• Title, Summary, Keyword: heat treatment

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Effects of Vacuum Heat Treatment and Salt bath Heat Treatment Conditions on Mechanical Properties of High Speed tool Steel (금속도 공구강의 기계적 성질에 미치는 진공열처리와 염욕열처리 조건의 영향)

  • Kim, Je-Don;Kim, Kyung-Sik
    • Journal of the Korean Society for Heat Treatment
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    • v.26 no.1
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    • pp.7-13
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    • 2013
  • Vacuum heat treatment(indirect heating method) has long exposure time at high temperature and low quenching rate. Contrarily salt bath heat treatment (direct heating method) has short exposure time at high temperature and fast cooling rate. With these different features of processes, mechanical properties such as hardness, tensile strength and impact strength of products show very different results. In this study, Salt bath heat treated products showed higher tensile strength and impact strength than vacuum heat treated products but hardness was not much different. These lower mechanical properties of vacuum heat treated products are due to differences in heat process and secondary hardening with high temperature tempering process. Consequently, It indicates that salt bath heat treatment is better way than vacuum heat treatment for product to have high mechanical properties.

Effects of Heat Treatment and Rest-inserted Exercise on Muscle Activity

  • Bang Jae-Kyun;Hwang Sung-Jae;Kim Chi-Hyun
    • Journal of Biomedical Engineering Research
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    • v.27 no.2
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    • pp.73-77
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    • 2006
  • Prolonged immobilization leads to significant weakness and atrophy of the skeletal muscle and can also impair the recovery of muscle strength following injury. Therefore, it is important to minimize the period under immobilization and accelerate the return to normal activity. This study examined the effects of combined heat treatment and rest-inserted exercise on the muscle activity of the lower limb during knee flexion/extension. Twelve healthy subjects were assigned to 4 groups that included: (1) heat treatment + rest-inserted exercise; (2) heat treatment + continuous exercise; (3) no heat treatment + rest-inserted exercise; and (4) no heat treatment + continuous exercise. Heat treatment was applied for 15 mins prior to exercise. Continuous exercise groups performed knee flexion/extension at 0.5 Hz for 300 cycles without rest whereas rest-inserted exercise groups performed the same exercise but with 2 mins rest inserted every 60 cycles of continuous exercise. Changes in the rectus femoris and hamstring muscle activities were assessed at 0 and 2 weeks of treatment by measuring the electromyography signals of isokinetic maximum voluntary contraction. Significant increases in both the rectus femoris and hamstring muscles were observed after only 2 weeks of treatment when both heat treatment and rest-inserted exercise were performed. These results suggest that combination of various treatment techniques, such as heat treatment and rest-inserted exercise, may accelerate the recovery of muscle strength following injury or immobilization.

Effect of Vacuum Heat Treatment and Salt Bath Heat Treatment Conditions on Mechanical Properties of Hot Work Die Steel (열간 금형강의 기계적 성질에 미치는 진공열처리와 염욕열처리 조건의 영향)

  • Kim, Je-Don;Kim, Kyung-sik;Park, Ki-Ho
    • Journal of the Korea Society of Die & Mold Engineering
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    • v.8 no.2
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    • pp.23-29
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    • 2014
  • Salt bath heat treatment is usually used but recently vacuum heat treatment is increased for the heat treatment of hot work die steels. The differences in two heat treatment processes were compared by testing the mechanical properties of heat treated products. With two different features of processes, mechanical properties such as hardness, tensile strength and impact strength of products show very different results. In this study salt bath heat treated products showed higher tensile strength and impact strength than vacuum heat treated products but hardness was not much different. These lower mechanical properties of vacuum heat treated products are due to differences in heating and quenching process.

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The Effects of Cyclic Heat Treatment Process for Fine Microstructure of TiAl Cast Alloy (주조용 TiAl 합금의 조직 미세화를 위한 반복열처리 공정 조건에 관한 연구)

  • Kong, Man-Sik;Yang, Hyunseok
    • Journal of the Korean Society for Heat Treatment
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    • v.32 no.5
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    • pp.195-200
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    • 2019
  • For expanding the applications and workability of TiAl alloy, elongation is very important property. Fine microstructure is needed for elongation and physical properties of TiAl alloys. In this study, The effects of cyclic heat treatment process for fine microstructure of Ti-46Al-Nb-W-Cr-Si-C alloy, which was made by VAR (vacuum arc remelting) and VIM(vacuum induction melting) centrifugal casting process, was investigated. Cycle heat treatment process was very effective for recrystallization of this TiAl system, which has microstructure size of $50{\sim}100{\mu}m$ through pre-heat treatment, cyclic heat treatment in ${\alpha}+{\gamma}$ phase region and solution heat treatment respectively. Refined grain size was finally confirmed by photos of optical microscope and scanning electron microscope.

