• Journal of Advanced Marine Engineering and Technology
• /
• v.21 no.2
• /
• pp.157-165
• /
• 1997

The strength level of welded joint in room temperature and elevated temperature up to $600^{\circ}C$ was investigated in 250 and 300 grade 18% Ni maraging steel sheet welded with electron beam. The results obtained in this study are as follows; 1. Optimum welding heat input was 600J/cm in 1.0mm thickness and the room temperature tensile strength, joint efficiency of welded joint treated with optimum aging condition were found to be about 166kg/$mm^2$, 95% in 250 grade, 189kg/$mm^2$, 92% in 300 grade maraging steel sheet, respectively. 2. Tensile strength of welded joint in room temperature increased slightly by aging after repeated solution heat treatment, but the fracture mode showed a shear. 3. Joint efficiency at a temperature between $540^{\circ}C$and $600^{\circ}C$ found to be about 72% to 55%, but the joint efficiency exceeded about 90% below $300^{\circ}C$. 4. The fracture occurred in most weld metal, and the fracture surface showed a shallow dimple.

• Journal of Aerospace System Engineering
• /
• v.8 no.2
• /
• pp.33-39
• /
• 2014

Feathering spindle is one of the critical parts of the rotor system in the Smart Unmanned Aerial Vehicle(SUAV) that it was manufactured with special material, Maraging C300. During the initial ground and tie-down flight tests of the SUAV, surface of the feathering spindle contacting to the needle-roller bearings showed excessive wear and dent due to high vibrating loads transferred from the rotating blades. Gas nitriding process was applied to the bearing contact surface of the feathering spindle to increase surface hardness so as to improve the surface defects. This paper briefly presents the gas nitriding process adopted and the spindle quality improvements including wear and corrosion resistance.

• Journal of the Korean Society for Heat Treatment
• /
• v.6 no.4
• /
• pp.185-193
• /
• 1993

The effect and Condition of heat treatment on the tensile strength of welded joint was investigated in 300 grade 18% Ni-Co-Mo-Ti maraging steel sheets welded with electron beam. A good tensile strength of welded joint was obtained by following heat treatment cycle ; At $1100^{\circ}C$ the specimen was high temperature solution treated for 1 hour and then it was repeated solution treated at $900^{\circ}C$, $820^{\circ}C$ for 1 hour respectively to recrystallize the coarsened ${\gamma}$ grain. These heat treatment cycle was completed by an final aging heat treatment at $480^{\circ}C$ for 4 hour. Moreover, dissolution of dendrite, a significant decrease in seregation of Mo, Ti in weld metal were observed and also the coarsened ${\gamma}$ grain formed at $1100^{\circ}C$, $1200^{\circ}C$ changed to fine grain due to the effect of recrystallization.