• Title, Summary, Keyword: heat treatment

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Effect of heat treatment residual stress on stress behavior of constant stress beam

  • Kwak, Si Young;Hwang, Ho Young
    • Journal of Computational Design and Engineering
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    • v.5 no.1
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    • pp.137-143
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    • 2018
  • Although most casting and heat treatment processes generate significantly high residual stress in the products, this factor is generally not taken into account in the design stage of the product. In this study, experimental study and numerical analysis were conducted on a constant stress beam to examine effects of the residual stress generated during the heat treatment process on yielding behavior of the product in use. A constant stress beam of SUS 304 was designed in order to test the stress behavior related to residual stress. The residual stresses generated during quenching heat treatment of the beam were measured in advance by ESPI (Electronic Speckle-Pattern Interferometry) equipment, and then the external stresses generated while applying a simple external load on the beam were measured. Also, the residual stress distribution generated during the heat treatment process was computed using a numerical analysis program designed for analyzing heat treatment processes. Then, the stress distribution by a simple external load to the beam was combined with the calculated residual stress results of the previous heat treatment step. Finally, the results were compared with experimental ones. Simulation results were in good agreement with the experimental results. Consistency between experimental results and computational results prove that residual stress has significant effects on the stress behavior of mechanical parts. Therefore, the residual stress generated in the previous heat treatment step of casting must be taken into account in the stage of mechanical product design.

Enhanced Virus Safety of a Solvent/Detergent-Treated Anti-hemophilic Factor IX Concentrate by Dry-Heat Treatment

  • Shin Jeong-Sup;Choi Yong-Woon;Sung Hark-Mo;Ryu Yeon-Woo;Kim In-Seop
    • Biotechnology and Bioprocess Engineering:BBE
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    • v.11 no.1
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    • pp.19-25
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    • 2006
  • With particular regards to the hepatitis A virus (HAV), a terminal dry-heat treatment ($100^{\circ}C$ for 30 min) process, following lyophilization, was developed to improve the virus safety of a solvent/detergent-treated antihemophilic factor IX concentrate. The loss of factor IX activity during dry-heat treatment was of about 3%, as estimated by a clotting assay. No substantial changes were observed in the physical and biochemical characteristics of the dry-heat-treated factor IX compared with those of the factor IX before dry-heat treatment. The dry-heat-treated factor IX was stable for up to 24 months at $4^{\circ}C$, The dry-heat treatment after lyophilization was an effective process for inactivating viruses. The HAV and murine encephalomyocarditis virus (EMCV) were completely inactivated to below detectable levels within 10 min of the dry-heat treatment. Porcine parvovirus (PPV) and bovine herpes virus (BHV) were potentially sensitive to the treatment. The log reduction factors achieved during lyophilization and dry-heat treatment were ${\ge}5.60$ for HAV, ${\ge}6.08$ for EMCV, 2.64 for PPV, and 3.59 for BHV. These results indicate that dry-heat treatment improves the virus safety of factor IX concentrates, without destroying the activity. Moreover, the treatment represents an effective measure for the inactivation of non-lipid enveloped viruses, in particular HAV, which is resistant to solvent/detergent treatment.

Heat Treatment of Superalloys for High Temperature Applications (고온구조용 초내열합금 열처리)

  • Park, Nho-Kwang
    • Journal of the Korean Society for Heat Treatment
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    • v.16 no.6
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    • pp.341-348
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    • 2003
  • Superalloys which can be devided into three categohes, i.e. Ni-base, Co-base, and Fe-base alloys are widely used for high temperature applications. Since superalloys contain many alloying elements and precipitates, its chemistry and processing parameters need to be carefully designed. In this review, current state-of-the art in the superalloy technologies is described with special attention to the heat-treatment for the control of the microstructures and mechanical properties.

