• Title, Summary, Keyword: heat-aging

Search Result 521, Processing Time 0.036 seconds

Effect of Aging Treatment on the Mechanical Properties and Damping Capacity of 12Cr Heat Resistant Steel with Ferrite Phase (페라이트 상을 갖는 12Cr 내열강의 기계적성질 및 감쇠능에 미치는 시효처리의 영향)

  • Kang, C.Y.;Choi, H.G.;Park, H.K.;Sung, J.H.;Lee, D.H.
    • Journal of the Korean Society for Heat Treatment
    • /
    • v.24 no.1
    • /
    • pp.23-30
    • /
    • 2011
  • This study was carried out to investigate the effect of aging treatment on the mechanical properties and damping capacity of 12Cr heat resistant steel with ferrite phase. While hardness values in ferrite phase was not changed, that in martensite phase was dramatically dropped in early stage of aging treatment and then gradually decreased with increase of aging time. As aging treatment was carried out, the precipitation was not detected in ferrite phase, while carbides were precipitated in martensite phase. With increasing the aging time, tensile strength eventually decreased while impact toughness increased rapidly in the early stage of aging and then gradually increased. Besides, it was confirmed that damping capacity was not changed in the early stage of aging and then gradually increased with increase of aging time.

Effect of Heat Treatments on Welding Residual Stresses of 18% Ni Maraging Steel (18% Ni 마레이징강의 용접 잔류 응력에 미치는 열처리의 영향)

  • 배강열;나석주;김원훈
    • Journal of Welding and Joining
    • /
    • v.11 no.2
    • /
    • pp.53-61
    • /
    • 1993
  • One of the most interesting and promising steel groups considered for the rocket motor case, aircraft and aerospace component is the maraging(martensitic plus aging) nickel steel, developed by International Nickel Company in 1960. This material attains a very high strength with good fracture toughness by simple heat treatments which do not involve a quenching. Full strength can be obtained by "maraging" at 480.deg. for 3 hours for the 18% Ni maraging steel. The effect of heat treatments was considered on the residual stress field of 18% Ni maraging steel weldments. In experiments, various heat treatments such as stress relieve heat treatment, aging and solution heat treatment were carried out of the GTA weldments and the residual stresses were measured by using the hole drilling method. Whereas the conventional pattern of residual stress shows the stresses to be maximum along the weld centerline with tensile stress extending into the heat affected zone, the pattern in maraging steels shows the centerline stress to be compressive. After welding, a series of aging, solution heat treatment and solution heat treatment plus aging treatment were carried out and the residual stresses were measured to reveal that these heat treatments almost completely remove the welding residual stresses.

  • PDF

Microstructural Development of Ferritic 11Cr-3.45W Heat-resistance Steel for Ultra-supercritical Power Plant During Creep and Thermal Aging (크리프와 등온열화에 따른 초초임계압 발전설비용 페라이트계 11Cr-3.45W 내열합금강의 미세조직 변화)

  • Kim, Chung-Seok
    • Journal of the Korean Society for Heat Treatment
    • /
    • v.31 no.3
    • /
    • pp.91-96
    • /
    • 2018
  • Microstructural development of ferritic 11Cr-3.45W heat-resistance steel for ultra-supercritical power plant during creep and thermal aging was investigated using electron microscopy. The test samples were isothermally aged at $700^{\circ}C$ for up to 4000 hours and subjected to creep loading at $700^{\circ}C$ for predetermined periods of lifetime to prepare the damaged materials. In this structural material, a various secondary phases are the primary influence on mechanical properties of ferritic heat-resistance steel. The typical precipitates of $M_{23}C_6$, MX and $M_2X$ secondary phases had been analyzed through qualitative and quantitative manner. Coarsening of precipitates and increase of lath width were observed during creep and thermal aging. This phenomenon was remarkable for creep process compared with isothermal aging process.

Aging Treatment Optimization of Ti-3Al-8V-6Cr-4Mo-4Zr Alloy for Spring Application (스프링용 Ti-3Al-8V-6Cr-4Mo-4Zr 타이타늄 합금의 시효열처리 최적화)

