of the calculated results by interpolation method.

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Thermal Structural Analysis of a Duct with Heat Resistant Metal Materials for Smart UAV (고온 내열재료를 사용한 스마트 무인기 덕트의 열 구조 해석)

  • Im, J.B.;Yoon, D.Y.;Lee, K.M.;Park, J.S.
    • Journal of the Korean Society for Aviation and Aeronautics
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    • v.12 no.2
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    • pp.17-28
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    • 2004
  • In unmanned aerial vehicle (UAV), the high temperature results from friction with the air, combustion of fuel and combustion gas of a nozzle etc. It causes serious problems in the UAV structure. The characteristic analysis of heat resistant metal and ceramic materials and creep analysis for the functionally graded material (FGM) is presented in this paper. FGM is composed of two constituent materials that are mixed up according to the specific volume fraction distribution in order to withstand high heat condition. In addition, the creep behavior of FGM applied in duct structure of an engine is analyzed.

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High Temperature Fatigue Deformation Behavior of Automotive Heat Resistant Aluminum Alloys (자동차 부품용 내열 알루미늄 합금의 고온 피로 변형 거동)

  • Park, Jong-Soo;Sung, Si-Young;Han, Bum-Suck;Jung, Chang-Yeol;Lee, Kee-Ahn
    • Korean Journal of Metals and Materials
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    • v.48 no.1
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    • pp.28-38
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    • 2010
  • High temperature high cycle and low cycle fatigue deformation behavior of automotive heat resistant aluminum alloys (A356 and A319 based) were investigated in this study. The microstructures of both alloys were composed of primary Al-Si dendrite and eutectic Si phase. However, the size and distribution for eutectic Si phase varied: a coarse and inhomogeneous distributed was observed in alloy B (A319 based). A brittle intermethallic phase of ${\alpha}-Fe\;Al_{12}(Fe,Mn)_3Si_2$ was detected only in B alloy. Alloy B exhibited high fatigue life only under a high stress amplitued condition in the high cycle fatigue results, whereas alloy A showed high fatigue life when stress was lowered. With regard to the low-cycle fatigue result ($250^{\circ}C$) showing higher fatigue life as ductility increased, alloy A demonstrated higher fatigue life under all of the strain amplitude conditions. Fractographic observations showed that large porosities and pores near the outside surface could be the main factor in the formation of fatigue cracks. In alloy B. micro-cracks were formed in both the brittle intermetallic and coarse Si phasese. These micro-cracks then coalesced together and provided a path for fatigue crack propagation. From the observation of the differences in microstructure and fractography of these two automotive alloys, the authors attempt to explain the high-temperature fatigue deformation behavior of heat resistant aluminum alloys.

Hot Corrosion Properties of Heat Resistant Chrome Steels (내열강의 고온부식특성에 대한 크롬함량의 영향)

  • Lee, Han-sang;Jung, Jine-sung;Yoo, Keun-bong;Kim, Eui-hyun
    • Korean Journal of Metals and Materials
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    • v.48 no.4
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    • pp.277-288
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    • 2010
  • The hot corrosion properties of heat-resistant steels were investigated in an oxidation atmosphere including artificial ash and sulfur dioxide. The heat-resistant steels of T22, T92, T122, T347HFG, Super304H and HR3C were evaluated at 620, 670 and $720^{\circ}C$ for 400 hours. The relationship between the corrosion rate and the temperature followed a bell-shaped curve with a peak rate at around $670^{\circ}C$. The corrosion rates showed a decreasing tendency as the chrome contents of these steels increased from 2.15 wt.% to 24.5 wt.%, and austenitic steels had a lower corrosion rate than ferritic steels. Sulfidation by $SO_2$ as well as molten salt corrosion also had an effect on the total corrosion rate, especially showing an increase in the corrosion rate in ferritic steels. Regardless of the chrome content in the steels and irrespective of the test temperature, the corrosion scale was composed of an outer oxide and an artificial ash mixed layer, a middle oxide layer and inner sulfide, and a mixed oxide layer. As the chrome content increased, the proportion of chrome oxide in the corrosion scale increased. Before spalling of the corrosion scale, voids and cracks were initiated in the sulfide and the mixed oxide layer or at the interface with the substrate.

Effect of Sb and Sr Addition on Corrosion Properties of Mg-5Al-2Si Alloy (Mg-5Al-2Si 합금의 조직 및 부식특성에 미치는 Sb, Sr 첨가의 영향)

  • Jeon, Jongjin;Lee, Sangwon;Kim, Byeongho;Park, Bonggyu;Park, Yongho;Park, Ikmin
    • Korean Journal of Metals and Materials
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    • v.46 no.5
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    • pp.304-309
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    • 2008
  • Magnesium alloys containing $Mg_2Si$ particles, as a promising cheap heat-resistant magnesium alloy for automobile power train parts applications, are attracting more attention of both material scientists and design engineers. Modification of the Chinese script shape $Mg_2Si$ particle is a key for using this alloy in sand or permanent mould casting. In the present work, the modification effect of Sr and Sb on the corrosion properties of the Mg-5Al-2Si alloy was investigated. Sr or Sb addition promoted the formation of fine polygonal shape $Mg_2Si$ particles by providing the nucleation sites. Sr was more effective element than Sb for shape modification of Chinese script shape $Mg_2Si$. Such improved microstructure of the modified alloy resulted in large improvement in corrosion resistance as compared to unmodified Mg-5Al-2Si alloy.