The Effect of Heat Treatment on Biological Response and Mutation Frequency of Gamma Irradiated Rice Seeds (수도종자의 방사선조사에 있어서 열처리의 효과)

  • Chang-Yawl Harn;J. L.Won;Kwang-Tae Choi
    • KOREAN JOURNAL OF CROP SCIENCE
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    • v.10
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    • pp.45-50
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    • 1971
  • For the purpose of finding out the effect of heat treatment on biological response and mutation rate, rice seeds were heat treated before and after gamma irradiation. 1. At a dose of 20 KR, pre-irradiation heat treatment showed reduced biological damage and increased mutation rate as compared with non-heat treatment. 2. Mutation frequency was increased in post-treatment of heat shock than in pre-irradiation heat treatment and non-heat treatment. 3. Pre-irradiation heat treatment at 6$0^{\circ}C$ for 30 minutes markedly reduced the biological damage and increased the mutation rate. 4. Mutation spectrum in heat treatment was different from non-treatment.

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EFFECTS OF LOW-TEMPERATURE HEAT TREATMENT ON ELASTIC MEMORY PROCESS OF COLD WORKED STAINLESS STEEL WIRE (열처리가 냉간가공한 stainless steel wire의 복원양상에 미치는 영향)

  • Oh, Jeung-Sei;Park, Soo-Byung;Son, Woo-Sung
    • The korean journal of orthodontics
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    • v.22 no.3
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    • pp.647-656
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    • 1992
  • The purpose of this study was to evaluate the elastic memory process in cold worked stainless steel wire and the effect of heat treatment on it. 0.018 inch round and $0.019\times0.025$ inch rectangular wire (ORMCO stainless wire) were used in this study. Each wire type had 4 groups: non-heat treatment group, furnace heat treatment group, electric current heat treatment group, and bending after heat treatment group. Each group was consisted of 10 specimens. With the Jig, each wire was bent into v-shape uniformly, and width of two free ends of each v-shaped wire was measured by caliper (to the point of 0.1 mm correctly) at time interval of offjig, after heat treatment, 1, 2, 3, 4 hours, 1, 2, 3, 4, 5, 6 days, 1, 2, 3, 4 weeks after. The results were as follows: 1. In non-heat treatment group and bending after heat treatment group, elastic memory process was occured $60\%$ within 1 hour, and more than $90\%$ within 1 week. 2. In furnace and electric current heat treatment group, almost all elastic memory process was occured during teat treatment, and then specimen was stabilized dimensionally. 3. Magnitude of deformation by elastic memory was greater in heat treatment group than non heat treatment group and bending after heat treatment group. 4. There was no remarkable difference in deformation pattern between 0.018 inch round wire and $0.019\times0.025$ inch rectangular wire.

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Improving the Dimensional Stability of Spruce and Birch Boards by Heat-Treatment at 190 and $210^{\circ}C$

  • Kang, Ho-Yang
    • Journal of the Korea Furniture Society
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    • v.20 no.6
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    • pp.560-565
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    • 2009
  • It is known that heat treatment decreases the hygroscopicity of wood. Thus heat-treated wood is good for outdoor construction due to its improved dimensional stability. This study is to investigate the hygroscopicity and discoloration of spruce and birch boards heat-treated above $190^{\circ}C$. The equilibrium moisture contents (EMCs) at all relative humidities decreased with the increase of heat treatment temperature and/or time for both spruce and birch. It was revealed that heat-treatment temperature affected more on the hygroscopicity thaan heat-treatment time. The average basic densities decreased for the spruce specimens, but increased for the birch specimens with an increase of the treatment time and/or temperature. The same heat treatment condition (190-8) made the birch specimens darker than the spruce specimens.

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Effects of Heat Treatment on the Dietary Fiber Contents of Soybean sprout and Spinach (가열처리에 의한 콩나물과 시금치의 식이섬유 함량변화)

  • Lee, Eun-Young;Kim, Young-A
    • Korean journal of food and cookery science
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    • v.10 no.4
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    • pp.381-385
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    • 1994
  • The dietary fiber contents of soybean sprout and spinach were changed by heat treatment. Before heat treatment, soybean sprout and spinach had larger amount of insoluble dietary fiber than soluble, and similar proportions of insoluble v/s soluble dietary fibers. After heat treatment, the value of insoluble dietary fiber of soybean sprout and spinach was increased significantly, except for microwave heating short time treatment. It is believed that the increment of insoluble dietary fiber is due to Maillard reaction products and resistant starch after heat treatment. The change of soluble dietary fiber contents of soybean sprout and spinach were not consistent in heat treatment. It is supposed that some soluble dietary fiber was destroyed by heat treatment, and some insoluble dietary fiber was hydrolysed or destroyed to be soluble. Total dietary fiber of soybean sprout and spinach was significantly incereased by all heat treatment, except for microwave heating short time of spinach.

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