  • Youn, Chang-Suk;Park, Yang-Kyun;Kim, Jong-Hyung;Lee, Soo-Chang;Lee, Dong-Geun
    • Journal of the Korean Society for Heat Treatment
    • /
    • v.30 no.6
    • /
    • pp.279-284
    • /
    • 2017
  • Mechanical properties of titanium alloy can be improved by controlling microstructure through heat treatment. In this study, Ti-3Al-8V-6Cr-4Mo-4Zr metastable beta titanium alloy, was controlled for excellent mechanical property and sound formability through various high temperature heat treatment and aging conditions and the optimum heat treatment conditions were determined. The specimens were heat-treated at $950^{\circ}C$, followed by various aging treatments from $430^{\circ}C$ to $500^{\circ}C$ for 1 to 24 h. As aging temperature and holding time increased, hardness increased by ${\beta}^{\prime}$ phase formation and precipitation of secondary ${\alpha}$ phase in ${\beta}$ matrix. However, the optimum aging temperature and holding time for mechanical properties were at $450{\sim}470^{\circ}C$ for 8~16 hr. Hardness values of the specimen aged at $450^{\circ}C$ for 8 h were found to be the highest. These results can be effectively applied to fabrication of spring with better formability and mechanical property.

Influence of Variation of Aging Heat Treatment Condition on Phase Transformation and Mechanical Properties of 15-5PH Stainless Steel (15-5PH 스테인리스강의 시효열처리 조건변화가 상변태 및 기계적 성질에 미치는 영향)

  • Kim, T.S.;Lee, Jewon;Roh, Y.S.;Sung, J.H.;Lim, S.G.
    • Journal of the Korean Society for Heat Treatment
    • /
    • v.32 no.5
    • /
    • pp.212-223
    • /
    • 2019
  • This study is to investigate the relationship between microstructural factors and tensile properties after aging heat treatment of the 15-5PH stainless steel at the temperature range of $450^{\circ}C$, $500^{\circ}C$ and $550^{\circ}C$ for various time. For the aging time of 2 hours, hardness showed maximum at $450^{\circ}C$ and then decreased with increasing aging temperature. While, hardness decreased gradually during aging $450^{\circ}C$, $500^{\circ}C$ and $550^{\circ}C$ from 1 hour to 5 hours but the hardness nearly unchanged until the 100 hours after 5 hours aging. When aging at $450^{\circ}C$, Cu atoms preferentially aggregated at the prior austenite grain boundaries and martensite lath boundaries, and Cu concentration at those boundaries was nearly unchanged even after aging for 100 hours. Therefore it was suggested that the coherency is still maintained after 100 hours aging at $450^{\circ}C$. Aging at $500^{\circ}C$ and $550^{\circ}C$ results in an increase in the concentration of Ni at the martensite lath boundaries and prior austenite grain boundaries, resulting in the formation of reversed austenite. Especially, when aged at $550^{\circ}C$ for 100 hours, the concentration of Ni remarkably increased at those boundaries, and thus the microstructure of herring bone shape was appeared. Considering the migration of Ni atom to the lath boundaries and prior austenite grain boundaries, Ni atoms contributed greatly to the formation of reversed austenite. On the other hand, it was found that Cu atoms hardly moving to those boundaries may not be contributed to the formation of reversed austenite. When aging at $450^{\circ}C$, the coarsening of the precipitated Cu atoms proceeded very slowly with increasing aging time, therefore the decrease in strengths were small but the reduction area was considerably increased due to the softening of the matrix. At the aging temperature of $500^{\circ}C$ and $550^{\circ}C$, the strengths decreased and the elongation and reduction area increased due to the appearance of the reversed austenite. Especially, the increase of reduction area was remarkable.

Changes of Carbide Characteristics and Magnetic Properties in Artificially Aging Heat Treated 2.25CrMo Steel (경년열화 열처리된 2.25CrMo 강에서의 탄화물 특성 및 자기적 성질의 변화)

  • Byeon, Jal Won;Kwun, S.I.
    • Journal of the Korean Society for Heat Treatment
    • /
    • v.14 no.6
    • /
    • pp.323-329
    • /
    • 2001
  • Artificial aging was performed to simulate the microstructural degradation in 2.25CrMo steel arising from long time exposure at $540^{\circ}C$. The carbide morphologies were classified as acicular, pipe and globular type, and the number of carbides per unit area was measured for each type of carbides. The fine acicular carbides were found to diminish drastically in the initial stage of aging. An attempt was made to evaluate the microstructural degradation in artificially aging heat treated 2.25CrMo steel by the magnetic property measurements such as saturation magnetization, coercivity and remanence. The saturation magnetization showed no distinct trend with aging time. However, the coercivity and remanence were observed to decrease rapidly in initial 920 hours of aging time and then decrease slowly afterwards.