Endurance Life and Deformation Behavior under Thermo-mechanical Fatigue of Nb-added Heat Resistant Austenitic Stainless Steel (Nb 첨가 오스테나이트계 내열 스테인리스강의 열기계적 피로 수명 및 변형 거동)

  • Oh, Yong Jun;Park, Joong-Cheul;Yang, Won Jon
    • Korean Journal of Metals and Materials
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    • v.49 no.7
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    • pp.541-548
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    • 2011
  • Thermomechanical fatigue (TMF) behavior of heat resistant austenitic stainless steel was evaluated in the temperature range from 100$^{\circ}C$ to peak temperatures of 600 to 800$^{\circ}C$; The fatigue lives under TMF conditions were plotted against the plastic strain range and the dissipated energy per cycle. In the expression of the inelastic strain range versus fatigue life, the TMF data obtained at different temperature ranges were located close to a single line with a small deviation; however, when the dissipated energy per cycle, calculated from the area of the stress-strain hysteresis loops at the half of the fatigue life, was plotted against the fatigue life, the data showed greater scattering than the TMF life against the inelastic strain range. A noticeable stress relaxation in the stress-strain hysteresis curve took place at the peak temperatures higher than 700$^{\circ}C$, but all specimens in this study exhibited cyclic hardening behavior with TMF cycles. Recrystallization occurred during the TMF cycle concurrent with the formation of fine subgrains in the recrystallized region, which is considered to cause the cyclic hardening of the steel.

Hard, Wear Resistant Metal Surfaces for Industrial Applications through Laser Powder Deposition

  • Sears, James;Costello, Aaron
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • pp.293-294
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    • 2006
  • Laser Powder Deposition (LPD) is a technology capable of modifying a metallic structure by adding the appropriate material to perform a desired function. LPD offers a unique fabrication technique that allows the use of soft (tough) materials as base structures. Through LPD a hard material can be applied to the base material with little thermal input (minimal dilution and heat-affected-zone {HAZ}), thus providing the function of a heat treatment or other surface modifications. These surface modifications have been evaluated through standard wear testing (ASTM G-65), surface hardness (Rc), micro-hardness (vickers), and optical microscopy.

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A Study on Heat Generation and Machining Accuracy According to Material of Ultra-precision Machining (초정밀가공의 재질에 따른 발열과 가공정밀도에 관한 연구)

  • Lee, Gyung-Il;Kim, Jae-Yeol
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.17 no.1
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    • pp.63-68
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    • 2018
  • At present, ultra-precision cutting technology has been studied in Korean research institutes, focusing on development of ultra-precision cutting tool technology and ultra-precision control engineering. However, the developed technologies are still far behind advanced countries. It focuses on metals including aluminum, copper and nickel, and nonmetals including plastics, silicone and germanium which require high precision while using a lathe. It is hard to implement high precision by grinding the aforementioned materials. To address the issue, the ultra-precision cutting technology has been developing by using ultra-precision machine tools very accurate and strong, and diamond tools highly abrasion-resistant. To address this issue, this study aims to conduct ultra-precision cutting by using ECTS (Error Compensation Tool Servo) to improve motion precision of elements and components, and compensate for motion errors in real time. An IR camera is used for analyzing cutting accuracy differences depending on the heat generated in diamond tools in cutting to examine the heat generated in cutting to study cutting accuracy depending on generated heat.

Welding Characteristics of Lap-Joint Hastelloy C-276 Sheet Metal Using Nd:YAG Laser (Nd:YAG 레이저를 이용한 하스텔로이 박판의 겹치기 이음 용접 특성)

  • Kim, Chan Kyu;Jung, Yoon Gyo;Cho, Young Tae
    • Journal of the Korean Society for Precision Engineering
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    • v.32 no.8
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    • pp.681-685
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    • 2015
  • Hastelloy C-276 composed of Cr, Mo, and Ni is a versatile, corrosion-resistant alloy with numerous industrial applications including its use in nuclear reactors, general chemical plants, and as a superconducting base material. Of especial significance, it can be used as a thin-sheet type whereby lap-joint welding is occasionally necessary. The main welding problems for thin-sheet metals are deformation and burn-through from an excessive heat input. Laser welding can minimize these problems because it has a high energy density and low heat effect on the base material. In this study, the laser-welding characteristics of lap-joint Hastelloy C-276 sheet metal were determined. The criteria of the laser-welding variables were chosen using a heat-conduction analysis, and the optimal welding parameters were selected by experimenting with an Nd:YAG laser.