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Mo계 고속도 공구강의 오스템퍼링에 따른 기계적 성질에 관한 연구
최문성,이해우,노용식,김영희,김한군,이상윤 ( M . S . Choi,H . W . Lee,Y . S . Rho,Y . H . Kim,H . G . Kim,S . Y . Lee ) 한국열처리공학회 1991 熱處理工學會誌 Vol.4 No.1
This study has been performed to find out the effect of austenitizing temperature, austempering temperature and its holding time, and tempering cycle on the mechanical properties such as impact resistance, hardness etc. of AISI M₂Mo series high speed tool steel austempered or tempered after austempering treatment. The results obtained from the experiment are as follows ; (1) Optical micrograph has revealed that the transformation rate of bainite is delayed as the austenitizing temperature increases and that bainite is most apparently transformed at an austempering temperature of 290℃. (2) The amount of retained austenite during austempering has been analysed to be increased by the X-ray diffraction technique as the transformation product of bainite is increased. It has also been shown that the longer the holding time of austempering, the more the transformation quantity of bainite is formed, exhibiting, however, that the rate of bainitic transformation is considerably retarded after a certain period of holding time elapses. (3) Hardness measurement has shown that hardness values obtained after austempering increase with decreasing the amount of retained austenite. (4) The austempering and then tempering cycle has been formed to give hardness values which are more greatly improved as austenitizing temperature is increased. (5) The mechanical property of the specimen primary-tempered for 1 hour at 550℃ after austempering for 2 hours at 290℃ from the austenitizing temperature range of 1180℃ to 1210℃ have been estimated to be good values.
중탄소 Boron 강의 가스침질탄화처리에 의해 형성된 화합물층의 마모특성에 관한 연구
이상윤,이해우,조효석,이준범,박기원,오도원 한국열처리공학회 1999 熱處理工學會誌 Vol.12 No.2
The study on the wear characteristics of compound layers formed during gaseous nitrocarburising in the medium carbon boron steels and the plain carbon steel has been carried out by using a pin-on-disc type wear test machine under the oil lubricating condition at room temperature and by varying applied loads, sliding speeds and wear distances. Values of friction coefficient measured at the sliding speed of 0.4m/sec under the oil lubricating condition have been shown to decrease considerably with increasing applied load and become gradually a constant value as load is increased to a higher value, showing that the transition load for friction coefficient appears at an applied load of 247.2N. The length and volume wear rates of compound layer have been revealed to relatively constantly increase, also showing that the wear life per unit thickness of compound layer turns out to be superior as porous layer has a denser and thinner appearance. As the sliding speed increases during wear test performed by varying sliding speed at a load of 63.2N under the oil lubricating condition for medium carbon boron steel nitrocarburised in gas atmosphere, the wear rate has been found to increase, the friction coefficient to decrease and the wear life per unit thickness of compound layer to decrease considerably.