  • PDF

Ultrasonic Nondestructive Evaluation of Microstructural Degradation in Artificially Aging Heat Treated 2.25CrMo Steel (인공 열화 열처리된 2.25CrMo 강의 미세조직 변화에 대한 초음파 비파괴평가)

  • Byeon, Jai Won;Kwun, S.I.;Park, Un-Su;Park, Ik-Keun
    • Journal of the Korean Society for Heat Treatment
    • /
    • v.14 no.2
    • /
    • pp.110-117
    • /
    • 2001
  • Artificial aging was performed to simulate the microstructural degradation in 2.25CrMo steel arising from long time exposure at $540^{\circ}C$. It was found that the carbides became coarser and spheroidized as aging time increased. An attempt was made to evaluate the microstructural degradation in artificially aging heat treated 2.25CrMo steel by the ultrasonic attenuation and velocity measurements. Ultrasonic velocity was found essentially insensitive to the microstructural changes resulting from aging heat treatment. However, the ultrasonic attenuation was observed to increase with increasing aging time. Also, it was noticed that the change of ultrasonic attenuation with aging time was more sensitive at high frequency regions.

  • PDF

Multi-phase Accelerating Test Method of Thermal Aging Considering Heat Generation of Electric Equipment (전기기기의 발열을 고려한 다단계 가속열노화 방법)

  • Lim, Byung-Ju;Park, Chang-Dae;Chung, Kyung-Yul
    • The KSFM Journal of Fluid Machinery
    • /
    • v.16 no.5
    • /
    • pp.18-23
    • /
    • 2013
  • Thermal aging test is performed to qualify the life time of equipment in thermally aged condition. Due to long life time more than 10 years like as in power plant, the equipment is subjected to the accelerated thermal aging condition which is able to shorten the long aging test period by increasing aging temperature. Normally, conservatism of thermal aging test causes to impose unbalanced and excessive thermal load on components of the equipment, and deformation and damage problems of the components. Additionally, temperature rise of each component through heat generation of the electric equipment leads to long-term problem of the test period. Multi-phase accelerating aging test is to perform thermal aging test in multiple aging conditions after dividing into groups with various components of equipment. The groups might be classified considering various factors such as activation energy, temperature rise, glass transition temperature and melting temperature. In this study, we verify that the multi-phase accelerating aging test method can reduce and equalize the thermal over load of the components and shorten aging test time.

The Effects of Solution Heat Treatment and Aging Treatment on the Electrical Conductivity and Hardness of Cu-Cr Alloys (크롬동합금의 도전율과 경도에 미치는 용체화처리와 시효처리의 영향)

  • Kim, Shin Woo
    • Journal of the Korean Society for Heat Treatment
    • /
    • v.15 no.1
    • /
    • pp.21-24
    • /
    • 2002
  • The electrode materials for welding machine in automobile industry such as Cu-Cr, Cu-Zr and Cu-$Al_2O_3$ require the high electrical conductivity and the proper hardness. Therefore the effects of solution heat treatment and aging treatment on the electrical conductivity and hardness of Cu-0.8wt%Cr and Cu-1.2wt%Cr alloys have been investigated. Cu-0.8wt%Cr alloy showed the higher electrical conductivity and hardness than Cu-1.2wt%Cr alloy and both alloys showed the better electrical conductivity at $930^{\circ}C$ among 930, 980 and $1030^{\circ}C$ solution heat treatment temperatures. The electrical conductivity and hardness in both alloys were not affected by aging treatment but remarkably affected by solution heat treatment temperature. The final drawing process reduced electrical conductivity and increased hardness more in Cu-1.2wt%Cr alloy.

Hardness and Electrical Conductivity Changes according to Heat Treatment of Cu-1.6Co-0.38Si Alloy (Cu-1.6Co-0.38Si 합금의 열처리에 따른 경도 및 전기전도도의 변화)

  • Kwak, Wonshin;Lee, Sidam
    • Journal of the Korean Society for Heat Treatment
    • /
    • v.33 no.5
    • /
    • pp.226-231
    • /
    • 2020
  • The Cu-Co-Si alloy shows high strength by forming precipitates by aging precipitation heat treatment of supersaturated solid solution treated with solution treatment such as Cu-Ni-Si alloy, and the Co2Si precipitated phase is dispersed in the copper matrix. The effect of aging treatment on the microstructure, mechanical and electrical properties of Cu-Co-Si alloys for electronic devices was investigated. As a results of SEM/EDS analysis, it was found that Co2Si precipitates of 30~300 nm size were distributed in grains. By performing the double aging treatment, it was possible to improve the strength and electrical conductivity by dispersing the fine precipitate evenly.