熱サイクル後の炭素鋼の強度および疲労に及ぼす非金属介在物の影響について

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We have investigated on the changes in dimension, hardness, ultrasonic attenuation and micro-structure of three kinds of carbon steel (E,D and J) having different amounts of non-metallic inclusion MnS during simple thermal cycling between 720℃ and 50℃, and further, carried out the same studies on armco iron. The results were as follows : 1) The sample E which contains a small amount of inclusion elongated in the longitudinal direction, but the samples D and J with higher quantities of the inclusion contracted after thermal cycling. On the other hand, their diameters were found to expand regardless of inclusion quantities. Therefore, some decrease in specific gravity has taken place in all samples. 2) The changes in hardness, grain size and ultrasonic attenuation mostly occurred during the period of 50 cycles. 3) The changes in hardness, grain size and ultrasonic attenuation in all samples which were subjected to isothermal annealing for 310 hrs at 720℃ have the same tendency with the case of thermal cycling, but the dimensional change could not be recognized. 4) The dimensional change in armco iron was small compared with the sample E, but plastic deformation and formation of sub-grain due to thermal stress was clearly observed. The anomalous changes in dimension and mechanical properties are supposed to be caused by reason of that the concentration of the thermal stress at the boundary regions between grain and inclusion induced by heating and cooling has brought about some plastic deformation, which results to the origin of crack or various defects. The behavior of materials bearing inclusion are influenced by the form, properties, size and distribution of the inclusion. Furthermore, the chemical and physical reaction between base metal and inclusion is to be accelerated by thermal stress, and consequently, various anomalous phenomena might be appeared.
1961-03-15

熱サイクル後の炭素鋼の強度および疲労に及ぼす非金属介在物の影響について

スポンサーリンク

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