In this study, the effect of tempering on the stretch-flangeability is investigated in 980 MPa grade dual-phase steel consisting of ferrite and martensite phases. During tempering at 300 oC, the strength of ferrite increases due to the pinning of dislocations by carbon atoms released from martensite, while martensite is softened as a consequence of a reduction in its carbon super-saturation. This strength variation results in a considerable increase in yield strength of the steel, without loss of tensile strength. The hole expansion test shows that steel tempered for 20 min (T20 steel) exhibits a higher hole expansion ratio than that of steel without tempering (T0 steel). In T0 steel, severe plastic localization in ferrite causes easy pore formation at the ferrite-martensite interface and subsequent brittle crack propagation through the highly deformed ferrite area during hole expansion testing; this propagation is mainly attributed to the large difference in hardness between ferrite and martensite. When the difference in hardness is not so large (T20 steel), on the other hand, tempered martensite can be considerably deformed together with ferrite, thereby delaying pore formation and hindering crack propagation by crack blunting. Eventually, these different deformation and fracture behaviors contribute to the superior stretch-flangeability of T20 steel.

The resistance of metallic materials to ballistic penetration generally depends on a number of parameters related to projectile, impact, and armor plate. Recently, armor materials have been required to have various properties such as hardness, strength, and impact toughness in order to maintain an excellent ballistic resistance even after impact. In the present study, the influence of tempering on the microstructure and mechanical properties of an ARMOX 500T armor steel plate was investigated and then compared with those of S45C and SCM440 steels. As the tempering temperature increased, the hardness and strength gradually decreased, whereas the ductility and impact toughness clearly increased because the hardness, tensile, and impact properties were affected by the microstructural evolution and precipitation occurring during tempering. On the other hand, temper embrittlement appeared at tempering temperatures of 300 to 400 °C for the impact specimens tested at low temperature.

The present study deals with the effects of tempering treatment on the microstructure and mechanical properties of Cu-bearing high-strength steels. Three kinds of steel specimens with different levels of Cu content were fabricated by controlled rolling and accelerated cooling, ; some of these steel specimen were tempered at temperatures ranging from 350˚C to 650˚C for 30 min. Hardness, tensile, and Charpy impact tests were conducted in order to investigate the relationship of microstructure and mechanical properties. The hardness of the Cu-added specimens is much higher than that of Cu-free specimen, presumably due to the enhanced solid solution hardening and precipitation hardening, result from the formation of very-fine Cu precipitates. Tensile test results indicated that the yield strength increased and then slightly decreased, while the tensile strength gradually decreased with increasing tempering temperature. On the other hand, the energy absorbed at room and lower temperatures remarkably increased after tempering at 350˚C; and after this, the energy absorbed then did not change much. Suitable tempering treatment remarkably improved both the strength and the impact toughness. In the 1.5 Cu steel specimen tempered at 550˚C, the yield strength reached 1.2 GPa and the absorbed energy at -20˚C showed a level above 200 J, which was the best combination of high strength and good toughness.

The effect of tempering temperature and microstructure on dry sliding wear behavior of quenched and tempered PM with 0.3% graphite and 1-2% Ni steels was investigated. The sintered specimens were quenched from 890℃ and then tempered at 200℃ and 600℃ for 1 hr. Wear tests were carried out on the quenched＋tempered specimens under dry sliding wear conditions using a pin-on-disk type machine at constant load and speed. The experimental results showed that the wear coefficient effectively increased with increasing tempering temperature and decreased with increasing Ni content.

The study examines hardness pattern of SH737-2Cu-.9C samples transient liquid phase sintered at different temperatures viz. , and , heat treated by various methods and then tempered at different temperatures. Sintered samples were characterized for density and densification parameter, and austenitized at , subsequently cooled by four different methods viz. annealing, normalizing, oil and brine quenching. Hardness pattern was found minimum for air cooled and maximum for brine quenched, and samples sintered at had relatively higher hardness. The O.Q and B.Q samples were then tempered at , , and . Hardness pattern typically showed secondary hardness taking place, with maximum around .

쌀을 수분함량 24%로 10시간 동안 조질한 후 roll mill로 1회 분쇄한 후 pin mill로 1회 분쇄하였을 때 의 특성을 조사하였다. 소요전력은 다른 제분방법(TRMR, WDRMR, DPMR) 보다 가장 적었다. 쌀가루의 수분함량은 수침하여 제분한 쌀가루의 32.8%, 조질하여 제분한 쌀가루의 22.3%보다 훨씬 적은 17.2%였다. 쌀가루의 입도는 100 mesh 이상의 입자가 87.4%로 수침 roll mill 쌀가루 6.8%와 조

Power consumption, mesh size, moisture content, color difference, amylogram of rice flour milled with the water soaked rice were compared with that of rice using dry pin mill process. The rice was soaked in 23, 24, 25, 26% of water for 10hr, independently. The more rice had moisture content, the less power consumption was needed. Power consumption to mill the rice soaked in 25% of water was less than that of dry rice by 6.8kW/100Kg. Moisture content of rice flour from the rice soaked with 25% of water was 2% higher than that of rice flour from the rice soaked with 23% of, water. Population of flour particle from the rice soaked with 24-25% of water was 45.7∼46.25 of 60 mesh, 9.7∼10.4% of 80∼100 mesh and 7.7∼8.1% of 100 mesh. Gelatinization temperature of rice flour from the rice soaked with 23% and 24∼25% of water was 65.70C and 64.50C, independently. Temperature of rice flour from the rice soaked with 23% 24∼25% of water sith minimum viscosity was 85.50C and 88.4∼88.70C, independently. Brightness and whiteness of the rice flour from the rice soaked with 24∼25% of water were 95.90∼95.95 and 905.82∼95.94, independently. Brightness and whiteness of the rice flour from the soaked rice were 1.2 and 1.7 higher than that of rice flour from the dry rice, independently.