Combined Heat Treatment Characteristics of Cast Iron for Mold Materials (금형재료용 주철강의 복합열처리 특성)

  • Hwang, Hyun-Tae;So, Sang-Woo;Kim, Jong-Do
    • Korean Journal of Materials Research
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    • v.21 no.7
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    • pp.364-370
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    • 2011
  • Currently, there are two main issues regarding the development of core technologies in the automotive industry: the development of environmentally friendly vehicles and securing a high level of safety in the event of an accident. As part of the efforts to address these issues, research into alternative materials and new car body manufacturing and assembly technologies is necessary, and this has been carried out mainly by the automotive industries. Large press molds for producing car body parts are made of cast iron. With the increase of automobile production and various changes of design, the press forming process of car body parts has become more difficult. In the case of large press molds, high hardness and abrasive resistance are needed. To overcome these problems, we attempted to develop a combined heat treatment process consisting of local laser heat treatment followed by plasma nitriding, and evaluated the characteristics of the proposed heat treatment method. From the results of the experiments, it has been shown that the maximum surface hardness is 864 Hv by the laser heat treatment, 953 Hv by the plasma nitriding, and 1,094 Hv by the combined heat treatment. It is anticipated that the suggested combined heat treatment can be used to evaluate the durability of press mold.

Study for Heat Treatment Optimization of Titanium Hollow Casted Billet (타이타늄 중공마더빌렛 주조재의 열처리공정 최적화 연구)

  • Youn, Chang-Suk;Park, Yang-Kyun;Lee, Hyung-Wook;Lee, Dong-Geun
    • Journal of the Korean Society for Heat Treatment
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    • v.32 no.2
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    • pp.68-73
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    • 2019
  • ${\alpha}$-titanium alloy has a relatively low heat treatment characteristic and it is mainly subjected to heat treatment for residual stress, recovery or dynamic recrystallization. In this study, commercially pure titanium hollow castings was fabricated by gravity casting. Heat treatments were carried out at $750^{\circ}C$, $850^{\circ}C$ and $950^{\circ}C$ to investigate the effect of post-heat treatment on microstructure and mechanical properties. Beta-transus temperature ($T_{\beta}$) was about $913^{\circ}C$, and equiaxed microstructure was shown at temperature below $T_{\beta}$ and lath-type microstructure at temperature above $T_{\beta}$. Microstructure and mechanical properties did not show any significant difference in the direction of solidification for titanium hollow billet, so it can be seen that it was a well-made material for extrusion process. The optimum heat treatment condition of hollow billet castings for the seamless tube production was $850^{\circ}C$, 4 hr, FC, indicating a combination of equiaxed microstructure and appropriate mechanical properties.

A Study on Heat Treatment for Improving Cold Forgeability of a Bearing Steel, SUJ2 (베어링강 SUJ2의 냉간 단조성 향상을 위한 열처리에 관한 연구)

  • Kim, Hae-Ji
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.8 no.1
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    • pp.24-30
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    • 2009
  • In this paper, the effect of heat treatment on forgeability is investigated and an improved heat treatment cycle is proposed for the bearing steel, SUJ2. An application example of a bearing inner race cold forging, which has small cracks in the bottom after backward extrusion and piercing, is found from a cold forging industry. The process is evaluated by finite element analysis and several heat treatment cycles are examined in order to propose an improved heat treatment cycle. The effect of heat treatment on material hardness and tool life, dimensional accuracy and forming load is revealed through experiment.

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Effects of the Non-equilibrium Heat-treatment on Modification of Microstructures of Al-Si-Cu Cast Alloy (비평형 열처리에 의한 주조용 Al-Si-Cu합금 조직의 개량 효과)

  • Kim, Heon-Joo
    • Journal of the Korean Society for Heat Treatment
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    • v.13 no.6
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    • pp.391-397
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    • 2000
  • Addition of Ca element and nonequilibrium heat treatment which promotes shape modification of eutectic Si and ${\beta}$ intermetallic compound were conducted to improve the mechanical properties of Al-Si-Cu alloy. Modification of eutectic Si and dissolution of needle-shape ${\beta}$ intermetallic compounds were possible by nonequilibrium heat treatment in which specimens were held at $505^{\circ}C$ for 2 hours in Al-Si-Cu alloy with Fe. Owing to the decrease in aspect ratio of eutectic Si by the heat treatment of the alloy with 0.33wt.% Fe, the increase in elongation was prominent to be more than double that in the as-cast specimen. Dissolution of needle-shape ${\beta}$ intermetallic compounds in the alloy with 0.85wt.% Fe led to the improvement of tensile strength as the length of ${\beta}$ compounds decreased to 50%.

