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우기도,박영구,김석원,진영철,류재화,나종필 ( K . D . Woo,Y . K . Park,K . W . Kim,Y . C . Jin,J . H . Ryu,J . P . Ra ) 한국열처리공학회 1998 熱處理工學會誌 Vol.11 No.2
N/A The graphitization is affected by the addition of small amount of the elements, such as Si, Al, Ni, B, Cr and Mn etc. Boron is well known as the most effective element for the graphitization of cementite in high carbon steels. But a study on quantitative analysis of B effect on the graphitization is few reported. Therefore the effect of boron addition in Fe-0.65%C-1.0%Si-0.5%Mn steels on the graphitization is investigated quantitatively using hardness tester, optical microscope and scanning electron microscope, neutron induced microscopic radiography. The graphitization in high carbon steels is promoted with 0.003∼0.005%B addition. But the graphitization in steels which has no boron takes long holding time at 680∼720℃. The hardness of quenched steel containing 0.003%B is higher than that of 0.005%B added steel due to complete dissolution of fine graphites into the austenite. The 0.003%B added high carbon steel graphitized at 680℃ for 25hr is useful steel for the agricultural implements and automobile parts which needed a good formability and high hardness.
Cu-25 Ni 합금의 주기적 크리프시 관찰되는 변형돌발 현상에 대한 고찰
남수우,류재화 대한금속재료학회(대한금속학회) 1985 대한금속·재료학회지 Vol.23 No.11
The phenomenon of strain burst is observed in Cu-25Ni alloy subjected to cyclic creep at intermediate temperature (0.45-0.55 Tm) and high stress however in static creep under the same condition, strain burst is never occurred. The purpose of this work is to study the tendency and mechanism of the strain burst. Strain bursts occur frequently as the temperature and stress are increased, but at low stresses or high temperatures the strain burst is not observed. The strain burst can be seemingly explained as follows: in cyclic creep the localized dislocation network spacing growth is occurred by recovery during cyclic unloading, on reloading instantaneous large increase in mobile dislocation density caused by destruction of grown dislocation network spacing results in strain burst.
박영구,우기도,이창희,류재화,나종필 한국열처리공학회 1999 熱處理工學會誌 Vol.12 No.2
The graphitization is affected by the addition of small amount of the elements(such as Si, Al, Ni, B, Cr and Mn etc.) and the pre-treatment(such as cold rolling). Boron is well known element to accelerate the graphitization of cementite in high carbon steels. Also, cold rolling is known to accelerate the graphitization. But the graphitization nucleation mechanism by cold rolling is few reported. Therefore the effect of cold rolling in Fe-0.5%C-1.0%Si-0.47%Mn-0.005%B steel on the graphitization is investigated quantitatively using hardness test, optical microscope and scanning electron microscope, neutron induced microscopic radiography. The nucleation of graphite in cold-rolled Fe-0.5%C-1.0%Si-0.47%Mn-0.005%B steel is formed at void which is formed at pearlite/pearlite boundary by cold rolling. But the effect of cold rolling on graphitization in boron addition steel is more effective than that of no boron addition steel due to segregation of BN at void in boron addition steel.