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Effect of Heat Treatment on the Surface Machined by W-EDM (고온 열처리가 와이어 컷 가공면에 미치는 영향)

  • Choi, K.K.;Lee, Y.S.
    • Transactions of Materials Processing
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    • v.15 no.8
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    • pp.539-543
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    • 2006
  • Experimental studies are carried out in order to investigate the effects of heat treatment on the surface machined by W-EDM. In this work, two ways of heat treatment after W-EDM are considered. As a comparison, the machined surface by a traditional method such as milling/grinding is also considered. Thereby, specimens are prepared by four different machining methods. Those are (1) milling and then grinding, (2) wire-cut electric discharge machining (W-EDM), and (3) low temperature heat treatment or (4) high temperature heat treatment after W-EDM. The resulting surface roughness are measured and the changes of surface microstructures are investigated using the scanning electron microscope (SEM) with energy dispersive X-ray spectrometer (EDS). In general, heat treatment after W-EDM result in smoother surface and better chemical composition at the machined surface. Especially, high temperature tempering could remove defects in the thermally affected zone, which cause an overall deterioration of the surface machined by W-EDM.

Barkhausen Noise Characteristics of 3Cr-1Mo Steel with Heat-treatment (열처리에 따른 3Cr-1Mo강의 Barkhausen noise 특성)

  • Nam, Young-Hyun
    • Journal of the Korean Society for Heat Treatment
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    • v.21 no.4
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    • pp.199-204
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    • 2008
  • The destructive method is reliable and widely used for evaluating the properties of material but it is time-consuming and difficult to prepare specimens from in-service industrial facilities. In the present research, Barkhausen Noise (BN) has been used to evaluate changes of mechanical properties due to heat treatment condition. The BN voltage (rms voltage) was measured with grain size. The rms voltage of BN increased with the heat treatment temperature ($870{\sim}1000^{\circ}C$) because the grain size increased with the temperature. The rms voltage of BN decreased with various heat treatment processes, such as quenched, tempered and PWHT. The BN can be used for the nondestructive evaluation of the forged reactor vessels. and moreover, it may be effectively used in the field application.

The Microstructure Changes of Continuous Cast iron Rods According to the Heat-Treatment Conditions (열처리 조건에 따른 주철연속주조봉의 미세조직 변화)

  • Kim, Tae-Bong;Kim, Seon-Hwa;Park, Sang-Jun
    • Journal of Korea Foundry Society
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    • v.20 no.3
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    • pp.173-180
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    • 2000
  • The microstructure changes of the matrix and the graphites were observed by optical microscope and the average hardness number was investigated according to the heat-treatment conditions of the cast iron rods by the horizontal continuous casting process in 35 mm diameter. The three kinds of heat-treatments were introduced. The first treatment was performed at 900, 950, and $1000^{\circ}C$ for 2 hours and the second treatment was conducted during 5, 10, and 15 hours at $1000^{\circ}C$ respectively. The third treatments were the two-cyclic heat-treatment and the three-cyclic heat-treatment at $1000^{\circ}C$ during 2 hours. The matrix microstructure of the specimens to be treated at various temperatures for 2 hours was the ferrite to be transformed from the pearlite The hardness number of the center of the samples according to the heat treatment time at $1000^{\circ}C$ was higher than that of the surface area because of the martensite formation in the center. Also, in the cyclic heat-treatments, the hardness number of the two-cycle treatment specimens increased because of the martensite formation in the center.

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